The distribution of phonated intervals in the speech of individuals who stutter.

PURPOSE Previous research has demonstrated the fluency-improving effect of reducing the occurrence of short-duration, phonated intervals (PIs; approximately 30-150 ms) in individuals who stutter, prompting the hypothesis that PIs in these individuals' speech are not distributed normally, particularly in the short PI ranges. It has also been hypothesized that this nonnormal PI distribution will be present during the stutter-free speech of affected persons. METHOD A comparison was made between the distributions of PIs during oral reading by adolescent and adult speakers who stuttered (n=13; 11 males) and by age- and gender-matched, normally fluent control participants. RESULTS The results did not support these hypotheses. The results showed that although there were significantly fewer PIs in the speech of the speakers who stuttered (probably because of their slower speaking rate), there was no significant difference between the PI distributions of both speaker groups. This was also true for comparisons between the stutter-free speech of the affected speakers and matched periods of speech produced by the control participants. The PI distributions from both groups were highly correlated. CONCLUSION The null hypothesis findings are discussed in relation to speech-motor- and neurologic-systems explanations for the fluency-inducing effects of reducing short PIs in the speech of individuals who stutter.