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AN INVESTIQATION OF STUTTERING VIEWED AS LEARNED BEHAVIOR WITH SPECIAL REFERENCE TO EXPERIMENTAL EXTINCTION AND SPONTANEOUS RECOVERY
By E. LeRoi Jones
dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy* in the Department of Speech in the Graduate College of the State University of Iowa June 1950
ProQuest Number: 10991961
All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is d e p e n d e n t upon the quality of the copy subm itted. In the unlikely e v e n t that the a u thor did not send a c o m p le te m anuscript and there are missing pages, these will be noted. Also, if m aterial had to be rem oved, a n o te will ind ica te the deletion.
uest ProQuest 10991961 Published by ProQuest LLC(2018). C opyright of the Dissertation is held by the Author. All rights reserved. This work is protected against unauthorized copying under Title 17, United States C o d e M icroform Edition © ProQuest LLC. ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 4 8 1 0 6 - 1346
V\caVYl\ Sc.\£-N and 62.6 per cent, respectively.
With reference to Reading 1 of the first day, the adapta
tion was progressively increased in the first readings of the first five dayss
31.7 per cent the second day, 37-1 the third, 42.8 the fourth,
and 5^-7 per cent the fifth day.
On the sixth day, after the lapse of
ten days, the corresponding reduction in the first reading was only 36.7 per cent. Condition II In Condition II a different-250-word passage was read five times in succession on each of the seventh, aignth, ninth, end tenth days of the experiment.
The mean frequencies of stuttered words in all readings
of the four passages are presented in Table V. Between Reading 1 and Reading 5, on the seventh day, the mean was reduced from 47-75 words to
Table IV Percentage of Adaptation Computed From the First Reading in Condition I
r -e 3
r -r 5
1G-Day Interval 6
* R * first reading of first day
Table ? Mean Frequency of Stuttered Words in the Five Headings on Each of Four Days in Condition II
31 20.70, on the eighth day from 39.95 to 16.32, on the ninth day from 37.79 to 15*37, and on the tenth day from 40.33 to 15.67. The absolute decreases in means betiveen Readings 1 and 5 on the four days were 27.65, 23.63, 22.42, and 24.66, respectively.
Therefore, the reductions of
stuttering in all the passages were approximately the same. In Reading 5 on all four days, and particularly the last three days, the mean frequencies of stuttering were also roughly sirailar; 20.70 on the seventh day, 16*32 on the eighth, 15*37 on the ninth, and 15*67 on the tenth. There was a consistent tendency for the frequency of stuttering to be reduced in each successive reading of each different passage.
shown in Table V, on the seventh day the means for the five readings were 47*75, 32.90, 27.50, 23*00, and 20.70, the mean number of stuttered words decreasing with each successive re ding.
The same systeraatic decrease
in means was shnwn for the five readings on the eighth, the ninth, and the tenth days, when different content material vms read each day.
each day the largest decrease in stuttering occurred between Readings 1 and 2, and the decrease in means became progressively smaller in Reading© 3, 4, and 5* The decreases in mean words stuttered in the five readings of each day are shown graphically in Figure 2.
The shapes of the four
curves are ail very similar. All are negatively accelerated positive curves.
In each, a sharp decline occur© between readings 1 and 2,
after which each curve progressively levels off In the three last readings. Table VI shows the results of the test of significance applied to
U V s
Figure 2 Mean number of words stuttered in Condition XI (with new material)
Table VI Significance of Differences Between Mean Frequency of Words Stuttered in Readings 1 and 5 on Each of Four Days in Condition II
34 the differences between means in Readings 1 and 5 on each of the four days. The mean differences on the seventh, ninth, and tenth days were statistically significant at the 0.1 per cent level of confidence; that on the eighth day was significant beyond the 1.0 per cent level. The percentages of adaptation, with reference to the percentage of words stuttered in Reading 1 of the seventh day, appear in Table VII. The percentage of stuttered ^ords in Reading 1 of the eighth day was reduced only 15*4 per cent in comparison with Reading 1 of the seventh day.
The corresponding value for the ninth day was 20.0 per cent, and
14*& per cent for the tenth day.
The decrease in the frequency of
stuttering attained in any one day carried over only to a slight degree to Reading 1 of the following day when a different passage was read.
greatest adaptation in stuttering v>,as revealed in Reading 5 on the eighth, ninth, and tenth days, when the number of stuttered words was reduced from Reading 1 on the seventh day 65*4 per cent, 67.4 per cent, and 66.7 per cent, respectively. Comparison of Adaptation in Conditions I and II Each day in both Conditions I and II there was a decrease in mean words stuttered between Readings 1 and 5* In general this decrease became progressively smaller each day for the first five days in Condition I, when the same passage was read on all days.
On the sixth
day after the interval of ten days, the decrease in means again became larger, due chiefly to the relative increase in stuttering on Reading 1. In
II, when different material was read each day, the decrease
Table VII Percentage of Adaptation Computed from the First Heading in Condition II
r -r 3
r -r 4
r -r 5
Z first reading of seventh day
36 in means remained fairly constant from day to day.
In both Conditions
I and II, the mean differences between Readings 1 and 5 on all days were significant beyond the 1.0$ level of confidence. The mean number of words stuttered in Reading 5 on all days in both Conditions I and II were very similar.
In Condition I these means
varied from 14.22 to 18.96, and in Condition II, from 15*37 to 20.70. In every day*s readings in both Conditions I and II, there was a systematic decrease in mean stuttered words in successive readings from 1 to 5* Each day the largest decrease in means occurred between Readings 1 and 2, after which the decrease became progressively smaller in the three last readings. The curves obtained by plotting the mean number of stuttered words in the five readings of each day in both Conditions I and II are all of the same general shape.
All show a sharp decline between.Readings 1 and
2, after which each gradually levels off in the three last readings of the day.
All may be described as negatively accelerated positive curves.
In Condition I, however, the curves tend to flatten out after the third day, until the sixth day is reached. The four curves in Condition IIall have the same general form as the curve of
the first day *s reading in
Condition I. The percentages of adaptation were similar in
Conditions I and II.
The percentages of stuttered words in both Conditions were reduced between 56.8 and 68.6 per cent in the final readings of the various days. When the same material was read each day, the greatest adaptation occurred the second day in Reading 4, a 68.6 per cent reduction from the frequency
37 of stuttering in Reading 1 of the first day.
.vhen a different passage
was read each day, the greatest adaptation was reached on the ninth day in Reading 5, the percentage of stuttering being reduced 6?*4 per cent from the frequency of stuttering in Reading 1 of the seventh day. The outstanding differences between percentages of adaptation in Conditions I and II were found in the first readings of the different days.
In Condition I, when the same reading material was used, the
percentages of adaptation in Reading 1 of the successive days were lauch larger than the percentages in the same readings in Condition II, when different material
as read each day.
$ith different reading material
there was not the same cany-over effect (more spontaneous recovery) from one day to the next as when the reading material was kept constant. The readers adapted better when both the reading content and the reading situation remained constant, as in Condition I, than when the situation remained constant but the reading content varied, as in Condition II. Effect of Time Interval in Condition I The same material was read five times in succession on each of five successive days, and again on a sixth day after an interval of ten days, in order to determine the influence on frequency of stuttering of a 24-hour interval, and of a ten-day interval, respectively, between the reading series.
The means of the first and last readings on each day
of Condition I are shown in Table VIII, and is illustrated graphically in. Figure 3.
The first day the means were reduced from 43-83 stuttered
Table VIXi Means of Stuttered Words in Readings 1 and 5 on all Rays in Condition I
10-Day Interval 6
A\ean number of wonH stuttered
Reading 1 Reading 5>
Figure 3 Mean number of words stuttered in Readings 1 and $ in Condition X
40 words in the first reading to 15.00 in the fifth.
This decrease in
stuttering was temporary, however; on the second day in the first reading the mean frequency rose to 30