SPEECH MOTOR COORDINATION AND CONTROL - EVIDENCE FROM LIP, JAW, AND LARYNGEAL MOVEMENTS

The movements of the lower lip, jaw, and larynx during speech were exa mined for two different speech actions involving oral closing for /p/ and oral constriction for /f/. The initial analysis focused on the man ner in which the different speech articulators were coordinated to ach ieve sound production. It was found that the lip, jaw, and laryngeal m ovements were highly constrained in their relative timing apparently t o facilitate their coordination. Differences were noted in the degree to which speech articulator timing covaried dependent on the functiona l characteristics of the action. Movements associated with coordinatin g multiple articulators for a single sound were more highly constraine d in their relative timing than were movements associated with sequenc ing of individual sounds. The kinematic patterns for the different art iculators were found to vary in a number of systematic ways depending on the identity of the sound being produced, the phonetic context surr ounding the target sound, and whether one versus two consonants were p roduced in sequence. The results are consistent with an underlying org anization reflecting the construct of the phoneme. It is suggested tha t vocal tract actions for the sounds of the language are stored in mem ory as motor programs and sequenced together into larger meaningful un its during speaking. Speech articulator motion for the different vowel sounds was found to be influenced by the identity of the following co nsonant, suggesting that speech movements are modified in chunks large r than the individual phonetic segments. It appears that speech produc tion is a hierarchical process with multiple levels of organization tr ansforming cognitive intent into coherent and perceptually identifiabl e sound sequences.