Influences of the lower lip on upper-lip movement during speech

Relations between parameters of lower-lip movement and upper-lip movement were investigated during. bilabial opening and closing gestures. Upper- and lower-lip movements of five normal adults were transduced in the inferior-superior dimension with a strain gauge system. Visual feedback of lower-lip movement was employed to manipulate the displacement of the lower lip. Systematic modifications in upper-lip movement were observed as a function of the variation in lower-lip movement. The effects of lower-lip movement on upper-lip movement were larger when the jaw was fixed with a bite block. The temporal relations between lips were maintained at all lower-lip displacements both with and without the bite block. These data will be discussed relative to acoustical, mechanical, and motor control factors that may influence the interactions between lips. [Work supported by NIH.]