Controlled variables: psychology as the center fielder views it.

Perceptual control theory (PCT) views behavior as the control of perception. The central explanatory concept in PCT is the controlled variable, which is a perceived aspect of the environment that is brought to and maintained in states specified by the organism. According to PCT, understanding behavior is a matter of discovering the variables that organisms control. But the possible existence of controlled variables has been largely ignored in the behavioral sciences. One notable exception occurs in the study of how baseball outfielders catch fly balls. In these studies it is taken for granted that the fielder gets to the ball by controlling some visual aspect of the ball's movement. This article describes the concept of a controlled variable in the context of research on fly ball catching behavior and shows how this concept can contribute to our understanding of behavior in general.