Cross, D., and Olson, P. Interaction between jaw kinematics and voice onset for stutterers and nonstutterers in a VRT task. Journal of Fluency Disorders, 1987, 12, 367-380.

The purpose of this study was to investigate the relationship between jaw kinematics and vocal onset of adult stutterers and normal speakers in a voice reaction time task. Ten adult stutterers and ten normal speakers produced /(/ as rapidly as possible in response to twenty-one 1K Hz tones. All responses were initiated with the jaw in a predetermined "closed" position. Results showed that reaction times for both the jaw (JRT) and voice (VRT) were significantly correlated for both groups and that voicing typically began during the final phase of the jaw opening movement. As a group, the stutterers did not differ significantly from the normal speakers for JRT, VRT, or jaw kinematics. Within-group analysis, however, showed that four of the six stutterers exhibited long VRTs and JRTs relative to the distribution of scores for the normal speakers and other stutterers. These subjects also exhibited asynchrony between jaw opening and vocal onset. Results indicate that interaction among upper-articulatory behavior and vocal onset may account, in part, for the long voice reaction times reported for some stutterers.