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Decreases in simple reaction time as a function of stutterers' participation in a behavioral therapy
J. FLUENCY DISORD. IO (1985), 301-310
DECREASES IN SIMPLE REACTION TIME AS A FUNCTION OF STUTTERERS’ PARTICIPATION IN A BEHAVIORAL THERAPY DAVID P. HURFORD University of Akron Akron, Ohio
RONALD L. WEBSTER Hollins College Rounoke, Virginia
Stutterers and fluent speakers were compared on a simple reaction time task to determine whether participation in a behaviorally based stuttering program had an effect on clients’ reaction time scores. A group of fluent speakers was used to control the possibility that any changes in reaction time latency were due to practice or familiarity with the task. All participants responded with a finger-lift as quickly as possible to 25 visual stimuli presented by computer. Response latencies from the stutterers and the fluent speakers were compared. Stutterers’ posttherapy reaction time latencies were significantly shorter than their pretherapy latencies. It was also observed that stutterers’ reaction time scores prior to therapy did not differ significantly from fluent speakers’ scores. However, stutterers’ posttherapy reaction time scores did differ significantly from fluent speakers’ posttest scores. The results are discussed in terms of arousal. motivation. familiarity with the environment, conditioned inhibition. and two aspects of therapy.
INTRODUCTION The reaction time paradigm has been a useful tool in the analysis of behavior. As early as 1927 Scripture suggested that the paradigm could be extended to examine neuromuscular speech disorders (Netsell and Daniel, 1974). However, relatively few studies have been performed to directly test this idea. Recently the reaction time paradigm has been used to study stutterers, fluent speakers, or to make comparisons between these two populations (Adams and Hayden, 1976; Brennan and Cullinan, 1976; Cross, 1978; Cross and Luper, 1978; Cullinan and Springer, 1980; Hillman Address correspondence to David Akron. Akron, Ohio 44325.
P. Hut-ford,
0 1985 by Elsevier Science Publishing Co., Inc. 52 Vanderbilt Ave., New York, NY 10017
Department
of Psychology,
University
of
301 0094-730X/85/$03.30
302
D. P. HURFORD
and R. L. WEBSTER
and Gilbert, 1977; Izdebski and Shipp, 1978; Luper and Cross, 1978; McFarlane and Prins, 1978; Netsell and Daniel, 1974; Prosek, 1978; Siegenthaler and Hochberg, 1965; Starkweather, Hirschman, and Tannenbaum, 1976). Most of these studies dealt with voice or speech reaction time. However, a few studies have examined simple manual reaction time (Luper and Cross, 1978; Reich, Till, and Goldsmith, 1981). The majority of the literature, including both speech and nonspeech response time, has suggested that stutterers have longer response latencies than fluent speakers (Andrews, et al., 1983). Reich, Till, and Goldsmith (1981) examined the reaction times of stutterers using forefinger pressing, nonspeech vocal initiation, and speechmode vocal initiation response tasks. They reported that stutterers reaction time scores to auditory stimuli differed significantly only on the phonatory initiation tasks. This finding contradicted the Luper and Cross (1978) study that found that finger-pressing reaction time scores to auditory stimuli were significantly longer in the stuttering group than with matched nonstutterers. The present study was based upon earlier research (Hut-ford, 1981) and was designed to explore the possibility that stutterers have longer manual response latencies to visual stimuli than nonstutterers. A curious observation was made in our laboratory during a test in which posttherapy stutterers had significantly shorter latencies than those of the fluent speakers. The stutterers’ posttherapy latency scores were examined because the therapy was not believed to have a contributing effect on reaction time latencies and because it was convenient to take the measurements at that time. This unexpected finding was initially attributed to either biased sampling techniques or to the fact that the stutterers had just completed an intensive therapy program geared to reduce or abolish stuttering behavior: the Precision Fluency Shaping Program (Webster, 1974). In the course of the program the therapy may have permitted quickening of the reaction time latencies along with decreasing stuttering behavior. The present study explored the possibility that the stutterers’ simple nonspeech reaction time latencies to visual stimulation could be shortened as a function of their participation in treatment. If this phenomenon can be replicated in this study, it may not only aid in determining what aspects of the therapy are producing the effects, but may also shed some empirical light on the etiology of stuttering. In order to rule out other possibilities that could account for the acquisition of shorter posttherapy latencies, the present study used a comparison group not matched for age but comparable, and matched for sex with the stuttering sample. The time interval between pre- and posttest administration was also matched to account for the finding that reaction time latencies decrease with practice and familiarity with the task (Murray, 1970).
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METHOD Participants The 21 stuttering participants in the study were all enrolled in the stuttering therapy program at the Hollins Communications Research Institute (HCRI) at Hollins College located in Roanoke, Virginia. All were men between the ages of 19 and 33 yr. The mean age of this group was 23 yr. The stuttering participants were all judged to be physically normal by way of information gathered in the application procedure for the therapy at HCRI. The comparison group consisted of 21 men associated with Hollins College and the immediate community who were between the ages of 17 and 35 yr. The mean age of this group was 27 yr. The comparison group was carefully selected to include only normally fluent speakers with no history of stuttering. This information was obtained during the recruitment phase.
Apparatus Sets of three Xs (XXX) were displayed on the screen of an interactive display terminal (ADM3-A), which was located on a table in front of the participant. When the Xs appeared on the screen the participant lifted his finger from a red button that was part of a small switchbox located a few inches in front of the terminal. The reaction time information was transmitted to an ERG custom built Z-80, S-IV0 computer (Empirical Research Group, Inc.). After each reaction time score was processed by the computer-it was automatically typed on a printer, without the knowledge of the participant-the next stimulus was presented.
Procedure When the participant first entered the computer room he was instructed to sit in the chair in front of the display terminal while the experimenter read aloud the instructions. The participant was instructed to place his preferred hand in front of the small switchbox so that his index finger rested gently on the red button and depressed it. The experimenter explained to the participant that when a set of three Xs appeared on the terminal he was to release the red button as quickly as he could. The participant was also told that after he responded to the Xs he could take his time redepressing the red button and depressing the space bar so that the computer would present the next set of xs. After questions were answered, the experimenter reviewed the pro-
304
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cedure once again and then began the session by presing the R (RUN) key. The participant then took over the terminal by himself. The stimulus list was comprised of 25 sets of three Xs. Intertrial intervals were randomly determined by the computer and ranged from 7 to 18 sec. It has been reported that reaction time latencies decrease with practice and familiarity with the task (Murray, 1970) and that participants’ variability may be as much as 10% to 13% of their mean reaction time (Steinman and Veniar, 1944). The present study therefore used as dependent variable measures the mean of the ten fastest reaction time latencies and the median reaction time latency per participant to control somewhat for the expected variability in response latencies. The Precision Fluency Shaping Program This behaviorally based program of stuttering therapy is directed at enabling the stutterer to restructure the gestures used in articulation, voicing, and respiration in a manner that approximates the gestures of fluent speakers. The Precision Fluency Shaping Program takes place over a period of 3 wk and uses the teaching and integration of three basic skills: gentle initiation of phonation, diaphragmatic control of respiration, and stabilization of vocal tract shapes (Webster, 1974). RESULTS AND DISCUSSION Analyses using the mean of the ten fastest reaction time latencies were similar to the results of the analyses using the median reaction time latencies; therefore, only the results using the median reaction time latenties are presented. The pre- and posttherapy means for the median reaction time responses for the stuttering group were 238.2 and 214.6 msec, respectively. The means for the median reaction time responses for the pre- and posttests of the comparison group were 246.8 and 250.4 msec, respectively. The results of a two-way analysis of variance with repeated measures on one factor indicated that there were significant differences between groups (stutterers vs. nonstutterers), F(1,40) = 5.8, p < .025, trials (pretherapy and pretest vs. posttherapy and posttest), F(1,40) = 8.3, p < .Ol, and trials x conditions interaction F( 1,40) = 15.4, p < .OO1. Post-hoc analyses with t tests indicated that there were no significant differences between pretherapy scores of the stuttering group and pretest scores of the comparison group, t(40) = 0.8702, p > .lO. However, the stutterers’ posttherapy scores were significantly shorter than the posttest scores of the comparison group, ~(40) = 3.657, p < .Ol. The stutterers’ posttherapy scores were also significantly shorter than their pretherapy scores, t(20)
SIMPLE REACTION TIME AS A FUNCTION OF THERAPY = 5.279, p < .0005. Therefore, the results of the present study replicate the findings of the initial test. The finding that simple visual manual reaction times of pretherapy stutterers and nonstutterers were not significantly different is consistent with the auditory results reported by Reich, Till, and Goldsmith (1981) concerning manual reaction time. Reports by Luper and Cross (1978), however, have indicated that auditory manual reaction times of stutterers were significantly slower than those of nonstutterers. It is possible that simple manual reaction time is quite variable within populations of stutterers and that sample biases are more likely to occur in the studies reported, all of which used relatively small numbers of participants. The extent to which there are real pretherapy reaction time differences between stutterers and nonstutterers appears to depend upon future research involving larger sample sizes. The larger issue raised by this study deals with the finding that reaction time decreased significantly as a function of stutterers’ participation in therapy. Several factors may be responsible for this finding. Increased familiarity with the physical environment may have facilitated reaction time reduction in the stutterers. This possibility is raised on the basis of reports by Conrad (1962), Oldfield and Wingtield (1965), and Smith (1967), who found reaction times to be highly sensitive to familiar cues. Although in the present experiment both stuttering and nonstuttering groups spent the same amount of time in the experimental room and with the experimental apparatus, all stutterers worked for 19 consecutive days in a small clinical building that contained the experimental room. Thus it could be hypothesized that their greater familiarity with the clinic generalized to the experimental room on the basis of its similarity and proximity to the rooms in the building. The appropriate evaluation of this possibility would be to test stutterers and nonstutterers in environments that were at the same level of familiarity for each group. Another possibility was that there may have been an increased arousal level in stutterers who were at the conclusion of a successful 3-wk period of participation in therapy. Excitement resulting from the attainment of improved speech fluency and anticipation of going home could have contributed to an overall increase in arousal level. This interpretation is generally consistent with the reports of Freeman (1940), Levitt and Gutin (1971), and Sjoberg (1975), who found that moderate levels of arousal decreased reaction time latencies. If arousal played a role in the observed decrease in reaction time latencies in the posttherapy stuttering group, one might suspect a higher number of anticipation errors (trials in which the participant responded prior to the presentation of the stimulus) to occur in this group. The mean anticipation errors were as follows for each group: stutterers pretherapy, 0; stutterers posttherapy, 0.02; fluent speakers pretest, 0.01; and fluent speakers posttest, 0.006. A chi-square test
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and R. L. WEBSTER
of homogeneity revealed that the number of anticipation errors between stutterers and fluent speakers was not significantly different, x2( 1) = .178, p > SO. McNemar’s test for related samples found that there were no significant differences between pre- and postanticipation errors, x2( 1) = .154, p > SO. The data, therefore, do not support this hypothesis. The data were further analyzed by examining the actual trials and dividing the stuttering and fluent speaking groups into the following subgroups: stutterers pretherapy, stutterers posttherapy, fluent speakers pretest, and fluent speakers posttest. This was done to examine the hypothesis that higher motivation levels were present in the stuttering posttherapy group. The results of a two-way analysis of variance with repeated measures on one factor indicated that there were significant differences between groups, F(3,80) = 5.6, p < .005, and trials F(24, 345) = 1.7, p < .025, but the trials x conditions interaction was not significant F(72,345) = 0.26, p > .20. The results of an analysis of variance for simple effects indicated that there was not a decreased linear relationship in response latencies across trials: stutterers pretherapy, F(24,345) = 1.02, p > .20; stutterers posttherapy, F(24,345) = 0.28, p > .20; fluent speakers pretest, F(24,345) = 0.84, p > .20; and fluent speakers posttest, F(24,345) = 0.35, p > .20. The data, therefore, do not support the idea that an increase in the stutterers’ motivation resulted in the observed posttherapy decrease in reaction time. If a higher level of motivation was present in the posttherapy stuttering group, a linear decrease in latency should have been found across trials. Not only did this finding fail to materialize, but all the participants verbally expressed a high level of motivation. Further research, however, could control this possibility by testing stutterers and fluent speakers at the end of each of the 3 wk of therapy and noting any changes in response latencies as a function of progress through therapy. If reaction times decrease for week 2 of therapy, a period often associated with reports of reduced motivation and boredom, then the arousal hypothesis would not satisfactorily account for the results. It would also be useful to test stutterers in therapy with stutterers not in therapy, but matched for familiarity with the experimental situation. This possibility is unlikely for economic considerations but would aid in teasing out factors not associated with the observed posttherapy decrease in latency. Conditioned inhibition may also play a role in explaining the results of the present study. It is possible that inhibition of response initiation is a conditioned by-product of the physiological mechanism that constitutes stuttering. This notion is reminiscent of Pavlov’s idea of internal inhibition in which peripheral stimuli were thought to disrupt central processes (Woodworth and Schlosberg, 1954). It is also consistent with Sherrington’s (1947) view that inhibition is a necessary result of two reflexes competing for a common pathway. It is possible that inhibition of response
SIMPLE REACTION
TIME AS A FUNCTION
OF THERAPY
initiation associated with stuttering may also have been generalized from speech to nonspeech responses. A possible mechanism responsible for this effect could involve the hypothesis that stuttering results from a defect in sensory feedback reception associated with speech production (Webster and Lubker, 1968). The basic notion is that the physical consequences that accompany repeated instances of stuttering may have an inhibitory effect on several different response modalities. This condition could have established itself years prior to therapy and may have been responsible for the longer pretherapy reaction time latencies. Extensive utilization of fluency producing skills may have reduced inhibition of response initiation and allowed for the quicker response times observed. Although this general interpretation appears to be rather speculative, it does emphasize the possibility that specific experimental factors that reduce stuttering may also account for the observed posttherapy reaction time decrease in stutterers. In terms of what aspects of the therapy are responsible for the posttherapy decrease in reaction time latencies, a brief logical task analysis is in order. Two aspects of the therapy seem relevant. The first of which concerns the “stretching” of syllable durations. Initially, the client is instructed to expand each and every syllable spoken to 2 sec. This is done with the aid of a 2-set stop watch. After a number of skills have been attained using this 2-set syllable duration, a shorter syllable duration of 1 set is incorporated into the therapy. At the beginning of this syllable duration, the skills acquired during the 2-set syllable duration phase must be stabilized. Once stabilized, new skills are learned. The next syllable duration is &-set syllable duration, and the skills learned at I-see syllable duration must be stabilized here. The last syllable duration learned is that of SIOHJnormal. This syllable duration is concerned with the duration just long enough for the client to still feel the targets. This syllable duration approximates normal speech. One must not get the impression that the Precision Fluency Shaping Program is primarily concerned with the quickening of syllable durations. The therapy teaches the client many target behaviors that must be skillfully learned and maintained at each syllable duration. Although the therapy does not emphasize speed (in fact it discourages this type of emphasis), the decrease in reaction time latencies seen in the stuttering group may be a generalization from a vocal musculature response to a manual response. The second aspect of therapy that may be partially responsible for the effects is the emphasis placed on feeling the relaxed nature of the target behavior. This basically means that the speech muscles are not tense or inappropriately constricted. In combination, these two aspects of therapy seem to be related to the decrease in latency. The client learns to control speech targets at ever decreasing syllable durations and also learns to keep the vocal musculature relaxed. It is possible that both of these ther-
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apy variables could be generalized to other systems of responding. notably the manual response system.
Most
CONCLUSION A significant decrease in stutterers’ visual manual reaction time was observed as a function of their participation in a behaviorally based therapy. A number of hypotheses were introduced to aid in explaining this finding. Two of which, the arousal and the motivation level hypotheses, were statistically invalidated but were not directly tested in the design of the study. Theoretically, the best design would include four separate groups, each tested in an experimental room not associated with HCRI. The four groups would include a stuttering group and a comparison group of nonstutterers each participating in therapy, and a stuttering group and a comparison group of nonstutterers not participating in therapy. With this design, the familiarity of the environment hypothesis would be examined as well as directly testing the role of therapy in decreasing reaction time latencies. However, as mentioned above, this design was not feasible in the present study. In terms of the conditioned inhibition hypothesis put forth in this study, the best possible situation would have reflected reaction times of pretherapy stutterers that were longer than the pretest comparison group, and then the observed decrease in latency for the stuttering group at the end of therapy. The conditioned inhibition hypothesis would intuitively make more sense if this would have occurred. Otherwise, this hypothesis would argue that stutterers, when they no longer stutter, should have shorter reaction time latencies than normally fluent speakers. However, in support of this hypothesis it still remains possible that the physiological mechanism responsible for stuttering may interfere with other modalities. When this physiological mechanism is no longer functioning, other modalities, such as the visual-manual system, may be temporarily augmented so that quicker response times of stutterers might be a landmark of therapy. Although this explanation is speculative, it was not the purpose of this study to completely explain the results, but to verify that they existed. Future research could also examine more closely the relationship between the therapy and the decreased reaction time latencies found in the posttherapy stutterers. Closer examination of these variables may lead to a better understanding of the effectiveness of this particular therapy program and the etiology of stuttering. It is obvious that this study raised far more questions than it answered. Substantially more research is necessary both to confirm the results and to understand the mechanisms that may be responsible for the observed effects. Suggestions made here may aid in guiding further work.
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The authors wish to thank R. E. Sanders and M. D. Murphy for their assistance with the preparation of the manuscript.
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Hillman, R.E. and Gilbert, H.R. Voice onset time for voiceless stop consonants in the fluent reading of stutterers and nonstutterers. Journal of the Acoustical Society of America,
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Hut-ford, D.P. Simple reaction time: Stutterers versus fluent speakers. lished manuscript, Hollins College, Virginia, 1981. Izdebski,
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Murray, H.G. Stimulus intensity and reaction time: Evaluation of a decision theory model. Journal ofExperimental Psychology, 1970, 8, 383-391. Netsell, T. and Daniel, B. Neural and mechanical response time for speech production. Journal of Speech und Hearing Research, 1974, 17, 608-618. Oldfield, R.C. and Wingfield, Journal
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Reich, A., Till, J., and Goldsmith, H. Laryngeal and manual reaction times of stuttering and nonstuttering adults. Journal of Speech and Hearing Research, 1981, 24, 192-196.
Sherrington, C.S. The Integrative action of the nervous system. New Haven: Yale University Press, 1947. Siegenthaler, B.M. and Hochberg, I. Reaction time of the tongue to auditory and tactile stimulation. Perceptual and Motor Skills, 1965, 21, 387-393. Sjoberg, H. Relations between heart rate, reaction speed and subjective effort at different work loads on a bicycle ergometer. Journal of Humun Stress, 1975, 1, 21-27. Smith, E.E. Journal
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DECREASES IN SIMPLE REACTION TIME AS A FUNCTION OF STUTTERERS’ PARTICIPATION IN A BEHAVIORAL THERAPY DAVID P. HURFORD University of Akron Akron, Ohio
RONALD L. WEBSTER Hollins College Rounoke, Virginia
Stutterers and fluent speakers were compared on a simple reaction time task to determine whether participation in a behaviorally based stuttering program had an effect on clients’ reaction time scores. A group of fluent speakers was used to control the possibility that any changes in reaction time latency were due to practice or familiarity with the task. All participants responded with a finger-lift as quickly as possible to 25 visual stimuli presented by computer. Response latencies from the stutterers and the fluent speakers were compared. Stutterers’ posttherapy reaction time latencies were significantly shorter than their pretherapy latencies. It was also observed that stutterers’ reaction time scores prior to therapy did not differ significantly from fluent speakers’ scores. However, stutterers’ posttherapy reaction time scores did differ significantly from fluent speakers’ posttest scores. The results are discussed in terms of arousal. motivation. familiarity with the environment, conditioned inhibition. and two aspects of therapy.
INTRODUCTION The reaction time paradigm has been a useful tool in the analysis of behavior. As early as 1927 Scripture suggested that the paradigm could be extended to examine neuromuscular speech disorders (Netsell and Daniel, 1974). However, relatively few studies have been performed to directly test this idea. Recently the reaction time paradigm has been used to study stutterers, fluent speakers, or to make comparisons between these two populations (Adams and Hayden, 1976; Brennan and Cullinan, 1976; Cross, 1978; Cross and Luper, 1978; Cullinan and Springer, 1980; Hillman Address correspondence to David Akron. Akron, Ohio 44325.
P. Hut-ford,
0 1985 by Elsevier Science Publishing Co., Inc. 52 Vanderbilt Ave., New York, NY 10017
Department
of Psychology,
University
of
301 0094-730X/85/$03.30
302
D. P. HURFORD
and R. L. WEBSTER
and Gilbert, 1977; Izdebski and Shipp, 1978; Luper and Cross, 1978; McFarlane and Prins, 1978; Netsell and Daniel, 1974; Prosek, 1978; Siegenthaler and Hochberg, 1965; Starkweather, Hirschman, and Tannenbaum, 1976). Most of these studies dealt with voice or speech reaction time. However, a few studies have examined simple manual reaction time (Luper and Cross, 1978; Reich, Till, and Goldsmith, 1981). The majority of the literature, including both speech and nonspeech response time, has suggested that stutterers have longer response latencies than fluent speakers (Andrews, et al., 1983). Reich, Till, and Goldsmith (1981) examined the reaction times of stutterers using forefinger pressing, nonspeech vocal initiation, and speechmode vocal initiation response tasks. They reported that stutterers reaction time scores to auditory stimuli differed significantly only on the phonatory initiation tasks. This finding contradicted the Luper and Cross (1978) study that found that finger-pressing reaction time scores to auditory stimuli were significantly longer in the stuttering group than with matched nonstutterers. The present study was based upon earlier research (Hut-ford, 1981) and was designed to explore the possibility that stutterers have longer manual response latencies to visual stimuli than nonstutterers. A curious observation was made in our laboratory during a test in which posttherapy stutterers had significantly shorter latencies than those of the fluent speakers. The stutterers’ posttherapy latency scores were examined because the therapy was not believed to have a contributing effect on reaction time latencies and because it was convenient to take the measurements at that time. This unexpected finding was initially attributed to either biased sampling techniques or to the fact that the stutterers had just completed an intensive therapy program geared to reduce or abolish stuttering behavior: the Precision Fluency Shaping Program (Webster, 1974). In the course of the program the therapy may have permitted quickening of the reaction time latencies along with decreasing stuttering behavior. The present study explored the possibility that the stutterers’ simple nonspeech reaction time latencies to visual stimulation could be shortened as a function of their participation in treatment. If this phenomenon can be replicated in this study, it may not only aid in determining what aspects of the therapy are producing the effects, but may also shed some empirical light on the etiology of stuttering. In order to rule out other possibilities that could account for the acquisition of shorter posttherapy latencies, the present study used a comparison group not matched for age but comparable, and matched for sex with the stuttering sample. The time interval between pre- and posttest administration was also matched to account for the finding that reaction time latencies decrease with practice and familiarity with the task (Murray, 1970).
SIMPLE REACTION
TIME AS A FUNCTION
OF THERAPY
303
METHOD Participants The 21 stuttering participants in the study were all enrolled in the stuttering therapy program at the Hollins Communications Research Institute (HCRI) at Hollins College located in Roanoke, Virginia. All were men between the ages of 19 and 33 yr. The mean age of this group was 23 yr. The stuttering participants were all judged to be physically normal by way of information gathered in the application procedure for the therapy at HCRI. The comparison group consisted of 21 men associated with Hollins College and the immediate community who were between the ages of 17 and 35 yr. The mean age of this group was 27 yr. The comparison group was carefully selected to include only normally fluent speakers with no history of stuttering. This information was obtained during the recruitment phase.
Apparatus Sets of three Xs (XXX) were displayed on the screen of an interactive display terminal (ADM3-A), which was located on a table in front of the participant. When the Xs appeared on the screen the participant lifted his finger from a red button that was part of a small switchbox located a few inches in front of the terminal. The reaction time information was transmitted to an ERG custom built Z-80, S-IV0 computer (Empirical Research Group, Inc.). After each reaction time score was processed by the computer-it was automatically typed on a printer, without the knowledge of the participant-the next stimulus was presented.
Procedure When the participant first entered the computer room he was instructed to sit in the chair in front of the display terminal while the experimenter read aloud the instructions. The participant was instructed to place his preferred hand in front of the small switchbox so that his index finger rested gently on the red button and depressed it. The experimenter explained to the participant that when a set of three Xs appeared on the terminal he was to release the red button as quickly as he could. The participant was also told that after he responded to the Xs he could take his time redepressing the red button and depressing the space bar so that the computer would present the next set of xs. After questions were answered, the experimenter reviewed the pro-
304
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and R. L. WEBSTER
cedure once again and then began the session by presing the R (RUN) key. The participant then took over the terminal by himself. The stimulus list was comprised of 25 sets of three Xs. Intertrial intervals were randomly determined by the computer and ranged from 7 to 18 sec. It has been reported that reaction time latencies decrease with practice and familiarity with the task (Murray, 1970) and that participants’ variability may be as much as 10% to 13% of their mean reaction time (Steinman and Veniar, 1944). The present study therefore used as dependent variable measures the mean of the ten fastest reaction time latencies and the median reaction time latency per participant to control somewhat for the expected variability in response latencies. The Precision Fluency Shaping Program This behaviorally based program of stuttering therapy is directed at enabling the stutterer to restructure the gestures used in articulation, voicing, and respiration in a manner that approximates the gestures of fluent speakers. The Precision Fluency Shaping Program takes place over a period of 3 wk and uses the teaching and integration of three basic skills: gentle initiation of phonation, diaphragmatic control of respiration, and stabilization of vocal tract shapes (Webster, 1974). RESULTS AND DISCUSSION Analyses using the mean of the ten fastest reaction time latencies were similar to the results of the analyses using the median reaction time latencies; therefore, only the results using the median reaction time latenties are presented. The pre- and posttherapy means for the median reaction time responses for the stuttering group were 238.2 and 214.6 msec, respectively. The means for the median reaction time responses for the pre- and posttests of the comparison group were 246.8 and 250.4 msec, respectively. The results of a two-way analysis of variance with repeated measures on one factor indicated that there were significant differences between groups (stutterers vs. nonstutterers), F(1,40) = 5.8, p < .025, trials (pretherapy and pretest vs. posttherapy and posttest), F(1,40) = 8.3, p < .Ol, and trials x conditions interaction F( 1,40) = 15.4, p < .OO1. Post-hoc analyses with t tests indicated that there were no significant differences between pretherapy scores of the stuttering group and pretest scores of the comparison group, t(40) = 0.8702, p > .lO. However, the stutterers’ posttherapy scores were significantly shorter than the posttest scores of the comparison group, ~(40) = 3.657, p < .Ol. The stutterers’ posttherapy scores were also significantly shorter than their pretherapy scores, t(20)
SIMPLE REACTION TIME AS A FUNCTION OF THERAPY = 5.279, p < .0005. Therefore, the results of the present study replicate the findings of the initial test. The finding that simple visual manual reaction times of pretherapy stutterers and nonstutterers were not significantly different is consistent with the auditory results reported by Reich, Till, and Goldsmith (1981) concerning manual reaction time. Reports by Luper and Cross (1978), however, have indicated that auditory manual reaction times of stutterers were significantly slower than those of nonstutterers. It is possible that simple manual reaction time is quite variable within populations of stutterers and that sample biases are more likely to occur in the studies reported, all of which used relatively small numbers of participants. The extent to which there are real pretherapy reaction time differences between stutterers and nonstutterers appears to depend upon future research involving larger sample sizes. The larger issue raised by this study deals with the finding that reaction time decreased significantly as a function of stutterers’ participation in therapy. Several factors may be responsible for this finding. Increased familiarity with the physical environment may have facilitated reaction time reduction in the stutterers. This possibility is raised on the basis of reports by Conrad (1962), Oldfield and Wingtield (1965), and Smith (1967), who found reaction times to be highly sensitive to familiar cues. Although in the present experiment both stuttering and nonstuttering groups spent the same amount of time in the experimental room and with the experimental apparatus, all stutterers worked for 19 consecutive days in a small clinical building that contained the experimental room. Thus it could be hypothesized that their greater familiarity with the clinic generalized to the experimental room on the basis of its similarity and proximity to the rooms in the building. The appropriate evaluation of this possibility would be to test stutterers and nonstutterers in environments that were at the same level of familiarity for each group. Another possibility was that there may have been an increased arousal level in stutterers who were at the conclusion of a successful 3-wk period of participation in therapy. Excitement resulting from the attainment of improved speech fluency and anticipation of going home could have contributed to an overall increase in arousal level. This interpretation is generally consistent with the reports of Freeman (1940), Levitt and Gutin (1971), and Sjoberg (1975), who found that moderate levels of arousal decreased reaction time latencies. If arousal played a role in the observed decrease in reaction time latencies in the posttherapy stuttering group, one might suspect a higher number of anticipation errors (trials in which the participant responded prior to the presentation of the stimulus) to occur in this group. The mean anticipation errors were as follows for each group: stutterers pretherapy, 0; stutterers posttherapy, 0.02; fluent speakers pretest, 0.01; and fluent speakers posttest, 0.006. A chi-square test
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of homogeneity revealed that the number of anticipation errors between stutterers and fluent speakers was not significantly different, x2( 1) = .178, p > SO. McNemar’s test for related samples found that there were no significant differences between pre- and postanticipation errors, x2( 1) = .154, p > SO. The data, therefore, do not support this hypothesis. The data were further analyzed by examining the actual trials and dividing the stuttering and fluent speaking groups into the following subgroups: stutterers pretherapy, stutterers posttherapy, fluent speakers pretest, and fluent speakers posttest. This was done to examine the hypothesis that higher motivation levels were present in the stuttering posttherapy group. The results of a two-way analysis of variance with repeated measures on one factor indicated that there were significant differences between groups, F(3,80) = 5.6, p < .005, and trials F(24, 345) = 1.7, p < .025, but the trials x conditions interaction was not significant F(72,345) = 0.26, p > .20. The results of an analysis of variance for simple effects indicated that there was not a decreased linear relationship in response latencies across trials: stutterers pretherapy, F(24,345) = 1.02, p > .20; stutterers posttherapy, F(24,345) = 0.28, p > .20; fluent speakers pretest, F(24,345) = 0.84, p > .20; and fluent speakers posttest, F(24,345) = 0.35, p > .20. The data, therefore, do not support the idea that an increase in the stutterers’ motivation resulted in the observed posttherapy decrease in reaction time. If a higher level of motivation was present in the posttherapy stuttering group, a linear decrease in latency should have been found across trials. Not only did this finding fail to materialize, but all the participants verbally expressed a high level of motivation. Further research, however, could control this possibility by testing stutterers and fluent speakers at the end of each of the 3 wk of therapy and noting any changes in response latencies as a function of progress through therapy. If reaction times decrease for week 2 of therapy, a period often associated with reports of reduced motivation and boredom, then the arousal hypothesis would not satisfactorily account for the results. It would also be useful to test stutterers in therapy with stutterers not in therapy, but matched for familiarity with the experimental situation. This possibility is unlikely for economic considerations but would aid in teasing out factors not associated with the observed posttherapy decrease in latency. Conditioned inhibition may also play a role in explaining the results of the present study. It is possible that inhibition of response initiation is a conditioned by-product of the physiological mechanism that constitutes stuttering. This notion is reminiscent of Pavlov’s idea of internal inhibition in which peripheral stimuli were thought to disrupt central processes (Woodworth and Schlosberg, 1954). It is also consistent with Sherrington’s (1947) view that inhibition is a necessary result of two reflexes competing for a common pathway. It is possible that inhibition of response
SIMPLE REACTION
TIME AS A FUNCTION
OF THERAPY
initiation associated with stuttering may also have been generalized from speech to nonspeech responses. A possible mechanism responsible for this effect could involve the hypothesis that stuttering results from a defect in sensory feedback reception associated with speech production (Webster and Lubker, 1968). The basic notion is that the physical consequences that accompany repeated instances of stuttering may have an inhibitory effect on several different response modalities. This condition could have established itself years prior to therapy and may have been responsible for the longer pretherapy reaction time latencies. Extensive utilization of fluency producing skills may have reduced inhibition of response initiation and allowed for the quicker response times observed. Although this general interpretation appears to be rather speculative, it does emphasize the possibility that specific experimental factors that reduce stuttering may also account for the observed posttherapy reaction time decrease in stutterers. In terms of what aspects of the therapy are responsible for the posttherapy decrease in reaction time latencies, a brief logical task analysis is in order. Two aspects of the therapy seem relevant. The first of which concerns the “stretching” of syllable durations. Initially, the client is instructed to expand each and every syllable spoken to 2 sec. This is done with the aid of a 2-set stop watch. After a number of skills have been attained using this 2-set syllable duration, a shorter syllable duration of 1 set is incorporated into the therapy. At the beginning of this syllable duration, the skills acquired during the 2-set syllable duration phase must be stabilized. Once stabilized, new skills are learned. The next syllable duration is &-set syllable duration, and the skills learned at I-see syllable duration must be stabilized here. The last syllable duration learned is that of SIOHJnormal. This syllable duration is concerned with the duration just long enough for the client to still feel the targets. This syllable duration approximates normal speech. One must not get the impression that the Precision Fluency Shaping Program is primarily concerned with the quickening of syllable durations. The therapy teaches the client many target behaviors that must be skillfully learned and maintained at each syllable duration. Although the therapy does not emphasize speed (in fact it discourages this type of emphasis), the decrease in reaction time latencies seen in the stuttering group may be a generalization from a vocal musculature response to a manual response. The second aspect of therapy that may be partially responsible for the effects is the emphasis placed on feeling the relaxed nature of the target behavior. This basically means that the speech muscles are not tense or inappropriately constricted. In combination, these two aspects of therapy seem to be related to the decrease in latency. The client learns to control speech targets at ever decreasing syllable durations and also learns to keep the vocal musculature relaxed. It is possible that both of these ther-
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apy variables could be generalized to other systems of responding. notably the manual response system.
Most
CONCLUSION A significant decrease in stutterers’ visual manual reaction time was observed as a function of their participation in a behaviorally based therapy. A number of hypotheses were introduced to aid in explaining this finding. Two of which, the arousal and the motivation level hypotheses, were statistically invalidated but were not directly tested in the design of the study. Theoretically, the best design would include four separate groups, each tested in an experimental room not associated with HCRI. The four groups would include a stuttering group and a comparison group of nonstutterers each participating in therapy, and a stuttering group and a comparison group of nonstutterers not participating in therapy. With this design, the familiarity of the environment hypothesis would be examined as well as directly testing the role of therapy in decreasing reaction time latencies. However, as mentioned above, this design was not feasible in the present study. In terms of the conditioned inhibition hypothesis put forth in this study, the best possible situation would have reflected reaction times of pretherapy stutterers that were longer than the pretest comparison group, and then the observed decrease in latency for the stuttering group at the end of therapy. The conditioned inhibition hypothesis would intuitively make more sense if this would have occurred. Otherwise, this hypothesis would argue that stutterers, when they no longer stutter, should have shorter reaction time latencies than normally fluent speakers. However, in support of this hypothesis it still remains possible that the physiological mechanism responsible for stuttering may interfere with other modalities. When this physiological mechanism is no longer functioning, other modalities, such as the visual-manual system, may be temporarily augmented so that quicker response times of stutterers might be a landmark of therapy. Although this explanation is speculative, it was not the purpose of this study to completely explain the results, but to verify that they existed. Future research could also examine more closely the relationship between the therapy and the decreased reaction time latencies found in the posttherapy stutterers. Closer examination of these variables may lead to a better understanding of the effectiveness of this particular therapy program and the etiology of stuttering. It is obvious that this study raised far more questions than it answered. Substantially more research is necessary both to confirm the results and to understand the mechanisms that may be responsible for the observed effects. Suggestions made here may aid in guiding further work.
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The authors wish to thank R. E. Sanders and M. D. Murphy for their assistance with the preparation of the manuscript.
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