Influence of speaking rate on the upper lip, lower lip, and jaw peak velocity sequencing during bilabial closing movements.

Upper lip, lower lip, and jaw movements were recorded in five adult speakers for repeated sequences of the utterance [bae] at different speech rates. The results failed to confirm several earlier reports of an invariant upper lip, lower lip, jaw peak velocity sequencing pattern for bilabial closures. While the earlier reported sequence was the most frequent, a wide variety of different sequences was also commonly observed. In addition, significant intersubject differences in sequencing were found. The present results thus do not support the earlier hypothesis that oral closure gestures reflect aspects of a centrally generated pattern of motor output during speech.