Seeing Motion: A History of Visual Perception in Art and Science 9783110422993, 9783110426960

Table of contents :
TABLE OF CONTENTS
PREFACE: On Theories and Art in Visualizing (Apparent)-Motion
Acknowledgements
PART 1: On the Study of Apparent Motion, Apparent Corporeality and Apparent Spatiality
Seeing as a Scientific Topic
The Beginnings of the Study of Apparent Motion
An Individual Way of Seeing: Jan Evangelista Purkinje
The Explanation of an Optical Illusion: Peter Mark Roget
The First Motion Picture Machine: Joseph Plateau
The Phenakistoscope or the Stroboscopic Disk
Inventions with Stroboscopic Effects
The Talbot-Plateau law of 1834/35
Gustav Theodor Fechner’s Subjective colors
Four notes on Afterimages
Experiments on the Simulation of Riparian Illusion with the oppel Antirheoscope
Zöllner’s Illusion
Reflections on Zöllner’s Illusion: Wilhelm Filehne
hermann helmholtz and the new Physiological optics in the nineteenth century
helmholtz’s Experiments on Visual Sensations
Ernst Brücke: The Advantage of Intermittent Retina Stimuli
Josef czermak: Thoughts on Speed during Motional Illusions
The Influence of Psychophysics on Mach’s Experiments
Mach’s Series of Experiments on light Stimulus on the Retina
Mach’s Experiments on Sensation of Movement and Afterimages of Movement
Studies in Movement: The Mach Drum
Sigmund Exner: Explorations into Kinesthetics, Sensation of Movement and Apparent Motion
Two Sparks and One Apparent Motion
Johann Ignaz Hoppe’s Attempts at Defining Apparent Motion
The First Psychological Analyses of Stroboscopic Phenomena (1886)
James McKeen Cattell: Visual Stimulation in Time
The First Monograph on the Perception of Movement
Alfred Borschke and Leo Hescheles: Movement Afterimages and Speed of Movement
Adolf Szily’s Experimental Analysis: Moving Afterimage and Contrasts of Movement
Szily’s Instrument Based Observations
Adolf Basler: Memoranda on the Process of Movements of Afterimages
Vittorio Benussi: From Apparent Motion to Apparent Corporeality
Stroboscopic Apparent Motion (S-Movement), 1912
Combinations of Apparent Motion (1918)
Stereo Kinetics
Max Wertheimer: The Berlin Gestalt Psychology
Wertheimer’s Phi-Phenomena (1910–1912)
From Apparent Motion to a Repositioning of Psychology as a Whole
Application of a Theory for Types of Visual Perception
Karl Duncker: On Induced Movements
Herbert Kleint: Simulation of a Tilted Room
The Inverted Image of the Retina
George M. Stratton and the Experiment with Inversion Goggles
Early Experimental Perception Research at the Innsbruck University: Franz Hillebrand, Theodor Erismann, Ivo Kohler
Theodor Erismann and Ivo Kohler’s Goggle Experiment
Consecutive Experiments with Inversion Goggles after 1955
Resume of Part I
PART 2: From the Artistic Transformation to Immateriality
The Beginnings of Kinetic Art at the Turn of the Twentieth century
From Schumann/Wertheimer Wheel-Tachistoscope to Duchamp’s Readymade Roue de bicyclette (Bicycle Wheel)
Influence of Perception Research on Art after 1960
Artistic Research: Alfons Schilling, Jeffrey Shaw, Peter Weibel
Discerning Participatory capacity and Phenomenological narration: Jeffrey Shaw
Addiction to new Images: Alfons Schilling
From Perception Devices to Seeing Machines
Visual Test Situations between Experiment and Theory: Peter Weibel
The observation of observation in Peter Weibel’s Work
construction of Imaginary Spaces and observations in Apparent Spaces
Interactive Images and Dislocation
Interactive Plasticity in the Virtual Image
Feedback-Effects
EPILOG
APPENDIX
Endnotes
References
Internet sources
Image credits

Citation preview

Seeing Motion

Edition Angewandte Book Series of the University of Applied Arts Vienna

Edited by Gerald Bast, Rector

RoMAnA KARlA SchUlER

SEEING MOTION A HISTORY OF VISUAL PERCEPTION IN ART AND SCIENCE

Seeing Motion Romana Karla Schuler, Department of Digital Arts, University of Applied Arts Vienna, Austria library of congress cataloging-in-Publication data A cIP catalog record for this book has been applied for at the library of congress. Bibliographic information published by the German national library The German national library lists this publication in the Deutsche nationalbibliografie; detailed bibliographic data are available on the Internet at http://dnb.dnb.de. This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, re-use of illustrations, recitation, broadcasting, reproduction on microfilms or in other ways, and storage in databases. For any kind of use, permission of the copyright owner must be obtained. © 2016 Walter de Gruyter Gmbh, Berlin/Boston Translation from German into English: Gretchen Sylvia Simms copy editing: Elisabeth Schicketanz, Michael Walch coverimage: Marcel Duchamp, Rotorelief, 1935 © Succession Marcel Duchamp/Bildrecht, Wien, 2015 layout: Rainer Dempf Printing: Remaprint littera, Wien Printed on acid-free paper produced from chlorine-free pulp. TcF Printed in Austria ISSn 1866-248X ISBn 978-3-11-042696-0 This publication is also available as an e-book (ISBn PDF 978-3-11-042299-3; ISBn EPUB 978-3-11-042303-7). www.degruyter.com

TA B l E o F c o n T E n T S

P R E FA c E On Theories and Art in Visualizing (Apparent)-Motion . . . . . . . . . . . . . . . . . . . . . . . . . 9

Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

PA RT 1 On the Study of Apparent Motion, Apparent Corporeality and Apparent Spatiality

Seeing as a Scientific Topic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 The Beginnings of the Study of Apparent Motion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 An Individual Way of Seeing: Jan Evangelista Purkinje . . . . . . . . . . . . . . . . . . . . . . . 24 The Explanation of an Optical Illusion: Peter Mark Roget . . . . . . . . . . . . . . . . . . . . . 31 The First Motion Picture Machine : Joseph Plateau . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 The Phenakistoscope or the Stroboscopic Disk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 Inventions with Stroboscopic Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 The Talbot-Plateau law of 1834/35 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 Gustav Theodor Fechner’s Subjective colors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 Four notes on Afterimages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 Experiments on the Simulation of Riparian Illusion with the oppel Antirheoscope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 Zöllner’s Illusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 Reflections on Zöllner’s Illusion: Wilhelm Filehne . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 hermann helmholtz and the new Physiological optics in the nineteenth century . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 helmholtz’s Experiments on Visual Sensations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 Ernst Brücke: The Advantage of Intermittent Retina Stimuli . . . . . . . . . . . . . . . . 64 Josef czermak: Thoughts on Speed during Motional Illusions . . . . . . . . . . . . . . . 67 The Influence of Psychophysics on Mach’s Experiments . . . . . . . . . . . . . . . . . . . . . 68 Mach’s Series of Experiments on light Stimulus on the Retina . . . . . . . . . . . . . . 71

Mach’s Experiments on Sensation of Movement and Afterimages of Movement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 Studies in Movement: The Mach Drum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 Sigmund Exner: Explorations into Kinesthetics, Sensation of Movement and Apparent Motion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 Two Sparks and One Apparent Motion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 Johann Ignaz Hoppe’s Attempts at Defining Apparent Motion . . . . . . . . . . . . . . . 97 The First Psychological Analyses of Stroboscopic Phenomena (1886) . . . . . . . 99 James McKeen Cattell: Visual Stimulation in Time . . . . . . . . . . . . . . . . . . . . . . . . . . 101 The First Monograph on the Perception of Movement . . . . . . . . . . . . . . . . . . . . . . 103 Alfred Borschke and Leo Hescheles: Movement Afterimages and Speed of Movement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106 Adolf Szily’s Experimental Analysis: Moving Afterimage and Contrasts of Movement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108 Szily’s Instrument Based Observations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110 Adolf Basler: Memoranda on the Process of Movements of Afterimages . . . . 113 Vittorio Benussi: From Apparent Motion to Apparent Corporeality . . . . . . . . 115 Stroboscopic Apparent Motion (S-Movement), 1912 . . . . . . . . . . . . . . . . . . . . . . . . 118 Combinations of Apparent Motion (1918) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122 Stereo Kinetics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126 Max Wertheimer: The Berlin Gestalt Psychology . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130 Wertheimer’s Phi-Phenomena (1910–1912) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132 From Apparent Motion to a Repositioning of Psychology as a Whole . . . . . . . 140 Application of a Theory for Types of Visual Perception . . . . . . . . . . . . . . . . . . . . . 141 Karl Duncker: On Induced Movements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143 Herbert Kleint: Simulation of a Tilted Room . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146 The Inverted Image of the Retina . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150 George M. Stratton and the Experiment with Inversion Goggles . . . . . . . . . . . . 152 Early Experimental Perception Research at the Innsbruck University: Franz Hillebrand, Theodor Erismann, Ivo Kohler . . . . . . . . . . . . . . . . . . . . . . . 157 Theodor Erismann and Ivo Kohler’s Goggle Experiment . . . . . . . . . . . . . . . . . . . . 159 Consecutive Experiments with Inversion Goggles after 1955 . . . . . . . . . . . . . . . 165 Resume of Part I . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169

PA RT 2 From the Artistic Transformation to Immateriality

The Beginnings of Kinetic Art at the Turn of the Twentieth century . . . . . . . 174 From Schumann/Wertheimer Wheel-Tachistoscope to Duchamp’s Readymade Roue de bicyclette (Bicycle Wheel) . . . . . . . . . . . . . 176 Influence of Perception Research on Art after 1960 . . . . . . . . . . . . . . . . . . . . . . . . . 183 Artistic Research: Alfons Schilling, Jeffrey Shaw, Peter Weibel . . . . . . . . . . . . . 185 Discerning Participatory capacity and Phenomenological narration: Jeffrey Shaw . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186 Addiction to new Images: Alfons Schilling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208 From Perception Devices to Seeing Machines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215 Visual Test Situations between Experiment and Theory: Peter Weibel . . . . . 225 The observation of observation in Peter Weibel’s Work . . . . . . . . . . . . . . . . . . . . 237 construction of Imaginary Spaces and observations in Apparent Spaces . . . 244 Interactive Images and Dislocation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256 Interactive Plasticity in the Virtual Image . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260 Feedback-Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 268

EPIloG by Peter Weibel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273

APPEnDIX Endnotes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 291 Internet sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 302 Image credits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 303

P R E FA c E On Theories and Art in Visualizing (Apparent)-Motion

This book examines the historical theories of the perception of apparent motion from the epistemology of scientific experimentation and the impact of these studies on sensory-motoric perception in virtual art. The nineteenth century is often described retrospectively as the century during which movement and speed were discovered. These newly developed methods of actually showing the sequence of motion aroused the interest of science in the area of perception of moving lines and bodies. The historical background can be traced to Stone Age cave paintings or even to Egyptian burial paintings – the earliest efforts in depicting motion sequences. At the turn of the nineteenth century the first scientific studies were conducted on the perception of the process of movement and the three-dimensionality of objects: a stroboscopic disk (1832/33) and a stereoscope (1838) were the first devices that could synthesize apparent motion and apparent corporeality. These groundbreaking experiments led directly to the realization of today’s ubiquitous technological feasibility such as the use of cyberspace. Among artists, the advanced protagonists for this have always used innovative achievements and discoveries in the fields of physics, mathematics or technology on topics such as light and perspective for their pictorial depictions, and it is proven that they employed so-called visual devices. This search for new insights begins with the question: What should be researched? This question already implies that – metaphorically speaking – researchers and artists found themselves in an “unfocused” area, which lay beyond their secure comfort zone. new ideas and beliefs had already been added to the research process, or altogether new topics arose such as the epistemology of perception that enabled the visualization of apparent motion: the goal was to explain the deception, the delusion of sight, in an attempt to subsequently avoid such deceptions, or at least to analyze the apparent and to ultimately distinctly isolate it from reality. What happened? The discovery that apparent perceptions, physiological ones such as the afterimage (Roget) or those that even occurred in nature such as J. oppel’s riparian illusion, could also be artificially generated, unleashed a host of experiments during the nineteenth century. The new

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insights on the unreliability of visual perception, on the difficulty of distinguishing between reality and virtuality first caused certain uneasiness. How could one ever trust one’s own senses anymore? This unreliability of one’s own sense perception prompted new questions in the physiological and specifically in the neurological sciences. Subsequently, heated discussions ensued on the topic far beyond the areas of empirical sciences that always included the self and self-observation and therefore also cultural, sociological and philosophical questions. The interpretation of reality between actual movement and apparent motion had to be fundamentally reconsidered. Ultimately, the studies of optical illusions and the development of the stroboscope and stereoscope heralded the advent of a profound cultural change. In the span of a mere one hundred years, man’s viewing habits – such as seeing kinetic lines, forms and objects or spaces – our conception of illusion and that which is real has been revolutionized by means of modern perception research and the development of new technological media imagery. The result of the next step that led into completely illusionary worlds will soon be available in every home with new immersion technology. Our seeing habits, increasingly focused on visual display units, have radically altered our reality. This constructed virtuality can be considered as an expanded reality. The acceptance of apparent worlds, of virtuality, in our world could possibly be the greatest cultural change in the twentieth century. Artists have long seized on and implemented virtual phenomena. An impressive example is that of the Belgian artist René Magritte and his surrealist paintings. Beginning with film and photography, media art offers a multitude of possibilities in the creation of artificial, apparent worlds. Since the 1960s artists have experimented with new media and created visionary concepts. With so-called expanded cinema, the medium of film has been analyzed in a de- and re-constructed manner. As soon as digital technologies were made accessible, new digital aesthetics in art emerged, and with their surreal narrative imagery landscapes a broad spectrum of opportunities evolved in addressing multi-sensory perception. Supported by new technology, the potential of new image worlds could finally be documented and critiqued from the position of the integrated observer. Exemplary works to be mentioned here are Jeffrey Shaw’s The Golden Calf (1994) or Peter Weibel’s Europa(t)raum (1983) and Gesänge des Pluriversums (Songs of the Plural Universe, 1986–88).

This publication is divided into two major parts. The first section outlines the epistemology of apparent motion. In order to make the marked research of the phenomena of apparent corporeality and apparent motion more accessible, I found it necessary to pinpoint and summarize the primary sources of study in this field of the nineteenth and twentieth century. Subsequently, while relying on the historical theories of visual perception research, the second section attempts to provide an exemplary account of the historical origins of modern virtual art from the twentieth century and into the twenty-first century based on three marked artists – Alfons Schilling, Jeffrey Shaw and Peter Weibel. At the center are manifestations of those perceptions – that aided by apparative vision in experimental psychology or physiology and – reflecting these scientific discoveries are generatedin experimental apparative and electronic art. A historical line can be drawn – based on the great number of works selected – between the theories of experiential perception research (hermann helmholtz, Ernst Mach, Sigmund Exner, Wilhelm Stern, Vittorio Benussi, Max Wertheim, George M. Stratton, Ivo Kohler) and modern apparative art (Alfons Schilling) as well as electronic digital art (Jeffrey Shaw, Peter Weibel). The influence of early physiological perception research is clarified in the artistic experiments addressing apparent corporeality or apparent bodies. Since the onset of the 1920s, artists such as Marcel Duchamp, naum Gabo and lászló Moholy-nagy have grappled with apparent contours, apparent lines and apparent movements. By doing so, kinetic art and opArt, with proponents such as nicolas Schöffer, Victor Vasarely, Frank Malina, Joel Stein, Getulio Alvarez or Marina Apollonio or also Alfons Schilling with his kinetic painting, evolved in the midst of the twentieth century. With the spread of cybernetic and reorientation toward the principle of the interdisciplinary, a transition occurred in the artistic self-image. Step by step, the artists’ interests moved in the direction of science – an approach that was initially met with a lack of understanding. In the 1960s the search for an interconnection of art and science was already seen as a potential enrichment of both systems. In his 1970s book Expansion der Kunst, the artist Jürgen claus spoke out clearly in favor of a corresponding system of art. It was “the intellectual audacity that understands the

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universality of art […] that promotes the correspondence of art with other advanced fields of knowledge.” only in the past few years has a convergence between science and art also begun to manifest in the traditional institutions such as the art academies. Models are being sought out in order to structurally integrate an open complementary dialogue between science and art. The purpose of this book is to make the influences of scientific insights in the field of human perception on art, the influence of the nineteenth century application of perception research on illusion, kinetic apparent characters and apparent motion on the machine, kinetic or computer supported visual art of the twentieth and twenty first centuries more accessible.

Acknowledgements

My constant and longtime interest in visual perception was ultimately a reason for my focus on fine arts. The art historical deliberations of John Berger, Michael Baxandall, Svetlana Alpers, Rudolf Arnheim and Ernst Gombrich furthered my interest for perception during my studies in Innsbruck. It was logical that the topic of my doctoral dissertation would be about the field of visual perception. After the monograph on the artist and philosopher Peter Weibel, Bildwelten (1996), was published, he was the one who guided me to look more closely at the Innsbruck goggle experiments. Brimming with enthusiasm for the subject, I submitted my dissertation application to the media researcher Manfred Faßler at the University of Applied Arts Vienna. The initial enthusiasm for the project was challenging because of the demands of my work as curator at Viennese museums. looking back, the stretch of time the research entailed actually enriched and enhanced my work. only through the selection of historical material it became clear to me where my work would lead me. The linear content, placing the focus on visual perception of apparent motion and apparent spatiality, essentially prevailed, and yet fundamental changes were made in terms of expanding on the research that incorporated nineteenth century experiments of seeing apparent motion. The Innsbruck goggle experiments still occupy an important position in this publication. however, they are not, as originally planned, developed in isolation. Instead, they are embedded in the history of knowledge on apparent spatiality and continue through to the development of digital art. My research was completed in 2011 and submitted as a dissertation. It is a special honor and pleasure that this German manuscript has been translated into English and that it is appearing as an edition of the University of Applied Arts Vienna. I would like to, especially, thank Gerald Bast, the president of the University of Applied Arts Vienna, who enabled it all. In this regard, I would also like to thank Anja Seipenbusch-hufschmied of the publication department at the University of Applied Arts Vienna, as well as Angela Fössl from the publishing house Walter de Gruyter. In the course of my research and while drafting of this publication, I was afforded support and encouragement from many different people. I

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would primarily like to thank Peter Weibel, who always stood by my side and continuously supported me throughout with his interest in and comments on the subject matter. Jeffrey Shaw receives my sincere thanks for his generous provision of the many images of his works. A special thanks goes to Alfons Schilling (1934–2013) for the countless and highly inspiring conversations on his artistic ideas and works at the onset of my research. I would also like to thank my friend and translator Gretchen Sylvia Simms, who found it exciting to delve into the history of knowledge alongside the history of art. My sincere thanks to my friends, colleagues and co-workers from various universities: Elisabeth von Samsonow, my academic advisor at the Academy of Fine Arts, Vienna, who was always at my side motivating me; Inés Ratz from the office of Alfons Schilling’s estate, Vienna, for the images from the estate; Dietmar Kratzer and Gerhard lücke from the Psychology Institute at the University of Innsbruck; Armin Stock from the AdolfWürth-center for the history of Psychology, Würzburg; Brigitte Parakenings from the philosophical archive at the University of constance; Mauro Antonelli from the psychology archive at the University of Milan; Ruth Schnell from the Department of Digital Arts at the University of Applied Arts Vienna, as well as the co-workers at the library at the Academy of Sciences, Vienna. For the continuous and wonderful working support for the necessary digital devices afforded by my brother clemens Schuler – thank you very much. My thanks go to Rainer Dempf for the graphic design. A very special, heartfelt thanks goes to my reader Elisabeth Schicketanz, who always gave me the opportunity to clarify my thoughts by the objections she raised. And thanks also to Dorothea May for her spiritual guidance considerations aimed at that which is essential. lifelong confidence in me and loving affection came from my parents, Sophie and Willi Schuler. They are the reason that this publication is also dedicated to them.

PA RT 1 On the Study of Apparent Motion, Apparent Corporeality and Apparent Spatiality Seeing as a Scientific Topic

The visual arts have always been considered an essential and specific tool for the theory of visual perception. Those who create works of art considered technical-optical achievements (i.e. perspective) or a device such as the camera obscura, for example, as a support for creating naturalistic, imaginative and narrative depictions. The great masters leonardo da Vinci and Albrecht Dürer recognized the necessity of working with the laws of light and perception in addition to their primary focus of painting (fig. 1, 2, 3). however, at the turn of the nineteenth century profound changes occurred. According to the art historian Jonathan crary’s 1 hypothesis, a new way of observing evolved that differed significantly from that of the seventeenth and eighteenth centuries.2/* For René Descartes the eye was still considered to be a sort of seeing machine with which to regard the outside world. here Descartes fell back on Kepler’s optical model, which considered the eye to be a form of camera obscura (fig. 4, 5). The act of seeing was interpreted as something mechanical. The metaphor of the machine for the eye corresponded to the spirit of the seventeenth century and the mechanistic world picture. It also broke down the human body into individual parts in order to potentially reassemble it and its functions again. It was not until the eighteenth century that scientists came to the conclusion that within the act of seeing electrical impulses entered the nervous system. At the turn of the nineteenth century the physicalmechanical theory of seeing was questioned. The new physiological issues made it possible to explain the emergence of visual illusions, which had previously just been vexing.3 crary admits that he was unable to establish empirically the type of viewer existing in the nineteenth century. What he believes could explain the socio-cultural changes were the numerous inventions of optical devices such as the stereoscope or the phenakistoscope (fig. 6, 7). The topic of seeing was quickly discovered as subject matter in the scientific disci-

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* The invention of the camera obscura had an impact on science, philosophy and art and ultimately changed the general type of observer in the seventeenth and eighteenth centuries.

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plines of physics, physiology and psychology. The discrepancy between science and art went from working together in the spirit of cooperation and a simultaneous goal of autonomy to a final break between the two disciplines. While Romantic painting was reduced to aesthetic appearance and disinterestedness (Kant), the nineteenth century was celebrated as the Age of natural Sciences. The renowned naturalist Emil du BoisReymond made a polemic attack on the current situation in the arts in an address on “natural sciences and art” given at the Academy of Sciences in Berlin in 1890. According to him, art “failed to make the connection with the modern age of science and technology”.4 Many natural scientists shared du Bois-Reymond’s hard-hitting opinion on the subject of the antiquated status of art. natural scientists who created a revolution with their new theories of vision in the nineteenth century, such as hermann helmholtz, Ernst Mach or the Viennese Sigmund Exner, considered painting to be a significant field of study. hermann helmholtz, who was the inventor of the ophthalmoscope and the first physiologist and physicist to successfully measure the speed at which nerve impulses are conducted, published his famous Handbook of Physiological Optics in 1867.5 here he presented his theory that the brain interprets the signals sent by the sensory organs via neural pathways: “The sensory perceptions are signs for our consciousness in which understanding the meaning is left to our mind.”6 Almost simultaneously, helmholtz gave his classes The New Developments in Visual Theory in heidelberg and Frankfurt/Main. In 1868 they were published in his series titled Popular Lectures on Scientific Subjects. At the beginning of the first chapter – on the optical working of the eye – he explains that the teachings about the senses represents a frontier and maintained that the natural sciences and humanities could only arrive at optimal solutions by working cooperatively.7 For helmholtz, physiology of the senses could not be ascribed to the vital biology of nativism but rather it was based on pure physical biology. With his consistent approach he solved the sophomoric squabble between empiricists and nativists in 1866, an argument which would continue into the twentieth century. helmholtz compared the eye to a camera or nerves with telegraph wires. These analogies between biology and technology spelled out helmholtz’s empirical-physical concepts. In addition to helmholtz, it was Emil du Bois-Reymond and Ernst Brücke who were included among the notable representatives of a physical biology. From 1847 on, the young physiologists called themselves the organic

Fig. 1 Studies on perspectives: Albrecht Dürer, 1525 (above); Athanasius Kirchner, 1646 (below).

Fig. 2 Camera Obscura as a table-top device

Fig. 3 Leonardo da Vinci: Computation of light beams in glass, Codex Atlanticus, 1508

Fig. 4 René Descartes’ model of sight, 1637

Fig. 5 Receptacles and retinas, models of eyes according to Kepler

Fig. 6 Phenakistoscope (Plateau)

Fig. 7 Stereoscope

physicists 8. All of them were students of the vitalist Johannes Müller, who published the much-noted two-volume edition of Handbuch der Physiologie des Menschen (handbook on the Physiology of Mankind). Ewald hering and Ernst Mach were also especially critical of this interpretation of perception as being purely empirical phenomena. They were convinced that the laws of physics were in themselves insufficient to explain physiological sensory perceptions. Instead, a link would have to be assumed between psychological and physiological events. In his writing on optics, helmholtz also delved into the subject of painting. In addition to color theory, he was interested in the effects of depth as well as the relation of size on a two dimensional surface.9 It would seem possible that his preoccupation with depth perception led to the development of the telestereoscope. It enabled viewing the world through the eyes of a giant – everything that was off in the distance would draw closer and would appear optically much smaller 10 (fig. 8). helmoltz’s descriptions and suggestions on using the photographic stereoscope were significant. he also considered their use relevant for art. helmholtz was one of the first to address retinal inversion with the use of prisms.11 The physicist Ernst Mach attempted to explain artistic issues with illustrative models from the field of perception in his famous 1886 lecture titled Why has Man two Eyes? According to Mach, the specific location of the human eyes is directly relevant for how we view the world and its culture. Mach worked on experiments with endoscopes in order to expand the range of vision through which our “two windows”, the eyes, see and thus to vary it.12 Mach’s 1885 bestselling publication Die Analyse der Empfindungen (The Analysis of Sensations) would have a cultural influence at the end of the nineteenth century and beyond. Mach, like Freud, was convinced that the ego doesn’t have any distinct contours: the ego was more of a fictional reality. That which is real and that which is an illusion are not always clearly separable. Many writers and artists who were active around 1900 recognized a philosophically based explanation for Impressionism and the unsalvageable ego.* The Viennese physiologist Sigmund Exner, was one of helmholtz’s students. Exner is considered to be the actual scientific discoverer of apparent motion. Using two electric sparks that he set off for a moment sequentially in 1875, he was able to prove the phenomenon, which until then had only been vaguely circumscribed.13

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* The Viennese writer Hermann Bahr published his essay “Das unrettbare Ich” in 1904. In it he refers to Mach’s theory on truth and illusion. Hermann Bahr: “Das unrettbare Ich” in Dialog vom Tragischen (Berlin, 1904), 79–101.

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* Today this is the MAK, Museum for Applied Arts, Vienna.

** The expression “Aufbau der Sehwelt” (World of Seeing) stems from the perceptual psychologist Wolfgang Metzger. Gesetze des Sehens. Die Lehre vom Sehen der Formen und Dinge des Raumes und der Bewegung, reprint after the 3rd edition, reworked edition 1975, (Eschbom, 2008). In the foreword of the third edition Metzger writes: “The book (…) could have also been titled: The Structure of the World of Seeing. And the terms such as ‘right seeing’ could have also been used here.” Heinrich Kottenhoff, Was ist richtiges Sehen mit Umkehrbrillen und in welchem Sinn stellt sich das Sehen um?, (Meisenheim am Glan, 1961).

In his noted lecture at the Viennese Museum for Art and Industry* in 1882 Zur Physiologie des Fliegens und Schwebens in den bildenden Künsten (on the physiology of flying and floating in the visual arts), Exner tried to clarify an established theme in painting from an empirical point of view. Using flying entities, he demonstrated the impossibility of portraying angels. Exner hoped artists would take note of scientific discoveries and would henceforth paint angels in a physical and physiologically correct manner. According to Exner, the ideal painter was “ … a man who followed science consistently and consciously.”14 natural scientists such as helmholtz, Mach or Exner recognized the relevancy and useful nature of physical, physiological and psychological insights in considering and evaluating images. In addition to the vast fundamental research conducted on the structure of the so-called Sehwelt **– pioneer work in the cognitive sciences – they anticipated a modern and very empirically positivistic orientated imagery prior to 1900. By the turn of the nineteenth century, a relevant framework for the new visual theories had been created. Particularly interesting for the natural scientists of that time was the retina, and how a light ray or light spot would penetrate the eye. The recognition of the chromaticity of objects, seeing movement and depth perception, for example, would become core issues in the visual perceptive sciences that the nineteenth century scientists would address and contend with.

Fig. 8 Helmholtz sketch of a telestereoscope

The Beginnings of the Study of Apparent Motion

There are several options available in terms of dating the first scientific studies on apparent motion: at the end of the eighteenth and the beginning of the nineteenth century, there are verifiable studies on apparent motion in an increasing number of scientific papers. This phenomenon became increasingly focal, especially in the medical field: the symptom of vertigo when occurring with rapid movements of the head or body leading to the first studies of natural apparent motion. As early as 1730, William Porterfield already discovered a physical connection between optical apparent motion and the human feeling of vertigo.15 The physician and philosopher Marcus herz published his first book on the subject of dizziness (vertigo) Trial on Vertigo in 1786 in Berlin. here he described that the altered perception of space resulting from rotating of persons around a stationary object in turn caused apparent motion.16 In 1792, the Scottish scientist and physician William charles Wells presented his studies on vertigo in connection with afterimage- and eye-movement.17 The scientific aspirations in medicine to determine the exact cause of vertigo; the attempt to observe the phenomenon of apparent motion for the first time in the empiric manner of the Age of the Enlightenment can be considered a possible cause for the upcoming interest in the development of moving pictures. The new scientific opinion in the field of optics in the early nineteenth century caused noticeable changes. Up until this time, scientists proceeded from geometrical optics or even ray optics and had studied and analyzed optical appearances from this standpoint. The wavelike diffusion of light was not known until the nineteenth century. With the discovery of the new Wave Theory, the classical perspective introduced during the Renaissance faded into the background. new directions in art presented themselves such as Impressionism or Pointillism that refrained from using a radial pictorial structure based on perspective. The assumption of physiological optics regarding vision became increasingly important.18 With his writings, the multi-faceted scientist Thomas Young is considered to have conceived the Wave Theory and physiologi-

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* The first volume was published in 1833.

** The field of experimental psychology was easily accessible for women. At the University of Innsbruck the first woman able to complete her studies with a doctoral degree had studied at the Institute of Psychology.

*** For the Poggendorff illusion a slanted (diagonal) line is broken by a beam. The slanted line appears to be offcenter – part of it seems to be farther down and the other part farther up.

cal optics. Johannes Müller’s Handbook on the Physiology of Mankind* had a noticeable impact on many young scientists, among them hermann helmholtz and Ernst Brücke. here, for the first time, was a comprehensive overview of the new physiological discoveries. In painting it was especially the plein air painters such as William Turner or the Impressionists like George Seurat who focused on the changing scientific tenets that occurred due to the Wave Theory and the interest in physiological optics. The ontological dominance of light was increasingly criticized in the course of the nineteenth century. once again, the individualistic-physiological way of thinking in the new directions of art found its way into the research of optics. The scope of experimental psychology had not been defined more closely before that time; physicists, chemists or physicians conducted most of the optical experiments. The natural scientists who studied material optics on a broad, universal scale were at an advantage because they could use transdisciplinary models. It was not until the beginning of the twentieth century that both male and female scientists could participate in wide-scale specialization.** Parallel to the study of optical-pictorial depictions, interesting enquiries were made in the field of electrical engineering and how electronic images might be created. Working instructions as to how to produce electrical dust images had been available as of 1803. In his treatise Ueber elektrische Figuren und Bilder (on Electrical Representations and Images) in the Annalen der Physik und Chemie, Peter Rieß clarified in 1846 that “among all of the electric images, electric dust depictions are the simplest to create, and explaining how is not difficult”19. The editor of this work was the well-known physicist and discoverer of the Poggendorff illusion***, Johann christian Poggendorff. In his writings Rieß describes very specifically the electrical Hauchbilder (breath-images)20 that had been produced by Gustav Karsten in 1843, and which could be found in the three-volume treatise, also in the Poggendorff Annals, volumes 57, 58 and 60. Rieß’s statement outlined clearly how surprisingly advanced the theories had been. And just as with practical versions of the first electric video engineering in the first half of the nineteenth century, these could be created using simple methods. The first electric depictions were categorized: electric dust figures, electric dust pictures, breath-images, fake breath-images, electrolyte pictures

or primary/secondary electric drawings. The principle was very similar everywhere: by setting up an electric field on a prepared surface (pitched copper for example) and working with the applied dust particles or with a pattern (signet or seal stamp), colored shapes appeared. In order to create dust figures for example, the plate was subjected to electrical current before the dust was applied. If the plate was dusted prior to electrification, the reverse shape was created. For the experiments with dust pictures simple patterns (models) were used. Rieß preferred using stamps with the letter T or F with a circle around them. The number of revolutions of the electric plate determined the intensity of the color. Rieß noticed that at 30 to 40 transmissions, the letter and the ring were red in color while, where the letter was not raised, it appeared to be yellow.21 The electric breath picture “is created by repeated electric charges that occur between the pattern and the isolated plate in alternating and opposite directions”22, explained the experimenter Rieß. he had tried out numerous variations of the electrical exchange. he had also experimented with paper that had been saturated with liquid beforehand and had been corroded chemically with the electrical fields creating color changes on the paper. A series of interchanging, alternating and opposing electrical charges were conducted that were then visible on the paper. These pictorial images became known as electrolytic pictures in physics.23

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* In more recent publications the name appears in the Czech manner of spelling Purkyně. I have kept the old, Germanized version because this is how it is mostly spelled in the nineteenth century source material.

** It is at this same institute that Johannes Czermak will work as an assistant. His observations on timing in 1857 influenced the physiologist Sigmund Exner in his theory on apparent motion (1875).

*** The Association was disbanded in 1972 and founded again in 1990

**** In “Das Sehen in subjektiver Hinsicht” (Seeing in a subjective manner, 1819), 893–904, Goethe discusses Purkinjes observations directly.

An Individual Way of Seeing: Jan Evangelista Purkinje*

And it does not suffice to achieve general terminology by means of superficial studies and careless observation. With each and every individual the characteristic attributes must be noted down to the most minute detail, and then provide an expert assessment of it. – Since however the individual person happens to be a most determined being, his knowledge requires a keener eye than is needed for more general scientific tasks.24 Purkinje (1823)

The brilliant natural scientist Jan Purkinje, born in Bohemia, enjoyed exceptional observation skills specifically suited for scientific phenomena. These allowed him to develop new and relevant bases on visual theory. Achievements of this multi-faceted and dedicated scientist, in his functions as a physician and physiologist and politics, are still effective to this day. on the university level, one of his major achievements was the foundation and management of the Physiological Institute in Breslau (1839) and Prague (1851)** Beyond that, he was also a founding member of the recognized Prague Art Association Umělecká Beseda, to which his youngest son Karel, a painter, also belonged.*** Purkinje followed the systematic studies on subjective facial features at almost the same time as Goethe.25/ **** Much the same as Goethe, he regarded the eye as an active organ and not just as a transient medium.26 he described the eyes as follows: “owing to its direct connection to the brain, as the primary seat of the imagination”.27 he was convinced of this due to his observation: […] that when one looks at a succession of individual objects such as a long procession of horsemen, waves passing by, or the spokes of a wheel that isn’t moving too quickly, for example, a similar apparent motion of the actual moving object remains within the field of vision. This is based on temporal adaptation made by the eye muscles.28 These observations are similar to those made and described by the great English natural scientist Mark Peter Roget a few years later (1825). In the observations of Purkinje, Goethe or Roget, the active human eye gains in significance and value. Through the increased number of visual-experiments and the numerous publications on the eye and its function, it becomes obvious that the period around 1820 represented a new beginning for methodical and theoretical research into the physiology of the eye.

From this time forth, the eye is considered as a distinct and individual sensory organ.

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Many of Purkinje’s observations and experiments were soon forgotten and were only rediscovered for science many years later. For example, Purkinje had invented an ophthalmoscope and numerous other tools with which to study the choroids and cornea, the lens image and the iris (fig. 9, 10, 11). In 1837 he discovered a guide cell in the cerebellum, which is known as the Purkinje-cell today. It is the largest neuron in the cerebellum (fig. 12).* As a physician, Purkinje recognized the necessity of characterization in medicine, for mankind and for every living thing. The basis of the art of characterization must be strictly reserved for physiology. Because it is about the correct and definite insight into the natural spirit of a given individual: his relative health, his ability to take in outer influences and react to them, his constitution, his temperament, his sexual character, his age, his ancestral background that is based on his sex or family, and finally the influence that weather, sex, manners, profession and other civil accommodations may have.29

* The study of the plasticity of the synapses between the Purkinje cells and their parallel fibres has been an important field of study in neuroscience since 1969. The essential motivation came from the neuroscientist David Marr who assumed there was a relevant solution in learning new motor skills in that field. See David Marr, “A Theory of Cerebral Cortex” in Journal of Physiology 202 (1969), 437–470; John C. Eccles, Karl R. Popper, Das Ich und sein Gehirn 1977 (Munich, Zurich, 1989), 463.

his basic ideas – that the physician has to start looking at the patient as an individual, for example – were based on his optical experiments. his analyses on afterimages and reflex-images also verify Goethe’s notion that the eye represents a productive individual organ** that can produce images on its own. Purkinje’s consistent stance that the eye should be considered as an individual organ was derived from his studies on refleximages in the frontal cornea. It was in that process that he discovered that the cornea itself must be doubled. The second image occurs through the mirroring of the back surface of the cornea and the relationship of the two images to one another that can give information concerning the thickness of the cornea itself.30 his observation was also not duly acknowledged for a long time. Even the prudent natural scientist helmholtz did not recognize this phenomenon in 1856 during his optical experiments, although Purkinje’s instruments were surely much more primitive than those of helmholtz. Purkinje’s discovery of the two corneal images was again resumed in 1880 by the Swedish physiologist Magnus Blix.31 Between 1891 and 1898, the Danish ophthalmologist who worked at The Sorbonne in Paris confirmed Purkinje’s discovery of the doubled corneal image. Blix further developed this discovery and derived a model from it that could determine the size and intensity of images on the cornea 32 (fig. 13).

** In 1819 Goethe wrote on the subject as follows: “every eye can […] be understood as a separate individual.” in Ernst Beutler, ed., Gedenkausgabe der Werke, Briefe und Gespräche, 900.

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* The first scientific description on afterimages was published in 1738 by the physician and physicist James Jurin. Essentially, the optical focus and defocus of colors were determined. James Jurin, “Essay upon distinct and indistinct vision” in Robert Smith, ed., Compleat System of Opticks, vol. 2 (London: 1738) 115–171 and 168– 171; Ulrike Boskamp, “Nachbilder, nicht komplementär, Augenexperimente, Sehlüste und Modelle des Farbensehens im 18. Jahrhundert” in Werner Busch, Caroline Meister, eds., Nachbilder, Das Gedächtnis des Auges in Kunst und Wissenschaft, 52–55. ** The British poet, scientist and physician Erasmus Darwin was a member of the Royal Society since 1761. He was the grandfather of Charles Darwin (theory of evolution) and Francis Galton (behavioral genetics). *** The physicist Mach who researched and taught for many years in Prag referred to Purkinje’s early observations in his work Bewegungsempfindungen (“Sensations of movement”) dated 1875.

For a long time the phenomenon of afterimages* and apparent motion were central to Purkinje’s discoveries. He had learned – like Erasmus Darwin** before him – that, with the aid of galvanic electricity, apparent motion could be initiated. The luminous phenomena that occur within the eye after galvanic exposure can be all the livelier and can be made to occur more simply the more sensitive the nervous system being examined is. The greatest challenge lies in the consistent and precise measurement of the galvanism by which the variations in the individual standard could be displayed.33/*** Based on his observations of the riders passing by hour upon hour and the subsequent illusion that the houses in the surroundings would have the reverse movement is what Purkinje described as the so-called appearance of the afterimage and its relevance for seeing movement. The function of the retina played an essential role. What is being referred to here is … the sensitivity of the retina to stronger or weaker light; it would appear necessary to study to which degree of light and darkness objects of a certain size can still be just barely differentiated; which degree of lightness the eye can endure without blinding.34 And therefore as follows: Different people have different capabilities of perceiving afterimages that are evoked in the eye following the observation of opposite colors. After a certain period of time, traces of the afterimages remain.35 Based on Purkinje’s research and studies in the area of subjective perception of light sensation, the so-called entoptic phenomena,**** moved to the forefront in the nineteenth century. The phenomena concern afterimages, physiological appearances such as seeing lightning after being struck on the head. They take place within the individual’s visual perception and can only be seen by the person affected. Entoptic phenomena can therefore be symptoms for certain illnesses or just plain semblances.***** Around 1819, the young scientist Purkinje also began to look at the entoptic phenomena. He named the phenomenon he was observing Lichtschattenfiguren (light-shadow-figures). Thereafter many scientists described them, such Helmholtz, in his renowned Handbuch der physiologischen Optik. However, it was Purkinje’s assistant in Prague, the researcher Johann Czermak, who fully understood the light-shadow-figures as entoptic phenomena. Czermak expanded on Purkinje’s experiments as follows:

Fig. 9 Purkinje: Ophthalmoscope

Fig. 10 Ophthalmoscope diagrams by Purkinje, Helmholtz and Ruete

Fig. 11 Depiction of diagram of veins by Purkinje

Fig. 12 Purkinje cells

Fig. 13 Purkinje’s mirror image, depictions of the cornea

[…] when the eye is confronted with a rapid changing of illumination and darkness then the entire face is quickly covered by a chessboard-like pattern of light and dark squares. These become smaller and increasingly distinct as they move from the periphery to the center. on these ‘primary’ depictions ‘secondary’ ones appear in an alternating sequence […].36 The shape described by czermak as primary […] consists of a chessboard-like pattern in the central field of vision that increases in size toward the periphery. It can be best understood when one looks through holes or slits of a quickly rotating cardboard disk that has been directed towards an evenly clouded sky. Despite the completely neutral light of the lightgrey clouds there are the shady spots of the light-shadow-figures which take on a slightly subjective (violet) color. If one looks at the light of the clouds through colored glass, magnificent complementary colors appear, among other things. The so-called ‘secondary’ shapes Purkyne named ‘Eight Pointed’, ‘Snail Square’ and so forth are formed in random sequence on the checkered background and based on the same pattern.37 helmholtz characterized the Lichtschattenfiguren (light-shadow-figures) as follows: When the speed of the wheel is so fast that there is no longer any differentiation visible between the individual sections, then the number of sections appear to increase. These then form a grid of blurred and crookedly sketched poles which are longer toward the edge of the radius of the wheel. When the rapidity of movement is increased, the design becomes subtler and similar to that of a knitting pattern. It appears at the location of the flickering field, which corresponds, to the yellow patch. This is a round or oval shape with sharply contrasted light and dark comparable perhaps to a multi-petaled rose whose petals have a nearly hexagonal shape. In its center is a dark point, which is surrounded by a light circle. These same shapes can also be generated by turning towards an intense or vivid light with eyelids closed, moving one’s outspread fingers back and forth in such a manner as to create a fast moving alternation of illumination and shade for the eye. The important thing is to create a rapid change of shadow and light.38 Purkinje’s experiments were complex and damaged the eyes of the test person when they were exposed to them for a longer period of time. It is therefore understandable that – as czermak explained – only few researchers made the effort to repeat these arduous optical experiments or conduct new ones: the risk of danger to one’s own eye or that of the test

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**** As opposed to optical phenomena physical apparitions, that are perceived objectively like a solar eclipse or lightning in the sky during a lightning storm. ***** While scientific analysis of entoptic phenomena remained within the confines of perception psychology, these apparitions remained of interest to many artists in connection with their work. For example in art trends like op art or kinetic light-art and up to virtual art worlds with computer supported machines.

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person seemed to be too great.39 The most famous example for this was Purkinje himself and the researcher Joseph Plateau who went blind as a result of the intense and long lasting optical tests. The physicist Gustav Theodor Fechner also almost lost his eyesight due to his experiments. Purkinje’s insights were not initially acknowledged in many fields of study. however, researchers such as Plateau, helmholtz or Mach soon showed great interest in them. Joseph Plateau, who addressed the topic of afterimages in his 1829 dissertation, elevated Purkinje’s observations of the most important scientific studies in this field. helmholtz expanded upon Purkinje’s experiments on light-shadow-figures with rotating colored disks in his own studies. Mach, who later also taught in Prague, referred to Purkinje’s observations in his research on perception of movement.

The Explanation of an Optical Illusion: Peter Mark Roget

In 1824 the English physician Peter Mark Roget* made an interesting observation of a specific optical illusion during the course of his studies on physiological apparent motion such as vertigo caused by rotating the body. In 1825 Roget in the Annals of Philosophy released these studies.40 Shortly thereafter a German translation of the article appeared in Poggendorff’s Annals under the title Erklärungen eines optischen Betruges bei Betrachtung der Speichen eines Rades durch vertikale Öffnungen.41 Roget had noticed a curvature in the spokes of cart wheels that disappeared when the movement became very rapid. The peculiarity of this optical illusion is that the bend of the spokes are consistently convexed downward; the curvature remains the same regardless of whether the wheel is turned toward the right or the left of the observer. […] A specific speed of the wheel is required […] The curvature can be seen more completely when the spaces between the spoke –, through which one looks at the wheel – are narrow […] For the same reason this illusion is perceived best when the spokes are dark in color or shaded and when bright light is projected on the wheel […] It doesn’t make a difference when the number of spokes is increased within the allotted space except that the bent images of the spokes increase in number. […] In order to create these appearances it is crucial that a progressive movement occur simultaneously as a revolving movement. The true reason for this illusion is therefore also the same as the delusion that takes place when one sees a closed circle of light caused by a luminous object being rotated quickly. The impression is such that a sufficiently strong beam of light has a certain enduring effect on the retina.42 With this, Roget presented the inertia of the retina. he did not define the phenomenon as Nachbild or afterimage which scientist later used to describe the effect. Roget himself referred to a key question in Quarterly Journal of Science, Literature and the Arts dated December 1820. The author was referred to, and signed using the initials J.M.43/** In this article, the illusion is described but no theoretical explanation is given.44/ *** At the end of his remarks, Roget noted, “a new means is delivered that measures the effect of light on the retina.”45 The premise would have to be the exact determination of the speed required so that the apparent forward movement of the spokes becomes visible.

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* Peter Mark Roget became famous as a lexographer with his work Roget’s Thesaurus that came out in 1852.

** It is suspected that with J.M. the editor of the journal, John Murray is being referred to. At the time it was very typical that the editor would sign with a monogram. Poggendorff always signed his commentaries in the Annalen der Physik und Chemie with a “P”.

*** Based on his observations, Roget created the mathematical formula y= (b-x)tangx, in order to arrive at the curvature of the curve. According to him all such curves can be computed with the same formula.

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Roget’s new insights and their formal description became the physiological and psychological basis for automatic and artificial generation of the illusion of movement (fig. 14).

Fig. 14 Roget, wheel spokes, 1824

The First Motion Picture Machine *: Joseph Plateau

If things had gone according to his father, Joseph Plateau would have pursued a career as an artist. That is why the young Plateau first went to art school. Shortly after his father died, Plateau followed his second great passion: the natural sciences. His educational background in art became very useful when it came to scientific illustrations to accompany his complex commentaries. Having known about the observations from Purkinje to Roget, he described a new means of using anamorphic image disks in his dissertation dated 1829. In it he described the prototype for his invention, which he presented as an Anorthoscope in 1836 at the Brussels Academy. One of Plateau’s primary interests was the study of the function of the retina: the reaction time for seeing, the retina’s sluggishness or the duration of lingering impressions and duration of afterimages. At times these were simple and quite ordinary observations that convinced Plateau to examine a specific topic. For example, the phenomenon that occurs when a glowing piece of coal is quickly swung around in the dark and the observer sees a glowing curve as if the piece of coal left behind tracks of its path. This fact proves that the impression of light on our eye has a certain duration. After that object is no longer physically there, the image still remains there temporarily. 46 Another example for the appearance of an afterimage on the retina which fascinated Plateau was when one looks at a white piece of paper that appears light due to the sunlight, then closes one’s eyes for a moment, the white image still lingers on the retina for a certain amount of time. He intended to verify this observation with experiments. He wanted to measure how long it took for the luminosity (light intensity) and for how long the impression lasted. The circular path created by the rotating glowing piece of coal gave him an idea: allowing small, colorful objects to rotate long enough to give the impression that the objects were rotating independently. Is seems to follow, that, in order to measure the duration of the impression of the little objects on our facial organ, one must rotate said object in a circular movement and speed it up until it ap-

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* This description in connection with Plateau and his 1829/32 invention is based on the film critic M. Quigley Jr. in Quigley, Magic Shadows, The Story of the Origin of Motion Pictures (New York, NY, 1960), 89.

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pears to form a full circle; the duration of this orbit, which can be calculated without a problem from the number of orbits in a given time period, would then be the duration of the impression.47 In 1765, the Irish natural scientist Patrick d’Arcy had calculated the duration of visual perception of a glowing piece of coal. Thomas Young, an English ophthalmologist and physicist, was the first person to successfully measure the wavelength of light. Although he had never tested the retention time of light on the retina, he claimed that it clearly lasted longer than the actual light stimulus. And, that the impression left behind depended on the intensity with which the light was cast.48 The researcher Plateau, still young at that time, attempted to test and determine the duration of the retention time of various colored objects in ordinary daylight. he referred to d’Arcy’s procedure and measured the duration of the impression on the retina with a similar instrument: the apparatus created for these experiments consisted of several vertically placed wheels. These were set into motion. he did this in such a way that the last wheel was the fastest while the others were weighted down to move more slowly. A special pointer made it possible to regulate and read the rotation speed per orbit. Behind the pointer was a disk that Plateau had covered with black velvet. The objects to be set in orbit were colorful, semicircular paper strips (white, yellow, red and blue) that were centered on the axis of the pointer. Despite the many experiments Plateau had conducted, he was not completely satisfied with his first results because he could only achieve a mediocre result. In reference to d’Arcy’s results, he noted that he had sped up the machine to the point of leaving the impression of a glowing ring; d’Arcy remained guarded about the effect of a ring on the retina, however.49 D’Arcy’s experiment with the glowing coals had been conducted in the dark, while Plateau had assumed that the sensitivity of the human eye should be evaluated differently in the dark. The experiments he conducted with the white and yellow paper strips provided the most lasting impression, followed by red and blue. Plateau wanted to more accurately determine this ranking of colors, so he divided a paper disk into equal sized sections (fig. 15). Two of these were added to the disk so that it had a trapezoidal shape. Twelve of the trapezoidal segments were assigned a color, the others were blacked out. In a variation of this, the previously blackened sections were removed and Plateau replaced them with a black disk mounted behind the colored one. When the disk was rotated at an average speed, there was “only a quiver: a rapid sequence of light and dark

lights”.50 When the velocity was increased, “the unclarity was reduced and a uniform color appeared.”51

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Plateau described that the colored and the black fields appeared in the nuances of black plus the corresponding color. Removing the fields and placing an object between the colored disk and the one covered with black velvet, the object would appear “visible like through a colored veil”.52 Plateau had discovered that reaching a certain rotation speed of the disk was essential for the eye to observe an even color tone. his next step was to calculate the exact speed required to recognize each individual color tone. The new results were contrary to the original experiment. The colors blue, red, yellow and white afforded the longest retention period on the retina, whereas blue lasted longest and white the shortest period of time.53/* Plateau concluded that white left a stronger impression in the first experiment but at the fastest speed, it lost in duration. While blue, on the other hand, left the weakest impression and had the longest aftereffect. Plateau conducted further similar experiments with two disks divided into black and white sections (fig. 16). Although the invention of optical devices that created optical illusions such as the thaumatrope or kaleidoscope in 1827 54 they also led to a series of methodological tests the cart-wheel effect described by Roget remained key to Plateau’s research.

* The measurable values of the orbital duration were depicted on a chart.

Fig. 15 Rotating disk with black and white sections

Fig. 16 Rotating disk with color segments

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* Johann C. Poggendorff reports on this in detail as editor of his 1834 annals.

The Phenakistoscope or the Stroboscopic Disk

Further experiments on the lingering effects of light on the retina led to Plateau’s most popular invention: the phenakistoscope. he described this apparatus as a special rotating disk with which, for the first time, fixed images could be set in motion. In november 1832, Plateau sent the physicist Faraday his apparatus prior to his giving a detailed report on it the following January 1833.55 only a few weeks later, Simon Stampfer, who lived in Vienna, came out with a report on a very similar invention (fig. 17). Stampfer called his picture disk Stroboscope. Both inventors, Stampfer and Plateau, had independently invented very similar devices that would create the first moving pictures.56/ * It is plausible that this occurred because both were familiar with the so-called Faraday’s Wheels 57 (fig. 18). Faraday describes his device with the two gear wheels as follows: If one rotates the wheels at the same speed and in opposite directions, and the eye is in a position to see both freely, adjacent to one another, one is only aware of a single, even veil. […] When the speed of the two wheels differs, the picture is no longer still but instead revolves in the direction of the wheel with the higher speed. When the eye isn’t focused on the wheel axis but still in a location that both partially cover one another, one can behold a crooked illusion of a varied shape.58 Faraday reported that in developing his device he had been inspired by the phenomenon of apparent motion of a tiny rotifer. This primitive multicellular organism that was only visible with a microscope had two coronas with cilia on its head that looked like two wheels, which were virtually in constant motion. Two disks mounted on one axis were developed for Plateau’s and Stampfer’s stroboscope. one of these had slits on the circular rim while the other had images on it. These performed singular successive steps of an activity. Plateau’s first image was of a dancer whose various phases of movement were painted on the disk (fig. 19). Stampfer chose a hammer, which hit a detonator cap with the corresponding revolution of the disk (fig. 20). When the disk was set into motion and held in front of a mirror, an optical illusion occurred in which it appeared as if the movement was taking place in a flowing sequence of motions. Thus the stroboscope became enormously popular and sold successfully as a children’s toy.

Beyond that, it served as a very useful device in the study of seeing virtual movement and afterimage movement, which would ultimately lead to the invention of film.

Fig. 17 An excerpt of Simon Stampfer’s and Mathias Trentsenšky’s patent application in Vienna, Austria

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Fig. 18 Faraday’s rotifers

Fig. 19 Joseph Plateau, disk with dancers

Fig. 20 First depiction of the Stampfer/Trentsenšky disk with hammer blows

Inventions with Stroboscopic Effects

only a few months after Plateau’s invention had been released, in the summer of 1833, William George horner developed an improved model in Bristol, England, called the stroboscopic cylinder or life-wheel. The inventor introduced it in the January 1834 edition of the Philosophical Magazine in london. In that same year, it appeared in the Poggendorffer Annalen to the scientific world as well.59 horner called his apparatus daedaleum, basing the name on the famous artist and architect of antiquity who is supposed to have developed a similar artwork. The daedaleum proved to have some advantages over the stroboscopic disk and the phenakistoscope. It consisted of a hollow cylinder that could be turned on its axis. It was open on the top with slits cut out at equal intervals around the upper edge. A strip of paper with a sequence of pictures was placed on the inside. Without the help of a mirror, picture sequences were generated that could be viewed through the slits simultaneously by several people. The daedaleum brought on the market as a toy was called zoëtrope, wonder drum or wheel of life. It quickly became popular and was produced and sold until the beginning of the twentieth century. William G. horner was also the first to attempt to explain the stroboscopic phenomenon mathematically. As a premise for the occurrence of the stroboscopic illusion, he measured the distance between the respective viewer and the cylinder. An entirely different but equally innovative invention for the presentation of moving pictures is traced back to the Austrian artillery captain Franz von Uchatius. The field marshal-lieutenant Ritter von hauslab commissioned Uchatius to think of some way to project moving pictures on the wall based on the stroboscopic disk. Eight years later, on April 21st 1853, Uchatius disclosed his studies on the “Apparatus for Showing Moving Pictures on the Wall” at the Wiener Sitzungsberichte.60 his device was the first hand-crank film projector prototype (fig. 21): The lighting-device consists of a detonating gas current calcium cylinder B and a collecting lens c that radiates converging rays and can only illuminate one image at a time. With the help of a simple mechanism of crank D, the light is turned at a slower or

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faster pace in a circle. The illuminating device remains stationary because of its weight and because it is hung on pegs c. The two flexible gas pipes, D and E, move back and forth through the perforated floor of the box. The lead mass E functions as the counterbalance of the illuminated device.61 The spectrum of visual possibilities that were created with the novel gadget that produced stroboscopic illusions opened new scientific vistas within the community of researchers working on this particular area of perception. The unresolved issues of procedures on how the human eye perceives motion, how apparent motion occurs and the measurability of the moving afterimage became essential topics of research during the nineteenth century. This also resulted in new discoveries within the field of modern perception psychology. In the same year that Plateau constructed his phenakistoscope and Stampfer introduced his stroboscopic disk, David Brewster of Edinburgh presented his latest observations of retinal perception at the Assembly of British natural Scientists in oxford. In the field of visual theory, it was still believed that the “light that radiated off visible objects only appear on that part of the retina on which it falls directly.”62 Brewster refuted this line of thinking and argued that for certain exceptions observed by him: when light in the form of a glowing line or bright points reaches the retina, “a series of odd appearances” occurs.63 Peering through several parallel slits, such as those of the teeth of a comb, the continuous succession of lines seem pronounced and even more so when the comb is moved slanting in the opposite direction of its teeth. It is then that the lines no longer appear to be straight, and new black lines stand out. Brewster alluded to the similarity of this phenomenon with what happens when black parallel lines are drawn on white paper, which is also comparable to the ocean depth markings on maps. Such varied and sometimes seemingly simple field observations by scientists yielded increasingly concrete physiological points of reference that freed the act of seeing from mystical implications. It could be considered in an enlightened, empirical manner and as such, the biological connections that occurred within the human eye could be more readily interpreted.

Fig. 21 Franz Uchatius: Projector for moving images onto a wall

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The Talbot-Plateau Law of 1834/35

In 1834, the inventor of the negative image in photography, William henry Fox Talbot, reported on his experiments with polarized light in the november issue of Philosophical Magazine. In the second section of his description, he outlined his experiments on photometry or the measurement of the intensity of light. he observed that he himself had made these observations nine years before, and that he had intended to publish them but it was only after having read an article in a “foreign journal and having recalled my attention to this subject” 64 that prompted him to release his earlier studies. In his introduction, Talbot wrote “Photometry, or the measurement of the intensity of light, has been supposed to be liable to a peculiar uncertainty”.65 The relatively simple example of a piece of glowing coal being moved around the room rapidly had already demonstrated the appearance of a ring of light. According to his observations, the ring of light had to give off the same intensity of light as the charred piece of coal. There can be no doubt, as it seems, that such must be the case; for if the luminous circle sent more rays to the eye, it would likewise send more in every other direction, and thus the apartment would become more illuminated than before, which is not the fact. If, then, the total quantity of light remains the same, it follows that its apparent intensity must have diminished exactly in the same proportions as its apparent area has been enlarged. 66 Talbot now didn’t use glowing coal for his experiment but used a rotating white disk instead, on which a wide black spiral was placed in one section (fig. 22, 23). There was widespread interest in this experiment. First it was Plateau who shortly afterwards identified new discoveries in the area of photometry and tested Talbot’s observations with his own experiments in 1835. Talbot’s basic photometric principle seemed applicable on many levels. The experiment of alternating the intensity of color that Talbot used to attempt to define a fundamental photometric principle would ultimately become known as the Talbot-Plateau law. In an essay dated 1835, Plateau noted that he had performed trials in photometry even before he had heard about Talbot’s experiments. Both physicists had arrived at the same conclusion: when a glowing object is consistently and intermittently shone on the eye, and the successive moments of its appearance occur

at such short intervals that the eye cannot distinguish between them but experiences them as a continuous sensation, then the apparent magnitude of the object is weakened in the ratio of the sum of appearance- and disappearance- periods to the mere duration of its appearance.67 It had already been established that when a white disk with black sections is made to rotate, the disk is grey at a certain speed. When he continued the experiment, Plateau used a white sheet of paper and a disk made of the same white paper that had a specific number of black sections marked on it. Both objects, the paper and the disk were placed at unequal distance in front of a lighted candle. Plateau varied the distance until the light on the disk and the paper were virtually identical. Through the spaces between the light source and the object, the ratio of the colors of both objects could be calculated. In the case of dual coloring, the area surrounding the spiral was blue, and the rest of the disk was yellow. At the appropriate rotation speed, the center of the disk appeared a pure blue and the outer edge was an intense yellow. Talbot noted the precise moment of the color change with great enthusiasm – “the most curious part of this experiment was to observe the neutral tint, which the color passed at a certain point.”68 Based on Talbot’s recommendation, the experiment was expanded to use a rotating mirror to move the image of a glowing object quickly around in a circle. When the eye is positioned in a manner to catch the reflecting beam of light with each complete rotation of the mirror, and if the speed of the rotation is such that the interruptions of light are not visible, the eye will register a continuous movement of a glowing object. The brightness of the light corresponds to the brightness of the object to the same extent as the circumference of this object corresponds to the traverse length of it. one must also consider the reflection of the light in the mirror dims the intensity of the light that, of course, is variable depending on the angle at which the eye perceiving the rays reflect off the mirror.69

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Fig. 22 Excerpt from the article “Experiments of Light”

Fig. 23 H. F. Talbot’s spiral, 1834

Gustav Theodor Fechner’s Subjective Colors

In 1838, Gustav Theodor Fechner * published a report in the Poggendorffer Annalen about a disk used for the production of subjective colors.70 The French monk Bénédict Prévost had previously experimented with subjective colors in 1826. In his experiment, subjective colors such as red or blue were produced by rotating the black/white sectors of the disk. In his publication Fechner referred to Talbot’s observations of the rotating color disk that produced an even grey. he expressed his astonishment that despite countless experiments with the black and white colored disks there was no special focus on the phenomenon of the subjective perception of color. he went on to experiment with a disk that had a radius of 18 inches and was divided into 18 concentric rings. The innermost ring was completely black, the next one had 20% white added to it, the next one 30% and so on until the final, outer ring which was 100% white. The ratio between black and white was equivalent to the form of an Archimedean spiral (fig. 24). When this disk was turned, I was astonished that instead of shades of pure grey, my eye perceived all sorts of alternating colors from the middle to the edge and depending on the rotation speed. The colors were not overly intense nor were they without vivacity. I showed this phenomenon to numerous people and learned that they perceived them with varying degrees of distinctness that, considering the subjective origins, was not necessarily remarkable.71 The mathematician and astronomer August Ferdinand Möbius** made Fechner aware of another interesting phenomenon with these experiments, besides the individual and varying color perceptions. When the disk was turned to the right, (see arrow in fig. 24) the black part expanded, and when it was turned to the left, the black form contracted, which Fechner referred to as “when a shape pulls itself together”.72 The direction of rotation also affected the way the color was perceived. When the disk was rotated in the direction of the arrow, the black edges appeared to be yellowish-red. When turned in the opposite direction, they appeared to be bluish-green. The effect of the optical enlargement or diminishment of the image occurred earlier.73 Fechner also used a disk on which there was only a single white section of a semi-circle on a black background or a black semi-circle on a white background depending on the direction of the rotation. When rotated at a moderate speed, the disk appeared to be

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* Gustav Theodor Fechner (1801–1887) wrote extensively. Under the pseudonym Dr. Mises he published not only scientific papers but also poems and satirical writings. In Psychophysics (1860), within experimental physiology and within the field of psychology mathematics was emphasized and this led to innovative perspectives (Brücke and Mach). The introduction of the term experimental aesthetics can be traced back to Fechner.

** He discovered the Möbiusschleife in 1858 (Möbius strip or Möbius band) which was named after him.

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yellow. When the speed was gradually increased, it appeared to be yellowish-green, green and finally a light blue. When the velocity of the rotating disk was increased, the entire surface of the disk appeared to be multi-colored. Toward the end of the nineteenth century, c. E. Benham picked up Fechner’s idea of subjective color perception with the help of the rotating disks. he used a disk that was painted half black. The second semi-circle showed partial semi-circular lines. As soon as the disk rotated, the viewer could discern pale hues of color. The Benham Disk came on the market as a toy in 1894. The special effects of the disk that had become important in the research of color perception in cognitive psychology are generally referred to as Prévost-Fechner-Benham-Disks by peer review boards. This popular work resulted in a double volume in leipzig in 1860 called Elements of Psychophysics and summarized Fechner’s perceptual observations. It was of crucial significance for subsequent scientists such as hering and Mach, for example.

Fig. 24 G. Th. Fechner’s spiral

Four Notes on Afterimages

In the middle of the nineteenth century, Plateau confronted the experts with four treatises on the theory of the afterimage. These works are more generally referred to as Four Notes. These notes were commented on with great interest and led to further experiments that examined the afterimage on the retina. The First Note was published in 1849, and much like the others, referred to “the new and peculiar use of lingering impressions on the retina.”74 By constructing two disks that Plateau had painted with various colors and had put in motion, he attempted to define these impressions more accurately. one disk was divided into eight equal sections, with opposing sections in either red or blue fields. The remaining four sectors were black and white. The second, and black disk featured two additional cutouts (fig. 25a, 25b) and was set into slightly faster rotation. The pink tones immediately changed to a deep red, and then again transitioned to a black shade, etc. In his Second Note (1850), Plateau examined how lingering impressions on the retina depended on the rotation speed induced by his picture machine, the anorthoscope.75 This instrument consisted of two consecutively positioned disks. The one in the rear was transparent and had four images painted on it, while the front one was opaque and had narrow, straight slits. Plateau had not previously gone into detail on the rotation speed, nor the direction and shape of the slits (1836). After that, he experimented with varying the direction and speed of both disks. The anorthoscope, which Plateau had already presented for sale to an interested public, served as the testimonial for the comparison of the parameters. The ratio of the speed of the two disks was originally 4:1 for the transparent to opaque black one. Because each change in speed and every variation in the number of slits on the black disk also changed the perception of the distorted images, Plateau concluded that the speed, the direction and the number of slits determined the instant at which the distorted image could be recognized as being consistent.76 In the Third Note (1850) Plateau attempted to improve his phenakistoscope (phantascope) for practical application. What he found especially disturbing was that the observer could only look at the pictures or moving shapes with one eye, and that it wasn’t possible for several people to look at it at the same time. he was hoping to achieve a better solution by combining the anorthoscope and phenakistoscope.77

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* Two drawings are required for the stereoscope that relate to one another in a certain way and are positioned on the interior side of the device.

** Peter Weibel sees the beginnings of film history to correlate with Mark Peter Roget’s 1824/25 observations. In Peter Weibel, Time Slot (Cologne, 2006), 9. I think that this date should be moved back to the moment when attention was first paid to apparent motion in the natural sciences at the end of the eighteenth century. With the publications by Marcus Herz (1786), followed by Purkinje (1819/23) and John Murray (1820) all of which Roget referred to in 1824.

The physicist charles Wheatstone, famous inventor of the stereoscope, had influenced Plateau in such a way that he combined the principle of the phenakistoscope and the stereoscope. hence the figures were not only moving but they also appeared to be three-dimensional. Plateau’s commentary is significant here: Assuming the possibility of adding this effect to the phenakistoscope, and by combining both instruments, the figures that are simply sketched on paper, are compellingly lifted (en ronde bosse) and seem to move around, so that they come to life. This means carrying the illusion of art to its apex.78 however, Plateau recognized the difficulty in sketching the images in such a way that the stereoscope could register them.* he found a passable yet complex solution: In order to sustain a pair of drawings that the stereoscope would not show as a mere perspective of lines but instead as objects with convex forms similar to an ornamented column with light and shade. Mr. Wheatstone had the idea of using photography. Two daguerreotype images of the same object are placed next to each other in two different positions and relate to each other in the necessary manner. one could, for example, take the sixteen modified consistent representations of which one wants the apparatus to create depictions and model them in plaster. Then take a pair of pictures of the same sixteen with the daguerreotype and finally transfer the sketches in the necessary distortion onto two disks. Without a doubt this would entail long and very precise work, but the results would be richly and admirably rewarding.79 Plateau and Wheatstone were thus the first to record in print their theoretical ideas as to how to construct pictures in such a way as to make them move and have depth. overall their idea already corresponded to the medium of film, which would not be shown for another forty years.** In his closing Fourth Note, Plateau worked on generating the events on a rotating disk rather than the phenakistoscope.80 The rotating disk that was used had a radius of circa 25cm, showed an Archimedean spiral with a coil spaced about 12mm from the center. Then you draw a second spiral, parallel to the first, but four millimeters away from it. These two lines together form a spiral shaped strip on the plate, four millimeters wide. Then, the description goes, three circles emanate from the center of the disk with the respective measurements of 1 1/2, 5 and 8 1/2 cm in diameter. Then the last two strips are broken off at the point at which the spiral-shaped lines intersect, so that the spaces between the coils of this strip are extended. Then the small circle at the center must be blackened, the space between the second and third

are painted yellow, and the remainder red. however, the coils of the spiral strips must remain white. The blue, yellow and red colors must be intense. Then, if this plate is rotated in the direction the arrow indicates, and with the velocity regulated by hand, the black circles and the colored areas retain the same appearance, which it clearly must. only the spiral strip appears as a row of sharply drawn rings that are created successively around the edge of the black circle. Then the rings proceed through the blue, yellow and red areas and finally disappear at the circumference of the plate. Were the plate to be rotated in the opposite direction, the rings first appear at the circumference, constrict, and then disappear one by one within the black circle.81 Plateau compared these optical illusions with the threads of a screw that would revolve around their own axis at a very high speed. he also noted that eight different test persons perceived this illusion differently. Fechner reported on quite similar observations with his experiment from 1838 on subjective color perception. Almost simultaneously, in 1851, Talbot also suggested that with the help of snapshots and a battery operated light source he could produce the impression of moving objects. John Tyndall based his idea on the experiment in 1850, which analyzed “the movement of streaming water illuminated by an electric spark”.82 Talbot’s concept remained unexecuted.*

Fig. 25a Joseph Plateau: rotating disk, experiment on afterimage, circa 1849

Fig. 25b Joseph Plateau: rotating disk, experiment on afterimage, circa 1849

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* Ten years later, Du Mont wrote the following on the snapshot: “Today photographers are able to make snapshots on highly sensitive surfaces in light; they photograph a moving object like horses etc. But they have never thought about doing more than taking a picture of these objects and never wanted to take several consecutive pictures or consecutive movement phases.” in Karl Wilhelm Wolf-Czapek, Die Kinematographie, Wesen, Entstehung und Ziele des lebenden Bildes, (Dresden, 1908), 36. The photographer Eadweard Muybridge first depicted these phases of movement in 1877. He was the first to take a series of photos as Du Mont had suggested in 1861. Muybridge’s method was cumbersome and expensive. The solution to the problem came through the invention by the astrophysicist Pierre Jules César Janssen. He used a so-called “Maltese cross wheel” in 1874. Janssen only made photo series that had no time based movement connected to them. In 1870, at almost the same time the Parisian physiologist Étienne Jules Marey studied sensory perception. Inspired by Muybridge’s photographs, he began to construct a special apparatus to chart movement. See ibid., 36–39.

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Experiments on the Simulation of Riparian Illusion with the Oppel Antirheoscope

The moment that triggered the physicist Johann Josef oppel from Frankfurt/Main, Germany, to construct the antirheoscope was when he intended to repeat the phenomenon that occurred during the so-called Ufertäuschung (riparian illusion). Precededing this were numerous observations on entoptic phenomena 83 in nature. oppel described these in great detail on July 13th, 1853 in Rhine Falls in neuhausen by Schaffhausen. This is the precise location at which the Rhine river very noisily splits off of lake constance. oppel’s traveling companion had made him aware of this natural phenomenon. The scientist described it as a strange movement of the ground below our feet […] A few seconds were enough to establish the belief that a mere optical illusion was taking place. This was without a doubt brought about by the observation of the moving water which had been observed only a few moments before.84 A skilled mechanic by the name of August Fritz crafted a special perception device for oppel in his workshop. Basically the device consisted of five barrels each with a diameter of 10.5 inches. They were covered with white paper and spirals were drawn on them with a quill. All of the barrels could be moved simultaneously with the help of a shared drive. The drawings on the barrels were comparable to the serpentine windings of a screw or with the waves of flowing water, which were to be imitated. In his written explanations, oppel referred to a very similar experiment with rotating disks that Plateau mentioned in his Fourth Note. According to oppel, he had not been acquainted with the previous studies done by Plateau in 1849/50, at the time of his experiment. During a lecture at the Frankfurt Physics Association, oppel presented a collection of opticalchromatic devices. Among them there was a white disk with a red Archimedean spiral painted on it. It was rotated quickly with the aid of a small mechanism. “When, for example, the waves that were constantly getting bigger suddenly stood still, one of the members present commented that these now suddenly appeared to be getting smaller which meant getting closer to the center”.85 oppel purposefully chose light colors for the paper and the spiral; that way the contrast appeared smoother in comparison to the strong contrast of black and white that Plateau had

created. Besides that, the light colors had the advantage that the eye became less tired than with Plateau’s earlier experiments. oppel was interested in the much discussed issue of whether the experiments on perception and the theories that are derived from them should be understood to be part of the physiological or the purely physical optics.86 For this reason, oppel looked into whether “[…] complementary colored afterimages were merely a restricted sensitivity of the eye because of the special, ongoing color effects received and, due to that, a conditional emergence of the […] still remaining complementary color”.87 In comparison, Plateau’s physiological theory was based on an independent response of the eye. In the end, the physicist oppel came to the following conclusion: “a purely physiological process exists […] here, where an adequate explanation for the optician has to be proven within a less accessible area of the natural sciences.”88 oppel also developed another device that he called the anaglyptoscope.89 In principle, it was the predecessor of the twentieth century holograph (fig. 26). With the help of a fairly simple device – a recessed shape, for example – the raised form of a relief or an apparent inversion of the relief was perceived (plaster mold, surrounded by a protruding frame, mirror and candlelight).

Fig. 26 Experimental arrangement for an anaglyptoscope

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* Which according to Wheatstone’s definition would have been impossible because to date only those visual inversions of reliefs could be produced that were described as pseudoscopes. The wellknown physicist and perception scientist Heinrich Wilhelm Dove expanded on the idea in 1859. Contrary to Wheatstone, he wanted to recognize all the wellknown “facial deceptions” (Gesichtsbetrüge) as examples for pseudoscopy. See Heinrich Wilhelm Dove: Optische Studien, Fortsetzung (Berlin, 1859), 19.

Zöllner’s Illusion

The German physicist Johann Karl Friedrich Zöllner had been focused on Plateau’s and oppel’s experiments for a long time. he tried to unite his own so-called Zöllner Figure – an optically conspicuous illusion – with those of Plateau and oppel. With his optical pattern Zöllner was able to keep an active discussion going among the scientists on perception psychology. he himself wanted to see in it the phenomenon of a so-called pseudoscopy.* The Zöllner Figure was examined in detail and was included in the experimental discussions of such renowned colleagues as Franz Brentano, Ernst Mach, Alois höfler or Friedrich Schumann. Entire dissertations had been written on Zöllner’s discovery, such as the one by the experimental psychologist Vittorio Benussi, who in his later studies on apparent motion (as of 1911–12) brought the Zöllner Figure to life by means of the stereoscope. The observer of Zöllner’s illusion is led astray by many curved crosslines imposed on two parallel lines. According to Benussi, the French Renaissance philosopher Montaigne had already been familiar with this effect (fig. 27a, 27b, 27c). In his paper dated 1860, Zöllner emphasized that the optical illusion, which he discovered were purely psychic apparitions and neither mathematical nor physical phenomena.90 Based on the assumption that the width of the main lines was dependent upon the “connecting lines of both eyes, a maximum [width (translator)] could be reached when both the lines crossed at an angle of just under 45 degrees”.91 he discovered that it wasn’t even necessary to draw the main lines since the consistent subsequent cross lines were enough for a reaction from the eyes. As a result of this discovery, Zöllner looked for a practical, working explanation in which he analyzed the number of cross lines, their distance from one another, their angle in the direction of the long lines, the distance to these, and the intensity of the drawing.92 With his research, Zöllner was able to determine “that the pseudoscopic deflection of the main line directed towards the cross line is very specific, that both always seem to converge or diverge alternatingly towards opposite sides.”93 he added further, that the intensity of the drawing or how it is raised from the white surface of the paper is completely without impact. The con-

sciously produced illusion of a shape already arose as soon as the slightest pencil stroke had been made that even began to indicate a shape.94 This description by Zöllner allows one to understand the precision with which he conducted his observations. In direct reference to oppel’s experiments on the specific nature of our sense of color contrasts, Zöllner deemed it necessary to explain the illusion in terms of contrasting effects. A focal point of the research on sensory perception in the nineteenth century centered on finding the location of the organ that was responsible for perceiving movement and speed. Zöllner’s research too was focused on this topic. According to Zöllner, Plateau should be credited for having connected the concepts of movement and the perception of colors.95 Plateau’s studies as well as those by oppel had inspired him to experiment with optical sketches with movement while he could identify completely with Plateau’s enquiry into the seat of the perception of motion – namely “whether [these] seemed to be justified in the most directly affected organ (the retina) or in the organ where the function of the soul took place (the brain).”96/* Zöllner’s observations were dedicated specifically to the problems of parallelisms: when we might perceive the concept of two lines as being parallel, and how we might determine this parallelism when our visual perception was unable to convey the parallel lines even though we were aware of the optical illusion. We define two lines as being parallel when the shortest distance of all its points are the same. When the lines are so far apart that they can’t comfortably be recognized, measuring instruments need to be used to compare the distance at various points in order to finally determine whether the equal or unequal points are parallel or not parallel. In this case the concept of parallelism of the lines results in a logical conclusion that has occurred by our intellect as well as certain facts of observation.97 consequently Zöllner substantiated his explanation: The concept of parallelism or non-parallelism of two straight lines, on the one hand, and repose or motion of a body on the other hand, are not a direct result of sensory perception. Rather, they are the result of logical conclusions based on the data observed by the eye and that have been reached with the help of our reflection or comparative understanding. only the speed with which these very rapid successive operations of understanding occur prevent us from consciously perceiving them individually.98

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* Just a few years later, Ernst Mach finally found a solution: that the organ associated with motion could be found in the passageways of the ear. The ideas presented by Plateau played an essential role for Mach.

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* In 1913 Vittorio Benussi published his first monograph on the concept of time in psychology.

Zöllner recognized that for the conceptualization of two parallel lines, a certain period of time was needed: “The notion of rest requires a greater period of time to develop than the notion of a body in motion […] The notion of parallelism requires a greater time to develop than the notion of convergence or divergence of two straight lines.”99 Alexius Meinong and especially Vittorio Benussi with the older Graz Gestalt theory or Graz production theory integrated the time element into the perceptual process at the beginning of the twentieth century.* This could explain why the older Graz production theory is referred to more frequently in current cognitive psychology than the more recent Berlin Gestalt School of psychology. Zöllner finally tested his theoretical ideas about optical movement phenomena with Plateau and oppel’s experiments. I am choosing the simplest case and assume that a series of points that are at the same distance from one another are moving, for example, in a straight line from left to right at a uniform speed. When the motion has continued for a specific period of time, we expect it to continue for the ensuing moment with even more certainty the more often our expectations are met, that is to say, the longer the motion occurs. When, therefore, the moving dots suddenly stop and are at rest, this phenomenon remains in our consciousness because of the altered effect on the retina. [And (author)] we are able to perceive this change only as a change of movement because, for the creation of the concept of rest, our observation would have had to take a specific period of time. When considering that the points had previously been moved, the greater our expectations of the duration of the observed movement, the longer our ability to observe must be engaged in order to produce the concept of rest. Since, as seen above, we are even more convinced of an object being at rest, the longer the period of time we have observed said object.100 Zöllner was looking for a physical law that had to exist between movement and apparent motion. Just as oppel had observed, Zöllner also recognized “that at a very high speed it is no longer possible to distinguish between individual objects. As a result, the notion that these objects are moving at all no longer exists.”101 his conclusions are as follows: “The number of mental images which can be conceived of simultaneously is fewer, the slower the movement is.”102 And furthermore: “that the apparent motion observed on the originally moved objects must be transferred to all the images on the retina which occur from the end of the original movement at a calculated time and which must be proven.” 103 Zöllner

came to the conclusion that solely through the internal visualization of movement, we also perceive this movement as being real with our eye – this image can also be achieved with closed eyes. Were an object that had been moving to come to a sudden halt, pseudoscopic effects would result.104

Fig. 27a Zöllner illusion

Fig. 27c Zöllner illusion

Fig. 27b Zöllner illusion

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* Vittorio Benussi was familiar with Filehne’s theory and his experiment on the representation of the three-dimensional. They could have influenced him in taking Zöllner’s illusion as a template for his experiments on apparent motion in 1912 with a modified stroboscope. The influence that the rather unknown psychologist Filehne had on Benussi has not been explained further to date. Filehne, Die geometrischen Täuschungen (Leipzig, 1898), 48.

Reflections on Zöllner’s Illusion: Wilhelm Filehne

The relatively short description Zöllner delivered in twenty-one printed pages resulted in a great deal of material for discussions and suggestions, which ultimately led to an expansion on his findings about the perception of apparent motion and parallel lines or non-parallel lines. Almost fifty years after the appearance of the essay, there was still a great interest in Zöllner’s illusion. In 1898, the physiologist and pharmacologist Wilhelm Filehne (1844–1927) published his considerations and additional experiments of his own in the newspaper Zeitschrift für Psychologie und Physiologie der Sinne (Journal for Psychology and Physiology of the Senses).105 Filehne rejected the term illusion for Zöllner’s pattern, as did Vittorio Benussi many years later: These perceptions are called ‘illusions’ but one should not be deceived by such a term. If one calls these perceptions illusions, then seeing the physicality of any drawing or photograph is an even greater illusion. Yes, when we see the dimensions of the real world, even though they are real, they become physiologically and psychologically an overall illusion, albeit a convenient and enjoyable one. 106 In order to support his theories, Filehne constructed a three-dimensional model that essentially echoed Zöllner’s illusion spatially* (fig. 28a-d). Filehne assumed that we perceive everything connected to a space either consciously or unconsciously. Perhaps that is the reason for creating a model that would also take the relationship to space into consideration. During his experiments on the origin of apparent motion, he made an interesting observation: if one turned the Zöllner illusion by 90º so that the primary lines were to be horizontal and viewed them through a black pipe, movement immediately appeared in the rendering. The impression that the cross-lines wandered or jumped was created.107 This kind of movement was equally apparent, but less so, when the main lines were in a vertical position. According to Vittorio Benussi, the theories presented by Filehne on the Zöllner illusion were similar to those by Armand Thiéry, especially regarding the interpretation of perspective: […] [The] memory of images of spatial perception (be they in the original or in effective images) that remain on the threshold of consciousness. These can remain effective even in cases in

which the drawing doesn’t create any conscious awareness of perception, but still retains an artistic perspective of the motif, whether or not it is particularly representational. What is meant by the above observation will be clarified in the following explanations. For now it should suffice to define them as a simple compilation of lines or angles, which can at the very least be understood spatially as an act of will 108 (fig. 29). Images that contain elements of perspective should awaken conscious memories and thereby trigger these much as they would in normal spatial vision. With this theory of perspective existing within memories, he had discovered an explanation for Zöllner’s illusion. The so-called Loeb illusion* supplied the necessary comparative review procedure to apply his theory to the geometric-optical Zöllner illusion. This is due to the influence of the then current studies published by Gerard-heyman on parallelism in the Zöllner and the Müller-Lyer illusions that dealt with, among other things, the loeb illusion.

Fig. 28a Wilhelm Filehne: Variations of the Zöllner’s illusion

Fig. 28b Wilhelm Filehne: Variations of the Zöllner’s illusion

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* The physician Jacques Loeb, who studied with the physiologists Friedrich Goltz and Adolf Fick, will later become known as one of the pioneers of the Berlin Gestalt Theory along with Christian von Ehrenfels.

Fig. 28c Wilhelm Filehne: Variations of the Zöllner’s illusion

Fig. 28d Wilhelm Filehne: Variations of the Zöllner’s illusion

Fig. 29 Wilhelm Filehne: Zöllner’s illusion depicted with scenography

Hermann Helmholtz and the New Physiological Optics in the Nineteenth Century

In 1867, the physician and physicist hermann helmholtz published his principal work Handbuch der physiologischen Optik (handbook of Physiological optics) that comprised more than 800 pages. It was the ninth volume in a series titled Allgemeine Enzyklopädie der Physik (General Encyclopedia of Physics). In this tome he presented a one-of-akind compendium on the current state of research on optics and perception in the mid–nineteenth century. Beyond that, this volume gave increased insight into his own work that was very rich in ideas on research in optics and perception. helmholtz had grappled intensively with the ideas expounded by the British researcher Thomas Young and had thus further elaborated on his reflections on optics. helmholtz used the term physiological optics that Young had coined in his own writings and research. It was precisely this research into optical illusions as they might relate to the new optical devices that helmholtz considered to be urgently needed in order to better describe seeing (the phenomenon of visually perceiving the world around) in order to better describe his theory of cognition. In his handbook, he concentrated on the appearance of irradiation, which he declared was connected to perceptual illusions. This phenomenon is created by connecting light and dark surfaces. The bright, strongly illuminated fields appear to be much larger than the dark surfaces, which are adjacent to them (fig. 30). here helmholtz was referring to the earlier experiments by Plateau with his checkerboard depictions. In addition to the light and dark surfaces, he worked with a variety of glass lenses and observed the differences that occurred with concave and convex lenses. Even if irradiation is not directly connected to the phenomenon of apparent motion, the observation of this illusion is viewed in conjunction with the perception of apparent surfaces, apparent volume and apparent motion. In terms of a definition for the emergence of irradiation, helmholtz specified three possible criteria: 1. The illusion of proportion – the light surfaces appeared larger, 2. The apparent coalescence of the light surfaces that lay in close proximity to each other and 3. The apparent severance of straight lines 109 (fig. 31).

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* At that time, one already knew that these fragmented images had an interesting effect in paintings. Especially in those of the Dutch artists such as Jan Vermeer (1632–1675), we frequently find these circles of confusion in the form of patches of light. In the nineteenth century, this painting technique had become increasingly important in pointillism. ** Alfred Wilhelm Volkmann was Professor of physiology in Halle, Germany. His younger sister Clara was married to Gustav Theodor Fechner, the founder of psychophysics. Volkmann commented on his string experiments on irradiation in his 1863 publication and suggested that he was not completely in accord with Helmholtz’s explanation. Helmholtz arrived at the conclusion that Volkmann could calculate the width of the scattered images on the retina based on the width of the space between the two strings.

At first helmholtz used the term irradiation solely to designate completely illuminated surfaces that appeared to be larger than they actually were. he also indicated a possible other use for this term. This was, for the interesting phenomenon called the circle of confusion.110/* During this period of time, the only observation that was made when regarding these forms of irradiation was that solely the lighter part appeared to be larger than the darker surface. helmholtz mentioned the experiment of the physiologist Alfred Wilhelm Volkmann 111/** who was able to refute the current observations with his string experiments. Volkmann asked test persons to attach black strings to a light background and white strings to a black background. The white and black strings were of the same thickness. The test persons were supposed to connect the strings so that the distance between each one equaled the width of the string itself. With each experiment the distance between the strings was consistently increased to be wider than the width of the string, regardless of whether a light or dark background was used.112 Years later, in his remarks on the Müller-lyer-and Zöllner illusions, the psychologist Adolf Stöhr called attention to the fact that vertical lines always appear longer than the horizontal ones, even when they are exactly the same length. The reason for this was that the photoreceptors of the eye are not as closely knit in the horizontal as in the vertical.113

Fig. 30 Optical proportion of adjoining light and dark surfaces

Fig. 31 Optical proportion of adjoining light and dark surfaces

Helmholtz’s Experiments on Visual Sensations

The rotating disk can be included among the standard features of nineteenth century experimental laboratories (fig. 32 a-c). As a young physician and modern physicist, helmholtz conducted an entire series of experiments with rotating disks for his optical images. Among these were also his experiments on the perception of irradiation and the measurement of light with a white disk and two black spots that turned into a grey circle when moved rapidly 114 (fig. 33). helmholtz’s interest focused on the color changes that occurred when the disk was rotated. In this case he created a link to the earlier experiments completed by Fechner with socalled subjective colors. helmholtz used the rotating disks primarily in his experiments for his new theory of visual sensations as well as for measuring the duration of light perception (fig. 34). The rotating disks proved to be a very helpful instrument in observing how the intensity of color fades. helmholtz tested and repeated many optical experiments that his predecessors had already performed using rotating disks. Examples are Purkinje’s experiment with lichtschattenfiguren (light-shadow-figures) or Fechner’s experiment with subjective colors. he observed rotating flickering disks under colored light with colored segments of a circle. helmholtz tested Talbot’s and Plateau’s experiments and amended them with his own studies. For example, he placed a convex glass lens between the eye and the rotating disc in order to prevent compensation. If the pupil is located in the furthest focal point of the lens so that the image that the lens casts on the disk falls on the surface of the pupil, the light from the brighter sections is cast evenly over the entire visual field viewed through the lens. on the other hand, if the lens is brought closer to the disk, the eye perceives the white and black segments more or less sharply as long as the disk remains stationary. once the disk is set in motion, the brightness level remains constant whether it is the eye or the disk that is brought closer. hence we can deduce that the eye is affected identically whether it is exposed to either intermittent or to a continuously equal amount of light.115 later, between 1920 and 1925, the experimental psychologist Vittorio Benussi and his first assistant cesare Musatti conducted very similar ex-

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periments with disks in Padua, Italy. These had circles painted on the flat disks and at the correct rotation speed apparent motion became visible. Friedrich Schumann recorded the contraction and expansion of images on the surface as gestalt perception at the beginning of the twentieth century.116

Fig. 32a Device used to rotate disks at the end of the 19th century

Fig. 32b Device used to rotate disks around 1910

Fig. 32c Photo of rotating disks at the psychology institute, Harvard University, circa 1893

Fig. 33 Rotating disks with two black spots

Fig. 34 Rotating disks with a certain array of circular sections

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* In 1838, Fechner had published his theory on the subjectivity of colors in the Annalen der Physik und Chemie which was edited by Poggendorff.

Ernst Brücke: The Advantage of Intermittent Retina Stimuli

Ernst Brücke, a college friend of helmholtz, taught physiology in Vienna at the same time as helmholtz published his Handbuch der physiologischen Optik. Prominent students such as Sigmund Freud, Ernst Mach and physiologist Sigmund Exner were among the audience. In his multi-faceted work, the topic of retinal stimulation was a central theme. In an article in the Wiener Sitzungsberichte dated 1864117, he outlined his results on the useful effect of intermittent retina stimulation. he based his research on the Talbot-Plateau law as well as on Fechner’s psychophysics and on the optical experiments on the retina completed by helmholtz. It is possible that Brücke’s remarks on the subject were the reason why shortly afterward Ernst Mach began to conduct more intense experimental research on the retina.118 Brücke and other researchers such as Volkmann and Mach welcomed Fechner’s introduction of mathematics into experimental psychology with his teaching on psychophysics. It therefore seems comprehensible that Brücke used Fechner’s formula on the intensity of sensations.* It stated, “that by rotating the disk, the effect of the stimulus was increased”.119 Talbot and Plateau had already formulated this theory in the following way: that the effective size of a regularly applied intermittent retina stimulus was identical to that of a continuous and constant retinal stimulus for which the identical retinal area, the identical amount of light are used in the identical way in order for it to completely disappear.120 Talbot had already explained his principle of photometry and Plateau was able to prove Talbot’s principle by demonstrating that a rotating disk with black and white sectors and a disk with cut out sectors appeared to have the same amount of lucidity. Brücke used rotating disks that were painted in equal amounts of black and white for his own experiments on retinal stimulus (fig. 35, 36). he explained his observations as follows: one selects a turntable on which black and white has been applied equally but in varying circles in a varying number of sectors. And one does it in such a manner that the number alterations increase from the center and away from the periphery. If one turns such a disk slowly enough so one can differentiate be-

tween the black and white lines on the inner rings, and yet fast enough to make the outer rings appear to be an even grey, then one will notice that between the two, one or two things are visible in neither black nor white, nor evenly gray, but rather more or less colored and flickering. When one rotates the disk even faster, the image moves forward towards the center. That is to say that the outermost of the flickering rings turns a consistent grey and the following ring which had been an alternating black and white, shows colors and flickers instead. When one rotates it more slowly, the image is moved toward the periphery in an analogous way. If one were to look at a single, individual ring while gradually turning the disk faster and faster, one can see how the flickering begins, first in violet and yellow, and with increasing speed, the violet turns lighter, and when one turns even faster, it turns light blue and the yellow turns orange […].”121 The emergence of subjective colors by alternating black and white on rotating disks had already been known for some time, and Fechner had described it in detail years earlier. Brücke’s goal was to observe the disparity of light perception at varying rotation speeds. In all of these experiments, he placed great emphasis on a detailed description of the varying scales of brightness. In the end he summarized the results of his observations on the measurement of light effects per second in the formula x=nqc/60.* Brücke was of the opinion that the number of application points needed to be increased in order for the stimulus to reach its most effective point. helmholtz was able to achieve an increase in the number of application points in an experiment in which he used convex glass lenses, Brücke noticed an additional element: There was something that influenced perception during the observation of the rotating disk and that element was time. he separated all of the collected stimuli on the retina from which light sensitivity could be deduced into primary and secondary states of stimulus. Brücke defined all of the stimuli that appeared at the beginning of the application of stimuli as primary states of stimulus; he included those that occurred when the light stimulus stopped or at least clearly decreased as secondary. Brücke discovered, for example, that the appearance of monochromatic red on a disk was to be considered a primary effect. over time, the sensation would decrease. The eye would tire due to the color red. he divided these secondary conditions or symptoms into positive equal-colored, into positive complementary-colored, and into negative complementary-colored groups. Brücke understood the division into positive and negative in the same sense as in photography.122

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* In which n = the rotations per minute and q= the number of white fields on the ring; c gave Brücke the value of 5.76 which should express the relationship of the movement from the (run) of the apparatus. The radius of disk used was 18 cm.

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In his resumé he wrote that with these images, or afterimage experiments, the effect of a given amount of light could be increased in that the light source is periodically interrupted. The interruption increased the stimulus but the constant flickering would impair and could even permanently damage vision.

Fig. 35 Ernst Brücke: rotating disk divided up into sections

Fig. 36 Ernst Brücke: rotating disk divided up into sections

Josef Czermak: Thoughts on Speed during Motional Illusions

The physiologist Josef czermak began to focus on the theory of motional illusions in 1857. To czermak’s demise, he then had to leave the University of Graz, Austria, to hold a professorship at the University of Krakow, Poland.123 he felt that the move was more of a hindrance than beneficial in connection with his experimental research in the field of speed. czermak had noticed that the concept of speed had barely been considered in physiological studies.124 he consequently pursued the objective of demonstrating the difference between motion perception and the sense of motion with respect to speed in four differing experiments. What should be proved first was: “how fast and how slow the speed of movement in a room can be in order to even be perceived as such.”125 Second, he gave examples of the observation of differences in speed that occur between two movements in order to be conscious of the difference. In the third series of experiments, he questioned specifically whether “the speed of an observed movement could be subjectively increased or decreased by changing the convergence angle of the axis of the eyes.”126 And finally, with the help of the fourth experiment in the series, how speed manifests when we see or feel it. or, in czermak’s own words, “[…] when we perceive it on the area of the retina or the skin, it has various degrees of sensitivity of the sense of space.”127 his interesting approach later gave Sigmund Exner and also Ernst Mach considerable food for thought concerning the relationship of perception to space and movement for their experiments in the realm of motional illusion and the perception of motion.

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* Ernst Mach’s handwritten course catalogue, starting summer semester 1860, can also be found in the Ernst and Ludwig Mach’s partial estate at the Philosophical Archive at the University of Constance. ** Gustav Theodor Fechner, who had many interests, summed up the results of his studies on psychology in his famous book entitled Elemente der Psychophysik (1860). He ascertained that in most cases the ratio between sensations (y) and stimulus (x) can be expressed with the following formula: y = p log. (x/q), whereby p and q are experiential constants.

The Influence of Psychophysics on Mach’s Experiments

During his studies, the physicist Ernst Mach attended lectures held by Ernst Brücke and carl ludwig on physiology. As Mach himself stated, the fact that he turned towards physiology after he had completed his studies in physics was for economic reasons: instead of conducting research in a laboratory and purchasing expensive equipment, he could have “his own” body be the subject of his research.128 The decision to concentrate on the world of sensory perception would prove to be fruitful for Mach’s career and for the world. his first Viennese lectures in 1860 dealt with the question of sensory perception such as Über Änderung des Tones und der Farben durch Bewegung (on the Alteration of Sound and color through Movement). A year later, his lectures were on Physik für Medizin (Physics for Medicine) and Höhere physiologische Physik (higher Physiological Physics).* In January of 1861, Mach submitted his contribution on psychophysics129 to the Wiener Sitzungsberichte for publication. During that same month, he wrote his first letter to Gustav Theodor Fechner. In that letter Mach thanked Fechner for his depiction of psychophysics, which in turn was the scientific basis for his deliberations in connection with physics and physiology.** During the winter semester of 1864/1865, Mach gave a one hour lecture on Fechner’s Elements of Psychophysics at the University of Graz, Austria. In 1865, his lecture Bemerkungen zur Lehre von sinnlichem Sehen (comments on the Teachings of Sensualized Vision) followed.130 In his earlier contribution on psychophysics in 1861, Mach attempted to prove that the multitude of measurements given in Fechner’s law could also be used on the perception of tension experienced by the ocular muscle. It was not Mach’s intention to test the perception of complicated designs by examining it. his focus was primarily on the perception of simple, straight lines. he assumed that there must be something characteristic about the differing positions of straight lines that the human eye could recognize that trigger the senses and lead back to the differentiated perception on which movement of the eye would follow the individual points of the line: “through the eye only those depictions are perceived as sharp and clear which fall on a specific point of the retina. Should a larger picture be perceived clearly, the separate sections needed to pass by this point of clear vision in succession” 131 (fig. 37a). This movement, in turn,

depended upon the degree of tension of the eye muscles. The formula which was derived from Fechner’s law and which he applied to his experiments, he made on the condition that they should be understood arithmetically, and therefore it would be difficult to combine the various stimuli into one clearly formulated theory. In order to conduct his tests he returned to, among other things, the black rotating disks which were marked and separated into circles. Extending from the center was a taut white thread that moved along with the rotation. he positioned two identical apparatuses adjacent to one another, so that, from his vantage point, he could observe the center of both of the disks. he positioned the thread on a disk and simultaneously tried to also position the second thread on the second apparatus in exactly the same way (fig. 37b). After each trial he measured the various positions of the threads, or rather, he determined the deviation with the aid of the so-called method of determining the central error – “that one repeatedly aspires to make one stimulus equal to that of another and then determine the central error that had been made.”132 At the time there were two mathematical treatises on the highly disputed ocular movement theory: one by the mathematician and physiologist Adolf Fick and the other from the physiologist Georg Meissner. For Mach the theory on ocular movement had not been fully formulated: First, it is just like Fick as well as Meissner’s work showed – not known around which axis the eye is actually turning while the optical axis makes a specific movement. Second, even if the rotating axis were known, determining a corresponding muscle tension is unpredictable because the eye has six torques where three would already suffice (fig. 38). Fick’s assumption that the movement takes place with a minimum amount of effort is probably true, but this has not been proven.133 Georg Meissner, Adolf Fick and hermann helmholtz considered themselves to be representatives of a new theory on ocular motion from which helmholtz wanted to deduce a logical explanation for upright vision or rather, for the inverted image on the retina. The studies by physiologist Erwald hering (1863) and later by Vincenz Dvorak (1870) followed Mach’s first critical comments on the ocular movement theory. In 1870, Dvorak was able to refute the ocular movement theory for vision while standing upright at the University of Prague based on Mach’s prompting.134/*

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* For his trials Dvorak used several archimedic spirals that he had rotate on disks similar to Plateaus experiments. This was in order to determine that the perception of the process of motion could not be explained through eye-movement but was contingent upon the retina.

Fig. 37a Ernst Mach: broken curve, the position of a viewed line, 1860

Fig. 37b Ernst Mach: rotating disk mounted on a board, 1860

Fig. 38 Apparatus to explain the movement of the eyes, circa 1850–55

Mach’s Series of Experiments on Light Stimulus on the Retina

After the physiologist Brücke had published his research results on the effect of intermittent retina stimulus, Mach began his series of experiments on light stimuli on the retina. His noteworthy results were combined in four publications that appeared in the Wiener Sitzungsberichte between 1865 and 1868. In the introduction of his first essay “Über die Wirkung der räumlichen Vertheilung des Lichtreizes auf die Netzhaut” (1865)135 (On the Physiological Effect of the Spatial Distribution of the Light Stimuli), he describes a serendipitous observation. This occurred during his experiments with black and white rotating disks that ultimately led him to formulate a general rule on physiological optics. Mach set the disks into rapid rotation, from which the following image ensued: One particular disk that had a bright area in the center became darker around the edges. When the disk was black in the center and the lighter sections were mostly at the edges, the center of the disk appeared darker and the outer area lighter. “The appearance of the lighter rings must astonish everyone who might attempt to explain them theoretically.”136 He set up a coordinate system to show the changes in brightness in which x represented the radius of the disk and y the intensity of light on the rotating disk. Then he also used a rotating cylinder with black and white sections in various shapes and discovered that everywhere that the light curve has a kink, the spot grows lighter or darker than the surrounding area. The spot is lighter when the kink is concave against the abscissa axis and darker when the kink is convex against the abscissa axis 137 (fig. 39a-c). Mach was thereby able to demonstrate that this phenomenon was independent of rotating disks and the intermittent light idea. It could occur everywhere that corresponding light conditions existed. He was the first to describe, to some extent, the principle of the phenomenon that would later be known as the Mach-Bänder (Mach bands) (fig. 40). Mach demonstrated a progressive research approach with the application of the relatively new method of imagery known as photography 138/* for his experiments. He used photography not only for the purpose of documentation but also to verify his theory.139/** The disks he used were similar to those used by Helmholtz and Brücke in their studies on intermit-

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* Mach’s numerous experiments are documented alongside his many publications through the new technological medium of photography. Over 900 pictures can be found in his estate which is located in the Deutsches Museum in Munich. More photos and albums (from the Prague Institute) are at the not yet overworked (original) partial estate at the University of Constance, German.

** On the usefulness of photography Mach published his teachings separately. He can be counted as one of the first scientists who consistently kept track of his trials through photography in order to allow a more objective view of moving sequences in his experiments. For the aforementioned trials he photographed a plethora of rotating disks with various depictions. He was convinced that the photo paper reflected the same as the retina according to the TalbotPlateau Law.

Fig. 39a Method of measuring brightness with rotating disks according to the Talbot-Plateau law using an x and y-axis

Fig. 39b Ernst Mach: disk to measure brightness, photograph is taken during rotation, 1865

Fig. 39c Ernst Mach: Light curve during contrast phenomenon, 1865

Fig. 40 Ernst Mach: rotating disk used for the phenomenon of Mach bands, 1865

tent light stimuli. One of these was divided into six rings that were painted on in a black and white ratio to the power of two. What this meant was that the innermost ring showed one, the next one showed two, the next one four black segments and so forth, until the outermost ring had 32 black segments. He then made the disk rotate at a speed of thirty rotations per second. The disk appeared to be a uniform grey.140 In order to test the influence of light, he used a disk on which three rings were imposed; the outer one was half black, the second a quarter black, and the third one was an eighth black. The center remained white. This disk was photographed during rotation and revealed three unevenly bright circles. The rings were cut out of these photographs and glued further toward the center, adjacent to the middle. Upon rotating, the rings all appeared equally bright 141/* (fig. 41a-b). Mach was thus able to prove that even illusions were bound by certain natural laws: “Why should the sensory organs not also have a certain logic?”142 was a theoretical presumption that would become the basis of the algorithmic construction of apparent motion. Mach often criticized the general manner of thinking and speaking about reality and illusion. In his most popular work, Analyse der Empfindungen (Analysis of Sensations), he gave the following example: we see a pencil which we hold in front of us in the air as straight; when the same is dipped into water at an angle, we see it with a kink. In the last case one says: The pencil appears bent although it is straight in reality. What right do we have to explain the fact of reality to someone and to disparage the other to be an illusion? In both cases there are facts, which represent differing conditions and differing types of correlation of the elements. The pencil submerged in water appears optically to be bent due to its surroundings, haptically and metrically it is straight.143 This way of seeing things through the existence of the discernible objects leads directly to the influence the epistemological idealist Irishman George Berkeley had on Mach. Many other natural scientists such as Helmholtz or the Viennese neuro-anatomist Theodor Meynert were also highly fascinated by Berkeley’s thoughts and ideas.144 At that time he was already convinced, that we are able to think in order to be able to conceive of the ideality of the world. In his second treatise “Über den physiologischen Effect räumlich vertheilter Lichtreize” (On the Physiological Effect of the Spatial Distribution of the Light Stimuli) 145, he invited the reader to read the retina as a surface

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* The Mach bands had an impact on artists such as Paul Klee and Mark Rothko. They were used by some American minimalist artists such as Jo Baer for example.

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on which “each and every spot is a light-intensive proportionate y-coordinate”146 should be applied. If the points of all the coordinates were linked, one would have an objective light-intensive surface, henceforth referred to as luminous surface. In the next step a coordinate should be pinpointed on every spot of the retina for which the exact location of the corresponding proportional light sensitivity is located. The light surface as well as the sensory surface would be differentiated inasmuch as one of them would reflect a distorted image to the other. The other surface that is created as a result of the connection of these coordinates might be described as the subjective light intensity surface or sensory surface. The luminous surface and the sensory surface differ in that one conveys a distorted image of the other. According to Mach, the relationship of these two surfaces might be determined in terms of physiology. Based on Fechner’s Law, Mach derived a formula that allowed him to calculate two curves: one for the luminous surface – the light curve, and the other for the sensory surface – the sensory curve.147 Mach assumed that this composite light which shines on the retina could not be calculated in mathematical terms but required instead a physiological value.148 Besides the mathematical calculations, Mach described various experiments using rotating disks. For example, in one experiment a black/white colored disk was set into rotation while a second disk that had varying sections placed in front of it, which had random notches. The observer was supposed to look from the second disk B to the first disk A. In order to avoid the interference of so-called wheel spoke curves, Mach replaced the painted disk A with a photograph. To double-check his text, Mach placed two transparent rotating glass surfaces over one another and photographed them. This variation gave Mach the advantage of conducting a series of experiments to determine the light intensity when the two “bands” or disks crossed (fig. 42a-b). In his third discourse in “Über die physiologische Wirkung räumlich vertheilter Lichtreize” (On the Physiological Effect of Spatial Distribution of the Light Stimulus)149, Mach described his attempt to “examine more closely the relationship of the form and lighting technique of a uniform surface with that of a lighting surface of its perspective image and the associated perceptive surface.”150 The graphic monocular effect of the rotating disk gave Mach an idea: to place a binocular device with rotating cylinders under the stereoscope. He used a large optical mirror and discovered

Fig. 41a Ernst Mach: Mach-Bands, 1865

Fig. 41b Ernst Mach: Mach-Bands, 1865

Fig. 42a Ernst Mach: Experiments on light intensity, 1866

Fig. 42b Ernst Mach: Experiments on light intensity, 1866

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* This principle will be addressed about 100 years later by the artist Alfons Schilling in his experimental work and used in an artistic way for his seeing apparatus.

that the eye sees the object in the mirror just as the reflection of the eye would see the actual object, except that the reflection is not congruent with but rather symmetrical to the object in relation to the reflection plane. This suffices for orientation. Now, if I move the angle-mirror closer to my face, just as the diagram shows, in which l is for the left eye and r for the right eye, then I see two images of my face. These are quite different in terms of perspective than they ever could be in actuality for the stationary eye (fig. 43). If I cover both images by fixating the right image with the right eye and the left one with the left eye, I get the impression of a physical object that isn’t immediately very striking. When looking at it for a longer period of time then, second by second, a relief becomes more distinct: the eyebrows appear to stand out beyond the eyes, the nose appears to be as long as a shoe, the mustache appears to protrude from the lips like a fountainhead, the teeth seem to protrude far beyond the lips, etc. In actuality, the two perspective images in the mirror correspond to the distance of the eye from the mirror l, r or by the unchanged distance, the eye is from a body of much greater relief.151/* Not only the amount of time required in order to arrive at the perception of a relief was of interest to Mach but also the endless possibilities of distortion that resulted from the variation in the distance from eye. Mach had two plaster casts made of the same mold and put them adjacent to one another. When he looked at one of them with the right eye and the other with the left eye, “the stereoscopic impression was very nice.”152 Other pseudoscopic experiments, such as observing the ground outside, were only possible to accomplish with a great deal of effort. As a result he concluded that: since I’ve seen animals that have had their brains removed show certain mannerisms, which they have obviously acquired as a result of their way of life, I don’t doubt that the eye can identify a [kind of habitual (translator)] experience and certain mannerisms to which it reacts 153 (fig. 44). While in later experiments with inverting mirrors – from George M. Stratton to Ivo Kohler- the theory is championed that the retinal image could possibly be inverted, the most recent studies generally adhere to Mach’s notion that the human being adapts his sense of orientation relatively quickly when he experiences his surroundings reversed or distorted for a longer period of time. In another example in which the pitches of rooftops and duplicate edges occur, Mach uses a simple sketch and describes as follows:

Fig. 43 Ernst Mach: Construction sketch for an angle mirror, 1866

Fig. 44 Ernst Mach: Sketch of pseudoscoptic experiments, 1866

Fig. 45 Ernst Mach: Optical illusions of pitched roofs, 1866

Fig. 46 Ernst Mach: Sketch of the act of observing oneself, circa 1885

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* Later, though, Mach used his left eye (retina) in his well-known selfinspection of the ego (fig. 46). In a footnote Mach attributed the drawing to the writings of Chr. Fr. [sic] Krause. The author of this work had asked for comprehensible solutions for the selfperception of the ego (Ernst Mach, Analyse der Empfindungen, 16). It is possible that Mach resorted to using the Johannes Müller 1837 model for his sketch. In his Handbuch zur Physiologie, in the chapter „Bilder des eigenen Körpers im Sehfelde“ a description of the drawing that Mach had made at a much later date: „certain parts of our bodies are almost always included in our visual field as well as in our mental image. When we look at something with only one eye, only one side of our nose is within our field of vision. When we move the eyebrows down, they occupy only the top part of our visual field. When we raise our cheek, we see a portion of it in the lower part of our field of vision. And, when the outer part of the musculus orbicularis palpebrarum contracts, the outer part of the field of vision is limited by a silhouette created by the surroundings of the eye. Images of parts of our body can therefore appear in the entire periphery of our

I imagine looking down from the edge of a rooftop that extends downwards. When I imagine myself standing under the roof that same edge projects inward. A certain amount of effort is necessary to imagine the roof, and this is all the more complex the more complicated the drawing is. In the previously mentioned pseudoscopic landscape I have first viewed the rooftops as convex, then later as concave. I can only think in terms of a depth sensation that is triggered by perspective154 (fig. 45). In addition to his experiments on vision with both eyes, Mach felt that “looking at physical objects with only one eye to be instructive”155 and useful. In a simple experiment: the image from the preceding experiment is constructed out of stiff sheets of paper as a three-dimensional object. Here the raised vertical side should be facing the observer. The light should enter from the left so that the right sides appear to be darker. When one eye is closed, it was possible to see the figure as concave with a little additional effort. The left side then appears to be brighter. But it isn’t only the brightness of the three-dimensional paper figure that changes. It is also the proportions, which appear different: the edges between bf and bd appear longer than ae and ac. The lines cd and ef appear shorter than ab. The edge ab ultimately no longer appeared to be vertical but was more like a book lying opened in front of the observer.156 Even Mach was surprised at […] how fast these things [which simultaneously change the depth, form and light perception (author)] are adjusted by well functioning reflexes. At the same time, one sensation, which seems to trigger another, can do just the opposite to the same degree.157 Thus the sensation that was initiated by one event is decreased to the same degree that it was increased. Mach presented his insightful observations on binocular optics in his paper “Wozu hat der Mensch zwei Augen?” (Why has Man Two Eyes?) dated 1866 in Graz, Austria. Later it was published in his Populärwissenschaftlichen Vorlesungen (Popular Science Lectures).158 In his lecture Mach expounded extensively on the perception of perspective as a cultural imprint and appropriation. According to his memory, he had perceived, as a child, every perspective drawing as a distorted image. For him the non-perspective depictions of the old Egyptians served as a paradigm for objective vision with two eyes.159/*

In his fourth and last treatise “Über die physiologische Wirkung räumlich Vertheilter Lichtreize” (On the Physiological Effect of Spatial Distribution of the Light Stimulus) dated 1868, on the topic of contrast phenomena or influence phenomena with rotating disks or cylinders, Mach went into more detail on Fechner’s basic psychological law. A dispute had flared up among the scientists as to which scientific discipline might claim Fechner’s law. Adolf Fick was of the opinion that it was a physiological law; Wundt, on the other hand, considered it to be psychological. Between these two positions, Mach was convinced that the law was organic in nature, in the sense of organization: the psychophysical law does not apply to the relationship between stimulation and nerve impulses in a simple nerve. It applies to the relationship of the first stimulus to the last nerve impulse, which accompanies conscious perception. That is because the stimulus in the sensory organ is filtered through a complex web of nerves.160 Because of this filtering process could be explained by Fechner’s Law as being organic-physical or also as an organic-psychological law. Mach’s observations about the eye made a point here: even when the relationship of light intensity changed, we would still be able to recognize the same object. This organization of the light intensity relationship consisted of psychological and physical regulators such as the muscles of the iris, the retina and the surface of the pupil opening. Mach began with the premise that other regulators were also present to calculate the light intensity of an image. Subsequently, his interest was focused on observing the proportions of stimulus and arousal. To this end he provided the following example: “if one lays a white square abcd on a black base that has no borders, it has a certain degree of contrasting brightness. If one then cuts out square efgh and lays it next to iklm, the overall brightness of the field of vision remains the same. However, the brightness of the white increases” 161 (fig. 47). These phenomena also occur with other color contrasts. In order for that to happen Mach experimented with a disk that had cutout and was covered with either black or white paper. A colored base could be observed through the cutouts on the rotating base 162 (fig. 48). Based on his observations Mach finally concluded that perception “was a myriad of organically concentrated individual forces with which one could, for example, imagine the retina to be more dynamic and autonomous than what one might generally think.”163

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field of vision between the images of our body parts are the images of the objects beyond. When we stare at the tip of our nose by looking at it with one eye, the image of nose remains within the field of vision from one side to the middle. When we look with both eyes and fixate the tip of the nose, the image of the tip of the nose remains in the middle of the lower part of the field of vision. The nose can be seen by both eyes, while the images on the side of the nose get partially lost inasmuch as the eye only sees outer objects instead. While the other eye has an unclear image of the nose. When the eye looks downward, not only the nose but also the cheeks and lips appear in the lower part of the field of vision as well as on the torso and the extremities of the body. With each position of the eye it sees a part of our body and the image of parts of our body become an integral part of most of facial perceptions and facial concept. Although the images of our body are only seen within the visual field of our retina and from there presented to the sensorium. They accompany the images of outer objects with the same degree of certainty. Strictly speaking, the image of our hand, the one we actually see, is not the

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hand itself but only its illusion. We reach for something and in doing so, the same thing occurs within the image of visual field of the retina. We see that we are reaching inasmuch as the illusion of our hand takes on the illusion of the object.“ Quotation excerpted from Johannes Müller, Handbuch der Physiologie des Menschen für Vorlesungen, vol. 2, section 1. (Koblenz, 1837), 356–357. Karl Clausberg used this text from Müller’s “Handbook” as the prologue of his book. Karl Clausberg, Neuronale Kunstgeschichte, Selbstdarstellung als Gestaltungsprinzip (Wien, New York, 1999). To this day this uniform drawing continues to gives impetus to artists. The image of a computer assisted distorted Mach drawing is used for the cover of an Ars Electronica catalogue. The artist Peter Weibel, as editor of the catalogue Die Welt von Innen, Endo und Nano (1992) points out the historical development of the biological-mathematical psychophysics up to endophysics (Otto Rössler 1976).

Fig. 47 Ernst Mach: Sketch on the perception of different proportions, 1868

Fig. 48 Ernst Mach: Experiment on observation on a colored base, 1868

Mach’s Experiments on Sensation of Movement and Afterimages of Movement

To date, not much attention has been paid to the sensation of movement in the research of visual perception; perhaps not because the topic seems too insignificant but rather because it is difficult “to study the basic forms of sensation of movement under controlled conditions.”164 Furthermore, there is also the predominant opinion that the sensation of movement is a complex exception within the field of perception research.* At the beginning of the eighteenth century, the Irish philosopher George Berkeley commented as follows: “the observation of movement greatly tormented the spirits of the old philosophers to the degree that tortuous, even absurd opinions evolved that do not deserve further attention.”165/** Ernst Mach added his own personal experience with incidental perceptual experiences on the voluminous topic of the sensation of movement: he was able to explain the skewed positions of houses and trees while a train rounds a curve with rapid acceleration but was unable to describe the physiological sensation. Mach had become convinced that with all sensations of movement the overall impression was not purely optical. This gave him the impetus to study these special illusions more closely.166 concerning the topic of the sensations of movements, the extensively discussed topic of afterimages of movement became a relevant topic about which to do experimental studies. Plateau and oppel were of the opinion that afterimages of movement were related to processes in the retina. But the topic of sensations of afterimages of movement had led to a variety of theories since the Plateau spiral and the anti-rheoscope, which oppel had introduced in 1856 such as the theory of eye-movement, which has already been addressed. helmholtz’s assertion that the “illusion [or afterimages of movement (author)] does not occur when there is rigid fixation”167, was corrected by a simple experiment conducted by Mach’s assistant Vincent Dvorak: a large white disk with a spiral was superimposed on a smaller disk with a counter-rotating disk, upon which a third disk was placed that rotated in the same direction as the first large disk. The common center of all of the disks was a small black disk upon which several black threads were stretched. While the disk is being rotated, the center can be fixated acutely so that the rim of the light afterimage at the center and the black threads reveal every movement and fluctuation of the eye position immediately. If one then sees a white lined umbrella, then a

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* Researchers such as James J. Gibson and Ivo Kohler and later also David Marr and Richard L. Gregory did not share this viewpoint and devoted their research to the sensation of movement as it had existed in the nineteenth century.

** Berkeley is often understood to be Mach’s predecessor as well as that of the Wiener Kreis. However, Berkeley’s ideas on epistemology were always theologically based. This is to say that every analysis of movement was ultimately always based on God. Mach, on the other hand, wanted to free the entire science from metaphysical ballast and strove for a unified scientific understanding.

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dark afterimage of the disk appears, divided into three partially shrinking, partially swelling rings. And within this afterimage, very tight and quiet, are the bright afterimages of the center with the threads. It should be noted that the apparent motion in the afterimage only catches weaker dots and spots and never clear dots and lines. These afterimages of optical movement are also of the same type of localized manifestations on the retina as light- and color-afterimages and occur as such when in staid fixation.168 Mach was especially interested in Plateau’s experiments on the movement of afterimages in reference to his own studies on the sensations of movement. Both physicists were in continuous written contact and exchanged information with each other.169 Plateau, among other things, had shared with Mach that he had come to the conclusion that the observation of the senses during passive movements would also fall under the law that they had posited. however, Mach didn’t share this point of view: in his book on sensations of motion dated 1875, he stated that he believed to have disproven Plateau’s law which Plateau had believed to be a general law that was also valid for the observed perception of passive movements.170 Mach worked out a formula that he had observed on moving humans and animals, whereby he could generalize the phenomena. he had developed a special rotary device for this purpose. During his experiments, the device was constantly adapted and it was essentially just a rotating wooden frame with a chair (fig. 49). The test person who sat down on the chair could be moved from a vertical sitting position into a horizontal reclining position. In order to avoid dizziness, the test person – often Mach himself – was enclosed in a sort of paper box. In this rotating box there was a black cross on a white background. In contrast to helmholtz, Mach was able to determine that the feeling of dizziness could by no means be eliminated when the paper box was rotated and the cross simultaneously remained visually anchored.171 When the paper carton was then quickly opened, the test person was under the impression that the room that was visible for him and its entire contents was turning. As if the Sehraum (visible room) were turning within a second room: it appears as though the visible room were rotating within a second room which one believes to be stationary, although the latter is not visibly distinctive in any significant way. one would like to think that behind the visible room there is a second room to which the first is always relating. This fact is of fundamental importance and one has to experience it oneself.172

Mach’s description of this phenomenon or special perception can be defined by the term polytopic.173/ *

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Mach conducted many rotation experiments with animals such as doves or rabbits. his results proved that his own experiences were very similar to those shown in animal behavior. For instance when he turned the dove clockwise, the dove began to move counterclockwise. Jean P. Flourens, Albrecht Graefe, Johann czermak and Josef Breuer had conducted such experiments with animals before. Breuer was able to prove analogous behavior caused by the dizziness brought on by rotation in birds and from birds that had their vestibular organ, their semi-circular canals, surgically removed.

* The term polytopic (many roomed, many placed) is used by Peter Weibel when referring to the new directions in art of the twentieth century. In the visual arts of the twentieth century, from painting (cubism) to and including film, video and computer art, this term becomes increasingly relevant.

The results of Breuer’s studies, like the Breuer description on nystagmic movement, served as a useful reference point for Mach’s own experiments. It would only seem natural to presume that every movement of an image on the retina, which does not result from a conscious eye-movement, is interpreted as being a movement of the object in the room. […] even images that remain on the retina [can (author)] appear to be moving. […] the visual space remains in relation to the second room which we construct based on our sensations of movement.174 In Grundlinien der Lehre von den Bewegungsempfindungen (Fundamentals of the Theory of Movement Perception), Mach presented three experiments on the phenomenon of apparent motion.

Fig. 49 Ernst Mach: model of a revolving chair used in trials on the sensation of motion, 1874/75

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* This contraption could be understood to be one of the earliest formal forerunners of multi-medial headsets like the one created by Ivan Sutherland at the University of Utah in 1966–68.

** The Gestalt psychologist Karl Duncker addressed this subject from 1927–1929 in detail with the term induced movement.

*** Later, in the twentieth century, the principle of the Mach Drum was used in the study of motion sickness in space travel.

Studies in Movement: The Mach Drum

Mach assumed that optical perception associated with perception of movement could be changed. contrary to this, the perception of movement could be triggered by optical processes. In order to prove this, Mach constructed an instrument-based device that was similar to an enormous helmet and was placed over the head of the test person. To construct this device he used a horizontal wooden cylinder that was 1.5 meters in diameter and placed it on a vertical axis. on the inner edge of the wooden cylinder there was a strip of paper half a meter wide with vertical lines running from top to bottom.* The subject (test person) would sit on the inside of a lined, hollow, revolvable cylinder. When the drum was rotated for a few minutes, they thought that the objects, which the drum didn’t cover, were turning in the opposite direction. Soon they were under the impression that they were at rest again even while the drum was still turning. These two subjective conditions frequently alternated. Upon repeating this experiment several times, it appeared to me that the part of the field of vision that was not stationary would be easiest to set in motion […] At least I couldn’t seem to resist a feeling of motion. As is well known, in the most varied form one can observe these sorts of experiences when on a bridge looking down on flowing water. or, for example, while on a stopped train and seeing several moving ones nearby. The field of vision appears divided into several parts as a result of varying movements 175 (fig. 50). Mach developed variations of this rotation device in order to expose both humans and animals to rotating movements. of all of these rotation devices described, the Mach Drum version is the best known and has gone down in the history of perception research. With the help of the Mach Drum the test person could perceive so-called induced movement.176/** The drum created an apparent motion of a sedentary object by the movement of other objects. As a further experiment, a paper drum, as previously described, was placed over the head of the subject and this person was placed in the rotation device. A third experiment combined the rotation of the two devices*** (fig. 51). At the time that Mach conducted his experiments, the primary organ for the perception of motion was not yet known. There were a variety of pre-

sumptions on the subject. For example, that perception of connective tissue and bones, skin, muscles, blood pressure, eyes emanated from the brain or from a separate organ in the head. Mach had carefully tested all of these ideas and had found the plausible theory that the principle organ for the perception of movement must lay within the labyrinth of the ear. When compared with other senses, Mach had determined that the sensation of movement, the phenomenon that “disassembled into elements, that we, inasmuch as they are connected with body processes and through these are contingent upon them, is called sensations.”177 Mach had recognized that the complete assessment of sensory perception also required an intellectual interpretation. he therefore postulated that the perception of the senses could only evolve through feeling (sensation) and reason.178 George Berkeley’s statement: “being is being perceived or perceiving”179/ * must have influenced Mach in his reflections on the subject. For his analysis of the senses, Mach classified the elements involved into three groups: ABC was for the everyday objects such as a house or a table, KLM consisted of elements that relate to the human body such as hair, eye color etc. and group αβγ was comprised of the elements connected with memories or emotions. A sense of connection could not occur until all of the elements coincided.180 With this concept Mach anticipated the paradigm of the later modern Berlin Gestalt theory (Wertheimer, Köhler) according to which perceptions originate solely through the organization of sensory experiences. As Plateau and oppel before him, Mach was convinced that the movement of afterimages was dependent upon designated processes within the retina. he vehemently opposed helmholtz’s idea that movement of the eye was essential during this process as well as another axiom held true during this period by helmholtz which claimed that when a point is strictly fixated, movement of afterimages do not appear.181 Thanks to Mach’s student Vincent Dvorak, who supported Mach’s deliberations with experiments, which he conducted in 1870 in his Prague laboratory, his theories became increasingly important. Dvorak repeated Plateau’s experiments with the rotating disk within the framework of a series of experiments. It was here that he discovered a further relevant component that was responsible for the appearance of afterimages: the intensity of light. When he quickly and repeatedly changed the light intensity in a room he was able to produce an afterimage.

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* esse est percipi (aut percipere) is Berkeley’s principle theorem and already describes perception as a construed reality.

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Dvorak’s new insights into afterimages as they related to light intensity or rather light differences confirms Mach’s well-known experiment with the Mach bands or Mach rings (1865).182 Although Mach’s pivotal question was on the optical sensation of movement of objects in a room, he realized that the objects could be created by light variations. The attention that was paid to the contrasts would contribute significantly to the aesthetic design of abstract painting in the twentieth century. 183

Fig. 50 Sketch for Ernst Mach’s drum

Fig. 51 Optokinetic Drum (according to the Mach-Drum 1875), circa 1969

Sigmund Exner: Explorations into Kinesthetics, Sensation of Movement and Apparent Motion

One used to imagine the way in which one might arrive at the impression of how an object moves as follows: The object appears (to us) at the moment t and at the location α, at moment tl, at the location α1, and t2 at α2 and so forth. When we recognized this, we were able to say that the object was moving or as one expressed it, we deduced movement. This conception is correct, to a certain degree. It is correct for the impression that certain movements make on us, but not right for other movements of which we took impressions. We also refer to those as impressions of movement.184 Exner (1888) The physiologist Sigmund Exner was Ernst Wilhelm Brücke’s student in Vienna.* he spent a year in heidelberg with hermann helmholtz. It was there that he began conducting experiments on the amount of time required of impressions on visual field. Exner adapted two devices he had found in helmholtz’s laboratory for this purpose: an electromagnetic rotation machine, which could possibly regulate the rotational speed (fig. 52) and a device to interrupt the light impressions. The rotation device was connected to the second device so that they could be set in motion. The second device consisted of two circular disks whose centers were aligned (fig. 53). A small object was fastened to the second device, which was alternatingly visible and not visible to the viewer. The object to be observed could be enlarged with lenses. With the help of timer the period of time that the object was visible or covered could be precisely recorded. By linking the two devices it became possible to illustrate the chronological sequence of the retinal stimulation on a curve (fig. 54). Although Exner had not completed his doctoral degree, he published the final results of his experiments in the 1868 edition of Wiener Sitzungsberichte.185 As a result, he became distinguished early on, and for this reason Exner would obviously turn his focus to the study of visual perception in his subsequent physiological research.

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* After his habilitation treatise (1871), Exner became Brücke’s assistant. It is said that Sigmund Freud, who was also a student of Brücke’s, wished for nothing more than this position as an assistant, but he then had a falling out with Brücke. In later years, Freud strongly denied this fall-out. In 1891 Exner followed in Brücke’s footsteps and became tenured Professor and Member of the Board of the Physiology Institute in Vienna. One of his students was the author of Geschlecht und Charakter, Otto Weininger.

Fig. 52 Sigmund Exner: depiction of a rotating machine and device for intermittent light impressions used for visual experiments, 1868

Fig. 53 Sigmund Exner: circular disk mechanism for devices used in experiments on vision, 1868

Fig. 54 Sigmund Exner: chronological sequence of vision, 1868

Two Sparks and One Apparent Motion

As adjunct Professor and assistant at the physiological Institute in Vienna, Exner between 1873 and 1875 published four treatises on the topic of “Experimental Studies of Simple Mental Processes” in Pflüger’s Archiv für die gesammte Physiologie des Menschen und der Thiere (Pflüger’s Archive for a comprehensive Physiology of Mankind and of Animals). In his fourth essay, he explained his experiments on determining the sensation of a time difference between two sensory impressions. As it turned out, within the center and the periphery of the retina the eye reacts irregularly in relation to perception.186 The experiments took place in a darkened room in which, with the help of helmholtz’s rotation device, a horizontal disk was placed into steady rotation. on the underneath side of the disk two needle-shaped metal pieces or metal pointers were attached. When the disk was turned, the tips of the metal pieces came into regular contact with a cone of mercury. These, and the tips of the metal pointers, were connected to an electric battery, which generated a spark, that was essential for the observation. The observation distance of the eyes was placed at 640mm. Exner wrote the following on the subject: While, in the case of a shorter distance from the eye, I can see each and every spark at its origin; when the distance is greater, I have the impression of a movement. I still see every spark at its origin but between the sparks, I see a movement as if the first spark were jumping over to the second one. […] A movement, […] even when none has taken place. So that one has to say that the eye (sit venia verbo) has a tendency to interpret such successive impressions as movement.187 The metal pointers could be easily shifted so that the time lapse between the jumping sparks could be changed. Instead of producing an apparent motion with two sparks, Exner used a tin cylinder with two horizontal little holes with a diameter of 3.3mm and a distance of 10.7mm. As a light source there was a gas flame inside the cylinder. later he exchanged the two holes with a vertical slit. A vertical disk rotated in front of the cylinder or its openings. With this device, Exner also observed apparent motion on the rotating disk.188 After Exner concentrated on the center of the retina in order to produce a stimulus

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* Exner pointed out his treatise entitled “Einfachste psychische Processe III” in Pflüger’s Archive dated 1875 which had appeared shortly before and in which his deliberations were presented in a fragmented sketch.

** In 1857 Exner had published a treatise in Pflüger’s Archive and posited his theory therein. He wanted to publish the proof in the Wiener Sitzungsberichte.

with the spark, he also studied the periphery of the retina for local sensations of movement.189 he was able to supply the proof with a study that dealt with seeing movement and he presented the results on July 15th 1875 at the Viennese Academy of Sciences for a publication in the Wiener Sitzungsberichte.190/* Exner profited from these studies on apparent motion by becoming highly recognized among experts in the field and this served as a reference for many experiments on vision and motion that followed. The focal point of his study was the quest for a plausible explanation of peripheral vision of the retina, which he initially tried to explain based on the compound eye. over the course of his research, Exner became convinced that apparent motion played an essential role in “that the perceptual function of a movement was based on actual or direct sensation and not, as was previously believed, on an actual sensation.191/** Exner’s most eminent study on seeing movement was released the same year as Ernst Mach’s Lehre zu den Grundlinien der Bewegungsempfindungen (Fundamentals of the Theory of Movement Perception). As Exner does not refer to this work in any way, one can assume that when he wrote his study he had no prior knowledge of Mach’s study. In fact, he expressly emphasized that no one besides the physiologist Karl Vierordt 192 had dealt with the subject.193 however, one should note that Vierordt clearly mentions Mach’s research in his own introduction. Exner on the other hand highlighted the experiments of Mach’s assistant. With the help of spiral disks, Dvorak had produced sensations of motion in afterimages and in so doing attempted to disprove the theory of eyemovements. All of his life, Exner had often expressed his discontent with the imprecise terminology that existed in the field of perception theory. he therefore tried to first define the terms perception and sensation with the help of deliberations on the minute- and second-hands of a clock. The idea behind this experiment is based on czermak. Exner put a black disk with a circumference marked in white into rotation. The rotational speed was equal to the minute hand of a clock. The movement gradually became recognizable to the degree in which the white marker line slowly changed its position. When the rotation speed was increased, there was a moment in which, for the observer, a movement seemed to become apparent, while during the earlier slower rotation; the movement could only have been inferred. According to Exner’s definition, the impression of the slow movement should be classified with perceptions, whereas, during the fast

movements, a pure sensation of movement occurred. Exner subsequently assigned these sensations of movement to all other possible motional illusions. his theory therefore stated that all experiments with stroboscopic disks were not only motional illusions but also actual sensations of movement. Exner had come to believe that the “most primitive features of our eyes”194 existed explicitly to see movement. This concept of motion is already given by Aristotle to a certain degree. he had considered light as a form of movement originating from an illuminated object; the actual ocular perception therefore took place solely through the movement of the illuminated object.195 Based on the observation of animals, which recognize their prey solely through their movements, react and can ultimately hunt successfully, Exner was able to conceptualize the idea that vision with the type of eyes that humans and higher animals have is necessary in order to recognize movement. This idea prompted him to study the function of the compound eye in order to answer the question of for what the vision of form and movement is useful. When light falls on a single area, and then on another and another, the ray of light (from a candle, for example) has to be absorbed as a very intense sensation of movement by the compound eye. The intensity is, of course, dependent upon the number of nerve endings stimulated by light.196 In addition, the compound eye can orient itself in two ways: once by the localization of movement and then by the intensity of perception. The more facets that exist, the better the localization. With the help of a strong refractor, a so-called crystal cone located behind the cornea, the reduction of the intensity of perception is prevented. Exner compared the compound eye with a sort of light capacitator, an instrument that is similar to what he had on his microscope to illuminate the object being magnified (fig. 55). A topic that really seemed to interest Exner was whether seeing with the compound eye resulted in a image on the retina as was known to occur with the vertebrate eye. Repeating an earlier experiment with a fly (musca vomitans) that Johann christoph Gottsched had conducted remained unsuccessful. only when the experiment was repeated on a water-scavenger beetle (hydrophilus piceus) did Exner presume a socalled compound picture.

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In his experiment with the compound eye, Exner placed a 2-inch wide convex lense in a room in such a way that he could see the window frame through the lens. he placed a pencil in an upright position eight inches in front of the lens. If the viewer’s eye was about one foot behind the lens, then they would see both the window and the pencil rather clearly. With the help of a translucent umbrella, Exner then took a photo of the window. The image of the pencil is completely missing. When I place the umbrella 2 to 3 inches farther away from the lens, I can see an image of the pencil and from the window, the image all I can see is only a washed out blotch of light.197 Exner assumed that the retinal images of the compound eye, if such a thing really existed, must be on different planes. he eventually came to the conclusion that the compound eye could not produce a comparable image to the human retinal image because of its anatomy and optical requirements. Due to the numerous ommatidia there was a heightened degree of sensation, which came from the light condensers. Just the light from the candle flame sufficed to stimulate so many nerve endings than would ever have been possible with the human eye. For Exner, the compound eye seemed to be the key in the “function of the eye as the organ which detects movement.”198 It was not necessarily optimal for planar or spatial photographs of the external world. The compound eye, consisting of many individual eyes, was really ideal for detecting movement. The layout of the compound eye as a semi-circular (hemispherical) shape allowed for a 360-degree field of vision. The object under observation is recognized simultaneously by a whole group of eyes, and that is why each alteration of the position of the pictorial object is registered by the change in sensation of the entire group of eyes. Exner compared the function of the compound eye with the reaction of the peripheral region of the human retina in terms of sensation of movement. With the help of a simple example, Exner was able to prove the physiological sensitivity of the peripheral region of the retina: In this respect one can make the apparently absurd observation that, for example, a group of bright spots on a dark surface are pushed sufficiently far on the periphery of the field of vision, doesn’t come close to recognizing their actual number: but as soon as one such spot is added to the existing ones, or one disappears from the group an active impression occurs – one might be inclined to say that ‘something moved’ within the field of vision.199 Since the study “Über das Sehen von Bewegungen” (on Seeing Movement) had not yet gone to print and was not intended to be published until 1876,

Fig. 55 Sigmund Exner: Sketch of a compound eye

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Exner published his fourth treatise on the subject of psychological processes in Pflüger’s Archive 200. here he went into detail on the topic of afterimages and the precise location of the sensory area of eye. he experimented with rotating disks that he divided up into black and white sections and that are reminiscent of the earlier experiments conducted by Plateau. In using these disks plus the stereoscope, Exner was convinced that both eyes share one sensory area and it could be proven that “it can be distinguished by the interaction that takes place at that location between each area of an eye with the identical area and in close proximity of the other eye.201 In 1887, in the essay “Einige Beobachtungen über Bewegungsnachbilder” (Some observations on Motion Aftereffects), Exner described the use of a star-shaped device that consisted of thirty knitting needles that formed a wheel: […] the peripheral end of each needle was 21 cm from the center, and all the needles were on a single plane like the spokes of a wheel. They were of course also positioned at the same distance from one another (12º) […] The wheel was put into motion, so that it completed eight revolutions in one minute. I sat down in such a way that the level of the spokes fell directly at my median level, and placed a mark which is perpendicularly above the rotating axis, about halfway up the spokes. The mark is placed in such a way that they strike each other hard with each revolution. I would then get so close that the tips of the needles almost touched my nose and then sealed off all openings with screens except for that part of the needle which came towards me; […] If I stared at it for one to two minutes and then suddenly stopped the wheel, it undoubtedly appeared to be moving backwards.202 Within his very complex and wide scope of studies, Exner continued to study kinetic and optical sensory movement in order to pinpoint the boundary between perception and sensation: “Sensation is what we call those impressions on our senses, inasmuch as our bodies consciously register them (especially our nervous system) as large external objects”.203 In his primary work which appeared in 1894 Entwurf zu einer physiologischen Erklärung der psychischen Erscheinungen (Sketch of a Physiological Explanation of Psychological Phenomena) Exner formulated the following: “I named sensations that particular set of stimuli that may reach our conscious awareness but that cannot be subdivided; I called perception that unified set of stimuli that conscious awareness is able to subdivide”.204 here Exner refers to Ernst Mach’s extremely popular

theories of that time of sensation complexes. Mach was of the opinion that: it is not the body that creates sensations, but rather a complexity of elements (a complexity of sensations) that generate the body. If the physicist considers the body to be, that which is permanent and real, while the “elements” are its ethereal appearance, then he does not take into account that all “bodies” are only symbols of thoughts for elemental complexes (sensation complexes).205 Exner considered pure sensation to be the primary process, and perception as the secondary. A pure sensation could in no way be defined. This led him to conclude that: “since sensation is always primary and perception always secondary, the focus and precision of the latter is dependent on the focus and the precision of the former.”206 helmholtz had drawn on an example from music in order to conceptualize the divergence of perception and sensation: we could consider the sound of a violin as pure perception, but as soon as the sound is broken up into partial tones, it becomes a matter of pure sensation.207 Based on this example, however, a very essential problem arises of determining an unambiguous terminology. Many if not most people cannot aurally distinguish the partial tones of a violin. Exner was once again opposed to the arbitrary use of scientific terms, which led to vague wording of indistinct terminology. he considered this conceptual confusion to be the greatest hindrance to “modern sensory physiology and brain physiology” that were already problematical because they “had to work with a nomenclature and system drawn from an entirely different science.”208 In 1896, Exner published his interesting treatise “Über autokinetische Empfindungen” (on Autokinetic Sensations).209 he described the appearance of subjective sensations of motion occurring in darkened rooms. he was motivated by his friend hermann Aubert’s previous research which addressed these kinds of illusions and who had published an article in 1887 on the sensations of motion. In addition to describing his own experiments, Exner also compiled a retrospective of this phenomenon: For example, in 1799 Alexander von humboldt had described low-lying stars and their fluctuating movement. Within the framework of his study in 1858 “Über das Sternschwanken” (on the oscillation of Stars), Gottfried Schweizer, the Director of the Astronomical observatory in Moscow, had declared humboldt’s astronomical observations to be subjective phenomena. Schweizer had created a so-called artificial star using an opaque lantern that had a narrow slit of light that was observed in a darkened

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* One can find similarities in the methodology of image production in kinetic art and also in experimental film such as expanded cinema.

room and discovered that the phenomenon could be traced back to an apparent motion. Schweizer’s experiments interested Exner because he had seen the longest duration of movement of objects to be observed to that date. Regarding this, Schweizer described, among other things, the following of his experiments: If one were to draw a black dot or an even larger patch onto a white wall, and were then to stand at a certain distance from it, so that both the dot and the patch were still clearly visible, and if one were to look at them steadfastly for a while, a strange phenomenon would indicate that the paint or patch would appear to gradually move away into various directions, yet always return to its previous point of origin […] Simultaneously with the change of location of the separate objects, these would also appear to change their shape at the edges so that the black dot in particular would give the impression of being a black insect on a white wall attempting to creep this way and that, yet always returning to its starting point.210/* In 1886, the French physiologist and neurologist Pierre-Marie-Augustin charpentier conducted very similar experiments, probably without knowing about those that Schweizer had conducted. charpentier described that an illuminated spot which one stared at for several minutes appeared to move. According to his notations, this effect already took place after a few seconds, and one experienced the impression of a mild displacement. charpentier called these types of phenomena subjective visual sensations. In his studies on sensations of motion, hermann Aubert had almost identical results and may have been the first to term these auto-kinetic sensations. According to Exner, these are a matter of associations of mental images; the imagination of the direction conveys the impression of apparent motion in the same direction of the fixed illuminated spot. Exner was convinced that solely the mental image effected, for example a balloon or even a bird hovering in the distance. What remained unresolved for him, however, was the question: “Why does movement impose itself on consciousness? Because that occurs long before a mental image arises that could be associated with the perception of a point of light.”211 With his idea Exner was probably the first to associate the significance of neuronal connections that relate thinking and consciousness to vision.

Johann Ignaz Hoppe’s Attempts at Defining Apparent Motion

Johann Ignaz hoppe was a physician and a philosopher who worked and taught in Basel, Switzerland. In 1879, he published a study Die ScheinBewegungen based on the so-called retrogressive riparian illusion.212 hoppe was convinced that his study represented the central physiological and physical explanation of apparent motion.213/* Following hoppe’s explanations, then the impression is created of apparent motion that occurs through incomplete vision 214. In this work, hoppe’s theory is of special interest because he tried to explain apparent motion by examples in the applied arts. “one of the most amazing manifestations in the field of apparent motion is the moving – or the coming to life – of a statue or painting. Those kinds of phenomena can only be intentionally achieved by being in the right frame of mind.”215 According to hoppe, an artistic portrayal would be best suited to “leave an imprint” on the retina.”** hoppe clearly distinguished between seeing and thinking. By thinking, one could arrive at a perception but not one that would produce a “photochemical image on the retina”. 216 This was in opposition to what Johannes Müller assumed, namely that thinking could at least enable a perception in the sense of “putting something into place”. hoppe was of the opinion that we would only see appearance or apparent motion unclearly or incompletely. Even when, in the process of seeing, the visualized image was mentally constructed by thinking about it, before a physiological drawing was created, a movement of the eye muscles would accompany it.217 Therefore, according to hoppe, a description, an apparent motion is simply a movement that takes place with our eye muscles in relation to the imprint point on the retina of a stationary object even though we know otherwise, we recognize it as moving and describe it as such even though this knowledge is false.218 In his study, hoppe did not refer to the research on sensations of movement by Mach nor to the experiments by Dvorak nor Exner’s results on the physiological sensations of movements and their definition of apparent motion. Instead, he had addressed a current and as yet unknown subdomain on the topic of sensory perceptions and had begun to make it a topic of discussion. The expert commentaries on the first comprehensive

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* According to the author, the hallucinatory apparent motion as well as the apparent motion of diplopia (double vision) had to be disregarded.

** Hoppe uses the term “imprint” in place of the more commonly used term “afterimage”.

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publication on apparent motion were therefore absolutely divided in their opinions.219/*

* The experimental psychologist Wilhelm Stern denotes the publication as a “relatively broadly written” book by Hoppe.

The train of thought hoppe followed and the questions that arose are quite avant-garde when considered today. he, for example, broached the issue of the discrepancy of the theoretical aspects of the process of perception or the topic of the perceptual threshold between a material and immaterial world; the latter being of great importance for the phenomena of apparent motion. George Berkeley’s theorem percipi est esse initiated hoppe’s question: If one can perceive the riparian movements of the tides, “do they therefore exist?”.220

The First Psychological Analyses of Stroboscopic Phenomena (1886)

otto Fischer drafted the first psychological study on stroboscopic phenomena in 1886.221 he elucidated on and accentuated the best-known examples available on the market at that time. These included the multitude of stroboscopic gadgets that had been invented since Plateau and Stampfer but which had not yet found any practical applications. The application of the stroboscopic images was primarily used for physiological purposes such as the representation of interference diagrams (Poppe)222, water jets (Magnus)223 or water waves (Müller)224 etc. only the Viennese physician Salomon Stricker had searched for an answer in his writings on the extent of the psychological effects of the stroboscope to date. Stricker’s theory stated that the visualization of movement was currently the most important philosophical topic ever. he described the stroboscope as “a device that would prove the association of muscle sensation with sensory perception”225. he claimed “that the representation on the stroboscope was only caused because the images passing before our eyes force us to move our eyes in the same way as they would if we focused on a little man jumping up and down”.226 Early on, Stricker had recognized the potential of the visualization of movement within modern society as was increasingly manifested at the turn of the twentieth century. his discoveries, which he also aimed to substantiate with experiments, were quickly contested. he went so far as to claim that motional illusion did not occur at all. otto Fischer succeeded in proving the contrary of Stricker’s hypothesis within the framework of his own, specially constructed stroboscope. of the two disks Fischer used, one was constructed for the movement phases of the depicted objects (picture disk) and the other one had small openings (slit disk). The picture disk was put into steady motion with the mechanical workings of a watch. The slit disk could be turned by hand and at will. In consideration of Stricker’s theory, Fisher used a disk that was smaller than the picture disk, so that one could look through n slits and see the entire circle of rings of the picture disk from a certain distance. This means seeing partially indirectly. I placed dots on the picture disk in such a way that they went up and down like a sinusoid, not like they used to as a positive and negative wave, singly, but two of each.

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When I looked at both rotating disks while I fixedly focused on the front one, I saw 2n dots that moved up and down in such a way that the two diametral dots that were across from one another moved away from the center simultaneously. Since x = 12, 24 dots moved in 24 different directions at equal angular distances from the center to the center. This contradicts Stricker’s hypothesis because had it been correct, the eyes would have had to be able move in 24 different directions simultaneously.227 Fischer not only investigated Stricker’s theory, he also performed countless experiments with dot-lines, which he placed on a disk. These, in turn, led to his own theories on concepts of motion or afterimages on the retina etc. As a result of his psychological analyses, he recognized that the short duration of the light exposure was the main reason objects appeared to move. Fischer understood the stroboscopic effect as a result of afterimages. he summarized: In order to artificially produce the movement of an object one must receive short, successive light exposure. They should be at almost identical intervals so that the eye should not be affected by any other light stimulation in the meantime.228

James McKeen Cattell: Visual Stimulation in Time

At almost the same time as otto Fischer presented his analyses on ideas of movement by stroboscopic disk, the American physiologist James McKeen cattell drafted his noted work Über die Trägheit der Netzhaut und des Sehcentrums (on the Inactivity of the Retina and the Visual center) on the perception and quick comprehension of colors and characters.229 cattell had determined that keeping accurate time records was the crucial requirement for the correct recognition of colors and characters impacting the retina. The tests occurred using both artificial and natural light. All of these experiments began in The United States and later took place in a physiological laboratory at the University of leipzig in Germany. They were performed using a device that cattell described as a Fall-Chronometer (falling chronometer). It was a variation of a tachistoscope with which the visual stimulus could be made evident for a brief period of time. What was crucial, however, was the exact recording of time (how long the object being shown was visible) (fig. 56). In this case the objects were letters or words that the test person was supposed to record visually.* latin letters or German letters and numerals were used. cattell was against the general practice of acting as a test person and investigator himself, so he used several test persons for his experiments. At the end of his series of experiments, cattell explained that he had not intended to establish new theories but rather to define the threshold of consciousness. There is not only a threshold of stimulus but also a level of stimulus beyond which an increase of stimulus strength would not exceed the intensity of perception. Analogously, there is a limit for the number of objects or for how complicated an object beyond which the consciousness can no longer register the overall impression (extent of consciousness).230 Among other factors, the length of time required for certain symbols or colors to stimulate movement within the retina cells was to be determined.

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* Based on Cattell’s psychological experiments on the perception of letters, the concept of reading schools as they exist today developed in seminars and publications.

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Fig. 56 James McKeen Catell: Falling chronometer used to measure visual stimuli, 1886

The First Monograph on the Perception of Movement

The author of the first monograph on the perception of movement, Wilhelm Stern, deliberately avoided the term seeing in the title of his comprehensive treatise “Die Wahrnehmung von Bewegungen vermittelst des Auges” (The Perception of Movement by Means of the Eye) dated 1894.231 He believed that the perception of movement would play a significant role (which means muscle sensation and not only the optical and psychological elements). His experiments were concerned with the types of perceptions of movement and their characteristics, and consequently concentrated on the perception of movement in various regions of the retina. Finally he gave his attention to motional illusion and apparent motion. Among Stern’s greatest achievements was that he was the first to give a precise description of the various types of movement as well as attempt to categorize them. He was thus able to define four (distinct) variations of apparent motion: the deceptive motion as impression of a movement even when the field of vision is objectively at rest. These took place when an object was visually fixated for a longer period of time. For example, if it began to vibrate when the field of vision was completely isolated, similar to a glowing wire in a darkened room. Changes in light intensity or differences in brightness could cause deceptive motion to occur. He described transferred movements as the objectively perceived movements of an object that could be observed either by themselves and/or be observed on another object. Transformed movements would occur when an objective movement took place but another shape appeared, among them he recorded the stroboscopic illusions that were created with devices such as the stroboscope, daedaleum, schnellseher (electro-tachoscope) or wunderkreisel whereby a kreisel could be a gyroscope, rotating disk or a spinning top.232 Among the devices was Plateau’s large black spiral that would either contract or expand evenly to all sides. According to Stern, when an actual consistent movement occurs, and then stops after a certain amount of time, there is often the impression of an after-movement. He believed this movement to possibly be the most significant form of optical moving illusion.233 Stern also attempted to be more precise in the differentiation of aftermovements. He placed the riparian illusion, the Plateau spiral, Dvorak’s and Kleiner’s experiments with three spirals on a disk or three disks like

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hoppe’s experiments on apparent motion (in which counter movement was created with the help of mirroring) into the category of diametrically opposed after-movements (oppel). Stern also experimented with so-called aligned after-movement. his results coincided with those by the German physiologist Theodor Wilhelm Engelmann: afterimages created during a train ride by quickly opening and closing the rested eye which faced the (rail-car) window. Soon an afterimage of the window-frame was generated (of the train car) in a stationary position, while the surroundings moved in the actual direction. The apparent motion became even more pronounced when the objects in the afterimage were less focused. When the direction of the train […] changed, […] the direction of the afterimage would change immediately.234 Finally, Stern mentioned an optical moving illusion, which still lacked an explanation: “when a lattice-like object is moved past the eye that is fixated elsewhere, these appear to be curved-like waves. however, when both the resting eye and the other follow a stationary object, both eyes see normally.”235 Because helmholtz had also observed the curved lines in a state of rest, Stern came to the conclusion that they must be two entirely different phenomena. In addition to categorizing various types of movement or apparent motion, Stern outlined the history of the perception of moving illusions in the nineteenth century by giving detailed descriptions of his own experiments in his monograph. Among other things, he explained how he continued the experiments conducted by Sigmund Exner on visual acuity during movement. Stern positioned a piece of backlit milk glass in a dark corridor. A black strip of paper was stretched across the surface so that two equally illuminated surfaces were discernable. By changing the width of the strip, the distance of the two bright surfaces in which the gap between them was no longer visible. Stern erected a cardboard screen with a 10 cm square opening in the center placed in front of the milk glass in order to assess the sensitivity of the movement. According to Stern, this “cutout served as a bright object. The screen could easily be moved sideways.”236 Stern was familiar with Exner’s theory that visual acuity was greater for a stationary object (as opposed to a moving one). he did not share Exner’s opinion, though, that this was a specific sensation of movement but rather, he was convinced he had actually observed an irra-

diation (the apparent extension of the edges of an illuminated object seen against a dark background). Stern conducted a variety of experiments on afterimages. he repeated and varied Engelmann’s and oppel’s investigations with the help of lined paper placed over the drum of two kymographs.* The series of experiments took place in a darkened room in which only the drums were illuminated. The movement was observable through a square opening which allowed the eye to see only the vertical lines passing by. 237 Stern attributed the perception of movement that occurred to visual as well as to muscle sensations created by – as he emphatically stated – several circumstances of sensation or even by just a single one: “that this is possible, that a sensory perception, without comparison to others, can already possess the character of movement, […] is proved by almost all illusions of movement.”238 The term sensation of movement itself seemed ambiguous to him. It became clear to him that Ernst Mach had described completely different sensations than he had. “namely those produced through the movement of one’s own body […] and because of this deficiency, one would have to differentiate between personal internal movement sensations and external sensations of movement.”239 And further: If one were to understand by the term ‘sensation of movement’ a sensation of movement of a set of familiar sensations which had the ability to directly indicate a particular movement, this would be acceptable because the name would have the same meaning as in the expressons ‘depth of sensation’, sensation of smoothness, which one encounters here and there.240 As long as one considers the sensation of movement to be completely elementary or not analyzable or place it on the level of color- or sound-sensations, the term remains vague and problematical. And it can only aid in the “labeling of an outside movement” in the direct interpretation of “certain sensations or complex sensations of the eyes” these might lead to a direct meaning of “characteristics of an external movement. “241

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* The kymograph is an instrument used in the natural sciences for recording variations in pressure. Around 1840 the physiologist Carl Ludwig had already constructed a kymograph with rollers to measure blood pressure.

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* According to the editorial staff, the article had already been received by October 31, 1901. ** Several variations of the kymograph existed; the one here was similar to the original one developed by Carl Ludwig.

Alfred Borschke and Leo Hescheles: Movement Afterimages and Speed of Movement

In 1902, a short article on afterimages of movement appeared which Alfred Borschke and leo hescheles of the Physiological Institute of the University of Vienna composed.242/ * Years of research on the topic of light and color sensation had preceded the article. The two authors were aware of the complexity of problems associated with the incomplete verifiability in the area of optical sensations. That is why they wanted their study to be understood as a sort of interim report. The objective was to arrive at the most precise description of the phenomenon as well as the speed of the afterimage. like Mach, Exner or Stern before them, Borschke and hescheles used the drum of a kymograph ** for their experiments. Their theoretical viewpoint based on the opinion of their teacher Sigmund Exner, that during a stroboscopic, simulated movement just such moving afterimages would arise. They also used Exner’s system of lines for their studies, which they modified slightly. Blackened knitting needles were ideal for the vertical and horizontal rods having a diameter of 1.5 mm and placed 1.5 mm apart on a matte white background. Aided by an electric motor and a cover for the system of crossed lines, the knitting needles were moved independently of each other. The regulation of the direction in which the needles were being moved was variable and possibly both vertical and horizontal. The device was illuminated from the sides by light bulbs. The screen cover had a circular opening of 5 cm and was used for observing the rodand line-systems. on the lid of the opening there were also horizontal and vertical lines to facilitate the observation of afterimages. Depending on the retinal impression, there was an apparent displacement of the grid of squares. “one could see both systems of rods in the act of moving, or a system being in a kind of ‘competition of the visual field’, a system of moving rods while the other system of rods more or less withdrew and was no longer discernable.”243 In order to determine the speed of the afterimage, four different interesting aspects had to be scrutinized: whether the speed of the afterimage was influenced by the speed of the original image, by the number and clarity of the rods, by the clarity of the original image or also by the length of time that a movement was observed. In terms of the first aspect, a certain proportional relationship of

the speed between the original image and the afterimage was proven. When the number of rods was reduced, the direction of movement of the afterimage appeared larger than when there were more rods that were closer together. That “the speed of the afterimage is influenced by the clarity of the original image”244, was also determined and it was shown that the speed of movement was also crucial for the direction of the afterimage. With regard to the duration of observation of a movement, Borschke and Hescheles came to the conclusion that after a very short period of time afterimages were already identifiable. First they set the period of time at 30 seconds, then they reduced the time by half and finally they conducted the trials with an observation time of 3 to 4 seconds.245 The transition of the afterimage from its subsidence to a complete state of rest could not be clearly defined, regardless of whether the afterimage of the grid of rods had actually passed by or not. Borschke’s and Heschele’s very specialized study on the speed of the afterimage was followed by a series of projects that had similar and expanded studies within the field of experimental sciences at the turn of the twentieth century.*

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* The debate about the afterimage in art primarily accelerated in the area of kinetic and technological arts. Influences can also be seen in psychedelic literature. The American poet and pioneer in media-art Gerd Stern (born 1928 in Saarbrücken, Germany) who was a founding member of the influential art association USCO (US Company) called his second volume of poems Afterimage (1965).

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* In 2004, during a congress on perceptual psychology in Budapest, the well-known Scottish perception researcher Nicholas Wade brought Szily’s achievements to light again.

Adolf Szily’s Experimental Analysis: Moving Afterimage and Contrasts of Movement

In 1905, the Hungarian physician Adolf Szily published a study on the observations of the movement of afterimages and moving contrasts in the periodical for psychology and physiology.246 After Szily died, some of his essays on perceptual research were printed posthumously but his research was very quickly completely forgotten.* At the beginning of his treatise, Szily summarized the status quo of the research on moving afterimages by Purkinje, Müller, Plateau, Helmholtz, Brücke and up to Exner and Stern. Ernst Mach’s observations of light and sensory stimuli of movement were not mentioned, although Mach, in his more recent edition of Analyse der Empfindungen (The Analysis of Sensations), had referred to Szily’s studies. Szily, like Mach before him, had observed contrasting lines with the help of rotating cylinders. With his study Szily could prove that the after-movement “constituted the basic phenomena of the senses of the organ of sight.”247 The physiological aspect of apparent motion, as Exner had demonstrated, was supposed to be worked through more concisely with his own experiments to show new perspectives on the subject. The preliminary work conducted by Exner in the field constituted the substantial basis for Szily’s research. The phenomenon of contrasts of movement as well as the Zöllner pattern of stripes is what Szily used to expand on his pronouncements. The previous observations on the effects of movement (impressions) were separated into two groups: naturally or artificially created effects of movement (impressions) in apparent motion.248 Based on the multitude of differing concepts of after-movement, Szily deduced four fundamental formulas that were intended to clarify the phenomenon of apparent motion.249 Szily included Zöllner’s essay on the striped pattern among the ideas on pseudoscopic movement. He also included the studies conducted by Ernst Budde (1884) twenty-four years later, which further explained similar psychological hypotheses. Szily shared Budde’s views that while looking indirectly at the movement of the fixed mark and the moving object, these jump back and forth, while their relationship to one another is constantly being adjusted. After each

one of these jumps, for which a certain amount of time is required, a change in the relationship is noted.250 Budde described these observations as meta-kinetic adjustments or meta-kinetic apparent motion. Unconscious eye-movements can produce a second concept of motion. Szily named Purkinje and helmholtz as well as Stricker as prominent representatives of this theory, which claimed that all concepts of motion were based on muscular sensation. he classified the third concept of motion as that which occurs as a result of the time that the subsidence of stimulus to the retina occurs. Johannes Müller and later Wilhelm Stern had described this in their publications. Szily categorized the pure physiological motion afterimage as examined by Plateau, oppel, Dvorak and Zehfuss251 but especially by Exner as well as the research-duo Borschke and hescheles, into a fourth category. Szily referred to Exner’s discourse on optical sensation of movement several times and deliberated upon them in his own instrument-based designs such as the kymograph drum.

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Szily’s Instrument Based Observations

Szily implemented radiating and spiral disks as well as parallel line systems for his experiments. Aided by a rotating disk, he could more readily locate the fixed point for the eye than with the lined kymograph drum or oppel’s anti-rheoscope. Additionally, the disk was to be rotated at the slowest possible speed in order to evoke impressions of movement. To this end, he constructed a device, which could be turned by hand (fig. 57). Szily was convinced that experiments with “a glance at a system of sketched lines on a stationary board” were constructive in this context.252 Reliable guidelines for the construction, formally clear and spatially arranged contours and, last but not least, the ability to repeat the generation of the afterimage should provide meaningful results on apparent motion or on afterimage contrasting movement (fig. 58 and 59). hence he built several variations of Zöllner’s familiar pattern by changing the angle of the lines. he also conducted a variety of experiments in contrasting movement using varying background colors. he aimed to have differing intensities of the afterimage movement, or rather, the apparent motion in his experiments.

Fig. 57 Adolf Szily: Device to observe the impression of movement, 1904

Fig. 58 Adolf Szily: Zöllner’s pattern with the impression of movement, 1904

Fig. 59 Adolf Szily: Circular system with a square to observe apparent motion, 1904

Fig. 60 Adolf Basler: Device to test the speed of moving afterimages, with a kymographic drum, 1908

Fig. 61 Adolf Basler: Detail of a kymographic drum, 1908

Adolf Basler: Memoranda on the Process of Movements of Afterimages

Basler used a device he constructed himself for his series of experiments on seeing movements253 in which moving afterimages were artificially generated. When a complicated construction of rods was set into motion, a simple striped pattern became visible when viewed through a small cutout similar to a picture (fig. 60, 61). Additionally, the test person was supposed to trace the apparent after-movement by hand with the help of a gadget mounted on the device. Basler himself appeared to be surprised by the precondition he had created, in which the movement that was seen could be read back simultaneously. The test persons were also supposed to estimate the speed. In most cases, the speed was perceived to be faster than it actually was. The Viennese physiologist Ernst Fleischl-Marxow (1883) had already noted this misconception in his optical studies: The movement was always gauged faster than it objectively was.254 With his experiments Basler verified theories already existing in this field. Studies by oppel255 (1858), Zehfuss (1880),256 Budde (1884),257 hoppe (1894),258 Borschke and hescheles (1902) as well as those of cords and Brücke (1907)259 served as fundamental references on moving afterimages for him. As others had before him, particularly Plateau, Basler had determined that the ability to observe moving afterimages was not of the same intensity with every test person. In his search for an explanation for this phenomenon, he categorized the existing explanations in psychological and physiological terms. Representatives of physiology such as Zöllner and Budde were not satisfied with purely psychological viewpoints. however, even among physiologists, the opinions on the dependency of observing moving afterimages diverged greatly from sufficient blood supply such as Johann Georg Zehfuss to “the individual elements of afterimages [created (author)] moving in the same direction as the original movement disappeared in the same order as they originally had appeared (Johannes Müller).260 Wilhelm Wundt and Wilhelm Stern had come to similar conclusions. Basler based his research primarily on that of Sigmund Exner and searched for explanations within the field of physiological optics. he cited the following example:

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if one fixates, for example, a shape painted in any color whatsoever and looks at it on a neutral background, one sees the same shape emerge in its complementary color. The longer we regard the first color, the longer and more saturated the complementary color becomes. continuing with this comparison, with the moving afterimage, the velocity is more or less similar to the color saturation: the longer one regards a moving object, the faster the afterimage appears to move, and the longer the sensation endures.261 Basler’s research had one single goal: to verify the simultaneous contrasts in the sensation of movement. Even after several experiments, the required proof that should have been provided still could not furnish a flawless explanation for these phenomena.

Vittorio Benussi: From Apparent Motion to Apparent Corporeality

When Benussi attended Alexius Meinong’s philosophy lecture during the winter semester 1899/1900 and changed his major from Italian and German Philology to Philosophy, he spent most of his time in the experimental lab which Meinong had established in Graz, Austria, in 1894 (the first of its kind at the time of the Imperial and Royal monarchy). For Benussi the cooperative work with his teacher, but particularly Franz Brentano’s writings and christian von Ehrenfels’ ideas proved to be pivotal. Von Ehrenfels having studied with Meinong, was called to the Prague University and would become one of the most distinguished protagonists and pioneers of Gestalt psychology. his work Über Gestaltqualitäten (on Gestalt Qualities), dated 1890, can be considered to be the basis of the Graz School and later for the Berlin School of Gestalt, in particular. The theory of Gestalt psychology can be traced back to Plato, Aristotle and lao-Tse. All three of these philosophers put more emphasis on the whole rather than the sum of its parts. contrary to the associative theoreticians (Wundt) with their elemental psychology and focus on the analysis of the individual components, Gestalt theoreticians made the entirety, the wholeness, the structure of perception, feeling and action the central point of their focus. The founder of the Graz School, Meinong, differentiated between a higher and lower order, basing his ideas on von Ehrenfels’ theory. The latter operated with the core concept of Vorstellungsproduktion or imagery production and became known as Produktionstheorie or production theory. This notion differentiates between elemental imagination and that which the subject/observer cognitively produces. Essential contributions for the theoretical phrasing of the Graz Gestalt theory came from Rudolf Ameseder (1904) and Stefan Witasek (1908). Benussi dealt more with the actual empirical experimental aspects of the theory. Benussi submitted his dissertation Über die Zöllnersche Figur. Eine experimental-psychologische Untersuchung (on the Zöllner illusion. An Experimental-Psychological Study) in 1901. More than nine thousand experiments had been conducted to prove the Zöllner illusion, and by the time he had completed his dissertation, the number had increased to 14,000 individual observations, which he had organized and summarized

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* As Benussi emphasized, in this essay he summarized his arguments on the abstract concept of gestalt ambiguity and the concepts of extrasensory provenance, for – as he emphasized – the younger colleagues, not lastly because of the criticism made of his own theories by the younger representatives of the new Berlin Gestalt School. ** In addition to his studies on geometric illusions, Benussi also experimented with chromatic apparent chromaticity.

in charts and diagrams. His hard work did not remain unnoticed: he garnered great appeal and Meinong in particular would have wanted him to be his assistant. This wish was not to be granted officially, and Benussi remained at the status of lab assistant until he was discharged in 1918 after the end of the war. His habilitation treatise dated 1905 was “Psychologie des Gestalterfassens” (Psychology of Understanding Gestalt) and was related to the Müller-Lyer illusion. His first studies on the perception of time were published between 1907 and 1909. All of his test results were published in the comprehensive publication Psychologie der Zeitauffassung (Psychology of the Notion of Time), which was also the first monograph on the perception of time. Benussi’s Gestalt theory was based on two primary principles: the principle of Gestalt ambiguity and of the difference between sensory and extrasensory provenance that are either dependent upon peripheral stimuli or independent of them.262/* Accordingly, the produced association consisted of a constant act of association plus the variable content of associations, which together made up the fundamental psychological components of Gestalt perception. Benussi wanted to recognize a third component as well: that of the object of the association. By 1905, he had already begun to abandon the previously used terminology elementary and production associations that Meinong and Ameseder had introduced. He preferred the expression inadequate associations for all of the geometric-optical illusions**. Just as Filehne had before him, Benussi rejected the term illusion because, in the field of Gestalt theory, it remained ambiguous and had negative connotations. Vorstellungsinadäquatheit (the inadequacy of imagination) on the other hand was more of a didactic term that could be divided into sensory and extra-sensory provenances 263. The mere notion of a curve, a so-called quasi-convexity of an imaginary line that was actually straight, produced an inadequate association. At the beginning of his 1911 study “Über die Motive der Scheinkörperlichkeit bei umkehrbaren Zeichnungen” (On the Motifs of Apparent Corporeality in Invertible Drawings) 264 Benussi describes the problem surrounding the illusive physicality based on a drawing of a cube. “We generally focus our eyes on whatever is closer, our eyes stare at it, and from this fixated position some kind of eye-movement is made.”265 Benussi clearly completely avoided mentioning any impression of perspective. According to him, terminology such as apparent physicalness,

apparent matter or apparent corporeality was significant because something material could always be produced from an illusion. He tried to clarify whether the apparent corporeality was based on the completion of the actual portrayal by association and in which the apparent corporeality related to the duration of exposure to the image shown (fig. 62). In that same year – 1911 – Heinrich Hanselmann of the University of Zurich wrote his dissertation “Über optische Bewegungswahrnehmung“ (On Optical Perception of Movement).266 The young researcher echoed the existing theories on the observations of motion. For this, he drew on a research approach that connects and characterizes the diffraction phenomenon with the status of observation. He divided the phenomena of apparent motion into two categories. In the first he included objects that appear on the retina due to physical conditions such as lattice phenomena, wheel spoke phenomena and/or a combination of these. As examples he cited the experiments of Roget, Plateau, Faraday, Aimé, Emsmann, Kurz, Fischer and Reuß. The second category of apparent motion that he also defined by means of a host of examples, Hanselmann designated the socalled subjective facial phenomena267 as described in Jan Purkinje’s and Johannes Müller’s268 earlier writings and experiments. Hanselmann addressed mainly those phenomena that could also be categorized as entoptic perceptions and that up to that point had only barely been studied. Besides this classification of apparent motion, Hanselmann also summarized the phenomena of movement into three diverse observation criteria: whether the entire body was in passive or active motion, whether only the head was moving or whether the apparent motion was dependent upon involuntary or arbitrary eye-movement. In the addendum to his observations, Hanselmann also briefly delved into the very popular displays of apparent motion that could be generated by stroboscope and cinematography.269 He stressed that the stroboscope had been recognized as a very useful device for physical imagery and had not, as had so often been claimed before Otto Fischer’s analyses, simply used as toy.270

Fig. 62 Adolf Basler: Summary of results

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* When Vittorio Benussi published his study on apparent motion in 1912, the concept of the electric television already existed as a basic idea. The engineer Ernst Ruhmer showcased his first electric television in front of an expert audience on June 26, 1909. (fig. 63) Through electric transmittance 25 picture elements (Pixels) were greatly enlarged by a projection device from the focusing screen of the transmitters onto the screen of the receiver. During this demonstration of image transfer, or electric apparent motion, pictures were transferred from one place (sender) to another (receiver) with the help of electricity. It was not the direct production of apparent images that stood in the fore but rather to exemplify the location independency of images.

Stroboscopic Apparent Motion (S-Movement), 1912

In 1912, prior to this discursive background, Benussi discovered a group of apparent motion that he shortly thereafter termed s-movements.* In 1912, the results of his research were published in the Zeitschrift für die gesamte Psychologie with the title “Stroboskopische Scheinbewegungen und geometrisch-optische Gestalttäuschungen” (Stroboscopic Apparent Motion and Geometric Optical Gestalt Illusions).271 He used a specially constructed stroboscope, similar to that of Wilhelm Wundt272, for his experiments. It had eight spokes, each of which had a mount for holding a depicted image. The width of the slit or peephole was variable and the light source was by incandescent lamp (fig. 64). The Müller-Lyer illusion and the Zöllner illusion, which Benussi used in most of his experiments on “inadequate Gestaltauffassung” in apparent motions or apparent corporeality, were divided into eight-phase images depicted blurred and cut out with a line-width of 0.6–0.7 mm. The eight individual images were then mounted onto the stroboscope and set into rotation. The familiar geometric patterns appeared just as expanded or constricted as he had expected for the moving images (fig. 65, 66, 67a-b). Thus, Benussi produced a sort of “mechanical” animation of phased images, in which, similar to the principle of showing a movie, setting the geometric-optical pattern into motion. He commented: “When observing the individual images the following rule generally applies: The observer either attempts to follow the given movement as such […] or the multitude of spatial forms that are produced by individual parts while others remain at rest”.273 The two apparent motions discovered by these experiments emanated from the center. He labeled these, on the one hand, as (small) s-movements in which “the direction corresponds with the direction of the contracting side”. On the other hand, he designates as (large) s-movement, in which “the direction moves in opposition to the direction of the side”.274 The apparent motion of the sides creates the notion of shapes that continuously change places with the individual parts of the object. The results Benussi presented did not remain without negative commentary nor criticism. In fact, the exceptionally polemic discussion that ensued between the representatives of the Graz Production Theory and the Berlin Gestalt School was triggered by a commentary by Kurt Koffka and Friedrich Kenkel in 1913 on Gestalt and movement experiences.275 In 1914, Benussi had to undergo a critical analysis as he termed it.276 To

which Koffka replied in the form of a very bitter dispute in his contribution dated 1915.277

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In addition to his first studies with regards to optical apparent motion, Benussi also dealt with phenomena of tactile apparent motion. The first results here were presented in 1914, and more in 1916 and 1917. he used the term kinematohaptische Scheinbewegung (cinematic-haptic apparent motion) or short KSB. “Through successive stimulation of two areas of the skin, it is possible to suggest that one object (actually the touch) had moved from one place to another.”278 It was known that the skin reacts differently to touch. That means touching the forearm, the inner hand or the forehead produce differing tactile sensations. Benussi assumed that the retina, for all practical purposes,” did not have such differentiation, [therefore (author)] the analysis of KSB would cast a new light on the studies of SB [Scheinbewegung or apparent motion (author)].”279 Benussi conducted experiments on individuals who were born blind and on sighted individuals as well. This proved that the skin, as opposed to the retina, could be stimulated with a wide variety of objects. According to Benussi, the optical and tactile apparent motion images should correspond completely. The underarm, for example, was stimulated in two main areas with a distance between them of 4 and 24 cm; the basic phenomenon correlated with an arched movement in the air.280 The time intervals and stimuli were essential here – even the skin on various parts of the body does not react the same way nor to the same degree. Benussi described this process of perception as the conversion of registering impressions.*

* The ability to transform impressions that have been recorded can be used today for the visually impaired. In the meantime it has become possible to stimulate certain areas of the skin or also other senses through electronic sensors. The sense of smell can be stimulated, for example, in order to pick up on “visual” impressions of the surroundings.

Fig. 63 Decription of Ernst Ruhmer’s electric television, 1909

Fig. 65 Vittorio Benussi: Specially constructed stroboscope, 1912

Fig. 66 Vittorio Benussi: Specially constructed stroboscope, 1912

Fig. 64 Vittorio Benussi: Various views of apparent corporeality with altering positions of the same sketch

Fig. 67a Vittorio Benussi: Specially constructed stroboscope, 1912

Fig. 67b Vittorio Benussi: Specially constructed stroboscope, 1912

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* Benussi got the tip about this device from M. Radojkovic who was professor of theoretical physics at the University of Graz, Austria.

** In the course of his experiments, Benussi gave the movements the description “E-Apparent Motions”, as an hommage to the physicist Eisenlohr.

*** The exact dating of a discovery always causes confusion. In some popular science writings and presentations we find 1911/12, which is not correct. Terms such as apparent motion, apparent corporeality, stereokinetics etc. are often not used accurately. That is why it often comes to mix-ups in terminology and dating. According to my research, Benussi only discovered and conducted intensive research on the stereokinetics during his time in Padua (as of 1922). Mauro Antonelli, the Benussi biographer and head of the Benussi archive at the University of Milan, verified my findings by an e-mail from September 9, 2010: “Dear Mrs. Schuler, I looked more closely at the Benussi archive („Fondo Benussi“: http://www.aspi. unimib.it https://webmail.unimib. it/Redirect/www.aspi. unimib.it) and can confirm that Benussi did

Combinations of Apparent Motion (1918)

At the beginning of 1918, Benussi presented a new study on the various combinations of apparent motion. In the initial experiment a stroboscopic disk was placed into rotation. Benussi used images to describe the complicated process (fig. 68). In the mirror image of the disk, and through the slit s and s’, the test person was able to discern the semi-circular up and down movements of the plotted pair of sides on the circles (recognizable as a fragment of the Müller-Lyer’s illusion). The two central points o and o’ moved, as shown in figure c. Benussi introduced the term “field of apparent motion” for the combinations of apparent motion. He then tried to examine what the reciprocal effect of the movement was within the fields of apparent motion. Among these he used the example of the two pendulum devices that the Karlsruhe physicist Wilhelm Eisenlohr had described in his textbook dated 1870: a brass bar a-a was attached on two vertical threads of the same length. On a second bar, a lead solder was hung on a cross-layer to the brass bar, p (fig. 69). When the lead solder p and the brass rod a-a begin to swing, the movement of p against a-a appears to be elliptical or circular. Eisenlohr had referred to the swinging curves that Wheatstone and later Lissajous had observed.281 * Benussi wanted to find out where a relative apparent motion ultimately existed, and when one could speak of a combined apparent motion.** These studies, which still took place in Graz, served as the basis for his later experiments on so-called stereo kinetics, which Benussi discovered between 1922 and 1925 in Padua, Italy.*** Benussi gave one of the apparent motion combinations the rather curious name of “apparent motional lapse”: “with this expression I am describing a group of phenomena in which the characteristic attribute is that the pathway of an apparent motion is deformed by means of the shape of an obvious connection of the places where the actual apparent motion occurs (is illuminated, becomes visible).”282 As an example he cited a form that was seen as a spiral shape even when it was actually the image of concentric circles (fig. 70, 71). 283/**** I am now projecting, for example, the upper (lower) half of such a picture (light on dark) onto a weakly illuminated white screen.

Behind this there are three small lamps attached in such a way that they become visible as three concentric circles (in light that shines through the screen) when they are all stimulated simultaneously. If the little lamps are illuminated alternatingly without projecting the spiral image, one achieves an appropriate frequency to produce an apparent circular motion. If one then projects half of the spiral image, the circular motion separates into two semicircular curving motions that appear displaced, depending on the circumstances (perspective). Disregarding the background of the spiral semicircle (which is hard to do) can reestablish the unified circular motion (A-reaction). If, however, instead of showing the complete picture of the spiral, further track deformations occur, the full spiral image is shown instead of the half image, resembling an elliptical type of structure. These are to be discussed elsewhere. This is not the place to go into the details such as point duality or identity when the circle disintegrates in arched movement, meaning the moment of awareness of this phenomenon and such. […] According to the imagined continuation, along which the spiral path ‘leads’ the point for a while, it will be flung out of the path that had been determined by the illuminated points; it derails.284 At the end of his article, Benussi wrote: “it is possible that the detection of the combination of apparent motions is the first step toward an experimental metaphysics.”285

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show a certain interest in the phenomena of apparent corporeality and spiral movements, which led the way for the discovery of the stereokinetic phenomena already in the winter term of 1911/1912 – when he was working at the University of Graz (see the Benussi-Archive under “Partizione Didattica”: „Didattica 3.10”, “Didattica 4.10”, “Didattica 4.14”, “Didattica 4.18”, etc.). The actual discovery of the stereokinetic phenomena didn’t take place until he was in Padua though – as is clearly discernable from the archive documentation (see ”Partizione Didattica”: “Didattica 8.7”, “Didattica 8.31” and “Didattica 8.32“ for the years 1922 to 1925). I hope I was herewith able to provide you with all the necessary information. I remain with kind regards, Mauro Antonelli.) **** Benussi gleaned the information on this illusory figure from André Breton (La Nature, 1912). The illusion was first discovered and described by James Fraser in 1908.

Fig. 68 Vittorio Benussi: Stroboscopic disk with the Müller-Lyer pattern

Fig. 69 Wilhelm Eisenlohr: Bifilar pendulum device, 1870

Fig. 70 Vittorio Benussi: Spiral image, 1918

Fig. 71 Spiral images according to J. Fraser, 1908, or A. Breton, 1912

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Stereo Kinetics

These studies are among those that Benussi continued in Padua, where he taught as of 1919. The continuation of his experiments on apparent corporeality with rotating, superimposed circular disks ultimately led to the so-called stereo kinetics in 1922/23. he did not publish his research results until 1925. his assistant and successor, cesare l. Musatti, had already collaborated with him and had first published on the subject in 1924. Two years later, Benussi summarized his studies again because he felt that his prior writing on this important phenomenon was too brief. In 1927, he described stereo kinetics as follows: The circular disks […] rotate very slowly: 1/2–1 rotation per second. In stationary position the image that is drawn on the right disk can be interpreted as ‘circle (or ellipse) + point’ or cone. In the case of the cone the interpretation is more or less of a perspective nature: a weak apparent corporeality is experienced. When the disk is rotated slowly we experience something entirely different and of a compelling nature and reality: we see a solid figure, a cone that is moving on its own and is definitely suspended in the air in three dimensions: we have achieved an assimilated conversion 286 (fig. 72). Benussi commented on this conversion in detail: After several rotations or – depending on the type of test person – even after just one, one sees the sketched point moved along the periphery of the circle at the edge of the rotating disk: relative apparent motion. The gap of the point from the periphery of the circle remains constant. The white image: circle (ellipse) point on the black rotating disk is strongly illuminated (the light source is located behind the test person). After short or longer observation, one sees a completely three-dimensional object, whose tip either faces towards the observer (or away from him). The first impression of the image is quickly inverted; not the tip (base) but the transparent base (the penetrating point) of the cone is turned towards the observer. This base can also be missing entirely, in which case the test person peers into a funnel. The cone (funnel) that is facing or is averted to the onlooker now completes two movements: a circular movement around the center of the rotating disk and its own movement. These appear like a circular motion around an axis in which the base plate is either in front of or behind the rotating disk (cone or funnel in which the tip is pointing towards or away from the onlooker), while the other collapse with the cone or funnel base. The base of the cone that is visible forms an angle (α) on the surface of the rotating

disk. While in reality the base of the registered apparent field (cone), the white circle (or the ellipse), is on the level of the rotating disk. The perceived field (cone or funnel) seems compellingly detached from the rotating disk; it moves with amazing grace, smoothness, flexibility, and lightness, rhythmically and skillfully; its walls are transparent and rigid like glass; it moves in a dark and foggy space, in a dark medium 5–10 cm in diameter in which the black disk has changed so that light and shadow glide over its surface. This compelling impression of the corporeal remains unchanged for a few seconds after the object has come to a complete stop: a positive afterimage of the corporeality remains. […] The stereokinetic conversion is tied to certain preconditions: dedicated observation, rotation of the base disk, having had certain experiences. A conscious perspectival conception of the drawing being observed (i.e. circle and dot as cone) is not a prerequisite of the conversion effect achieved during rotation 287 (fig. 73–81). In the last year of his life, Benussi began to experiment with hallucinatory movement by means of suggestion and hypnosis. The research he had done for decades served to create the basis of modern Gestalt psychology. But it was quickly replaced by the younger Berlin Gestalt Theory. contemporary cognitive psychology honors Benussi’s pioneer work anew. his research was continued by his students and successive generations of researchers at the Institute in Padua. cesare Musatti, Fabio Metelli or Gaetano Kanizsa had a stronger affinity to the previously rejected Berlin Gestalt School.

Fig. 72 Vittorio Benussi: Stereokinesis, a funnel is formed out of circles, 1922/24

Fig. 73 Vittorio Benussi: Rotational device used in reshaping during stereokinesis, 1922/23

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Fig. 74 Vittorio Benussi: Sketch of the reshaping phenomenon caused by two simultaneous movements, 1922/27

Fig. 75 Vittorio Benussi: Sketch with circles, 1922/24

Fig. 76 Vittorio Benussi: Circular disks used in stereokinesis, 1922/24

Fig. 77 Vittorio Benussi: Circular images and patterns of stereokinesis, 1922/24

Fig. 78 Cesare Mussatti: Circles of stereokinesis, 1924

Fig. 79 Cesare Mussatti: Stereokinesis, 1924

Fig. 80 Cesare Mussatti, Pentti Renvalli: Stereokinesis

Fig. 81 Marcel Duchamp: Experiments on Stereokinesis, circa 1925/27

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* Oswald Külpe was one of W. Wundt’s students. He later strongly opposed the Wundt Theory.

** Schumann explained here the apparent expansion and the contraction in the perception of geometric patterns.

Max Wertheimer: The Berlin Gestalt Psychology

Initially Max Wertheimer was a student of Christian von Ehrenfels in his hometown of Prague. As of 1902, he continued his studies in Vienna and Berlin. In 1905, he finished his doctoral degree under Oswald Külpe* in Würzburg, Germany.288 Between 1910 and 1912, he completed his qualifications to become a professor under Friedrich Schumann at the Psychological Institute of the Academy in Frankfurt/Main with his work “Experimentelle Studien über das Sehen von Bewegung” (Experimental Studies on Motion Vision).289 While in the process of writing his doctoral thesis and his continuing research in the field, and basing his ideas on the term Gestalt quality which von Ehrenfels had introduced in 1890, Wertheimer developed the scientific approach that became known as Berlin Gestalt School. Around 1900, Schumann was still very hesitant to express his thoughts on Christian von Ehrenfels’ new theory on the term Gestalt quality. He was skeptical as to whether this would constitute a relevant renewal for psychology. He commented on Ehrenfels’ opinion with a sceptical tone: “I came to the conclusion to remain cautiously reserved [in this regard (translator)].”290/** He was not the only one among his colleagues who had reservations about the expression Gestalt quality. Even ten years later, the psychologist Josef Klemens Kreibig criticized the term Gestalt quality in a manner more restrained than euphoric.291 Such was not the case with the young emerging scientists such as Max Wertheimer, who were prepared to dispute seriously with the Ehrenfels’ Gestalt quality: von Ehrenfels’ theory was strongly anticipated by Ernst Mach with his achievements on sensation complexes. The young scientists Max Wertheimer, Kurt Koffka and Wolfgang Köhler established the Berlin School of Gestalt Psychology based on these ideas and relatively quickly attracted widespread interest. Prior to the initiative which led to the founding of this popular Gestalt school by Wertheimer and his cooperatives, the Graz Gestalt psychologists (Meinong, Witasek, Benussi) and partially the Würzburg School in Professor Oswald Külpe’s circle clearly attempted to not only take over von Ehrenfels’ and Mach’s innovative theses but rather to continue their development. This means that the

elementary implementation of a Gestalt psychology had been prepared in its substantial passages long before Wertheimer and his colleagues. But the decisive change could not be brought about. Ultimately the Berlin/ Frankfurt Gestalt theorists succeeded in doing so in the second decade of the twentieth century. The youngest Gestalt school actual place of origin was not Berlin but Frankfurt/Main, Germany, where Wertheimer also performed his experiments on apparent motion between 1910 and 1912. The Berlin School of Gestalt Psychology aspired towards holistic thinking. In principle, the representatives related biotic experiments to mathematical processes in order to arrive at empirical analyses. Wertheimer himself defined Gestalt theory as Interrelationships in which what occurs within the whole cannot be deduced from the nature of the individual parts. on the contrary, there was – succinctly put – that which happens within one part of the whole is determined by internal structures of this one whole.292 The newer Berlin Gestalt psychology was obviously in opposition to the older one, and for a long time Wundt’s dominant associative psychology. In his doctoral thesis (1905) Wertheimer was still strongly bound to the associative method. But shortly after the publication of his work, a conflict arose between the psychologist carl Gustav Jung and Wertheimer. Within this dispute each of them accused the other of plagiarism because it was not clear which of them had first used the so-called word-association method. In the end, Wertheimer bore the consequences and abandoned his own studies in this field. These preliminary events in Wertheimer’s career also perhaps explain – in a superficial humane way – why he strove towards a new theoretical orientation within psychology, which distanced itself from the popular associative method.293

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* According to Witasek, in the third chapter of his book on the visualization of movement: It is stated that “[...] it goes without saying that the so-called stroboscopic phenomena are essentially to be understood as a case of production processes. [...] Everything strange or miraculous that one thought one had to see in the discoveries of Faraday, Plateau, Stampfer and others at that time and which secured their popularity as only few facts of our field of knowledge have been able to achieve, is waning. And so, it naturally makes room for the insight that, when one considers that the production of a visualization of shapes (and one such is likewise, a visualization of movement) [...] is dependent upon all of the respective shapes or movements belonging to the individual and singular placement of the shape. [...] We can create the notion of a cross or a square, readily, standing on point, simply by using the four points •:• or stressing them. We do not need the full specification of + or ◊”; quoted in Stephan Witasek, Psychologie der Raumwahrnehmung des Auges (Heidelberg, 1910), 333–334.

** Considering the controversy between

Wertheimer’s Phi-Phenomena (1910–1912) In his habilitation treatise on apparent motion, Wertheimer examined all of the former theoretical deliberations and experiments. he tested the familiar theories and disproved some of them with conflicting results in order to eventually argue his own neuropsychological approach. Wertheimer was familiar with the enormous work of Stephan Witasek, a representative of the Graz School, the 1910 publication Psychologie der Raumwahrnehmung des Auges (Psychology of the Eye’s Spatial Perception) in particular. With this work, the experimental psychologist Witasek had introduced the Graz conceptual production theory. Described are Benussi’s tests on apparent lines or the production of Gestalt concepts, and he summarized the basic theses* (fig. 82 a-b). But at that time Wertheimer had not registered the published cross-references as being firm evidence of Benussi’s achievements. It was only in a later reprint of his habilitation treatise that he first commented on the similarity of Benussi’s field of study to his own.** Wertheimer began to freelance at the Psychological Institute in Frankfurt/Main around 1910. he gave the name phi-phenomena to the results of his experiments on stroboscopic movements. Between 1910 and 1913, Wertheimer supplied significant foundational work concerning his theory of Gestalt psychology. The development of his ideas and experiments on apparent motion sound genuinely anecdotal: During a train ride from Vienna to the Rheinland – a long trip which gave him time to think – Wertheimer supposedly, very spontaneously, got off the train in Frankfurt/Main to purchase a toy stroboscope. The following morning he asked the head of the Frankfurt Institute, Friedrich Schumann, if he would be allowed to work in the lab there. The psychologist Viktor Sarris, later director of the Institute, believes to have seen a typical approach of Wertheimer which can be understood as a pattern: first the thought experiment in the train ride, then the reflection with the toy model, and finally the systematic experimentation with the tachistoscope.294 The various devices that Wertheimer used for his experiments and also modified are of particular interest here. The diascope projection device would be an example thereof. Instead of a slide he inserted a steel sheet into the sashed frame. In the center of the steel sheet he cut out a 3–4 cm

vertical and 7mm horizontal rectangle. Wertheimer affixed a cardboard disk that had two narrow vertical slits on the outer frame. When this prepared sashed frame was completely inserted into the projector, the cutout rectangle only allowed light into one of the two slits. For the other, only when one slid the frame up in the rack a bit.295 Wertheimer described the experimental process as follows: “After intermittent, rhythmic back and forth movement of the slide feed, one finds an opportune moment during constant observation in which the observer doesn’t see two static projection pictures but rather a single line that changes from one position to another.”296 Wertheimer subsequently worked on a series of push instructions that were performed with the projector. A summary of his final result was as follows: In most cases the real movement and the ‘apparent motion’ could not be differentiated, not even for the observers who had developed expertise over a period of months by looking briefly during multiple tachistoscopic experiments. In some cases (after multiple expositions of such a board, after longer periods of observing movement) the apparent motion was identified correctly. But not the one as movement and the other as non-movement, rather the state of a qualitative difference of the actual seen movement: a different movement impression or the difference in regards to visibility was registered; very often a declaration was made in a strong, energetic manner as to the one movement being different from the other. It was ‘the best movement of all’ and did not refer to the exposure of the actual movement but rather the second stationary stimulus.297 Wertheimer was obviously surprised by the strength of the illusion or rather about the clarity of perceiving the apparent motion. Wolfgang Köhler, who was an assistant at the Frankfurt Institute at the time, as well as the psychologist Kurt Koffka and his wife Mira Klein-Koffka acted as regular test persons for these experiments. The Schumann tachistoscope was unquestionably one of the most instructive devices for his visual experiments at the Institute in Frankfurt. The tachistoscope is used in perception psychology for the intermittent observation of images and symbols. The experimental psychologist Benussi used a wheel tachistoscope in 1906 in his observation of perception in his experiments (fig. 83). The device was not considered as anything special at the time, but was – like the stroboscope – rather viewed as a useful instrument in perception psychology. By the quick successive appearance of images the impression of movement is conveyed without the actual movement of an object. Wertheimer’s adapted tachistoscope for

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Jung and Wertheimer about the latter’s dissertation around 1905/1906, it seems legitimate to consider Wertheimer’s scientific integrity regarding his familiarity with and current scientific knowledge of Benussi’s experiments of 1911/1912. Particularly because there were fierce and often polemic clashes between Benussi and the representatives of the Berlin Gestalt school. Long before Wertheimer’s experiments, representatives of the older Graz Gestalt school had been considered to be notable, recognized scientists; their writings were published regularly and in numerous journals. Additionally, Wertheimer had studied with Ehrenfels in Prague. The latter had a cordial relationship with his doctoral advisor A. Meinong, the founder of the Graz experimental psychology. (Alexius Meinong, Über Gegenstandstheorie, Selbstdarstellung (Hamburg, 1988), 57. It is therefore highly probable that there was an intense scientific discourse or correspondence between Ehrenfels and the Graz experimental psychologists. Wertheimer had, in fact, left Prague already by 1902 in order to continue his studies in Vienna, Berlin, Würzburg and

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Frankfurt/Main. Regardless of that, the study of relevant literature would have been an absolutely imperative matter of course. That Wertheimer, whose theories were fundamentally based on Ehrenfels’ theory, hadn’t factored in his scientific setting, becomes less plausible.

* It is quite conceivable that the young Wertheimer used the early experiments conducted by Exner with a special wheel construction for the observation of moving afterimages in 1887 as an idea for the use of the Schumanntachistoscope for his own experiments. I have not been able to find direct proof of this but Wertheimer’s method is largely based on Exner’s experiments on apparent motion.

** Today we know that longer eye-movement rigidity causes a certain amount of fatigue of the retina and nothing can be perceived.

movement observations consisted of a bicycle that had the inner tube removed. Steel rings were placed around the wheel rim. Within the steel ring, which seemed like a special frame around the wheel rim, narrow slits were made that could be closed with a sliding device.* This exclusive wheel mechanism stood on a platform. The wheel could be set into motion with an electric motor. The observed object could be viewed with the help of a telescope. The rotating steel ring wheel was located between the telescope and the object. colors of the field of exposure were very dark to black; a light source at the side illuminated the dark field. objects being observed usually consisted of two white paper strips (about 1 x 6 cm). Interactions of conditions such as brightness, size, form and distance between the objects and their location were crucial to determine the respective conclusive result 298 (fig. 84). In his experiments with the wheel tachistoscope Wertheimer also concentrated on the question of whether eye-movements occurred. For this he conducted special tests of afterimages. optical movement impressions actually did occur despite rigid fixation, and this meant completely without eye-movement. he therefore concluded that actual eye-movement is not a requirement for seeing motion.** Just like the representatives of the Graz Gestalt theory before him, Wertheimer defined his as complex theory. When observing objects through the stroboscope, three related complex perceptions became apparent: that of succession, the optimal movement, and simultaneity.299 In terms of perception of apparent motion Wertheimer was only superficially interested in “what was available psychologically; what constituted these impressions”, 300 and his first technical experiments with the stroboscope would give the answers to these questions: “how does the optimal stage of movement occur? […] how does it disintegrate into these? What transpires in the course of these three stages?”301 The well-documented results of the physiologist Sigmund Exner (1875) served as the basis for his explanation of the phi-phenomena. Exner’s early experiments on apparent motion gave Wertheimer the basic information, and it seemed logical to him to build on his theories. In the end, Wertheimer thought he had recognized a sort of psychological short circuit that was responsible for seeing apparent motion.302 According to the theory, with each individual neuronal activity, a whole-brain activity or a so-called short circuit always occurred.

In relation to seeing actual movement (or illusion), it seemed of immense importance for Wertheimer whether the movement of two objects could appear to be identical.303 He experimented with a large number of various types of movement, with angular movements, parallel arrangements or strips of paper having a variety of color designs. His test persons’ comments supplied Wertheimer with revealing results of the subjective observations of the processes of movement. He noted that the processes of movement would consist of a sort of dual partial movement,304 which arose from the actual movement from location a to location b and then to a complete state of rest (simultaneity) (fig. 85 a-e). He therefore concentrated on detecting the actual moment at which a visual perception process transforms into an apparent motion. This led to the question that his role-model Sigmund Exner had formulated similarly in 1887: whether or not this process had already occurred on the retina or had not yet occurred until it had reached certain areas of the brain.* On January 29, 1912 Wertheimer handed in his research work “Über das Sehen von Bewegung” (On Seeing Movement) as his professorial dissertation. Immediately thereafter, in the first 1912 number, he was able to publish it in the renowned journal Zeitschrift für Psychologie (Psychology Magazine).

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* Sigmund Exner, Einige Beobachtungen über Bewegungsnachbilder, (Leipzig, 1887) 6. In 1887 Exner had already asked himself the same question regarding moving afterimages. “Years ago, based on a series of trials, I argued for the notion that afterimages of colorand light-sensations are located in the retina. I undertook the projected experiments to discover what the relationship is with the moving afterimages; the results of the same were not suitable in providing reliable evidence for the one or the other aspect. Therefore the following question: Do the physiological processes that give moving afterimages their origin occur in the retina or the brain? remains unanswered at present.”

Fig. 82a Stephan Witasek: Sketches from the book Raumvorstellungen, 1910

Fig. 82b Stephan Witasek: Sketches from the book Raumvorstellungen, 1910

Fig. 83 Tachistoscope used by Benussi, 1906

Fig. 84 Max Wertheimer, Friedrich Schumann’s tachistoscope, circa 1910/12

Fig. 85a Max Wertheimer: Types of slider arrangements, 1912

Fig. 85b Max Wertheimer: Types of slider arrangements, 1912

Fig. 85c Max Wertheimer: Types of slider arrangements, 1912

Fig. 85d Max Wertheimer: Types of slider arrangements, 1912

Fig. 85e Max Wertheimer: Types of slider arrangements, 1912

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* At the turn of the twentieth century, movie screenings already occurred during which the actors came on the stage in person in order to play their role in the film “live”, in front of the screen.

** The visual transition of two individual images is calculated. Wertheimer had to deal with the fact that some psychologists accused him of mathematizing psychology too much.

From Apparent Motion to a Repositioning of Psychology as a Whole

The revolution, which the Gestalt theory triggered within the field of psychological perception research and which took place at the turn of the twentieth century, can definitely be linked to the perpetuation and intensive research conducted on apparent motion. Wertheimer and Benussi had almost simultaneously begun to address the phenomena of apparent corporeality and apparent motion. As early as 1912, the monitoring of moving light specks or dots was included in these well-known phenomena outside of the laboratory as well, especially because of moving pictures. The new mass medium of film made the impressive experiencing of the narrow relationship between illusion and reality possible. Fascinating presentations attempted to break through or make one aware of this threshold.* For the prevailing dominance of Gestalt psychology (also referred to as perception psychology), Wertheimer and Benussi designed an alternative draft which was intended to afford new prestige for the entire scientific field of psychology, which Wundt represented. The repositioning within the field of psychology presented a remarkable opportunity for the Graz school and later for the Berlin scientists as well as for research of seeing and apparent motion within the framework of their studies. Thus Wertheimer became convinced that the phi-phenomena dealt with natural movements, which were not really discernable from actual movement. It did not emanate from individual occurrences that were compounded, as Wundt had assumed. Moreover, in the perception of phi-phenomena, extremely complex neurophysiological processes interacted. Today we know that visual intelligence does not necessarily perceive individual occurrences. This eventually manifests itself in the development of so-called special effects such as morphing in film.**

Application of a Theory for Types of Visual Perception *

Proceeding from Wertheimer’s theoretical deliberations that the optical system is based on an integrated act and not on individual parts, the American psychologists Junius Flagg Brown ** and Albert c. Voth of the University of Kansas introduced another experiment performed in 1937 on vectoring movements. Brown and Voth considered the visual field to be a so-called vector field. Within it every point was determined by size and direction. The researchers defined the field forces as forces that produced the dynamic processes within the field.305 They arrived at the conclusion that cohesive field energies exist between all objects in the visual field that, according to their nature, are vectors. As objects they drew on images as had been used and implemented by Rubin *** in his experiments of Gestalt theory. The visual field should also be presented as a manifold fourth dimension. For this reason it was important to create a time component as well as a three dimensional spatiality. The device used for this and similar experiments consisted of a wheel with cross-shaped spokes. A light source was mounted at the tip of each wheel spoke (fig. 86). After exceeding a certain rotation speed, the test person was able to recognize a square. If the rotation speed was increased, a circular shape appeared in the field of vision (fig. 87 a-b). This experiment served to prove that the observer simultaneously had real and apparent motion in his field of vision. The prime motive for this and similar experiments was to attempt to expand the use of type theory effectively in the field of “perception”306 or visual perception. Scientists assumed that the optical system served as a structured domain of vector fields, and that it was a coherent continuous field that brought with it forward-looking consequences for the field of psychology: From older established sciences like physics, we may at least hope that someday psychology will have a unified theoretical background. […] If a vector-field theory is true for perception, we may at least be sure that it is more likely true for action and emotion.307 Brown and Voth hoped that at some point psychology would be based on a standardized theoretical foundation. Ernst Mach’s idea considerations on the economy of thought had essentially already anticipated this notion.

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* The type theory was developed by B. Russel and A. N. Whitehead at the turn of the twentieth century in which various objects relate to one another in a hierarchical way in terms of amount, function, size etc. and therefore they can be defined through their relation.

** After completing his studies at Yale University, Junius Flagg Brown (1902–1970) studied with Wertheimer, Köhler and Lewin in Berlin. Brown had a leading role in disseminating Gestalt theory in the United States. He wrote a principal work on social psychology, Psychology and the Social Order (1936). Despite the great scientific acknowledgment he received, the psychology professor Brown became isolated during the 1950s in the United States professionally because of his Marxist beliefs. It is only recently that his publications have once again become of widespread interest.

*** Edgar Rubin (1886– 1951) was a Danish psychologist; He is known especially for his drawing of an optical illusion, the Rubin-Vase, in which two human facial profiles can alternately be seen as a vase.

Fig. 86 Junius F. Brown, Albert C. Voth: Device with wheel spokes and light cross

Fig. 87a Junius F. Brown, Albert C. Voth: Phenomenon when the device is rotating

Fig. 87b Junius F. Brown, Albert C. Voth: Phenomenon when the device is rotating

Karl Duncker: On Induced Movements

Wertheimer’s teachings and publications on Gestalt psychology triggered a multitude of incentives that led to a revision of the general image of psychology. It also especially benefitted his students in Berlin and later in Frankfurt/Main where he was professor from 1929 to 1933 – until his involuntary departure for the United States. The series of experiments on the perception of movement and the illusion of movement that Karl Duncker had conducted in Wertheimer’s lab between 1927 and 1929 should also be considered from this perspective. Duncker published his results in 1929 under the title “Über induzierte Bewegung. Ein Beitrag zur Theorie optisch wahrgenommener Bewegung” (concerning Induced Movement. A contribution to the Theory of Visually Perceived Movement) in the journal Psychologische Forschung. Zeitschrift für Psychologie und ihre Grenzwissenschaften (Psychological Research. A kournal for psychology and fringe sciences) 308 (fig. 88). Duncker himself defined the term of induced movement as “the movement (that) is ‘induced’ by the movement of the moving stimulus”.309 he experimented with various means of movement, which he divided into five categories: experiments in bright light with objects being moved back and forth; experiments in the dark with very slow movements; experiments in bright light with fields moved steadily in one direction; experiments in the dark with stroboscopic movements, and experiments in the dark with the rotation of a pair of stimuli being moved translationally at a constant distance. For his experiments with stroboscopic movement, Duncker used two projectors. With one of them, a single dot was projected onto the screen. The other projector projected a geometric image: a rectangle with the dimensions of 100 x 80 cm and the width of the contour lines at 3.5 cm. Two slides with the image of a rectangle were on the projector’s feeder that served as a background for the single dot on the screen. By moving the image of the rectangle rapidly back and forth, the dot appeared to be moving (fig. 89 a-c). It was not the moving background, as one would logically assume, but rather the stationary dot that was perceived as moving. Duncker’s results clarified in which way the sense of sight captures the impression of movement of larger and smaller objects. Evidently the size of the object matters: static, smaller objects are perceived as moving even though it was the larger objects or backgrounds that were moved. There is an actual reversal of the perception of the moved or unmoved objects, just

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Fig. 88 Karl Duncker: Title page of his 1929 publication

Fig. 89a Karl Duncker: Apparent motion of dot movement on a projection surface and an actual square surface

Fig. 89b Karl Duncker: Apparent motion of dot movement on a projection surface and an actual square surface

like the impression we often get that the moon follows the clouds passing by in the night sky. Duncker summarized the results of his test series as follows: The phenomenal movement of objects changing in distance (their movement ratio) is primarily determined by type and degree of the object’s (and its parts) reciprocal ‘locality’. Be it, that only the one moves towards the other. Be it that both somehow move towards each other (including the parts of a whole correlating symmetrically). To reduce this to the smallest common denominator: phenomenal movement is a shift in the natural system of reference.310 Duncker pointed out that the observer can never be outside the locomotor system but is rather an integral part of the locomotor system. he based his thesis on the experiments conducted by the psychologist herbert Kleint with test persons who remained in a tilted room while perceiving moving illusions. The fundamental idea for Kleint’s tests came from his observation of so-called Hexenschaukel (witches’ swing). This was a popular entertainment at fairs in which the persons were set into a swinging movement so that the person who was in a stationary position was under the impression that he himself was moving. An example would be of them standing on their heads.311 A few years later, Duncker published his fundamental discoveries on the topic of creativity in his book Zur Psychologie des produktiven Denkens (A Qualitative Study of Productive Thinking) dated 1935.312 Based on the term he coined “functional fixedness in connection with problem solving” he analyzed the double meanings of words or terms using psychological-mathematical methods as well as his manifold viewpoints of how to consider visual problems such as picture puzzles or optical illusions.

Fig. 89c Karl Duncker: Apparent motion of dot movement on a projection surface and an actual square surface

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Herbert Kleint: Simulation of a Tilted Room

In addition to apparent motion, the topic of apparent space became a central theme in the experimental psychology of perception. The discovery of the observer’s presence within the locomotor system and a dependence upon it led herbert Klein to examine phenomena occurring during an optical tilt of the verticality of an entire room in 1926/27 in Berlin. his results were ready for print in 1928 but he was unable to publish them in the journal Zeitschrift für Psychologie und Physiologie der Sinnesorgane (Journal of Psychology and Physiology of the sensory organs) until 1936– 38.313 Prior to that the author presented his results as lectures solely at psychological conferences. his intense engagement with phenomena in connection with spatial orientation was based on two almost simultaneous experiences he had at school – first his fascination with the illusions of movement of the Hexenschaukel (witches’ swing) at the fair and secondly his impressive experience during a film screening. For technical reasons the film stopped momentarily, just as a horseback rider was about to jump over a hurdle. At that moment, when the rider “stood still” (was frozen) in the air, Kleint’s own muscles began to flinch, an experience that he described as a sort of “downward sag” (collapsing) of his own body. It was not an actual movement but rather “a type of unconscious accompaniment of his musculature, of which we are only consciously aware under special circumstances and which in my opinion can basically befit any perception.”314 Kleint constructed a so-called turning-house that had wallpaper, pictures etc. on the walls. The test person would be placed near the center of the turning house. Above him there was a light source (fig. 90). Initially Kleint attempted to explain his spatial experience using his turning house for various experimental observations on directional perception. The turning house or the constructed room could be moved in varying directions, tilted at different angles of inclination. The test persons’ comments were recorded in protocols after just two minutes in the room. Even at a major incline: “At the moment when I forget that I am conducting an experiment, the house is almost vertical”, and after three minutes: “The incline is still there just a little bit, I notice my internal conflict of vertical versus inclined.”315

147 Kleint not only experimented with a turning house in a tilted position but he also tried to approach this perceptual phenomenon with large photographic images placed at a slant. Standing one meter away from a large wall, the test person was supposed to assess his own position in photographic image (city view) without focusing on anything in particular. In other experiments, he was to judge an optically or tactilely perceived vertical object (perpendicular thread or stick) within the field of vision and determine its ostensible vertical location.”316 After eleven test persons, the results clearly showed “that the test persons threatened to fall over in the direction of the image”.317 The test persons also seemed to have the impression of a decline in the same angle as the incline. Kleint compared his experiment with George M. Stratton’s in 1896/97 with reverse glasses. he thought he could recognize a certain similarity to his own in the process.318 In his experiments Kleint implemented various illusional situations of spatial perception. For instance, the illusion Mach had already observed from a vehicle. Mach had described this phenomenon using the train as an example and Kleint had discovered a similar type of illusion in an airplane: While the airplane landed, the landscape seemed to come into a strong incline. As it turned out, this illusion depended on the flying altitude: at a low altitude of 400 to 500 meters, the incline was less intense if it was noticed. In an open airplane the illusion did not occur at all; in a closed cabin, the visual effect of the landscape viewed at an angle created an even more intense effect. In order to clarify the phenomenon, Kleint placed a 16 x 20 cm window in the door of his turning house. The house was placed into various positions, and the test person was supposed to observe the objects through the window. A pronounced tilt of the objects was observable, a sort of distorted perception of the outer world. When the door was opened, the outside objects were no longer considered to be tilted or distorted as they had been before through the tiny window. Kleint formulated his theory of orientation structure: Based on cerebral or ear labyrinth damage, there can be chronic orientation failure of vertical and horizontal orientation: the entire room will be experienced as being in a sloping position. If, during the experiment, the entire room is not “ideally” filled – that is to say, if “disturbing” spatial circumstances were not available, it was difficult for the test persons to be upright or to get upright, even if they did not suffer from any neurological disorders. “If a certain perceived direction, for example, a defined line is in a room or

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* Experimental physiologists particularly liked using the Mach wall in the 1920s as an example for induced perception of motion. It was not originally a horizontal but rather a vertical testing category. A long carpet of circa 3 meters (Mach used a leather chamois carpet with a simple pattern) was moved slowly and evenly on a set of rollers like an endless band with the aid of a hand crank. A wire with a knot as a visual fixation point for the observer was spanned about 30 cm above the carpet. Mach wrote about it: “The observer follows the carpet and he sees it moving while the surroundings are at rest. When he fixes his vision on the knot, he himself believes to be moving with the whole room, against the arrow, while the carpet remains at rest.” (Mach, Analyse der Empfindungen, 117–118).

** This illusion is used in the theater for example: when a drive in the car is supposed to be occurring on the stage, the pictures are shown moving in the opposite direction in the back of the stage.

filled with other parallels or intersecting it, the direction is determined accordingly.”319 Because of cerebral damage or damage of the ear labyrinth, a persistent neurological deficit of the vertical-horizontal orientation can occur: the whole room is perceived as being at a constant slant. When, during the time, the whole room is not filled in an ideal manner, which means when spurious moments in the room occur, standing upright or getting into an upright position proved difficult for the test person who evidently did not suffer from any neurological problems.320 Kleint’s experiments dealt with the topic of retina stimulation, retina movement, the afterimage, the movement of the eye including the observer’s head position, either in a stationary or moving position, or the effect the outer world has on the observer (objects, lighting, mobility of objects etc.). In addition to the sense of direction, he focused his studies on the perception of movement. As he had done before, he separated the sense of direction into directional structure and isolated individual directions. Analogous to that, he also separated the perception of movement in directional structure and into isolated movements. Following Kleint’s theory “the apparent motion of an object […]” is “not a function of the shift of the retinal image, but rather its connection to other objects present or within the field in which they are contained.”321 he conducted several experiments on perception in which, on the one hand, the body moved or, on the other hand, the room and the body were in motion. To that end he also modified the so-called Mach Wall322/* by placing it in a horizontal position. Prior to that he used a thread with a piece of paper dangling from it. When the wall was moved, the piece of paper seemed to move in the opposite direction, even though it was actually at rest.** one had to distance oneself from the eye-movement theory because the test person’s eyes are only able to look in one direction and were unable to follow both directions simultaneously. Kleint concluded that for the perception of a socalled isolated movement (seeing a light spot in a dark room even though objectively or phenomenally a movement is taking place) neither a retinal shift nor an eye-movement is required. With his experiments, Kleint created a sort of virtual environment as Mach had done before him with his revolving chair. George Stratton had done the same with his inversion glasses in which illusions of the perception of a room were presented in a convincing manner. Even though he based his theory in part on the results of early experiments in order to substantiate his own theory regarding the inverted retinal image this was

not in the forefront of his own research in the way it had been with Stratton and other scientists, for example. Kleint’s experiments on perception and moving interiors could also be interpreted as early reflections on the theory of quantum mechanics, newly discovered at that time (1925) in order to introduce these in the experimental psychology of (space) observation in a closed system. This aspect was never clearly mentioned by Kleint.

Fig. 90 Herbert Kleint: Turning house, 1926

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The Inverted Image of the Retina

The functioning of the retina was not clearly understood by scientists for a long time. For Arabic scientists in the Middle Ages, the opinion prevailed that the retina carried with it the pneumas the spirit. It was Johannes Kepler, who, in 1604, discovered its real function: Kepler compared the retina to a canvas upon which the external images were displayed. The German Jesuit christoph Scheiner dissected an oxen’s eye in 1625 and discovered a small image, albeit an inverse image. This led to the question, which would preoccupy scientists for many years to come: why do we see upright? According to the psychologist Bruce E. Goldstein, visual perception is a process that doesn’t just happen. Rather, it is a complex matter even if it is just an everyday perception.323 Many processes or exact sequences in the processes of perception still have not been fully clarified. For visual perception many components work together such as environmental stimuli and the activity of the nervous system based on physiology. But cognitive influences determined by previous knowledge are significant as well. Perception is therefore not a purely physiological act but originates through the interaction between the information that stimulates the receptors and the specific information, which is at the receptor’s disposal based on the individual’s prior experiences.324 Psychologists such as Stratton and Kohler recognized that “the value of the disturbance experiment consists of complete perception, artificially going back to a prior state of development. one can observe how something evolves and draw conclusions of how something which already is completed has developed.”325 Special glasses were constructed that consisted of prisms, lenses or mirrors and were deliberately used to create visual confusion within the sciences as well as in the arts. In experimental psychology visual instruments of this sort were used for the artistic reversal of retinal images of 180° or the contortion of the field of vision from left to right or the reverse. In addition to the experiments on the change of visual direction, experiments were also conducted that manipulated the perception of distance or that caused a spatial image to be reversed in the impression of depth perception.

The scientific discourse, which continued for more than a hundred years, concerning “What is correct vision with inversion goggles and to which extent does sight change?326/ * was supported by the representatives of modern cognitive science (Dolezal, Yoshimura, linden). The basis of the conundrum of why the retina depicts the representational world the wrong way around and why we still see perpendicularly, created space for a number of speculations among philosophers and scientists. Johannes Müller determined that we could never see our own retinal image and that we could only become aware of how we actually see the world upside down by means of optical experiments.327 – Whereby we were only capable of the hypothesis that behind the retina of the eye there was a second eye, which was observing the first. This model of explanation was accepted for some time (if not explicitly) in connection with Descartes’ optical diagram dated 1677. When one assumes that an image is projected onto the retina and then reaches the human brain, then a being must exist, a homunculus, as a sort of inner observer, that looks at this image. older empirical associational psychology, which originated in England at the end of the seventeenth and beginning of the eighteenth centuries, around John locke, George Berkeley and David hume, is of significant relevance in this connection. In 1709, George Berkeley composed an especially impressive theory of vision.328 According to this theory, sight essentially develops through the sense of touch. The world that we perceive solely on a visual basis is a unique illusion. Because only that which we can touch can be real. Therefore we are primarily able to come to conclusions through the actual objects we can touch. This emphasis on the tactile sense as opposed to the sense of vision becomes ostensibly relevant in the case of experiments with inversion goggles.** his radical views led Berkeley to the conclusion that only the sense of touch could be responsible for gaining a spatial concept. Based on the earlier experiments with inversion goggles (Stratton), the psychologist Franz Bruno hoffmann also recognized a certain degree of harmony between the sense of vision and the sense of touch. however, he declared that the sense of sight had the dominant role.329

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* Kottenhoff was a student of Theodor Erismann at the University of Innsbruck and familiar with the glasses experiment. Besides the experimental problems set forth in his publications, for the first time he tried to show the differences between the American and European psychologists views on the inversion goggles in the theoretical overview of his publications.

** Considerations of the Berkeley theory in modern psychological methods can be found in Walter Lembecker’s dissertation “Berkeleys Theorie der Gesichtswahrnehmung beurteilt auf Grund der modernen Psychologie” (Universität Rostock, 1929) and Eduardo Torreani, “Die Theorie der Gesichtswahrnehmung von George Berkeley im Lichte der Modernen Naturwissenschaft” (Berlin, 1965). Both works discuss Stratton’s inversion goggles or rather Torreani and the Innsbruck goggle experiment as well.

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* After Roberto Ardigò’s death in 1919, the psychologist from Triest who was forced to leave the institute in Graz, Austria, because of his Italian heritage, Vittorio Benussi, took over the Institute in Padua.

** Stratton went to Leipzig, Germany, to write his doctoral thesis with Wilhelm Wundt after he studied in the United States.

George M. Stratton and the Experiment with Inversion Goggles

change an individual’s eye, and you change his Weltanschauung. Ernst Mach (1866)330 helmholtz conducted the first verifiable studies using inversion prisms around 1861. The experimental psychologist Roberto Ardigò at the University of Padua conducted similar experiments with prisms circa 1880. Ardigò was familiar with helmholtz’s experiments from the Handbuch der physiologischen Optik. Ardigò first published his results in 1886 in the book Opere Filosofiche”.331/* The American experimental psychologist George M. Stratton** began a series of studies on the retina and upright vision at the University of california in 1895/96. The problem he was addressing in general dealt with the necessity of image inversion for upright vision.332 Until that time essentially two theories prevailed that attempted to explain the problem of the inverted position of retinal images: the projection theory and the eye-movement theory. Stratton had originally planned to construct a special visual device so that he could experiment simultaneously with both eyes. he decided to perform the experiment monocularly because the tubes that were attached directly in front of the eyes and the automatic convergence strained the eyes greatly. his visual instrument has the right eye looking through two convex lenses with the same focal width placed close together on the visual axis (fig. 91 a-b). The tube on the left eye was covered with black paper. The first time Stratton wore the seeing device for three days. The device was removed at night and his eyes were bound shut. During the first experiment Stratton did not leave his home. he basically observed the street traffic from his window in order to gain impressions of the “outside world”. With the double lensed goggles a completely new field of vision emerged that turned everything he saw upside down. The objects viewed had to be mentally reinterpreted in order to orient himself. Bodily movements were not automatically moved in the opposite direction. A contradiction ensued between the visual appearance of the object and his sense of touch. In the beginning, the direction in which the subject reached for an object did not coincide with his visual perception. After a while, however, the unusual nature of the field of vision disap-

Fig. 91a George M. Stratton: Sketch of the eye with a normal retinal image

Fig. 91b George M. Stratton: Sketch of Stratton’s inversion goggles arrangement of lenses, 1896

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* “Such a harmony, it must be confessed, was only occasional; but that it could come at all, and particularly that it came more forcibly the longer the experiment was tried, shows clearly what the harmony of the tactual and the visual space-world consists in.” (George M. Stratton, “The spatial Harmony and Sight”, in Mind, 8 (32) (1899), 492–505).

peared. The subject returned to an acceptable normality. In his notes Stratton described how he was able to manage fairly well with the new order of things by the third day. He repeated and prolonged wearing the double-lensed goggles for a period of up to eight days. During these later experiments he even took an evening walk outdoors (fig. 92). In 1899, Stratton built a visual device with a light frame and replaced the lenses with mirrors. One mirror was placed directly above the head of the test person; the second one was directly in his field of vision at a 45-degree angle (fig. 93). Stratton could therefore see his entire body lying in front of him, turned 90 degrees horizontally. His legs suddenly appeared to be incredibly far away. In this case he did not change the direction of the objects but the perceived distance of the field of vision. By the third day his orientation had improved. Hence Stratton could confirm that the interaction between tactile sense and vision must be significant for spatial orientation.333/* “The experiment indicates that if we were to see a thing long enough in any given place, we should, sooner or later, also feel it there.”334 He initially presented his research results at the psychological convention in Munich in August 1896 and received a great deal of recognition from his colleagues for it.335 In 1920, the psychologist Natalie Förster continued with Stratton’s theory on the correlation of the sense of sight and the sense of touch. She began with her experimental research at the Psychological Institute at the University of Moscow. Later, she continued her research until the end of her academic studies at the psycho-physical laboratory at the State Academy for Arts and Sciences in Moscow at the end of the 1920s. After a preliminary report at a convention in Moscow in 1923, she published her results in Psychological Research in 1930. 336 Förster was looking for an explanation of the correlation between the spatial perception of the primary sense of touch and the primary sense of vision. Her test persons were supposed to “draw the outline of an image, which they [saw (author)] in a mirror” with a pencil.337 While doing this the test persons could only observe their hand movements in the mirror. According to Förster, the test person was given two different ideas as to their direction: one kinesthetic and one optical, which the person followed simultaneously but in reversed direction. Förster wanted to be certain about which of the senses – the sense of sight or the sense of touch – ultimately was an-

chored in our consciousness. At the end of her series of experiments, Förster came to the conclusion that first, one could confirm Stratton’s findings, and second, that the sense of vision has absolute priority for our consciousness in the correlation between sense of vision and sense of touch in spatial perception.338 Besides her reference to Stratton’s experiments, Förster referred to Margaret Wooster’s (American psychologist)339 and Karl Scholl’s (German physician)340 goggles experiments. They had also conducted research on solving the question of a new optical-motor coordination or of the host of phenomena that emerged by means of consciously created visual disorders. Wilhelm Stern*, Stratton’s scientific commentator in the renowned magazine Zeitschrift für Psychologie und Physiologie der Sinnesorgane, attempted to draw on his experiments on upright vision about thirty years later, in 1927. Stern used prisms to create a reversed image. But with that, the already minimized field of vision became even narrower and undesired reflections appeared at its edges. In his description of the history of experiments with goggles Kohler later wrote that each continuation of this experiment “was hampered by technological deficiencies.”341 The American P. Harry Ewert took a controversial position about the Stratton experiments.342 He published the results of his experiments in 1930. They supplied no evidence that the retinal image reverted after a certain period of time. His test persons could not simulate this inversion of a new visual mindscape. Ewert therefore declared Stratton’s results as pure illusions.** Ewert even charged Stratton of acting as both investigator and test person which then led to falsifications. In the course of the debate, Ewert was reproached for allowing his test person to only “breathe laboratory air” because otherwise “they might have been able to hone their observations for visual imagination”343 In the end, Ewert’s attacks led to Stratton’s experiments being barred from inclusion in American textbooks. Stratton, however, was accepted by European experimental psychologists and physiologists whose continued studies also inspired scientists in Japan to experiment in this direction, in the Sixties of the twentieth century. Almost simultaneously, in 1928, the Canadian psychologist Gordon Brown distorted the field of vision of both eyes by 75° with the help of

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* Stern was director of the Psychological Institute in Hamburg from 1916 to 1933. Because of his Jewish heritage he was dismissed summarily in 1933 from the University, of Hamburg, which he had co-founded. He and his wife had to flee to the Netherlands and then the United States. Stern’s son was the famous philosopher Günther Anders who after his life in exile in America resided in Vienna, Austria.

** Henry Ewert, IV, nr. 2, 142–163. An initial polemic debate on Stratton’s theory already had taken place with James H. Hyslop’s (American) contribution “Upright Vision” in Psychological Review in March of 1897.

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prisms, in order to disrupt depth perception. his test persons got used to the skewed outer world but there was no return to the visual reversal of the field of vision.344

Fig. 92 George M. Stratton: first inversion goggles, 1896

Fig. 93 George M. Stratton: Arrangement of mirrors for a seeing device, 1899

Early Experimental Perception Research at the Innsbruck University: Franz Hillebrand, Theodor Erismann, Ivo Kohler

Franz hillebrand, the experimental psychologist and founder of the Innsbruck Experimental laboratory for Psychology, studied philosophy with Franz Bretano. he was also a fellow student of Alexius Meinong. After his graduation in 1881, he worked for Ewald hering and for Ernst Mach in Prague. he was also given the assignment of founding a laboratory for experimental psychology in Vienna, but this failed to happen because of a lack of available laboratory space at the University of Vienna. In 1896, when hillebrand was called to the University of Innsbruck to assume the position of full professor, he set up a laboratory for psychological experiments. In his studies and teachings hillebrand concentrated primarily on visual and spatial perception, spatial geometry and the theory of cognition. Based on the approach of brain researcher Ewald hering and the physicist Ernst Mach, he emphasized the field of visual perception. Mach distinguished hillebrand and lauded him in the preface of the sixth edition of his book Analyse der Empfindungen in connection with his experiments on the physiology of the senses. Franz hillebrand worked in detail on the issue of the stroboscopic movement and published a study in 1922. It focused on his ambition “to get to a theory for stroboscopic movement that was as free of hypotheses as possible.”345 his intense involvement with the perception and the function of the retina set the course for generations to come at the Innsbruck Institute. hillebrand, who quickly became a renowned psychologist with very good connections, was also able to bring the prestigious International Psychologists’ convention to Innsbruck in 1910 346/* (fig. 94).

Fig. 94 Instruments in the exhibition at the psychology congress in Innsbruck, 1910

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* A devices exhibition was organized as part of the Innsbruck congress. A series of visual devices or equipment that could be useful for the observation and measurement of visual perception were presented. Among them were motorized color gyroscopes (spinning tops) (Institute Innsbruck), for apparent motion and moving afterimages, various models of tachistoscopes, devices for measuring rolling movements of the eye, devices for demonstrating the Hering-Hillebrand horopter deviation or a device to register head movement to “handy” memory devices. The presentation of such devices around 1900 reveals how motorized machines were already being readily used to analyze the sensory perception.

Fig. 95a Erismann/Kohler: Inversion goggles with metal mirrors

Fig. 95b Erismann/Kohler: Skiing with inversion goggles

Fig. 95c Erismann/Kohler: Inversion goggles with metal mirror

Theodor Erismann and Ivo Kohler’s Goggle Experiment

In 1926, after hillebrand suddenly died, the Swiss psychologist Theodor Erismann was appointed to be his successor in Innsbruck. After 1928, Erismann addressed the phenomenon of the inverted retinal image. With goggle experiments he caused artificial visual disorders for the normal seeing eye. The scientist searched for possibilities of recreating visual impairment – at the time, this was a hot topic because of the number of eye injuries sustained during the First World War.* The Innsbruck goggle experiment lasted for several decades and can be subdivided into three categories: testing Stratton’s results with inversion goggles, experiments with prisms and half-prisms, and studies with colored goggles. After 1939, Ivo Kohler, who was one of Erismann’s** students at the time, participated in the experiments. In addition to repeating Stratton’s experiments, Erismann and Kohler dealt with the topic of seeing forms and images, of size and movement as well as color. The results of the studies on seeing provided information on the structure and evolution of physiological perception within the framework of the milieu of common stimuli. Decades of fundamental research led to the discovery of so-called situational after-effects, which are related to ordinary afterimages. These aftereffects appeared after lengthy periods of tests with goggles. What was manifested to Erismann/Kohler was that these aftereffects occurred “as soon as stimuli were placed on the subject’s opened eye” the “sensitivity of light, color, size and movement of objects or for the entire system of the visual direction changed in a peculiar manner” depending on the type of goggles worn.347 Erismann coined the term situational-aftereffect, and in 1947 it was presented at a psychologists’ convention in Bonn, Germany. Kohler preferred using the term conditioned senses.348 In 1928, Erismann used a metal mirror that was mounted horizontally underneath the eyes for his experiments; the larger the mirror, the wider the field of vision. But because of how the mirror was mounted, one could no longer see one’s own feet. For this reason the experiment could only be conducted at the Institute. As of 1947, new construction allowed the investigators to place the mirror over the subject’s eyes in a manner that was similar to a peaked cap. This way one could use mirrors that were twice as big and the construction became “street-suitable” (fig. 95 a-f ). It was possible to take a bicycle tour by the fourth day and a ski trip by the

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* Theodor Erismann was Swiss. He was born in Moscow in 1883 and grew up there. While studying he first was interested in physics and in 1908 went to lectures held by Albert Einstein in Zurich.

** In 1946 Kohler became Erismann’s assistant and in 1956 he took over as head of the Institute.

Fig. 95d Visual perception with inversion goggles

Fig. 95e Visual perception with inversion goggles

Fig. 95f Visual perception with inversion goggles

sixth day. According to the test person, objects that were upright were seen upside down for the first few minutes after removal of the goggles. For the two following days, apparent motion and a slight feeling of vertigo ensued. The inversion experiments were expanded to stretch over a period of ten days. According to Kohler, what was experienced should oscillate between inverted and upright vision. Kohler compared the observer of inverted images using the example of the Schröder stairs.349 Erismann began conducting his experiments on impaired vision caused by prism goggles in 1933. The first test began by wearing binocular prism goggles for a period of ten days. After two days, the apparent motion had disappeared and the curvature of the lines as well as the distorted images were noticeably reduced (fig. 96, 97 a-c, 98, 99, 100). After ten days, all of the visual distortions had receded. Upon removing the goggles powerful apparent motion, curvatures as well as distorted images returned. The subject described the condition as comparable to being inebriated. This feeling disappeared after four days. Kohler himself expanded the wearing of the prism goggles to a maximum of 124 days. Besides photographs of the experiments, the Innsbruck goggles experiments were documented in a scientific instructional film (fig. 101, 102). After completion of the Innsbruck experiments with specialized perception goggles in the 1950s, Kohler, who headed the Psychological Institute * in Innsbruck, was invited to be a guest lecturer at American universities. Above and beyond that he was in close contact with the wellknown American perception researcher James Gibson who coined the phrase ecological optics. The most important writings on the subject were translated into German with the help of Ivo Kohler.

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* Ernst Pöppel wrote his doctoral dissertation under Kohler and described him as an ingenious experimenter. He was a truly independent but uncomfortable thinker and was also a very unusual faculty member: “who was often bored in the meetings and took out white mice in order to train them during the meetings.” (Quote Ernst Pöppel, Der Rahmen. Ein Blick des Gehirns auf unser Ich (München, 2006), 250; Additionally it should be mentioned that Kohler was also a good draftsman, which I could ascertain by looking through his partial estate at the Institute of Psychology in Innsbruck as well as at his working sketches.

Fig. 96 Prism glasses

Fig. 97a Distortion due to prism glasses

Fig. 97b Distortion due to prism glasses

Fig. 97c Distortion due to prism glasses

Fig. 98 Distorted perception due to prism glasses

Fig. 99 Seeing device for distorted visual perception

Fig. 100 Color prism classes

Fig. 101 Erismann during a seeing experiment

Fig. 102 Experiments with inversion goggles

Consecutive Experiments with Inversion Goggles after 1955

The Innsbruck researchers received widespread international encouragement. The German-American art historian Rudolf Arnheim, curator of the Responsive Eyes (1966) exhibition at MoMA on kinetic and OpArt, was among those impressed by their work. The Innsbruck distortion goggles experiments were so impressive because with them new images of perception, the so-called “rubber world”, could be produced.350 According to neuroscientist and author of Auge und Gehirn (Eye and Brain) Richard Gregory, Stratton’s and Erismann/Kohler’s experiments were among the best visual experiments that are justifiably still discussed to this day. They have inspired researchers around the world to repeat many of the experiments and to conduct follow-up experiments. In the mid 1950s. experiments were even conducted on animals at the University of Chicago using inversion goggles.351 Chickens in particular were readily used for experiments on the sense of vision and sense of touch because of their exceptionally rapid movements when unerringly picking at a kernel of corn. A brief time after having hatched from an egg, chicks demonstrate an amazing accuracy when gathering food.352 The scientists constructed little helmet-like masks for the newly hatched chicks and inserted lenses that altered the field of vision by a few degrees (fig. 103). They noticed however that even over a longer test period the chicks were unable to adapt. They could not ingest any food because they kept pecking adjacent to the kernel. Apparently the chicks learned how to peck over a relatively short span of time because the older test chicks had much less difficulty in adapting visually and coordinating the consumption of food. Between 1960 and 1995, thirty-seven long-term experiments with upright vision and left-right inversion were conducted in Japan. These experiments remained relatively unnoticed in the international scientific discourse because the results were almost exclusively published in Japanese. Yoshimuro first summarized the Japanese experiments from this period in his essay written in English.353/* The Japanese researches tied in with the experiments conducted by Stratton and Kohler. They essentially continued the experiments in order to make their findings on visual and cognitive-motoric perception useful for modern day robotic technology. In the United States, on the other hand, scientists hoped to

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* On the occasion of the commemorative publication for Ivo Kohler in 1984, a bibliography of the Japanese research on artificially induced visual disturbances that were put together by Tatsuro Makino, professor at the University of Tokyo, was published in Lothar Spillmann, Bill R. Wooten, eds., Sensory Experience, Adaptation, and Perception, Commemorative publication for Ivo Kohler (Hillsdale, New Jersey, 1984), xxv-xxvii.

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use the research results in aeronautical areas such as in supporting flight simulators, for example. The experiments of Irvin Rock and charles S. harris that were performed around 1965 on visual and haptic illusions received a great deal of attention. objects were observed through prisms that would make them appear to shrink, grow or appear inverted. The conclusion had to be that vision was more important for perception than haptics: “vision is totally dominant over touch” 354 (fig. 104). These findings concur with those that Franz B. hoffmann presented in his work Die Lehre vom Raumsinn des Auges (Science of spatial perception of the eye), on the sense of space in 1925.355 The psychologist hubert Dolezal, a student of the renowned perception scientist James J. Gibson, initiated a series of interesting experiments with binocular visual devices at the end of the 1960s. The starting point was Stratton’s and Kohler’s experiments. In 1970, for example, Dolezal wore a visual device that he constructed to wear for a period of 6 days. It consisted of two 30cm long pipes with an interval of 2.5cm and a diameter of 4.5cm.356 The subjects’ field of vision was extremely limited. When the observer fixated on an object with the vastly reduced field of vision, one single image emerged (fig. 105a-b). In the summer of 1971, Dolezal spent five weeks in a small Greek village wearing prism goggles that displaced the normal vision by 180° vertically.357 During this optical transformation, left and right were not transposed. In addition to the visual irritation, the 3.8kg of weight of the visual device – which was made out of a football helmet – was burdensome for him. he still performed everyday activities such as riding a bike, swimming, hiking, driving a car, riding a donkey, playing chess and writing letters, etc. The scientist wanted to spend the entire test period exclusively in an outdoor environment in order to show how the visual and the motor systems are integrated (fig. 106). nASA built on his research in order to reduce the uncomfortable effects of the absence of gravity such as, for example, an astronaut’s nausea. he did not publish his experiences, which he had previously recorded on tape until 1982 in his book Living in a World Transformed. Perceptual and Performatory Adaptation to Visual Distortion. neuroscientist David linden at the Max-Planck-Institute conducted the most current studies for brain research in Frankfurt/Main under Wolf

Singer’s direction. linden repeated Stratton’s and Kohler’s experiments and tested the cerebral images of the subjects with magnetic resonance imaging and presented the results within the framework of his dissertation (1999).358 Shortly before that, linden published the essay “The Myth of Upright Vision. A Psychophysical and Functional Imaging Study of Adaptation to Inverting Spectacles” (1999).359 The results of his experiments confirmed the rapid visual-motor adaptation of the subjects within the span of six to ten days. In the cerebral images however, aided by the MRI, a dislocation between the cognitive-motoric adaptation and the perceptual adaptation was detectable (functional magnetic resonance images). The experiments showed that the test person is able to learn to adjust to an altered environment independent of the unusually distorted field of vision. Ten years later linden, who in the meantime had obtained a professorship at the University of Bangor (GB), commented on the experiment with the inversion goggles as follows: “I continue to consider the question of adaptation (perceptual vs. cognitive/motoric) with inversion goggles as well as other transformations of sensory inputs as (absolutely) fascinating.”360

Fig. 103 Chicks with inversion prisms, circa 1955

Fig. 104 Irvin Rock, Charles Harris: Prism experiments, 1965

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Fig. 105a Hubert Dolezal: Sketches of tubular glasses, 1970

Fig. 105b Hubert Dolezal: tubular glasses, 1970

Fig. 106 Hubert Dolezal: Inversion prism goggles with a helmet, 1971

Resume of Part I

The roughly 150 years of experimental research into seeing constructed apparent motion and apparent space within the fields of physiology and psychology yielded the basic knowledge for today’s life amid a virtual environment. Some of this fundamental knowledge may appear partially antiquated or quaint, yet the pioneers in this field were able to collect the first experiences and to document these as to the means by which virtuality can be created as well as how virtuality can reasonably be perceived and felt. Erismann considered apparent motion, also referred to as stroboscopic movement, to be “the psychological basis of the entire [field of (translator)] cinematography.”361 How they can be elicited and how the observer can conceive or perceive them to be real has been under scrutiny since the beginning of the nineteenth century. At that time the [scientific (translator)] research approach was critical towards all phenomena with a psychological provenance that could not be understood as real. Phenomena such as apparent motion were regarded as physical curiosities that represented the incommensurable. Thus the physicist Ernst Mach (1865) had to battle critical comments on his experiments that some scientists: […] made concerning his experiments […]. Recently a distinguished scholar was surprised by my experiments. ‘Why so? Those must be mere illusions!’ – These times have passed. We now know that even ‘illusions’ are facts and are subject to laws. We are even doing too much good and forgetting that every psychological event must correspond to something physical, and finding it is very desirable.362 And yet the Gestalt schools got lost in a fog of subjectivism,363 and many discoveries that were in part brilliant were lost. Connected to that, according to David Marr, there was also a general loss in interest for what perception actually was. 364 The historical research experiments into perception have been revived and repeated in art and not in the sciences. In so doing artistic autonomy is often abandoned. This means that there is no further actual, independent and reflective development on the theoretical basis but rather the existing scientific concepts and their practical applications are transferred into an artistic context. For the past several years, the artist and biologist Carsten Höller has successfully initiated activities with reconstructions of Stratton’s and Kohler’s inversion spectacles. Currently, the highly celebrated Olafur Eliasson

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* With the descriptive expression “living image” the new medium of film was advertised around 1900 in Berlin and a short time later in 1903 in Vienna.

** The term CAVE stands for Cave Automatic Virtual Environment. This surrounding projection surface was developed at the beginning of the 1990s in Japan and the USA. With the help of stereo glasses 3D picture animation is produced. The viewer is literally within a singular illusion room. Oliver Grau, Virtuelle Kunst in Geschichte und in Gegenwart (Berlin, 2002), 124–127.

works similarly: he uses the methods of scientific transfer in a highly professional manner for his elaborate art projects. He infiltrates his artwork with technical-theoretic scientific work of natural scientists in order to fill his installations with relevant content. The technology he uses is contemporary, and yet he undoubtedly borrowed the basics, for the content of his concepts, from the scientific achievements of the nineteenth century. Although new technology is crucial for Eliasson’s work, for the viewer it remains subdued in the background – behind the oversized interference of that which is make-believe and that which is real. This artistic practice can be defined as neo-historicism or post-historicism with regard to the historical epistemology.365 As soon as we turn on the computer or the television or look at ads in public spaces or see a movie at the movie theater today, apparent motion becomes real through virtual images. In our everyday world we are continuously confronted with apparent motion. At the end of the nineteenth century, the term living images had already been introduced. At the entryway to movie theaters the slogan living photography was used.* Karl Wilhelm WolfCzapek used the term living images for the first time in his theoretical work Die Kinematographie, Wesen, Entstehung und Ziele des lebenden Bildes (Cinematography, essence, development and goals of the living images) in 1908.366 Wolf-Czapek proved to have downright visionary views on the possible future application possibilities of film: […] a picture of the living, moving human has been assured for all time […]. If one allows one’s imagination free rein, one can envision how one day every house will have its own little cinematographic device. How friends and relatives will send one another living portrait films and therefore, even from afar they can enjoy a reunion, how grown-ups showcase pictures of their childhood, the survivor can magically bring the deceased back to life on the wall.367 The illusory world and reality overlap increasingly today. In doing so the perceived differences of illusion and real environment ultimately disappear.368 According to that principle, a virtual CAVE ** is pure apparent corporeality that exists only through visual cognitive faculties with the help of large computers on electronic microprocessors. Since the beginning of the 80s of the twentieth century, new companies have come into existence in Silicon Valley that develop and sell special software for virtual environments. Additionally, publications have been produced and Hollywood movies (Terminator, Matrix) made that concentrate on the topic of virtual realities or cyberspace. The term cyberspace became increasingly popular

outside the computer community with the book Neuromancer by William Gibson in 1984. The computer pioneer Jaron lanier introduced the expression virtual reality in 1987 as a term for virtual environments. Art and cultural festivals such as the famous Ars Electronica first become dedicated to digital techniques and virtual phenomena as of 1984.369 In his contribution Zur Geschichte und Ästhetik der digitalen Kunst (on the history and Aesthetics of Digital Art) the media artist Peter Weibel denotes the new digital image* or the new digital sound as – by means of digital technique – freed image or freed sound.370 The information and computer sciences in the twentieth century as well as the cognitive sciences meant a continuation of the study of perception of movement. The complex neuro-sciences are divided into specific subcategories such as neurophysiology, neurochemistry, neurobiology, neurophilosophy or neuroaesthetics and so forth. Today the human retina is considered as a sort of neuronal “computer” that highly reduces or screens what should ultimately enter our consciousness, with its cones and rods, even before the visual information arrives at the brain. According to the neurobiologist Manfred Fahle, our individual perception already begins on the retinal plane.371 But what is perception? This question remains inconsistently defined to this day. Ever since the development of computer sciences, perception and therefore vision is understood as a sequence of processes that are analogous to computer programs. They take place gradually (Ulric neisser, David Marr). Perception is a basic achievement of animate beings, and serves primarily for orientation in the environment and in survival. Social life is also implicated here and is thus defined by the neurobiologist Gerhard Roth.372 The physiological and psychological insight into apparent motion, apparent contours and apparent spatiality create the foundation for further technological developments such as the construction of machines that can see.** It is here that the ability to coordinate the sense of sight and the motoric senses becomes relevant. According to the question of the dominant sense of perception, which George Berkeley had already addressed in 1709 in his paper on a new theory of vision, has recently been receiving increased attention. In addition to the historical scientific results on vision and apparent motion (Roget, Purkinje, Plateau, Zöllner, oppel, helmholtz, Mach, Exner, Benussi, Wertheimer and Duncker), the perception of an image or an object in appar-

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* Beginning in the 1990s Weibel used the term “living images” synonymously for virtual image world in his discussions and writings. Peter Weibel in conversation, Dec. 6, 2008 in Karlsruhe.

** The psychologists Oliver G. Selfridge and Ulric Neisser began their 1960 essay Pattern Recognition by Machine with the following introductory sentence: “Can a machine think? The answer to this old chestnut is certainly yes.” (quotation taken from: Perception: Mechanisms and Models, 21.) One has abandoned the idea of the analogy between the biological brain and the computer brain. The construction of an artificial human brain ranks among the hottest concepts of the 21st century in the neurosciences.

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* Marr died of leukemia in 1980 at the age of 35. His theory on vision remains a fragment of deliberations that developed between 1975 and his early death. After his death his major work was published in which he shows the complexity of vision and tries to approach the issue mathematically.

** Martin Tröndle from the Institut für Kunstforschung at the Hochschule für Gestaltung und Kunst in Basel put a data armband around 600 visitors arms at the St. Gallen art museum that registered these measurements within his E-Motion project (2009). (http://www.mappingmuseum-experience.co m/ueber-das-projekt/ kurzbeschreibung, May 14, 2015).

ent spatiality is a compulsory aspect of virtuality. With their experiments in spatial perception Wheatstone, Stratton, Benussi, Witasek, Kleint, and Erismann/Kohler submitted the fundamental knowledge on spatial sight. The bases for the development of 3D animation and interactive immersion is due to these historical experiments. In 1960, Béla Julesz was able to demonstrate in the Bell laboratories how important binocular disparity of the eyes is for spatial perception with the aid of a computer generated, random dot stereogram.373 When one regards two-pixel images stereo-optically, each eye is shown only a single image, for instance, a floating rectangle can be seen. David Marr’s (1982)374 algorithmic approach contributed to a better understanding of object recognition. Marr also considers perception to be a process that takes place in several steps. To this end he developed computer programs that were comprised of several steps and that essentially had a three-tiered structure: a simple sketch (differentiation of light is determined, structure and surface-textures), 2.5D sketch (a depth perception image that is observer oriented, movement orientation) and the 3D model (independent from observer standpoint, memory content, experiences).375/* neuroaesthetics is a more recent branch of neurosciences that examines the interconnection of neuroscience, beauty and art. For a study in this context visitors of the St. Gallen art museum recently wore bracelets that were mobile measuring devices.** The goal was a psycho-geographical account of how the viewer experienced the art at the exhibition. Their heart rate was measured as well as the speed at which they walked through the museum and how long they regarded each artwork. The data measured was supplemented by individual surveys. Representatives of modern neuroaesthetics who attempt to take terms such as ideal beauty or a predetermination of great art and attempt to define them practice a highly advanced method for finding data in the human brain. A major representative of this branch of science is the English neurologist Semir Zeki. his declared objective is aimed at the idea of how art and beauty stimulate the brain. Zeki is convinced that artists have been working on a specific visual grammar for many thousands of years. he assumes that with the help of neuroaesthetic methods he will be able to decode this. What is conspicuous about Zeki’s studies is that advocates of the ideology of the arts as well as those who are supporters of archaic thought in art have received this idea with enthusiasm. Primarily large pharmaceutical corporations such as Schering are among the sponsors for projects within the framework of these aspects of neuroaesthetics. In recent times

funds spent on the neurosciences for economic and image purposes has increasingly served to benefit art projects.376

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Strong criticism of the generally advanced research projects comes primarily from within. hence an appeal coming from the neuroscientists such as the neurologist Max Bennett should not be surprising. Although he was not particularly skeptical about special projects in neuroaesthetics, he complained about utterances coming from the philosophers’ camp. Bennett considers it to be a genuine necessity to integrate philosophers into the teams of the research projects on modern brain research. According to him, philosophers don’t do their career of critical thinking justice with regards to neurosciences; in most current developments in cognitive sciences their comments have been too compliant. he himself would prefer philosophers to serve in opposition and not be consensual partners because their critical voice would not only enliven the research in terms of human consciousness, but would also serve the neurosciences “[…] in their practice of leading the way.”377 Along with the philosopher Peter hacker, Max Bennett published a voluminous piece of writing with the title Philosophical Foundations of Neuroscience. Bennett’s renowned mentor, the nobel Prize laureate John carew Eccles, already anticipated this idea. he and the philosopher Sir Karl Popper had already published the standard reference book on human consciousness Das Ich und sein Gehirn (The Self and Its Brain: An Argument for Interactionism).

* In this connection Pöppel borrowed the term framework from Marvin Minsky or the sociologist Erving Goffmann. Minsky had developed a framework theory for the computer: a computer must have a framework for each scene that it describes from the real world. When, therefore, a computer is supposed to describe a room then it is based on the information that there is furniture there etc. Goffmann’s theory of a framework analysis studied the various everyday occurrences because everyday life creates a “framework” of situations.

In his book Der Rahmen (The Framework) the neuropsychologist Ernst Pöppel describes Bennett’s positive experiences with transdisciplinary approaches.378 An entire chapter is dedicated to productive cooperation with artists. he expresses himself, as being surprised by the conspicuous coherence in art and scientific depictions such as the works by Jackson Pollock and images of nerve cells. Pöppel also saw a link in content such as observations on identity in science and the topic of the Doppelgänger in portraiture. The positive mutual implementation delighted the neuroscientist greatly in his observations on the interaction of science and art. he was certain that art and modern neurosciences would create a new framework with one another.* This innovative dovetailing of the disciplines is not only widely discussed theoretically today but is already in practice de facto. long ago, it was Ernst Mach who had theorized on the advantages of deliberate attention paid to an active cooperation of disciplines. he considered it to be a vision of a merging among different fields all of which are concerned with the same problems and solutions.

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PA RT 2 From the Artistic Transformation to Immateriality The Beginnings of Kinetic Art at the Turn of the Twentieth Century

Times of crises often cause a process of rethinking and radical changing of approaches and procedures. With the enormous opportunity that coincided with the newly developed perspective, paradigm change in specific genres often merge as they have for art at the beginning of the twentieth century. The modern avant-garde visual artist defied naturalistic-aesthetic guidelines and picturesque techniques. The new challenge for the progressive artist was to find a new visual language or to develop novel modes of expression that were on a par with the innovative phenomena in the natural sciences or with the new media of photography and film that could provide new options for the artistic picture or object. how to transfer real movement onto a panel or into a (static) sculpture soon evolved into a central theme in art in the early twentieth century. Although film was already a mass medium at that time, it became increasingly sophisticated both in terms of technology and content.379 Very early forms of expanded cinema were shown in Vienna in 1913.380 Although there were only black-and-white movies, the fascination with the moving bodies and their representation had increased immeasurably. At the turn of the twentieth century, some artists began to show a cautious interest in the new scientific achievements. The range stretched from experimental physics and physiology to psychology. It is possible that this interest and the tendency to experiment artistically in this direction were expedited by the progress made in the technical production of images. In striving to include artificially produced movement within a work of art, kinetic art of the twentieth century was created. To this day it has been continued in new image technologies. From the principle of moving images and especially on the basis of the recognition of apparent motion, both kinetic art (places object/subject in motion) and later op art (perceptual illusions especially entoptic illusions) developed, which the natural scientist Jan Purkinje worked on, observed and commented on as of 1819. A further step in the direction of moving art took place in video art during the mid1960s with the involvement of the viewer. It would then reach its actual apex in interactive and digital art.

By 1900, the focus on movement was no longer a novelty in the realm of the newer aesthetics and philosophy. The philosopher Theodor Dahmen attempted to make “the principle of movement the sole fundamental law of aesthetics as a whole” in his book Die Theorie des Schönen. Von dem Bewegungsprinzip abgeleitete Ästhetik (The Theory of the Beautiful: Aesthetics derived from the Principle of Movement).381/* For the first time artists who were fascinated by the technological revolution placed value on not describing themselves as artists, but rather as non-artists. They got to the heart of the matter**, like Marcel Duchamp with his famous question, whether one could also create art, without it being art.*** Preliminary artist reactions came in the form of cubism and in 1908/09 with the Italian Futurist Manifesto. They were the first group of artists for which movement was central for their particular type of art. Futurist painting often concentrated on representing the individual phases of movement by multiplication of the figure in order to simulate continuous movement. But it was not only the Futurists who were searching for new solutions in depicting the principle of movement in the fine arts. The Dadaists, Surrealists and representatives of Bauhaus as well as the Russian constructivists grappled intensely with the topic of movement. In art history, naum Gabo is considered to be the inventor of kinetic spatial constructions. In 1920, he exhibited his first kinetic sculpture with a motor-driven steel spring. At the same time Marcel Duchamp experimented with circles and spirals painted on disks that he made rotate. With this Duchamp transferred the psychological experimentation on stereo kinetics into an artistic context for the first time.

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* The work was highly criticized. Dahmen was reproached for having compiled so many laws outside logical connections, without proving them empirically.

** As a working note Duchamp asked in 1913: “can one make works, that are not “art”? Quote taken from Serge Stauffer, Marcel Duchamp, Die Schriften (Zurich, 1983), 125.

*** Duchamp: “I was interested in ideas – not merely visual products. I wanted to put painting once again at the service of the mind.” Quotation taken from Martin Jay, Downcast Eyes. The Denigration of Vision in TwentiethCentury French Thought, (Berkeley, Los Angeles, London 1994), 164.

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* The Duchamp-Wheel mas made of the front wheel of a bike and was mounted on a stool. It was never exhibited and after his studio was dissolved in 1917 it was lost. In an interview in 1965 Duchamp affirms that it was “a private experiment of which I never thought it would be shown publicly) (Quote taken from Dieter Daniels, Duchamp und die anderen. Ein Modellfall einer künstlerischen Wirkungsgeschichte I (Köln, 1992), 170) The reconstruction of the bike took place in 1951 as part of an exhibition Readymades (Ibid., 167) In Daniels’ dissertation there is no connection made to Max Wertheimer or to Vittorio Benussi, the discoverer of the stereokinetic effect (1922/24).

** The verification as to which André Breton is being referred to in this short article has not been possible to date. If the article is actually from the surrealist artist André Breton (1896– 1966) has not been verified. What is certain, is that Breton had started studying medicine as of 1913. There is also one more clue: Breton used the cover of the relatively well-known conservative magazine La Nature as a template for his surrealist magazine.

From Schumann/Wertheimer Wheel-Tachistoscope to Duchamp’s Readymade Roue de bicyclette (Bicycle Wheel)

In the spring of 1913, Duchamp placed his first bicycle* in his Paris studio. By 1915, the term readymade was supposed to be introduced in New York for sculptures made out of everyday objects that were out of context. The Duchamp wheel is not only the first known readymade but can also be considered to be the first kinetic sculpture (fig. 107). Duchamp had been entertaining the idea for some time incorporating moments of movement into his work. He seemed to have a special affinity for all things turning, such as wheels and windmills. Wheel-shaped items can be found in his pictures after 1911 in Moulin à Café (Coffee Grinder) for example (fig. 108, 109). In his Cubo-Futurist painting Nu descendant un escalier (Nude Descending a Staircase) dated 1912, he showed successive sequences of the processes of movements of a human body. It is entirely conceivable that Duchamp was impressed by the article and images Quelques Illusions d’Optique (Some optical illusions) by André Breton** which he published in 1912 in La Nature, Revue des Sciences. They had already influenced Vittorio Benussi with his experiments on combined apparent motion in 1918. As he himself always emphasized, Duchamp was “truly spellbound” by the phenomenon of seeing movement.*** It is also well known that Duchamp was very interested in flying objects. Around 1909, he acquired a postcard on which there was a picture of an airplane although it was more of a strange object that consisted of numerous filigree bars and wheels (fig. 110). Years later, in New York on October 20, 1920, Duchamp activated his first optical machine that had motorized rotating propellers (fig. 111). The speed at which the machine’s propellers turned was so fast that it was life threatening and at the same time surprising for him. At one of the first demonstrations, the rotating blades almost killed one of his artist friends, Man Ray.382 For Duchamp the topic of the depiction of revolving spirals became increasingly interesting. Beginning in 1918, he created drawings with spiral. On November 8, 1924 in Paris, Duchamp’s second optical machine was displayed: from the center of a half circular glass form spiral-like lines extended over the form.383 The arched glass ball was mounted on a freestanding rod and made to turn quickly (fig. 112, 113a-c).384 As reflected in his films such as Anémic Cinéma (1925/26) or Rotoreliefs (1935) Duchamp later dealt with illusions of perception. The above works

Fig. 107 Marcel Duchamp: Bicycle Wheel, 1913, replica of a lost original

Fig. 108 Marcel Duchamp: Coffee Grinder, 1911

Fig. 109 Marcel Duchamp: sketches of Coffee Grinder, 1911

Fig. 110 Postcard with airplane, 1909

Fig. 111 Marcel Duchamp: Optical machine, 1920

Fig. 112 Marcel Duchamp: Optical machine, 1920

Fig. 113a Marcel Duchamp: Glass sphere on tripod, 1924

Fig. 113b Marcel Duchamp: Glass sphere on tripod, 1924

appear to be direct quotations from the field of experimental psychology. They seem to have been drawn from Max Wertheimer’s experiments on phi-phenomena in particular or Vittorio Benussi’s experiments on stereo kinetics (1922/26). Duchamp’s later work clearly reveals the connection with the experiments of Wertheimer and Benussi (fig. 114, 115, 116 a-b). These aspects of perceptual experimentation within Duchamp’s works have been discussed in depth and documented in various exhibitions and art historical texts. Despite the multitude of interpretations on the reception of Duchamp’s readymades, the uncanny similarity between the Duchamp bicyclewheel object and the Schumann/Wertheimer-Tachistoscope does not seem to have caught anyone’s attention (1898–1910). Many factors indicate that Duchamp, fascinated by the visualization of movement, would have been familiar with the new studies on oscillopsia by Max Wertheimer. It is also conceivable that he used his stay in Munich,* in the summer of 1912, to delve more deeply into these studies. Because Duchamp spoke fluent German, there would have been no problem in communicating. To date, his stay in Germany in 1912 has been a blind spot in his biography. There are barely any concrete references as to what moved him to stay in Germany that particular summer. What is definitely known is that he had no real interest in meeting the artist Wassily Kandinsky who was already famous by then.385 Based on his preference for scientific literature and especially that on theories of perception of kinesis, it seems probable that he would have been anxious to view Wertheimer’s research. he would have been highly interested in viewing Wertheimer’s inventions. Upon his return to Paris in 1913, he constructed his first bicycle object in his Paris studio. This was not entirely coincidental. It was not originally created as an artwork. Duchamp emphasized this repeatedly – he stated that he simply wanted an object within reach so that he could set it in motion by hand and observe it readily. one can deduce from some of his notes and comments that he liked to combine the turning of the wheel with the flickering of an open flame in a fireplace. herbert Molderings, the Duchamp expert, believes that Duchamp serendipitously discovered something in his readymades that he hadn’t originally been looking for. Molderings cites hans-Jörg Rheinberger’s findings on experimental systems386 that a researcher might incorporate many different objects in his experiments without necessarily knowing or being able to formulate clearly the full purpose of these objects.387 In

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*** The artist Daniel Spoerri who knew Duchamp personally told the author in an interview that Duchamp was very interested in the physical and cognitive phenomena. He allowed these to flow into his work although he shied away from giving away the source of his ideas (interview with the author on January 10, 2011).

* During this summer Duchamp traveled from Munich to Berlin and other German cities.

Fig. 113c Marcel Duchamp: Glass sphere on tripod, 1924

Fig. 115 Device used to generate moving afterimages, circa 1900

Fig. 114 Marcel Duchamp: Anémic Cinéma, circa 1925/26

Fig. 116a Marcel Duchamp: Rotoreliefs, 1935

Fig. 116b Marcel Duchamp: Rotoreliefs, 1935

Fig. 117 Max Wertheimer in front of a Schumann/WertheimerWheel tachistoscope

Fig. 118 Marcel Duchamp with his bicycle wheel, first Readymade

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Duchamp’s case, at any rate, the wheel in his studio was not primarily an autonomous work of art but rather a personal visual object or, as he himself described it as his own very personal experiment. There can be no doubt that Duchamp, who had a keen interest in the Schumann/ Wertheimer wheel-tachistoscope, who had studied that type of movement and, considering the art historical connections, had been familiar with and therefore influenced by the invention. consequently he would be considered the godfather of the first readymades (fig. 117 and 118).

Influence of Perception Research on Art after 1960

Since the 60s of the last century, a program schedule aligning art and technology has occurred at the more advanced exhibition houses. Individual forerunners had always rebelled against the monopolization of fields of expertise. The interconnection or Verfransungen (Adorno) of art and the natural sciences were termed polymedial* or transgressive. Besides the upcoming influence of structuralism (claude lévi-Strauss) and the new media sciences (Marshall Mcluhan), the aesthetics of information theory (Abraham A. Moles, Max Bense) promoted interdisciplinary practices. The concepts of a comprehensive cybernetics388 were targeted based on the interconnection of varying areas such as computer sciences, engineering, natural sciences, sociology and art.** A keystone of the representatives of cybernetics was to determine the hierarchy of an universal science. The cyberneticists, particularly Warren Mcculloch389 engaged and applied experimental epistemology.*** Max Bense considered cybernetics to be a “meta technique of the machine” and not as a tool for expansion or just an artificial limb that was specifically dedicated to mankind.390 At the same time, art was experiencing a conflicting alignment – striving for the dissolution of boundaries and expansion in artistic practices on the one hand, and reduction and concentration of these on the other. At about the same time the canadian psychologist Daniel E. Berlyne attempted to establish a neo-behavioral direction in psychology. Berlyne’s term new experimental aesthetics would not be officially introduced until the 1970s as a new empirical psychological aesthetic in an abstract. The goal is to open up a teaching with an emphasis on lust-based experiences. This suggestion of an aesthetic psychology was echoed in the actions of the artistic encounter with environments at that time. but also partially in the earlier Viennese Actionism. The older school of classical behaviorism was replaced by cognitive change as of 1956. With the legendary Symposium Special Interest Group on Information Theory at MIT in September 1956 the cognitive sciences were de facto founded. The wellknown German/American psychologist Ulric neisser’s key work Kognitive Psychologie (cognitive Psychology) appeared in 1967. In the psychological sciences in the nineteenth century, the interest lay primarily in the senses, perception, association, imagination and attention. In the beginnings of psychological studies, mental, cognitive processes al-

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* Terms such as polymedial or polyaesthetic are used similarly to terms such as intermedial, transmedial, mixedmedia or mixed-means in literature, theater and in modern music. Whereby with the prefix “poly-” not “many” is meant in terms of quantity but for multiple qualities. The concept formations with “poly-” were apparently constructed more often in the 1960s. Richard Kostelanetz is said to have created the word poly artist (1968) also termed the phrase mixed-means (-media). Richard Kostelanetz, The Theater of Mixed-Means. An Introduction to Happenings, Kinetic Environments and Other Mixed-Means Presentations (1968), Reprint New York 1980. See also the abstract of Marios Joannou Elia’s dissertation on the topic of “Zeitgenössische Musik und ihre Wahrnehmungsformen im Kontext von Polyästhetik und Polymedialität” (as of 2007 in the works) at the Music University, Vienna, http://www.mdw.ac.at/u pload/phd/Elia-MariosJoannou.pdf

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** Stefan Rieger attempts to explain how the basic concept of the virtual was derived and where its origin is through the theories of cybernetics. Warren McCulloch, Verkörperung des Geistes (1965).

*** McCulloch’s famous question that he asked as a student in 1917, “What is a number, that a man may know it, and a man that he may know a number ?” was picked up by Peter Weibel in 1992 worked into his computer LED installation at the Vienna IBM office building (Schuler, ed., Peter Weibel – Bildwelten, 190–191, 287).

ready stood in the foreground. In about 1930, the emphasis in psychology was placed on emotion, behavior and motivation as opposed to introspection.391 Research in the cognitive sciences that had essentially originated with cybernetics, continued in part the ideas of Wertheimer’s Berlin Gestalt theory, Koffka, Köhler as well as Kurt lewin’s field theory, and the older, so-called production theory of the Graz Gestalt school and Meinong. Witasek and Benussi were included as well.

Artistic Research: Alfons Schilling, Jeffrey Shaw, Peter Weibel

With the current theoretical and technical upheaval that opened the access to computer and video technology, the conditions of producing the artistic image changed paradigmatically. The previously “ontological” within the image appeared obsolete because image production was now generated by image systems. Technological image enhancement demanded and conceptualized other perceptual questions in dealing with virtual media (apparent motion and apparent corporeality). Artists also had to ask themselves these questions. A new abstract concept was required in aesthetics that could live up to the technological transformation and the loss of the ontological image. The moving image in media art is often seen as a form of contemporary art. Artist Peter Weibel suggested a new concept of possible aesthetic triplets, the moving image and digital art: instead of the classical triple terms of being (reality) – work (thing, stuff ) – truth (beauty, soul) the new aesthetic in media art and in art of the 21st century would be explained to the viewer as simulation – medium – fiction or virtuality – sign.392 In the first part of this existing work there would be an account on apparent motion and apparent corporeality with contributions from the history of science. The second part is dedicated to the art historical reflection of works that deal with artistic and exploratory questions on perception – with an accent on apparent motion or apparent corporeality. Specifically, the media work by three well-known artists would be selected: Alfons Schilling, Jeffrey Shaw* and Peter Weibel. All three artists belong to the first generation of media art. Instrument based vision and virtual perception remain in the foreground of all three artists. Each one of them has made explicit reference to historical-technological phases of development. The inclusion of historical sensory physiology and perceptual theoretical concepts constitutes the essential part of their long-term art production. Their thoughts were meant to construct “Maschinen der Wahrnehmung” (Machines of Vision)** with which, according to Weibel, the research on techniques of visualization that had begun in the nineteenth century could be continued.393

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* The media artist Jeffrey Shaw creates his works almost entirely in a team with artists, technicians, architects, programmers and so on who join forces for a project.

** With “Machines of Vision” the media artist Steina Vasulka describes a series of her installations (1973–1978).

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* In the magazine series Film Culture, a special edition appeared in the winter of 1966 with an emphasis on Expanded Cinema. A symposium in New York that same year (1966) was dedicated to Expanded Cinema: “The programs will explore the uses of multiple screens, multiple projectors, multiple images, interrelated screen forms and images, filmdance, moving slides, kinetic sculpture, handheld projectors, balloon screens, video tape and video projections, light and sound experiments.” (quotation taken from Jonas Mekas, ed., Film Culture – Expanded Arts (New York, 1966), December, nr. 43, 1)

Discerning Participatory Capacity and Phenomenological Narration: Jeffrey Shaw

In 1966, the Australian artist Jeffrey Shaw began staging successful public art performances, happenings and films in the expanded cinematic style.* What made Shaw’s film performances distinctive was that besides including musicians and performers, he included primarily the creative capacity of the audience. This direct participation and integration of the audience in art projects can be understood as an innovative form in twentieth century aesthetics. Interspersing and interlocking of various media into an artwork should be included as well. This expansion within the artistic presentation often leaves the stage or the restrictive art space in order to become an event in “public” spaces, or a happening or an activity. This expansion within the scenario combined with an increased input of the “stimulus intensity” factor which sometimes went to the point of downright emotional explosions, led to excessive and not infrequent prosecutions by the authorities such as was the case with the Wiener Aktionismus (actionism). Shaw’s multimedia art events allowed him to have an experimental and largely open sphere of artistic activity. It was here that he could primarily explore the boundaries of moving images, film and the possibility of mobile performance venue or projection surfaces. In his continuous filmstrip Continuous Sound and Image Music (1966), for example, the temporal sequence of pictorial perception for the individual sequencing of a film image was constructed (fig. 119). Animated black and white freehand drawings were featured. long before computer-aided image worlds could have been created, Shaw had already developed artificial landscapes, pneumatically-transparent objects for walking on the surface of water (1969), massive cloud objects (1970) that served as movie screens or inflatable multi-storied pavilions (1971) upon which the audience could sit on an airborne floor (fig. 120 a-e). PVc, which at that time had just been developed, was best suited for the sophisticated inflated constructions used in the Expanded cinema Performances such as Emergences of Continuous Forms (1966) or Movie Movie (1967)394 (fig. 121 a-c). PVc became more popular because it came in the form of sturdy folios and was easy to handle. Particularly because of its transparent nature, it could be perfectly combined with water, air

and the audience. Shaw’s early works of Expanded cinema were constructed together with the Dutch artist Tjebbe van Tijen who, like Shaw, had studied art in Milan. After 1966, the two worked intensively together. Even now Shaw cooperates with a team of artists and engineers and generally performs “live” and with the participation audience.395 For the artist the participatory and transformational aspect in a work is pivotal: Just as I love the friction between the real and the virtual, I also love the friction that ensues between a work that is my own and that which the audience can claim: it has also become partially theirs. I like this type of union with the audience. Traditional art has so few possibilities allowing this to happen and to be experienced. 396 Shaw’s works and those of his fellow artists are representative of many projects that caused a sensation at the end of the 1960s and beginning of the 70s: Stanislav Filko with his inflatable Kosmos-Environments (1968), hans haacke’s Sky-line (1967) or Gilles larrain’s Tubulaire (1969). Shaw and Van Tijen were not the only ones who worked with large, sensational objects and the participation of the audience. The artist Graham Stevens planned a pneumatic sculpture in order to intensify the audiences’ senses as early as in 1965. In 1968, Graham Stevens first displayed an enormous walk-on waterbed. With all of these events, the narrative, haptic, playful and interactive moments remained in the foreground. That means that the audience became a part of the events. Most notably such architects as louis Kahn, Buckminster Fuller or the young hans hollein adopted this new direction. They saw an opportunity of applying new technologies and creating with new materials as well as establishing a connection to modern sociological research. Shaw’s continuous testing of new materials that were used in construction such as chemo-technical vinyl or Plexiglas for roof construction can be explained by – among other things – his study of architecture. In his 1975 work Viewpoint* Shaw addressed the topic of perceptual illusion. This work consisted of a console with two optical observation windows whose shapes were reminiscent of historical colonnaded stereoscopes from the end of the nineteenth century (fig. 122 a-c). Two scenes are seen that visibly overlap perfectly. on the one hand, the viewer sees the room of the museum in real-time and on the other a constructed event that occurred in the past. The latter is shown through an automatic feed by two slide projectors as a projection on the screen on the opposite wall that no one else in the room is able to see. At times they are comic se-

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* This was in cooperation with Theo Botschuijver at the Musée d’Art Moderne de la Ville de Paris in Paris.

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* In his 1875 book on the perception of motion (kinaesthesia) Ernst Mach described the physiological observation that in the scope of his experiment on kinaesthesia and after getting out of the turning drum he suffered from the unusual perception of a doubled space. This ceased in his body shortly after the rotation of the device was stopped.

** Virtual Sculpture (1981), coauthor Theo Botschuijver, software by Larry Abel, and Memories of Certain Elements (1982) with Fabienne de Quasa Riera, software by Larry Abel, hardware by Charly Jungbauer and Tat van Vark (fig. 124).

quences, for example a museum visitor who prepares his bed and then lies down in it. In principle, two rooms and two time periods are merged into a single image. That means that two separate scenes are fused simultaneously on one screen. Showing an image of an event in real-time concurrently with an event that took place in the past was a basic goal in new media during the 1970s. What the new media were able to accomplish and what they were able to represent were still central themes. In this regard especially the approbations of the phenomenal and narrative aesthetic (also for media analytical themes) remained decisive in Shaw’s work. To a certain degree, this was a fallback onto Daniel E. Berlyne’s neobehaviorist approach of the new experimental aesthetic. In the course of the technological development and feasibility of Shaw’s artistic landscape, objects changed into images of purely virtual landscapes. The objects that appeared were illusory bodies that the viewer could change actually-interactively at will. The modalities of perception between viewer and virtual spatial objects led to an expansion of interaction or to the participation of the audience during the performance. Innovations within the arts developed, based on the foundation of knowledge in experimental research in which our psychological-physical perceptual system is able to experience and interpret apparent motion and apparent corporeality such as “actual” movement and bodies. At the end of the 1970’s Shaw worked with virtual projection in real space in that he developed a method of overlapping two concepts of space* like Virtual Sculpture** (fig. 123 and 125). Schilling drew stereo images with the help of a stereoscope and let them appear three-dimensional. he also created auto stereo images. Shaw experimented with computer-generated stereo images: actual spatial situations were superimposed with computer-animated projections. Just as with Schilling’s Seeing Machines (with arrangements of prisms or mirrors) a digital interface made visual access possible. In Points of View (1983) the viewer directed computer-aided image production on a screen with the help of two joysticks and a console (fig. 126 a-f ). With airplane simulator technology the user could change his virtual position on the screen/stage interactively. Everyday hieroglyphic ideographs acted as virtual fellow-players in the form of visual-moving signs. Sixteen soundtracks were also made accessible by means of the joysticks. The interactive computer installation was later presented with

two content-related enhancements. once, a text was delivered on the Falkland Island War, and the second time an open artwork was to be performed: sixteen people were invited to take part with their personal contributions so that the user could navigate between the individual dialogues. The strong tendency that Shaw had to express narrative situations is also obvious in the title of his work The Narrative Landscape* (1985/1995). This is an interactive audiovisual installation from which the viewer has access to a joystick in an elevated position (fig. 127 a-b). lyrics from Dirk Groenwald were audible. The novelty was that the viewer could zoom into the digitized images up to their actual pixel resolution. That which is described in spatial vision as Tiefenraumsehen (depth perception) led to a dissolved microscopic pixel-image in the depth-reflection of a digital image. In the 1986 interactive installation Inventer La Terre,** Shaw does not use a projection screen. The viewer looks directly into the inside of a console in which an optical system has been installed that consisted of semitransparent mirrors, a lense and a video monitor. Through the opening of the console the viewer can see a virtual image hovering in the actual room. handles on the console allow them to have interactive access to the virtual image in the actual room (fig. 128 a-d). The Legible City (1988–91) became Shaw’s most popular media art work: a real bicycle served as interface in order to activate the computer-aided presentation (fig. 129 a-c). The user placed their feet on the pedals of the stationary bicycle, and then a 3D image of city maps of Amsterdam, new York and Karlsruhe. The streets did not show buildings. In their place, virtual letters rose up along the road from which words and sentences could be created. Dirk Groenewald who had also penned Narrative Landscape wrote the accompanying text. After Shaw took over the direction of the media department in the newly founded center for Media and Art in Karlsruhe (ZKM), his interest in virtual immersion intensified. For Shaw it was essentially about an advanced continuation of Expanded cinema: to be able to create a new narrative form with digital, non-linear structures. A virtual environment could be created with it in which the viewer had options in interactive navigating through virtual image worlds. These appeared in 3D projec-

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* Software by Gideon May and Lothar Schmitt.

** Coauthor Walter Maioli (composer), Software by Larry Abel.

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* Jeffrey Shaw has been working at iCinema since 2003 – Centre for Interactive Cinema Research at the University of New South Wales, Sydney. His last cooperation in the continued development of the Project T_Visionarium (2002– 2009) again with the ZKM.

** Jack Massey, Conrad Lloyd Morgan, Cold War Confrontations: US Exhibitions and their Role in the Cultural Cold (Zurich, 2008) 178–183.

*** The spherical architecture of a semicircle was implemented by VanDerBeek in 1965 in Stony Point, New York. The formal motivation could be traced back to Buckminster Fuller who taught at the art school in North Carolina at the time VanDerBeek attended it.

tions and could – in a broader sense – be described as “interactive, immersive” visualizations. That means that the observer finds himself not as a passive recipient in front of an image-narrative but steers himself, as author, through the 3D-visualization. In order to study the new visualization techniques, a long-term study project Extended Virtual Environment, EVE was initialized in 1993. This continued until Shaw left the ZKM in 2002. The continuation was in Sydney, Australia, at the icinema (center for Interactive cinema Research).* The projection grounds were an air-inflated structure with a dome measuring 9 meters in height and 12 meters in diameter at the hub 397 (fig. 130, 131, 132). The inside of the “dome” became the projection surface and the observer had an interactive and largely moveable image selection to choose from. In the late 1950s and 1960s, the United States artists who had also developed Expanded Cinema introduced many experimental works for multiprojection performances. charles and Ray Eames had already used seven huge screens within a dome architecture in Moscow in 1959.** The group of American artists USco succeeded in using public performances with multi-media and cinematic effects. The experimental filmmaker Stan VanDerBeek worked most consistently with multi-screens. his intermedial art environment became known as the Movie Drome (1963–1965)398 and can be considered to be a crucial contribution to the development of the Expanded cinema. VanDerBeek described his multimedia presentation in Movie Drome 399/ *** as a “newsreel of ideas, newsreel of dreams, movie-mural, feedback, image library, kinetic-library” or “culture-intercom”. he saw the experimental form of Expanded cinema as a “tool” for global (non-verbal) communication and coined terms such as EthosCinema.400 Within the Movie Drome, the visitor was to experience – preferably in a reclined position – thousands of images of the 3000 years of art history (among others in the form of computer animation) from the ancient Egyptians to the present day on multi-screens. VanDerBeek, whose artistic origins were related to Surrealism with collages that appeared to be surreal, compared this intermedial flood of images to that of a particular magazine-collage. The basic premise for the presentation of this bombardment of images that Group USco and Gerd Stern or Stan VanDerBeek had conceptualized shed light on the futuristic prognoses of the 1960s. With regard to the developments of cybernetic theories in the field of digital computers, many scientists and avant garde artists assumed that one day the device

would take over the human brain entirely. This viewpoint presupposes that the cerebral area, the brain, is the central location in which all experiences reside. The cognitive-neurological interest in experimenting with perception psychology and sensory physiology that had begun in the nineteenth century had been discovered anew. This was not only the case in the sciences: an increasing number of famous artists* rediscovered the historical experiments as well. They recognized that light kinetic cybernetic art forms could be used as new options of narration to make pictorial forms move. The genre of film in particular seemed predestined to be expanded upon with innovative environments. This was the case with Whitney’s and Eames’s cinematic performance inside the architectural form of a dome. Early in the 1990s, Shaw continued with and expanded on VanDerBeek’s idea of the dome with new interactive computer technology. The research project EVE at ZKM which had run for such a long time, resulted in works such as The Telepresent Onlookers (1995) and The Web Planetarium (1998) as well as the project series T_Visionarium (fig. 133) that began in 2002.** For the work The Telepresent Onlookers two video projectors are placed in the middle of the cupola on a robot controlled by a swivel arm device so that the image could be projected in various locations throughout the interior of the dome by the rotating movement of surround projection. The two video projectors created stereoscopic images that the viewer could see as 3D-images through so-called polarization glasses (also known as 3-D glasses). The visitor wore a special headset with a position measuring device that could localize position and viewing direction allowing the video projection to be steered. The visitor could de facto steer the projection over the entire interior with his/her own line of vision. In principle, the viewer was largely in an enclosed interior but with the interactive telematics he/she could also be in the virtual outdoors. Because of the closed-dome architecture, the viewer experienced the immersion nature of many of the omnipresent TV-images much more intensely and was able to intervene in the established structure of the narrative image.401 By means of digital technology Shaw was able to produce a moving 3D image. Plateau had already considered this and referred to it in his notes on the afterimage, namely to find a technical method by which to combine Wheatstone’s stereoscope with his own stroboscope. The interactive immersive installation T_Visionarium emerged in two

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* Ben F. Laposky already showed electronically produced color images in 1965. That same year Herbert W. Frank began experimenting with oscillograms. In Germany Kurd Alsleben and Wilhelm Fetter created the first computer graphics in 1960. In 1965, the first digital graphic computer works emerged by Frieder Nake, George Ness, Michael Noll as well as – in the Bell Labs – by Kenneth C. Knowlton, Stan VanDerBeek and by the perception psychologist Béla Julesz. (Frank Popper, “High Technology Art”, in Digitaler Schein. Ästhetik der elektronischen Medien (Frankfurt/Main, 1991), 249–266.)

** Besides Jeffrey Shaw, Neil Brown, Dennis Del Favero and Peter Weibel were also involved in the T_Visionarium I and II.

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stages: T_Visionarium I (2003) and T_Visionarium II (2008–10). The T_Visionarium essentially provided the opportunity of editing a multitude of stories drawn from television material and viewing these in 3D on a 360° projection screen. The first version was implemented in the EVEdome. A databank was created in which the content fed on the content of the weekly television programs telecast at specific times from forty satellite TV channels. Using a remote control, the viewer could select key terms and other parameters such as patterns, colors and items from the search engine. Upon input, the system filtered out the corresponding picture from the databank and dispersed it across the entire projection surface of the dome. The user’s head movement with a head-TrackingSystem could also control the positioning of the images, and the images could be experienced in 3-D using polarization glasses. The formal image resolution that brought out a narrative event of the images explicitly selected for the viewer was in the format of a panorama picture. Shaw demonstrated this kind of artistic approach in his 1974 Diadrama in which 2000 slides were shown on a panorama type of projection surface. Beginning in 1995 – with the interactive work Place – a User’s Manual or also in 2000 with enhancements of Place as Place Ruhr – Shaw and his team of experts experimented with the concept of an interactive panorama image-environment (fig. 134, 135). The second version of T_Visionarium was carried out with the AVIE (Advanced Visualisation and Interaction Environment) technology. T_Visionarium with AVIE is the first 360° stereoscopic projection movie theater. one could do without the cumbersome head-Tracking System: the user just had to wear 3D glasses. A cupola was not used for the environment but rather a panorama projection surface in the form of a ring with a diameter of 10 meters. The 3D images were projected via 12 digital projectors (fig. 136). The participation of the viewer was the focal point for Shaw ever since he had begun working as an artist in 1965/66. In contrast to conventional linear storytelling of classic cinema, henceforth a highly individual narrative pictorial narrative ensued in the era of technological advancement. In which way technology influences the sociocultural aspect of viewing habits, Shaw demonstrated in other works such as The Golden Calf from 1994/95 (fig. 137, 138). A flat display monitor on a platform was connected to a computer by a long cable. The handy display monitor showed

a computer-generated calf. In order to see more of it, the viewer had to stop and perform a sort of cult-like dance with the little movable monitor in order to see the image of the golden calf. Depending on how one moved on the platform, the position of the calf changed. here the onlookers themselves were not reflected on the skin of the animal, rather they activated the projection of the digital calf with their dance-like movements. With this work Shaw foresaw the tablet Pc or the mobile telephone displays back in the mid 1990s. The forecasted daily dance around the digital calf, that is, around the mobile computer or communication device, was what Shaw expressed in a prophetic manner. Jeffrey Shaw’s works are exemplary for the techno transformation phenomena of our time in terms of highly developed pictorial presentation. In addition, it is very important to him to convey new forms of digital narrative through interactive, strongly haptic installations. The selection or new constructions of certain visual interfaces in his interactive installations always had a special position for him. Therefore it is not surprising that Shaw’s work has often become central in media and art theory and his relevant works on the topic are already considered to be classics of interactive art.402/*

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* The media philosopher Mark Hanser uses Shaw’s work as source to fortify his theory of media that is essentially based on Gilles Deleuze’s work L’imagemouvement and his reflections on Bergson’s theses; on the other hand, Peter Weibel considers Shaw’s work as possible instruction for how to deal with the device-complexity of (today’s) world.

Fig. 119 Jeffrey Shaw, Tjebbe van Tijen: Continuous Sound and Image Music, 1966

Fig. 120a Jeffrey Shaw, Theo Botschuijver, Sean WellesleyMiller: Airground Mattress, 1970

Fig. 120b Jeffrey Shaw, Theo Botschuijver, Sean Wellesley-Miller: Aqua Airground, 1972

Fig. 120c Jeffrey Shaw, Theo Botschuijver, Sean Wellesley-Miller: Cloud (of daytime sky at night), 1970

Fig. 120d Jeffrey Shaw, Theo Botschuijver, Sean Wellesley-Miller: Airground, 1968

Fig. 120e Jeffrey Shaw, Theo Botschuijver, Sean Wellesley-Miller: Cloud (of daytime sky at night), 1970

Fig. 121a Jeffrey Shaw, Tjebbe van Tijen, Theo Botschuijver, Sean Wellesley-Miller: MovieMovie, 1967

Fig. 121b Jeffrey Shaw, Tjebbe van Tijen, Theo Botschuijver, Sean Wellesley-Miller: Movie Movie, 1967

Fig. 121c Jeffrey Shaw, Tjebbe van Tijen, Theo Botschuijver, Sean Wellesley-Miller: Movie Movie, 1967

Fig. 122a Jeffrey Shaw, Theo Botschuijver: Viewpoint, 1975

Fig. 122b Jeffrey Shaw, Theo Botschuijver: Viewpoint, 1975

Fig. 122c Jeffrey Shaw, Theo Botschuijver: Viewpoint, 1975

Fig. 123 Jeffrey Shaw, Theo Botschuijver: Virtual Sculpture, 1981

Fig. 124 Jeffrey Shaw, Fabienne de Quasa Riera: Memories of Certain Elements, 1982

Fig. 125 Jeffrey Shaw, Theo Botschuijver, Virtual Sulpture, 1981

Fig. 126a Jeffrey Shaw: Points of View, 1983

Fig. 126b Jeffrey Shaw: Points of View, 1983

Fig. 126c Jeffrey Shaw: Points of View, 1983

Fig. 126d Jeffrey Shaw: Points of View, 1983

Fig. 126e Jeffrey Shaw: Points of View, 1983

Fig. 126f Jeffrey Shaw: Points of View, 1983

Fig. 127a Jeffrey Shaw, Dirk Groeneveld: Narrative Landscape, 1985

Fig. 127b Jeffrey Shaw, Dirk Groeneveld: Narrative Landscape, 1985

Fig. 128a Jeffrey Shaw, Walter Maioli: Inventer la Terre, 1986

Fig. 128b Jeffrey Shaw, Walter Maioli: Inventer la Terre, 1986

Fig. 128c Jeffrey Shaw, Walter Maioli: Inventer la Terre, 1986

Fig. 128d Jeffrey Shaw, Walter Maioli: Inventer la Terre, 1986

Fig. 129a Jeffrey Shaw, Dirk Groeneveld: The Legible City, 1988/91

Fig. 129b Jeffrey Shaw, Dirk Groeneveld: The Legible City, 1988/91

Fig. 129c Jeffrey Shaw, Dirk Groeneveld: The Legible City, 1988/91

Fig. 130 Jeffrey Shaw: EVD-Extended Virtual Environment (Dome), 1993

Fig. 131 Jeffrey Shaw: The Telepresent Onlookers, 1995

Fig. 132 Jeffrey Shaw: The Telepresent Onlookers, 1995

Fig. 133 Jeffrey Shaw, Neil Brown, Dennis Del Favero, Peter Weibel: T_ Visionarium I, 2004

Fig. 134 Jeffrey Shaw: Place Ruhr, 2000

Fig. 135 Jeffrey Shaw: Place Ruhr, 2000

Fig. 136 Jeffrey Shaw, Neil Brown, Dennis Del Favero, Matthew McGinity, Peter Weibel: T_Visionarium II, 2008

Fig. 137 Jeffrey Shaw: The Golden Calf, 1994

Fig. 138 Jeffrey Shaw: The Golden Calf, 1994

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* In 1955, the gallery Denise René showed Le Mouvement, and with it the path for kinetic art had been paved in Paris.

** Jean Tinguely (1925– 1991) had also grown up in Basel and had learned to become a window dresser. In 1960, he performed his famous Happening with a selfdestructing machine Hommage to New York in the courtyard of the MoMA. Bill Klüver gave him technological support. Klüver organized the legendary E.A.T. festival in New York in 1966.

Addiction to New Images: Alfons Schilling

The artist Alfons Schilling was born in Basel, Switzerland. As a teenager he underwent a psychological test, the so-called Szondi-Test, to determine what kind of career would be suitable for him. According to the results, his talents lay in the creative field, and the psychologist suggested he take up some sort of vocational training such as that of window dresser. At his father’s request, Schilling first completed vocational business school and bank training in Basel. In 1956 he moved to Vienna to study at the University of Applied Arts with Professor Bäumer. There he met Günter Brus and Walter Pichler who soon became his friends. he spent a longer period of time with Brus on the Spanish island of Mallorca and then travelled to Madrid and visited the El Prado Museum. In 1961, Brus and Schilling first exhibited together at the gallery Junge Generation Wien (fig. 139). Their abstract and quite gestural paintings touched on tachism and the informal. The young artists had already envisioned a continuation of an earlier action painting. Instead of tying himself or herself down further in Vienna as an artist, Schilling left shortly thereafter for Paris in order to break into an international, open and more diverse art scene. The newest trends such as kinetic art were more densely integrated and up to date there.* The new trend of opArt was presaged as attempting to become established in the expanding art world of the 1960s. Schilling met the Polish avant garde artist henryk Berlewi who resided in Paris. Because their studios were nearby, Schilling had casual contact with Jean Tinguely, an outstanding representative of kinetic art.** Schilling told him about his idea of experimenting with rotating disks, and Tinguely thought it was so interesting that he encouraged him to continue with it. In a personal conversation in 2006, Schilling continuously emphasized his urgent intention to create new images that had never before been seen. This explains his obsession with inventing new forms of expression in painting. Already prior to his stay in Paris, Schilling had constructed a rotating disk, which he wanted to paint – in accordance to the Futurist Manifesto – that supported a style of movement or a sculptural dynamism (Umberto Boccioni).403 Reinforced by the influence of the moving image

of kinetic art, in 1961 Schilling began having large circular canvases rotate aided by a motor driven mechanism while pouring buckets of paint on them in his studio. This was to de facto transform a kinetic sculpture (the quickly rotating disk) into a canvas or to move sculpture into a painting (fig. 140). With this Schilling was following the strongly proclaimed and popular expression of dissolution of boundaries of the static image by using rotating motion and centrifugal force. This was a popular idea in its day. It would be apropos to describe Schilling’s art as kinetic painting. And, similar to Duchamp’s Rotoreliefs, these picturesque works appeared to be an artistic answer to Plateau’s stroboscopic afterimages as well as to Fechner’s subjective color circles in the early stages of perception research of the nineteenth century. Despite the important expansion of his work, Schilling interrupted his art production for a short period of time. he had become convinced that pictorial art had reached its limits and that he as an artist had nothing new to discover. In the fall of 1962, Schilling moved to new York and took jobs here and there for artist friends. one of his employers was the well-known engineer Bill Klüver who was also the initiator of the festival E.A.T. 9 Evenings: Theater and Engineering (1966) which had taken place in the same building as the Armory-Show back in 1913. he assigned Alfons Schilling the documentation on film of all the performances and shows.404/* Soon thereafter, in the second half of the 1960s, Schilling began working artistically again. Fascinated by holography, he started working with this technology together with the scientist Don White. For Schilling the depiction of movement and space on a 2D surface was a challenge with which he would grapple for many years. When he researched the technological means by which to depict space and movement in a picture, he discovered lenticular grid photography that makes the viewer an “activator of the image”. According to Schilling: it is only with their movement around the depiction that the viewers stimulate the image into movement, and so “the picture becomes a complete picture” 405 (fig. 141). Schilling was impressed by perception research and especially by visual perception as well as the options that were possible through technology in terms of new visual devices. Through an acquaintance Schilling was afforded the privilege of using the famous Bell laboratories at night in order to be able to implement the devices and computers for his own artis-

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* More than 20 scientists, engineers and 10 artists were invited to work together for the event. Among the participating artists were John Cage, Öyvind Fahlström, Yvonne Rainer, Robert Rauschenberg and Robert Withman.

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* The little-known Scottish natural scientist Thomas Brown (1778– 1820) founded Consequent Associationism. Along with Berkeley, he can be included as pioneer in the theory of local signs. Here the right vision was always justified in connection with localization such as touch.

tic purposes. he was able to test his own experimental works there. It was there that he met the well-known perception researcher Béla Julesz and soon he immersed himself in the theories of stereoscopic vision. Schilling painted large-format images allowing the recognition of spatial objects on a 2D canvas with the help of a stereoscope (fig. 142 a-c). Julesz was impressed with Schillings paintings because he, too, was able to produce stereoscopic computer images but not in as comparatively short a time as Schilling. In 1974, Schilling drafted his first auto-stereograms, which allowed the viewer to see 3D figures without goggles. These were the socalled free visions (fig. 143). his numerous stereoscopic tests led him to the conclusion that spatial perception as well as the perception of movement is connected simultaneously in both space and time. With the help of masks he had made himself, he was able to bring about the separation of binocular vision (fig. 144 a-b). he experimented with a stereo-slide projector with which he could project two slides at the same time (fig. 145). According to Schilling’s theory, the eyes should be understood not as points of position but rather points of time, where the equation movement produces time = time applies. The Scottish philosopher and natural researcher Thomas Brown* had already derived human visual space from body movement.406 The movement followed in a chronological chain, “and space was nothing more than the associative connection of this sequence of movements.”407 Aided by a rotating projector with locking disks, he discovered the visual phenomenon that he had registered at the patent office in 1976 known as the Schilling-Effect (fig. 146 a-d). The rotation disks used had a certain similarity to the disks that Mach had used for his experiments on retinal stimuli in 1866/1868 (fig. 148).

Fig. 139 A. Schilling, G. Brus und O. Mühl in the exhibition, 1961

Fig. 140 Alfons Schilling: Rotation painting, 1962

Fig. 141 Alfons Schilling: Chicago Demo (Genet), Linsenraster-Fotografie, 1968

Fig. 142a Alfons Schilling: Stereo images with seeing device, Kunsthaus Zurich, 1979

Fig. 142b Alfons Schilling: Random-Pattern Stereo, 1977

Fig. 142c Alfons Schilling: Random-Pattern Stereo, 1973

Fig. 143 Alfons Schilling: Free vision, 1974

Fig. 144a Alfons Schilling: Mask

Fig. 145 Stereo-slide projector in the artists collection.

Fig. 144b Alfons Schilling: Mask

Fig. 146a Alfons Schilling: Schilling-effect, sketches for patent application, 1976

Fig. 146b Alfons Schilling: Schilling-effect, 1983

Fig. 146c Alfons Schilling: Rotation-Projector-shutter slider, circa 1980/81

Fig. 146d Alfons Schilling: Letter to the patent office, 1976

From Perception Devices to Seeing Machines

At the beginning of the 1970s, Schilling constructed experimental video cameras or projectors, frequently in cooperation with media artist Woody Vasulka. An example is the spider, a device for recording the parallactic displacement which occurs when shooting 3D integral photographic images or a sequence enlarger for lenticular photo images (1970). These constructions were the artist’s first perception devices or perception machines*/408(fig. 147 a-b). later Vasulka reported how impressed he was by what Schilling knew and his experience with binocular vision. he was also impressed at Schilling’s approach to opening up unorthodox new paths for perception with the help of visual devices. his friend’s experiments had strongly influenced his own work. For example, in constructing mechanisms that might analyze electronic images. I would urge you to examine his work on binocular perception where each artwork becomes a clear essay on the topic of understanding our mind. his other works, the ocular/optical constructions, are radical tools that challenge our consciousness as the property of perception of space.409 The more Schilling dealt with the cognitive sciences as they related to visual perception, the more significant they became to him. In 1969, he produced a series with his lenticular-photos of moving images The Falling Man (fig. 148). In it two different views of the same image appeared on a single photo. Although the figure is doubled, it looked like a shadow and out-of-focus, but the viewer is able to still briefly see movement. Whatever the viewer actually sees depends entirely upon what he is directing his attention to. “Perception is often most effective during the movement, ”410 wrote neisser, the pioneer of cognitive sciences. Even more striking is his comment: “Perception is like movement, a cyclical activity […].”411 Schilling also used the binocular parallel axis in order to create new stimulus patterns for the eye; by shifting the position of the eye, form, location and arrangement of the viewed objects. he studied optical illusions such as the Pulfrich-Effect412/**. he concentrated on historical visual devices and experimented with diverse optical positioning of lenses and prism goggles. In the 1970s, interior designers, geologists, architects and psychologists became very interested in the topic of spatial orientation. Such terms as cognitive landscape, introduced by Edward c. Tolmann413 (1948) while

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* Ever since the exhibition in Vienna in 1987 at the Museum of Applied Arts (MAK), Schilling’s optical devices have been known as Seeing Machines. The title of the exhibition was termed Seeing Machines by Peter Noever, the director at the time. (Conversation with Schilling, April 2006)

** The Pulfrich-Effect was discovered by the physicist Carl Pulfrich. It is of a swinging pendulum, which suddenly appears to circle when the eye is shaded.

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experimenting on cognitive maps in rats and men were used in all things concerning new urban planning. As of 1971, a series of 3D lenticular photographs developed that Schilling called Brainscape (fig. 149) which was synonymous with cognitive map. Spatial vision on a two dimensional surface – is what fascinated Schilling. In 1972, he constructed a stationary seeing apparatus called Little Observer, which he used to make binocular plotted rooms (fig. 150). With the help of a special construction of mirrors, his seeing apparatus Big Observer (1974) made it possible to see a combination of an apparent space and a real space at the same time (fig. 151). Schilling soon realized that he would not be able to attain a more enduring change in visual perception with the stereoscope. he therefore transitioned to constructing portable seeing devices with which allowed the user to move about freely as far as possible. The major change was not in the seeing of the images. Being able to walk around freely with the seeing machine on evoked a sort of flowing pattern with which the eyes could be saturated or with which to gain new information. Schilling’s classic visual devices such as the Little Wheel (1978), Big Wheel (1981), Little Bird (1978), Darkroom (1984), Light Pump (1981), Exhumed Bird (1985/1986) were all optical “devices” so-called seeing machines (fig. 152). Because of the new mobility created by the ability to carry the device around, the viewer gained not only a visual but also a special motor experience. his movement was not only determined by the weight of the heavy mechanism, but especially by the striking visual phenomena. By using angular prisms or by means of a special arrangement of mirrors, for example, fore and background become interchanged. The artificially induced visual space offered the viewer a new visual dimension. Schilling experimented a great deal with the variations of intraocular distance. The greater the distance, the more time the eyes required to adapt: more room became visible. Following this principle, one of his most important works was created on the hudson River in new York: Optical System (1983). With this huge spatial-stereoscope the intraocular distance was expanded to 5 meters in order to bring the viewed landscape of the hudson River from a distance of 5km to a distance of 120 meters (fig. 153 a-c). Similar to the experiments in the scientific labs, Schilling’s seeing machines generated artificial visual motor perceptual distortion, although it

was under different conditions than in a laboratory. The user of the machine or device was immersed into a foreign visual world. Everything that had appeared familiar until then could be turned around, switched or distorted. Distances and directions could no longer be clearly defined by the user/observer because the visual field received signals that did not coincide with the motor function or sense of touch. According to the results of the studies on the inversion goggles, one could hypothetically assume that with Schilling’s seeing machines, a certain familiar normality would set in after wearing them for a longer period of time such as for three to ten days. Around 1973, Schilling developed a video headset to simulate a subjective, partially virtual 3D-environment (fig. 154 a-b) with the aid of small monitors (cRT) that would be worn like a pair of glasses. The signals of two video cameras were transferred via cable and later they were supposed to be beamed via a mini-transmitter. The video headset was supposed to work with batteries to allow for free movement. Following the above example, Schilling was among the first artists to create the concept of an artificial virtual space. In his groundbreaking essay Electronic Space, dated March 1973, Schilling introduced new options of this electronic virtual space (fig. 155). With this the observer could visually experience soft space. What this meant is that with the help of electronic images it would be possible to constantly “switch” – for example the foreground would go into the background and vice versa. The viewer could actually see himself within the space, in real time as well. Proportions would be variable, images and films could be added and mixed, etc.414 Schilling also described a virtual artificial space. The technique, which he would have needed to implement his ideas, was not sufficiently advanced at that time, and a large part of the innovative intention to create a cyberspace stopped as a visionary concept. The term cyberspace would not be introduced for another ten years. An interesting parallel development occurred in the computer sciences shortly before that at the University of Utah. Ivan Sutherland developed a headset at the end of the 1960s. It was able to show computer-simulated 3D-graphics 415/* (fig. 156 a-b). At almost the same time experiments were being conducted in psychology with electronic seeing prostheses created for the blind (fig. 156 c). A significant reason for his intense preoccupation with seeing and for the construction of seeing machines was the assumption that our vision had

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* Schilling did not receive this important piece of information on Sutherland’s research from the 1960s until he read Peter Weibel’s essay Anotomie des Sehens. In this connection one should also mention Morton Heilig’s “Sensorama” (1961). This early device could be viewed as the first head-mounteddisplay. Heilig had already begun working on the concept for this multi-sensory machine in 1956.

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* In connection with the inversion goggles, Béla Julesz goes into detail in his 1971 writings on the marked similarities of his own trials with the goggle trials made by Ivo Kohler.

become dulled. he doubted the receptivity of our vision because it had become “exhausted” by the flood of digital images. he compared our eyes with an old television set.416 our eyes had been overloaded and brutalized […] like when one looks at the sun for too long and one loses the ability to see after a while. It seems as if something like that has occurred. As a painter, one is particularly aware of that, in the midst of this jungle of imagery. It is clear to me that the naked eye has arrived at its end. It has become immune. It is no longer capable of insights.417 This fundamental loss of vision was close to being apocalyptic for him. This deep pessimistic reason explains his quest for new possibilities with which to revive the eye. In the process of his experimentation, he also became aware of tendencies that aimed at getting rid of the eye completely. For example, when visiting the Very Large Array (1986) the American radio telescope in new Mexico on which images of exoplanets of other sun systems in the universe could be created with the help of earth movements. Instead of images only digits were transmitted. The researchers in charge only needed conventional imagery in order to collect research funds. Actually, the numerical images sufficed for their interpretation. This development elicited the following astonished pronouncement from Schilling: “That is downright madness – they no longer need any eyes.”418 historically scientific concepts from the nineteenth and twentieth centuries were transferred to the contemporary art scene. Perceptual devices such as Mach’s optical square, Stratton’s inversion goggles or helmholtz’s telestereoscope could have been the inspiration for Schilling’s Augenverschieber (Eye Shifter, 1974), Raumumkehrer (Room Reverser, 1974) or Optisches System (optical System, 1983) (fig. 157 a-c). he impressed the scientist Don White or the famous perception scientist Béla Julesz 419/* with his profound knowledge of binocular vision. But Schilling still retained a high artistic autonomy for himself. he influenced many artists, from media artist (Woody Vasulka) to painting (Damien hirst) with his accomplishments on perception.

Fig. 147a Alfons Schilling, Woody Vasulka: Spider, 1970

Fig. 147b Alfons Schilling, Woody Vasulka: Sequence-Enlarging device for lens grid-photos, 1970

Fig. 148 Alfons Schilling: The Falling Man, 1969

Fig. 149 Alfons Schilling: Brainscape, 1971

Fig. 151 Alfons Schilling: Big Observer, 1974

Fig. 150 Alfons Schilling: Little Observer, 1972

Fig. 152 Alfons Schilling: Seeing Machines, 1978–1986

Fig. 153a Alfons Schilling: Optical System, 1983

Fig. 153b Alfons Schilling: Construction sketch of Optical System, 1983

Fig. 153c Hermann Helmholtz: Telestereoscope, 1860

Fig. 154a Alfons Schilling: Sketch of Video-Head-Set, 1973

Fig. 154b Alfons Schilling: Video-Head-Set, 1973

Fig. 155 Alfons Schilling: Essay on Electronic Space (page 1), 1973

Fig. 156a Ivan Sutherland: Head Set, 1966/67

Fig. 156b Ivan Sutherland: Head Set, 1966/67

Fig. 156c Paul Bach-y-Rita, Tactile vision with a TV-camera, 1969

Fig. 157a Alfons Schilling: Eye Shifter, 1984

Fig. 157b Alfons Schilling: Eye Shifter, 1984

Fig. 157c Ernst Mach: Sketch of an angle mirror, 1866

Visual Test Situations between Experiment and Theory: Peter Weibel

Peter Weibel embodies a type of artist that does not fit into any popular category. he can most likely be described the way Paul Feyerabend identified him based on the critical academic concept of “against methodological constraint”.420As a result of similar considerations, Ernst Mach had already introduced the concept psychophysical parallelism*as a scientific exercise in which the same object would be examined over and over again but from the perspective of various disciplines. According to Mach, this approach alone could secure comprehensive and profound knowledge of a single object being researched.** The physicist Feyerabend expanded on this concept to create a learning program that would prohibit any sort of methodological constraints. Peter Weibel had been working for close to fifty years on his open work, as he himself describes it. characterized by consistent plurality, his work evades any stylistic analysis and is not sufficiently accessible to any kind of conventional scientific methods pertaining to images. Too many stylistic fractures in non-style and too many different forms of media characterize his work. The artist and theoretician Weibel is generally categorized in the field of conceptual, experimental and epistemically oriented media art. Peter Weibel is among the first protagonists of the above art form who captured the canon of problem constants after 1960.*** In the end, Weibel’s relentless preoccupation with content ultimately led to the development of a very advanced stylistic moniker that vacillates between critical-rationalist issues and recurring aesthetic forms. The artist remains focused on much more that critical-rational issues than on recurrent aesthetic forms. The implementation of the latest and most current forms of media technology – as soon as they were accessible to him, from film to video to interactive computer-art and web-art – accelerated the development of the problem of consistency to a certain extent. Technical media afforded Weibel the prerequisite for the implementation of his ideas: From the beginning, technology has only helped me to deal with aesthetic and cognitive challenges more precisely. Because of that I didn’t stick to one form of technology. For me it was always only about the idea, and that is why I only used media in order to allow ideas to unfold. I was forced to learn the ropes of each new form of technology so that I could enhance the contextuality and the participatory interactive aspect of a work 421 (fig. 158).

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* The formation of the concept can be traced to Theodor Gustav Fechner who had recognized the parallelism of body – soul – challenge. Fechner preferred the term identity-aspect however. Mach discovered the term later for his theory of cognition and distanced himself from Fechner’s metaphysical background because of his own positivistic attitude. (Mach, Die Analyse der Empfindungen, 50).

** Mach aimed to establish a connection between the psyche and the physique as a “necessary prerequisite of precise research”. (Mach, Ibid., 51).

*** At the heart of Weibel’s attention are not recognizable, stylistically formal characteristics but rather fields of discourse with the constancy of multiple problems. A few years ago I became convinced that Weibel’s works could only be characterized by the term problem constants. I would like to revise this viewpoint. In the meantime there are certain formal, stylistic and material constants, which have become particularly visible in the vast number of his media works.

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* In the essay Materialien zu den Filmen (1974) Weibel describes himself as a modern poet because he uses modern communication media in addition to language. His first monograph (1982) appeared under the title Mediendichtung.

Weibel ultimately obliterated any trace of his own personal stylistic preferences and the concept of consistency, present throughout his entire creative work. Retrospectively, the fanned-out nature of his complete works nonetheless reveals throughout aesthetic and formal consistency. This is true particularly in regard to his preference for certain materials such as common objects made of plywood, glass, books, mirrors, etc. as well as the use of distinctly geometrical fundamental forms. A prominent example for this are the formative cubes. countless works are based on cubeshaped bodies upon which Weibel projects images and texts, as well as objects using neon lights Lichtkubus (cinekubus, 1974) painted cubes Wasserwürfel (Water cube, 1988), or interactive cube objects Cartesianisches Chaos, 1991, Weltwürfel (World cube, 1992), which would appear on the wall or on a screen Gesänge des Pluriversums (Songs of the Plural Universe, 1986–88). cubes (cube shapes) serve as a base for objects, at another time as recursive shapes that are plunged into objects. Prior to the era of flat screen televisions, Weibel often used the box-like shape of older TV-sets, with the object forming a frame for text and image messaging or even clouds of smoke from the cigarettes of a fictitious news broadcaster or as an object transformed into a non-functioning TV-aquarium filled with water. The titles of his works, such as Wasserwürfel (1988), Box Man (1987), Weltwürfel (1992) or Music-Cube (Music-Board, 2011) point unequivocally to his preferences. In addition to these, he also chose other geometric forms such as building blocks, or rectangles or grid-like bars that pervade his pluralistic universe of images as basic kit-like construction modules. Above and beyond that, since the 1960s Weibel has grappled with the human sense organs and their performance (seeing, feeling, speaking, hearing, smelling and tasting). Weibel’s excellent physiological and psychological knowledge as well as his interest in scientific experiments on cognitive abilities can be traced to his studies of medicine and physiology (1964–1967) as well as to his studies in mathematics (1967–1975). his very first works originated in the field of experimental literature and conducted investigations based on linguistic themes. As a result of first publications, he gained the reputation as being an author* and literatureand film-critic.422 In addition to his own experimental poetry, he often sympathized with avantgarde and anarchistic tendencies. The descriptive expression Wiener Aktionismus can be traced back to Weibel. his first book of materials, a pictorial compendium of images on Wiener

Aktionismus,423 is to date a unique testimonial of this significant movement in the 1960s. The utopian-like projects of this time period were witness to the influence of mass media researcher Marshal Mcluhan and even more clearly of cybernetics, which would later transition into the cognitive sciences. Weibel evidently struggled with the writings of the cyberneticist Max Bense in the mid 1960s. In the publication Werkstatt Aspekt 2 Peter Weibel came out with experimental poems and prose as well as a programmatic text on avant garde art and mass culture. here he quoted Max Bense in connection with art and cognitive interests: “concrete poetry is interested in intellectual-experimentational knowledge”.424 A central theme in this early text is the positioning of artists in mass culture and mass consumption within a capitalistic economic system. What is striking, according to Weibel, is that mass culture equalizes all products in that they retain the character of consumer goods. The common market is the supermarket […] Today the artist becomes an advertiser […] his artistic universe is the poster world, the world of magazines and consumption: he has to go into mass marketing. he does not feign individualism, neither in its creation nor in its reception […] he knows his work is a product. Solely the artistic complexity of his work sets it apart from mass-produced items and perhaps exposes the shark in the swimmingpool.425 In the first stages of his project series with interfaces for sensory perception were his works Information Unit (1967), a razor with multifunctional potential (fig. 159). Besides being a razor, the device was also a radio, control system, camera, walkie-talkie, speaker, TV and spy-pen. Weibel archived depictions of various modern everyday communication media from technical magazines. he would then introduce them as New Invention (at least as a concept) with his own, newly created captions and instruction manual. In addition to the enhancement of their technical possibilities, these new devices were also intended to serve as multi-sensory expansion like “Pillen”-Film (1968), Radiopille (1969), Amauroscope (1969) or Lichttelefon (light Telephone, 1969). The basic idea behind Filmbrille (Film Goggles, 1967), eyeglasses frame with two projectors mounted on them, was a sort of (physiological) canvas upon which the representation was projected directly onto the retina. For Brille als Welt (World as Goggles, 1967) the glasses were fitted with microcomputers. In an individual selection of images, of the worlds, everyone was to program

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* It has been reported that there were violent disputes between the two artists because Pichler claimed the concept for “Redehelm” for himself without Weibel’s consent. In 1982, Weibel wrote: “In the spring of 1967, I talked to Walter Pichler about experiments in art and technology at a party. I told him about my desire to have (own) a reading helmet that was equipped with a microphone, speakers, an amplifier, batteries, a spotlight, radio, magnetophone etc. It should make me independent of the environment and the public. A sort of literary guerilla-fighting-suit or a protective helmet made out of aluminum for mass events. When I returned to Austria from a working trip to Sweden, Pichler was in the process of preparing his exhibition at the Galerie nächst St. Stephan. It was there that I found this concept that I believed to be mine, being presented as ‘kleiner raum’ in a reduced manner. After an argument, Pichler finally wrote under the title of the object ‘for Peter Weibel’ at the opening of the exhibition.” (Quotation taken from Peter Weibel, Mediendichtung), 187.

images selected from his own personal world. With Distanzsinne (Sense of Distance, 1969) fiber optic cables were used as eye-tubes. Films were projected on the ends of these tubes, and these gave the user instructions. Weibel had conceived of these highly technological, linked communication forms in 1967/70, which later actually became part of our everyday lives: every human is connected by a multitude of such fiber optic cables with every thing he needs (cities, people, landscapes, etc.). Through these he can see whatever and whenever he wants. A communication system with fiber optic cables can transport a thousand times more information than a few telephone cables 426 (fig. 160, 161, 162, 163 a-b). His first plans for the Redehelm (Speaking Helmet, 1967) were executed – without Weibel’s consent – by Walter Pichler 1967/68 as Der Kleine Raum (Small Space).* After Redehelm (Der Kleine Raum) Weibel designed Medienlunge (Media Lung), implemented in 1974 (fig. 164, 165). All of these projects, partially visionary ideas stemming from a medial extension of the sensory organs aided by apparative interfaces, were ultimately supposed to become data-gloves and data-suits had they actually been created.** For the work Das Magische Auge (The Magic Eye, 1969, in cooperation with Valie Export) the canvas was equipped with light sensors and so, when the viewer walked past it, it was activated, and served as an eye for movement and tone (fig. 166). In this work, Mach’s famous essay “Wozu hat der Mensch zwei Augen?” (1866) can be heard like an echo, and up until now it had received only very little attention in Weibel’s artistic work.427 The reference to Mach is made clearly “audible” with Weibel’s song Entzweit (1981), Hotel Morphila Orchestra: I have two hands. I have two ears. I have two feet. I have two eyes. I see through two eyes with dismay and diremption, With one eye the half, with the other, the other half. I am divided. I have two lips. I have two kidneys. I have two lungs.

I have two balls. I walk on two legs towards the separation. Left and right my arms hang from my shoulders. I am, I am, divided. I take in two images of the room with two eyes. I? the latent objects with two arms. I see through two eyes with dismay and diremption, with one eye the half, with the other, the other half. I am divided. I float with the rivers. I fly with the clouds. My lips fly upwards. My feet fly downwards. I float with the eyes with dismay and diremption. I fly with the trees. I sit on the clouds. I am divided.* Besides the physiological concepts on interpreting the sensory organs and tools, a critical discourse ensued about the new film and new movie theater. Peter Weibel was not satisfied with Peter Kubelka’s definition at the beginning of the 1960s: “The film’s location is the screen”.428 According to him, the location for a film is on celluloid, but even this was up for discussion. When he was a medical student and experimental poet, Weibel began producing his own films according to his own concepts (1965). During a work-related stay in the summer of 1967 in Sweden, he adopted the term expanded arts (1966) from a special edition of “film culture”. It gave him the fitting definition of his artistic function in the field of film: more precisely, expanded cinema.** In his first expanded movie Weibel projected Welcome (1965–66)***, a film on his body**** and on the surrounding walls. Welcome can be regarded as an early work of Peter Weibel. The film initiative was shown twice during the international Symposium DIAS in London. In place of the soundtrack two records with interpretations of pop culture (Ray Charles, What I Say and The Everly Brothers, Suzie Q) were played as well as speeches given on the program. The film, a montage, showed cityscapes of Stockholm as well as linguistic structures with writing and letter images. In later performances of Welcome even scientific teaching films on how Weibel’s body worked

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** Weibel seemed to be most fascinated by the physiological binary arrangement of the organs and body parts such as lungs, hands, ears, lips and eyes.

* The song text was published years earlier as a poem in the Literaturzeitschrift Manuskripte, 40/1973. 38. Mach’s reflections would also prove significant to Weibel in his work on the topic of the sense of self.) ** The special edition had appeared just months earlier in New York, in December 1966. It therefore seems obvious that the special edition was already in circulation in certain art circles in 1967 in Sweden and not, as sometimes mentioned, in the summer of 1968. *** Welcome was filmed in Sweden in the summer of 1965 and cut in the winter of 1965/66. **** It was only in the summer of 1967 that Weibel had heard of the experimental films made by the American painter and filmmaker Robert Whitman, who already began projecting movies on the human body as a screen starting in 1963.)

Fig. 158 Peter Weibel: Work memo “Meine Kunstphasen”

Fig. 159 Peter Weibel: Information Unit, 1967

(my art phases), circa 1986

Fig. 160 Peter Weibel: Pillen-Projekt-Film (pill-project-film), 1968

Fig. 161 Peter Weibel: Radiopille (radio pill), 1969

Fig. 162 Peter Weibel: Amauroscope, 1969

Fig. 163a Peter Weibel: The Light-telephone, 1969

Fig. 163b Peter Weibel: Concept of a psycho-physical interface such as distance sensations among others, 1969

Fig. 164 Peter Weibel, Walter Pichler: Redehelm (talking helmet), 1967

Fig. 165 Peter Weibel: Medienlunge (media lung), 1974

Fig. 166 Peter Weibel, Valie Export: Das magische Auge, (the magical eye), 1969

Fig. 167 Peter Weibel: Welcome, 1965/66

Fig. 168a Peter Weibel: way way out, 1968/2007

Fig. 168b Peter Weibel: way way out, 1968/2007

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* In the 1982 publication, the date of the premiere is listed as January 13, 1967. A print of the program is in Peter Weibel: Das Offene Werk, (ostfildern, 2007) 552.

** The following email from Peter Weibel Sent: Friday August 12, 2011 at 22:35 To: Romana Schuler Regarding: Re: Welcome and Announcement Dear Romana, I am glad to see that we have finally found the right way of writing: Ray Charles and the Everly Brothers Susie Q. The film Welcome was actually performed in London in 1968 and in fact it was just like on the program documented as intermedia at DIAS. The film is an installation film with images of Stockholm. Not only the writing and letter images but also other urban images. The film was shown again in the winter of 1965 in Vienna where Peter Kubarik [sic. Kubelka] saw it but more or less rejected it especially because of the pop music that I played live as a record. In London it was shown at the same time as a performance by Mühl at DIAS. There the film was projected rotating on the walls and on my body but also on another day of the festival at another location as movie. At the Galerie nächst St. Stephan in 1966 there

were projected. It was then that the duplication of objects already played an important role – filmed grass is projected onto real grass. Because of ambiguity, a complete understanding of the terms was not always possible (fig. 167). Peter Weibel’s first public film event took place in a room rented at the Palais Palffy on the 26th/27th of January 1967*in Vienna with Nivea and Welcome. Just like at the DIAS-Symposium in London, image and sound were not presented together but separately.429/** Originally, for financial reasons – making a movie with a soundtrack was more expensive – Weibel substituted a recording for the soundtrack that was played along with the performance. Thus he also created the desired disillusionment or deconstruction for the new avant garde movie, the expanded cinema. The terminology for this performance was generally very vaguely defined. Happening, action painting, performance, lectures, direct art, intermedia, multimedia performance, environmental art, object poems, art in fusion or total art etc. circulated among the Viennese artists in an attempt to classify how this art should be defined. In his so-called environment-film way way out (1968) Weibel was ahead of his time with his idea of a virtual cave, even before the artist Dan Sandin began developing his first concepts for a cave in the 1970s. On all four walls and following precisely defined chronological parameters, four different images of animals, machines etc. were projected. These images and their duration were characterized by their respective ability to move: a snail, for example, that moved along slowly. In the final theme a rocket took off and flew about on all four walls around the viewer, who was standing in the midst of the action. A loud shout was heard over a loudspeaker screaming: “Out, out, out …” *** (fig. 168 a-b). Weibel had already broached the issue of experimental-linguistic writings, as to how the realities of the linguistic world might cover or might not cover his artistic concepts of the object or image world. He continued in this vein in his sculptures according to the motto: Everything is media poetry, for example, in his writing-light-sculpture Der Zwang zur Identität (Forced Identitiy, 1979/80).**** The movement of the wind correlates to a flash of light in order to show a new relationship between language (text) and sculpture (object). The experimental psychologist and philosopher Franz Hillebrand, who had also been concerned with identification mechanisms, described a similar example using an illuminated

advertisement for a movie in his 1922 publication on the theory of stroboscopic movement. The successive lighting up of the individual letters of the work movie (Kino) created an optically movable alphabet and could trigger the association of the term movie together with the movement of film images. The meaning would experience a variable way of reading: “movie” would be conceptually defined in the form of a written image as well as through a moving image.430 The optical impression described by Hillebrand, which was evoked by an electric timer, was comparable to a certain extent to the light installation Der Zwang zur Identität (Forced Identitiy, 1979/80) by Peter Weibel. By way of the successive illumination of the individual letters and words WIND the movement of the wind was metaphorically perceived in a light sculpture. At the same time a projector showed images of destroyed homes on the wall of the exhibition room. Additionally, a slide image of houses destroyed by wind was also projected on a wall of the exhibition room, following the illumination of the letters. An attempt to visualize the movement of the wind, its destructive impact was additionally displayed as well. With the successive movement and the transformation caused in the environment the light sculpture generated an expanded identification of the natural phenomenon of wind (fig. 169).

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was a little performance but in January 1967 at the Palais Palffy, just like at the Forum Stadtpark the film was shown as a projection on my body. Here the speeches were in French, English and German. In London my speech was of course only in English. If it was shown in 1968 in Cologne I don’t know at the moment.The film is now here with me in Karlsruhe. The film to listen to (Hörfilm) Hör Zu is an expansion of this projection practice. For the multi media show, I chose films like films of operations that I projected onto myself. An example is in my intermedial change on Mc Luhan. Here I also projected films onto the wall and on myself. As well as for my performance in Düsseldorf Cream Cheese. I checked out a large number of films from the British Council where Mr. Kronberger was the head of the film rental and archive. In 1968 I then extra recorded one and then a record in order to project it on my back with life text or music from a record. The photo in the open work is not from 1968 but from later. The photo is posed and comes from Valie Export from 1971/72. With kind wishes for your work. Peter

*** The concept with the images of a snail and to

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a rocket was presented in the magazine Film (see Peter Weibel, “Expanded Cinema”, in Film, Nov. 1969); A (very modified) realization of the original concept was shown at the exhibition MindFrames: Media Study at Buffalo 1973– 1900 at the ZKM Karlsruhe in 2007. **** Weibel created several variations of the light installation “Zwang zur Identität”. In a sketch he named the work also as “Identität der Bedeutung” (Romana Schuler, ed., Peter Weibel – Bildwelten, 65).

Fig. 169 Peter Weibel: Forced Identity, 1979/80

The Observation of Observation in Peter Weibel’s Work

After the mid 1920s, a new holistic worldview arose based on the new and developing theory of quantum mechanics. The question of detailed substantiation and interpretation concerning issues of the viewer were no longer reserved for scientific circles but also became open to popular scientists, allowing their participation in these problems. As a result of cybernetic theories, telepresence became increasingly important at the end of the 1950s. The first development towards an aesthetics of information also essentially rested on cybernetic discourse. Art would serve not only as an exchange of information but would become communication or would be communication based on the concept of feedback. As such, the relationship between a viewer and an artwork would become even more pronounced. Already in Renaissance art there was a rediscovery of a central perspective already familiar in that the reception of an image was very much dependent upon the viewer’s literal standpoint. legendary expressions such as I am in the picture (Jackson Pollock) or I am an artwork (Timm Ulrich) point directly to this connection between viewer and work. They also prompted Weibel again and again to theoretical considerations and artistic interventions. Especially his numerous works with morphing effects on the topic of his own identity should be considered in this light: video cross fading of his own self-image with depictions of the painter and mathematician Piero della Francesca or the poet nikolaus lenau (fig. 170 a). But works such as Ich als Hund (I as a Dog) or Selbstbildnis als Frau (Self-portrait as Woman) (fig. 170 b) etc. addressed the issue of switching from self-observer and viewer-standpoint, just as Jackson Pollock had introduced at the end of the 1940s in what was termed Action Paintings. As a result of his introspection* and the unstable or construed identity, Weibel began experimenting with the observation standpoint within closed systems based on model worlds. In his video The Endless Sandwich (1969)431/ ** the observation of the observation is presented by way of an endless chain of images *** in a series of identical looking model worlds. The Endless Sandwich can be considered as one of the earliest examples in his series of video pieces about the inner observer, or the topic of interfaces worldwide.**** The process-like arranged image scheme appears to

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* Building theories and topics on introspection as well as Artificial Ego (Valéry, Rimbaud) in connection with the topic of observation or even also quantum mechanics (Bohr, Heisenberg, Pauli and Schrödinger) fascinated Weibel since high school.

** The work was first shown at the First International Underground Film Festival, Arts Lab, London, September 1970, and in the TV program Impulse (Hans Preiner ed.) on Austrian television ORF. Impulse number 7 (29. 6. 1972) and Impulse number 42 (9. 12. 1974) (repeat).

*** Weibel compared the viewer as being one in a measuring chain, as a part of a whole chain of observers.

**** Up until the end of the 1980s, Weibel saw two clear aspects in his work The Endless Sandwich: “Two moments characterize this piece: the first in time, the second in mapping/picturing. A specific process is (virtually infinite) repeated and reproduced until it is finally reduplicated. The real process and the reproduced process are finally one; function (process) and content (image) are mapping

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constant: this is the sandwich character of every picturing process […]” (quote taken from Peter Weibel, “The Endless Sandwich”, Österreichische Hochschülerschaft, ed., Peter Weibel, Peter Weibel. An Annotated Videography 1969–1976 (Innsbruck, February 1977). After he had later discovered the theory of endophysics it is what gave him the explanation for observing endless model worlds (Weibel, “Virtuelle Realität oder der Endo-Zugang zur Elektronik”, in Florian Rötzer, Peter Weibel, eds., Cyberspace. Zum medialen Gesamtkunstwerk, 39.

* It takes 6 times until a black image appears.

** The British experimental psychologist Kenneth J.W. Craik probably was the first to postulate at the beginning of the 1940s that the mental functions of the brain could be explained with the example of an adding machine. Allen Turing who dealt with computation theory published similar ideas a few years later. His work Computing Mechanisms and Intelligence (1950) appeared five years later, after Craik had died.

be simplistic yet conceptually, it is ingenious: a viewer looks at a TV screen and at the same observes the finite model world of a viewer in front of a TV on a monitor, similar to a finite feedback loop. Suddenly, on the monitor that is located farthest away, an image interference occurs. The actual viewer gets up and tries to adjust something on the monitor in hopes that the image will return to normal again. The same scene then takes place with the next “inner” observer or viewer until repeated sequences arrive at the last viewer who is also affected by the already familiar static on the screen (fig. 171 a-c). This chain of onlooker-images takes on a hierarchy of viewers ranked from outside to inside and can perhaps best be explained with the principle of the Russian Matryoshka dolls in which a larger doll contains a smaller doll which contains a smaller doll and so forth. A very similar approach is presented in Weibel’s schematically applied work Time and Tense in Picture Processing oder Abhandlung über das Ende der Welt (1970). It is not a human who is looking at an outer system at the next smaller world but an image device “watches” or a finite image process is documented: An image of a daily newspaper is projected on the wall and photographed with a Polaroid camera and it is photographed with a Polaroid and projected again and again and photographed etc. In the end, the image on the screen is a completely black image because of the continued lack of definition.432/* Using video systems was an adequate new medium for the young artist and math student of that day to comprehend the processes of quantum mechanics or to follow up on the topics of quantum physicists. And in that way also to conduct his own experiments such as on determinism of natural laws. Based on Kenneth J.W. craik’s publication which appeared in 1943, The Nature of Explanation, Weibel dealt with the problem of whether natural processes could be computed by algorithms. Die Eroberung der Natur (The nature of Explanation, 1973) (fig. 172) was the title of Weibel’s video performance with which the scientific quantum experiment was intended to illustrate the indistinguishability of pool balls.** It could also be interpreted as an hommage to Kenneth craik.*** The primary intention of the video performance, though, lay in the prediction of the movement of the balls: Weibel’s hand attempted to follow a pool ball on screen.433 Aided by a video recorder, Weibel was able to stop the phases of movement of the balls and analyze the course of this movement in individual images on the screen.

The manner in which Peter Weibel worked through the complexity of the question of observation, based on natural scientific theories of quantum physics and later particularly on the perspective of endophysics, has already been documented and proven on many levels.434 The influences of empirical sensory perception research in the nineteenth century, especially Mach’s on introspection and which are noticeable in Weibel’s literary, artistic and theoretical work since the mid 1960s * have only been afforded rudimentary consideration. This is true even though direct reference would have been available, as is clearly shown in the closed circuit video installation Beobachter der Beobachtung: Unbestimmtheit (observation of the observed: Uncertainty, 1973)** Three monitors and three video cameras are set up in a circle (fig. 173 a-c). The viewer, who is in the closed circuit, is recorded live and appears simultaneously on the monitors. he is able to move around as much as he likes, turning as often as he likes. Regardless of what he does, he will always and only see his own back on the screen. Similar to the idea of never being able to see our own face without a mirror, we cannot recognize our own backs with our physiologically perceptual functions. The internal observer cannot perceive the distortion. only the person standing outside the area being filmed can observe the inner observer in an undistorted state. Self-observation remains fragmentary unless we are aided by visual devices such as mirrors, photography etc. which allow an outward expansion of the limits of our perception. clearly that is why Weibel hoped, like Mach, that only the linking of self-observation and physics makes any sense. Weibel was apparently in a position to recognize, as Mach once had, that only the connection between self-observation and natural sciences (physics) makes any sense: Self-observation alone, without the help of physics, could not have directed the sensory analysis. Philosophers often unilaterally overestimate introspection, psychiatrists often unilaterally overestimate the physiological analysis, whereas, in order to achieve any complete success, a combination of the two is indispensable.435

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*** According to the scientific theory that was based on only one single ball, the prediction of chance can be determined by means of one single model.) * When he was 18, Weibel already became acquainted with Mach’s writings. He came upon it in Lenin’s lectures on Materialism and Empirio-Criticism within which he criticized Mach. (conversation with Author, July 2011)

** This work was premiered at the 1973 Trigonale 73 in Graz, Austria. As far as I know, the installation was shown again as a reconstruction in May 1995 in the exhibition falsch verbunden at the Hamburger Kunstverein. A short time later a group exhibition followed (“Self Construction” 24. Nov. 1995–25. Feb. 1996) with a presentation of the work in the 20er Haus in Vienna. The work was then acquired by the Generali Collection in Salzburg.

Fig. 170a Peter Weibel: Trinity, video poem, 1975

Fig. 170b Peter Weibel: Selfportait as a Woman, 1967

Fig. 171a Peter Weibel: Endless Sandwich (1969), Art Lab, London, 1970

Fig. 171b Peter Weibel: Endless Sandwich, ORF-Sendung, 1972

Fig. 171c Peter Weibel: Endless Sandwich, ORF-Sendung, 1972

Fig. 173a Peter Weibel: Observer of the Observation: Uncertainty, 1973

Fig. 172 Peter Weibel: The Nature of Explanation, 1973

Fig. 173b Peter Weibel: Observer of the Observation: Uncertainty, 1973

Fig. 173c Peter Weibel: Observer of the Observation: Uncertainty, 1973

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* Later Weibel was not satisfied with his chosen title. According to him, it would have been more descriptive had he called the work Virtueller Tetraeder (Virtual Tetrahedron) or Virtueller Würfe l (Virtual Cube). (conversation with the author, 1995). Additionally, the term Kalter Kubus (Cold Cube) was a reference to rationality in art as an antithesis to Expressionism as well as a formal reference to Josef Hoffmann’s white lattice objects of the Wiener Werkstätten. The neurologist Antonio Damasio represents the viewpoint that rational thoughts originating from visual impressions or from hearing can be described as cold media. (Antonio Damasio in an interview with Gert Scobel in Scobel extra, 3SAT, premiere Nov. 22, 2011)

Construction of Imaginary Spaces and Observations in Apparent Spaces With the video installation Inverse Space (1977, 1980) Weibel demonstrated the paradox of the media. A gallery space appears on a box-like monitor. When someone enters the actual room, one would assume that a surveillance camera would immediately record every visitor and be shown on a small monitor, as we are accustomed to from surveillance systems. But what actually happens is nothing; the small room remains empty. Adjacent to the monitor is another box in which there is a small illuminated 2D photograph of the empty gallery space that is recorded with a camera and again appears on the screen (fig. 174 a-b). His engagement with mirror texts after 1972 and especially his experience with closed circuit video installations or the previously mentioned Inverse Space led Weibel to consider how a 2D drawing might be converted to a 3D depiction in an imaginary or virtual space. His multi-piece closed circuit video spatial installation Traum vom gleichen Bewusstsein aller (Dream of Everyone having the Same Consciousness, 1979) as well as Imaginäre Tetraeder (Imaginary Tetrahedron, 1980) are, in my opinion, to be considered to be the artist’s seminal works within the series of depictions of perspective- or observation-dependent positions (fig. 175 a-e, 176, 177). The latter was conceived and completed by Weibel during a reconstruction of an exhibition. He called the later variation Imaginärer Würfel (Imaginary Cube) or also Kalter Kubus (Cold Cube, 1990). Weibel himself also described this work as Raumzeichung (Drawing of Space).* Just as Alfons Schilling had attempted to broadcast three dimensional vision onto 2D paintings with free-vision or with autostereograms as of 1974, Weibel also tried out this pictorial experiment with the help of new technological visual media in his video-spatial installations. The lecture Ernst Mach gave in 1866 “Wozu hat der Mensch zwei Augen?” inspired Weibel above all in his arrangements of technical equipment. In this series of spatial installations Weibel always used two video cameras that recorded the two-dimensional fragmentary linear drawings on the ground and complementary to these, a small line-drawing on the wall. The two recorded images are displayed using a mixer and appear on the monitor as three-dimensional spatial images or as virtual tetrahedron or in a later variation as a virtual cube. The video cameras could be conceived of as the two eyes, the mixer and the monitor as the functions of

the brain or our consciousness. Weibel’s image-creating constructions with a video system show an apparative simulation model for binary vision. It is particularly relevant for our spatial depth perception. on the topic of imaginary tetrahedron Weibel wrote “the result was a transformation of the real space within an imaginary one. The screen creates the space in a way in which it doesn’t exist in reality. Retroactively, and by including the viewer, it also transforms the actual space.”436 In the course of dealing with theories of endophysics and with the natural scientist Roger Bosćovič (the first reputed to have recognized the interface problem of the world), Weibel arrived at an expanded and preliminarily final interpretation of his perspective perceptual work: the creation of model worlds, which explain the simultaneity of the distorted internal and external viewer dependency.437 Weibel expressed the perceptual problem of perspective distortion in various artistic media as in the concept drawing Niemals werden wir ein Rechteck rechteckig sehen (We will never see a Square as a Square, 1972), or in the series of experimental photographs Polymorphe Brechnungen (Polymorphic Diffraction, 1975) (fig. 178, 179). The video installation Gerade und geschwungene Linie (Straight and curved lines, 1981) also addressed the issue of creating visual co-distortion and the various options of levels of reality. A further recognizable affinity for nineteenth century geometric picture puzzles obtrudes here, such as the widely known Zöllner illusion (1860) and the problem of parallelism/non-parallelism. Seen in this light, the Zöllner illusion was an early scientific example in which the collision of two realities was visualized in a pictorial arrangement. Weibel referred to the Zöllner illusion again and again in his writings on perceptual theory. And still Mach’s questions concerning the straight line, which resulted from his preoccupation with Fechner’s laws, offered a possible link. A stationary video camera recorded a white beam lying askew. The monitor directly next to it showed the viewer with what was the apparently “same” beam, but here it was straight – the expected incline disappeared in the image on the virtual monitor (fig. 180). loosely based on Benussi’s theory of 1907/11 one arrives at an inadequate mental image: even though the beam is not bent, it appears to be convex. The Mach example with the pencil in a glass of water, which appeared to be bent even though everyone knew it was straight, addresses the problem of sensory perceptual illusion. In Weibel’s case it is not the sensory receptors that underlie the illusion but rather media. The virtual image becomes variable. Supported by a video system, Weibel separated the two

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* Europa(t)raum – The manner in which it is written can also imply two meanings: in one hand the dream of Europe and in other hand the European area or the map of Europe.

** More details on the aforementioned works that were made from 1982–1996 can be found in the catalog raisonné. (Schuler, ed., Peter Weibel – Bildwelten 1982–1996 (Vienna 1996).

*** In Weibel’s series Scanned Objects (1991) the calculability of the virtual image is presented. Every day objects are cut up horizontally in scanlines and reconstructed as divided objects intermittent with plexiglass placed in between.

images from reality, which nonetheless remained visible for the viewer. This meant that, what was offered was a reality in a concrete, natural space with an askew beam and a second virtual image in which it was straight. Weibel demonstrated the variability of the virtual image as opposed to the image of the material object in the space. Proceeding from these experiments with video systems, Weibel developed continuing complex spatial experiments somewhere between virtuality and reality. This principle of developing an ambiguous reality – in real space with the virtual space on the monitor – can be found, among other places, in the works Imaginärer Raum (Imaginary Space, 1982), (fig. 181 a-b) Europa(t)raum (1983)* (fig. 182 a-c), Video Labyrinth (1984), (fig. 183 a-b) or Zur Dynamik des Virtuellen (On the Dynamics of the Virtual, 1989)** (fig. 184 a-b). The actual arrangements of color, strips of tape, wooden latticework or objects (in the case of Europa(t)raum) oversized knife blades are the objects that are spread throughout the room) at first do not provide the viewer with any kind of coherent logic. Not until the virtual image do they make any sense as pictorial objects such as perspectival cubes, circles, triangles, labyrinths, maps or do they meld together as concepts. The video camera takes over construction, and the viewer himself becomes a part of this arrangement. “Der Betrachter wird zum Opfer der Perspektive”438, (“The viewer becomes the victim of perpective”) Weibel commented regarding this specific condition. Two entirely different conditions were presented to the eye. Even if our consciousness suggests that the virtual picture is a purely formal construction, we still don’t see the written program or the formula before us but perceive, on the monitor, applying our psychic/ physical capabilities, the mathematically produced virtual physicality of a cube. However, if we look into the actual room, we convey signals from the retina and the brain that are nothing but a jumble of lines.*** Weibel’s experiments on perception and the works that resulted from then would also be appropriate through cartography, characterized by a scanning of the actual process of seeing. “The retina knows nothing about perspective, nothing about the constructions of illumination, which pertain to conscious thinking; hence it does not draw any conclusions from them”439 wrote Mach in his third treatise on his experiments with light stimuli, when he had just discovered the phenomenon of the Mach-bands. In order to approach the topic of the various dimensions of reality more closely, Weibel tested spatial installations using a slide projector. For Drei

Grade der Modalität (Three Degrees of Modality, 1982) nine square glass panels were erected on the floor in the corner of a room at acute angles. Black tape was applied to the floor and on the glass panels. From a certain position, the viewer noticed a slightly distorted square. This position was photographed and projected as a slide above the installation (fig. 185). The technical slide presented a constructed segment of image information. The installation Gegenstand/Widerstand-Symphonie: Vier graduelle Verschiebungen (object/opposition-Symphony: Four Gradual Displacements, 1982) also showed the complementary cross-fadings of an image of the installation, the cutting up of visual fractions of possible realities. At the same time, the relevance of the viewer’s actual physical position becomes apparent. Dependency on this was emphasized (fig. 186). The differing planes of reality that should had been clarified as of 1990 as exoand endo-interface to reality already existed in all of the above listed works. In Weibel’s works, which immediately followed, such as Imaginärer Raum (Imaginary Space) or Video Labyrinth, the video camera and the monitor replaced both the photos and the slide projections. In the mid 1980s, Weibel heard about two new theories that clearly confirmed his artistic and theoretical considerations of the observer’s physical viewing position. First, by the so-called endophysics of the biochemist and mathematician otto Rössler440 that initially spread as the invention of dynamic systems of the Rössler-Attractor in quantum physics after 1976. With the publication of niklas luhmann’s System Theory (1984)441 the viewer was established as the primary and secondary order in the social sciences. This was to describe the differentiation of his own system. luhmann’s theory of a social system put observation into relation with the term autopoietic systems (Maturana/Varla) which were based on biology. The models of endophysics to the interface between viewer and environment greatly accommodated Weibel’s previous mode of thinking as they were seen as clear advancements in the further development of Mach’s famous sketch on the visualization of self perception and ego dating back to 1885. Towards the end of the twentieth century, new solutions to problems of observer and observing were continually considered, from the theory of relativity via quantum theory to the chaos theory. The inventor Rössler described the theory of endo-physics, which assumes an observation from within, with the model of Bubble-Boy who lived in a sterile bubble, which is his interface to the outer world.442

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Fig. 174a Peter Weibel: Inverse Space, 1977/80

Fig. 174b Peter Weibel: Inverse Space, 1977/80

Fig. 175a Peter Weibel: Dream of Everyone having the Same Consciousness, 1979

Fig. 175b Peter Weibel: Dream of Everyone having the Same Consciousness, 1979

Fig. 175c Peter Weibel: Dream of Everyone having the Same Consciousness, 1979

Fig. 175d Peter Weibel: Dream of Everyone having the Same Consciousness, 1979

Fig. 175e Peter Weibel: Dream of Everyone having the Same Consciousness, 1979

Fig. 176 Peter Weibel: Imaginary Tetrahedron, 1980

Fig. 177 Peter Weibel: Imaginary Cube (Cold Cube), 1980/90

Fig. 178 Peter Weibel: We will never see a Square as a Square, 1972

Fig. 179 Peter Weibel: Polymorph Diffraction (photoseries), 1975

Fig. 180 Peter Weibel: Straight and Curved Lines, 1981

Fig. 181a Peter Weibel: Imaginary Space, 1982

Fig. 181b Peter Weibel: Imaginary Space, 1982

Fig. 182a Peter Weibel: Europa(t)raum, 1983

Fig. 182b Peter Weibel: Europa(t)raum, 1983

Fig. 182c Peter Weibel: Europa(t)raum, 1983

Fig. 183a Peter Weibel: Video Labyrinth, 1984

Fig. 183b Peter Weibel: Video Labyrinth, 1984

Fig. 184a Peter Weibel: On the Dynamics of the Virtual, 1989

Fig. 184b Peter Weibel: On the Dynamics of the Virtual, 1989

Fig. 185 Peter Weibel: Three Degrees of Modality, 1982

Fig. 186 Peter Weibel: Object/Resistance-Symphony: Four Gradual Displacements, 1982

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Interactive Images and Dislocation

A new era began in the 1990s with interactive, computer-based image editing. Weibel is a highly productive artist who continuously presses on with his new concepts in art helped by the latest developments, and who, while in the process of this, must also correct himself. With the advent of interactive media, Weibel had adequate means at his disposal to further refine the representations of his artistic reflections regarding his theme of the role of the viewer. In addition, new media made it possible for him to experiment with the simultaneity of phenomena, respectively the socalled dislocation or the non-locality. Early test-runs and approaches proved to be effective when he dealt with new digital image media which once again prompted him to define a new image that was governed by the three Vs: virtuality, variability and viability. The virtuality of the image – or also: the algorithmic image – was distinguished by the computer’s capacity to store information. The content of the image was to be context-dependent, thus the image would achieve the characteristic of variability. Finally, these new images were to be dependent on the system itself, highly dynamic and true-tolife, thus they would be characterized as viable. With this triple-equation, art had – for Weibel – long since transitioned to a post-ontological status.443 Das Tangible Bild (Tangible Image, 1991) was one of the early interactive works in which the theme of dislocation was presented to the observer in real time. The viewer stood in front of a monitor with a screen made of black rubber that he could touch with the help of built-in sensors. Behind the viewer was a cartesian grid. Grid and viewer were recorded with a video camera and projected live onto a projection screen. The viewer, now registered as a bulk of data himself, could also change the image by touching the screen and with it, the projected image – a de facto interaction with themselves. A so-called co-distortion emerged (fig. 187 a-b). A similar topic was addressed in Cartesianisches Chaos (1991). In this it was not the screen that was the interface but rather the floor with built-in sensors. In the true sense of the word, the viewer stepped into the image space and integrated with the computer-generated image of the surface of water that appeared to be flowing over an opened (digital) cube (fig. 188). In a further development of the preceding project Cartesiansiches

Chaos (cartesian chaos), in Weltwürfel (World cube, 1992), sensors underneath a chessboard pattern on the floor triggered a perspective co-distortion, which was activated by the viewer stepping onto it. The activity was then projected on the wall. In these interactive computer-works the model of the inner observer was most clearly exemplified (fig. 189). Peter Weibel realized the idea of a pluriversum or a multiversum in 1992/1993 in his interactive computer installation Zur Rechtfertigung der hypothetischen Natur der Kunst und der Nicht-Identität in der Objektwelt (on Justifying the hypothetical nature of Art and the non-Identity in the object World). Initially it was presented as a three part work (architecture, letters and object world) but was supplemented by a further virtual world, the gas-world 444/*(fig. 190 a-c). The letter world reflected Weibel’s conviction that our alphabet was the first, if not actually the oldest interface.445 Stepping into the respective world occurred through sensors on the floor that can be associated with a typewriter keyboard. In order to allow reversible communication between the virtual parallel worlds, according to Weibel, a quantum computer would be required. The gas-world most closely represented the idea of life-like behavior. The creatures that were created virtually looked for food and fled from others. clouds of gas represented hypothetical beings for the kinetic gas theory. Because of their characteristics, the gas molecules could not initially be explained in detail when they collided. James Maxwell found the solution in a thought experiment that would later be known as Maxwell-Dämon (Maxwell demon) **/446: Through self organization, following the intelligence of swarming, the system was able to develop variability. In 1994447 Weibel recognized that this was a simplified model of Darwin’s Theory of Evolution – for Darwin the biological organs that developed the fastest had the greatest variability.448

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* The term gas comes from the Belgian physician and natural scientist Johan Baptista van Helmont who explicitly mentions the reference to chaos.

** The result of James Maxwell’s thought experiment, in order to disprove the second theorem of thermodynamics, was later denoted by Lord Kelvin as MaxwellDemon.

Fig. 187a Peter Weibel: Tangible Image, 1991

Fig. 187b Alexander Ströck: reconstruction sketch for the publication “Bildwelten”, 1996

Fig. 188 Peter Weibel: Cartesian Chaos, 1991

Fig. 189 Peter Weibel: World Cube, 1992

Fig. 190a Peter Weibel: On Justifying the Hypothetical Nature of Art and the Non-Identity in the Object World, 1992/93

Fig. 190b Peter Weibel: On Justifying the Hypothetical Nature of Art and the Non-Identity in the Object World, 1992/93

Fig. 190c Peter Weibel: On Justifying the Hypothetical Nature of Art and the Non-Identity in the Object World, 1992/93

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* Refers to the boundaries of Aristotle’s science of nature.

Interactive Plasticity in the Virtual Image

In 1993, Weibel developed an advanced form of interactivity with a virtual image. In Der Vorhang von Lascaux (The curtain of lascaux), a photograph of the stone-age cave paintings of lascaux were projected on a wall. The viewer, who was recorded by video camera, was able to walk through three-dimensionally through the cave drawing into the foreground (fig. 191). In order to bring the oldest known stone age wall paintings contextually into the world of computer art, a chronology of the image needed to be compiled – from their origins up to our day – from the classical, ontological image to the postontological, virtual, interactive pixel image. The evolution of the image, from a fixed cave drawing on stone through the transportable panel painting on the screen and finally to the flexible, variable digital image on the computer screen or the projection wall, the three-dimensional virtual figures on the screen became significantly clearer. The downright doughy, occasionally liquid-like plasticity of the image became even more evident in the second variation of Lascaux: The Wall, the Curtain, (Boundaries*) technically speaking also: Lascaux (1994). here the viewer was standing in front of a wall onto which a brick wall had been projected and into which he was imprinted like a footprint in the sand (fig. 192). If the work Lascaux I shows the status quo of the new virtual and interactive image, then the virtual brick wall here was seen as a boundary against which the viewer bumped again and again. This was assumed to be the hypothetical boundary – as a closed curtain – that separated us from the exo-world, which lay closest. After all, these are the ancient imagined wishes or frankly stated basic human curiosity that drove us to the desire to overcome the visible “inner world”, to change or even to conquer the endo-position of the here and now. In addition to artistic editing of physiological-psychological perception, these last two works exhibited narrative elements for the first time. As early as May 1993, Weibel introduced this technique of dimensional portrayal in his virtual image with his work Jede(r) ist jede(r). Jede(r) ist der/die andere für jede(n) in der Heimat Babylon (Everyone is everyone, everyone is the other for everyone in the home of Babylon, 1993) (fig. 193). In this work, consisting of several parts and displayed over two stories of a building, he also projected a digital image of the painting Turmbau von Babel (Tower of Babel) by Pieter Bruegel. Using an automatic security

video camera mounted on the roof of the exhibit building*, he videorecorded the skyline of Frankfurt as a three-dimensional live-picture was superimposed over the digitized Turmbau von Babel (Tower of Babel) (fig. 194 a-c). comparable to Schilling’s search for new, never-before-seen images, Weibel attempted to actualize – using the medium of the moving image, with film, with movies, – novel ways of image-perceptions during the second half of the 1960s. consequently, he demanded liberation from neural integration 449, that is, from the neural networks of the state 450 as related to a multitude of projects that disputed sensual perceptions. As Weibel wrote regarding his Pillen (Pills) project: I think of films in the form of a new sensory organ that affords me every desired sensory quality, delivers air to me, whether coming from lung breathing, jaw breathing or the reverse, that does not shy away from discrepancies of sensory data, permits me to grasp foam when I see stones, allows me to smell chocolate when I eat grasses, lets me hear violins when I glue envelopes shut, that allows me to feel water when I reach for the electrical outlet, etc.451 Weibel considers the act of seeing as an active deed that is not solely restricted to the eyes.** Roughly thirty years later, he took up his early radical-visionary ideas of interface once again, which might have enabled visual perception without the use of the eyes. According to this, the intelligent interfaces of modern image technology should find direct access to the human body in order to create a total independence of space and time and to disable the manipulable interfaces between the image (the information) and the observer. Eyes, mouth, ears and arms – the biological peripheral devices should be replaced by tools, by a pencil, a palette of paints, but also by a computer and its programs. hence it is not surprising that Weibel, in addition to his social, political and ecological studies on perception, should once again turn his attention more onto the research of sensual perception as it had been in the nineteenth century. That is, he directed his interest in cognition once again toward modern neurosciences. In a symposium in Budapest in January, 1996 at which Weibel gave a public lecture with the title Intelligent Image452, he used the term neurocinema for the first time, a concept that has since become popular. In addition to this suggestion, he brought up the topic of the meaning of Quantum Physics and the coming quantum-

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* The solo show took place at the Karmeliter Kloster, Ausstellungshalle Frankfurt/Main, Germany, May 7 to June 13, 1993.

** Weibel often used the term Handlungsakt (action) synonymously with Sehakt (seeing). In conversation with the author during the exhibition Vision which Weibel curated in Weimar in August 2011.

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* Babylon is tentatively Weibel’s last work with a perceptual theoretical aspect on the topic of observation. In the years that followed political, economic and social critical implications dominated his artistic work. It was only in the spring of 2011 that a new work Das Leben im 20. Jahrhundert: 225 Millionen Morde (The Life in the twentieth century: 225 Million Murders) was tied to the interface debate of the 1990s with its technical use of displays of tablet computers.

computers as an interface for understanding between parallel worlds. As early as June 1996, within the framework of a group exhibit Wunschmaschine – Welterfindung (Wish Machine – Invention of the World) in Vienna, he introduced Babylon* his next-to-the-last interactive videocomputer work,453 which dealt exclusively with perception and viewer independence. This work gained little attention, even though Weibel had artistic edited his novel concept of neurocinema or quantum cinema.454 In principle, this also dealt with a coherent visualization of the points of view of various observers. He began with Bruegel’s painting Tower of Babel, which he had already cited in 1993. This time Weibel was able to integrate the original, which is located in the Kunsthistorisches Museum Wien (Viennese Museum of Art History) into his work. The painting shows King Nimrod gazing upon the construction of the Babylonian tower. The visitors of the Kunsthistorisches Museum stood in front the painting and thereby formed the outer observers who in actuality were looking at a classic “frozen” image narrative. The room in which the painting hangs was recorded with a video camera and the image data was transferred to a computer about 500 meters away, to the Kunsthalle on the Viennese Karlsplatz, where the actual exhibition was taking place. Here the visitors saw a digitized, moving image. In addition to where the viewer stood, communication occurred on three levels among the visitors on the interior of the Kunsthistorisches Museum and the visitor of the Kunsthalle and finally, the visitor to the Kunsthalle was also able to communicate with the visitors of the original. As a result, the direct viewer of the original was not privileged but instead, the visitors of the Kunsthalle had a much broader spectrum and means of communication and perception at their disposal. Weibel wrote in his catalog essay: “The machinesupported perception is the end of the illusion, the end of the reign of the monopoly of the real. The ruler looks upon the world, the citizen looks into the future on the display in his brain.”455 The consideration of simulating vision, aided by modern image technology and consequently by replacing it entirely with interfaces, is something Weibel recognized as the only opportunity for self-perception and observation of the environment that was to expand the boundaries of our inner universe. Weibel’s most recent work Life in the twentieth century: 225 Million Murders (2011)456 is merely on the screen of a tablet computer supported by so-called augmented reality, a computer-based expansion of reality perception (fig. 195 a-c).

neuro- or quantum-cinema represented the beginning of the next, continuing level of interface theories. It is conceivable that Weibel could have been right with his prognosis based on today’s development in the omnipresence of electronic screens in both public and private use such as information screens, navigational devices and even including e-books or screens on mobile phones.

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Fig. 191 Peter Weibel: The Curtain of Lascaux, 1993

Fig. 192 Peter Weibel: The Wall, the Curtain (Boundaries) technically speaking also: Lascaux, 1994

Fig. 193 Peter Weibel: Jede(r) ist jede(r). Jede(r) ist der/die andere für jede(n) in der Heimat Babylon, 1993

Fig. 194a Peter Weibel: Tower of Babel, 1996

Fig. 194b Peter Weibel: Tower of Babel, 1996

Fig. 194c Peter Weibel: Tower of Babel, 1996

Fig. 195a Peter Weibel: Life in the 20th Century: 225 Million Murders, 2011

Fig. 195b Peter Weibel: Life in the 20th Century: 225 Million Murders, 2011

Fig. 195c Peter Weibel: Life in the 20th Century: 225 Million Murders, 2011

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Feedback-Effects

This study intends to shed light on two essential issues: first, the path of scientific observation from the physiological visual illusion to the discovery of the afterimage and the creation of apparent motion/apparent spaces in in the experimental-psychological-physiological sciences. on the other hand, it intends as well to reflect back on the transformation of scientific-virtual image generation in the arts to the empirical-experimental and perceptual research of the nineteenth century. The development of an empirical methodology for experiments explaining human seeing of virtual phenomena such as apparent motion and apparent spatiality took place primarily in the very early epistemic disciplines such as experimental physiology, psychology and physics of the nineteenth century. In the course of the twentieth century, the continuation of research and the resulting acquisition of knowledge particularly in computer science and currently in neurosciences ensued. The creation and analysis of visual illusionary patterns with the aim of optically stimulating the human eye were popular areas of experimental research on perception as documented by the Zöllner- or Müller-lyer’s illusions. The questioning of apparent realities, that can occur in the perception of the outer world just as can emerge in inner images or – according to the experimental replicable visual perception of apparent realities – has been scientifically pursued with a clear positivistic attitude ever since the beginning of the nineteenth century. The discovery of mechanically created moving images using stroboscopic disks or the recognition of spatial images supported by stereoscopes, such as the invention of photography, unleashed euphoria in the historical area of physiological research dealing with visual perception. The research and scientific explanation of apparent images that had been discovered when afterimages emerged brought an abundance of spectacular and even extremely speculative studies on the human retina. The primary instruments were rotating, especially painted disks such as the stereoscope in order to allow apparent objects to appear on a screen that provoked the phenomenon of apparent motion. The relevance of the duration of time of light stimulaton of the retina was quickly recognized – with the argument of why medial digital art is characterized as time-based art.

As a consequence of the results and insights on apparent motion at the turn of the twentieth century, a gestalt theoretical reversal took place in experimental psychology. Vittorio Benussi introduced the idea of ambiguity in conjunction with the term of inadequate beliefs in perception psychology. Max Wertheimer established the new Berlin Gestalt School with his experiments on apparent motion. In Vienna, the psychologist Karl Bühler457 enjoyed talking about duplicity in the phenomenon of apparent space*. his student, Egon Brunswik, separated perceived and subjective worlds.458 Fritz heider**extrapolated the thing and the medium from the Bühler Duplicity Principles.459 and so presented the outline for a term that is very much up-to-date in current media theory. The apparative experiments made the fragility of our visual perception evident or led to the realization that perception must de facto be a construct. The three artistic positions which have been presented and which focused on apparent motion and apparent worlds demonstrate on the one hand coherency in their work, on the other hand, their distinct discrepancies. The observation of Shaw, Schilling and Weibel’s works clearly illustrate the contemporaneous approach to technological image media, devices etc. but ultimately and especially show their very differentiated reflection and transformation of the epistemic path taken and the historical experiments on sensory perception of the nineteenth and twentieth centuries. The approach sketched here examines various areas holistically and seeks also to reveal the still existing structural problems (such as separate institutions) of an interdisciplinary connection between science and art. In scientific research, a theory generally precedes an experiment even when, in the end, an unexpected result might be achieved. That is precisely where the media artist and theoretician Weibel finds a definition for contemporary art: to artistically scrutinize existing theories with experiments, to verify questioning empirically through art. Two crucial directions became apparent in the course of drafting a developmental history of virtual art that referred back to the historical scientific recurring experiments on perception: A phenomenological direction, evidently also developed out of new behaviorism, the participatory effect in actionism and from multi media performances. Thus it introduces multi-narrative as a new narrative form and not linear as in the world of the digital image. current content

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* The Bühler Theory of duplicity (light-airhypothesis) developed in connection with color perception.

** Heider took his doctoral degree in 1920 under Alexius Meinong in Graz. He worked with Wertheimer in Berlin in 1921. In 1927 he was Wilhelm Stern’s (1927) assistant in Hamburg. In 1930 he emigrated to the United States.

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and imagery are transferred and communicate with modern digital image media interactively. An epistemic-artistic alignment, which in turn even evokes an exit from art but does not cause the predicted end of art. There is actually an attempt made to supercede a fixed (empirical) canon. According to the above, one could simply assume a dynamic dualism that is split up into a phenomenalistic image-oriented or reality cognition-oriented direction of art. To an extent this dynamic dualism can be interpreted as an expression of our overall media-oriented culture. Homo ludens is a catchphrase that has assumed an important role especially in the field of cybernetics. Jeffrey Shaw, who is named here as a representative of the first category, concentrated on the playful interaction with virtual landscapes. Today, game arts are ever present in the area of artistic digital interaction and also in regard to social networks on the web, such as Facebook or Google+. Shaw’s creative playfulness in inventing interfaces, the interactive use of stereoscopic environments as well as the integration of the public as an essential part (taking on a necessary active role) are not only descriptive but significant criteria in terms of content in his work; think of Points of View (1983) in which the use of joysticks as symbols are driven onto the field. Interactive networking becomes a component of the creative process and that is why Shaw understands the network of media artists as an absolute requirement for his work. The implementation of complex media installations demands a large team of experts who can computationally resolve the project in a creative and technologically current way in the form of an “intelligent image”. Artistic interaction with “intelligent” machines and their implementation have long occupied our own highly virtual living spaces. Shaw’s works stand for téchne or in latin ars in the classic sense. he uses the machine in order to create a fantasy trip, a virtual landscape, and in order to create a highly advanced narrative artistic experience using modern digital means. Schilling and Weibel, on the other hand, follow a common tradition in their artistic practice, namely an emphatic scientific orientation. Both apply an experimental empirical method in their artistic work and thus refer again and again specifically to the known positivist Ernst Mach. Accordingly, Weibel’s and Schilling’s artistic work is associated with the episteme, the science and theory of cognition. They concentrate on the

process of the origination of perception itself, on the questions of how one arrives at the contemplation of images, which role the viewer assumes and what they can recognize, through the senses, either consciously or by way of introspection. Schilling and Weibel avoid the phenomenalistic recycling of images in their work. Schilling even creates a temporary break in his artistic production because he was afraid of being repetitive. Schilling considers the Renaissance artist leonardo da Vinci to be representative of the universal prototype.* What is distinctive is that leonardo was specifically focused on human anatomy, the physical apparatus, as well as the muscles, bones and organs of the human body. Vision also was central to his concerns. he was additionally interested in the construction of devices and machines that might be able to serve mankind in expanding their sensory perception. That he was supposed to have been an important mentor in technology and computer sciences does not correspond to the historic facts, as Elisabeth von Samsonow correctly indicated in her studies on modern philosophy.460 Those responsible for the digital code were other scientists such as Raimundus lullus (a great thinker of the Middle Ages) with his logical machine, or Kurt Gödel in the twentieth century, whom Weibel held in such great esteem. Moreover, Schilling adhered to his role model: he built machines, devices as interfaces that expanded vision without the help of a digital code. Even though he worked parallel to his friend Béla Julesz, who programmed stereoscopic images in the Bell labs, Schilling achieved his own singular artistic mode of expression with “conventional” analog seeing devices and stereo images that were without a doubt endemic to his experiments. In his early works Peter Weibel had already grappled with physiological psychological sensory perception. like Alfons Schilling, he conceptualized devices – machines to supplement and expand on human sensory perception. At almost the same time, he also looked for connections with logical algorithmic approaches that he attempted to express in his experimental poetry. Weibel’s orientation toward logic emerged increasingly with his study of mathematics as of 1967, which led him to (as opposed to Schilling) work with the development of the scientific background of digital image generation. A key to Weibel’s complete works is the implication of two fundamental methodological approaches: simulation and implants for the sensory apparatus plus the application of the digital code. on the one hand he draws on the metaphor of the machine and the basic idea of

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* In a conversation with Schilling he read a quotation of Leonardo da Vinci’s to me and added that this sentiment of Leonardo’s was exactly what he felt about art and science. (Conversation with Alfons Schilling, May 2006).

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* Precisely this complex interweaving of two essentially different concepts also produced a certain unimaginable and difficult attribution of Peter Weibel’s œuvre that is based not only on his artistic work or curatorial activities but also on his teaching and his theoretical work. Meta-terms such problem constancy can ease the profound conflict with Weibel’s artistic-epistemic universe.

the prostheses for the expansion of the senses, as Schilling had with leonardo’s revitalized world view. on the other hand, he expertly celebrates and generates concepts with codes for his language- and image- poetry which cling to the rich tradition of the world of digits, beginning with Raimundus lullus and up to Kurt Gödel or Allen Turing.* These works of Weibel often appear to be awkward and inaccessible because their prevailing empirical aspect exclude their aesthetic impact.461 For art of the new digital-image world, the return to early research in sensory perception of the nineteenth century is of great relevance and with it the even more current direction – virtual or digital art. Their issues can be positioned convincingly in cultural sciences, expand and vary them anew. After all, according to Mach the experimental-empirical methodology and its variations were a basic requirement for the scientist and had its beginnings with thought experiment. In accordance with James W. McAllister, all scientific [also artistic (author)] revolutions have their origins when a known aesthetic quality is abandoned in order to make new discoveries. Then the search for theories begins anew. The methodological approach of the empirical sciences seems to have been completely adopted by experimental art. curiosity is the leitmotif for all research. It is in the primary position of every epistemic act: it implies and legitimizes every form of artistic research. Additionally, the scientific historian and biologist hans-Jörg Rheinberger has paradoxically but aptly formulated the well-known aphorism: “Research means not understanding”.462

EPIloG

For art, art theory, as well as scientific theory, Romana Schuler’s book is highly significant for several reasons. To begin with, Schuler’s method of presenting the development of art movements is not simply art-intrinsic but based instead on technological and scientific history. For good reason she begins her thesis with a discussion of artists who had conducted research themselves – at least in the field of popular science. For this reason they were familiar with scientific methods and their results in their experiments with the perception of movement. This book provides an equally surprising and overwhelming abundance of evidence to support this theory. In this regard, there is one notable discovery that is unique: revealed here, for the first time, is the connection between the first readymade work Roue de bicyclette (Bicycle Wheel, 1913) by Marcel Duchamp with the scientific counterpart by Max Wertheimer (Schumann/Wertheimer Wheel tachistoscope, 1898–1910). Wheel technology could be found in almost all laboratories at the time. Duchamp, who was known for going to invention fairs, had apparently brought the wheel from the lab into the studio. originally not considered as an artwork but rather as an object to be perused and used for demonstrations. Duchamp, clearly fascinated with observing movement, built himself one and placed it in his studio. There is not only a wealth of convincing material supporting this theory that avant-garde artists at the turn of the twentieth century were familiar with popular scientific literature but also that the precision with which this material was processed is conclusive. here Schuler presents a panorama of nineteenth century experimental psychology that addresses the phenomena of perception and movement. Subsequently, the technological-industrial revolution would succeed in experimentally analyzing and recreating physiological movement processes and perception processes. This experimental psychology is the prerequisite for the –isms of twentieth century art. From Plateau to Mach, the innovations, theories and experiments within the realm of experimental psychology have been diversely and extensively processed. The artists of cubism, futurism and constructivism, op art and kinetic art used precisely these. The development of the laws of

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optical illusions and apparent motion are primarily presented as the logical consequence, of laboratory experiments in visualizing apparent motion, apparent corporeality and apparent spaces. Following an extensive account of the research results, that also includes the works of lesserknown authors such as Adolf Szily or natalie Förster. Romana Schuler describes the Innsbruck School (Erismann and Kohler) invention of experimental seeing devices in the 1950s. These seeing devices influenced the development of machine- and media-aesthetic up to cyberspace. Artists such as carsten höller settled for mimicking these inventions and presenting them to an uninformed public. These results lead to the second thesis of the book, which is that large parts of twentieth century art are based on scientific research conducted during the nineteenth century. The avant-garde of the first half of the twentieth century based their art directly on such research findings. An example is Ernst Mach’s photography of wind resistance on projectiles depicting an open triangle. Futuristic painters applied this angle bracket for the depiction of movement and the dispersal of light. By way of painting, this open triangle became the universal symbol for drive and movement – consider the button on recording devices where this triangular symbol depicts forward and two such triangles together symbolize fast forward. With the neo-avant-garde media art that followed the Second World War, interdisciplinary development took on a new dimension. For the first time artists were able to transfer the results of new technology to new art forms and as such contributed to the study of seeing movement. The third thesis amounts to demonstrating that, towards the end of the twentieth century, the development of digital technologies was used in order to broaden the research horizon of science and art. Romana Schuler demonstrates this with three media artists’ departure from the repertoire of apparent perception and apparent motion to the virtual realm. Virtuality became the key concept of interactive media art of the 1990s and also the central term of media philosophy, especially among the French representatives from Baudrillard to Virilio. These three media artists succeeded in producing findings that go beyond the scientific findings even though the historical discoveries were adapted from science. The outstanding merit of this book is that for the first time a precise analysis is made of the psycho-physiological experimental system of

the nineteenth century on the topic of illusion that became the basis of art and philosophy of virtuality 100 years later. This publication spans an art historic and scientific arc from helmholtz’s experiments to op Art and kinetic art to computer supported virtual environments. Romana Schuler tells the story as it has never been perceived, and reading it is rewarding. The fourth and final thesis of this book is: The perception apparatus and seeing machines of the artists at the end of the twentieth century are nothing more than the continuation of the work conducted by nineteenth century scientists. What therefore becomes evident is that the relevant contemporary art demands an art theory which integrates scientific and technological history. At the same time, these artistic results indicate that the neo-avant-garde of media art should be integrated into scientific history and technology history because their findings sometimes trump those in scientific research or can stimulate new ideas. In addition to the rich historical source material and the stringency of argumentation in this respect, this is the particularly novel aspect of this publication. This book bears meaning not only for art history but also for the history of knowledge. The fundamental principle that empirical proof follows and therefore must follow the theory has to some degree been accepted in contemporary scholarship. otherwise expressed: applied technology follows fundamental research. heinrich hertz’s empirical proof follows J. c. Maxwell’s mathematical equation on electromagnetic waves. Guglielmo Marconi’s empirical applications in turn followed these. Romana Schuler demonstrates, in an additional step, not only that applied sciences can follow empirical sciences but that indeed they should, as does experimental art. With that she proves her fifth and future-oriented thesis: innovative sciences and innovative art are both germane to epistemic experimental systems. Peter Weibel, 31st of August 2015

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Jonathan crary, Techniken des Betrachters. Sehen und Moderne im 19. Jahrhundert (Dresden, Basel, 1996), 18–35. Thomas Kleinspehn, Der flüchtige Blick, Sehen und Identität in der Kultur der Neuzeit (Reinbek bei hamburg, 1991), 212–24. Michael Foucault, Die Geburt der Klinik (Munich, 1973). Andrea A. Reichenberger, “Wissenschaft und Kunst: Alois Riegl contra Emil du BoisReymond” in Alois Riegl. Revisited, Arthur Rosenauer, Peter noever, Georg Vasold, eds. (Vienna, 2010), 206. Gerhard Benetka, Denkstile der Psychologie. Das 19. Jahrhundert (Vienna, 2002), 51. hermann helmholtz, Handbuch der physiologischen Optik (leipzig, 1867), 797. helmholtz, Populär-Wissenschaftliche Vorträge, 2nd booklet, 2nd edition (Braunschweig, 1876), 3. Michael Ruoff, Hermann von Helmholtz (Paderborn, 2008), 90. helmholtz, Handbuch der physiologischen Optik, 625–626; Ibid., “optisches über Malerei” in Populär-Wissenschaftliche Vorträge, 3rd booklet (Braunschweig, 1876). helmholtz, Handbuch der physiologischen Optik, 647–649. Ibid., 601–603. Ernst Mach, Populär-wissenschaftliche Vorlesungen (1896) (leipzig, 1910), 93–95. Sigmund Exner, “Über das Sehen von Bewegungen und die Theorie des zusammengesetzten Auges” in Sitzungsberichte der Kaiserlichen Akademie der Wissenschaften. Mathematisch-Naturwissenschaftliche Classe, vol. 72, sec. III, 1875 (Vienna, 1876), 156–191. Sigmund Exner, Zur Physiologie des Fliegens und Schwebens in den bildenden Künsten (Vienna, 1885), 15–16; Peter Geimer, “Das Gewicht der Engel, Eine Physiologie des Unmöglichen” in henning Schmidgen, Peter Geimer, Sven Dierig, eds., Kultur im Experiment (Berlin, 2004), 170–190. William Porterfield, A Treatise on the Eye, the Manner and Phenomena of Vision (Edinburgh, 1759), vol. 2; Rebekka ladewig, “Augenschwindel, nachbilder und die Experimentalisierung des Schwindels um 1800” in Werner Busch, caroline Meister, eds., Nachbilder. Das Gedächtnis des Auges in Kunst und Wissenschaft (Zurich, 2011), 107–126. Marcus herz, Versuch über den Schwindel, 1786, 2nd edition (Berlin, 1791), 180. William charles Wells, “An Essay upon Single Vision with Two Eyes Together with Experiments and observations on Several Subjects in optics” (1792) in William charles Wells, Two Essays: One Upon Single Vision with Two Eyes; the Other on Dew (london, 1818), 1–117. crary, Techniken des Betrachters, 92–102; Ralph Köhnen: Das optische Wissen. Mediologische Studien zu einer Geschichte des Sehens (Munich, 2009), 357. Peter Rieß, Über elektrische Figuren und Bilder in Annalen der Physik und Chemie, vol. 2 (leipzig, 1846), 13. Ibid., 20–30, Hauchbild = breath-image. Ibid., 8–9. Ibid., 21. Ibid., 37. Jan Purkinje, Abhandlung über die physiologische Untersuchung des Sehorgans und des Hautsystems, dissertation (Breslau, 1823), quotation taken from reprint in Acta Historica Leopoldina, nr. 11 (halle/Salle, 1979), 110. Johann Wolfgang von Goethe. “Das Sehen in subjektiver hinsicht” (1819) in Ernst

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Beutler, ed., Artemis-Gedenkausgabe der Werke, Briefe und Gespräche, vol. 16 (Zurich, 1950), 844–856. Köhnen, Das optische Wissen, 350. Purkinje, Abhandlung über die physiologische Untersuchung des Sehorgans und des Hautsystems, 123. Purkinje, “Beiträge zur Kenntnis des Schwindels aus heautognostischen Daten” in Medicinische Jahrbücher des österreichischen Staates 6 (Vienna, 1820), quoted here following Alfons Borschke, Leo Hescheles “Über Bewegungsnachbilder” in Zeitschrift für Psychologie und Physiologie der Sinnesorgane, vol. 27 (Leipzig, 1902), 388. Purkinje, Abhandlung über die physiologische Untersuchung des Sehorgans und des Hautsystems, 110. Ibid., 14–15. Ibid. Ibid., 15. Ibid., 122–123. Ibid., 122. Ibid. Johann Czermak, “Über die entoptische Wahrnehmung der Stäbchen- und Zapfenschicht” (Membrana Jacobi Retinae) in Sitzungsberichte der Kaiserlichen Akademie der Wissenschaften. Mathematisch-Naturwissenschaftliche Classe, vol. 41, sec. II (Vienna, 1860), 645. Czermak, “Zur objektiven Erklärung einiger sogenannten subjektiven Gesichtserscheinungen” in Sitzungsberichte der Kaiserlichen Akademie der Wissenschaften. Mathematisch-Naturwissenschaftliche Classe, vol. 43, sec. II (Vienna, 1861), 168. Helmholtz, Handbuch der Physiologischen Optik, 381. Czermak, Über die entoptischen Wahrnehmungen, 645. Peter Mark Roget, “Explanation of an optical Deception in the Appearance of the Spokes of a Wheel as seen through Vertical Apertures” in Annals of Philosophy, vol. 10 (London, 1825), 107–112. Roget, “Erklärung eines optischen Betruges bei Betractung der Speichen eine Rades durch vertikale Öffnungen” in Annalen der Physik und Chemie, vol. V (Leipzig, 1825), 93–104. Ibid., 94–98. J.M. in Quarterly Journal of Science, vol. 10, 282. Hermann Kalkofen, “Anorthoskop (Plateau 1836) und anorthoskopische Erscheinungen”, edited version of the lecture at the 42. Kongress der Deutschen Gesellschaft für Psychologie (Jena, 2000) http://psydok.sulb.uni-saarland.de/volltexte/2004/150/html/ Kalkofen2003Anorthoskop.html (accessed 12.11.2011). Roget, “Explanation of an optical Deception in the Appearance of the Spokes of a Wheel as seen through vertical Apertures”, 94. Ibid., 104. Joseph Plateau, “Über einige Eigenschaften der vom Lichte auf das Gesichtsorgan hervorgebrachten Eindrücke” in Annalen für Physik und Chemie, vol. 20 (Leipzig, 1830), 304–305. Ibid., 305. Ibid., 306; As a source Plateau quotes from Thomas Young, A Course of Lectures on Natural Philosophy and the Mechanical Arts, vol. 1 (London, 1807), 455. Ibid., 310. Ibid., 311. Ibid. Ibid. Ibid., 313. Charles Wheatstone, “Traumatrop oder Kaleidoskop” in Annalen der Physik und Chemie,

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vol. 10 (leipzig, 1827), 470–480. Joseph Plateau, “correspondant Mathématique et Physique”, De L’Observatoire de Bruxelles, vol. VII (Brussels, 1833). Johann c. Poggendorff, “Stroboskopische Scheiben, Phänakistiskop, Phantasmaskop” in Annalen der Physik und Chemie, vol. 32 (leipzig, 1834), 636–649. compare the description by Michaeal Faraday, “Über eine besondere Klasse von optischen Täuschungen” in Annalen der Physik und Chemie, vol. 22 (leipzig, 1831), 601–606. Ibid., Faraday, 602. Ibid. William George horner, “Über die Eigenschaften des Deadaleum’s eines neuen auf optische Täuschung beruhenden Instruments” in Annalen der Physik und Chemie, vol. 32 (leipzig, 1834), 650–655; Poggendorff, “Stroboskopische Scheiben, Phänakistiskop, Phantasmaskop” in Ibid., 648–649. Franz Uchatius, “Apparat zur Darstellung beweglicher Bilder an der Wand” in Sitzungsberichte der Kaiserlichen Akademie der Wissenschaften. MathematischNaturwissenschaftliche Classe, vol. 10 (Vienna, 1853), 482–485. Ibid., 484. David Brewster, “Über Schwingungen in der netzhaut erregt durch die Wirkung leuchtender Punkte und linien” in Annalen der Physik und Chemie, vol. 27 (leipzig, 1833), 490–497. Ibid. William h. Fox Talbot, “Experiments of light” in The London and Edinburgh Philosophical Magazine and Journal of Science, 3rd series, vol. 5, nr. 29 (london, nov. 1834), 327. Ibid. Ibid., 328. Plateau, “Betrachtungen über ein von hrn. Talbot vorgeschlagenes photometrisches Princip” in Annalen der Physik und Chemie, vol. 35 (leipzig, 1835); Plateau, “Bulletin de l’acad. Roy. des sciences et belles-lettres de Bruxelles”, vol. 2 and 3 (Brussels, 1835), 52 and 89. Talbot, “Experiments of light”, 331. Plateau, “Betrachtungen über ein von hrn. Talbot vorgeschlagenes photometrisches Princip”, 466–467; Talbot, “Experiments of light”, 332. Gustav Theodor Fechner, “Über eine Scheibe zur Erzeugung subjectiver Farben” in Annalen der Physik und Chemie, vol. 45 (leipzig, 1838), 227–232. Ibid., 227. Ibid., 229. Ibid., 230. Plateau, “Über eine neue sonderbare Anwendung des Verweilens der Eindrücke auf die netzhaut” in Annalen der Physik und Chemie, vol. 78 (leipzig, 1849), 563–567. Plateau, “Zweite notiz über neue sonderbare Anwendungen des Verweilens der Eindrücke auf die netzhaut” in Annalen der Physik und Chemie, vol. 79 (leipzig, 1850), 269–290. Ibid., 289. Plateau, “Dritte notiz über neue sonderbare Anwendungen des Verweilens der Eindrücke auf die netzhaut” in Annalen der Physik und Chemie, vol. 80 (leipzig, 1850), 150–157. Ibid., 156. Plateau, “Dritte notiz über neue sonderbare Anwendungen”, 157. Plateau, “Vierte notiz über neue sonderbare Anwendungen des Verweilens der Eindrücke auf die netzhaut” in Annalen der Physik und Chemie, vol. 80 (leipzig, 1850), 287–292. Ibid., 288–289. Karl Wilhelm Wolf-czapek, Die Kinematographie, Wesen, Entstehung und Ziele des

lebenden Bildes (Dresden, 1908), 35. 83 Johann Josef oppel, “neue Beobachtungen und Versuche über eine eigenthümliche, noch wenig bekannte Reactionsthätigkeit des menschlichen Auges” in Annalen der Physik und Chemie, vol. 175 (leipzig, 1856), 542. 84 Ibid., 541–542. 85 Ibid., 557. 86 Ibid., 559. 87 Ibid. 88 Ibid., 561. 89 oppel, “Über ein Anaglyptioskop (Vorrichtung, vertiefte Formen erhaben zu sehen)” in Annalen der Physik und Chemie, vol. 175 (leipzig, 1856), 466–469. 90 Friedrich Zöllner, “Über eine neue Art von Pseudoskopie und ihre Beziehungen zu den von Plateau und oppel beschriebenen Bewegungsphänomenen” in Annalen der Physik und Chemie, vol. 186 (leipzig, 1860), 503. 91 Ibid., 500. 92 Ibid., 501. 93 Ibid. 94 Ibid. 95 Ibid., 505. 96 Ibid., 507.; see Mach, Grundlinien der Lehre von den Bewegungsempfindungen (leipzig, 1875). 97 Ibid., 504. 98 Ibid., 509. 99 Ibid., 511. 100 Ibid., 512–513. 101 Ibid., 514. 102 Ibid., 515. 103 Ibid., 517. 104 Ibid., 518. 105 Wilhelm Filehne, “Die geometrisch-optischen Täuschungen als nachwirkungen der im körperlichen Sehen erworbenen Erfahrungen” in Zeitschrift für Psychologie und Physiologie der Sinne, vol. 17 (leipzig, 1898), 15–62. 106 Ibid., 21–22. 107 Ibid., 48. 108 Ibid., 19. 109 helmholtz, Handbuch der physiologischen Optik, 321. 110 Wilhelm Bezold, “Über Zerstreuungsbilder auf der netzhaut” in Graefes Archiv für klinische und experimentelle Ophthalmologie, vol. 14, nr. 2 (Berlin, 1868) 1; “when one looks at a glowing point from a distance, for which one has not and cannot adapted to, it appears as a recognizable glowing shape. This is what is termed a circle of confusion of the point because the normal eye would recognize it as the image of a circle. Under such circumstances a more expanded surface expansion reveals faded contours. If the circle of confusion is expanded it appears in a different form and even in a different color as a fragmented image.” 111 Alfred Wilhelm Volkmann, Physiologische Untersuchungen im Gebiet der Optik, issue 1 (leipzig, 1863), 1–51. 112 helmholtz, Handbuch der physiologischen Optik, 326. 113 Adolf Stöhr, Psychologie, 2nd edition (Vienna, leipzig, 1922), 204. 114 helmholtz, Handbuch der physiologischen Optik, 325. 115 Ibid., 340–341. 116 Walter Ehrenstein, “Versuche über die Beziehungen zwischen Bewegungs- und Gestaltwahrnehmung” in Zeitschrift für Psychologie, vol. 96 (leipzig, 1925), 307–308; cesare Musatti, “Sui fenomeni stereocinetici” in Archivio Italiano di Psicologia, vol. 3 (Bologna, 1924), 105–120.

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117 Ernst Wilhelm Brücke, “Über den nutzeffekt intermittierender netzhautreizungen” in Sitzungsberichte der Kaiserlichen Akademie der Wissenschaften. MathematischNaturwissenschaftliche Classe, vol. 49, sec. II (Vienna, 1864), 128–153. 118 Mach, “Über die Wirkung der räumlichen Vertheilung des lichtreiszes auf die netzhaut” in Sitzungsberichte der Kaiserlichen Akademie der Wissenschaften. MathematischNaturwissenschaftliche Classe, vol. 52, sec. II (Vienna, 1865), 303–322. 119 Brücke, “Über den nutzeffekt intermittierender netzhautreizungen”, 128. 120 Ibid., 128. 121 Ibid., 130. 122 Ibid., 138. 123 czermak, “Ideen zu einer lehre vom Zeitsinn” in Sitzungsberichte der Kaiserlichen Akademie der Wissenschaften. Mathematisch-Naturwissenschaftliche Classe, vol. 24, Issue I–III (Vienna, 1857), 236. 124 Ibid., 231. 125 Ibid., 235. 126 Ibid. 127 Ibid. 128 Mach. Leitgedanken meiner naturwissenschaftlichen Erkenntnislehre und ihre Aufnahme durch die Zeitgenossen in Typoskript of the not overworked partial estate of Ernst Mach at the Philosophical Archive at the University of constance. (8.2. 2010 [author]) 129 Mach, “Über das Sehen von lagen und Winkeln durch die Bewegung des Auges. Ein Beitrag zur Psychophysik” in Sitzungsberichte der Kaiserlichen Akademie der Wissenschaften. Mathematisch-Naturwissenschaftliche Classe, vol. 43, sec. II (Vienna, 1861), 215–224. 130 Mach, Typoscript of the not overworked partial estate at the Philosophical Archive at the University of constance, Germany (8. 2.2010 [author]). 131 Mach, “Über das Sehen von lagen und Winkeln durch die Bewegung des Auges. Ein Beitrag zur Psychophysik”, 215. 132 Ibid., 219. 133 Ibid., 218. 134 Vinzenz Dvorak, “Versuche über die nachbilder von Reizveränderungen”, 257–262. 135 Mach, “Über die Wirkung der räumlichen Vertheilung des lichtreizes auf die netzhaut”, 303–322. 136 Ibid., 303. 137 Ibid., 304. 138 Mach, partial estate, constance, Germany (8. 2.2010 [author]). 139 herta Wolf, “Die Divergenz von Aufzeichnen und Wahrnehmen. Ernst Machs erste fotografiegestützte Experimente” in ibid., ed., Diskurse der Fotografie, Fotokritik am Ende des fotographischen Zeitalters, vol. 2 (Frankfurt/Main, 2003), 427–455. 140 Mach, “Über die Wirkung der räumlichen Vertheilung”, 307. 141 Ibid., 308. 142 Ibid., 319. 143 Mach, Die Analyse der Empfindungen und das Verhältnis des Physischen zum Psychischen, 1885, 9th edition (Jena, 1922), 8. 144 Wilhelm Jerusalem, Einleitung in die Philosophie, 7th and 8th editions (Vienna and leipzig, 1919), 59. 145 Mach, “Über den physiologischen Effect räumlich vertheilter lichtreize” (second treatise) in Sitzungsberichte der Kaiserlichen Akademie der Wissenschaften. Mathematisch-Naturwissenschaftliche Classe, vol. 54, sec. II (Vienna, 1866), 131–144. 146 Ibid., 131. 147 Ibid., 131–132. 148 Ibid., 141. 149 Mach, “Über die physiologische Wirkung räumlich vertheilter lichtreize” (third treatise), 393–408.

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Ibid., 393. Ibid., 401–402. Ibid., 405. Ibid., 404. Ibid., 405. Ibid. Ibid. Ibid., 406. As of 1968/69 this topic is picked up by Dan Graham and Peter Weibel and reflected upon in their observer-dependent video-installations with two cameras (to be understood as “eyes”). Mach, “Wozu hat der Mensch zwei Augen” in ibid., Populär-wissenschaftliche Vorlesungen (1896), 4th edition (leipzig, 1910), 90–91. Mach, “Über die physiologische Wirkung räumlich vertheilter lichtreize” (fourth treatise) in Sitzungsberichte der Kaiserlichen Akademie der Wissenschaften. Mathematisch-Naturwissenschaftliche Classe, vol. 57, sec. II (Vienna, 1868), 12. Ibid., 14. Ibid., 18. Ibid., 18–19. Günther Kebeck, Wahrnehmung. Theorien, Methoden und Forschungsergebnisse der Wahrnehmungspsychologie, 2nd edition (Weinheim, Munich, 1997), 70. George Berkeley, “De Motu, Über die Bewegung oder über das Prinzip und die natur der Bewegung und über die Ursache der Bewegungsmitteilung” (1721) in Jürgen habermas, ed., George Berkeley, Schriften über die Grundlagen der Mathematik und Physik, Einleitung von Wolfgang Breidert, Hans Blumenberg (Frankfurt/Main, 1969), 208. Ernst Mach, Grundlinien der Lehre von den Bewegungsempfindungen (1875), reprint (Amsterdam, 1967) 60. Ibid. Ibid. Ibid. Ibid., 61. Ibid., 84–85. Mach, Grundlinien, 26. Peter Weibel, Die Beschleunigung der Bilder in der Chronokratie (Bern, 1987), 113. Mach, Grundlinien, 86–87. Ibid., 85–87. Ibid., 74–75; Wolfgang Metzger, Gesetze des Sehens. Die Lehre vom Sehen der Formen und Dinge des Raumes und der Bewegung, reprint following the 3rd completely overworked edition 1975 (Eschborn 2008), 628–629. Mach, Grundlinien, 54. Mach, Populär-wissenschaftliche Vorlesungen, 35. Arend Kulenkampff, ed., George Berkeley, Eine Abhandlung über die Prinzipien der menschlichen Erkenntnis (hamburg, 2004). Mach, Die Analyse der Empfindungen, 1–30. Mach, Populär-wissenschaftliche Vorlesungen, 60. Mach, Die Analyse der Empfindungen, 177. Jo Baer, “Mach Bands” in Dan Graham, ed., Aspen Magazine, nr. 8/9, 1970. Sigmund Exner, “Über optische Bewegungsempfindungen” in Sonderdruck aus dem Biologischen Centralblatt, vol. VIII, nr. 14 (Erlangen, 1888), 437–438. Exner, “Über die zu einer Gesichtswahrnehmung nöthige Zeit” in Sitzungsberichte der Kaiserlichen Akademie der Wissenschaften. Mathematisch-Naturwissenschaftliche Classe, vol. 58, sec. II (Vienna, 1868), 601–632. Exner, “Experimentelle Untersuchung der einfachsten psychischen Processe: III. Abhandlung, Der Persönlichen Gleichung” part 2 in Pflüger’s Archiv für die gesammte

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Physiologie des Menschen und der Thiere, 11 (Bonn, 1875), 406. Ibid., 407–408. Ibid., 408–409. Ibid., 411. Exner, “Über das Sehen von Bewegungen”, 156–191. Ibid., 156. Karl Vierordt, Zeitsinn (Tübingen, 1868). Exner, “Über das Sehen von Bewegungen”, 159. Ibid., 164. Julius hirschberg, ”Die optik der alten Griechen” in Zeitschrift für Psychologie und Physiologie der Sinnesorgane, vol. 16 (leipzig, 1898), 322. Exner, “Über das Sehen von Bewegungen”, 166–167. Ibid., 171–172. Ibid., 165. Exner, “Über die optischen Bewegungsempfindungen”, 440. Ibid., “Experimentelle Untersuchungen der einfachsten psychischen Processe, IV Abhandlung” in Pflüger’s Archiv für die gesammte Physiologie des Menschen und der Thiere, 11 (Bonn, 1875), 581–602. Ibid., 593. Exner, Einige Beobachtungen über Bewegungsnachbilder. Sonderdruck aus Centralblatt für Physiologie (leipzig, 1887), 3–4. Exner, “Über das Sehen von Bewegungen”, 157. Exner, Entwurf zu einer physiologischen Erklärung der psychischen Erscheinungen (leipzig, Wien, 1894), 224. Mach, Die Analyse der Empfindungen, 23. Exner, “Über das Sehen von Bewegungen”, 159. Ibid., 157. Ibid. Exner, “Über autokinetische Empfindungen” in Zeitschrift für Physiologie und Psychologie (leipzig 1896), 313–330. Gottfried Schweizer, “Über das Sternschwanken” in Bulletins de la Soc. Imp. des naturalistes de Moscou, nr. II (Moscow 1858), 17, quote taken from Sigmund Exner, “Über autokinetische Empfindungen”, 315 ff. Ibid., 317. Johann hoppe, Die Schein-Bewegungen (Würzburg, 1879). Ibid., preface without page number. Ibid., 9. Ibid. Ibid.,12. Ibid., 15. Ibid., 22. Wilhelm Stern, “Die Wahrnehmung von Bewegungen vermittelst des Auges” in Zeitschrift für Psychologie und Physiologie der Sinnesorgane, vol. 7 (hamburg, leipzig, 1894), 338–339. hoppe, Die Schein-Bewegungen, 210. otto Fischer, “Psychologische Analyse der stroboskopischen Erscheinungen” in Philosophische Studien III (leipzig, 1886), 128–156. Adolph Poppe, “Das verbesserte Interferenzoskop” in Annalen der Physik und Chemie, vol. 164 (leipzig, 1853), 223–230. heinrich Gustav Magnus, “hydraulische Untersuchungen” in Annalen der Physik und Chemie, vol. 171 (leipzig, 1855), 18. Johannes Müller, “Anwendung der stroboskopischen Scheibe zur Verräumlichung der Grundgesetze der Wellenlehre” in Annalen der Physik und Chemie, vol. 143 (leipzig, 1846), 271–272.

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Salomon Stricker, Studien über Bewegungsvorstellungen (Wien, 1882). Fischer, Psychologische Analyse, 152. Ibid. Ibid., 149. James McKeen cattell, “Über die Trägheit der netzhaut und des Sehcentrums” in Philosophische Studien III (leipzig, 1886), 94–127. Ibid., 122. Stern, “Die Wahrnehmung von Bewegungen vermittelst des Auges” in Zeitschrift für Psychologie und Physiologie der Sinnesorgane, vol. 7 (leipzig, 1894) 321–385. Ibid., 329. Ibid., 332. Ibid., 334. Ibid., 335. Ibid., 342. Ibid., 350–352. Ibid., 353–354. Ibid., 354. Ibid., 355. Ibid. Alfred Borschke and leo hescheles, “Über Bewegungsnachbilder” in Zeitschrift für Psychologie und Physiologie der Sinnesorgane, vol. 27 (leipzig, 1902), 386–398. Ibid., 391. Ibid., 395. Ibid., 395–397. Adolf Szily, “Bewegungsnachbild und Bewegungskontrast” in Zeitschrift für Physiologie und Psychologie, vol. 38 (leipzig, 1905), 81–154. Ibid., 82. Ibid., 88. Ibid., 90–99. Ibid., 90–91. Johann Georg Zehfuss, “Über Bewegungsnachbilder” in Annalen der Physik und Chemie, vol. 9 (leipzig, 1880), 672–673. Ibid., 98. Adolf Basler, “Über das Sehen von Bewegungen” in Pflüger’s Archiv, vol. 128 (Bonn, 1908), 145–176. Ernst Fleischl-Marxow, “Physiologisch-optische notizen” in Sitzungsberichte der Kaiserlichen Akademie der Wissenschaften. Mathematisch-Naturwissenschaftliche Classe, vol. 86, sec. III (Vienna, 1883), 8. oppel, “neue Beobachtungen und Versuche über eine eigenthümliche, noch wenig bekannte Reactionsthätigkeit des menschlichen Auges” in Annalen der Physik und Chemie, vol. 175 (leipzig, 1856), 540–561. Zehfuss, 672–673. Ernst Budde, “Über Metakinetische Scheinbewegungen und über die Wahrnehmung der Bewegung” in Archiv für Anatomie und Physiologie (Berlin, 1884), 127–144. hoppe, “Studie zur Erklärung gewisser Scheinbewegungen” in Zeitschrift für Psychologie und Physiologie der Sinnesorgane, vol. 7 (leipzig, 1894), 29–35. Richard cords, Ernst Theodor Brücke, Über die Geschwindigkeit des Bewegungsnachbildes” in Pflüger’s Archiv, vol. 119 (Bonn, 1907), 54–61. Basler, “Über das Sehen von Bewegungen”, 172–173. Ibid., 174. Vittorio Benussi, “Gesetze der inadäquaten Gestaltauffassung. Die Ergebnisse meiner bisherigen experimentellen Arbeiten zur Analyse der sog. geometrisch-optischen Täuschungen (Vorstellung außersinnlicher Provenienz)” in Archiv für die gesamte Psychologie, vol. 32 (leipzig, 1914), 396–419.

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263 Benussi, “Über die natur der sogenannten geometrisch-optischen Täuschungen”, 1905 reprint in Mauro Antonelli, ed., Psychologische Schriften, Textkritische Ausgabe in zwei Bänden (Amsterdam, new York, 2002), 139–146. Ibid., “Die intellektuellen Grundeinstellungen und ihre Gegenstände (1905), reprint (Amersterdam, new York, 2002), 147–153; Ibid., “Gesetz der inädequaten Gestaltauffassung. Die Ergebnisse meiner bisherigen experimentellen Arbeiten zur Analyse der sog. geometrisch-optischen Täuschungen (Vorstellung außersinnlicher Provenienz)” in Archiv für die gesamte Psychologie, vol. 32 (leipzig, 1914), 341–364. 264 Benussi, “Über die Motive der Scheinkörperlichkeit bei umkehrbaren Zeichnungen” in Archiv für die gesamte Psychologie, vol. 20 (leipzig, 1911), 363–396. 265 Ibid., 363. 266 heinrich hanselmann, Über optische Bewegungswahrnehmung (Zurich, 1911). 267 Ibid., 12–14. 268 Johannes Müller, Phantastische Gesichtserscheinungen (coblenz, 1826). 269 hanselmann, Über optische Bewegungswahrnehmung (Zurich, 1911), 15. 270 Müller, Phantastische Gesichtserscheinungen, 64. 271 Benussi, “Stroboskopische Scheinbewegungen und geometrisch-optische Gestalttäuschungen”, Archiv für die gesamte Psychologie, vol. 24 (leipzig, 1912), 31–62. 272 Wilhem Wundt, Grundzüge der Physikalischen Psychologie, vol. 2 (leipzig, 1911), 623–624. 273 Benussi, “Stroboskopische Scheinbewegungen”, 46–47. 274 Ibid., 48. 275 Kurt Koffka, “Beiträge zur Psychologie der Gestalt- und Bewegungserlebnisse, Einleitung” in Zeitschrift für Psychologie (leipzig, 1913), 353–358. Friedrich Kenkel, “Untersuchungen über den Zusammenhang zwischen Erscheinungensgröße und Erscheinungsbewegung bei einigen sogenannten optischen Täuschungen” in Zeitschrift für Psychologie (leipzig, 1913), 353–358. 276 Benussi, “literaturberichte zu Koffka-Kenkel, Beiträge zur Psychologie der Gestalt- und Bewegungserlebnisse (1913)” in Archiv für die gesamte Psychologie, vol. 32 (leipzig, Berlin, 1914), 50–57. 277 Koffka, “Zur Grundlegung der Wahrnehmungspsychologie. Eine Auseinandersetzung mit V. Benussi. Beiträge zur Psychologie der Gestalt- und Bewegungserlebnisse”, in Zeitschrift für Psychologie und Physiologie der Sinnesorgane (leipzig, 1915), 11–90. Benussi’s reaction to this can be found in a footnote: Benussi, “Über Scheinbewegungskombination (lissajoussche S-, M- und E-Scheinbewegungsfiguren), in Archiv für die gesamte Psychologie, vol. 37 (leipzig, 1918). 243. 278 Benussi, “Kinematohaptische Scheinbewegung (KBS) und Auffassungsumformung” in Archiv für die gesamte Psychologie, vol. 32 (leipzig, Berlin, 1914), 31. 279 Ibid. 280 Ibid., 33. 281 Benussi, “Über Scheinbewegungskombination”, 266–267. 282 Ibid., 273. 283 James Fraser, “A new Visual Illusion of Direction” in British Journal of Psychology, nr. 3, Jan. 1908, 307–337. 284 Benussi, “Über Scheinbewegungskombination”, 274–275. 285 Ibid., 282. 286 Benussi, “Zur experimentellen Grundlegung hypno-suggestiver Methoden psychischer Analyse” in Psychologische Forschung, vol. 9 (Berlin, 1927), 216. 287 Ibid., 216–218. 288 Max Wertheimer, “Experimentelle Untersuchungen zur Tatbestandsdiagnostik” in Archiv für die gesamte Psychologie (Universität Würzburg, 1905), vol. 6 (leipzig, 1905), 59–131. 289 Wertheimer, “Experimentelle Studien über das Sehen von Bewegung” in Zeitschrift für Psychologie und Physiologie der Sinnesorgane, vol. 61 (leipzig, 1912), 161–265.

290 Friedrich Schumann, “Beiträge zur Analyse der Gesichtswahrnehmungen I.” in Zeitschrift für Psychologie und Physiologie der Sinnesorgane, vol. 23 (leipzig, 1900), 30. 291 Josef Klemens Kreibig, “Über Wahrnehmung” in Sitzungsberichte der Kaiserlichen Akademie der Wissenschaften in Wien, Philosophisch-Historische Klasse, vol. 168, sec. 6 (Vienna, 1911), 11; Ibid., Die intellektuellen Funktionen (Vienna, 1909), 111ff. 292 Wertheimer, Über Gestalttheorie (Erlangen, 1925), 43. 293 Raimund Dehmlow, “Der Fall Wertheimer oder otto Gross als Verführer” in Bohème, Psychoanalyse und Revolution, R. Dehmlow, G. heuer, ed., 3. Internationaler otto Gross Kongress (Marburg, 2003), 81–90. 294 Viktor Sarris, Max Wertheimer in Frankfurt. Beginn und Aufbaukrise der Gestaltpsychologie Lengerich (Berlin Riga Scottsdale Wien Zagreb, 1995), 286–287. 295 Wertheimer, “Experimentelle Studien über das Sehen von Bewegung”, 169. 296 Ibid. 297 Ibid., 173–174. 298 Ibid., 177. 299 Ibid., 165. 300 Ibid., 166. 301 Ibid. 302 Ibid., 248–252. 303 Ibid., 186–190. 304 Ibid., 192. 305 Junius F. Brown, Albert c. Voth, “The Path of Seen Movement as a Function of the Vector-Field” in The American Journal of Psychology, vol. 49, nr. 4 (oct. 1937), 544. 306 Ibid., 562. 307 Ibid., 562–563. 308 Karl Duncker, “Über induzierte Bewegung” in Psychologische Forschung, Zeitschrift für Psychologie und ihre Grenzwissenschaften (Berlin, 1929), 180–259. 309 Ibid., 182. 310 Ibid., 246. 311 herbert Kleint, “Über die orientierung im Raum” in Bericht über den X. Kongress für experimentelle Psychologie (Jena, 1928), 131. 312 Dunker, Zur Psychologie des produktiven Denkens (Berlin, 1935). 313 Kleint, “Versuche über die Wahrnehmung” in Zeitschrift für Psychologie, vol. 138 (leipzig, 1936), 1–34; Ibid., vol. 140 (leipzig, 1937), 109–138; Ibid., vol. 141 (leipzig, 1937), 9–44; Ibid., vol. 134 (leipzig, 1938), 259–316. 314 Ibid., vol. 138, 1. 315 Ibid., 8. 316 Ibid., 11. 317 Ibid. 318 Ibid., 9. 319 Ibid., 32. 320 Ibid., 33. 321 Ibid., vol. 141, 29. 322 Ibid., 12. 323 Bruce Goldstein, Wahrnehmungspsychologie (heidelberg, Berlin, oxford, 1997), 1–2. 324 Ibid., 3–27. 325 Ivo Kohler, Über Aufbau und Wandlungen der Wahrnehmungswelt (Wien, 1951), 7. 326 heinrich Kottenhoff, Was ist richtiges Sehen mit Umkehrbrillen und in welchem Sinn stellt sich das Sehen um? (Meisenheim am Glan, 1961). 327 Johannes Müller, Handbuch der Physiologie des Menschen, 357. 328 George Berkeley, An Essay Towards a New Theory of Vision (1709) reprint (london, 1961). 329 Franz Bruno hoffmann, “Die lehre vom Raumsinn des Auges”, vol. 2 (Berlin, 1925), 356–360.

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330 Mach, “Wozu hat der Mensch zwei Augen?”, 93. 331 Hubert Dolezal, Living in a World Transformed (Caldwell New Jersey, 1982), 266–267. 332 Geroge M. Stratton, “Some Preliminary Experiments on Vision without Inversion of the Retinal Image” in Psychological Review III, Nov. 6 (1896), 611. 333 Stratton, “The Spatial Harmony and Sight” in Mind, 8 (32) (1899), 492–505; Ibid., Experimental Psychology and its Bearing upon Culture (1903) reprint (New York London, 1914), 148–149. 334 Stratton, “The Spatial Harmony and Sight”, 149; Max Ettlinger, “Literaturberichte zu Strattons Umkehrbrillen-Experimenten” in Zeitschrift für Psychologie und Physiologie der Sinnesorgane, vol. 18 (Leipzig, 1899), 130–140. 335 Wilhelm Stern, “Kongressbericht zu Strattons Umkehrbrillen” in Zeitschrift für Psychologie und Physiologie der Sinnesorgane, vol. 18 (Leipzig, 1898), 252–255. 336 Natalie Förster, “Die Wechselbeziehung zwischen Gesichts- und Tastsinn bei der Raumwahrnehmung”, Psychological Research, vol. 13, nr. 1 (Jan. 1930), 64–78. 337 Ibid., 66. 338 Ibid., 76–78. 339 Margaret Wooster, “Certain factors in the Development of a New Spatial Coordination” in Psychological Monographs, nr. 32 (Princeton, 1923). 340 Karl Scholl, “Vom Zielen und Zeigen” in Zeitschrift für die gesamte Neurologie und Psychiatrie, nr. 97 (Berlin, 1925), 217–236. 341 Kohler, Über Aufbau und Wandlungen der Wahrnehmungswelt, 16. 342 Harry Ewert, “A Study of the Effect of Inverted Retinal Stimulation upon Spatially Coordinated Behaviour” in Genetic Psychological Monographs 7 (1930), 177–363. 343 Kottenhoff, Was ist richtiges Sehen, 39. 344 Gordon G. Brown, “Perception of Depth with Disoriented Vision” in British Journal of Psychology, vol. 19 (1928), 117–146. 345 Franz Hillebrand, “Zur Theorie der stroboskopischen Bewegungen” in Zeitschrift für Psychologie, vol. 90 (Leipzig, 1922), 28. 346 Friedrich Schumann, ed., “Bericht über den IV Kongress für experimentelle Psychologie in Innsbruck” (Leipzig, 1911), 283–312. 347 Kohler, Über Aufbau und Wandlungen, 8. 348 Ibid., 10. 349 Ibid., 19. 350 Rudolf Arnheim, Kunst und Sehen (Berlin, 1954), 71. 351 Eckard H. Hess, “Space Perception in the Chick” (1956), reprint in Perception, Mechanism and Models, Scientific American (San Francisco, 1971), 367–371. 352 Walter Lembecker, “Berkeleys Theorie der Gesichtswahrnehmng, beurteilt auf Grund der modernen Psychologie”, dissertation (University Rostock, 1929), 31. 353 S. Hirokazu Yoshimura, “A Historical Review of Long-Term Visual-Transposition Research in Japan”, Psychological Research, vol. 59, nr. 1, 1996, 16–32. 354 Irvin Rock, Charles S. Harris, “Vision and Touch” (1967), reprint in Perception: Mechanisms and Models in Scientific American (San Francisco, 1971), 268–277. 355 Franz Bruno Hoffmann, Die Lehre vom Raumsinn des Auges, vol. 2 (Berlin, 1925). 356 Hubert Dolezal, Living in a World Transformed, 59–79. 357 Ibid., 81–108. 358 David Linden, “Spatial Analysis in the Human Cerebral Cortex: Behavioural and Functional Magnetic Resonance Studies of Spatial Transformations in Visual Perception and Imagery” (dissertation, Frankfurt/Main, 1999). 359 Linden, Ulrich Kallenback et al., eds., “The Myth of Upright Vision. A Psychophysical and Functional Imaging Study of Adaptation to Inverting Spectacles” in Perception, vol. 28 (1999), 469–481. 360 Answer per email received by the author. Dated February 23, 2009. 361 Theodor Erismann, Allgemeine Psychologie. Experimentelle Psychologie und ihre Grundlagen, part 2, new edition (Berlin, 1962), 82.

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Mach, “Über die Wirkung der räumlichen Vertheilung”, 320. David Marr, Vision, (New York, 1982), 8. Ibid. Romana Schuler, “Ernst Machs Forschungen mit Wahrnehmungsapparaten und ihre ‘Reprisen’ in der frühen Videokunst von Dan Graham und Peter Weibel” in Ludger Schwarte, ed., Kongress-Akten, Experimentelle Ästhetik, vol. 2 (2012); http://www.dgae.de/kongress-akten.html. Ibid., “The Experiments of Perception in Science and Art by Ernst Mach, Dan Graham and Peter Weibel” in Harald Klinke, ed., Art Theory as Visual Epistemology (Cambridge, 2014), 125–144. Karl Wilhelm Wolf-Czapek, Die Kinematographie, Wesen, Entstehung und Ziele des lebenden Bildes (Dresden, 1908) Ibid., 108. Manfred Waffender, ed., Cyberspace-Ausflüge in virtuelle Wirklichkeiten (Reinbek bei Hamburg, 1999), 66–89. Peter Weibel, Zur Geschichte und Ästhetik der digitalen Kunst, supplement catalog Ars Electronica 84 (Linz, 1984). Ibid., 6. Manfred Fahle, “Ästhetik als Teilaspekt menschlicher Wahrnehmung”, 63, in Ralf Schnell, ed., Wahrnehmung, Kognition, Ästhetik (Bielefeld, 2005) . Gerhard Roth, Das Gehirn und seine Wirklichkeit (Frankfurt/Main, 1997), 78–87. Béla Julesz, “Binocular Depth without Familiarity Cues” (1964); reprint in M. D. Vernon, ed., “Experiments in Visual Perception, Selected Readings” (Baltimore, Harmonsdworth, Ringwood, 1966) 77–83; Julesz, “Texture and Visual Perception” (1965), reprint in Perception: Mechanisms and Models in Scientific American (1972), 183–194. Marr, Vision. Ibid., 264–313. Niklas Maak, “Neuorästhetik, Ich messe das, was du nicht siehst”, Frankfurter Allgemeine Zeitung, Oct. 22, 2009, http://www.faz.net/aktuell/feuilleton/kunst/neuroaesthetik-ichmesse-das-was-du-nicht-siehst–1872671.html (accessed Dec. 26, 2011); Semir Zeki, Glanz und Elend des Gehirns, Neurobiologie im Spiegel von Kunst, Musik und Biologie (Munich, Basel, 2010). Maxwell Bennett, “Epilog”, Neurowissenschaft und Philosophie, Maxwell Bennett, Daniel Dennett, Peter Hacker, John Searle, mit Einleitung und Schlussbetrachtungen von Daniel Robinson (2007) (Berlin, 2010), 244. Ernst Pöppel, Der Rahmen. Ein Blick des Gehirns auf unser Ich, 2006 (Munich, 2010), 183–213. Czapek-Wolf, Die Kinematographie, Wesen, Entstehung und Ziele des lebenden Bildes, 102–108. Hans Scheugl, Ernst Schmidt Jr., Eine Subgeschichte des Films, Lexikon des Avantgarde-, Experimental- und Undergroundfilms, vol. 1 (Frankfurt/Main, 1974), 253–259. Theodor Dahmen, Die Theorie des Schönen. Vom Bewegungsprinzip abgeleitete Ästhetik (Leipzig, 1903). Marcel Duchamp, “Effemeridi su e intorno a Marcel Duchamp e Rose Sélavy, 1887–1968” in Jennifer Gough-Cooper, Jacques Caumont, eds., Marcel Duchamp (Milano, 1993). Ibid. Ibid., Diary entry dated November 8, 1924. Calvin Tomkins, Marcel Duchamp. Eine Biografie (Munich, Vienna, 1999), 105–125. Herbert Molderings, “Ästhetik des Möglichen. Zur Erfindungsgeschichte der Readymades Marcel Duchamps” in Gert Mattenklott, ed., Ästhetische Erfahrung im Zeichen der Entgrenzung der Künste (Hamburg, 2004), 126–127. Ibid., 127. Stefan Rieger, Kybernetische Anthropologie. Eine Geschichte der Virtualität (Frankfurt/Main, 2003). Warren McCulloch, Verkörperung des Geistes (in English 1965) (Vienna, 2000).

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390 Max Bense, Kybernetik oder die Metatechnik einer Machine (1951), in ibid., Ausgewählte Schriften, vol. 2 (Stuttgart, Weimar, 1998). 391 Ulric Neisser, Kognition und Wirklichkeit, Prinzipien und Implikationen der kognitiven Psychologie (English first edition, 1976) (Stuttgart, 1979), 13. 392 Peter Weibel, “Transformationen der Techno-Ästhetik” in Florian Rötzer, ed., Digitaler Schein, Ästhetik der elektronischen Medien (Frankfurt/Main, 1991) 205–246. 393 Jeffrey Shaw, Peter Weibel, eds., Future Cinema, The Cinematic Imaginary After Film (Cambridge, London, 2003), 594. Woody Vasulka, Peter Weibel, eds., Buffalo Heads: Media Practice, Media Pioneers, 1973–1990 (Cambridge, London, 2008), 472–481. 394 Shaw, “A User’s Manual”, From Expanded Cinema to Virtual Reality, exhibition catalog, ZKM, Neue Galerie Graz (Ostfildern, 1997), 62, 162. 395 A detailed list of the respective collective cooperation for the projects can be found in ibid., 59–171 and under http://www.jeffrey-shaw.net/ and for work that was created after 2002: http://www.icinema.unsw.edu.au/ (accessed Aug. 29, 2011) 396 Florian Rötzer, Peter Weibel, eds., “Reisen in virtuellen Realitäten, im Gespräch mit Florian Rötzer” in Cyberspace. Zum medialen Gesamtkunstwerk (Munich, 1993), 332. 397 The technical details on hard- and software can be found on the ZKM website: http://on1.zkm.de/zkm/werke/EVE-ExtendedVirtualEnvironment. 398 http://www.guilgreyshkul.com/VanDerBeek/_PDF/moviedromefinal_PDF_LORES.pdf 399 Gloria Sutton, “Stan VanDerBeek’s Movie Drome: Networking the Subject” in Shaw, Weibel, eds., Future Cinema, 137. 400 Stan VanDerBeek, “Culture-Intercom and Expanded Cinema, A Proposal and Manifesto”, http://www.guilgreyshkul.com/VanDerBeek/_PDF/CultureIntercom1,2,3_PDF_LORES. pdf 401 Neil Brown, Dennis Del Favero, Jeffrey Shaw, Peter Weibel, “Interactive Narrative as a Multi-temporal Agency” in Shaw, Weibel, eds., Future Cinema, 312–315. 402 Mark B.N. Hansen, New Philosophy for New Media (Cambridge MA, London, 2006), 42–92, 116–176; Gilles Deleuze, Das Bewegungs-Bild, Kino 1 (Frankfurt/Main, 1983); Heinrich Klotz, Peter Weibel, eds., Jeffrey Shaw – eine Gebrauchsanweisung, 17–18. 403 Umberto Boccioni, “Bildnerischer Dynamismus” (presentation Dec. 15, 1913), Hansgeorg Schmidt-Bergmann, ed., Futurismus. Geschichte, Ästhetik, Dokumente (Reinbek bei Hamburg, 1993), 323. 404 Alfons Schilling, Ich, Auge, Welt. The Art of Vision (Wien, New York, 1997), 42–43. 405 Conversation with Alfons Schilling, May 2006. 406 Kottenhoff, Was ist richtiges Sehen?, 131. 407 Ibid. 408 Peter Noever, Oswald Oberhuber, eds., Sehmaschinen, Alfons Schilling (Vienna, 1987). 409 Woody Vasulka, Peter Weibel, ed., ”Five Lectures” in Woody Vasulka and Peter Weibel, eds., Buffalo Heads: Media Study Media Practice, media Pioneers 1973–1990, exhibition catalog ZKM (Karlsruhe, Cambridge MA, London, 2008), 419. 410 Neisser, Kognition und Wirklichkeit, Prinzipien und Implikationen der kognitiven Psychologie, 89. 411 Ibid., 111. 412 http://www.dma.ufg.ac.at/app/link/Grundlagen%AAllgemeine/module/13916?step=all 413 Edward C. Tolmann, “Cognitive Maps in Rats and Men”, in Psychological Review, nr. 55 (1948), 189–208. 414 Schilling, “Electronic Space” in exhibition catalog Alfons Schilling, Ich, Auge, Welt (Vienna, New York, 1997), 130–133. 415 Weibel in ibid., 115–124. 416 Schilling, “Über Sehen sprechen, im Gespräch mit Christan Reder” in Peter Noever, Oswald Oberhuber, eds., Sehmaschinen, Alfons Schilling, in exhibition catalog MAK (Vienna, 1987), 12. 417 Ibid. 418 Ibid.

419 Julesz, “Adaptation in a Peephole: A Text on Theory of Preattentive Vision” in lothar Spillmann, Bill R. Wooten, eds., Sensory Experience, Adaptation, and Perception, Festschrift for Ivo Kohler (hillsdale, nJ, 1984), 37–52. 420 Paul Feyerabend, Wider den Methodenzwang. Skizzen einer anarchistischen Erkenntnistheorie (Frankfurt/Main, 1976). 421 Peter Weibel in conversation with the author and Thomas Feuerstein in Feuerstein, Schuler, eds., Teletopologie Österreich – Materialien zur Medienkunst (Vienna, 1994), 85. 422 Weibel, “Mediendichtung, Arbeiten in den Medien Sprache, Schrift, Papier, Stein, Foto, Ton, Film und Video aus zwanzig Jahren” in otto Breicha, ed., Protokolle, Zeitschrift für Literatur und Kultur, vol. 2 (Munich, 1982), Weibel designed the cover Medieindichter for an earlier book project on his work in 1969; Weibel, Das Offene Werk, 1964–1979 (ostfildern, 2007), 318–319. 423 Weibel, ed., Wien Bildkompendium. Wiener Aktionismus und Film (Frankfurt/Main, 1970). 424 Weibel, “Zeit der Transition. Avantgarde zwischen Kunst und Massenkultur” in Gottfried Schlemmer, ed., Werkstatt, Aspekt 2 (Wien, 1966), 7. 425 Ibid., 7–9. 426 Weibel, Neuer Österreichischer Film (Vienna, 1970), 100. 427 Romana Schuler, “Ernst Machs Forschungen mit Wahrnehmungsapparaten und ihre Reprisen in der frühen Videokunst von Dan Graham und Peter Weibel” in ludger Scharte, ed., Kongress-Akten, Experimentelle Ästhetik, vol. 2 (January 2012) 428 Weibel, “Äußerungen auf Tonband” (June 1974) in Kellerkino, Materialien zu den Filmen 1974 (Bern, 1974), 171–172. 429 Weibel, “Mediendichtung”, 63. 430 hillebrand, “Zur Theorie der stroboskopischen Bewegungen” in Zeitschrift für Psychologie, vol. 90 (leipzig, 1898), 28–29. 431 hans Preiner in a conversation with the author, Teletopologie Österreich – Materialien zur Medienkunst (1994), 120. 432 Weibel, “Mediendichtung”, 79. 433 Ibid., 675. 434 Thomas Dreher, Peter Weibel – Polykontextualität in reaktiver Medienkunst in Romana Schuler, ed., Peter Weibel – Bildwelten (Wien, 1996), 33–62. ludwig Seyfarth, Kunsttheorie als Schnittstellentheorie. Zum veränderten Status von Kunst und Ästhetik im digitalen Zeitalter am Beispiel der Schriften von Peter Weibel in Ibid., 19–32. claudia Giannetti, Endo-Aesthetics, http://www.medienkunstnetz.de/themes/aesthetics_of_the_digital/endo-aesthetics/ (accessed nov. 17, 2011), ZKM (Karlsruhe, 2004). 435 Mach, Erkenntnis und Irrtum. Skizzen zur Psychologie und Forschung (leipzig, 1905), 454. 436 Weibel, “Mediendichtung”, 173. 437 Weibel, “Virtuelle Realität oder der Endo-Zugang zur Elektronik” in Rötzer, Weibel, eds., Cyberspace, 37–43. 438 Weibel, Malerei und Geometrie in Zeichen im Fluß, Museum Moderner Kunst (Wien, 1990), 114. 439 Mach, “Über die physiologische Wirkung”, 389. 440 otto Rössler, “Endophysik – Physik von innen” in Karl Gerbel, Peter Weibel, eds., catalog Die Welt von innen, Endo und Nano (linz, 1992), 49–55. 441 niklas luhmann, Soziale Systeme, Grundriß einer allgemeinen Theorie (Frankfurt/Main, 1984); Ibid., Kunst der Gesellschaft (Frankfurt/Main, 1995). 442 Weibel, “Endo & nano. Über die Grenzen des Realen”, 8–12 and “Unsere Regenbogenwelt” in Weibel, Gerbel, eds., catalog Die Welt von innen, 13–21. 443 Weibel, “Postontologische Kunst: Virtualität, Variabilität, Viabilität”, typoscript (June, 1993) in Schuler, ed., Peter Weibel – Bildwelten, 242; Weibel, “Die Welt der Virtuellen Bilder. Zur Konstruktion kontextgesteuerter Ereigniswelten” in Camera Austria, nr. 46

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(Graz, 1994), 42–51. 444 Robert Bunsen, Florian M. Schwandner, Gasmetrische Methoden (Frankfurt/Main, 2005), 5–16. 445 Weibel, “The Art of Interface Technology” in hans Diebner, ed., Science of the Interface (ZKM Karlsruhe, 2001), 275. 446 Robert J. Scully, The Demon and the Quantum. From the Pythagorean Mystics to Maxwell’s Demon and Quantum Mystery (Berlin, 2007), 69–70. 447 Weibel, “Die Welt der Virtuellen Bilder”, 44; see Peter Teichgräber, ed., catalog Peter Weibel, Hypothetische Produkte, Vom Elend der Privilegien (Wien, 1994). 448 Semir Zeki, Glanz und Elend des Gehirns, Neurobiologie im Spiegel von Kunst, Musik und Biologie (Munich, Basel, 2010), 215. 449 Weibel, “Theater der thermalen Perzeption”, in Neuer Österreichischer Film, 100. 450 Ibid. 451 Weibel, “Pillenfilm oder der Sinnesdiskorrelator” in Supervisuell, nr. 2, February (Zurich, 1968). 452 Weibel, “Intelligent Image”, lecture held 1.23.1996 in Budapest. http://www.c3.hu/hu/scca/butterfly/Weibel/synopsis/html (accessed 11.1.2011) 453 Schuler, “Peter Weibel – Die Wiederkehr des Verdrängten (2011)”, Essay über Peter Weibel, http://peterweibel.at/index.php?option=com_content&view=article&id= 118&catid=9Itemid=7 (accessed nov. 15, 2011). 454 Weibel, “neurocinema. Zum Wandel der Wahrnehmung im technischen Zeitalter”, Brigitte Felderer, ed., in Katalog Wunschmaschine – Welterfindung (Wien, new York, 1996), 167–184. Further remarks: Weibel, “The Art of Interface Technology” in Dieber, ed., Sciences of Interface, 279–280.; Weibel, “The Intelligent Image: neurocinema or Quanten cinema?” in Shaw, Weibel, eds., Future Cinema, 594–601. 455 Weibel, “neurocinema. Zum Wandel der Wahrnehmung im technischen Zeitalter”, 183. 456 Schuler, “Peter Weibel – Die Wiederkehr des Verdrängten”. 457 Karl Bühler, “Erscheinungsweisen der Farben” in Handbuch der Psychologie, nr. I (Jena, 1922), 97. 458 Egon Brunswik, Wahrnehmung und Gegenstandswelt: Grundlegung einer Psychologie vom Gegenstand her (leipzig, 1934). 459 Fritz heider, Ding und Medium (1926) (Berlin, 2005). 460 Elisabeth von Samsonow, “leben und Tod der natur. Überlegungen zur Mechanik leonardo da Vincis” in Rötzer, ed., Digitaler Schein, Ästhetik der elektronischen Medien, 432–433. 461 Thomas S. Kuhn, Die Struktur wissenschaftlicher Revolutionen (Frankfurt/Main, 1976), 166–168. Kuhn’s ideas were further developed by James W. McAllister who also cites reasons such as these views that can change over time. James W. McAllister, “The Truth and Beauty in Scientific Reason” in Synthese, vol. 78, nr. 1 (new York, Vienna, 1998), 25– 51. 462 hans-Jörg Rheinberger, “nichtverstehen und Forschen” in Juerg Albrecht, Jörg huber et al, eds., Kultur nicht verstehen: produktives Nichtverstehen und Verstehen als Gestaltung (Zurich, 2005), 75–81.

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Fig. 90 herbert Kleint in Zeitschrift für Psychologie, vol. 138, 1936. Fig. 92, 95d-f, 96 heinrich Kottenhoff, Was ist richtiges Sehen mit Umkehrbrillen?, 1961. Fig. 95, 95b, 97a-b, 98, 100 Ivo Kohler, Über Aufbau und Wandlungen der Wahrnehmungswelt, 1951. Fig. 97c, 101, 102-104 in American Scientific Journal. Fig. 105a-b, 106 hubert Dolezal, Living in a World Transformed, 1982. Fig. 119 120a, 120b, 120d, 122a-c, 124, 126a-c, 126e-f, 128a-d, 131-132, 134-138 Archive Jeffrey Shaw. Fig. 120c, 120e, 123, 125 Eventstructure Research Group. Fig. 121a-c Pieter Boersma. Fig. 126d Bob van Dantzig. Fig. 127a-b oscar van Alphen. Fig. 133 Franz Womhof. Fig. 129a-c Marco caselli. Fig. 130 Bob van Dantzig. Fig. 139-143, 145-153b, 154a-b, 155, 157a-b Estate archive by Alfons Schilling, Vienna. Fig. 156a-b Ivan Sutherland, University of Utah. Fig. 156c Paul Bach-y-Rita. Fig. 158-165, 170a-b, 171b-c, 172-173a, 173c, 176, 179, 183a-b, 187a, 190b-c, 191, 193 Archive Peter Weibel. Fig. 174a-b Mala Galerie, Warschau. Fig. 169, 175a-e, 181a-b, 185-186 Michael Schuster. Fig. 166 Peter Weibel, Valie Export © Bildrecht, Wien, 2015. Fig. 167 Valie Export © Bildrecht, Wien, 2015. Fig. 168a-c Barbara Woellwarth. Fig. 177 Dieter Bogner. Fig. 180 Dora Maurer. Fig. 182a-c Philipp Schönborn. Fig. 184a-b A. Palacios nunez. Fig. 187b Alexander Ströck. Fig. 188 Teri Wehn-Damisch. Fig. 189 Thomas Dreher. Fig. 190a, 192 Galerie Tanja Grunert and Michael Jansen, Köln. Fig. 194a-c Fritz Simak. Fig. 195a-c Jens Barth.