Coordination, Not Control, Is Central to Movement

Abstract

The notion of the control of action is contrasted with that of coordination. In coordinated action, many parts of the body (or bodies) come together to act as if they served a specific purpose, recognizable as a behavioral goal. Such simpler domains of yoked components are called coordinative structures. Examples are given of the harnessing of components into coordinative structures. In the first case, known as synchronous speech, two speakers are subsumed within a single dyadic domain of organization that exists for as long as the speakers speak in synchrony. In the second case, a time-varying set of articulators work collaboratively in generating natural and fluent movement in accordance with a behavioral goal consisting of a desired utterance. In the latter case, we introduce a new model, extending the venerable task dynamic model familiar to students of articulatory phonology. In the new embodied task dynamic model, precise gestural timing arises, not from computation and control, but from considerations of optimality in movement. A candidate function for optimization combines terms derived from the estimation of articulatory effort, perceptual clarity, and speech rate. Both of these examples illustrate a methodological advantage of dynamical models that demand that the modeler first identify both components and system boundaries as they occur within the context of a specific behavioral goal. This contrasts with many approaches within computational cognitive science.