Acoustic duration changes associated with two types of treatment for children who stutter

The purpose of this study was (a) to examine in young children the effects of Speech Motor Training (SMT) on selected temporal acoustic durations considered to be related to speech motor programming, (b) to compare the speech motor effects of that treatment with those of a treatment of childhood stuttering that did not directly incorporate speech motor control training (Extended Length of Utterance [ELU]), and (c) to examine the relation of acoustic duration changes to reduction of stuttering. Twelve children who stutter were recorded while repeating syllable sets /see text/ and /see text/ before and after SMT (n = 6) or ELU treatment (n = 6). Children who did not stutter served as matched reference groups. The syllables beginning with /p/ and /t/ were used as tokens for the acoustic measurement. Five measures served as indicators of temporal aspects of speech motor performance: vowel duration, stop gap duration, voice onset time, stop gap/vowel duration ratio, and total token duration. Results indicated that following SMT there was a significant increase in vowel duration and some reduction in stop gap duration that resulted in significantly reduced stop gap/vowel duration ratios. These acoustic effects were consistent across most participants. The ELU treatment reduced stuttering more than the SMT, but was not accompanied by significant effects on the selected temporal acoustic measures. These findings are compared with previous findings of increased vowel durations associated with fluency enhancement and stuttering treatment. We speculate that the increased vowel durations allow more time for speech motor planning and that stuttering is reduced moderately as a by-product of longer vowel durations. The mechanism(s) by which ELU treatment reduces stuttering did not appear to be captured by the dependent variables measured in this study.