Degrees of Freedom in Behavior

Abstract

Coordinated behavior is typically explained in terms of motor programs or coordinative structures. The experiments described in this report suggest that a better explanation may be provided by control theory. In all experiments, subjects controlled the two-dimensional position of a cursor. By varying the disturbances to the two degrees of freedom of cursor movement, it was possible to elicit task-specific, unidimensional movement patterns resembling coordinative structures. Perturbation of one dimension of the movement pattern failed to produce a concomitant response in the other dimension unless there was a link between the degrees of freedom of action and perception. The subjects' behavior was accurately simulated by the behavior of independent feedback control systems. The results show that the problem of coordinating many degrees of freedom of action can be solved by viewing behavior as control of the perceptual consequences of these actions.