Jaw mechanics during release of the stuttering moment: some initial observations and interpretations

As a part of a larger study (Hutchinson and Watkin, 1974), this investigation was undertaken to examine jaw mechanics during the release of stuttering moments. Six adult subjects (four stutters, ranging in severity, and two normal talkers) read a series of sentences containing phonetic sequences requiring jaw depression. Strain-gauge transducers were employed to record articulatory movement. Only those stutterings occurring immediately prior to and during jaw opening were studied. The results confirmed generally faster jaw velocities for the opening and closing gestures; which was interpreted to suggest that the spindle motor system is maximally active to preserve synchrony in on-going vocal tract events following the dysfluency. In cases where an asynchrony between vocalization and jaw opening was noted, it was suggested that imprecision in predicting voice onset resulted in articulatory-laryngeal incoordination. It would appear from these interpretations that the clinical efficacy of the "pull out" procedure results from reduced demands on the gamma loop system and facilitation of articulatory-laryngeal synchrony through reduced supraglottal velocities.