Autonomic correlates of stuttering and speech assessed in a range of experimental tasks

Electrodermal activity, peripheral blood flow, and heart rate were recorded from 19 stutterers and 19 normal speakers during performance of jaw movements, a strenuous breath-holding task, reading, and spontaneous speech. The tasks were selected to produce a range of autonomic activation and thus help scale autonomic activation for speech relative to other motor behaviors. Speaking was associated with relatively large increases in autonomic activity in both stutterers and normal speakers. There were no differences between the two groups of speakers, suggesting that the stutterers did not have abnormally high levels of autonomic activation in speech. Within the group of stutterers, the more extreme increases in arousal (specifically increases in measures reflecting sympathetic arousal) were correlated with the occurrence and increased severity of disfluent speech. Significant correlations were found for the intervals prior to, during, and after speech. Although significantly correlated with disfluency, measures of autonomic arousal accounted for small percentages of the variances of fluency and severity. The results are consistent with the hypothesis that sympathetic arousal accompanies the breakdowns in speech motor processes characteristic of stuttering. Mechanisms linking autonomic nervous system functions and somatic sensorimotor processes involved in speech production are discussed.