Involvement of head movement in speech production and its implications for language pathology.

Analysis of head movement during speech, monitored by the polarized light goniometer, showed that head movement accompanies speech almost continuously in a manner specific to the concomitant, suprasegmental speech features. Thus initiation of speech after long pauses was accompanied by wide, linear movements (PS). The termination of speech in a pause (terminal juncture) was accompanied by movements of medium amplitudes and frequencies (OM). Sharp, intense movements (RM) were indicative of a peak in loudness, and often of a major phonetic stress. Finally, a speech disturbance was accompanied by movement if it involved a sharp prosodic transition. We suggest that these correlations indicate that head movement may have a role in speech production, regulating the many degrees of freedom and the dissipation of energy in speech. Furthermore, head movements may play a role in linguistic processing through the generative functions of stress, prominence, and orienting responses. Implications for speech pathology, especially dysphasia, are discussed.