The psychology of perception: a philosophical examination of Gestalt Theory and derivative theories of perception 9781315473284, 1315473283

Table of contents :
Editorial Preface. 1. Introduction 2. Explanation in the Psychology of Perception 3. The Historical Background of Gestalt Psychology 4. Gestalt Theory 5. Further Developments 6. Functionalism 7. Conclusion. Bibliography. Index.

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PSYCHOLOGY LIBRARY EDITIONS: PERCEPTION

Volume 13

T H E PSY C H O L O G Y OF P E R C E PT IO N

THE PSYCHOLOGY OF PERCEPTION A Philosophical Examination of Gestalt Theory and Derivative Theories of Perception

D. W. HAMLYN

First published in 1957 by Routledge & Kegan Paul Ltd This edition first published in 2017 by Routledge 2 Park Square, Milton Park, Abingdon, Oxon OX14 4RN and by Routledge 711 Third Avenue, New York, N Y 10017 Routledge is an imprint o f the Taylor & Francis Group, an informa business © 1957 Routledge & Kegan Paul Ltd All rights reserved. N o part of this book may be reprinted or reproduced or utilised in any form or by any electronic, mechanical, or other means, now known or hereafter invented, including photocopying and recording, or in any information storage or retrieval system, without permission in writing from the publishers. Trademark notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation without intent to infringe. British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library ISBN: ISBN: ISBN: ISBN: ISBN:

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THE PSYCHOLOGY OF PERCEPTION A Philosophical Examination of Gestalt Theory and Derivative Theories of Perception by D. W. H A M L Y N

‘Cette science en effet n’apprend que la manière de tromper les yeux.5 m alebranche, La Récherche de la Vérité, I, vii, 5.

ROUTLEDGE & KEGAN PAUL LONDON AND HENLEY NEW YORK

: HUMANITIES PRESS

First published in 1957 by Boutledge & Kegan Paul Ltd 39 Store Street London WClE 7DD and Broadway House, Newtown Road Henley-on- Thames Oocon BG9 1EN Reprinted in 1961 and 1969 Beprinted and first published as a paperback in 1979 Printed in Great Britain by Bedwood Burn Limited Trowbridge & Esher © Boutledge & Kegan Paul Ltd 1957 No part of this book may be reproduced in any form without permission from the publisher, except for the quotation of brief passages in criticism IS B N 0 7100 8718 7

CONTENTS EDITORIAL PREFACE

page vii

1 INTRODUCTION

1

2 EXPLANATION IN THE PSYCHOLOGY OF PERCEPTION

11

3

THE HISTORICAL BACKGROUND OF GESTALT PSYCHOLOGY

37

4

GESTALT THEORY

48

5 FURTH ER DEVELOPMENTS

76

6 FUNCTIONALISM

94

7

CONCLUSION

110

BIBLIOGRAPHY

116

IND EX

118

E D IT O R IA L P R E F A C E

S

tu d ie s in p h ilo s o p ic a l p s y c h o lo g y is a new series of philosophical discussions which are to be directed mainly towards the field of psychological and social studies. I t may prove possible for the scope of the series to be extended later. The contributors should not be regarded as representatives of some single philosophical school, but they are all in sym pathy with the most recent developments in philosophy. Each discussion will be of limited length and will be concerned with some topic in which the problems confronting the enquirer are to a significant degree conceptual and not just empirical in character. The first two subjects to be selected for discussion are: The Psychology o f Perception and Mental Acts. Among other topics which are planned for inclusion in the series are Motivation, Dreams, The Unconscious and The Idea o f a Social Science. I t is hoped th a t the enterprise will prove to be of interest both to philosophers on the one hand and to certain specialist investigators on the other; and the monographs are being w ritten with this dual audience in mind. R. F. HOLLAND A pril 1956 v ii

CHAPTER

ONE

IN T R O D U C T IO N

T

H E laym an often receives the claim of the psychologist to be concerned with the subject of perception with surprise, if not with scepticism. This is partly, no doubt, due to the fact th a t he has in his mind certain stereotyped ideas about w hat the psychologist is and is not; there is a popular confusion, for example, between the psychologist and the psychotherapist. I suspect, however, th a t there are other grounds for the popular scepticism with regard to the psychologist and the subject of perception. Is not the psychologist concerned with the ways in which the mind works? And surely perception cannot be one of the ways in which the mind works? I t is sometimes suggested th a t the investigation of the problems of perception is the province of the physiologist who is concerned with the workings of our sense-organs and their stim ulation by stimuli from without. For the basic conditions under which perception takes place are th a t there should be sense-organs and th a t they should be stimulated. Philosophers down the ages, too, have been concerned with perception. Their theories have not appeared to be like those of the physiologist (although Descartes and Locke, for example, felt it 1

2

THE PSYCHOLOGY OF PERCEPTION

necessary to mention w hat they called ‘animal spirits’ and the working of the nerves). In general philosophers have asked what we perceive; whether we are justified in saying th a t we perceive things or something else instead, such as sensations or sense-data, which are the means of our getting to know about things. Sometimes the physiologist’s story has been regarded as relevant here; it has for instance been claimed th a t because, ultimately, all perception occurs when our sense-organs are stimulated, we cannot really be said to perceive the objects which are the source of the stimulation, but only the sensations which are caused by this stim ulation. Clearly it is the task of the philosopher to sort out and evaluate such conclusions as this. B ut where is there room here for the psychologist? I t m ust be adm itted th a t it was once the case th a t there was little to distinguish the philosopher from the psychologist. Before the middle of the nineteenth centu ry the main psychological investigations were carried out by philosophers, and there was an inevitable confusion of problems and techniques. When physiology began to emerge as a full-grown science, there was another intermingling of problems and techniques, and, strangely enough, as I shall indicate in brief later, the findings of physiology were originally thought to confirm the theories of the philosopher-psychologists. As a rule the philosophers maintained th a t it is our sensations th a t we perceive and th a t all these sensations are distinct and separate; the physiologists thought th a t their findings corroborated this theory. A t the end of the nineteenth century there were reactions against these views, and it was out of these reactions th a t the modern psychology of perception

INTRODUCTION

8

was born. The psychological theories of perception of today all have their roots, in one way or another, in Gestalt Theory. This is generally recognized. I t has not been so often recognized th a t Gestalt Theory had its roots in its own past. There has in fact been a conservatism of approach to the subject and there has been little attem pt to consider w hat questions the psychologist ought to ask with regard to perception. The questions have been taken as self-evident, the answers as needing investigation. When the questions have themselves been made the subject of question the traditional (i.e. the nineteenth-century) viewpoint has been adopted. A t the present tim e psychology is in the paradoxical position of taking up a genuinely independent attitude towards the subject of perception, without it yet being clear what questions are being asked or ought to be asked. There is necessarily a cleavage between techniques and individual investigations and findings on the one hand, and general theoretical pronouncements on the other. Some questions which psychologists ask are purely factual. W hat colours can various animals see? Does the brightness or dimness of the illumination make any difference to w hat colours we can see, and what difference? W hat other factors affect what colours we can see? And so on. Some of these questions can be answered as a result of common-or-garden observation, others need more involved or experimental techniques. Sometimes theories are constructed to explain the findings, and in the cases corresponding to the questions noted above the theories are generally physiological in character. Thus the various theories of colour-vision which have been propounded have gene-

4

THE PSYCHOLOGY OF PERCEPTION

rally been physiological theories about the mechanisms through which we receive our impressions of colour. F or this reason colour-vision and the like haye sometimes been thought of as the province of the physiologist. Yet reflection might lead one to think th a t there are further complexities here. Is perception merely a m atter of having the requisite sensory equipment? Surely there are numbers of things which we do not perceive, not because we have not the requisite senseorgans, b u t because we are not paying attention, or for some similar reason. (The Gestalt Psychologists have pointed out th a t we do not generally perceive as such th e gaps between things.) If a psychologist wants to find out whether an animal can perceive red things, he will have to make the animal perform some task which it is in general capable of performing, bu t which on this occasion depends upon its perceiving a red thing as being red. To put this in other words, the animal is required to recognize a red thing, to distinguish it from things of different colours, or, to use the psychologist’s jargon, to discriminate it. B ut to recognize something as w hat it is, to distinguish it from other things, may require practice; it is something which animals and hum an beings may have to learn to do. I t is only after considerable experience th a t a child can recognize its parents and distinguish them from other people. I t may seem th a t redness is a simple property, th a t recognition of it should be immediate; but it is impossible for something to possess the property of redness alone, and a thing which is different from others near it in respect of redness may be different from them in other respects also. Thus the physiological theories of colour-vision, which concern themselves with the

INTRODUCTION

5

characteristics of our eyes as sense-organs, cannot be sufficient to explain how an animal or person can recognize things of a particular colour or distinguish them from others. The philosopher does not seem to be concerned here. He is not concerned with how we can recognize things as possessing one characteristic as distinct from another, bu t with the grounds which we have for saying th a t they have characteristics a t all, and with the question of whether we really know th a t they do. (I do not intend to say anything here about these epistemological questions, or how they are to be answered. I merely w ant to indicate the fact th a t they differ from the other kinds of question under consideration.) There seems, therefore, to be a genuine class of questions which are neither the province of the physiologist nor th a t of the philosopher. W hy not, then, of the psychologist? To say th a t these questions are the province of the psychologist is to say nothing as to how they are to be answered; it is merely to delimit the field. Nevertheless, the fact th a t the questions with which the psychologist might be expected to deal are questions concerned with recognition, discrimination and the like may serve to show th a t the psychology of perception is not so far from the popular conception of psychology after all. Might not an account of our recognition and distinguishing of things be described as an account of some of the ways in which our minds work? Moreover, the explanations which may be given of our recognition of things or of our distinguishing them from others are likely to be different from those appropriate to eolour-vision simpliciter. They are not, th a t is, likely to be physiological in character.

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THE PSYCHOLOGY OF PERCEPTION

W hat I have said so far may serve to indicate th a t the term ‘perception’ may not denote a single concept, b u t rather a family of concepts, which, whilst related, need to be distinguished from each other. In other words, the term ‘perception’ may signify, not just one thing, but a number of different, albeit related, things. I t is im portant to point this out because psychologists sometimes indulge in a conceptual inquiry (an inquiry, th a t is, into w hat sort of thing perception is, or what the term ‘perception’ signifies), whilst giving the im pression th a t they are doing something of a different kind. Thus we may be told th a t perception is an interaction between the organism and the environment, or th a t it is an achievement. And it is sometimes claimed th a t psychological discoveries, even empirical discoveries, are relevant to such characterizations. W hatever is the merit, however, of saying th a t perception is, for example, an interaction between the organism and the environment, it is clear th a t to say this is to say something about a concept, for it is to give an elucidation of what we mean when we say th a t someone perceives something. To this the empirical findings of psychology are relevant only in the most indirect way. T hat is to say th a t as a result of a factual investigation a person may incidentally come to understand something about w hat is m eant by ‘perception’, but only in the ways in which he would come to do so, and perhaps more quickly, by a direct conceptual investigation, a direct inquiry into w hat we mean when we say th a t we or other people perceive something. On the other hand it is sometimes said th a t empirical findings are absolutely irrelevant to conceptual questions, and this would be grossly misleading if it were taken to mean

INTRODUCTION

7

th a t no conceptual statem ent made by an experimental psychologist is worth listening to. Indeed the refusal of the facts to fit in with their theories sometimes forces upon people the realization th a t their understanding of the concepts involved has been at fault. Thus a conceptual discovery may result incidentally from an empirical inquiry. I t remains true th a t a statem ent of the form ‘Perception is------’ is a conceptual statement, no m atter who makes it. Everyone knows what it is to perceive something, in the sense th a t he has first-hand experience of it. Not everyone knows how to give an account of it. In saying ‘Perception is------’ the psychologist does not mean to tell us what we know already; he means to tell us something which perhaps we did not know. Knowledge of the facts would be required by a man who really did not know what it was like to perceive something. This ignorance is not merely an ignorance of what exactly anyone is saying when he says, ‘Yesterday I saw Mr. Smith’, but an ignorance which arises from a lack of acquaintance with the phenomena. If there were such a man, a man who was imperceptive in the strictest sense, the question ‘W hat is perception?’ would be to him like the question ‘W hat is a pterodactyl?’ to many of us; only more so, in th a t we can a t least find out what a pterodactyl is like by means of pictures or descriptions, even if it is not possible for us to meet one, whilst our hypothetical man cannot even do this. To us, however, the question ‘W hat is perception?’ cannot have such a point. We all have experience of perception, but we may not know how to describe it or give an account of it; we may not have a full understanding of the concept of

8

THE PSYCHOLOGY OF PERCEPTION

‘perception9. I t is here th a t the philosopher has his say. I t follows, then, th a t the dieta of psychologists which are of the form ‘Perception is------’ are not necessarily to be received with the respect which is always due to the facts; for no facts are here a t stake. We have noted already th a t when questions are asked about the facts they are not always of the same kind. Sometimes the psychologist may ask, for example, w hat colours an animal can see (i.e. distinguish from each other) in general. Sometimes he may ask, given th a t the animal can see a certain number of colours, under w hat conditions it will see any particular colour. Even in the latter case a number of general conditions may have to be stated in order to specify the case. In addition to saying ‘given th a t the animal can see a certain number of colours’ it may be necessary to add ‘and given th a t it is paying attention, is not asleep, is sufficiently interested in colours as opposed to other qualities’ and so on. Reference to attention, the state of mind of the animal, its motivation and the like, is reference to general conditions which m ust hold if any psychological function is to go on. W hilst it is worth while referring to such general conditions on occasion, in case they should be forgotten, it is also worth while remembering th a t they are general. Nothing particular is pointed out by such reference to general conditions, and this fact limits the explanatory force of such reference. I t is a truism to say th a t a m an will not do something unless, in some sense, he wants to, although it is far from a truism to say th a t he will do some particular thing only when he wants something very badly. Again, the statem ent th a t a man will

INTRODUCTION

9

distinguish something from other things only when he is paying attention can likewise be construed as a truism; it is not a truism to say th a t he will do so only when he is paying attention to a certain degree. The concepts of attention and perception are closely connected, so th a t to indicate such a connection is to make a t the most the minimum of a factual discovery, and indeed the discovery m ay be conceptual and not factual a t all. The latter will be the case if we are not prepared to allow anyone to say of anyone else th a t he perceived something unless he was paying attention to it. Experim ents have been carried out in which some emotionally-charged word is exposed to a subject for a very short tim e in a tachistoscope, and it sometimes happens th a t the subject is unable to report seeing anything, although other tests (e.g. by means of the psychogalvanic reflex) may indicate th a t he has been emotionally roused. I t has sometimes been suggested th a t we should call this ‘unconscious’ or ‘subliminal’ perception. The reverse may be true in other cases; a subject may be able to recall something of which he was unaware a t the time, something to which he was not paying attention. I t might be said here th a t perception can occur without any attention being paid to the object. In the first case, th a t the subject might be said to have paid some attention to the word might be inferred from the fact th at he was emotionally aroused, in spite of his not being able to report having perceived the word. In the second case, th a t the subject might be said to have perceived the object might be inferred from the fact th at he remembered it, in spite of his not, as it seems, having paid attention to it a t the time. In each case there is an ostensible conflict

10

THE PSYCHOLOGY OF PERCEPTION

between the conditions which are applicable. As I have said, in the first case it has been suggested th a t we should talk of ‘unconscious’ or ‘subliminal’ perception, and to do so is to decide th a t attention is the governing factor. In the second case we might be inclined to say th a t the subject m ust really have paid some attention to the object, just because we also wish to say th a t he m ust have seen it if he now remembers it. In either case a decision is being made, a decision to m aintain the connection between the concepts of ‘perception’ and ‘attention’, although in the first case a qualification is made by the addition of such words as ‘unconscious’ to ‘perception’. I t is im portant to note, however, th a t the facts force us to make a conceptual decision; they do not reveal a factual connection or the lack of it between perception and attention. Yet, when we approach the facts with relatively fixed concepts, it may be th a t our view of the facts will require alteration. Thus in the second of the cases described above our decision to m aintain the conceptual connection between perception and atten tion forces us to say th a t the subject m ust have paid attention, in spite of there being no evidence of this. I t is always possible for the general conditions under which perception takes place to be written into our conceptual framework; perception generally occurs, for example, only when we are paying attention, and we may be prepared to say th a t this m ust necessarily be so. I t is ju st this sort of development and application of a conceptual framework th a t tends to be involved in the construction of a theory. Yet, as I shall go on to show, the notion th a t a scientific theory of perception can be constructed involves serious difficulties.

CHAPTER

TWO

E X PL A N A T IO N IN T H E PSY CH O LO G Y OF P E R C E P T IO N

I

N the first chapter I referred to the general conditions which m ay have to be noted in relation to perception. As opposed to these general conditions there may be particular conditions of our perceiving things in a particular way. B ut here difficulties begin to arise by reason of the fact th a t the ways in which we may perceive something can be divided into two classes—the right ways and the wrong ways. Indeed, one way of perceiving something—the right way— m ay be distinguished from all others. I t is clear th a t we can, in principle, always say something about the ways in which we m ay perceive things wrongly, for this is just to say something about the conditions under

F ig

u r e

11

1

12

THE PSYCHOLOGY OF PERCEPTION

which illusions come into being. For example, in the light of the Muller-Lyer illusion (Figure 1) we can say th a t two lines of equal length look of different length (or, in other words, we see them as of different length) when, for example, they are furnished with arrowheads, as in the diagram. T hat is to say th a t we can state what precise factors may make them look different from their normal or correct length (I shall refer to such a case as Case (a)). On the other hand, if (Case (b)) we are asked under w hat conditions lines of equal length look of equal length, the only possible answer m ust be ‘Under any conditions except those which tend to make them look different5, and this is only another way, a negative way, of saying ‘Under normal conditions’. Indeed, to talk of lines of equal length looking of equal length a t all is odd, for we usually use such words as ‘looks’, ‘appears’ and ‘seems’ in order to make a contrast with what is actually the case. Here no such contrast is being made. This helps to explain why the answer to our question is either ‘Under normal conditions’ or ‘Under any conditions except those which tend to make them look different’. Such answers tell us little, but this is appropriate where the question also can be viewed as logically improper. The answers serve to point out th a t we are concerned with the normal case, not the abnormal, so th a t talle of how the lines look is out of place. Rather we should be concerned with what they are actually like. Thus the question which is appropriate to the abnormal case is no longer appropriate to the normal. However there is a third possibility (Case (c)). We expect the lines in Figure 1 to look different in length, but it may be th a t to some people they do not. Our

EXPLANATION IN PSYCHOLOGY OF PERCEPTION 18

expectations are here not derived from w hat we know to be the actual state of affairs, the actual length of the lines, bu t from the fact th a t we know of the aetiology of the illusion and its generality. To say th a t to these people the lines look of equal length is not to imply a contrast with the actual length of the lines (for they are of equal length), but with the ways in which they are generally expected to look in these circumstances. As the illusion is generally expected and these people do not fulfil our expectations a contrast is implied here. Such cases are rarer than those of type (a), or a t any rate the impulse to deal with them is more academic; we are not generally so interested in our failure to be taken in as our actually being taken in. Of more interest perhaps is the sort of answer th a t might be given in such cases to the question ‘Under w hat conditions do the lines look of equal length?’. In this case neither of the previous two answers is possible. We can neither say what makes them look of equal length (for nothing makes them look of equal length; they just are so), nor say th a t they look of equal length under normal conditions (for ex hypothesi the conditions are not normal). If we can say anything it must be to the effect th a t the person who is not taken in is, or has become, sophisticated; he manages, perhaps as a result of learning, to compensate for the factors which produce the illusion. These conditions are clearly very different from those which were given in the other cases. Y et how we are to characterize such conditions is not so clear. In consequence it is im portant th a t the differences between them and those applicable in Case (a) should be stressed. In case (a) we account for the illusion, the fact th a t

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THE PSYCHOLOGY OF PERCEPTION

we tend to see the lines as of different length although they are in fact of the same length, by pointing to other features of thê situation. I t is the total context th a t is relevant, not just the lines themselves, and we may account for the illusion by reference to this to tal context. Of course, by very reason of the fact th a t some people may fail to be taken in, th a t they m ay see the lines as of equal length regardless of the circumstances, we have to rule out sophistication in our account of the phenomena. We may have to say th a t a t any rate the naïve subject, the person who sees the lines for the first time, is liable to be subject to the illusion, and in his case the illusion is due to the total context. (The fact th at for some illusions sophistication may be necessary is irrelevant here. This means only th a t the natural expectations are reversed. Whereas in case (a) the illusion is expected, in such cases it is not, so th a t if the illusion occurs the pattern of explanation will be th a t appropriate to case (c) and not to case (a).) Thus we have to be governed in our expectations by w hat is natural, although it should always be remembered th at naturalness is always relative, as must also be sophistication. Psychologists, especially the Gestalt Psychologists, have often laid emphasis upon the naivety of the subject in experiments on perception, but it is clear th a t naivety is relative. As I shall indicate in the next chapter, the philosophical movement which has been given the title of ‘Phenomenology’ has encouraged the belief th a t absolute naivety can be obtained, pure experience without any sophistication; but this is metaphysics, not empirical fact. As long, however, as we are prepared to rule out some degree of sophistication, type (a) cases are to be

EXPLANATION IN PSYCHOLOGY OF PERCEPTION 15

accounted for by some reference to the circumstances of the situation—in the case under consideration, the additional lines which have been drawn. I t is in such circumstances th a t the illusion arises. In case (c), however, no such account is possible. We cannot refer to the circumstances which are peculiar to the situation, for it is despite these th a t the lines are still seen as of equal length. There is nothing about the lines with the arrow-heads which makes them look of equal length. Y et the situation is not a normal one; it is not one in which we should generally expect the lines to look of equal length. So we are forced to look for the appropriate conditions in something about the perceiver, not in w hat is perceived. The answer to the question, ‘Under what conditions will a person see lines of equal length as of equal length, despite circumstances which normally make them look of different length?’ m ust be something like, ‘When he is able, or has come to be able, to allow for these latter circumstances’. This answer is reminiscent of, but not the same as, the answer appropriate to case (b). For there the answer was, ‘Under all conditions except those which tend to make the lines look of different length’, and the analogous answer here is, ‘Under those conditions under which he is able to allow for circumstances which tend to make the lines look of different length’. In case (b) the factors applicable to case (a) were referred to as exceptions; in case (c) they are referred to as m atters to be allowed for. Thus a general answer to the question, ‘Under what conditions do lines of equal length look of equal length?’ m ust be a combination of those appropriate to cases (b) and (c), i.e. ‘Under all conditions except those which tend to

16

THE PSYCHOLOGY OF PERCEPTION

produce the illusion (in the more general sense th a t the conditions which tend to produce the illusion depend upon the subject’s degree of sophistication)’. My discussion so far might be said to be concerned with the laws of perception, in the sense th a t the issue has been the conditions which generally hold for a thing to be seen in a certain way. I t is clear th a t there may be laws, or a t any rate generalizations, applicable to the generation of illusions. About the conditions under which we are not subject to illusions, however, not much is to be said other than th a t some sophistication is possessed by the person concerned (although in connection with particular cases something may be said about the techniques involved in acquiring sophistication). B ut what could be said in a general way about correct perceivings? As I have attem pted to make clear, we can say th a t people see things correctly under normal conditions, but what conditions are normal can be determined only negatively by contrast with the abnormal conditions which produce illusions. This means th a t there is a definite limitation to the application of the phrase ‘law of perception’. Indeed it might be said th a t a better phrase would be ‘law of illusory perception’, a conclusion borne out by the quotation from Malebranche with which I have headed this work. This conclusion is obviously im portant for explanation within the field of perception. Explanations in science can be divided into two kinds, explanations made by reference to laws, and explanations made by reference to theories. We explain why a particular phenomenon deviates from our expectations (which may themselves be dictated by some

EXPLANATION IN PSYCHOLOGY OF PERCEPTION 17

law) by showing th a t it falls under some other law which accounts for the deviation. This is the typical pattern of w hat is sometimes known as ‘causal explanation’. We give the cause of the deviation from expectations by reference to the law, so th a t we can make a statem ent of the form ‘The phenomena differ from what was expected because------ ’. Theories on the other hand are invoked to account for laws, and in doing so generally provide a model of some sort into which the laws may be incorporated. The theory serves to show th at the laws are not ad hoc, arbitrary, or unexpected from a larger point of view. I t is therefore necessary to say something about both of these kinds of explanation in connection with perception. (1) T hat we may ask for, and are capable in principle of giving, explanations of our being subject to illusions is obvious. Our social life necessitates th a t there are standards of correctness in connection with our behaviour, and this includes the way in which we see things and the ways in which we describe w hat we see. If we know w hat something really is, if we know its correct description or identification, we expect others to know it also. Moreover, there are recognized ways of ascertaining w hat is the correct description or identification of a thing. This, iii the case of lines of equal length, is determined, not by the way in which they look in general, bu t by measurement; it is the latter which provides the standard of what we mean by saying th a t two lines are of equal length, so th a t the operation of measurement is the court of decision over questions of length. I t is in this sense th a t we can know definitely th at two lines are of equal length, in th a t we have a procedure for determining this. The case in question is,

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of course, a very straightforward one. In the case of colours, for example, standards are much less fixed; the number of factors which may have to be taken into account in determining an object’s colour may be large—illumination, saturation of colour, texture and so on. Nevertheless there are standards of correctness here too. We can say definitely if an object is red. Thus, if we know the correct description of an object, we can ask also why it does not on some particular occasion appear so to us or to anyone else (if it does not appear so), why we see it as possessing different characteristics from those which it really has. In the case of the Muller-Lyer illusion we can ask why one line looks longer than the other. The path of explanation is clear. I t would be enough as a first step to say th a t the lines look of different length because they are set in a context such th a t one is enclosed and the other given continuity outside it by lines attached to them. I t is not my concern whether this is a good explanation; it is sufficient if it reveals the type of explanation th a t is required. Of course, this is only a first step, and it may be th a t some theoretical justification will be required of this in turn. If this is so, it should be noted w hat it is th a t is being asked. Explanation is being required of the fact th a t in certain circumstances we generally fail to identify a thing or its properties correctly. I t is possible th a t such an explanation might be given by claiming th a t the law or generalization th a t lines look of different length when set in the context specified above is an instance of some more general law. A law which states th a t we see things in such a way th a t they are a function of the total pattern or context is clearly

EXPLANATION IN PSYCHOLOGY OF PERCEPTION 19

more general than th a t involved in the account of the Muller-Lyer illusion. W hilst a more general law might be proffered as explaining th a t under consideration, it is not clear th a t any systematic theory could be provided as well—certainly not one which could furnish a model for the phenomena. The final account of the Gestalt Psychologists did involve a model—one in which perceptual phenomena are explained in terms of certain hypothetical brain-processes, which are in turn explained in terms of electrical fields. This suggestion, however, is based on the assumption th a t the way in which we see things is always determined by w hat goes on in our brain, and whilst this may sometimes be true (brain-lesions sometimes produce disturbances of perception), it cannot be generally true in the required sense. For, as we have seen, some illusions are to be explained in terms which do not fit into this point of view, e.g. they demand reference to sophistication or the lack of it, or learning or the lack of it. Indeed such ‘laws’ as the one which relates the appearance of things to their total context cannot be more than generalizations of restricted generality. For, the very fact th a t to some people the Muller-Lyer illusion does not appear or need not do so, granted a certain sophistication, provides exceptions. Illusions and perceptual errors in general seem to be labile phenomena, depending as they do on the degree of sophistication of the subject. In some cases it is very difficult to avoid being taken in, in other cases it is easy. If generalizations are all th a t can be produced about such phenomena, there is no place for theories either. An attem pt might be made to save the day by saying th a t a t any rate unsophisticated subjects are

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always subject to the illusion. Difficulties immediately arise, however, as to how we are to assess sophistication and the lack of it. The notion of sophistication involves the notion of coming up to a mark, of the attainm ent of a standard. When we describe a man as Sophisticated’ we are assessing him. Such notions are foreign to ordinary scientific theories. Illusions are labile just because we do not all attain the same degree of sophistication with regard to how we see things. The difficulties involved in the construction of a theory in this field stem from th a t very notion of ‘sophistication’ and not merely from the lability of the phenomena. (2) W hat of explanations with regard to case (b), i.e. with regard to veridical perception? There is no suggestion in this case th a t the lines might be expected to be seen as otherwise than of equal length. There is no question of a deviation from expectation, and if, nevertheless, some question were still asked beginning ‘Why------’, it m ust be a different sort of question from normal requests for explanation. For, explanation is normally called for when there is something unusual about the phenomena, something not expected. W hat, then, could be asked in saying ‘W hy do the lines look of equal length?’ and what sort of answer could be given? I t may be th a t an answer to the second question will shed light on the first. I think th a t if we were asked in this context why the lines look of equal length, we should be tem pted to reply, ‘Because they just are of equal length’. One of the things which we expect of lines of equal length is th a t in normal circumstances they should look so. B ut why should we expect this? The answer can only be, ‘Because this is part of what

EXPLANATION IN PSYCHOLOGY OF PERCEPTION 21

we mean by saying th a t they are of equal length’. Once again we are back to questions of definition and not of fact. W hy do red things appear red under normal conditions? Because to say th a t a thing is red is to say, amongst other things, th a t it will appear red under normal conditions. W hat constitute normal conditions will vary from case to case, and a general account may be given only by saying th a t by ‘normal conditions’ is m eant any conditions except those which make a thing appear other than as it really is. This is the same account of normal conditions as I gave earlier. The fact th a t something appears red under normal conditions is grounds for saying th a t it is red. Indeed we expect red things to look red under a variety of conditions; we learn the use of the word ‘red’ not in just one context, b u t in a variety of contexts and circumstances. T hat something looks red under some complicated lighting arrangement is still grounds for saying th a t it is red, if not such good grounds as it would be if the lighting were neutral. Thus, in any one of a variety of circumstances, if we are asked why something which is red looks red, it is appropriate to answer, ‘Because it is red’, just because its looking red in this circumstance is one of the grounds for saying th a t it is red. To p ut the m atter in another way, in a way in which W ittgenstein once p ut it—if we are asked, say, what makes a white thing look red in red illumination, the answer is obvious; b u t if we are asked what makes a red thing look red in normal illumination, it would be appropriate to answer, ‘Nothing makes it look red. I t is red.’ Under normal conditions, i.e. the conditions in the light of which we establish w hat it means to say

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th a t something is whatever it is, it makes no sense to ask w hat makes it whatever it is. Again, an answer to the question why the lines of equal length look of equal length under normal conditions could be, ‘They have to, or they would not be of equal length.’ By this we mean th a t unless they looked of equal length we should not allow them to be described (and described correctly) as of equal length. Any attem pt to push the m atter further would be to become involved in m etaphysics of the classical sort, and indeed this whole discussion might be labelled ‘metaphysical5 or ‘epistemologicaP, inasmuch as it is concerned with grounds, definitions and the like. I t should be clear th a t this case provides no room for scientific explanation, since none is called for. To recognize the case for w hat it is, however, is im portant, because it is quite possible for a psychologist not to distinguish it from the others and to run them together in consequence. This, as I shall try to make clear later, was done by Koffka and the Gestalt Psychologists, and the mistake has been perpetuated by others. I t was suggested th a t the reason why we see things correctly in normal circumstances is th a t our seeing them is a result of the direct stim ulation of our sense-organs by the external stimuli. Furthermore, it was suggested th a t the only difference between this case and the cases of illusory perception is th a t in the latter the stim ulation is such as to allow autonomous brain-processes to produce an impression which does not correspond to the things as they actually are. For whilst there is often a correspondence between the pattern of stimulation and the perception, there is not a constant correspondence (what the Gestaltists called the ‘constancy

EXPLANATION IN PSYCHOLOGY OF PERCEPTION 23

hypothesis’ is just the hypothesis of this constant correspondence, and this they were anxious to deny). B ut in fact, to say th a t we see lines of equal length as of equal length under normal conditions amounts to a tautology (that lines are of equal length entails th a t we should see them so under normal conditions). If th a t is so, it cannot be interpreted as a fact requiring a genuine explanation. Perceiving is in any case not a m atter merely of receiving sensations which are produced directly by stimulation of our sense-organs, although, of course, having our sense-organs stim ulated is a necessary condition of our perceiving something. I t is not, however, a sufficient condition. This is evident enough from the fact th at sometimes a certain degree of sophistication is required in order for it to be possible for us to see things in a particular way, as was indicated earlier. Indeed it may well be the case th a t all the ways in which we see things are a product of learning and interpretation. Seeing lines as of equal length involves having come to be able to apply the concepts of ‘equal’ and ‘length’. For this reason to say th a t under normal conditions we see lines of equal length as of equal length because they are of equal length constitutes a logical truth, and it has nothing to do with any physiological facts about the stimulation of our sense-organs. The confusion has a long and respected history, dating at least from Locke and the British Empiricists, b u t it is*a confusion none the less. (3) W ith the third case (c) we return to an occasion for genuine explanation. In this case we are confronted w ith instances in which, in the light of generalizations relevant to case (a), we expect people to be subject to illusion. In the case of the Muller-Lyer illusion, we

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expect people to see the lines as of different length, but if anyone sees them as of the same length nevertheless, we may ask for an explanation of this. I noted earlier th a t any generalizations which may be applicable in this case will be generalizations to the effect th at people with a certain degree of sophistication can compensate for the misleading features of the situation. They possess the necessary technique for this purpose. Thus it is clear th a t an explanation of any individual’s failure to be taken in m ust be in terms of a generalization of this sort. B ut as with case (a), difficulties arise over the further type of explanation which is generally provided by theories; indeed the difficulties are here greater than before. Once again we can attain increased generality, even to the point of asserting what is all but a tau to logy (to say th a t failure to be taken in is a function of sophistication could easily be made tautological). As before, however, there seems no possibility of producing a theoretical model for any system of laws, such as might be found elsewhere in science. The reason for this is, I think, th a t we are throughout these cases continually concerned with success and failure, correctness and incorrectness, naivety and sophistication, pairs of opposing concepts which are applicable to human (and indeed animal) behaviour in so far as standards are imposed upon it. As I have said earlier, the existence of such standards and the reference to them is due to our social life. I t is only where comparisons are possible between the behaviour of different people, so th a t marks or gradings can be attached to them, th a t questions of success and failure begin to arise. I t is of no use to look for models of such situations elsewhere. I t

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may be th a t human behaviour is in part a product of the working of a nervous system for which models exist elsewhere—in communication engineering, for example. Such a model, however, does not seem applicable a t all in the present context, and the reason is th a t to call behaviour ‘successful5 or the reverse, to call a man ‘sophisticated’ or ‘naïve’, to say th a t what he does is correct or incorrect, is not merely to describe his behaviour or pattern of behaviour; it is to assign marks to it also, to appraise or evaluate it in terms of certain standards. Thus 111 so far as the psychology of perception is involved in the application of standards, it has peculiarities of its own. (It is likely th a t this is true of other branches of psychology also, but I cannot discuss this here.) I say ‘in so far as the psychology of perception is involved in the application of standards’ and not ‘because it is’ not only because it would be a mistake to attem pt to lay down in advance w hat is or is not to be called ‘psychology’, b u t also because there is yet a further alternative which is in some ways unlike those which I have considered so far. I began this discussion by saying th a t the ways in which we might see something can be divided into two classes, one consisting of the correct way of seeing it, the other consisting of all the incorrect ways. There may, however, be no one correct way of seeing an object. Most of the things or pictures which we see have a unique identification, but this is not universally so. In some cases it is possible th a t we m ay be offered two alternative descriptions from particular points of view and there may be no way of deciding between the two. Certain manufactured articles have two or more uses, and it would be

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no more correct to say th a t any one is the use than it is to say it of any other. The particular point of view which determines the appropriate kind of description is in this case the consideration of the use of the article. In the case of pictures, it may be a consideration of their representation which determines w hat description we are to apply, and in the case of m any pictures to say what they represent is the natural way of describing them. We could, of course, give an account of the structure of the drawn lines, colour patches and so on, b u t we should be less inclined to call this a ‘description of the picture5. In this sense, as W ittgenstein points out in the Philosophical Investigations (pages 194 ff.), some pictures have only one description. B ut others again are ambiguous. Psychologists have, in fact, made something of a speciality of such ambiguous figures, and Kohler has made a special investigation of the ways in which we pass from the seeing of one aspect of a figure to the seeing of the other, the intervals between changes over a period of time, and so on (see his Dynamics in Psychology). Clearly generalizations might be produced as to the rate of such changes and their dependence upon other factors. Sometimes it happens th a t after a while it is very difficult to see the figure in any way except one particular way. (It is to be noticed th a t if, for some reason we see something wrongly and then come to see it rightly, it is often very difficult to see it wrongly again.) If, however, we are asked under w hat conditions we see the ambiguous figure in one or other of the ways, it may proYe very difficult to give an answer. The very fact th a t the figure is ambiguous makes it impossible to say th a t anything makes us see it in one way or the

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other; for to see it in one way we have to ignore features which would enable us to see it in the other way. In consequence, we could not be made to see the figure in one way unless we were prepared to ignore features which would enable us to see it in the other way. Moreover, it is sometimes possible to acquire a technique for ensuring the change of aspect more or less a t will. We can direct our attention to some feature which enables us to see it in one or other of the ways. If this is true, then a t any rate this sort of explanation, i.e. one which involves the notion of ‘attention’, is possible with regard to the fact th a t a t any one moment we may see the figure in one way rather than the other. W hat stands out about such cases is th a t interpretation is required. We cannot see the figure in both ways at the same time, and this ‘cannot’ is a logical ‘cannot’, not an empirical one. I t is not the case th a t it is a m atter of fact th a t we do not see the figure in both ways a t the same time, although we might do so. For if we gave a sense to the notion of seeing an ambiguous figure in both ways a t the same time, it would involve a different sense of ‘seeing’ from th a t involved in saying th a t we see it in one or other of the ways alternatively. This is because what we mean by calling such figures ‘ambiguous’ is th a t each description excludes the other; they are not compatible. In consequence, if we were to say th a t we saw the figure in both ways a t the same time we could mean only th a t we knew th a t it could be interpreted in either way; perhaps in such cases we should be seeing the figure in neither way a t the time, but only as a figure. In other words, to say th a t we see the figure in both ways simultaneously cannot mean the same as saying th a t we are inter-

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preting it in both ways simultaneously, b u t rather th a t wTe know th a t it is capable of being interpreted in either way alternatively. I t follows from the fact th a t interpretation is required a t some stage th a t no physiological story is directly relevant, or, to put the m atter in the way th a t I have pu t the other cases, no theory can be produced to account for the phenomena which involves a model of this sort. Despite first appearances, this is for the same reasons as were applicable in the previous cases. Whereas there is no one correct way of seeing the figure in the present case, and therefore no one correct description, each alternative way in which we do see it is correct and might be opposed to ways which are incorrect. The fact th at there is more than one correct way of seeing the figure does not alter the pattern of explanation, except when we contrast one correct way with another. In this latter case we may have to appeal, for example, to attention. B ut the pattern of explanation is still dependent upon a prior account of a kind already discussed, in th a t each way of seeing the figure is correct and each in turn is therefore explicable as in case (c). Although some reference to the details of a ttention m ay be required, therefore, the phenomena are no different fundamentally from those in which there is bu t one correct account of the situation. This case, then, does not after all afford an exception to the general rule. The difference between each of the situations which I have discussed and between the questions which can be asked with regard to them has not generally been recognized by psychologists; and in one work which is of great importance for the psychology of perception

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—Koffka’s Principles o f Gestalt Psychology—it is claimed th a t such distinctions have no psychological relevance. On page 79 of his work Koffka says, ‘This distinction between two kinds of perception, normal and illusory, disappears as a psychological distinction as soon as one becomes thoroughly aware of the fallacy which it implies, much as it may remain as an epistemological distinction. For each thing we have to ask the same question, “Why does it look as it does?” whether it looks “right” or “wrong” .5 The context of this assertion is a criticism of older psychological theories on the grounds th a t whilst they concerned themselves with illusions such as the one with which I have dealt by looking for ‘special conditions which mislead our judgm ent’, normal perception was considered as presenting no problem a t all. Koffka suggests th a t the fundam ental question for the psychology of perception is ‘W hy do things look as they do?’, b u t he insists upon a single, general answer to this question, irrespective of the varying contexts in which the question might be raised. The view th a t this is the fundamental question and one which is to be answered in this way has been pu t forward by others since—for example, by J. J. Gibson in his Perception o f the Visual World. I t is because this question and this way of dealing with it have become so central th a t I call Koffka’s work ‘of fundam ental importance’. If, however, the question ‘W hy does X look such and such?’ demands very different answers in different cases, as I have shown, then there is no general answer to the question ‘Why do things look as they do?’, and the supposai th a t there is rests upon a confusion. Such a confusion is a conceptual confusion in th a t it involves a failure to

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distinguish different applications of the adm ittedly connected concepts of ‘appearing5and ‘perceiving5and concepts of a similar sort. Koffka5s way of dealing with the m atter, after he has insisted th a t the question ‘W hy do things look as they do?’ is the fundam ental question for the psychology of perception, is to examine two main answers which have been given to the question. Current theory, a t the time when Gestalt Theory came into being, was, he says, a combination of these two answers. The first answer is, ‘Things look as they do because they are what they are5, and the second, ‘Things look as they do because the proximal stimuli are w hat they are5. (By ‘proximal stimuli5 is m eant the pattern of excitation on the sense-organ itself.) We shall see th a t w hat is really wrong with these answers is th a t they each ignore some of the cases which we have mentioned, whilst accounting for the others. Koffka5s refutations are rather complicated: (1) The first answer is wrong, in effect, because of the possibility of illusions. Things do not always look as they in fact are (this is, indeed, implicit in our use of the word ‘look5), and this should be enough to refute the answer. Koffka goes on, however, to say th a t even if we allowed th a t illusions were to be accounted for merely by reference to special conditions, this would still leave the problem of why in normal cases things look as they do. (It is in this context th a t the quotation which I gave earlier occurs.) The first answer would suggest, Koffka says, th a t in normal cases there m ust be a simple and direct relationship between w hat things really are and how they look. B ut Koffka suggests th a t this cannot be so because things are not normally in

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direct contact with the organism; we have to allow for the process of stimulation, and this suggests th a t there cannot be any simple and direct relationship between things and how they look to us. In other words, even in the case of normal perception, there are conditions which m ust hold good—general conditions about the stimulation of the sense-organs. I t is clear, however, th at these conditions are not special conditions and so not on the same level as those which might be invoked to account for illusions. Special conditions could be invoked to account for normal perception only when we expected abnormal perception, and such conditions would be of the type discussed earlier. To say th at things look as they do because stimuli from them affect our sense-organs is not very illuminating, just because the account confines itself to general conditions, when special conditions seem to be demanded. B ut no one class of special conditions can be given to account both for illusions and for normal perception, in th at the type of special condition which can be given in each case is different, inasmuch as our expectations are different. Koffka says nothing about expectations, nor does he see th a t there m ust be such if his question is to have any meaning. A request for an account of normal perception m ust be made from quite a different point of view from th a t from which a request for an account of illusions can be made—unless, of course, all th a t is being required is a description of the general conditions under which perception can occur a t all: that, for example, our senseorgans are being stimulated, th at we are paying atten tion, and so on. There are some suggestions th a t this is all th a t Koffka is asking for, as will be evident from his

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consideration of the second answer—b u t only some suggestions. Other indications show th a t what he really wants is far more. The consideration of the first answer has shown th a t a t any rate things do not always look as they do because they are w hat they are. There are illusions, and this is often because the process of stimulation brings in other factors which constitute special conditions— perspective, illumination and so on. The immediate pattern of excitation on the sense-organ does not always, in consequence, correspond to the characteristics of the object of perception. This immediate pattern of excitation Koffka calls the ‘proximal stimuli’, and the suggestion put forward in the second answer is th a t if the way th a t things look is not always a function of their actual characteristics, it may be a function of the proximal stimuli. Things look as they do because the proximal stimuli are w hat they are. I t is to be noted th a t the immediate reasons for introducing this term ‘proximal stimuli’ were th a t some illusions are set up by those very factors—perspective, illumination and the like—which make it necessary to distinguish between the character of the object of perception and the character of the excitation of the senseorgans. In other words the existence of illusions of this kind was what made it necessary to have recourse to the immediate pattern of stimulation on the senseorgan. One would expect, therefore, th a t reference to proximal stimuli should afford explanations of these illusions, bu t not necessarily of normal perception or even of other types of illusion. (2) The second answer, then, copes with illusions of a certain type, just as the first answer coped with normal

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perception. As a general answer, however, it is wrong, because the way things look does not always correspond to w hat m ight be expected on the assumption th a t there is a complete correlation between how we see things and the excitation of our sense-organs. This is because of w hat have become known as the ‘phenomena of constancy’. If the laws of perspective, for example, held good, things at a distance from us should look smaller than similar things which are near to us. B ut they do not, or a t any rate not so much as would be expected on the basis of perspective alone. Analogously a white object under poor illumination still tends to look white whilst a black object in good illumination still tends to look black, although the former may be reflecting less light than the latter. A round plate seen a t an angle still tends to look round and not elliptical, although in fact, and in accordance with geometrical optics, the pattern of stim ulation on the retina is elliptical. Such examples might be m ultiplied. They have been studied extensively by the Gestalt Psychologists and by other psychologists also. Thus it would seem th a t the second answer, too, is wrong. Traditional psychological theory involved a combination of these two answers in th a t it initially invoked what Koffka calls the ‘constancy hypothesis’ (to be distinguished sharply from the constancies mentioned above), and imposed on this, interpretation by the perceiver. The constancy hypothesis is the view th a t sensory experience always corresponds to the stimuli which produce it; traditional psychologists often seemed to make of this a necessary truth, but it is in fact an aspect of a theory arising from a particular

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analysis of perception. In the light of such facts as those mentioned above, however, it is manifest th a t we do not always see things as exactly corresponding to the stim uli which affect our sense-organs, and to explain such deviations the traditional psychologists invoked interpretations which are made in the light of experience. Because we are not always aware of such interpretations, they were held to be unconscious, with the consequence th a t there was a frequent appeal to ‘unconscious judgm ents’. The G estalt Psychologists have rightly criticized such a resort to Ptolem aic epicycles, but they have also made a special point of attacking any view which invokes experience, a procedure which is more dubious, in th a t the view th a t perception involves interpretation or experience in some sense does not stand or fall with the tru th of the constancy hypothesis. We may need experience in order to see something in a certain way w ithout its being necessary to assert th a t such experience is imposed upon something originally given in sensation. Indeed, it is necessary to separate questions about sensations entirely from questions about the ways in which we perceive things. To say of someone th a t he has a sensation does not ordinarily commit one to the view th a t he has perceived anything at all. In sum, traditional psychologists espoused the second answer in so far as they invoked the constancy hypothesis, b u t in invoking experience or interpretation, Koffka claims, they also brought in something of the first answer. In other words, they claimed th a t we see things as we do, first, because the stim ulation of our sense-organs is w hat it is, but also, second, because we learn through experience th a t things are sometimes different in their

EXPLANATION IN PSYCHOLOGY OF PERCEPTION 35

appearance from what would be expected in the light of such stimulation, and so we come to allow for this. In fact it would seem that each answer is appropriate to particular cases, the cases already mentioned, but neither is, nor could be, generally applicable. In passing, however, Koffka makes a rather im porta n t remark. On page 80 of his work he says of the second answer, ‘Now in its broadest interpretation this proposition is certainly true, but the interpretation usually given to it is distinctly limited and therefore false’. I t is this which provokes the question as to whether Koffka is asking only for the general conditions of our perceiving anything a t all; for the broadest interpretation of the second answer would be th a t a general condition of our perceiving anything a t all is th a t our sense-organs are stim ulated. B ut Koffka goes on to say, ‘In the widest interpretation our proposition means no more than this; any change in the proximal stim ulation will, provided it be not too small, produce some change in the look of things, but what kind of change in the behavioural world will follow upon a change in the proximal stim ulation cannot be derived from our proposition; whereas in the narrower interpretation the proposition also contains implicitly a statement about the kind of this change’. So it would seem th a t Koffka requires an answer which gives both the general conditions of perceiving anything a t all, and also a t the same tim e the special conditions of perceiving some particular thing in the way th a t we perceive it. If this is so, it follows from what has been said th a t no one answer can be given. Koffka’s own answer which, he says, is final, is ‘Things look as they do because of the field organization to which the proximal

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stimulus distribution gives rise5. This answer is, on the face of it, as mysterious as it m ust be logically inappropriate. Where no one answer can be given, any one answer th a t is offered m ust be mysterious.

CHAPTER

THREE

T H E H IST O R IC A L BACKGROUND OF G ESTA LT PSYCHOLOGY

G

EST A L T Theory, as is obvious from its polemics, constituted a reaction, and it is, in consequence, necessary to see w hat it was reacting against. I t was, in fact, one of several reactions against the Sensationalist and Associationist theories of the nineteenth century, but these in turn had a further source in the B ritish Empiricists, Locke, Berkeley and Hume. These philosophers tended to present their epistemological theories of perception in psychological dress, w ithout being aware of the need for a distinction between epistemology and psychology. Fundam entally they were concerned with the justification of, and grounds for claims to perceptual knowledge, but their theories involved an apparatus of psychological te rminology of which modern empiricists have done much to rid themselves. Epistemology is concerned with claims to knowledge in general and deals w ith such questions as whether we can be said to have knowledge a t all. I t thus involves inquiry into the concept of ‘knowledge’. Traditionally, however, it has been associated with a metaphysics which entails th a t we 37

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cannot be said to know anything unless something, some piece of knowledge, is ‘given5to us, in such a way th a t we can be free from doubt or possibility of error with regard to it. Empiricists, like Hume, have always sought for the ‘given5 in sensation, whilst R ationalists have looked to reason to provide it. T hat which is ‘given5 is supposed to provide a basis for claims to knowledge in general. Psychology, on the other hand, is not concerned with the justification of such claims to knowledge; in the sphere of perception it can be concerned only w ith the causes or conditions of our perceiving things in certain ways. Of the B ritish Em piricists Hume, perhaps, had the biggest influence, with his doctrine of impressions and ideas. Hum e5s impressions were distinct and separate from each other in the sense th a t they constituted items of knowledge which did not entail each other. Thus my knowledge th a t something is red is quite distinct from m y knowledge th a t it is square. I t was claimed, furtherm ore, th a t my awareness of the redness of an object is something simple and incapable of further analysis. These views together constitute an epistemological atomism, the theory th a t knowledge is built up out of a num ber of distinct and simple building-blocks. B ut Hum e’s use of psychological terminology encouraged the belief in a psychological atomism also—the belief th a t experience is built up out of distinct atomic sensations. This latter view was espoused by the philosopher-psychologists of the nineteenth century, Jam es Mill, J. S. Mill and Alexander Bain, although already a t the end of their lives the doctrine was being modified. The means by which experience was built up out of these atomic sensations

THE HISTORICAL BACKGROUND

39

was th a t of association. Ideas derived from sensation are associated in certain ways. The doctrine of the association of ideas has a long and respectable history, going back at least as far as Aristotle, but until H artley it had been employed mainly to account for illusions and superstitious beliefs. I t was now pressed into service as a general explanation of our beliefs. In sum, the traditional nineteenth-century doctrine, certainly in this country and to a large extent elsewhere, was th a t certain atomic sensations are given; all else is a superstructure built up by association. Curiously enough, the doctrine of atomic sensations was, as it was supposed, given corroboration from physiology. In the 1830s Johannes Muller p u t forward a theory which he derived from another physiologist called Bell, a theory which he called ‘the theory of specific nervous energies5. The view pu t forward was th a t each nerve has its own specific function and cannot take over another function. I t was inferred from this th a t each particular nerve is responsible for one experience. The retina consists of a m ultiplicity of distinct nerve-endings; hence the retina should afford a m ultiplicity of distinct sensations. Thus the visual field became likened to a mosaic. This, of course, is only theory, bu t it is to be noted th a t it involves an argum ent from the properties of the retina to the characteristics of experience, and this argum ent has tended to be accepted even when it flies in the face of experience. There had been similar arguments before, of course, especially in the hey-day of geometrical optics. Berkeley’s view of our perception of the third dimension was essentially of this type. I t is interesting in this respect to compare Berkeley’s

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New Theory o f Vision with Malebranche’s discussion of similar subjects in his Récherche de la Vérité, 1, 7 ft., and in his 12th Dialogue on Metaphysics. B oth writers sta rt from the position th a t we are given sensations such as m ight be expected on the basis of geometrical optics and our knowledge of the retina of the eye as a two-dimensional surface. When, however, they come to the ways in which our actual perceptions differ from this, there are im portant differences between them. Berkeley tends to explain the deviations from expectation by reference to further sensations ‘suggested’ by experience. Malebranche, on the other hand, whilst sometimes referring to sensations, tends to say th a t the deviations are due to judgm ents which we make. However, as these judgm ents are not always or not generally consciously made, he refers to all visual sensations as kinds of ‘natural judgm ents’ or judgm ents of sense’, as opposed to ‘free judgm ents’. In the general workings-out of their theories there is perhaps no great difference between these writers (although on some particular points, e.g. in their tre a tm ent of the zenith-horizon illusion of the moon, there are im portant differences). W hat is noticeable, however, is the tendency of Malebranche to have recourse to judgments, whilst Berkeley, in common with the other B ritish Empiricists, clings to sensations. This is especially notable because one of the reactions against nineteenth-century sensationalism was th a t of the R ationalist Bradley, who espoused the cause of the judgm ent against the sensation and the idea. In general, however, the reaction took the form of showing th a t the sensationalist doctrine flew in the face of experience; our visual field, for example, is not

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like a mosaic of punctiform sensations. Jam es, Bergson, W ard and Stout all saw this, b u t the first two a t least clung to the old doctrine of ideas whilst a t the same tim e taking up a more functionalist approach to psychology (i.e. they concerned themselves with the functions of the mind, not its elements). The result was, in either case, an odd mixture, in which atom icity and continuity of experience were, it was thought, saved by making the elements interpenetrate or overlap. The main defect of the reaction, however, was th a t it failed to sort out w hat was epistemológica! and w hat was psychological in the older doctrine. In particular it failed, despite the insistence of Bradley and the Idealists on the connection between perception and judgm ent, to see th a t perception and the having of sensations are very different. Sensations, in the sense in which an itch is a sensation, do not provide us with information about other things, except indirectly, whilst perception is always concerned with information about other things. In having sensations we are orientated towards ourselves, in perceiving we are orientated towards other things. We are not provided, in sensations, with a basic knowledge on which everything has to be built, because sensations do not directly give us knowledge of other things but only of ourselves. We cannot begin a psychological account of perception with an assertion of w hat is ‘given’ in the epistemological sense, for epistemology has nothing to do w ith the psychology of perception. This failure to sort out the epistemological and psychological questions which are a t issue is evident in G estalt Psychology also. The G estaltists were inclined to assert in their

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polemics th a t we are not ‘given5atomic sensations but wholes, or things. This assertion is nothing if not m etaphysics, as m ust be any account of the ‘given5, and it indicates how far Gestalt Theory was involved in m etaphysical issues. Bradley5s move towards judgments, like th a t of Malebranche, errs in th a t it over-intellectualizes the interpretative side of perception (and, indeed, involves a metaphysics of another sort), but a t the tim e it was a salutary move. The immediate philosophical precoursers of Gestalt Psychology, however, were the Phenomenologists. The main exponent of this view was Husserl, but the ultim ate source was Brentano5s Psychology from an Empiricist Standpoint. Despite the title, Brentano was really a Rationalist who had been influenced to some extent by the Sensationalists; the term ‘Em piricist5 served to indicate a reaction against the German Romanticists, not to proclaim a scientific psychology. Brentano m aintained th a t psychology was the study of m ental acts—acts of conception, judgm ent and will. Each act had its own object or internal accusative, w hat Brentano called, reviving scholastic terminology, an ‘intentional object5. These intentional objects were, respectively, the concept, the judgm ent or proposition and the attitudes of love and hate. Brentano had two main disciples, Meinong and Husserl. The former was mainly interested in the different kinds of intentional object and their systematization, but from him there stemmed a school of psychology a t Graz, which has become known as the ‘production school5. The main exponents of this school were Yon Ehrenfels and Benussi. They maintained th a t certain contents of experience were basic, e.g. sensations, and th a t others

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were formed out of them by w hat they called ‘production’. Thus Von Ehrenfels emphasized w hat he called ‘gestaltqualitáten’—form qualities. A tune, for example, m ay have a form or structure which is, so to speak, something on top of the elements, the notes of which it is composed. Out of the notes is ‘produced’ a tune, by their acquisition of a structural pattern. Benussi tried to show how in this way higher-level experiences were formed out of lower-level experiences; perceptions were produced out of sensations by the acquisition of a structure, and so on up the scale of experience. The influence of the Sensationalists is here obvious; sensations were considered as atomic and separate, so th a t ‘production’ becomes a sort of glue which stuck them together (W undt’s ‘apperception’ had played a similar role). Husserl, on the other hand, pursuing w hat he called ‘Phenomenology’, claimed th a t it was necessary to consider both the m ental act and its object, as a form of experience. I t was necessary to ‘bracket-off’ all presuppositions so as to leave the experience in its purity. Husserl sometimes claimed a likeness to Descartes in this respect, and it is certainly true th a t his aim, like th a t of m any other epistemologists, was to arrive a t a basic form of experience on which knowledge is to be based. A product of this inquiry was the view which, as we have seen, was also put forward by others, th a t no such things as atomic sensations can be detected; in experience we never get beyond whole objects. As Kohler explains in his The Place o f Value in a World o f Facts, the Gestaltists followed Husserl in this, although Husserl himself was not so willing to return the compliment, and m aintained th a t there was a

4é

THE PSYCHOLOGY OF PERCEPTION

world of difference between his views and theirs. Husserl’s influence made itself felt in two main ways. F irst, it was held th a t psychology involves a consideration of m ental phenomena as they appear to one who knows nothing of the circumstances or relevant theory; all presuppositions, in fact, were to be bracketed off. Hence the emphasis upon the naïve or unsophisticated subject in psychological experiments, an emphasis which had already been made, before the tim e of the Gestaltists, by Hering in his work on colourvision. Second, it was held th a t psychology is not concerned w ith sensations as basic m ental elements; these are, a t the least, a product of analysis, and, as the Gestaltists maintained, erroneous analysis. W hat we are given is ‘gestalten’, wholes which, it is said, are more than the sum of the parts. (W ertheimer explicitly talks of these as ‘given’ in his paper entitled ‘The General Theoretical Situation’ in Ellis, Source Book of Gestalt Psychology.) In some ways this, like the other reactions of the same sort, was a move towards common sense, but the move was incomplete. The use of the expression ‘given’ shows how much the G estaltist view is mixed up with epistemology. T hat in a study of perception we need no reference to sensations is interesting and im portant, b u t there is no need to substitu te for the notion of a ‘sensation’ the mysterious notion of a ‘gestalt’, ‘a whole which is more than the sum of its parts’. In the end result, by saying th a t we are not given sensations b u t rather objects, the Gestaltists tended to discuss perception as if it were ju st like sensation, only having ‘wholes’ as its objects. As I have shown in more detail elsewhere {Psychological Explanation and the Gestalt Hypothesis, Mind

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Vol. 60, No. 240 (1951)), either nothing is more than the sum of its parts or else everything m ust be (according to how one is using one’s terms). Most of the things th a t have been said about the concept of a ‘gestalt’ have previously been said about the concept of a ‘substance’. I t is true to say of anything th a t it is either ju st the sum of its parts, or more than this in the sense th a t a mere summary of the parts does not in itself identify it uniquely, however much this summary may help someone to come to a conclusion about its identity. In giving a complete description of an entity we shall not necessarily have identified it uniquely. Hence w hat things are going to count as ‘gestalten’ is a question of w hat things we are prepared to furnish with some kind of unique identification. The Laws of G estalt Forms (given by W ertheimer in Ellis, op. cit., pages 71 ff.)—th a t we tend to see as wholes w hat have (a) elements which are near to each other (the factor of proximity, (b) similar elements (the factor of similarity), (c) a continuity of contour (the factor of common destiny), (d) a uniform ity of direction (the factor of common movement), (e) a tendency to enclose areas (the factor of closure), (/) a unity suggested by experience (the factor of experience—a factor which the G estaltists tended to play down) and any other factors which may be suggested—may be viewed as generalizations about the circumstances in which we are prepared to give something a unique identification. W ertheim er’s intentions, however, seem to be to discover not ju st the circumstances in which most people give something a unique identification, but those in which anyone would do so. I shall frequently interpret his findings in this light in w hat follows, and I shall

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claim th a t W ertheim er’s real concern is with the defining characteristics of a unitary thing. W hilst the emphasis on the naïvety of the subject is laudable as an attem pt to discover w hat it is natural to see in various circumstances when sophistication is a t any rate relatively ruled out, it should not be given more value than this. Like Husserl, in his suggestion th a t ‘bracketing-off’ enables us to discover the absolutely pure experience, the G estaltists have consistently m aintained th a t the results of their work show th a t experience plays little or no p art in determining w hat we perceive. They have asserted th a t if naïve subjects see something in a certain w^ay, this is an indication th a t experience has no effect on the perception. (The Gestaltists have sometimes tried to dem onstrate this by using very young subjects, but could any suitable subject be young enoagh?) This claim has seemed paradoxical to other psychologists and to philosophers, and the source of the paradox is revealed if the view is seen as an inference from the phenomenological method. I t is a fallacy to take terms such as ‘naïve’ and ‘sophisticated’ as anything else but relative, but the suggestion th a t absolute naivety is possible is encouraged by Husserl’s claim to be able to discover ‘pure experience’. W hilst the phenomenological method may be a good technique for ridding ourselves of our preconceptions in certain circumstances, the view th a t by it we can arrive at something with regard to which there are absolutely no preconceptions is a m etaphysical superstition. Similarly the disparagement of experience on the p art of the G estaltists is not a result of a scientific discovery, b u t a product of a m etaphysical background. The phenomenological method

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in psychology is nothing but the attem pt to consider experience, i.e. what appears to us to be the case, apart from all preconceptions. B ut the fact th a t this is only relatively possible m ust always be emphasized.

CHAPTER

FOUR

GESTALT THEORY

I

H A V E already indicated th a t Koffka claims to give one simple answer to the question ‘W hy do things look as they do?5 w ithout making any distinctions about the conditions under which the question m ay be asked. Because there are two such conditions in general, one when the expectation is th a t the thing will be seen correctly and it is not, and the other when the expectation is th a t the thing will be seen incorrectly and it is not, and because the types of explanation required in these cases are different, one would expect Gestalt Theory to be an amalgam of two quite different things. Moreover, when the question ‘W hy does X look as it does?5 is asked when there is no expectation to the contrary, it is no longer to be considered as a request for a scientific explanation, but something which has more to do with epistemology. This means th a t we m ust expect another strand, a philosophical one, in Gestalt Theory. I shall try to show th a t this is in fact the case. The Gestalt movement began in effect in 1912 with W ertheimer5s investigation of the phi-phenomenon. When two spots of light are projected in succession on to a screen a t a certain distance from each other, we 48

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tend, under certain conditions as regards the intensity of the light, the interval between the flashes, and the distance between them, to see, not two spots of light but one spot moving across the screen. Like many other phenomena which were investigated by the Gestaltists, this was not new; it had already been investigated by Exner, for example. (There are of course affinities between the phenomenon and what happens on the cinema screen.) Exner had attempted to explain it by reference to the workings of the eye, but Wertheimer turned his consideration to the cortex of the brain, postulating irradiation of excitation there. The suggestion was th at when irradiation from one centre of excitation has not died down before another centre of excitation is set up within the range of irradiation of the first, the sources of excitation are seen not as one but as connected. (This notion of irradiation can be brought into play in the case of another phenomenon of the same kind—that of the gamma-movement. When a light source is suddenly switched on it seems to expand; th at is to say th at it seems to us, not that the whole light source comes into view at once, but th at there is an expansion in the field of view from the centre outwards. The effect may be tried by switching on a light in a dark room.) Now it is noticeable th at the phi-phenomenon is an instance of an illusion; our normal ability to discriminate two light-spots has broken down. (In the samé way the cinema film is an illusion.) Wertheimer, however, makes no reference to any of our abilities, but goes straight on to what happens in the cortex, or rather to speculation as to what happens in the cortex. That something must happen there is clear, but it may be nothing of the kind th at the

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G estaltists postulate. W ertheimer’s suggestion, however, led to a general thesis which has been called th a t of ‘isomorphism’. The thesis asserts th a t there is always a sim ilarity of structure between the phenomena as seen (what has been called the ‘phenomenal’ or ‘behavioural environm ent’) and the corresponding cortical processes. The G estaltist view in general has come to be th a t this similarity is topological rather than geometrical, but it has raised some opposition from neurologists, in th a t it entails the treatm ent of the cortex, not as a system of discrete nerve-fibres, b u t as a field of forces akin to an electrical field. Indeed latterly, in response to such opposition, Kohler has taken it upon himself to carry out investigations which, he thinks, m ust dem onstrate the existence of cortical processes such as those which have been denied by neurologists, e.g. his work on figurai aftereffects (the effect th a t perception of one kind of figure may have on the subsequent perception of another), which he puts down to a satiation of the cortex, explicable in term s of field-forces there. (See his Dynamics in Psychology.) To return to the phi-phenomenon—it is clear th a t the general pattern of the account offered is th a t the light-spots act as stimuli to the eyes, so, in the last resort, setting up excitations in the cortex with which the perception is correlated isomorphically. To offer this account is to treat perception as if it were a mere sensation—the end product of a pattern of stim ulation, albeit modified by intervening neural processes. Now this, I think, is typical of Gestalt Theory. The Gestaltists refused to distinguish between sensation and perception, and in doing so they assimilated the latter

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to the former. To see something in a certain way, however, presupposes an ability; to see two lights as distinct presupposes an ability to distinguish them, an ability which a baby, for example, may well not possess. W hether or not such abilities are acquired, it is clear th a t they exist. To have a sensation, on the other hand, presupposes no such ability, although the identification of its source m ay do so. Now the reason why the Gestaltists treated perception as if it were merely sensation is, I think, th a t their predecessors, the Sensationalists, did so. For the latter, all perception was the having of sensations plus associated ideas. In effect the Gestaltists tended to deny the associated ideas and the atom icity of the sensations which act as the given (it is to be remembered th a t this word ‘given5shows th a t whilst the mechanism whereby these sensations were supposed to be produced was physiological, their status was epistemological, so th a t a real confusion is involved). W hat we are now said to be given in sensation is the whole phenomenon—in this case the moving light. So, when the Gestaltists denied th a t any distinction was to be made between perception and sensation, they were not introducing a completely new view; they were merely denying th a t any role was to be given to the old atomic sensations. I t m ay indeed be said th a t it is normal or natural for the phi-phenomenon to occur, although it is a good deal more labile than the G estaltists have given us to suppose. The claim th a t it is ‘given5, however, amounts to the thesis th a t we must see it under certain conditions, not merely th a t it is normal or natural to do so; and indeed the reasons for this necessity lie in the

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causal chain which extends from stim ulation, through cortical processes, to final perception. The lability of the phenomenon might be explained by reference to inter-personal differences in the constitution of the cortex, b u t the objections to the G estaltist account do not depend only on the fact of such lability, but on the logical errors involved in their view of perception. To perceive something as possessing certain characteristics presupposes having classified it, or mis-classified it—th at is to say th a t it presupposes an ability or skill in classifying things. None of this is reflected in the G estaltist account. Nevertheless the lability of the phenomenon, as with most illusions, is real enough. K orte attem pted to form ulate laws relating the different variables involved for optimum appearance of the phenomenon. He claimed th a t if the intensity of the light-spots involved in producing the phenomenon is increased so th a t it no longer occurs, optimum appearance of the phenomenon may be restored by increasing the distance between the light-spots, or by decreasing the tim e-interval between their exposure. Thus, for optimum appearance of the phenomenon intensity varies directly w ith distance, and inversely with timeinterval. Finally, tim e-interval varies directly with distance. On pages 291 ff. of his Principles Koffka attem pts to give these ‘laws’ greater status by bringing them into connection with Brown’s ‘laws’ of the apparent velocity of actually moving objects (with regard to which I shall say more later), b u t nothing can contravene the fact th a t K orte’s Laws as such have not been found to hold generally (see, for example, Vernon, A Further Study of Visual Perception, page 168); and even Koffka, following Cermak,

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has been forced to add im portant restrictions to the original laws. None of this is really surprising. W ertheim er’s position and the G estaltist position generally is th a t w hat we see is a product of interaction between the stimulus pattern set up by the object and the cortical processes which ensue. The former Koffka has called ‘external forces’ and the latter ‘internal forces’. The tendency of the internal forces is towards the production of a percept which has ‘good form ’, ‘good gestalt’ or ‘prâgnanz’. W hat this seems to mean is th a t there is always a tendency to see an object as being simple, regular, symmetrical, continuous, closed and the like. Thus, in the case of the phiphenomenon, the situation is th a t if the external forces, the conditions of stim ulation, allow there is a tendency to see a continuous movement, rather than a succession of flashes of light. In general, the weaker the external forces, the greater the tendency towards ‘good form ’. This is, perhaps, the most general thesis of G estalt Theory. I t is held not only th a t we see whole objects or forms, rather than parts which we synthesize, b u t th a t there is a tendency to see such forms, gestalten, as being as simple or ‘good’ as possible. This last fact is supposedly due to the nature of cortical processes, which correspond to field forces, rather than to discrete channels of excitation. This claim needs, of course, neurological confirmation which it has not generally received, b u t in any case Kohler felt it necessary to show th a t such tendencies to ‘good gestalt’ do occur in nature. This he did in his paper on ‘Physical G estalten’ (Ellis, op. cit., Chapter 3), in which he gave examples of such phenomena. The best known is perhaps th a t of the soap-bubble, in which the various

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forces a t work tend to produce a spherical shape. W hether or not we do tend to see objects in the way outlined is an empirical m atter, and the evidence is not clear-cut. Wulf, for example, claimed th a t successive reproductions of figures by subjects tended towards ‘good form ’, but others have found th a t the factors which are involved are more complex (see Vernon, op. cit., Chapter 4, and Woodworth, Experimental Psychology, pages 80 ff.). I t may well be the case th a t we have a tendency to see figures in a simple way, bu t this is by no means universal or unqualified, and in any case the tendency may have nothing to do w ith the neurological hypothesis put forward by the Gestaltists. By very reason of their account of the m atter, however, the Gestaltists m ust claim universality and m ust eschew any suggestions about influences from experience or convention. So far, then, the Gestaltist point of view has been seen to consist of the epistemological view that we see whole things or forms, and not sensations or sense-data out of which things are synthesized, and also of the view th at we tend to see forms so th at they are as ‘good’ as possible. I have already commented on the latter. W hat is still not clear about the suggestion is whether it is to the effect th at we tend to see forms as ‘good’ when this is an illusion, or whether in the case of forms which we have come to identify as such we have done so because we are influenced by factors such as ‘goodness’, i.e. whether ‘goodness’ is a defining characteristic of forms. Clearly we cannot see forms as ‘good’ when we are not subject to illusion unless the forms themselves are ‘good’. ‘Goodness’, then, might be a prominent characteristic which we are liable to

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attrib u te to things, or it m ight be the defining characteristic of whatever is seen as a form or object a t all. In the latter case we are concerned again with the philosophical aspect of G estalt Theory, an aspect which is philosophical because it am ounts to a view concerning the use of the word ‘see’. As I have said in the previous chapter, W ertheim er’s ‘Laws of Gestalt Form s’ am ount to statem ents concerning the factors on which we rely when we distinguish the things which we see; it m ight be said th a t the factors which I referred to in the last chapter sum up w hat is m eant by calling a form ‘good’. Another thesis of which the Gestaltists have made much has a connection with this—the thesis put forward by Rubin th a t what we see consists of a figure on a ground. The figure possesses greater form-properties, i.e. coherence, etc., than the ground and this applies even to ambiguous figures such as figure 2. For

F

ig u r e

2

whether we see this as a cross with vertical and horizontal lines, or whether we see it as a cross w ith arms

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a t the diagonals, the cross is always seen as a differentiated form against the background of the rest of the square, even if this very background a t other times becomes the figure. All this is dignified under the title of the ‘figure-ground hypothesis5, th a t whatever we perceive is divided into a figure and a ground, and th a t this distinction is imm ediately given, not something which we have to learn to make. I t hardly, however, deserves this dignity, for, clearly, when we identify an object we m ust distinguish it from everything else which forms its background. W hat we mean by an object is something which can be so distinguished and it would not make sense to talk of our seeing an object which was not so distinguished. Thus to call it a ‘hypothesis’ is a t the least misleading. To say th a t the tendency to distinguish figure and ground is innate is also misleading, for the tru th is th a t if we are to see an object a t all, it is a logical necessity th a t we m ust distinguish it from a background. This is not contingent and therefore not a m atter of experience. Perceiving something involves identifying it, and identifying it involves distinguishing it from other things. But, to say th a t if we see an object a t all it is not a m atter of experience th a t we have come to distinguish it from a background is not the same as saying th a t the figure-ground distinction is innately given. I t may, of course, be a m atter of experience th a t we have come to distinguish a particular figure from a particular background, but th a t figures in general need a background cannot be a factual hypothesis. The world of the baby might be, as William Jam es suggests, a blooming, buzzing confusion—in which there is no figure and no ground. The baby m ust, of course, have

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the capacity for learning to distinguish objects, buttas long as such a capacity is not exercised we may not allow that he sees anything. The thesis that the figureground distinction is innate, however, suggests that the baby is born making such distinctions, and this is unlikely. I t is certainly true th at we are born with the capacity for learning to distinguish objects, on the other hand, and once we do so we see them against a background as a matter of logical necessity. The ‘figure-ground hypothesis’ has been put to a generalized use by Koffka, with the claim that however we see what we see, this is determined by the framework into which we fit it. The logical truth th at the concepts of ‘object’ and ‘background’ presuppose each other is turned into the supposedly explanatory hypothesis that the way in which we see objects is in general determined by the framework. This kind of shift is typical of the Gestalt movement, and it is also true that it is not made clear just what these principles are meant to explain, and, indeed, what kind of explanation it is. For, it is a logical truth, as I have said, that a thing cannot be perceived except against a background, but it is an empirical truth, if it is a truth at all, that things often appear to us in certain ways because of the background into which we fit them. It would also be an empirical truth th at we are sometimes not subject to an illusion, when we might be expected to be, because we go by the total context or framework in our estimate of the situation, and not only by the object which is the immediate object of the illusion. (It may be remembered th at Koffka says in answer to the question ‘Why do things look as they do?’th at the answer ‘Because the proximal

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stim uli are w hat they are’ is true in its broadest interpretation.) I t is not only the ease, however, th a t these ‘tru th s’ are of different kinds, bu t it is also doubtful whether there can be ascribed to the two offered as empirical truths the kind of universal validity upon which the Gestaltists have insisted. I t is no doubt true th a t we are often influenced by the general framework, for this is more stable and unchanging than its contents. B ut th a t we are always so influenced could be held only by one who is prejudiced by some theory so as to be blind to the obvious differences in the attitudes which people adopt towards w hat they see. The ‘innocent eye’ of the artist is clearly not determined in its vision by the same factors as is the eye of the ordinary man in the street. I t m ust be adm itted th a t the Gestaltists have not always been absolutely blind to such facts. The effects of experience have been allowed some weight, for example, in W ertheim er’s Laws of G estalt Forms. B ut such effects have been played down. The reason for this is, I think, not hard to find. The general theory does not allow for these effects. For w hat the theory says is th a t whatever we see is a product of the interaction between external forces set up by stim uli from the object and autonomous internal forces in the cortex, so th a t we see things as wholes and as wholes with the simplest or ‘best’ structure. The apparatus of the theory is so far purely physiological and perception is regarded merely as the end-product of such processes of neural excitation. This is a conceptual mistake, b u t it is reinforced by the adoption of the phenomenological method, with its assum ption th a t a naïve approach to phenomena can lead to the discovery of the ‘pure

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experience5, untainted by preconceptions. The discovery of this ‘pure experience5 has been regarded as the discovery of w hat we really see. Despite these general defects, it is clear th a t concepts such as ‘context5and ‘framework5could be given good explanatory uses, in ways which I have already suggested. They could be used to explain some illusions, and some cases in which we are not subject to illusion, although the pattern of explanation in these cases will be different. Thus it is not surprising th a t within the context of G estalt Theory much useful work has been carried on. There is, for example, the work on the effects of the perceived form on other perceived features of the object—e.g. Benary5s work on the influence upon brightness contrast of the forms to which the contrasting areas belong, and the work of Fuchs, Tudor-H art and Heider on the manner in which the perceived colour of areas seen through a coloured transparency is influenced by the forms to which the areas are seen to belong. This work shows, not th a t we always see things in configurations, but the more modest, and indeed more respectable finding th a t our way of identifying w hat we see influences the look of what is there to be seen. If we identify one p art of the field of vision as belonging to a certain configuration, this may make it look different from the way in which it looks if we attribute it to some other configuration. Other findings are possibly less respectable because so much is claimed as deducible from the experiments. Thus Kohler made claims for the tendency to see things according to their structure or relationships rather than according to their individual properties, on the

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basis of experiments of the following kind with hens and chimpanzees. The animals were, for example, allowed to eat from a medium-grey card but not from a light-grey one placed next to it, and were so trained in their behaviour. When they were presented with a medium-grey card and a dark-grey card, they tended to choose the dark-grey card from which to eat, so, presumably, indicating th at they had seen the medium-grey card in the first instance as darker, and not as possessing the absolute properties which it had. The evidence is, in fact, less definite than I have allowed for, and in any case the results have often been disputed since, and indeed contraverted by fresh experiments. I t is certainly not the case th at there is always a tendency to go by relative characteristics; other factors may influence what we or animals do and the result does not seem to hold good, for example, where there is difference of hue and not merely of brightness. But this last fact would seem to confirm what common sense would tell one. Unless we establish the intensity of the light given off by them, the only way for us to distinguish otherwise identical objects of different degrees of brightness is in terms of their relative position in a scale of brightness. Indeed our very use of words indicates this. If, therefore, we were to set up an experiment in which objects were to be distinguished which we should naturally distinguish in terms of their relative properties, we should hardly be surprised if the animals behaved in a similar fashion. What Kohler’s experiments show is not th at there is a tendency to see things relationally, but th at where there is a relative distinction to be made we naturally

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make it in relative terms, and th a t if we are taught to act in accordance with this distinction in one situation, we shall tend to do so in analogous ones. T hat is to say th a t if we were presented with two objects, one brighter than the other, and taught to behave in certain ways towards one of them, say the brighter one, we should naturally formulate the principle of our behaviour by saying, Ί m ust behave in this way towards the brighter one’. For where properties fall within a scale it is easier to identify them by reference to the properties of the scale than in any other way. This, however, does not apply to all properties whatsoever. Kohler’s findings, in other words, were determined by the peculiarities of the set-up of his experiment, and they are not generalizable. Certainly it is impossible to take the experiments as showing th a t in perceiving we see things in term s of their form or structure first and foremost. A nother instance of this tendency to make sweeping claims on the basis of particular and limited experim ents is provided by Koffka’s interpretation of G ottschaldt’s work on the effect of repetition on the recognition of figures. I t has been noted by most G estalt psychologists th a t even familiar figures tend to lose their identity when set in a wider context th a t has an identity of its own. Thus Kohler showed in his Gestalt Psychology how a figure ‘4’ could fail to be recognized as such when incorporated in a system of lines. The to tal context, it may be said, draws our attention away from the details, so th a t to detect the latter we should have to adopt a specific attitude, as we do in m any puzzle-pictures. T hat is to say—and so far one may agree with the G estaltists—th a t there is

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often a natural way to see patterns, if we do not adopt a specific attitude towards them. This follows from W ertheimer’s ‘Laws’, which, as I have interpreted them, state the factors which make it natural for anyone to identify a form or object in a given way. G ottschaldt’s immediate purpose was to show th a t there are situations in which experience has apparently no effect in determining how we see a pattern. He did this (see Ellis, op. cit., Chapter 9) by concealing certain relatively specific shapes within more complex ones. For example, in Figure 8, shape (a) is concealed within shape (b).

(b) (a) F

ig u r e

3

The procedure with his subjects was th a t he exposed shapes like shape (a) a great number of times with a short exposure each time (the to tal num ber of exposures was, in fact, 520, an incredible number if the subjects were to keep awake). He then exposed the complicated figure and asked for a description of it. Very few cases occurred (5 per cent in all) in which subjects detected the simple figure within the complicated one. In control cases, where the simple figure was exposed only three times, there was very little difference in the num ber of instances in which the simple figure was detected within the complicated one (in fact 6*6 per

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cent of control cases detected the simple figure). The conclusion drawn was th a t experience or fam iliarity had absolutely no effect. I think th a t other factors might be recognized here, and indeed subsequent investigations (see, for example, Vernon, op. cit., pages 63 ff.) have shown th a t differences in the attitude of the subject and the complexity of the enclosing figure, and the way in which it is natural to see it, do have an influence. G ottschaldt claimed in a modest way th a t the results showed th at the theory was wrong which stated th a t experience alone determines how we see patterns. Koffka, on the other hand, claims (op. cit., page 157), ‘The conclusion is th at experience does not explain why we see a line pattern in the shape in which we see it, bu t th a t direct forces of organization, such as we have analysed, m ust be the real cause’. Behind this statem ent may again be detected the model of forces in the object interacting with forces in the cortex in a specifically causal way. Perception is treated as the end-product of a process of stimulation, not something in which we engage. I have yet to mention, first, further work on the perception of movement, both apparent and real, and second, work on the so-called constancy phenomena. Some work on apparent movement, i.e. W ertheimer’s investigation of the phi-phenomenon, has already been discussed. To this m ust be added the work of Ternus and Von Schiller on the effect which the perceived pattern of the lights cast on the screen has on their apparent movement. These last investigations may be classed with those of Benary, Fuchs, etc. Also of interest is the work of Duncker on the influence upon

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apparent movement of what is taken as the frame of reference. None of these investigations, however, leads to conceptual problems other than those already noted. The same remarks apply to Brown’s work on the apparent velocity of actually moving objects, and there would be no need to say anything about it except that, as I mentioned earlier, Koffka attempts to deduce Korte’s ‘laws’ of the phi-phenomenon from Brown’s ‘laws’, and claims further th at Brown’s findings are applicable to all movement, real or apparent. Brown found that in a homogeneous field the apparent velocity of moving objects is dependent on other factors, notably the size of the objects and the field, but also its illumination. Thus, if the size of the field and that of the objects moving in it is doubled, the apparent velocity is halved. Likewise, increase in illumination decreases the apparent velocity of the moving objects. (In driving at night one often seems to be travelling more quickly than at a corresponding speed by day.) Koffka’s explanation of these findings is th at the more structured the field, i.e. the more strongly articulated the figures in it, the less they appear to move. Once again, there may be something in this if we interpret it as saying th at our estimates of a thing’s speed of movement are affected by the form which we attribute to that thing. Whether this is the correct account of the facts or not does not for present purposes matter; whether it is the correct kind of account, however, does matter. It is not, however, this kind of account that Koffka intends to give; for him the situation must be brought into line with analogous ones, with the usual explanation in terms of the interaction of forces. The fact th at Korte’s ‘laws’ follow from

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those of Brown says nothing of itself for either. All th a t may be deduced is th a t in our perception of apparent movement and in our perception of the apparent velocity of actually moving objects we tend to go by the same factors. This is, of course, interesting, b ut it says nothing for the theory. In turning to the constancy phenomena we change our point of view. As the term ‘constancy5implies, the problem in this case is th a t of why we tend to see things w ith a certain constancy of size, shape, colour, etc,, despite changes of distance, perspective, illum ination and the like. Here we are required to account for our ability to identify objects correctly, not to account for why we fail to do so. I t is a fairly common belief th a t objects seen at a distance look small, th a t circular objects seen at an angle look elliptical, and th a t objects seen in a coloured illumination look coloured. Up to a point such beliefs are reasonable; women will not generally choose coloured fabrics in artificial light, and when looking down from great heights we often say th a t the people below look like insects. Yet it is perhaps not often realized how seldom we are deceived in such cases, or th a t in the great m ajority of cases we do not notice any distortions due to distance, angle or illumination. W hite objects in shadow generally look white, and it is interesting to work out the geometrical projections upon our retinae of the objects around us and notice how different these shapes are from the shapes which we see these objects as possessing. Photographs taken looking down a straight road show the edges of the road converging according to the laws of perspective as they would never ordinarily look to us; and photographs often show contrasts of light and

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shade which we should not normally be aware of. We generally make allowance for such things even when looking at photographs, but they can be noticeable nevertheless. The reference to photographs is appropriate in this context, in that the eye is often considered as a kind of camera, and subsequent neural processes are viewed as merely touching up the picture taken. This, I think, is the view implicit in Gestalt Theory. How is it, then, that we do not generally see things as the camera does? Psychologists, especially the Gestalt Psychologists but also others such as Thouless, have undertaken investigations into how far this constancy of size, shape, colour, etc., holds good. It has been found to be very variable from one person to another, but everyone perceives things with some degree of constancy. In some cases there is even over-constancy; that is to say that things seen at a distance, for example, may look bigger than normal. But why should this be the case at all if the eye is like a camera? Koffka has produced a rather complex and difficult theory to explain these phenomena. It is worth while to consider the general character of the theory, although it is, I think, unnecessary for present purposes to go far into the details. Such considerations will bring out the extent to which the Gestaltists were tied to one model, a model which obscured the differences between the various problems with which the psychology of perception has to deal. Koffka’s general approach consists in having recourse again to the concept of the ‘framework5. He maintains th at unless circumstances upset this, we take the framework as constant and invariable, so th at we relate the details of what we see to it. Sometimes this

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will lead to illusion, as in the ease when we are sitting in a com partm ent of a train and, taking everything outside as constant, we think th a t the train is moving when in fact another seen -through the window is doing so. So far this seems very reasonable, but it will not account for the constancy of objects within the fram ework. In consequence Koffka postulates a num ber of invariants between, as he puts it on page 224 of his work, certain aspects of stim ulation. Elsewhere, on page 236, he puts the point by saying th a t some effect will be invariant for a given stimulus. This reference to stim uli and stim ulation is worth noting. The postulated invariants are in fact relationships between certain properties which we see the objects as possessing. For example, in size-perception the apparent size of an object, given a certain pattern of retinal stim ulation, is proportional to its apparent distance. The lightrays from an object seen a t a distance will stim ulate a smaller area of the retina than will those from a similar object near to the eye, b u t because the object is seen as distant it is also seen as being of a similar size to the object near a t hand. Analogously, in shapeperception the invariant is the relation between apparent shape and apparent orientation. In brightnessperception it is the relation between, say, the apparent whiteness of the object and the apparent brightness of the illumination. An interesting exemplification of the last invariant is provided by Gelb’s experiment. Gelb illum inated a rotating black disc in a dark room so th a t only the disc was illum inated. In such circumstances the disc looks white in contrast with the room; b u t when a piece of white paper is held in front of the disc,

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the latter looks black, though brighter than the background. The account provided by Koffka, if it is satisfactory a t all, would explain relative constancy, i.e. why an object a t a distance, for example, is still seen as more or less the same size as one near to the subject. I t would not, however, as Koffka agrees, explain why we see things as possessing the size, shape, colour and so on th a t they do. Koffka says on page 230, CA theory would have to answer the question when a circular retinal image will lead to the perception of a circle, when to th a t of a non-normally orientated ellipse, and why it has the two different effects in the two different cases’. Thus certain instances of how we perceive things have to be taken as unique, and others derivative from them. In shape-perception, for example, perception of an object in the frontal-parallel plane is the unique case. B ut why is it unique? Here Koffka rules out w hat he calls the Veridicalness of the percept’, and concludes th a t the frontal-parallel plane is well balanced, so th a t non-normal orientation sets up a field of stress with the result th a t forces tend to restore the balance and make us see the objects as we would in the normal frontal position. Shape-perception perhaps provides the easiest case to account for in this way, as theref seem to be grounds for taking the frontal view of an object as the view of its shape. B ut w hat is ths view, for example, of its size? Koffka is obliged to assume th a t the view of an object’s size is provided when the object is within a certain range of distance from us, and in the light of Lauenstein’s suggestion th a t constancy holds within certain ranges of distance from us but varies from range to range, he adopts the further

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suggestion th a t ‘the “real” (normal) behavioural size may appear within th a t range which includes the observer’s behavioural Ego’ (page 237). Some of this is suggestive. There is no doubt a relation, for example, between the size which we see an object as possessing and the distance a t which we see it, but this will be so only if we have some means of estim ating one of these. The reason why we see a man a t a distance as more or less the same size as we see him when he is near to us is th a t we tend to allow for the distance. B ut to treat the m atter in this latter way is to tre a t perception as involving a skill, so th a t we employ techniques in its operation, even if we do not make fully-conscious inferences. When we learn to identify an object as of a certain size, we do not do so merely by coming to know its size in a standard situation and then inferring w hat is its size when we see it a t a distance, although certain situations provide the easiest and most exact way of determining its size. (The m ost exact way of all, of course, is to measure it, in which case we put a standard measure into one-one correlation with the object, so allowing as little room as possible for error.) In fact, we learn an object’s size in a variety of cases, not ju st in one standard one, and we learn th a t something is blue while seeing it in a variety of illuminations, even if we should refer to the standard cases for verification. B ut this means th a t the frontal-parallel position in shape-perception m ust be taken as standard in the sense th a t we should refer to it as p art of our procedure for verifying our estim ate of the shape of the object. Another way of putting this is to say th a t ‘seen as round in a frontal-parallel position’ enters into our definition of ‘round’; what we mean by

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saying that an object is round is, in part, th at if it is seen in a frontal-parallel position it looks round. Thus, this position is unique or standard because reference to it is involved in determining the correct use of the shape-description or the correct characterization of the shape. Koffka’s account is not at all like this. For him, the standard case is the one in which the situation is well balanced or simple, as if it were a law of nature that the way in which we see things tends to follow the simplest or the most balanced lines. Moreover, this ‘law’ is presented as if it were due to the conditions of stimulation and subsequent neural effects, the interaction of external and internal forces. How we perceive things is once again treated as the end-product of a process of stimulation; and it is for this reason th at I earlier drew attention to Koffka’s terminology. There is no reference to any skills which we may employ, skills which are presupposed in the success or failure of our identification or characterization of objects. In the case of the constancy phenomena we are in fact called upon to explain why we are successful in these identifications and characterizations in a large variety of circumstances, and how far we are so. There is none of this in Koffka’s account. It is notorious that the Gestalt Psychologists have insisted th at the phenomena of perceptual constancy are constitutionally determined; we do not learn to perceive things more or less correctly. For evidence of this they have appealed to experiments with young children and animals, and have stressed the naivety of the subjects when these have been adult. (There is no doubt th at the taking up of a sophisticated attitude by

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a subject will influence the results of an experiment.) The objection with regard to all such experiments is th at they cannot be performed except with subjects who have had time to learn to identify objects in a variety of circumstances. Anyone who can see things must be able to identify them in a number of circumstances. Otherwise we should not allow them the claim to see things at all. The view that perceptual constancy is innately determined has always seemed paradoxical, and such considerations as I have brought forward must confirm this feeling of paradox. The truth is that the model employed will not admit of any other conclusions being drawn than those which are drawn; for the constancies are set down as being due to organization of stimulation. And once again the adoption of the phenomenological method with its claims for absolute naïvety reinforces the conclusions drawn from the theory. I t need hardly be said that subsequent work (for this see Vernon, op. cit., Chapter 6) has cast doubt both upon the thesis of nativism (at any rate in human beings and some animals—th at much of the behaviour of some animals is instinctive cannot be denied), and upon the claim of Koffka to have discovered laws of a thorough-going sort. It is not surprising that the situation is more complex than the Gestaltists have supposed; for, if what I have said is true, the number of factors on which we may rely in coming to see things as possessing the properties that they do possess is likely to be large, and correspondingly the chances of making mistakes will be great. Indeed the study of the circumstances which lead to the break-down of perceptual skills may be more rewarding than attempts to look at our

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successes as conditioned in any simple way. We ought not to be surprised th at the apparent size of things, for example, does not correspond to what would be expected on the basis of the laws of perspective alone. Geometrical optics is in this respect a bad teacher. That the way in which we see things has something to do with the way in which the retinae of our eyes are stimulated is clear. But the situation is not th at our eyes provide us with a photograph which is what we see, or a photograph which provides us with a basis for making inferences as to what we see. For the thing which is actually missing is the photograph itself. Perceiving is not merely the receiving of sensations, nor is it this plus judgments. The having of sensations is not part of perceiving, although perhaps if we never had sensations we should not perceive anything either. To put the m atter in another way, perception is not the last term in a process of neural excitation, although without such excitation we should not perceive. Stimulation of our sense-organs is a necessary condition, not a sufficient condition of perception. When we say th at a man perceives something, we register his success in identifying that something, and also indicate the means of his identification, i.e. by the use of his senses. Similarly when we say th at a man perceives something as possessing certain characteristics, we register the fact that he has interpreted th at something in a certain way, and again indicate the means of his interpretation. A man who perceives something in a certain way is disposed to behave in appropriate ways towards it, by very reason of his interpretation; in perceiving he need not be interpreting in fact, but interpretation must have gone on at some time. The

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features on which we may rely for the identification or interpretation of an object, and the features which may deceive us in this are clearly various. In sum, most of the investigations of the G estalt Psychologists can be classified under headings corresponding to the three strands which I distinguished at the beginning of this chapter. (1) There are the investigations into illusions, into the ways in which things appear to us. Under this heading can be put, for example, investigations into the phi-phenomenon, the apparent velocity of actually moving objects, and, in general, the influences of the perceived form of an object on its other perceived characteristics. (2) There are the investigations into perceptual skills, of which the chief examples are the investigations of the constancies. (3) There are the investigations into w hat we take as the defining characteristics of ‘gestalten’. This last inquiry ought to be treated as philosophical in as much as, although empirical inquiries m ight be initiated as to w hat people are prepared to say on this m atter, W ertheim er’s concern is really with w hat any m an would naturally say. W hat any man would naturally say gives a clue to the nature of the concepts involved. Similar rem arks m ight be made about R ubin’s work. Indeed, a great number of statem ents about ‘gestalten’, such as th a t these are what we really perceive, are, in effect, philosophical and thus not amenable to empirical inquiry. T hat they are not so amenable is im portant, since Kohler’s attem pt to show th a t we perceive structural properties first and foremost, by reference to the supposed fact th a t animals go by the relative properties of things, m ight be considered as an attem pt to establish a philosophical

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conclusion by experimental means. But this is a forlorn hope, for philosophical puzzles are conceptual and can be solved only by conceptual inquiries. There are two possible exceptions to the classification given above. Kohler’s later work on the alternation of what is perceived in ambiguous figures and his work on figurai after-effects (for which see his Dynamics in Psychology) might be included under one of the headings given above, but the fact th at it is determined by neurological theory may be reason for keeping it separate. Prima facie, Gottschaldt’s work also falls outside the classification, for it might be said that his complex figures had no one correct description, and that what he was interested in was whether experience or something else determined how his subjects happened to describe them. Yet whether or not the complex figures had one correct description, they certainly had a natural description. The difficulty with regard to Gottschaldt’s experiments is what, if anything, they show at all. In consequence I prefer to leave his work with a question-mark. I have indicated th at the three types of inquiry are included within Gestalt Psychology without discrimination. I have shown also that concepts such as ‘gestalt’ and ‘framework’ are used indiscriminately, with the suggestion that the same type of explanation is applicable in each case, even when this is impossible. I have indicated also how far this approach was determined by a view of perception which involves a conceptual mistake, i.e. the view that it is possible to isolate a pure perceptual experience which is the end-product of a process of stimulation, albeit modified by autonomous neural processes. This view

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is enshrined in the hypothesis of isomorphism and in Koffka’s doctrine of external and internal forces, and it is reinforced by the phenomenological approach to perception.

CHAPTER

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T

H E two psychologists whose accounts or perception I wish to consider in this chapter are A. Michotte and J . J . Gibson, whose main works are respectively La Perception de la Causalité and The Perception of the Visual World. In both cases there are grounds for describing their approach as phenomenological, and this is especially true of the former. In his main work Michotte has attem pted to study the impressions which we have of causality, and to this he has added further work on our impressions of purpose, reality and substantiality (for details of which see Vernon, op. cit., Chapter 9). In his work he has stood out in opposition to philosophers like Hume, who denied th a t we have any impressions of causality and asserted th a t the necessity which we attrib ute to causal connections is due to an idea in the mind which accompanies certain features of the events which we take as cause and effect—notably their constant conjunction. M ichotte interprets this as saying th a t we have no immediate impression of causality, but he takes the word ‘impression’ to be used in its ordinary sense and not in Hum e’s more technical sense. Because Hume used psychological term s there is some excuse 76

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for thinking th a t he was talking psychology, b u t I think th a t it is truer to say th a t he was attem pting to provide an analysis of our notion of ‘cause5. H um e’s thesis is compatible with the thesis th a t in some sense of the word ‘impression5, we do have an impression of causality, b u t the main purpose of his investigation was not to pursue phenomenology; he was not primarily concerned w ith how things appear to us. When, however, Michotte says th a t our impressions of causality are immediate, he implies th a t there is no question of learning th a t the phenomena are causally connected. This seems to conflict w ith Hum e’s demand for constant conjunction, and indeed w ith our ordinary beliefs on the m atter. M ichotte’s position, then, is th a t under conditions which he has investigated we see one thing as causing effects in another, and in this we make no interpretations and no use in any way of past experience. For the perception is direct and immediate. This view is directly in accordance w ith the Gestaltist position. As I have said with regard to the latter, the phenomenological approach has led, first, to observations which may be of some interest, bu t second, to the drawing of conclusions which are a t the least a non-sequitur. I t is worth nothing th a t M ichotte does not use real objects in his experiments (indeed if he did he would not be able to investigate w hat he in fact wishes to investigate). Instead he uses an apparatus consisting of a marked disc rotating behind a screen in such a way as to give the appearance of rectangles moving along a slot in the screen. Under certain conditions, when one rectangle A moves along the slot to another rectangle B, it seems to cause the latter to

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move. Michotte has investigated the conditions under which this and other phenomena of the same kind occur. We are here again confronted with an illusion and are thus concerned with the appearance of causality only (rectangle A does not in fact cause rectangle B to move). This is as it should be if the approach is phenomenological. Now by studying the conditions under which we are deceived we can gain clues as to what we take into consideration when we are not deceived. (I am not suggesting th a t Michotte sees the m atter in this light; far from it.) The conditions under which such appearances are produced are, therefore, interesting in the same way th a t the conditions for the production of other illusions, such as apparent movement, are interesting; although once again I doubt whether any precision is to be expected as regards the variables involved. The suggestion, however, th a t this means th a t our perception of one thing causing an effect in another owes nothing to experience depends upon two misconceptions: (1) I t depends upon a misconception of phenomenology in th a t it involves the assumption th a t by it we may isolate the ‘pure experience’. Like the Gestaltists, Michotte has appealed to the naivety of the subjects and has sought empirical evidence from experiments with children (despite what m ight be taken as the counter-evidence of Piaget’s work with children). I t remains true, both th a t absolute naivety is a m yth, and th at, for these experiments to be carried out a t all, the subjects m ust have had relevant experience and acquired the relevant ability to see one thing as leading to another. (It is noteworthy th a t in his attem pts to produce the impression of purpose, Michotte found the

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phenomena much more labile. We are not, of course, used to seeing simple objects like rectangles behaving purposefully.) (2) I t depends upon a misconception of the notion of *cause\ Hume was anxious to point out both th a t the causal connection is not a logical one and th a t being the cause of something is not a perceptual property of an object in the same way th at redness is. In the latter respect H um e’s point was th a t A’s being the cause of B is not the sort of thing th a t we could perceive directly, w ithout previous experience of the uniform connection of things like A with things like B. This is a perfectly valid point. I t is, moreover, a conceptual point, which no am ount of experiment can gainsay. M ichotte’s investigations into the perception of things as real and substantial are akin to those of W ertheimer into G estalt Forms. They am ount to an inquiry into the conditions under which anyone would naturally attribute reality or substantiality to things. A conceptual inquiry by itself could establish with which other concepts those of reality or substantiality have connections or family relationships. I t is no surprise to learn th a t there is a connection between substantiality and permanence. We could establish such a conclusion by considering our use of the concept of a ‘substance’. Words like ‘real’ and ‘substantial’, however, get their meaning only by contrast w ith their opposites. When someone claims to see something as real, we know th a t a contrast is being made w ith w hatever he takes as unreal. Analogously, in investigating the perception of things as real, Michotte m ust be investigating the conditions under which we see something as not unreal. The natural procedure in such

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cases would be to take something which is adm ittedly unreal, and try to produce the illusion of reality. So one finds Michotte exhibiting two-dimensional drawings or models of three-dimensional objects (e.g. a drawing of a cube) in such a way as to make it really look a three-dimensional object. A two-dimensional drawing, a projection of a cube in two dimensions, does not normally look real; it looks only as i f real, as i f three-dimensional, even though the depth which it looks as if it possesses may be estim ated. I t is necessary, therefore, to produce the effect of reality by various means, e.g. by drawing into the picture the effect of constancy, or by cutting out clues to the perception of the actual dimensions of w hat is seen. Similarly, with regard to substantiality or permanence Michotte exhibits patches of light which, whilst not actually permanent, look so under certain conditions. Thus in this case, as in others, the illusion is considered for the sake of w hat light it m ay cast upon the cases in which we are free from illusion. Michotte claims th a t his concern is to discover the conditions under which we tend to have impressions of reality and substantiality. Y et w hat do the conditions in such cases am ount to? Surely all th a t is being said with regard, for example, to reality is th a t a thing will look real as long as it does not look unreal. A twodimensional drawing of a three-dimensional object will not look a real object as long as it still looks twodimensional. An object will not look perm anent as long as it lacks a natural continuity of behaviour (and continuity is one of the marks of permanence). If this is so, M ichotte’s results do not take us very far; they am ount to no more than we could discover by means

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of reflection on the concepts involved. This is not surprising if, as I say, the meaning of words like ‘real’ can be given only negatively by reference to words like ‘unreal’. M ichotte has to take for granted a certain application of the concept of ‘unreality’, as if there were no problem with regard to the criteria for saying th a t a thing is unreal. I t is in fact very noticeable how limited is his conception of unreality. Most of his instances are two-dimensional drawings or projections of three-dimensional objects. I t m ight indeed be said th a t we should not norm ally say th a t a two-dimensional drawing of a cube looks unreal; nor should we normally say this of the cinema film, however much theorists may talk of efforts to ‘complete the illusion’. The tru th is that, on M ichotte’s account, to say th a t we have the impression of a thing’s reality is to say th a t we take it for a solid object; it appears to us to be a solid object and not merely as i f it were one (the art of ‘tromple l’œil’ painting is different from th a t of ordinary representative painting). B ut nothing very significant can be said about the conditions under which we take something as a solid object, except th a t it looks solid; and it looks solid when it does not look the reverse. Hence it would perhaps be of greater advantage to investigate the conditions under which a thing looks unreal, so th a t we can say more definitely w hat is a t stake when we say th a t something is not like this, b u t real. Michotte, however, concludes, in the G estaltist manner, th a t our impressions of reality depend upon configurational factors; in effect, what this am ounts to is th a t our perception of something as possessing a certain configuration depends on its appearing to possess all the properties necessary to th a t

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configuration. Similar rem arks apply to his account of substantiality and permanence. As we have seen, Michotte associates being real and being three-dim ensional, so th a t to perceive something as real, i.e. threedimensional, we m ust perceive it as possessing those properties which make it three-dimensional, e.g. depth; bu t all th a t can be said in general about this is th a t the properties m ust be such th a t the object does not look two-dimensional. Similarly, to look substantial, an object m ust possess properties like permanence which serve to prevent it from looking insubstantial. So much for Michotte. In general one finds the same characteristics as those exhibited by Gestalt Theory— (1) the reliance upon the investigation of illusions, so as to shed light upon the configurational properties which act as necessary conditions for the perception of some other property, (2) the insistence th a t this perception is pure and innate, owing nothing to learning, and (3) the characteristics which have gone along with the use of the phenomenological method. In the case of Gibson there is the same emphasis upon the innateness of the determ inants of our visual impressions, b u t far less reliance upon the investigation of illusions, and for this very reason it may be doubted whether Gibson’s approach can really be called ‘phenomenological’. Y et there are aspects of his approach which might be so termed, and in any case his view rests ultim ately upon a development of an im portant rem ark of Koffka’s which I noted in Chapter 2. I shall discuss Gibson’s development of this rem ark below. In general, Gibson has asserted th a t the results claimed by experim entalists in the psychology

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of perception have depended too much on work carried ou t in artificial laboratory situations. N ot enough regard has been paid to n atural and real-life perception (and he adduces evidence of the perception of pilots flying and landing aircraft). If we did attend to such real-life contexts for perception, he says, we should be more impressed by the extent to which people agree in how they see the world, than psychologists have generally been. Such agreement, he thinks, m ust be due to th e conditions of stim ulation, and he proposes in consequence to examine them. The outcome is a theory of some interest despite its dependence upon a fundam ental mistake. I t m ay be remembered th a t in discussing the answers to the question ‘W hy do things look as they do?’ Koffka said of the view th a t it is because the proximal stim uli are w hat they are, th a t it is certainly true on its broadest interpretation. He implies th a t on his view th e constancy hypothesis would be true only on the broadest interpretation, i.e. an interpretation not generally given to it. I think th a t Koffka’s notion of the broadest interpretation is one which would bring in a reference to sensory organization, bu t there are suggestions of another point of view, and these Gibson takes up. Gibson claims (footnote to page 62) to be reinstating the traditional constancy hypothesis on a broader basis. We perceive things as possessing the shapes and forms th a t they do because, he claims, a correlate of them is there in the process of stim ulation. Gibson does not deny th a t learning plays a p art in determ ining how we see things (although he does not devote m uch space to a consideration of this), for he recognizes th a t we may have to learn to identify

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things, and learn w hat things mean for us and for others. B ut with regard to the basic properties which constitute an object’s form, whether we see them correctly or incorrectly, he, like the Gestaltists, considers th a t experience plays no part; our perception of them is a function of stim ulation. He first draws a distinction between w hat he calls the Visual world’ and w hat he calls the Visual field’. The former is the world as we see it. I t is unbounded and stable, it is th a t in which ‘solid objects look solid, square objects look square, horizontal objects look horizontal, and the book across the room looks as big as the book lying in front of you’ (page 26). The visual field, on the other hand, is what we see when we take up a different attitude towards things, so th a t we see it ‘as if it consisted of areas or patches of colored surface, divided up by contours’. Gibson gives hints as to how we m ay come to see it in this way. I t is, he says an introspective or analytic phenomenon which one gets when one tries to see things in perspective and as the painter sees them. The visual field differs from the visual world in being, for example, bounded, unstable, lacking in depth and subject to deformation when we move. In general, he claims th a t this distinction is a substitute for the traditional distinction between sensation and perception. The visual field is a close correlate of the pattern of retinal stim ulation which occurs when we look a t things, and, he claims, those who m aintained the constancy hypothesis were, in fact, m aintaining a theory about the visual field. W hat Gibson claims to do is to produce a theory about perception of the visual world, by showing th a t it too has its correlates in retinal stim ulation. In this respect his

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view is novel. He calls his theory a ‘psycho-physical theory of perception’, by which he means th a t the properties of the percept correspond in some way to the properties of the stimulus, but not necessarily in being copies of the latter. Gibson’s approach might well be said to be phenomenological because of his interest in discovering the degree of correlation between the visual world and the visual field. For his approach involves a consideration, not only of w hat things are actually like, bu t also of how they look when we take up a special attitu d e towards them . I t is his interest in the visual field th a t stam ps his approach as phenomenological. On the other hand he himself describes as phenomenological our attitu d e towards the visual world, and in doing so he shows his agreement with the general point of view adopted by the Gestaltists. I t is probable th a t his agreem ent with the Gestaltists over the notion of ‘phenomenology’ contributes to the fact th a t he draws the conclusion th a t when we assume an ordinary, unsophisticated point of view with regard to w hat we see, we are having a pure, unlearned perceptual experience. In another respect too his view is very like th a t of the G estaltists, for he seems to assume the same model of retinal stim ulation ->eortieal excitation -^perceptual experience. Perception is for him the final experience which is the last link in a causal chain. He no longer makes a distinction between sensation and perception because he assimilates the latter to the former. Gibson does not commit himself explicitly to this view, but such a view seems to be involved in much of w hat he says, and his brief account of the physical basis of perception presupposes it. On the whole he confines

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himself to the assertion th a t he is concerned to find the correlates of the properties of the stim ulus-pattern in how we perceive things. Nevertheless his analogy with psycho-physics and his description of his theory as psycho-physical is suggestive of the more specific point of view. For it implies th a t whether or not the connection between stimulus and perception is strictly causal (and this is the natural point of view to take w ith regard to w hat he says), there is a one-one correlation between them such th a t the former is a sufficient condition of the latter. In my discussion of the similar position adopted by the Gestaltists, I showed th a t the most th a t could be asserted in this context is th a t the stimulus is a necessary condition of our perception of something, and th a t it is a m istake to consider perceiving as if it were the having of impressions, sensations or visual experiences of this kind. The same considerations apply to Gibson’s theory, and they account for his preference for the view th a t so much of w hat we see and how we see it is unlearned. Nevertheless, if the properties of the stim uli are taken as necessary conditions for our perception of things, Gibson’s account is extremely interesting. W hat he may be taken as asserting is not, as he thinks, th a t the way in which we see the structure of things is always determined and determined only by the properties of the stimuli, b u t th a t if we are to perceive the structure of things a t all, some correlate of them m ust be there in the stimuli. This is im portant in a great number of respects, and especially perhaps in connection w ith depth perception. I t was a common nineteenth-century belief th a t our perception of depth is learned, and th a t the retinal image has no correlates

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of depth (the view has its origins, I think, in Berkeley). Now it seems true th a t we learn to perceive how far things are from us (Gibson sometimes seems to deny this, although a t other times he seems only to be denying th a t we learn to perceive depth a t all); very young children have often no idea of how far from them things are. Y et if there were no correlate of depth in the stim ulus-pattern we should never come to see things as distant from us a t all. Gibson m ay be taken as saying, either on the score of geometrical optics or on the score of the phenomenology of the visual field (taken as a copy of the pattern of stim ulation) th a t the nineteenth-century view cannot be true. The m atter could be argued on either score and I think th a t Gibson does so. On the one hand, m any of his drawings and photographs are designed to get us to see w hat the visual field is like when we see things a t varying distances from us, and I think th a t he has noticed something here th a t has not generally been noticed. On the other hand, he claims to be offering w hat he calls a ‘ground theory5 as opposed to the traditional ‘air theory5. The latter treated objects as if they were isolated in em pty space, so having only air a t the back of them . This would also be a fair picture of the point of view of geometrical optics, the point of which is largely to consider the geometrical projection upon the eye of the objects seen, w ithout considering their background. Gibson now gives consideration to this background, points out th a t objects are on a ground which stretches from us to them and beyond them. The geometrical projection of this ground with the objects upon it corresponds to the structure of the visual field, so th a t the visual field and the retinal image coincide.

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Gibson detects within the retinal image certain ‘gradients’, corresponding to similar gradients within the visual field. In particular there is a gradient of texture. W hen we are looking a t a ploughed field the projection of the furrows upon our retinae is such th a t the projection of the nearer furrows on the bottom of the retina has a coarser texture than has th a t of the more distant furrows on the top of the retina. Analogously the visual field has a gradient of texture from bottom to top corresponding to the gradient in the retinal image. Gibson has given in his book a wealth of drawings and photographs to illustrate this point. There is a gradient of texture corresponding both to the objects seen and to the spaces between them. Moreover there m ay be changes or breaks in the gradient of texture and these correspond to w hat are perceived as corners or steps. Gibson claims th a t because these gradients are found in the stim ulus-pattern the stim ulus itself is adequate for perception of depth. He has investigated various gradients of this kind, including motion-gradients corresponding to characteristic deformations of the visual field when we ourselves are moving. There is, of course, an additional complexity in the fact th a t we have two eyes. Gibson thinks th a t most of the traditional cues to depth can be considered as ‘variables of the retinal image’. Thus the retinal image which corresponds to the visual field already has properties which, whilst not corresponding exactly to those of the visual world, have some correlation with it. Gibson concludes th a t the existence of gradients in the retinal image means th a t there is provided in stim ulation a correlation w ith the visual world sufficient for our perception of it. In

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all this, he distinguishes between the anatom ical p a ttern of excitation on the retina, the fact th a t certain nerve-cells are stim ulated, and, on the other hand, the ordinal pattern of stim ulation. Such an ordinal pattern is provided by the gradients, where it is not which particular nerve-cells are excited th a t m atters, but w hat formal properties the pattern of excitation possesses. An ordinal pattern is provided either by the simultaneous excitation of nerve-cells in a certain order, or by the successive excitation of nerve-cells, as m ust be the case when either the objects which we perceive or we ourselves move. In the latter case we still think of ourselves as perceiving objects of identical form in spite of there being successive deformations of the visual field. Gibson here makes extensive use of data from investigations into w hat people see when flying. We perceive a stable visual world, despite deformations of the visual field, because there is a constant ordinal pattern of stim ulation. The analysis of such patterns would, Gibson says, require complicated m athem atics bu t there is no reason why it should not be carried out, A similar approach is made to the constancies. Gibson here takes a view like th a t of Koffka, th a t there is, for example, an invariant relation between perceived size and perceived distance for a given retinal image. There is, as he says, ‘no such thing as an impression of size apart from an impression of distance’ (page 176); and the impression of distance is afforded by the background. L ater (page 180) he says th a t w hat is really constant in the perception of the size of objects is scale. ‘The size of any particular object is given by the scale of the background at the point to which it is attached, and th a t is why its apparent size is linked to

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its apparent distance’ (page 181). The perceived scale of w hat is seen is on his view a function of stim ulation, so th a t the same account is applicable in this case as in those previously dismissed. Similar explanations are given of the other constancies. Gibson gives an account of an interesting experim ent to show how general is the extent over which size-constancy holds. Subjects tended to estim ate more or less correctly the height of a stake, by comparing it w ith a series of standards, even when the stake was nearly half a mile away. Now, it is interesting in this case th a t Gibson himself uses the word ‘estim ate’ in his account of the experiment (page 186), and it is clear th at this is the natural word to use. B ut it ought not to be the natural word to use on Gibson’s account. For him, the size of the stake seen at a distance ought to have its correlates in the stim ulus-pattern, and ought to be seen autom atically w ithout question of estimation. He reports th a t only one of the subjects was aware of using any cues or making any inferences in estim ating the size of the stake. B ut such awareness would not be necessary. There are m any skills which we perform w ithout being aware of how we do so and w ithout using any conscious reasoning in the process. The fact th a t no inferences were made does not preclude the employment of skills acquired through experience. Gibson, however, claims, ‘The objectivity of experience is not a paradox of philosophy b u t a fact of stim ulation. We do not have to learn th a t things are external, solid, stable, rigid and spaced about the environment, for these qualities m ay be traced to retinal images or to reciprocal visual-postural processes’ (page 186). The notion th a t objectivity (by which he means,

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I take it, the correctness of our perceptions) is a fact of stim ulation is, to say the least of it, extremely odd. Moreover it becomes very difficult to see how we could, if this were true, make mistakes about w hat we perceive. I t is no doubt true th a t stimuli for perception m ust, as a necessary condition of perceiving, possess properties corresponding in some way to the properties of things, b u t it is not true th a t this is a sufficient condition of perceiving the world as we do. Sometimes, to p u t the m atter in a bald fashion, we see things in certain ways because we wish to do so, even when we are concerned with the spatial properties of things. (This is a point which has been emphasized by the adherents of the so-called ‘new look5 view of perception; see for example B runer’s contribution to Perception: A n Approach to Personality, ed. Blake and Ramsey.) Gibson adm its th a t where there is question of identification, there m ust experience play a part, but he restricts identification to features of the world other than those which are formal or spatial. B ut identification plays a p art in these latter cases too; we have to identify things as being of a certain shape, size, etc. In respect of these features, Gibson’s theory is the trad itional causal theory of perception which has been held by m any philosophers, and in which w hat we see is said to be caused by things (with consequent difficulties as to how we ever know about things a t all, if this be so). As H. H. Price pointed out in a review (Mind, Vol. L X II, No. 247, page 410), Gibson looks a t the visual world, as well as the visual field, as a product of the nervous system. T hat is to say th a t the visual world is for him a phenomenal world, inasmuch as it is the

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end-product of stim ulation. The causal theory of perception is m eant to guarantee the correctness of our perceptions; for if our perceptions are caused by w hat we perceive there is no room for m istake on our part. The theory fails because where there is no room for error there is no place for talk of correctness either. If our perceptions are caused there is no room for talk either of correctness or of error. In Gibson’s case, the philosophical causal theory, enshrined in the model of perception as the end-product of a process of stim ulation, is imposed upon a praiseworthy and respectable physiological causal theory. In the latter it is shown th a t the nervous excitations set up by stim ulation have formal properties which are a correlate of those possessed by the sources of the stimuli. The philosophical theory, which provides a conceptual model (and a mistaken one) for perception ought to be carefully distinguished from any physiological theory about the processes underlying perception. Gibson’s version of the latter is interesting and useful. B ut it is a theory of perception only in the sense th a t it indicates some of the necessary conditions of perception. There are other necessary conditions also, b u t of these Gibson has said nothing, although other psychologists have had much to say about them . The questions ‘W hy do we see things correctly? How is objectivity possible?’ are not to be answered merely by appeal to the facts of stim ulation—not only because illusions occur, bu t also because babies, for whom, presumably, the stim ulation exists, do not initially see things correctly. They have not yet learnt to do so, they have not yet developed the necessary skills and techniques. I showed in the second chapter th at,

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in the logic of the case, the type of explanation which is required here is one which demands reference to skills or abilities. Like Koffka, Gibson asks the blanketquestion ‘W hy do things look as they do?5 and like him also, he expects a single answer. I t is not surprising th a t his answer is unsatisfactory.

CHAPTER

SIX

FUNCTIONALISM

I

H A V E entitled this chapter ‘Functionalism ’, not because I think th a t all those psychologists whom I wish to discuss would be willing to answer to th a t title, but because I think th a t it is a convenient way of indicating w hat is common to them . (Koffka once claimed th a t G estalt Psychology had something in common with functionalism (see Ellis, op. cit., page 377), b u t this is not so in the sense in which I shall use the term .) The psychologists so far considered have tended to treat perception as a more or less passive affair. Those whom I wish to consider now are more inclined to treat it as a m ental function, and thus take a more active view of it. They have also tended to stress the role played by learning in the determ ination of w hat we see. Indeed, within the general movement, there has been an emphasis upon the heterogeneity of the factors determining how we see things, including reference to the p art played by needs and motives. Psychoanalysis has had its influence here in forming w hat has been called the ‘new look’ approach to perception. I t is only necessary to m ention the work carried out by Bruner and others in this respect (see, for example, Blake and Ramsey, op. cit., and Vernon, op. cit., 94

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Chapter 10). Those whom I have selected for consideration (and I might, perhaps, have selected others) are theoretically interesting, and reveal also the philosophical dangers involved in this approach to perception, in which it is considered th a t in perceiving we are doing something. Such a view, as I hope to show, covers an im portant tru th , but it is also liable to lead to paradox. In general, functionalism can be considered as a reaction against Gestalt Theory. A typical instance of this reaction is provided by Hebb in his book The Organization o f Behaviour. Hebb does not make clear w hat he takes perception to be, b u t he makes a distinction between three properties or features of the objects of perception (pages 19 ft.). These are (1) a primitive, sensorily determined unity, (2) a non-sensory unity, affected by experience, (3) the identity (also affected by experience) of a perceived figure. The distinction between (1) and (2) rests upon the fact th at, as W ertheimer indicated (on my interpretation of W ertheim er’s findings), there are some figures which it is natural for anyone to see as figures, whereas in the case of others a special attitude or experience may be required. Hebb agrees with the Gestaltist position as regards the innateness of the perception of form in the case of (1) alone. Under (1) too he refers to the figure-ground hypothesis, bu t apparently treats it as an empirical tru th and not, as I have done, as a logical truth, given th a t we are to see figures a t all. To talk of a figure as being sensorily determined, however, suggests th a t the perception of it is a mere product of stim ulation, and this involves a conceptual m istake. To say th a t it is natural to see such figures as figures does not preclude the possibility of not doing

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so. To be said to perceive a t all we m ust be aware of unitary things, b u t w hat is to count as a thing is not so far determined. W hat is to count as a thing is determined in p art by w hat we are (our needs, etc.), and in p art by w hat the world is like (the fact th at, for example, it is heterogeneous); and one of these aspects may be given greater emphasis than the other. N either aspect, however, can be excluded altogether. When he deals with (3) Hebb is on firmer ground. He concludes on the basis of Yon Senden’s study of case histories of patients operated upon for congenital cataract, th a t we learn to discriminate forms and th a t eye-movements play a big part in this. (Hebb puts this by saying th a t we learn to see things, e.g. triangles. This sounds odd, for it suggests th a t seeing is something which we have to learn to do in general; in fact w hat he means is th a t we have to learn to see triangles as triangles.) The evidence provided by Von Senden is dubious, as the case histories are highly interpreted, and the difficulty with regard to such cases (which also arises with regard to the evidence provided by Riesen’s work with chimpanzees brought up in the dark from birth and then brought into the light) is th a t a way of dealing with the world independently of vision is built up during blindness, and this inhibits the subsequent use of vision. There is, however, little need to have recourse to such evidence; it is clear th a t discrimination, identification and classification go hand in hand, and if learning is required for one it is required for all. We are not born with the ability to identify figures as, for example, triangles, although we may be born with a capacity for learning to do so; for identification presupposes previous classification, and this clearly

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requires experience. In the case of animals where this does not seem to be the case, we hesitate to talk of identification or perception a t all. Hebb goes on to construct a neurological theory, in term s of which the necessary discrimination and classification m ay be carried out. An analogous theory, perhaps less strictly neurological, is provided by Hayek in his book The Sensory Order. Hayek himself comments on the similarities and rem arks th a t by very reason of the fact th a t his version is less explicitly neurological, it may bring out the general principles more clearly. I propose to follow H ayek in this and consider his view for its general theoretical and philosophical implications. I think th a t my conclusions with regard to his theory would in general apply also to H ebb’s. Hayek states th a t the thesis of his book was conceived when he was a student in about 1919 and 1920, and th a t it consisted of a development of and a reaction from the work of E rnst Maeh. I think th a t some of the book is still tied to the older tradition, especially in its use of the term ‘sensory’, b u t I propose to ignore such features and take the book a t its face value. Hayek says, rightly I think, th a t psychology m ust concern itself with cases where w hat we claim to see does not correspond to what is actually to be seen; th a t is to say, it m ust proceed by a study of illusions. His general concern is to show th a t the structure of the phenomenal environment, how we see things, corresponds to the structure of events in the organism which perceives it, but not always to the structure of the world as it actually is. The latter, he thinks, is the world revealed by physics. In this he has something in common with

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Gibson, but his working-out of the idea reveals a definite cleavage. He starts from what has become known as the equipotentiality of stimuli, th at is, from the fact th at we may perceive something as a circle despite the fact th at the actual nerve-fibres stimulated may differ from time to time. Gibson, it will be remembered, explained this in terms of an ordinal pattern of stimulation. Hayek does something similar, but instead of concluding th at the perception of a circle is merely the end-product of such ordinal stimulation, he concludes th at the seeing of the circle as a circle involves classification. Whenever we attribute properties to things we are classifying them. Like Hebb, H ayek then goes on to suggest a mechanism for such classification. Roughly, the organism acts like a sorting-machine, in which sorting is carried out on the basis of the relative frequency with which an impulse set up in the nervous system occurs together with other impulses or with their ‘following’. (By the latter Hayek means something like tracepatterns set up by previous sorting processes, so as to provide classification in term s of the succession of events in time.) This account m ust be viewed as one concerning the necessary conditions of our perception of things. Hayek, however, does not present his theory in this light, and he sometimes uses terminology which is inconsistent with this point of view. He talks, for instance, albeit with some hesitation, of nervous processes as representative of or symbols of other processes (see e.g. section 3.50). To talk in this way is to confuse an account of the necessary conditions of perception, an account of the mechanism of classification, with one concerning techniques as employed by us. We take

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things as symbols of other things in performing m any operations, and this involves our having carried out some classification. B ut the notion of a ‘symbol* is completely misplaced if applied to a mechanism. The ways in which Hayek views classification as being carried on become more and more complicated, but it is to be noted th a t relative frequency is their only basis. Hayek puts this by saying th a t classification is a ‘process which creates5the distinctions which we make between things (section 2.32). This is an unfortunate way of putting the m atter. The distinctions which we make depend upon the functioning of the nervous system, but this is not incompatible with saying th a t we recognize them. We recognize a distinction when the nervous system has responded differentially to stimuli on the basis of, inter alia, their relative frequency. The attribution of properties to things depends partly on us, in what we choose to put together, and partly on things, in what can be classed together. The fact th a t the former is the case as well as the latter does not mean th a t we create the relevant distinctions, but merely th a t when we talk of recognizing a distinction or sim ilarity both these aspects are involved. In other words, to perceive a thing as possessing a certain property is not to classify it, although classification m ust have gone on, conditioned possibly by a nervous system working as H ayek suggests. I t is clear th a t we are not classifying when we are perceiving. When we classify objects we do so on the basis of similarities which we perceive. If perceiving were classifying, we should perceive things as possessing certain properties on the basis of a perception of similarities. B ut seeing th a t this latter perception would be consti-

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tu ted by classification, we could not achieve this except on the basis of a further perception. And so this view would generate an infinite regress, confining itself to classification and never coming to grips w ith w hat is classified. The regress would be endless unless we were to come to some form of perception which is absolute, in not involving classification. The postulation of such a form of perception, however, Hayek wishes to avoid. On the other hand he does think th a t there m ust be a basis for the classification involved in the m ost elementary perception. Hence he is led to talk of ‘pre-sensory experience’, some form of experience, not perceptual, which is the basis of our actual perceptions. He is hesita n t about this (sections 5.7 ff.) and suggests th a t it m ight be better to talk instead of a ‘linkage’, implying only physiological processes. B ut this itself illustrates a vacillation between the view th a t we are classifying in perception, and the view th a t the nervous system is classifying, in responding differentially to stimuli. I t is im portant to see th a t these two views are not the same, although the latter may furnish necessary conditions for the former. In fact it is the stimulus which is absolute for Hayek, b u t this we cannot be said to perceive. We perceive things on the basis of the nervous system ’s differential responses to patterns of stimuli. Most of the time Hayek says th a t it is stimuli th a t are classified, with the implication th a t this means only th a t the organism reacts differentially to them . B ut he tends also to use ‘classify’ in the ordinary sense, calling perception an ‘act of classification’ (cf. section 6.36), w ith paradoxical results. For if in perceiving we are classifying we cannot be classifying any of the things which we should

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ordinarily be said to perceive; yet we are not ordinarily aware of stimuli or of ourselves as classifying them . Moreover, the properties which we usually take ourselves as perceiving cannot on this view be said to belong to the objects which we perceive a t all. In section 6.37 H ayek says, ‘The qualities which we attribute to the experienced objects are strictly speaking not properties of th a t object a t all, but a set of relations by which our nervous system classifies them ___ ’. B ut the same should be said of the objects themselves on this account! Such a conclusion runs counter to common sense, and might with justification be labelled ‘m etaphysical’. There are further difficulties still. Not only is it the case th a t we are not ordinarily aware of stimuli, b u t it is also impossible to see how we could come to know about the stimuli a t all except by perception. H ayek takes it th a t physics tells us about objects qua providers of stim uli and thus tells us of the objective properties of things. This suggests th a t physics is free from the difficulties which are involved in the account of ordinary perception. B ut this is surely not so. Physics relies upon perception as much as anything else. I t m ay be th a t Hayek senses the difficulty here, for his final account of science is th a t it provides true knowledge by providing the most coherent account of the world. In other words the standard of tru th and objectivity is coherence, not correspondence with the facts. In general, then, H ayek’s account is th a t in perceiving we are classifying (or sometimes th a t our nervous system is classifying) stimuli on the basis of their relative frequency; th a t physics tell us of the objective

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properties of w hat we classify, b u t th a t the standard of objectivity is coherence. U ltim ately, to perceive something correctly is to classify it in a way which produces the m ost coherent system. (His metaphysics is thus th a t of Idealism.) This view of H ayek’s theory is consistent with passages in which he talks of distinctions being created not recognized, and with other passages too (cf. section 1.17). To some it may seem th a t these conclusions are to be accepted as following from the premisses. The tru th is th a t the premisses are wrong, involving a conceptual mistake. To perceive is not to classify, although a necessary condition of perceiving something in a certain way is th a t some kind of classification m ust have gone on. I t is possible to describe H ayek’s view of perception as the view th a t it is an interaction between ourselves and the object, w ith the consequent result th a t the object itself becomes unknowable—a kind of ‘ding an sich’. This sort of paradox always signals a conceptual mistake. The views of those who have called themselves ‘Transactionalists’, and who m aintain th a t perception is a transaction between ourselves and the world, have similar implications. The view which has been called ‘Transactionalism ’ is derived chiefly from the work of Adelbert Ames Jr. (although its philosophy stems from Dewey), and a collection of papers has been published in a provisional form under the title Human Behavior from the Transactional Point o f View edited by F. P. K ilpatrick. The psychologists in this group have carried out experiments which are in the main extremely ingenious; these experiments are generally devoted to the production of illusions of a complicated sort, with

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a view to the shedding of light on factors which play a p art in perception, and this is stated as deliberate policy in K ilpatrick’s introductory paper (op. cit., page 4). Typical of such experiments is Ames’ work with the rotating trapezoid. A window-frame of trapezoid shape (such as would be the projection of a window-frame seen at an angle), was constructed and shadows were painted on to it; it was then suspended so as to be rotated and it was arranged for it to be seen against a plain background. On rotation the trapezoid, generally taken by the subjects to be an ordinary window-frame, undergoes interesting changes in its appearance; moreover objects put on it behave in w hat are, prima facie, very unexpected ways. Ames sets out to show th a t these phenomena would be expected if the subjects adopted normal assumptions concerning what is there to be seen. The ingenuity of the investigations is remarkable, and they shed a great deal of light on the production of illusions. W hat is of present interest, however, is the conclusion drawn by the psychologists concerned. The general point of view can be seen from Kilpatrick’s introductory paper in the book. It begins in a way familiar from a consideration of Koffka’s question ‘Why do things look as they do?’. We are told th at if we look at a chair, and are asked where all its ‘characteristics and qualities come from’, the answer cannot be that they are properties of the thing at which we are looking. This can be indicated by constructing situations in which we seem to see a chair but are not actually doing so. These facts, it is said, ‘cannot be reconciled with any notion th at what you see is in objects themselves’ (page 2). The same sort of con-

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sidérations affect the view th a t ‘visual perceptions are not determined by objects, b u t instead are determined by—can be derived from—the physiological stimuluspatterns th a t result from the impingement of light rays on the organism5. These stim ulus-patterns often undergo a distortion which is not reflected in the way in which we see things. So both of these answers are rejected. K ilpatrick’s own answer is, ‘Since w hat is perceived cannot be derived from either the immediate outside world or the immediate physiological stimuluspattern, it would seem reasonable to suppose th a t the explanation m ight profitably be sought in the realm of past events5 (page 4). L ater (page 8) we are told th a t the organism, ‘always forced to “ choose55 among the unlim ited num ber of possibilities which can be related to a given retinal pattern, calls upon its previous experiences and “assumes55 th a t w hat has been most probable in the past is most probable in the immediate occasion5. In fact we see constructs, built up through experience (page 14), and Ames adds to his account of the rotating trapezoid th a t ‘w hat we are aware of when we look a t a rotating object is not a disclosure of what is “objectively55 taking place, b ut is a prognosis whose nature is related to assumptions arrived a t from prior experience5 (page 65). Thus perception is a transaction in which the perceiver brings to bear on w hat is offered by the environm ent his past experience. W hy is the answer to the initial question so different from th a t of Koffka? I t is clear th a t the reason lies in the conceptual model adopted for perception. For Koffka, as we have seen, perception was the experience which is the end-product of retinal stim ulation plus cortical organization. For the Transaetionalists it

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is something very different. In one sense it is not an experience a t all; it is something much more like a form of response to the environment, in the shape of an interpretation of it. On page 89 of the book K ilpatrick says, ‘By perception, then, is m eant th a t p art of the transactional process which is an im plicit awareness of the probable significance for action of present impingements from the environment based on assumptions related to the same or similar impingements from the environm ent’. From Gestalt Theory to Transactionalism the wheel has gone full circle, and now everything is put down to experience. Y et there are still muddles in w hat is said. W hy should it be concluded from the fact th a t we are sometimes subject to illusions th a t we do not see objects themselves a t all? Surely the true conclusion is th a t sometimes we do and sometimes we only seem to do so. Again, when K ilpatrick says th a t w hat is perceived cannot be derived either from things or from stimuli, he seems to be assuming th a t the possession of certain properties by things or stimuli m ight be considered as a sufficient condition of our perception of things. B ut this, as we have seen, is not so; a t the most it is a necessary condition. The same thing may be said of K ilpatrick’s own explanation. His words suggest th a t past experience is to be a sufficient condition of how we perceive things, and the reference to ‘constructs, built up through experience’ reinforces this suggestion. B ut experience, like the other factors, can be no more than a necessary condition. W hat then of perception as a transaction? In perceiving something are we interpreting impingements from the environm ent on the basis of past experience?

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Much the same considerations are relevant here as were applicable to the view of perception as classification. In some cases when we perceive an object in a certain way, we may have interpreted w hat we see of the object in this way; not th a t we are interpreting when we perceive, bu t th a t interpretation m ust have gone on a t some time. To generalize this, however, is to make all cases of perception like those in which talk of ‘seeing-as’ is appropriate, and this is impossible, if only because ‘see-as’ gets its meaning only by contrast w ith ‘see’. This is to say th a t if it were not sometimes appropriate to say th a t we perceive objects, it would never make sense to talk of how we perceive them . As with the view of perception as classification, the view th a t it is a transaction makes it impossible for us to know anything about objects a t all. Thus the very basis of the theory th a t in perceiving we go through a transaction with objects in the environment is cut away. Things become not objects of perception, b u t ‘things in themselves’ in the K antian sense. In other words, the Transactionalist point of view, despite its very laudable attem pt to show th a t experience contributes much to our manner of seeing objects, fails to deal adequately with the conceptual question ‘W hat is perception?’. W hat the Transactionalists have to offer is a theory about ‘seeing-as’, not one about perception in general. There are deficiencies even in the presentation of this, as was the case with H ayek’s theory. I t would not be true, for example, to say th a t when we perceive something in a certain way, the organism ‘chooses’ in the light of assumptions which of the possibilities is relevant to a given retinal pattern. On the one hand, the organism cannot be said to choose a t all (K ilpatrick’s

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quotation marks indicate some sensitivity to this point); it is we who choose. On the other hand, whilst the organism responds on the basis of retinal stimuli, we do not choose on this basis, for, in the ordinary way, we have no knowledge of them . In any case, if, as I have said, perception involves the exercise of a skill, a word like ‘choose5implies too much self-consciousness. The Transactionalist approach emphasizes the important tru th th a t both the nature of the stim uli and our own experience and assumptions are factors in determining how we see things, in the sense th a t they are necessary conditions of our perceiving things in a certain way. B ut the reception of stim uli and the response to them are not constituent parts of perception. Nor it it true th a t we do not see things a t all directly, but are only in the position of making a prognosis, for this is to make things into ‘things in them selves5. Functionalism has the great m erit of taking a more active view of perceiving, and of freeing psychology from the model of perception as the experience which is the end-product of a process of stim ulation. T hat it does not deal with every problem is hardly surprising when it is considered th a t experiments are performed and theories constructed without any clarification of the concept of perception first being arrived at. I t is noticeable to what extent the end of much recent work, rather than the beginning, seems to be some kind of conceptual clarification. H ilgard’s rem ark (in his contribution to Blake and Ramsey, op. cit.) th a t perception is an achievement is a case in point. As a conceptu al statem ent this rem ark has some m erit. The verb ‘to perceive5 has something in common with w hat

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Ryle, in The Concept o f M ind, has called ‘achievement verbs5 (e.g. ‘win5 and ‘succeed5). An exam ination of other perceptual verbs, such as ‘see-as5, on the other hand, would be necessary for a full clarification of the concept of ‘perception5. Y et it m ight be said with justice th a t a conceptual statem ent such as th a t of Hilgard is a little result for all the experimental and theoretical work th a t has gone before. Conceptual clarification should come first. The value of psychological research in this field, and perhaps in others, lies in the details, not in the general picture. Something m ight be said, although I shall say little here, of another sort of puzzle th a t Functionalism seems to produce. I t is the puzzle concerning the status of the person who does the perceiving. W hat is a person apart from what he does and the factors which determine w hat he does? In the book Perception and Personality, a Symposium, edited by Bruner and Kreeh, for example, there are two articles which express this puzzle. The first by Klein and Schlesinger is entitled ‘Where is the perceiver in perceptual theory?5 and the second by Hochberg and Gleitman refers to the dangers of assuming a pure-ego which are said to be implicit in the so-called ‘new-look5approach to perception. I t is clear th a t both of these psychologists (and the same is true of others) have found it difficult to know w hat to say about the subjects of perceptual verbs. I can say here only th a t this puzzle seems to arise from a lack of insight into the logical implications of Functionalism. If you once begin to look on perception as a kind of activity, you cannot a t the same tim e take up w hat m ight be called a ‘structuralist’ approach.

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You cannot, th a t is, in the same context, both talk of a person as being active in certain ways so th a t w hat he does m ay be influenced by, for example, his motives, and also ask w hat the person is apart from his motives and the like. The attem pt to say what a person does and under w hat circumstances, and the attem pt, so to speak, to uncover the person by stripping off his m anifestations involve quite different approaches. The danger of assuming a pure-ego arises only when we are tem pted to think th a t a person is really quite different from his manifestations. B ut there is no danger in this direction merely in the fact th a t in order to talk of perceiving something we norm ally employ active verbs, such as ‘see5, with referring-expressions as their subjects. The use of referring-expressions does not commit one to any view as to w hat a person ‘really is5, and there is no such reason why Functionalists should become involved in such questions. I t is the person who perceives things, not a pure-ego.

CHAPTER

SEVEN

CONCLUSION H E N we say th a t someone sees something we do not imply merely th a t he has certain experiences (even if such experiences are presupposed). We imply also th a t he knows something about the object and we indicate the source of his knowledge (i.e. the use of his senses). The uses of csee-as’, when applied to another person (and first-person uses are different again) are more complicated. (1) We may, as is the case with illusions, imply th a t the person is disposed to make a claim to knowledge of the object, bu t refuse to allow the possibility of such a claim being adm itted. We might then describe his claim by talking of how it looks to him. There is of course the possibility th a t a person may see something in a certain way, whilst being quite aware th a t it is not like this really. In such a case we might still talk of how the object looks to him. In either case the person is certainly disposed to describe the object in the way which we call ‘illusory’, even if in the second case his knowledge runs counter to his disposition. (2) We may imply th a t the person is disposed to make a claim to knowledge of the object, but refuse to allow this as the only possible claim, as is the case with

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ambiguous figures. (The same qualification needs to be added as in case (1). Where there is oscillation between the aspects of the figure seen, and we say ‘Now he sees it as X . . . now as Y ’, we mean th a t on each occasion the person would be disposed to give, as the description of the figure, a description of one of its aspects, even though he knew th a t more than one description was possible.) (3) We m ay imply th a t the person is disposed to make a claim to knowledge of the object, and we may allow the claim, but a t the same tim e imply th a t such a claim was not expected. In all these cases we also indicate the basis of the claim, the fact th a t he has used his senses. I do not m aintain th a t the foregoing is a complete analysis of the possible uses of ‘see-as’; it serves merely to distinguish three im portant uses and gives some account of them . There are, in ordinary language, other uses, b u t the ones which I have m entioned are the most im portant for the psychology of perception. The use of ‘see-as’, for example, in which we express doubt as to the identification of the object has little relevance to the psychology of perception. For, in order to acquire th e inform ation which he requires, the experimenter m ust be in the privileged position of knowing the identity of the object. I t is perhaps true also th a t the third use of ‘see-as’ which I have mentioned is of less im portance th an the others, because our normal expectations are th a t people will see things correctly. Correctness and norm ality have a connection in th a t we expect people to exercise the skills which it is possible for them to exercise, and the existence of these skills presupposes th a t standards of correctness are applicable.

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(Where it is possible to talk of a skill, there m ust it also be possible in principle to say whether it has been exercised correctly.) I t would be paradoxical if everyone, or even most people, were to behave in an incorrect manner. The use of ‘see-as’ which is of the greatest importance is clearly use (1), and it is for this reason th a t so much stress has been laid on illusions by the psychologists. The study of these can bring to light factors as a result of which we may go wrong, and conversely those on which we m ust rely if we are to be right. In the second chapter I discussed the types of explanation which are applicable in the various cases, and I stressed the asymmetry which exists between them. This asym m etry is due to differences in the uses of the concept of ‘perception’. In my chapter on Gestalt Theory I showed th a t th a t theory was m eant to cover cases which are intrinsically different, and indeed th a t its exponents introduced philosophical issues in scientific guise. Those who have followed or developed Gestalt Theory have produced theories with much the same characteristics, even if they have differed in their emphasis. Thus Michotte has concentrated on illusions, Gibson on veridical perception. W hat unites them and Gestalt Theory is in particular the adoption of one conceptual model for perception— a model in which perception is merely the experience which is the end-product of a process of stim ulation and neural excitation. They have not all explicitly declared for such a model, but their theories have generally seemed to presuppose it. Moreover the adoption of the phenomenological m ethod reinforced the adoption of this model. Most of these psychologists have allowed some role to experience and learning, but

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they have tended to depreciate this; for the implication is th a t they are concerned w ith the pure experience, before it becomes overladen with the effects of learning. Such pure experiences are supposed to be discoverable by an examination of w hat is the case with naïve subjects. The supposition is th a t absolute naivety and lack of sophistication is possible, and th a t in this case w hat is really discovered is the pure experience which is the end-product of stim ulation and neural excitation. I have tried to show th a t this claim is wrong, and th a t the phenomenological approach is not in fact concerned with the discovery of the pure experience, b u t w ith how things look to someone who is unsophisticated in the sense th a t he does not know w hat they are really like. B ut this naivety is relative only. W ith Functionalism we moved to different ground in the sense th a t a different model came under consideration. The Functionalists have rightly em phasized how much interpretation, classification and the like have to do with perception, a fact which is implicit in our use of the phrase ‘see-as5. They have not usually expressed correctly the relations between perception and interpretation and the like, for in general they have tended to identify the concepts. I have brought forward argum ents to show th a t such identification is not possible. I t is nevertheless true th a t perceiving something as possessing certain characteristics presupposes interpretation or classification, ju st as perceiving something in general presupposes a skill in identifying things. Interpretation, classification and identification all demand, by and large, experience for their exercise. W hat of the future? I have urged the need for conceptual clarification before plunging into theory-

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construction. Otherwise all th a t will emerge may be a painful elucidation of the concepts involved, instead of a genuine theory; or a theory will emerge which, by playing upon ambiguous terms, explicitly prevents such elucidation. I t is not likely or desirable th a t the practice of psychologists in their experimental procedures should change, for it has long been obvious th a t the study of illusions is the best procedure in this field. I t has not always, however, been clear why this is so. I t is so, I m aintain, because in the investigation of perception we are fundam entally concerned with a skill and its break-down. I t is a skill in characterizing things the basis of which is provided by the fact th a t we have senseorgans. In general, most information is likely to be obtained concerning the exercise of a skill by studying the circumstances in which it tends to break down. Perception is no exception in this. We can study illusions either for their own sake, or for the light th a t they shed upon perceptual techniques. In studying the workings of the nervous system and the stim ulation made upon it, psychologists are studying only the necessary conditions of the exercise of perceptual skills. B ut there is no one sufficient condition of seeing something in a certain way. Even if other conditions are taken for granted, w hat is sufficient on any one occasion to make a person see a circle, for example, as an ellipse may nevertheless vary. The nature of skills is such th a t they can be performed under varying conditions. Something, however, may be said about the factors which tend to be sufficient to make people see things in a certain way. I t is difficult to see w hat theory can be constructed in these circumstances. At the present time psychologists

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have a tendency to go to neurology for their theories. I t m ust be stressed once again th a t such theories could be concerned only with some of the necessary conditions of perception, and not, as often seems to be supposed, w ith the sufficient conditions. B ut theories are m eant to explain laws, in th a t they are m eant to provide conditions sufficient for the laws to hold. I t is my thesis th a t there is no room for theories of this sort in the psychology of perception, and th a t such explanations as m ay be given are of quite a different sort. I t m ay be th a t some psychologists will feel th a t these criticisms are beside the point. I t may be held th a t it is sufficient for psychologists merely to investigate the connections between behaviour, m otivation, and certain features of the environment, w ithout making explicit reference to perception. N aturally enough this m ight be done, bu t whose task is it, in this case, to investigate perception? For, th a t there is room for inquiry in the case of perception I indicated in my first two chapters. I t would be a pity if psychologists were to initiate another movement akin to th a t of Behaviourism and give up talking about w hat is for one reason or another uncongenial to them . B ut as regards perception itself, it is the understanding of the concepts involved th a t has been lacking, not progress in the acquisition of detailed knowledge. Psychologists have, for example, acquired detailed knowledge of the causes of particular illusions. This has not been paralleled by an equally detailed understanding of the concept of ‘perception’. Contemporary ‘theories of perception’ are more often than not attem pts, only partially successful, to provide this understanding. They are not, and cannot be, genuine scientific theories.

B IB LIO G R A PH Y The following list of works is by no means meant to be exhaustive. I t includes only those works which I have found most useful. and R a m s e y , G. Y. (Ed.), Perception: A n Approach to Personality. New York: Ronald Press (1951). B o r i n g , E. G., Sensation and Perception in the History of Experimental Psychology. New York: D. Appleton-Century (1942). B r u n e r , J . S. and K r e c h , D. (Ed.), Perception and Personality, a Symposium. Duke U.P. (1950). E l l i s , W. D., A Source Book o f Gestalt Psychology. London: Kegan Paul (1938). G i b s o n , J. J., The Perception o f the Visual World. Boston: Houghton Mifflin (1950). H a y e k , F. A., The Sensory Order. London: Routledge and Kegan Paul. Chicago: Chicago U.P. (1952), H e b b , D. O., The Organization o f Behaviour. New York: Wiley (1949). K i l p a t r i c k , F. P. (Ed.), Human Behavior from the Transactional Point o f View. Hanover, N .H .: Institute for Associated Research (1953). K o f f k a , Κ. , Principles o f Gestalt Psychology. London: Kegan Paul (1935). Bl

ake

, R. R .

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Ko

hl er

, W.,

11?

Gestalt Psychology. London: G. Bell

(1929). The Place of Value in a World of Facts. New York: Liveright (1938). London: Kegan Paul. Dynamics in Psychology. London: Faber and Faber (1939). M i c h o t t e , A., La Perception de la Causalité. Louvain: Inst. Sup. de Philosophie (1946). R y l e , G., The Concept of Mind. London: Hutchinson (1949). (Vide esp. page 326.) V e r n o n , M. D., A Further Study of Visual Perception. C.U.P. (1952). W i t t g e n s t e i n , L., Philosophical Investigations. Oxford: Blackwell (1953). ( Vide esp. pages 194 f t) W o o d w o r t h , R. S., Experimental Psychology. New York: H olt (1938). (Many of these works contain extensive bibliographies. See especially Vernon, op. cit.)

IN D E X depth, perception of, 86-8 Descartes, R., 1, 43 discrimination, 4, 5, 96 Duneker, Κ. , 63

ambiguous figures, 25 ff. Ames, A. Jr., 102 ff. Aristotle, 89 association of ideas, 9 ff., 27 attention, 9 ff., 27

ego, pure, 108-9 Ehrenfels, C. von, 43 epistemology, 5, 22, 29, 37 equipotentiality of stimuli, 98 Exner, S., 49 experience, pure, 43, 46, 58-9, 74, 78, 113 explanation, scientific, 16 ff.

Bain, A., 38 Benary, W., 59, 63 Benussi, V., 42 Bergson, H., 41 Berkeley, G., 37, 39-40, 87 Bradley, F. H., 40-2 Brentano, F., 42 Brown, J. F., 64-5 Bruner, J. S., 91, 94, 116 causality, impressions of, 76 ff. causal theory of perception, 91-2 cinema, 49, 81 classification, 52, 96, 98 ff., 113 colour vision, 3 ff., 44 communication engineering, 25 conceptual inquiries, 6 ff., 79, 107-8 conceptual mistakes, 29, 58, 78-9, 92, 102 constancy hypothesis, 22, 33, 83 constancy phenomena, 33, 6573, 90

figure-ground hypothesis, 5557, 95 forces, internal and external, 53, 68, 70 framework, 57 ff., 66 Fuchs, W., 59, 63 functionalism, 41, 94 ff. gamma movement, 49 Gelb, A., 67-8 geometrical optics, 72, 87 gestalten, 44-45, 73 Gestalt Theory, 3, 4, 14, 22, 30, 33-4, 37 ff., 48-75, 77, 78, 82, 85, 94, 112 Gibson, J. J., 29, 82-93, 98, 112, 116 Gottschaldt, Κ. , 61-63, 74 gradients of stimulation, 88

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INDEX

Hartley, D., 39 Hayek, F. A. 97 ff., 116 Hebb, D. O., 95-7, 116 Heider, G. M., 59 Hering, E., 44 Hilgard, E. R., 107-8 Hochberg, J. E. and Gleitman, H., 108 Hume, D., 37-8, 76-9 Husserl, E., 42 ff. illusions (v. Muller-Lyer illussion), 16 ff., 30, 32, 49, 102-3, 110 impressions, 76-7 interpretation, 72, 106, 113 isomorphism, 50 James, W., 41 Kilpatrick, F. P., 102 ff., 116 Klein, G. S. and Schlesinger, H., 108 Koffka, Κ. , 22, 29-36, 52-3, 57, 61-3, 64-5, 66 ff., 82-3, 89, 93, 94, 104, 116 Kohler, W., 26, 43, 50, 53, 59-61, 74, 117 Korte, A., 52, 64 Lauenstein, O., 68 laws of perception, 11-16, 115 learning, 13, 19, 70-1, 83, 86, 113 Locke, J., 1, 23, 37 Mach, E., 97 Malebranche, N., 16, 40

119

Meinong, A., 42 metaphysics, 14, 22, 37, 102 Michotte, A., 76-82, 112, 117 Mill, James, 38 Mill, J. S., 38 models, conceptual, 19, 66, 85, 92, 104, 112-13 motives, 8, 94 movement, perception óf, 6365 Muller, J., 39 Muller-Lyer illusion, 11 ff., 18 ff., 23 naivety, 14, 24, 44, 46, 70, 113 nativism, 70-1, 82, 95 necessary and sufficient conditions, 72, 86, 92, 100, 105, 107,114-15 (cf. 8-10, 30-1) neurology, 19, 49-50, 97 (v. physiology) perspective, 33, 72 phenomenology, 14, 42-7, 58, 75, 77-8, 82, 85, 87, 112 phi-phenomenon, 48 ff., 64, 73 photographs, 65-6, 72 physics, 97, 101 physiology, 1, 2, 4, 5, 28, 92, 104 (v. neurology) Piaget, J., 78 prâgnanz, 53 ff. Price, H. H., 91 production school, 42-3 proximal stimuli, 32-3 psychoanalysis, 94 psychophysics, 85-6 purpose, impressions of, 76, 78

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reality, impressions of, 79 ff. Riesen, A., 96 Rubin, E., 55, 73 Ryle, G., 108, 117 Schiller, P. von, 63 seeing-as, 12, 96, 106, 108, 110 ff., 113 Senden, M. von, 96 sensationalism, 37 ff., 51 sensations, 2, 23, 34, 40-1, 51, 72 skill, 52, 69, 70, 71, 73, 90, 111-12, 114 sophistication, 14 ff., 19-20, 23-25 standards of correctness, 17 ff., 24 ff., I l l Stout, G. F., 41 structuralism, 108 subliminal perception, 9 ff.

substantiality, impressions of, 79 ff. tachistoscope, 9 Ternus, J., 63 theories, 10, 16 ff., 114 things in themselves, 102,106, 107 Thouless, R., 66 transactionalism, 102-9 Tudor-Hart, B., 59 visual field, 84 ff. visual world, 84 ff. Wertheimer, M., 45-6, 48-50, 55, 58, 62, 63, 73, 79 W ittgenstein, L., 21, 26, 117 Wulf, F., 54 Wundt, W., 43