High Quality Content by WIKIPEDIA articles! High Quality Content by WIKIPEDIA articles! Perceptual control theory (PCT) is a psychological theory of animal and Human behavior originated by unaffiliated scientist William T. Powers. In contrast with other theories of psychology and behavior, which assume that behavior is a function of perception that perceptual inputs determine or cause behavior PCT postulates that an organism's behavior is a means of controlling its perceptions. In contrast with engineering control theory, the reference variable for each negative feedback control loop in a control hierarchy is set from within the system (the organism), rather than by an external agent changing the setpoint of the controller. PCT also applies to nonliving autonomic systems.