JOURNAL OF COMMUNICATION
DISORDERS
9, (1976), 95-l 10
THE INFLUENCE OF TASK PRESENTATION AND INFORMATION LOAD ON THE ADAPTATION EFFECT IN STUTTERERS AND NORMAL SPEAKERS ROBERT
M. KROLL
Director of Speech Pathology, Clarke Institate of Psychiatry, Toronto, Ontario, Canada
STEPHEN
B. HOOD
Associate Professor, Speech and Hearing, Bowling Green State University, Bowling Green, Ohio
Fourteen stutterers and 14 normal speakers read two passages differing in information value under two different conditions. Condition I provided subjects with apriori knowledge regarding the experimental limits and requirements. Condition II withheld such knowledge. Results indicate that adaptation curves for both stutterers and normal speakers were influenced by the information value of the reading passage. Less adaptation was observed with the high information than with the low information passage. The task presentation variable differentiated stutterers from normal speakers. When apriori instructions were provided to stutterers, the adaptation curve assumed a smooth, decelerating course. When a priori instructions were. withheld, the curve deviated from the expected course. For normal speakers, identical adaptation trends were observed whether or not a priori instructions were provided. Stuttering adaptation is a function of both linguistic and situational variables; normal nonfluency adaptation is primarily a function of linguistic variables. Theoretical, experimental, and clinical implications are offered.
Introduction Recently, we suggested that the phenomenon of adaptation is more diverse and complex than is commonly believed. We indicated (Kroll and Hood, 1974) that stutterers manifest adaptation in reading, but not in spontaneous speech in the form of picture description. In view of this finding an attempt is made here to further identify underlying factors that contribute to adaptation in reading for both stutterers and nonstutterers. The adaptation effect generally refers to a progressive decrement in the frequency of stuttering behavior with successive readings of the same material. Research comparing quantitative and qualitative differences in adaptation trends between stutterers and normal speakers has produced somewhat equivocal findings. Whereas several investigators reported neither quantitative nor qualitative differences between the adaptation trends of stutterers and normal speakers (Sasanuma, 1968; Silverman and Williams, 1968; Silverman, 1970a,b), other researchers have suggested that the adaptation curves for the two groups are significantly different (Neelley and Timmons, 1967; Starbuck and Steer, 1953). Wischner (1950, 1952) hypothesized that the stutterer adapts to both the general speaking situation and to the specific speech context. Support for a general @ American
Elsevier Publishing
Company,
Inc.,
1976
95
%
ROBERT
M. KROLL
and STEPHEN
B. HOOD
situation variable is evidenced by such cues as colored borders surrounding the adaptation page (Johnson and Knott, 1937; Johnson, Larson, and Knott, 1937; Fierman, 1955), the adjacency effect (Johnson and Millsaps, 1937; Brutten and Gray, 1961; Rappaport and Bloodstein, 197 l), and other intervening variables introduced either prior to or during the experimental task (Wingate, 1972). A situational variable that has yet to be fully investigated concerns the amount and type of a priori knowledge given to the subject pertaining to the nature of the task. In the typical experimental setting, the subject is placed in a room with the experimenter and is handed a reading passage (Adams and Reis, 1971; Besozzi and Adams, 1969; Kroll, 1971; Kroll and Hood, 1974; Starbuck and Steer, 1953) or a packet containing five copies of the passage (Brutten, 1963; Wingate, 1972). The subject is then instructed to read aloud and, after a brief pause, to repeat the reading up to a total of five times (Beech and Fransella, 1968). The subject is thus provided with sufficient instruction and/or reading material so that he is fully cognizant of the requirements and limits inherent in the total experimental task. Brutten (1963) utilized the above experimental procedure and demonstrated that a reduction in stuttering during successive oral readings was accompanied by a similar reduction in anxiety as measured by palmar sweat scores. However, Gray and Brutten (1965) failed to confirm these results. Beech and Fransella (1968) attribute these discrepant findings to variations in experimental procedures. In Brutten’s study the subject was presented with a packet of reading passages stapled together. The subject was instructed to read each page and then turn to the next, which was identical. He continued in this way throughout the session. In the Gray and Brutten study, the subject was given one page and told to read it. The page was taken away after it had been read and another identical page handed to him. Gray suggests that in the former study he could form a ‘gestalt’ whereas in the latter he was uncertain of the limits of the experiment (p. 156).
An analogous argument for the importance of the subject’s a priori perceptual set or gestalt is offered by Forte and Schlesinger (1972). This situational variable appears worthy of further study. The specific speech or linguistic context to which the stutterer adapts includes variables that are totally verbal in nature. It has been repeatedly demonstrated that both stuttering and normal nonfluency are related to such factors as word length, grammatical class, word position, and initial phoneme class (Brown, 1945; Bloodstein, 1969; Quarrington, Conway, and Siegel, 1962; Quarrington, 1965; Taylor, 1966; Blankenship, 1964; Silverman, 1972). Taylor (1966) and Bloodstein (1969) have pointed out that much of the research investigating one of the four specific factors influencing stuttering has neglected to control for the presence or absence of the remaining variables. Similar arguments can be directed toward the research with normal speaking populations. Consequently, many studies that have attempted to identify the factor or factors contributing to stuttering and/or normal nonfluency employed inadequate control of
TASK PRESENTATION,
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LOAD,
AND ADAPTATION
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other pertinent variables. These variables may have been overlooked or may have been confounded with the experimental variable. Thus, the pattern of interrelationships of the factors remains unclear. It has been demonstrated that both stuttering and normal nonfluency are highly related to the amount of information conveyed by specific words (GoldmanEisler, 1968; Lanyon and Duprez, 1970; Quarrington, 1965; Schlesinger, Forte, Fried, and Melkman, 1965; Soderberg, 197 1). Furthermore, there exists a considerable degree of overlap between previously identified factors contributing to stuttering and the amount of statistical uncertainty or information conveyed by words (Bloodstein, 1969, p. 191). Similar structural constraints affect the amount of nonfluency in normal speakers, the major or underlying factor being that of information value (Taylor, 1966). Although some research has been directed toward manipulating the reading material during the adaptation task, the degree to which a stutterer adapts to specific aspects of the speech context is not currently understood (Bloodstein, 1969). Specifically, the degree to which reading passages, differing in the amount of information, will have differential effects on stuttering adaptation has yet to be empirically tested. The major purpose of this research, therefore, was to determine the extent to which the method of task presentation influences stuttering and normal nonfluency during adaptation, and the extent to which the information value of the reading passage influences stuttering and normal nonfluency during adaptation. Furthermore, the present study attempted to add additional information concerning the degree of similarity between the adaptation trends of stutterers and normal speakers. The following experimental questions were posed: (1) Is the differentially (2) Is the differentially
frequency of stuttering and normal nonfluency during adaptation influenced by the method of task presentation? frequency of stuttering and normal nonfluency during adaptation influenced by the information value of the reading passage?
Method Subjects
Fourteen stutterers and 14 normal speakers served as subjects in this study. The two groups of subjects were matched according to age, sex, and educational level. The stuttering group included 1 female and 13 males, ranging in age from 15 to 23 years, with a mean age of 18 years, 9 months. They were selected from among stutterers enrolled for speech therapy at clinics affiliated with Bowling Green State University, Pennsylvania State University, Westchester State College, and Eastem Michigan University in order to prevent the inclusion of subjects who might all have been exposed to a similar therapeutic approach.
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M. KROLL
and STEPHEN
B. HOOD
The normal speaking group included 1 female and 13 males, ranging in age from 15 to 24 years, with a mean age of 19 years, 8 months. They were selected from among those residing in the Bowling Green, Ohio, and Westchester, Pennsylvania areas. Reading
Material
Two 150-word passages were used as reading material for this study. The passages were selected from among 36 whose content had been analyzed and calibrated by Miller and Coleman (1967) for the information value that each contained. Their analysis was based on the cloze procedure, a technique that has been widely used to determine information values for prose passages. The reading passages were obtained from the United States Library of Congress (Document Number AD1 9601). Passage I (cloze score = 1,389) was designated as a “low information” passage; Passsge II (cloze score = 752) was designated as a “high information” passage. Task Presentation Two methods of task presentation were employed in this study. Condition I ensured that the subject was made completely aware of the total requirements of the experimental task. Condition II was constructed so that the subject was unable to predict the experimental requirements. For Condition I, the subject was handed a manilla folder containing a packet of five copies of the same passage, stapled together. Each copy was printed on an 8% ” X 11” white sheet of paper. The following instructions were given immediately before the first reading. “I have just handed you a packet of five identical reading passages. Each passage is printed on a separate page. When I give the signal “begin,” open the folder and read the first passage in your normal reading voice. Just as soon as you have finished turn the page, and read the same passage on Page 2. Continue reading the passages and turning the pages until you have read every one of the five passages. Remember, all passages are identical and your task is to read the passage on each page, making a total of five readings. Are there any questions?”
For Condition II, the subject was handed a single sheet of white paper contaning the reading passage. No instructions were provided other than, “Please read this in your normal reading voice.” When the subject completed the first reading, the experimenter instructed him, “Now read it again.” This procedure was continued until a total of five readings was accomplished. Ordering of Experimental It has been reported
Tasks
that a confounding
variable
in adaptation
studies arises
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INFORMATION
LOAD,
AND ADAPTATION
99
when subjects are asked to engage in adaptation tasks for more than one session. This has been attributed to the instability of the adaptation measure (Cullinan, 1963), and the fact that the subject is often less motivated and more resistive in subsequent sessions due to the length and monotony of the procedure on the first day (Cohen, 1952; Fierman, 1955). Consequently, the present study required subjects to complete all experimental tasks within one session. Each subject was required to produce massed oral readings for each of two passages under each of two methods of task presentation. Half of the subjects in each group read Passage I first; the other half read Passage II first. Similarly, half of the subjects read the passages under Condition I first, while half of the subjects read the passages under Condition II first. A total of 20 reading trials were thus obtained from each subject. A rest period of approximately 20 min was introduced following the first two sets of five readings to eliminate the possibility of fatigue due to the lengthy experimental task and to allow for the recovery of the stuttering response (Leutenegger, 1957). Subjects were chosen at random to determine the order of both reading passages and task presentation. Thus, seven randomly selected subjects in both groups performed the experimental tasks in each of the following orders: Passage I/Condition Passage II/Condition Rest Period Passage I/Condition Passage II/Condition All readings
II I I II
Passage II/Condition I Passage I/Condition II Rest Period Passage II/Condition II Passage I/ Condition I
were tape recorded on a Sony TC105 tape recorder.
Data Analysis Instances of stuttering and normal nonfluency were defined as any repetition, prolongation or revision of a sound, syllable, word, or phrase; any extraneous vocalizations (e.g., interjections) unrelated to the speech context; and any silent pauses unrelated to normal juncture boundaries. For all statistical analyses raw data were converted to ranks for use with the nonparametric Friedman two-way analysis of variance (Siegel, 1956)) and converted to proportions for graphic and tabular illustrations. Separate analyses were computed to test for the effects of different passages (collapsed across task presentation) and different methods of task presentation (collapsed across reading passages) on the adaptation scores for both groups of subjects. The nonparametric Friedman has been suggested for these types of data (Silverman and Williams, 1968). All analyses were required to meet significance at thep < 0.01 level. When this criterion was met, the nonparametric analog to the Scheffe post hoc analysis (Marasculio, 1968) was computed.
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M. KROLL
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B. HOOD
Results Inter- and Intra-judge
Reliability
The Pearson Product-Moment Correlation Coefficient was computed to determine the interjudge and intrajudge reliability of frequency counts for both moments of stuttering and instances of normal nonfluency. Correlation coefficients for the senior experimenter’s self-agreement were 0.99 for the stuttering group and 0.98 for the normal speaking group. Correlation coefficients for the senior experimenter’s agreement with an independent judge (a doctoral student with CCC-Sp, ASHA) were determined to be 0.98 for the stuttering group and 0.96 for the normal speaking group. The Influence of Task Presentation on Adaptation Stutterers. Table 1 shows the group mean absolute frequencies and proportions of stuttering moments across the five reading trials for each of the conditions collapsed across passages. A Friedman two-way analysis of variance by ranks revealed that the differences in stuttering moments across the five reading trials were significant for both Condition I (X2 = 50.85, df = 4, p < 0.001) and Condition II (X2 = 38.56, df = 4, p < 0.001)). Results of the post hoc analysis for Condition I indicate that the following reading trial means differed significantly: 1 and 3, 1 and 4, 1 and 5, 2 and 5. Results of the post hoc analysis for Condition II indicate that the following reading trial means differed significantly: 1 and 4, 1 and 5, 2 and 4, 2 and 5, 3 and 5. Figure 1 represents a graphic illustration of the group mean proportions of stuttering moments for Conditions I and II. It can be observed from Fig. 1 that the method of task presentation directly influenced the course of stuttering adaptation acrossthe five reading trials. For Conditon I, the adaptation curve followed a smoothly decelerating course with 30.3% of all stuttering moments occurring on trial one and 12.9% of all stuttering moments occurring on trial five. However, for Condition II, the curve was highly irregular as 23.9% of all stuttering moments TABLE 1 Group Mean Absolute Frequencies and Proportions of Total Stuttering Moments for Task Presentation with a priori Instruction (Condition I) and Task Presentation with No Instruction (Condition II), Collapsed across Reading Passages Condition
Trial
1
Trial 2
Trial 3
Trial 4
Trial 5
I-% Freq. IX Pet.
52.19 0.303
42.29 0.228
36.36 0.176
32.93 0.165
29.29 0.129
II x Freq. II x Pet.
43.71 0.239
45.93 0.269
41.00 0.198
33.64 0.166
27.86 0.129
TASK
Fig. 1. Stuttering
PRESENTATION,
adaptation
INFORMATION
curves for Conditions
LOAD,
AND ADAPTATION
I and II, collapsed
101
across reading passages.
occurred on trial one followed by an increase to 26.9% of all stuttering moments on trial two. The curve then decelerated smoothly across the last three reading trials. Normal speakers. Table 2 shows the group mean absolute frequencies and proportions of normal nonfluencies across the five reading trials for each of the conditions, collapsed across passages. A Friedman two-way analysis of variance by ranks revealed that the differences in normal nonfluencies across the five reading trials were significant for both Condition I (X2 = 45.20, df = 4, p < 0.001) and Condition II (X2 = 42.20, df = 4,p < 0.001). Results of the post hoc analysis for Condition I indicate that the following reading trial means differed significantly: 1 and 3, 1 and 4, 1 and 5, 2 and 5. Results of the post hoc analysis for Condition II indicate that the following reading trial means differed significantly: 1 and 3, 1 and 4, 1 and 5, 2 and 5. Figure 2 represents a graphic illustration of the group mean proportions of normal nonfluencies for Conditions I and II, collapsed across passages. It can be observed from Fig. 2 that the method of task presentation does not affect the course of nonfluency adaptation. Both curves are essentially similar in nature. For Condition I, 3 1.9% of all normal nonfluencies occurred on trial one and 11.7% occurred on the last reading trial. For Condition II, 3 1.3% of all normal nonfluencies occurred on trial one and 11.5% occurred on the last reading trial.
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M. KROLL
and STEPHEN
B. HOOD
TABLE 2 Group Mean Absolute Frequencies and Proportions of Total Normal Nonfluencies for Task Presentation with a priori Instruction (Condition I) and Task Presentation with No Instruction (Condition II), Collapsed across Reading Passages Trial 1
Trial 2
Trial 3
Trial 4
Trial 5
I T? Freq. I x Pet.
11.93 0.319
8.50 0.222
7.21 0.180
6.36 0.161
4.64 0.117
II x Freq. II x Pet.
11.64 0.313
9.14 0.239
6.79 0.169
5.64 0.164
4.57 0.115
Condition
Fig. 2. Normal nonfluency passages.
adaptation
curves
for Conditions
I and II, collapsed
across
reading
The Influence of Information Value on Adaptation Stutterers. Table 3 shows the group mean absolute frequencies and proportions of stuttering moments across the five reading trials for each of the passages, collapsed across conditions. A Friedman two-way analysis of variance by ranks revealed that the differences in stuttering moments across the five reading trials were significant for both Passage 1 (X2 = 47.47, df = 4, p < 0.001) and Passage 11(X2 = 38.56,#= 4,p < 0.001). TheaboveanalysesaresummarizedinTable 3.
TASK
PRESENTATION,
INFORMATION
LOAD,
AND ADAPTATION
103
TABLE 3 Group Mean Absolute Frequencies and Proportions of Total Stuttering Moments across Five Reading Trials for Low (I) and High (II) Information Passages, Collapsed across Conditions Passage
Trial 1
Trial 2
Trial 3
Trial 4
Trial 5
I fT Freq. IX Pet.
38.93 0.302
36.50 0.259
30.00 0.194
25.29 0.149
19.71 0.096
II g Freq. II x Pet.
57.57 0.253
51.57 0.236
47.21 0.183
41.29 0.173
37.71 0.155
Results of the post hoc analysis for Passage I indicate that the following reading trial means differed significantly: 1 and 4, 1 and 5, 2 and 4, 2 and 5, 3 and 5. Results of the post hoc analysis for Passage II indicate that the following reading trial means differed significantly: 1 and 4, 1 and 5, 2 and 4, 2 and 5. Figure 3 represents a graphic illustration of the group mean proportions of stuttering moments on Passages I and II, collapsed across conditions. It can be observed from Fig. 3 that the amount and rate of stuttering adaptation is directly influenced by the information value of the reading passage. For Passage I, 30.2% of all stuttering moments occurred on trial one, whereas only 9.6% of all stuttering moments occurred on the last reading trial. For Passage II, 25.3% of all stuttering
Fig. 3. Stuttering
adaptation
curves for Passages
I and II, collapsed
across conditions.
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ROBERT
M. KROLL
and STEPHEN
B. HOOD
moments occurred on trial one, whereas 15.5% of all stuttering moments occurred on the last reading trial. Normal speakers. Table 4 shows the group mean absolute frequencies and proportions of normal nonfluencies across the five reading trials for each of the passages, collapsed across conditions. A Friedman two-way analysis of variance by ranks revealed that the differences in normal nonfluencies across the five reading trials were significant for both Passage I (X2 = 48.99, df = 4, p < 0.001) and Passage II (X2 = 37.95, df = 4,p < 0.001). Results of the post hoc analysis for Passage I indicate that the following reading trial means differed significantly: 1 and 3, 1 and 4, 1 and 5,2 and 5. Results of the TABLE 4 Group Mean Absolute Frequencies and Proportions of Total Normal Nonfluencies across Five Reading Trials for Low (I) and High (II) Information Passages, Collapsed across Conditions Passage Ix Freq. IX Pet. II x Freq. II R Pet.
Trial 1
Trial 2
Trial 3
Trial 4
Trial 5
8.57 0.4 14
5.79 0.256
3.64 0.157
2.78 0.126
1.29 0.047
15.00 0.284
11.86 0.222
10.36 0.181
9.21 0.168
7.93 0.144
Fig. 4. Normal nonfluency
adaptation
curves for Passages
I and II, collapsed
across conditions.
TASK PRESENTATION,
INFORMATION
LOAD,
AND ADAPTATION
105
post hoc analysis for Passage II indicate that the following reading trial means differed significantly: 1 and 3, 1 and 4, 1 and 5. Figure 4 represents a graphic illustration of the group mean proportions of instances of normal nonfluency on Passages I and II, collapsed across conditions. It can be observed from Fig. 4 that the amount and rate of adaptation exhibited by normal speakers is directly influenced by the information value of the reading passage. For Passage I, 41.4% of all normal nonfluencies occurred on trial one, whereas only 4.7% of all normal nonfluencies occurred on the last reading trial. For Passage II, 28.4% of all normal nonfluencies occurred on trial one, whereas 14.4% of all normal nonfluencies occurred on the last reading trial. In summary, the method of task presentation represents a variable that differentiates stutterers from normal speakers. Whereas stutterers exhibited a smooth, negatively accelerating adaptation curve when provided with a priori information regarding the requirements and limits of the experimental task, the curve deviates from the pattern when no such information is provided. The normal speakers exhibited identical adaptation trends regardless of the method of task presentation. On the other hand, the information value of the reading passage determines the amount and rate of adaptation for both groups of subjects. Massed oral readings of the low information passage yielded greater and more rapid adaptation for stutterers and normal speakers than those adaptation curves obtained with the high information passage. Moreover, with Passage I, and to a lesser degree with Passage II, normal speakers showed greater adaptation than did stutterers. Discussion The Influence of Task Presentation on Adaptation Adaptation trends of stutterers and normal speakers can be differentiated when the treatment variable under consideration is task presentation. For the stutterers, a priori knowledge of the experimental limits and requirements (Condition I) yielded the expected smooth, decelerating adaptation curve; however, when a priori instruction was not provided (Condition II), the curve assumed an uneven shape as the amount of observed stuttering behavior increased from trial one to trial two. These results provide evidence to support the theoretical contention of Forte and Schlesinger (1972) that the shape of the stuttering adaptation curve will be determined by the amount of information given to the stutterer pertaining to the number of times the passage is to be read. In the present study, apriori knowledge of the experimental task included information regarding the number of required readings. The stutterer’s ability to form a gestalt of the total experiment is thus a major factor that determines the regularity or irregularity of the adpatation curve. The data obtained from this portion of the present investigation appear to confirm Wischner’s (1950) explanation of the relationship between general situa-
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M. KROLL
and STEPHEN
B. HOOD
tional anxiety and stuttering adaptation. Subsequent tests of Wischner’s hypothesis have demonstrated that the stuttering adaptation curve is altered when the general reading situation is in any way manipulated prior to, or during, the experimental task. Conversely, when general situational variables are held constant throughout the entire succession of reading trials, the course of the adaptation curve is essentially predictable (Fierman, 1955; Wingate, 1972). It is apparent from the results of the present investigation that the method of task presentation may be regarded as a situational variable which, when varied, alters the course of stuttering adaptation. When the subject is provided with sufficient prior instruction to form a complete perceptual “set” regarding the task at hand, adaptation to the general reading situation follows a smooth course. Results of the data obtained under Condition I can be explained in terms of this proposed model. The subject is presented with a set of complete instructions in addition to a packet containing the required reading material before any speech behavior is accomplished. Thus, the stutterer is fully cognizant of the general situation confronting him and gradually adapts to this unchanging situation with successive oral readings. If the stutterer is not totally aware of the exact nature of the experimental task prior to the oral reading (Condition II), it is conceivable that his perceptual “set” toward the experiment will fluctuate during his performance. That is, if he is simply instructed to read a single passage that is placed in front of him, his set toward the task may be at a particular level; if upon completion of the reading he is instructed to read the passage again, this unexpected command may alter his anticipatory level concerning his initial performance and/or the number of novel task instructions that the experimenter may ask him to engage in during future readings. The subject’s perceptual set thus switches from one of complete awareness of the task requirements to one of uncertainty and anticipation as to the exact nature and limits of the experiment. Under Condition II, the adaptation curve begins to follow the expected negatively accelerating course after reading trial two. The amount of observed stuttering behavior then decreases through trials three, four, and five in a fashion similar to that under Condition I. These findings may be due to the fact that when the stutterer is asked to read the passage a third time, he comes to realize that the experimenter’s instructions may be identical after every reading. His expectations may then be more defined as he becomes somewhat confident of future events. The subject may now begin to perceive the experiment as a whole (in much the same manner as he was able to do under Condition I) and thus his stuttering decreases. The identification of task presentation as a factor affecting stuttering adaptation has important implications for future experimentation in this area. It is essential that identical methods of task presentation be employed in studies attempting to replicate and/or verify past adaptation research. It might also be interesting to
TASK
PRESENTATION,
attempt to identify
INFORMATION
those situational
LOAD,
AND
ADAPTATION
factors that result in abnormal
107
adaptation
curves for normal speakers. In addition to the above theoretical and experimental implications, the variable of task presentation could conceivably be employed clinically with the stutterer. It might be meaningful to observe a stutterer’s adaptation trends under both methods of task presentation so that comparisons can be made regarding the individual’s speech performance under both predictable and uncertain reading situations. For the stutterer whose speech deteriorates under conditions of uncertainty, thereby producing uneven adaptation trends, thereapy might be directed toward increasing this individual’s ability to cope with a variety of unexpected events. If after a period of therapy the stutterer’s adaptation curve for Condition II approximates that for Condition I, the clinician may gain some indication that the stutterer’s reactions to talking and/or reading are approaching those of the normal speaker. For normal speakers massed oral readings under Condition I produced an almost identical adaptation curve to those under Condition II. These results indicate that the situational variable of task presentation has no real effect on the adaptation trends of nonstutterers. These findings can be accounted for by considering both the experimental tasks and the nature of the sample population. Unlike the stutterer, the normal speaker’s attitude toward talking and reading is largely one of indifference. These activities represent everyday occurrences that have never posed any specific problems for the individual. It would, therefore, seem to be of little consequence to the normal speaker whether or not he is provided with a priori information regarding the nature of the reading task. The subject’s performance level is consequently unchanged from Condition I to Condition II. The adaptation curve representative of the normal speaker is, therefore, mainly one of adaptation to the specific linguistic content of the reading passage. Informal questioning of subjects following the experiment seemed to bear out the above proposed models. Twelve of the 14 stutterers indicated that they “felt more anxious” when they were not given any instructions before the task. None of the normal speaking subjects indicated any difference in personal reactions between the two conditions other than that Condition II produced more curiosity pertaining to the purpose of the experiment. Past research that has reported neither qualitative nor quantitative differences between the adaptation trends of stutterers and normal speakers (Sasanuma, 1968; Silverman et al., 1968; Silverman, 1970a,b) must now be disputed on the basis of the situational variable identified in the present investigation. Whereas normal speakers remained essentially unaffected when the situational variable of task presentation was manipulated during the adaptation task, stutterers exhibited dramatic differences when the task presentation was varied. This factor yields quantitative as well as qualitative differences between the adaptation curves of stutterers and normal speakers.
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M. KROLL
and STEPHEN
B. HOOD
The Influence pf Information Load on Adaptation The amount of information in a reading passage, as measured by the cloze procedure, influences the amount and rate of adaptation for both stutterers and normal speakers. A reading passage containing a relatively low amount of conveyed information yields greater and more rapid adaptation than a passage of high information value. The effect of this treatment variable can be observed for both stutterers (Fig. 3) and normal speakers (Fig. 4). Schlesinger et al. (1965) postulated that the phenomenon of adaptation may be accounted for by a reduction in information load with massed oral readings of the same passage. The findings of the present study agree with this theoretical posture as indicated by differences in amounts of adaptation when information load is varied. Less adaptation is observed for the high information passage due to the slower rate of reduction in information load. That is, the subject’s proficiency in prediction proceeds at a relatively slow rate with repeated oral readings due to the high amount of information initially inherent in the passage. Conversely, adaptation occurs more rapidly, and to a greater extent, on the low information passage, as information load decreases rapidly due to the relatively high initial transitional probabilities of specific words and word sequences in the passage. In response to an informal interview conducted following the experimental session, 12 of the 14 stutterers and 11 of the 14 normal speakers indicated that the high information passage was “more difficult to read” than the low information passage. These responses provide further evidence to support the contention that the initial “difficulty” of the passage, which can be operationally defined as its information load, will determine the eventual course of the adaptation curve for both stutterers and normal speakers. The above findings have important experimental implications with regard to verification and/or replication of previous research on adaptation. The results of this study indicate the importance of specifying the information value of experimental reading passages utilized in adaptation studies. Failure to incorporate such data does not allow for verification of previously reported results. Thus, the experimenter should be aware of the importance of disseminating information regarding the complexity or cloze score totals of his reading passages. Wischner’s (1950) theoretical explanation of the adaptation phenomenon includes both linguistic and nonlinguistic variables. That is, the stutterer adapts to both the general speaking situation and to specific words in the reading passage. The results of this study provide powerful evidence to support the hypothesis that both linguistic (information load) and nonlinguistic (task presentation) variables are important determinants of stuttering adaptation. The normal speakers, however, fit only partially into Wischner’s two-factor model of adaptation. For nonstutterers, the linguistic variable of information load is the major determinant
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AND ADAPTATION
109
of nonfluency adaptation, whereas the situational variable of task presentation does not appear to be important. This study is based on a portion of a doctoral dissertation by Robert Kroll, completed under the directorship of Stephen B. Hood. The authors wish to thank Drs. James Frick, Gerald Moses, and Joseph Stigora for their assistance in gathering subjects. Special appreciation is extended by the senior author to Drs. B. Greenberg, W. Hinkle, M. Hyman, and F. Piggeforserving as members of the doctoral committee. Mrs. Janet Watson did an excellent job typing this manuscript. Requests for reprints should be sent to either author. References Adams,
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H. R., Fransella, F. Research and experiment in sfuffering. New York: Pergamon Press, 1968. Besozzi, T. E., Adams, M. R. The influence of prosody on stuttering adaptation. J. Speech Hearing Res., 1969, 9, 4&44. Blankenship, J. “Stuttering” in normal speech. J. Speech Hearing Res., 1964, 7, 9596. Bloodstein, 0. A handbook on stuttering. Chicago: National Easter Seal Society for Crippled Children and Adults, 1969. Brown, S. F. The loci of stutterings in the speech sequence. J. Speech Dis., 1945, 10,181-192. Brutten, E. J. Palmer sweat investigation of disfluency and expectancy adaptation. J. Speech Hearing Beech,
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Brutten, E. J., Gray, B. B. Effect of word cue removal on adaptation and adjacency: A clinical paradigm. J. Speech Hearing Dis., 1961, 26, 385-389. Cohen, E. A comparison of oral reading and spontaneous speech of stutterers with special reference to the adaptation and consistency effects. Ph.D. dissertation, University of Iowa, 1952. Cullinan, W. L Stability of adaptaton in the oral performance of stutterers. J. Speech Hearing Res., 1963, 6, 70-83.
Fierman,
E. Y. The role of cues in stuttering adaptation. In W. Johnson and R. R. Leutenegger (I%.), in children and adults. Minneapolis: University of Minnesota Press, 1955. Forte, M., Schlesinger, I. M. Stuttering as a function of time of expectation. J. Commun. Dis., 1972, 5, 347-358. Goldman-Eisler, F. Psycholinguistics: Experiments in spontaneous speech. New York: Academic Press, 1968. Gray, B. B., Brutten, E. J. The relationship between anxiety, fatigue and spontaneous recovery in stuttering. Behav. Res. Ther., 1965, 2, 251-259. Johnson, W., Knott, J. Studies in the psychology of stuttering: I. The distribution of moments of stuttering in successive readings of the same material. J. Speech Dis., 1937, 2, 17-19. Johnson, W., Larson, R. P., Knott, J. R. Studies in the psychology of stuttering: III. Certain objective cues related to the precipitation of the moment of stuttering. J. Speech Dis., 1937, 2, 23-25. Johnson, W., Millsaps, L. S. Studies in the psychology of stuttering: VI. The role of cues representative of past stuttering in the distribution of stuttering moments during oral reading. J. Speech Dis., 1937, 2, 101-104. Kroll, R. M. A frequency count and time measure analysis of the adaptation effect in stutterers. Unpublished Masters thesis, McGill University, 1971. Sfuttering
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Kroll, R. M., Hood, S. B. Differences in stuttering adaptation between oral reading and spontaneous speech. J. Commun. Dis. 1974, 7, 227-231. Lanyon, R. I., Duprez, D. A. Nonfluency, information and word 1ength.J. Abnorm. Psychol., 1970, 76, 93-97.
Leutenegger, 1957,
R. R. Adaptation
and recovery in the oral readings of stutterers.
J. Speech
Hearing
Dis.,
22, 276287.
Marasculio, L. A. Nonparametric statistics. Lecture presented at the American Educational Association Training Session, Chicago, February, 1968. Miller, G. R., Coleman, E. B. A set of thirty-six passages calibrated for complexity. Learning
Verb.
Behav.,
Research J. Verb.
1967, 6, 851-854.
Neelley, J. N., Timmons, R. S. Adaptation and consistency in the disfluent speech behavior of young stutterers and nonstutterers. J. Speech Hearing Res., 1967, 10, 25G256. Quarrington, Abnorm.
B. Stuttering Psychol.,
as a function 1965,70,
of the information
value sentence
position
of words. J.
221-224.
Quarrington, B., Conway, J. K., Siegel, N. An experimental study of some properties of stuttered words. J. Speech Hearing Res., 1962, 5, 387-394. Rappaport, B., Bloodstein, 0. The role of random blackout cues in the distribution of moments of stuttering. J. Speech Hearing Res., 1971, 14, 874-879. Sasanuma, S. A description of the disfluent speech behavior of stuttering and nonstuttering Japanese children. Unpublished doctoral dissertation, University of Iowa, 1968. Schlesinger, I. M., Forte, M., Fried, B., Melkman, R. Stuttering, information load and response strength. J. Speech Hearing Dis., 1965, 22, 9%103. Siegel, S., Nonparametric statistics for the behavioral sciences. New York: McGraw Hll, 1956. Silverman, F. H. A note on the degree of adaptation by stutterers and nonstutterers during oral reading. J. Speech Hearing Res., 1970a, 13, 173-177. Silverman, F. H. Course of nonstutterers’ disfluency adaptation during 15 consecutive oral readings of the same material. J. Speech Hearing Res., 1970b, 13, 382-386. Silverman, F. H. Disfluency and word length. J. Speech Hearing Res., 1972, 15, 788-791. Silverman, F. H., Williams, D. E. A proportional measure of stuttering adaptation. J. Speech Hearing Res., 1968, 11, 444-446. Soderberg, G. A. Relations of word information and word length to stuttering disfluencies. J. Commun. Dis., 1971, 4, 914. Starbuck, H. B., Steer, M. D. The adaptation effect in stuttering speech behavior and normal speech behavior. J. Speech Hearing Dis., 1953, 18, 252-255. Taylor, I. K. What words are stuttered? Psychol. Bull., 1966, 4, 233-242. Wingate, M. E. Deferring the adaptation effect. J. Speech Hearing Res., 1972, 15, 547-550. Wischner, G. J. Stuttering behavior and learning: A preliminary theoretical formulation. J. Speech Hearing Dis., 1950, 15, 324-335. Wischner, G. J. An experimental approach to expectancy and anxiety in stuttering behavior. J. Speech Hearing Dis., 1952, 17, 139154.
DISORDERS
9, (1976), 95-l 10
THE INFLUENCE OF TASK PRESENTATION AND INFORMATION LOAD ON THE ADAPTATION EFFECT IN STUTTERERS AND NORMAL SPEAKERS ROBERT
M. KROLL
Director of Speech Pathology, Clarke Institate of Psychiatry, Toronto, Ontario, Canada
STEPHEN
B. HOOD
Associate Professor, Speech and Hearing, Bowling Green State University, Bowling Green, Ohio
Fourteen stutterers and 14 normal speakers read two passages differing in information value under two different conditions. Condition I provided subjects with apriori knowledge regarding the experimental limits and requirements. Condition II withheld such knowledge. Results indicate that adaptation curves for both stutterers and normal speakers were influenced by the information value of the reading passage. Less adaptation was observed with the high information than with the low information passage. The task presentation variable differentiated stutterers from normal speakers. When apriori instructions were provided to stutterers, the adaptation curve assumed a smooth, decelerating course. When a priori instructions were. withheld, the curve deviated from the expected course. For normal speakers, identical adaptation trends were observed whether or not a priori instructions were provided. Stuttering adaptation is a function of both linguistic and situational variables; normal nonfluency adaptation is primarily a function of linguistic variables. Theoretical, experimental, and clinical implications are offered.
Introduction Recently, we suggested that the phenomenon of adaptation is more diverse and complex than is commonly believed. We indicated (Kroll and Hood, 1974) that stutterers manifest adaptation in reading, but not in spontaneous speech in the form of picture description. In view of this finding an attempt is made here to further identify underlying factors that contribute to adaptation in reading for both stutterers and nonstutterers. The adaptation effect generally refers to a progressive decrement in the frequency of stuttering behavior with successive readings of the same material. Research comparing quantitative and qualitative differences in adaptation trends between stutterers and normal speakers has produced somewhat equivocal findings. Whereas several investigators reported neither quantitative nor qualitative differences between the adaptation trends of stutterers and normal speakers (Sasanuma, 1968; Silverman and Williams, 1968; Silverman, 1970a,b), other researchers have suggested that the adaptation curves for the two groups are significantly different (Neelley and Timmons, 1967; Starbuck and Steer, 1953). Wischner (1950, 1952) hypothesized that the stutterer adapts to both the general speaking situation and to the specific speech context. Support for a general @ American
Elsevier Publishing
Company,
Inc.,
1976
95
%
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M. KROLL
and STEPHEN
B. HOOD
situation variable is evidenced by such cues as colored borders surrounding the adaptation page (Johnson and Knott, 1937; Johnson, Larson, and Knott, 1937; Fierman, 1955), the adjacency effect (Johnson and Millsaps, 1937; Brutten and Gray, 1961; Rappaport and Bloodstein, 197 l), and other intervening variables introduced either prior to or during the experimental task (Wingate, 1972). A situational variable that has yet to be fully investigated concerns the amount and type of a priori knowledge given to the subject pertaining to the nature of the task. In the typical experimental setting, the subject is placed in a room with the experimenter and is handed a reading passage (Adams and Reis, 1971; Besozzi and Adams, 1969; Kroll, 1971; Kroll and Hood, 1974; Starbuck and Steer, 1953) or a packet containing five copies of the passage (Brutten, 1963; Wingate, 1972). The subject is then instructed to read aloud and, after a brief pause, to repeat the reading up to a total of five times (Beech and Fransella, 1968). The subject is thus provided with sufficient instruction and/or reading material so that he is fully cognizant of the requirements and limits inherent in the total experimental task. Brutten (1963) utilized the above experimental procedure and demonstrated that a reduction in stuttering during successive oral readings was accompanied by a similar reduction in anxiety as measured by palmar sweat scores. However, Gray and Brutten (1965) failed to confirm these results. Beech and Fransella (1968) attribute these discrepant findings to variations in experimental procedures. In Brutten’s study the subject was presented with a packet of reading passages stapled together. The subject was instructed to read each page and then turn to the next, which was identical. He continued in this way throughout the session. In the Gray and Brutten study, the subject was given one page and told to read it. The page was taken away after it had been read and another identical page handed to him. Gray suggests that in the former study he could form a ‘gestalt’ whereas in the latter he was uncertain of the limits of the experiment (p. 156).
An analogous argument for the importance of the subject’s a priori perceptual set or gestalt is offered by Forte and Schlesinger (1972). This situational variable appears worthy of further study. The specific speech or linguistic context to which the stutterer adapts includes variables that are totally verbal in nature. It has been repeatedly demonstrated that both stuttering and normal nonfluency are related to such factors as word length, grammatical class, word position, and initial phoneme class (Brown, 1945; Bloodstein, 1969; Quarrington, Conway, and Siegel, 1962; Quarrington, 1965; Taylor, 1966; Blankenship, 1964; Silverman, 1972). Taylor (1966) and Bloodstein (1969) have pointed out that much of the research investigating one of the four specific factors influencing stuttering has neglected to control for the presence or absence of the remaining variables. Similar arguments can be directed toward the research with normal speaking populations. Consequently, many studies that have attempted to identify the factor or factors contributing to stuttering and/or normal nonfluency employed inadequate control of
TASK PRESENTATION,
INFORMATION
LOAD,
AND ADAPTATION
97
other pertinent variables. These variables may have been overlooked or may have been confounded with the experimental variable. Thus, the pattern of interrelationships of the factors remains unclear. It has been demonstrated that both stuttering and normal nonfluency are highly related to the amount of information conveyed by specific words (GoldmanEisler, 1968; Lanyon and Duprez, 1970; Quarrington, 1965; Schlesinger, Forte, Fried, and Melkman, 1965; Soderberg, 197 1). Furthermore, there exists a considerable degree of overlap between previously identified factors contributing to stuttering and the amount of statistical uncertainty or information conveyed by words (Bloodstein, 1969, p. 191). Similar structural constraints affect the amount of nonfluency in normal speakers, the major or underlying factor being that of information value (Taylor, 1966). Although some research has been directed toward manipulating the reading material during the adaptation task, the degree to which a stutterer adapts to specific aspects of the speech context is not currently understood (Bloodstein, 1969). Specifically, the degree to which reading passages, differing in the amount of information, will have differential effects on stuttering adaptation has yet to be empirically tested. The major purpose of this research, therefore, was to determine the extent to which the method of task presentation influences stuttering and normal nonfluency during adaptation, and the extent to which the information value of the reading passage influences stuttering and normal nonfluency during adaptation. Furthermore, the present study attempted to add additional information concerning the degree of similarity between the adaptation trends of stutterers and normal speakers. The following experimental questions were posed: (1) Is the differentially (2) Is the differentially
frequency of stuttering and normal nonfluency during adaptation influenced by the method of task presentation? frequency of stuttering and normal nonfluency during adaptation influenced by the information value of the reading passage?
Method Subjects
Fourteen stutterers and 14 normal speakers served as subjects in this study. The two groups of subjects were matched according to age, sex, and educational level. The stuttering group included 1 female and 13 males, ranging in age from 15 to 23 years, with a mean age of 18 years, 9 months. They were selected from among stutterers enrolled for speech therapy at clinics affiliated with Bowling Green State University, Pennsylvania State University, Westchester State College, and Eastem Michigan University in order to prevent the inclusion of subjects who might all have been exposed to a similar therapeutic approach.
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M. KROLL
and STEPHEN
B. HOOD
The normal speaking group included 1 female and 13 males, ranging in age from 15 to 24 years, with a mean age of 19 years, 8 months. They were selected from among those residing in the Bowling Green, Ohio, and Westchester, Pennsylvania areas. Reading
Material
Two 150-word passages were used as reading material for this study. The passages were selected from among 36 whose content had been analyzed and calibrated by Miller and Coleman (1967) for the information value that each contained. Their analysis was based on the cloze procedure, a technique that has been widely used to determine information values for prose passages. The reading passages were obtained from the United States Library of Congress (Document Number AD1 9601). Passage I (cloze score = 1,389) was designated as a “low information” passage; Passsge II (cloze score = 752) was designated as a “high information” passage. Task Presentation Two methods of task presentation were employed in this study. Condition I ensured that the subject was made completely aware of the total requirements of the experimental task. Condition II was constructed so that the subject was unable to predict the experimental requirements. For Condition I, the subject was handed a manilla folder containing a packet of five copies of the same passage, stapled together. Each copy was printed on an 8% ” X 11” white sheet of paper. The following instructions were given immediately before the first reading. “I have just handed you a packet of five identical reading passages. Each passage is printed on a separate page. When I give the signal “begin,” open the folder and read the first passage in your normal reading voice. Just as soon as you have finished turn the page, and read the same passage on Page 2. Continue reading the passages and turning the pages until you have read every one of the five passages. Remember, all passages are identical and your task is to read the passage on each page, making a total of five readings. Are there any questions?”
For Condition II, the subject was handed a single sheet of white paper contaning the reading passage. No instructions were provided other than, “Please read this in your normal reading voice.” When the subject completed the first reading, the experimenter instructed him, “Now read it again.” This procedure was continued until a total of five readings was accomplished. Ordering of Experimental It has been reported
Tasks
that a confounding
variable
in adaptation
studies arises
TASK PRESENTATION,
INFORMATION
LOAD,
AND ADAPTATION
99
when subjects are asked to engage in adaptation tasks for more than one session. This has been attributed to the instability of the adaptation measure (Cullinan, 1963), and the fact that the subject is often less motivated and more resistive in subsequent sessions due to the length and monotony of the procedure on the first day (Cohen, 1952; Fierman, 1955). Consequently, the present study required subjects to complete all experimental tasks within one session. Each subject was required to produce massed oral readings for each of two passages under each of two methods of task presentation. Half of the subjects in each group read Passage I first; the other half read Passage II first. Similarly, half of the subjects read the passages under Condition I first, while half of the subjects read the passages under Condition II first. A total of 20 reading trials were thus obtained from each subject. A rest period of approximately 20 min was introduced following the first two sets of five readings to eliminate the possibility of fatigue due to the lengthy experimental task and to allow for the recovery of the stuttering response (Leutenegger, 1957). Subjects were chosen at random to determine the order of both reading passages and task presentation. Thus, seven randomly selected subjects in both groups performed the experimental tasks in each of the following orders: Passage I/Condition Passage II/Condition Rest Period Passage I/Condition Passage II/Condition All readings
II I I II
Passage II/Condition I Passage I/Condition II Rest Period Passage II/Condition II Passage I/ Condition I
were tape recorded on a Sony TC105 tape recorder.
Data Analysis Instances of stuttering and normal nonfluency were defined as any repetition, prolongation or revision of a sound, syllable, word, or phrase; any extraneous vocalizations (e.g., interjections) unrelated to the speech context; and any silent pauses unrelated to normal juncture boundaries. For all statistical analyses raw data were converted to ranks for use with the nonparametric Friedman two-way analysis of variance (Siegel, 1956)) and converted to proportions for graphic and tabular illustrations. Separate analyses were computed to test for the effects of different passages (collapsed across task presentation) and different methods of task presentation (collapsed across reading passages) on the adaptation scores for both groups of subjects. The nonparametric Friedman has been suggested for these types of data (Silverman and Williams, 1968). All analyses were required to meet significance at thep < 0.01 level. When this criterion was met, the nonparametric analog to the Scheffe post hoc analysis (Marasculio, 1968) was computed.
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M. KROLL
and STEPHEN
B. HOOD
Results Inter- and Intra-judge
Reliability
The Pearson Product-Moment Correlation Coefficient was computed to determine the interjudge and intrajudge reliability of frequency counts for both moments of stuttering and instances of normal nonfluency. Correlation coefficients for the senior experimenter’s self-agreement were 0.99 for the stuttering group and 0.98 for the normal speaking group. Correlation coefficients for the senior experimenter’s agreement with an independent judge (a doctoral student with CCC-Sp, ASHA) were determined to be 0.98 for the stuttering group and 0.96 for the normal speaking group. The Influence of Task Presentation on Adaptation Stutterers. Table 1 shows the group mean absolute frequencies and proportions of stuttering moments across the five reading trials for each of the conditions collapsed across passages. A Friedman two-way analysis of variance by ranks revealed that the differences in stuttering moments across the five reading trials were significant for both Condition I (X2 = 50.85, df = 4, p < 0.001) and Condition II (X2 = 38.56, df = 4, p < 0.001)). Results of the post hoc analysis for Condition I indicate that the following reading trial means differed significantly: 1 and 3, 1 and 4, 1 and 5, 2 and 5. Results of the post hoc analysis for Condition II indicate that the following reading trial means differed significantly: 1 and 4, 1 and 5, 2 and 4, 2 and 5, 3 and 5. Figure 1 represents a graphic illustration of the group mean proportions of stuttering moments for Conditions I and II. It can be observed from Fig. 1 that the method of task presentation directly influenced the course of stuttering adaptation acrossthe five reading trials. For Conditon I, the adaptation curve followed a smoothly decelerating course with 30.3% of all stuttering moments occurring on trial one and 12.9% of all stuttering moments occurring on trial five. However, for Condition II, the curve was highly irregular as 23.9% of all stuttering moments TABLE 1 Group Mean Absolute Frequencies and Proportions of Total Stuttering Moments for Task Presentation with a priori Instruction (Condition I) and Task Presentation with No Instruction (Condition II), Collapsed across Reading Passages Condition
Trial
1
Trial 2
Trial 3
Trial 4
Trial 5
I-% Freq. IX Pet.
52.19 0.303
42.29 0.228
36.36 0.176
32.93 0.165
29.29 0.129
II x Freq. II x Pet.
43.71 0.239
45.93 0.269
41.00 0.198
33.64 0.166
27.86 0.129
TASK
Fig. 1. Stuttering
PRESENTATION,
adaptation
INFORMATION
curves for Conditions
LOAD,
AND ADAPTATION
I and II, collapsed
101
across reading passages.
occurred on trial one followed by an increase to 26.9% of all stuttering moments on trial two. The curve then decelerated smoothly across the last three reading trials. Normal speakers. Table 2 shows the group mean absolute frequencies and proportions of normal nonfluencies across the five reading trials for each of the conditions, collapsed across passages. A Friedman two-way analysis of variance by ranks revealed that the differences in normal nonfluencies across the five reading trials were significant for both Condition I (X2 = 45.20, df = 4, p < 0.001) and Condition II (X2 = 42.20, df = 4,p < 0.001). Results of the post hoc analysis for Condition I indicate that the following reading trial means differed significantly: 1 and 3, 1 and 4, 1 and 5, 2 and 5. Results of the post hoc analysis for Condition II indicate that the following reading trial means differed significantly: 1 and 3, 1 and 4, 1 and 5, 2 and 5. Figure 2 represents a graphic illustration of the group mean proportions of normal nonfluencies for Conditions I and II, collapsed across passages. It can be observed from Fig. 2 that the method of task presentation does not affect the course of nonfluency adaptation. Both curves are essentially similar in nature. For Condition I, 3 1.9% of all normal nonfluencies occurred on trial one and 11.7% occurred on the last reading trial. For Condition II, 3 1.3% of all normal nonfluencies occurred on trial one and 11.5% occurred on the last reading trial.
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M. KROLL
and STEPHEN
B. HOOD
TABLE 2 Group Mean Absolute Frequencies and Proportions of Total Normal Nonfluencies for Task Presentation with a priori Instruction (Condition I) and Task Presentation with No Instruction (Condition II), Collapsed across Reading Passages Trial 1
Trial 2
Trial 3
Trial 4
Trial 5
I T? Freq. I x Pet.
11.93 0.319
8.50 0.222
7.21 0.180
6.36 0.161
4.64 0.117
II x Freq. II x Pet.
11.64 0.313
9.14 0.239
6.79 0.169
5.64 0.164
4.57 0.115
Condition
Fig. 2. Normal nonfluency passages.
adaptation
curves
for Conditions
I and II, collapsed
across
reading
The Influence of Information Value on Adaptation Stutterers. Table 3 shows the group mean absolute frequencies and proportions of stuttering moments across the five reading trials for each of the passages, collapsed across conditions. A Friedman two-way analysis of variance by ranks revealed that the differences in stuttering moments across the five reading trials were significant for both Passage 1 (X2 = 47.47, df = 4, p < 0.001) and Passage 11(X2 = 38.56,#= 4,p < 0.001). TheaboveanalysesaresummarizedinTable 3.
TASK
PRESENTATION,
INFORMATION
LOAD,
AND ADAPTATION
103
TABLE 3 Group Mean Absolute Frequencies and Proportions of Total Stuttering Moments across Five Reading Trials for Low (I) and High (II) Information Passages, Collapsed across Conditions Passage
Trial 1
Trial 2
Trial 3
Trial 4
Trial 5
I fT Freq. IX Pet.
38.93 0.302
36.50 0.259
30.00 0.194
25.29 0.149
19.71 0.096
II g Freq. II x Pet.
57.57 0.253
51.57 0.236
47.21 0.183
41.29 0.173
37.71 0.155
Results of the post hoc analysis for Passage I indicate that the following reading trial means differed significantly: 1 and 4, 1 and 5, 2 and 4, 2 and 5, 3 and 5. Results of the post hoc analysis for Passage II indicate that the following reading trial means differed significantly: 1 and 4, 1 and 5, 2 and 4, 2 and 5. Figure 3 represents a graphic illustration of the group mean proportions of stuttering moments on Passages I and II, collapsed across conditions. It can be observed from Fig. 3 that the amount and rate of stuttering adaptation is directly influenced by the information value of the reading passage. For Passage I, 30.2% of all stuttering moments occurred on trial one, whereas only 9.6% of all stuttering moments occurred on the last reading trial. For Passage II, 25.3% of all stuttering
Fig. 3. Stuttering
adaptation
curves for Passages
I and II, collapsed
across conditions.
104
ROBERT
M. KROLL
and STEPHEN
B. HOOD
moments occurred on trial one, whereas 15.5% of all stuttering moments occurred on the last reading trial. Normal speakers. Table 4 shows the group mean absolute frequencies and proportions of normal nonfluencies across the five reading trials for each of the passages, collapsed across conditions. A Friedman two-way analysis of variance by ranks revealed that the differences in normal nonfluencies across the five reading trials were significant for both Passage I (X2 = 48.99, df = 4, p < 0.001) and Passage II (X2 = 37.95, df = 4,p < 0.001). Results of the post hoc analysis for Passage I indicate that the following reading trial means differed significantly: 1 and 3, 1 and 4, 1 and 5,2 and 5. Results of the TABLE 4 Group Mean Absolute Frequencies and Proportions of Total Normal Nonfluencies across Five Reading Trials for Low (I) and High (II) Information Passages, Collapsed across Conditions Passage Ix Freq. IX Pet. II x Freq. II R Pet.
Trial 1
Trial 2
Trial 3
Trial 4
Trial 5
8.57 0.4 14
5.79 0.256
3.64 0.157
2.78 0.126
1.29 0.047
15.00 0.284
11.86 0.222
10.36 0.181
9.21 0.168
7.93 0.144
Fig. 4. Normal nonfluency
adaptation
curves for Passages
I and II, collapsed
across conditions.
TASK PRESENTATION,
INFORMATION
LOAD,
AND ADAPTATION
105
post hoc analysis for Passage II indicate that the following reading trial means differed significantly: 1 and 3, 1 and 4, 1 and 5. Figure 4 represents a graphic illustration of the group mean proportions of instances of normal nonfluency on Passages I and II, collapsed across conditions. It can be observed from Fig. 4 that the amount and rate of adaptation exhibited by normal speakers is directly influenced by the information value of the reading passage. For Passage I, 41.4% of all normal nonfluencies occurred on trial one, whereas only 4.7% of all normal nonfluencies occurred on the last reading trial. For Passage II, 28.4% of all normal nonfluencies occurred on trial one, whereas 14.4% of all normal nonfluencies occurred on the last reading trial. In summary, the method of task presentation represents a variable that differentiates stutterers from normal speakers. Whereas stutterers exhibited a smooth, negatively accelerating adaptation curve when provided with a priori information regarding the requirements and limits of the experimental task, the curve deviates from the pattern when no such information is provided. The normal speakers exhibited identical adaptation trends regardless of the method of task presentation. On the other hand, the information value of the reading passage determines the amount and rate of adaptation for both groups of subjects. Massed oral readings of the low information passage yielded greater and more rapid adaptation for stutterers and normal speakers than those adaptation curves obtained with the high information passage. Moreover, with Passage I, and to a lesser degree with Passage II, normal speakers showed greater adaptation than did stutterers. Discussion The Influence of Task Presentation on Adaptation Adaptation trends of stutterers and normal speakers can be differentiated when the treatment variable under consideration is task presentation. For the stutterers, a priori knowledge of the experimental limits and requirements (Condition I) yielded the expected smooth, decelerating adaptation curve; however, when a priori instruction was not provided (Condition II), the curve assumed an uneven shape as the amount of observed stuttering behavior increased from trial one to trial two. These results provide evidence to support the theoretical contention of Forte and Schlesinger (1972) that the shape of the stuttering adaptation curve will be determined by the amount of information given to the stutterer pertaining to the number of times the passage is to be read. In the present study, apriori knowledge of the experimental task included information regarding the number of required readings. The stutterer’s ability to form a gestalt of the total experiment is thus a major factor that determines the regularity or irregularity of the adpatation curve. The data obtained from this portion of the present investigation appear to confirm Wischner’s (1950) explanation of the relationship between general situa-
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M. KROLL
and STEPHEN
B. HOOD
tional anxiety and stuttering adaptation. Subsequent tests of Wischner’s hypothesis have demonstrated that the stuttering adaptation curve is altered when the general reading situation is in any way manipulated prior to, or during, the experimental task. Conversely, when general situational variables are held constant throughout the entire succession of reading trials, the course of the adaptation curve is essentially predictable (Fierman, 1955; Wingate, 1972). It is apparent from the results of the present investigation that the method of task presentation may be regarded as a situational variable which, when varied, alters the course of stuttering adaptation. When the subject is provided with sufficient prior instruction to form a complete perceptual “set” regarding the task at hand, adaptation to the general reading situation follows a smooth course. Results of the data obtained under Condition I can be explained in terms of this proposed model. The subject is presented with a set of complete instructions in addition to a packet containing the required reading material before any speech behavior is accomplished. Thus, the stutterer is fully cognizant of the general situation confronting him and gradually adapts to this unchanging situation with successive oral readings. If the stutterer is not totally aware of the exact nature of the experimental task prior to the oral reading (Condition II), it is conceivable that his perceptual “set” toward the experiment will fluctuate during his performance. That is, if he is simply instructed to read a single passage that is placed in front of him, his set toward the task may be at a particular level; if upon completion of the reading he is instructed to read the passage again, this unexpected command may alter his anticipatory level concerning his initial performance and/or the number of novel task instructions that the experimenter may ask him to engage in during future readings. The subject’s perceptual set thus switches from one of complete awareness of the task requirements to one of uncertainty and anticipation as to the exact nature and limits of the experiment. Under Condition II, the adaptation curve begins to follow the expected negatively accelerating course after reading trial two. The amount of observed stuttering behavior then decreases through trials three, four, and five in a fashion similar to that under Condition I. These findings may be due to the fact that when the stutterer is asked to read the passage a third time, he comes to realize that the experimenter’s instructions may be identical after every reading. His expectations may then be more defined as he becomes somewhat confident of future events. The subject may now begin to perceive the experiment as a whole (in much the same manner as he was able to do under Condition I) and thus his stuttering decreases. The identification of task presentation as a factor affecting stuttering adaptation has important implications for future experimentation in this area. It is essential that identical methods of task presentation be employed in studies attempting to replicate and/or verify past adaptation research. It might also be interesting to
TASK
PRESENTATION,
attempt to identify
INFORMATION
those situational
LOAD,
AND
ADAPTATION
factors that result in abnormal
107
adaptation
curves for normal speakers. In addition to the above theoretical and experimental implications, the variable of task presentation could conceivably be employed clinically with the stutterer. It might be meaningful to observe a stutterer’s adaptation trends under both methods of task presentation so that comparisons can be made regarding the individual’s speech performance under both predictable and uncertain reading situations. For the stutterer whose speech deteriorates under conditions of uncertainty, thereby producing uneven adaptation trends, thereapy might be directed toward increasing this individual’s ability to cope with a variety of unexpected events. If after a period of therapy the stutterer’s adaptation curve for Condition II approximates that for Condition I, the clinician may gain some indication that the stutterer’s reactions to talking and/or reading are approaching those of the normal speaker. For normal speakers massed oral readings under Condition I produced an almost identical adaptation curve to those under Condition II. These results indicate that the situational variable of task presentation has no real effect on the adaptation trends of nonstutterers. These findings can be accounted for by considering both the experimental tasks and the nature of the sample population. Unlike the stutterer, the normal speaker’s attitude toward talking and reading is largely one of indifference. These activities represent everyday occurrences that have never posed any specific problems for the individual. It would, therefore, seem to be of little consequence to the normal speaker whether or not he is provided with a priori information regarding the nature of the reading task. The subject’s performance level is consequently unchanged from Condition I to Condition II. The adaptation curve representative of the normal speaker is, therefore, mainly one of adaptation to the specific linguistic content of the reading passage. Informal questioning of subjects following the experiment seemed to bear out the above proposed models. Twelve of the 14 stutterers indicated that they “felt more anxious” when they were not given any instructions before the task. None of the normal speaking subjects indicated any difference in personal reactions between the two conditions other than that Condition II produced more curiosity pertaining to the purpose of the experiment. Past research that has reported neither qualitative nor quantitative differences between the adaptation trends of stutterers and normal speakers (Sasanuma, 1968; Silverman et al., 1968; Silverman, 1970a,b) must now be disputed on the basis of the situational variable identified in the present investigation. Whereas normal speakers remained essentially unaffected when the situational variable of task presentation was manipulated during the adaptation task, stutterers exhibited dramatic differences when the task presentation was varied. This factor yields quantitative as well as qualitative differences between the adaptation curves of stutterers and normal speakers.
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M. KROLL
and STEPHEN
B. HOOD
The Influence pf Information Load on Adaptation The amount of information in a reading passage, as measured by the cloze procedure, influences the amount and rate of adaptation for both stutterers and normal speakers. A reading passage containing a relatively low amount of conveyed information yields greater and more rapid adaptation than a passage of high information value. The effect of this treatment variable can be observed for both stutterers (Fig. 3) and normal speakers (Fig. 4). Schlesinger et al. (1965) postulated that the phenomenon of adaptation may be accounted for by a reduction in information load with massed oral readings of the same passage. The findings of the present study agree with this theoretical posture as indicated by differences in amounts of adaptation when information load is varied. Less adaptation is observed for the high information passage due to the slower rate of reduction in information load. That is, the subject’s proficiency in prediction proceeds at a relatively slow rate with repeated oral readings due to the high amount of information initially inherent in the passage. Conversely, adaptation occurs more rapidly, and to a greater extent, on the low information passage, as information load decreases rapidly due to the relatively high initial transitional probabilities of specific words and word sequences in the passage. In response to an informal interview conducted following the experimental session, 12 of the 14 stutterers and 11 of the 14 normal speakers indicated that the high information passage was “more difficult to read” than the low information passage. These responses provide further evidence to support the contention that the initial “difficulty” of the passage, which can be operationally defined as its information load, will determine the eventual course of the adaptation curve for both stutterers and normal speakers. The above findings have important experimental implications with regard to verification and/or replication of previous research on adaptation. The results of this study indicate the importance of specifying the information value of experimental reading passages utilized in adaptation studies. Failure to incorporate such data does not allow for verification of previously reported results. Thus, the experimenter should be aware of the importance of disseminating information regarding the complexity or cloze score totals of his reading passages. Wischner’s (1950) theoretical explanation of the adaptation phenomenon includes both linguistic and nonlinguistic variables. That is, the stutterer adapts to both the general speaking situation and to specific words in the reading passage. The results of this study provide powerful evidence to support the hypothesis that both linguistic (information load) and nonlinguistic (task presentation) variables are important determinants of stuttering adaptation. The normal speakers, however, fit only partially into Wischner’s two-factor model of adaptation. For nonstutterers, the linguistic variable of information load is the major determinant
TASK
PRESENTATION,
INFORMATION
LOAD,
AND ADAPTATION
109
of nonfluency adaptation, whereas the situational variable of task presentation does not appear to be important. This study is based on a portion of a doctoral dissertation by Robert Kroll, completed under the directorship of Stephen B. Hood. The authors wish to thank Drs. James Frick, Gerald Moses, and Joseph Stigora for their assistance in gathering subjects. Special appreciation is extended by the senior author to Drs. B. Greenberg, W. Hinkle, M. Hyman, and F. Piggeforserving as members of the doctoral committee. Mrs. Janet Watson did an excellent job typing this manuscript. Requests for reprints should be sent to either author. References Adams,
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