---
title: "Perceptual control theory"
chunk: 1/7
source: "https://en.wikipedia.org/wiki/Perceptual_control_theory"
category: "reference"
tags: "science, encyclopedia"
date_saved: "2026-05-05T03:56:52.953091+00:00"
instance: "kb-cron"
---

Perceptual control theory (PCT) is a model of behavior based on the properties of negative feedback control loops. A control loop maintains a sensed variable at or near a reference value by means of the effects of its outputs upon that variable, as mediated by physical properties of the environment. In engineering control theory, reference values are set by a user outside the system. An example is a thermostat. In a living organism, reference values for controlled perceptual variables are endogenously maintained. Biological homeostasis and reflexes are simple, low-level examples. The discovery of mathematical principles of control introduced a way to model a negative feedback loop closed through the environment (circular causation), which spawned perceptual control theory. It differs fundamentally from some models in behavioral and cognitive psychology that model stimuli as causes of behavior (linear causation). PCT research is published in experimental psychology, neuroscience, ethology, anthropology, linguistics, sociology, robotics, developmental psychology, organizational psychology and management, and a number of other fields. PCT has been applied to design and administration of educational systems, and has led to a psychotherapy called the method of levels.

== Principles and differences from other theories ==
The perceptual control theory is deeply rooted in biological cybernetics, systems biology and control theory and the related concept of feedback loops. Unlike some models in behavioral and cognitive psychology it sets out from the concept of circular causality. It shares, therefore, its theoretical foundation with the concept of plant control, but it is distinct from it by emphasizing the control of the internal representation of the physical world.
The plant control theory focuses on neuro-computational processes of movement generation, once a decision for generating the movement has been taken. PCT spotlights the embeddedness of agents in their environment. Therefore, from the perspective of perceptual control, the central problem of motor control consists in finding a sensory input to the system that matches a desired perception.

== History ==
PCT has roots in the 19th-century physiological insights of Claude Bernard and Walter Bradford Cannon, and in the fields of control systems engineering and cybernetics. Classical negative feedback control was worked out by engineers in the 1930s and 1940s, and further developed by Wiener, Ashby, and others in the early development of the field of cybernetics. Beginning in the 1950s, William T. Powers applied the concepts and methods of engineered control systems to biological control systems, and developed the experimental methodology of PCT.
A key insight of PCT is that the controlled variable is not the output of the system (the behavioral actions), but its input, that is, a sensed and transformed function of some state of the environment that the control system's output can affect. Because these sensed and transformed inputs may appear as consciously perceived aspects of the environment, Powers labelled the controlled variable "perception". The theory came to be known as "Perceptual Control Theory" or PCT rather than "Control Theory Applied to Psychology" because control theorists often assert or assume that it is the system's output that is controlled. In PCT it is the internal representation of the state of some variable in the environment—a "perception" in everyday language—that is controlled. The basic principles of PCT were first published by Powers, Clark, and MacFarland as a "general feedback theory of behavior" in 1960, with credits to cybernetic authors Wiener and Ashby. It has been systematically developed since then in the research community that has gathered around it. Initially, it was overshadowed by the cognitive revolution (later supplanted by cognitive science), but has now become better known.
Powers and other researchers in the field point to problems of purpose, causation, and teleology at the foundations of psychology which control theory resolves. From Aristotle through William James and John Dewey it has been recognized that behavior is purposeful and not merely reactive, but how to account for this has been problematic because the only evidence for intentions was subjective. As Powers pointed out, behaviorists following Wundt, Thorndike, Watson, and others rejected introspective reports as data for an objective science of psychology. Only observable behavior could be admitted as data. Such behaviorists modeled environmental events (stimuli) as causing behavioral actions (responses). This causal assumption persists in some models in cognitive psychology that interpose cognitive maps and other postulated information processing between stimulus and response but otherwise retain the assumption of linear causation from environment to behavior, which Richard Marken called an "open-loop causal model of behavioral organization" in contrast to PCT's closed-loop model.
Another, more specific reason that Powers observed for psychologists' rejecting notions of purpose or intention was that they could not see how a goal (a state that did not yet exist) could cause the behavior that led to it. PCT resolves these philosophical arguments about teleology because it provides a model of the functioning of organisms in which purpose has objective status without recourse to introspection, and in which causation is circular around feedback loops.