Constancy of interstress intervals in the fluent speech of people who stutter during adaptation trials

The constancy of interstress intervals (ISIs) was studied in the fluent speech of 2 people who stutter during five adaptation trials. Counter to prediction, ISI constancy did not improve as an accompaniment to the reduction of stuttering from Readings 1-5. Overall, the subjects' ISIs were substantially more variable in duration than those of 2 nonstutterers. This was accounted for by the subjects' unusually long ISIs in utterances that placed greater demands on speech motor control processes. Implications for impairment source factors in stuttering are discussed.