Vocal characteristics of normal speakers and stutterers during choral reading.

It is well known that stutterers experience significant decrements in their stuttering when they read or speak in unison with another person. Recently, Wingate suggested that the act of choral reading or speaking prompts the individual who is following the model speaker to emphasize vocalization and its continuity throughout the utterance. This modified vocalization may then be viewed as the immediate cause of the stutterers' reduced disfluency. To evaluate this hypothesis, ten stutterers and ten normal speakers were tested in a control and choral reading condition. In the former, subjects read in their habitual manner. In the latter, subjects read in unison with a recording of a normal adult male. Subjects' oral readings were audio-taped and then submitted to spectrographic analysis. Measures of vowel duration, peak vocal SPL and continuity of phonation were made and then treated statistically. The major findings of this study indicated that across the two conditions, both groups failed to modify their vocal SPL and continuity of phonation. They did, however, alter their vowel durations. The normal speakers increased theirs by a statistically insignificant amount, while the stutterers significantly shortened theirs. The results that pertained to vocal SPL and vowel durations seemed a function of each group's scores for these measures in the control condition as compared to the values for the same measures that were generated by the model speaker with whom subjects read in unison in the experimental condition. These and other findings and interpretations are discussed further relative to Wingate's "modified vocalization" hypothesis.