Acoustic and Physiological Reaction Times of Stutterers and Nonstutterers

Abstract

This study investigates reaction times in the fluent speech utterances of stutterers and nonstutterers under several experimental conditions. Twenty adult stutterers and twenty matched controls produced utterances of three lengths—one syllable words, polysyllabic words, and sentences—in two conditions of time pressure (high and low) and two conditions of preparation (delayed and immediate responding) in a reaction-time paradigm. Recordings were made of EMG signals from the orbicularis oris inferior and from the extrinsic laryngeal area, as well as electroglottographic and acoustic signals. Measures were made of the duration of intervals between the stimulus, the acoustical onset of voicing, the onset of laryngeal EMG activity, and the onset of lip EMG activity. The durations of subintervals between the stimulus, the three physiological signals, and the acoustic signal were also measured. The results suggest that the reaction times of stutterers and nonstutterers are both increased by longer utterances, and that the effect is proportionally greater for the stutterers. The requirement to respond with minimal preparation produced longer reaction times in both groups, particularly for longer utterances, but this finding was stronger for stutterers than for nonstutterers, particularly in the prelaryngeal subintervals. The high time-pressure condition produced an unusual pattern of responding in many subjects. The analysis of subintervals indicated that the additional time taken by stutterers in responding was located in the earlier parts of the response, particularly when the utterances were longer. The results are interpreted as suggesting that stutterers may have difficulty in the motor programming of speech behavior.

Speech Production in People Who Stutter: Testing the Motor Plan Assembly Hypothesis

“…Both groups showed a significant increase in reaction time for the polysyllabic words and sentences, but especially for the polysyllabic words (one vs. threeVfour-syllable words) this effect was clearly stronger for the persons who stutter (but see also Young, 1994, for an alternative analysis of these data). Because their data further indicated that the effect was primarily located in the early parts of the reaction time Interval, Peters et al (1989) concluded that their data supported the claim that persons who stutter may have problems in assembling abstract motor plans. More recently, Dembowski and Watson (1991) and Watson, Pool, Devous, Freeman, and Finitzo (1992) were only partially successful in finding the same effect of word size on reaction time differences between persons who do and do not stutter.…”

“…In both studies the equivocal results were attributed to subgroup differences within the experi mental group. However, apart from that, these studies differed in a number of ways from the study, of Peters et al (1989)-for example, in the type and number of stimuli, the duration of intertrial intervals (ITIs), and the type of reaction time task (simple vs. choice).…”

“…To avoid the usual confusion in terminology that arises from words like planning and programming, the first stage will be referred to by motor plan assembly and the second stage by muscle command preparation. Peters et al (1989) argued that the longer verbal reaction times often found in persons who stutter, especially with more complex utterances, relates to increased demands on motor programming, as they called it. Although Peters et al did not precisely specify what stage in speech production i they were referring to, it seems that it comes very close to what is called here motor plan assembly.…”

Persistent developmental stuttering as a cortical-subcortical dysfunction: evidence from muscle activation

“…The influence of the type of task is also observed. Based on the study of Peters et al 9 and on the considerations of Klapp 10 , the RT is greatly influenced by the type of stimulus given at the beginning of processing. Activities involving repetition and reading allow the preprogramming of most motor commands prior to the act of speaking (simple RT).…”

“…The onset of speech has been studied in tasks involving the measurement of speech reaction time (RT) 9,10 . Although a great variability is observed between subjects, this has been described as increased in stutters depending on the type and complexity of the verbal task 11 .…”