A ' Dynamic Pattern ' Perspective on the Control and Coordination of Movement

That speech is the most highly developed motor skill possessed by all of us is a truism, but how is this truism to be understood? Al though the investigation of speech production and motor behavior have proceeded largely independently of each other, they are alike in sharing certain conceptions of how skilled movements are organized. Thus, regardless of whether one refers to movement in general or speech as a particular instance, it is assumed that for coordination to occur, appropriate sets of muscles must be activated in proper relationships to others, and correct amounts of facilitation and inhibi tion have to be delivered to specified muscles. That the production of even the most simple movement involves a multiplicity of neuromuscular events overlapping in time has suggested the need for some type of organizing principle. By far the most favored candidates have been the closed-loop servomechanism accounts provided by cybernetics and its allied disciplines, and the formal machine metaphor of central programs. The evidence for these rival views seems to undergo continuous updating (e.g., Adams, 1977; Keele, 1980) and so will not be of major concern to us here. It is sufficient to point out the current consensus on the issue: namely, that complex sequences of movement may be carried out in the absence of peripheral feedback, but that feedback can be used for monitoring small errors as well as to facilitate corrections in the program itself (e.g., Keele, 1980; Miles & Evarts, 1979).