The effect of temporal manipulation of disfluency on the perception of stuttering

The purpose of this investigation was to study the effect of temporal features within repetition of speech segments on the perception of stuttering. Past research has provided evidence that certain temporal aspects of repetitions produced by people who stutter tend to be shorter than those produced by normally fluent speakers. The effect of these temporal factors on the perception of the disfluency as "stuttering" or "normal" has not yet been studied.;Conversational speech of five children who stutter and five normally fluent children was recorded. Two short sentences, one containing part-word and one containing whole-word repetition were identified in the speech of each child. The repetitions were manipulated using the CSL system and the Cspeech software. Repetitions were modified creating four levels of pause duration and three levels of vowel duration. Pauses and vowels in the repetitions taken from the stuttering group were lengthened. The duration of the pauses and vowels in the repetitions taken from the normally fluent group were shortened to simulate stuttering.;The following questions were investigated:;(1) Does pause duration within the repetition influence the perception of stuttering? This question examined whether increasing pause duration within repetitions produced by people who stutter causes listeners to identify the disfluency as less representative of stuttering and conversely, whether shortening pause duration within repetitions produced by normally fluent speakers causes listeners to judge these disfluencies as more representative of stuttering.;(2) Does vowel duration within the repetition influence the perception of stuttering? The same reasoning underlying the first question was applied for vowel duration differences. This question examined whether increasing vowel duration within repetitions in the speech of people who stutter causes listeners to judge the disfluency as less representative of stuttering, and if shortening vowel duration within the repetition in the speech of normally fluent speakers causes listeners to judge it as more representative of stuttering.;Results indicated that both factors (pause duration and vowel duration) affected listeners' perception. In general, repetitions with short vowel and pause durations were judged as more representative of stuttering, whereas repetitions with longer vowel and pause duration were judged as more representative of normal speech.