VARIANCE OF CENTRAL TIMING OF VOICED AND VOICELESS PERIODS AMONG STUTTERERS AND NONSTUTTERERS

The finding of distinctively greater temporal variability among stutte rers is consistent with the hypothesis that the cause of their speech disruption is related to the excessive variability in their speech mot or system. This hypothesis, would lead to expect that the stutterers' temporal variability would be reduced when they lower their speech rat e, a condition known to reduce the frequency of stuttering. However, c rucial for the variability hypothesis is the contention that the exces sive variability deemed to be causative stems from the central timing mechanism of the speech production system. To find this component of v ariability, that which is due to speech rate variations and that due t o peripheral mechanisms must be separated from the observed total vari ability in segment durations. A procedure to achieve this is outlined. The application of this procedure showed a normalization of the stutt erers' variability during moderate slowing of speech.