Coordination Dynamics

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Many common behaviors require coordinating two limbs rhythmically. These range from the relatively simple coordination of two legs in walking to the very complex coordination of two hands in juggling. These acts of coordination require that the body's very many degrees of freedom--that is, its limbs, joints, muscles, even motor neurons--somehow get harnessed to function as units to accomplish a specific task. This organization displays a rather special flexibility, however: Although stable, it must also be temporary so that those same degrees of freedom can be reorganized, not only in order to accomplish some other specific task (the hands that juggle are also the hands that applaud) but also to allow the system to respond to perturbations (tripping on an uneven sidewalk). The overarching goal of the proposed research is to identify the physical principles that govern the formation, stability, and variability of these kinds of rhythmic organizations or synergies. Over the past decade, our research has contributed to the understanding that movement coordination is usefully and most appropriately addressed as a problem in a particular approach to physics, that of self-organizing systems. The proposed research will use several classes of experiments to explore the idea that the physical basis of common psychological phenomena such as learning, retention, forgetting, attention, and adaptation can be examined using movement coordination as a testing ground. Basic methodologies include requiring participants to swing hand-held pendulums rhythmically, to maintain an upright posture, or to perform cascade juggling. Manipulations (e.g., of participant expertise or handedness; of pendulum lengths and masses, oscillation frequency or phase; the imposition of extraneous tasks; the availability or continuity of visual structure) are motivated by certain expectations of the physical perspective. Three-space motion analyzers and force platforms will be used to collect the data. We pursue the idea that the principles governing movement's coordination are the principles of self-organizing physical systems and that the discovery and expression of these principles will benefit from the tools of nonlinear dynamics. Understanding the physical principles that govern movement's coordination should provide a source of new hypotheses about rhythmic and postural disorders as well as providing constraints on how coordination and its acquisition might be modeled.