body is capable ( Turvey, 1977), one would have a difficult time explaining how countless numbers of motor plans are stored in the central nervous system. Many critics of Adams' theory have suggested that movement must be regulated in a much more parsimonious manner. The answer to this problem may require one to view the items stored as rules for generating the programs instead of storing the programs themselves ( Boylls, 1980) or, as is suggested by Schmidt ( 1976), a generalized motor program for response classes may exist.
Perhaps the major reason the area has turned away from Adams' theory is the difficulty of its application in a broader context. As a theory of motor behavior, it would be hard pressed to explain very complex behaviors such as motor equivalence. Motor equivalence refers to the situation in which similar endproducts are achieved even though different muscle groups have responded: for example, the preservation of individual style whether one writes upon paper or chalkboard ( Greene, 1972; Merton, 1972), or the ability of a smoker to speak intelligibly with a pipe in his mouth ( MacNeilge, 1970). In this context, the endpoint appears unrelated to the movement producing it, clearly a variability not foreseen in Adams' theory. Adams' theory describes very well a limited portion of human motor behavior but is an inadequate explanation for a far greater percentage. Although this condition represents the source of both its strength and its weakness, it accounts for the demise of the theory more than any other reason.
Appreciation and a sincere thanks is extended to Virginia Diggles for her background work and editorial assistance in preparing this chapter.
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