Dynamics of Action and Perception in a Rhythmic Task

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All human behavior entails the continuous interaction between the actor and the environment. This interaction requires an exquisite degree of coordination, often under extremely complex conditions, and we are only just beginning to understand how such coordination is achieved. With funding from the National Science Foundation, Dr. Sternad will examine the performance of a perceptual-motor task in which the complex coordination of actor and environment is distilled in a paradigm suitable for research. The task is the rhythmic bouncing of a ball with a racket. In this task, the actor must continuously coordinate the movements of the racket with the movements of the ball, whose trajectories are in turn determined by the actor. This advantage of this task is that the resulting ball-racket system obeys well-understood physical principles. Moreover, by virtue of being a definable nonlinear dynamical system, it displays characteristic features such as stability and bifurcations. By manipulating the racket, the actor becomes part of this dynamical system and can exploit its properties. Some regimes of the system offer rhythmic solutions with "passive stability", where perturbations converge back onto the attractor without requiring corrective control. Other regimes require active control on the part of actor. Establishing, maintaining, and tuning the regimes of active control rely upon multiple sources of perceptual information. One of the primary aims of this research is to better understand these two general regimes of coordination. The research will also establish national and international collaborations in which both senior investigators and graduate students will participate.