The long-term objective of this program is to understand the temporal structuring of speech and manual gestures. A major hypothesis in the present research program is that such an understanding requires a consideration of the dynamics that underlie the spatiotemporal patterning of activity across the task-relevant elements of a speaker's or performer's behavioral repertoire.
Our specific aims are to investigate these dynamics, both empirically and theoretically, by focusing on three major temporal phenomena in both speech production and in the production of simple patterns of finger tapping """"""""gestures."""""""" Knowledge gained from each of these areas will have specific implications for further developments of our task-dynamic model of speech production and its generalization to nonspeech behaviors. The first phenomenon is that local variations in the duration of single elements in a spoken utterance or manual sequence, induced through specification of the element's intrinsic duration or emphatic stress, have systematic but poorly understood effects on the overall global duration of the sequence. Understanding these effects will provide constraints for modeling interactions between central """"""""clock-like"""""""" processes and peripheral """"""""motoric"""""""" events. The second phenomenon is the decrease in pattern stability that occurs during the production of """"""""tongue twisters"""""""" and comparably difficult manual patterns. Of particular interest is the way that instability develops over time. Understanding this effect will provide constraints for modeling the interactions (coupling functions) among simultaneously active gestural units. The third phenomenon is the systematic """"""""signature"""""""" of high level structure (hierarchical prosodic structure in speech; hierarchical rhythmic structure in unimanual tapping) on the kinematics of speech and the kinematics and kinetics of manual activity. Understanding this effect will provide constraints for modeling the means by which high level structure expressively modulates ongoing movements, and how this high level structure is embodied in central clocks or timekeepers. Overall, the research program will provide valuable data and theoretical understanding of the manner in which human skilled activities are structured in time and, hence, will provide valuable clues to movement disorders, such as Parkinson's disease, in which compromised control in the temporal domain is central to the disorder's presentation.
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