Measurement of phonated intervals during four fluency-inducing conditions.

Purpose: Previous investigations of persons who stutter have demonstrated changes in vocalization variables during fluency-inducing conditions (FICs). A series of studies has also shown that a reduction in short intervals of phonation, those from 30 to 200 ms, is associated with decreased stuttering. The purpose of this study, therefore, was to test the hypothesis that the distribution of phonated intervals (PIs) should change during 4 of the most well-known FICs.

Method: A repeated-measures design was used to explore the relationship between PIs and stuttering during 4 FICs: chorus reading, prolonged speech, singing, and rhythmic stimulation. Most conditions were conducted at 2 different speech rates. The distribution of PIs was measured during these conditions and was compared with PI distributions obtained during control conditions.

Results: Overall PI distributions were significantly different during all 4 FICs, as compared with control conditions. PIs in the range of 30-150 ms were reduced across all FICs, at all speech rates.

Conclusion: These results provide further evidence of the importance of phonation variables to (a) our understanding of how FICs may operate and (b) the treatment of stuttering. These findings, along with previous studies that showed how purposefully reducing the number of short PIs resulted in the elimination of stuttering, suggest that treatment programs based on prolonged speech-or PIs, in particular-may benefit from emphasizing a reduction in the number of short PIs and a simultaneous increase in the number of longer PIs.