A control system approach to cardiovascular reactivity: behavioral models that behave.

The control system mode of analysis of organism-environment interactions is described and used to derive an explanation of cardiovascular reactivity. This description reveals that a negative feedback control system continuously realizes a goal or purpose over time by producing output that negates the effects of unpredictable and uncontrollable disturbances on a physical variable corresponding to that purpose. Data from tracking experiments fit the control system analysis, but cannot be described by S-O-R analyses or by cognitive analyses that, unlike the control system analysis, do not correctly introduce physical time. Simple computer simulations of negative feedback control systems produce data that are almost perfectly correlated with each subject's behavior over time--these models behave. The existence of consistent behavioral results despite uncontrollable and unpredictable influences, the simple requirements for a negative feedback system, and the identification of continuously varying purposes as representing the unfolding of behavioral events over time argue for the testable hypothesis that most behavior is produced by negative feedback control. It is suggested that error in the operation of negative feedback control systems modulates cardiac performance. The ability of control systems to behave gives this explanation advantages over other theories of reactivity. A program for testing this explanation is described.