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Perceptual control theory (PCT) is a model of behavior based on the principles of negative feedback, but differing in important respects from engineering control theory. Results of PCT experiments have demonstrated that an organism controls neither its own behavior, nor external environmental variables, but rather its own perceptions of those variables. Actions are not controlled, they are varied so as to cancel the effects that unpredictable environmental disturbances would otherwise have on controlled perceptions. According to the standard catch-phrase of the field, "behavior is the control of perception". PCT demonstrates circular causation in a negative feedback loop closed through the environment. This fundamentally contradicts the classical notion of linear causation of behavior by stimuli, in which environmental stimuli are thought to cause behavioral responses, mediated (according to Cognitive Psychology) by intervening cognitive processes. Numerous computer simulations of specific behavioral situations demonstrate its efficacy,〔For example in (this collection ).〕 with extremely high correlations to observational data (0.95 or better), such as are routinely expected in physics and chemistry. While the adoption of PCT in the scientific community has not been widespread, it has been applied not only in experimental psychology and neuroscience, but also in sociology, linguistics, and a number of other fields, and has led to a method of psychotherapy called the Method of Levels. PCT has roots in insights of Claude Bernard and 20th century control systems engineering and cybernetics. It was originated as such, and given its present form and experimental methodology, by William T. Powers. ==The place of purpose (intention) and causation in psychology== A tradition from Aristotle through William James recognizes that behavior is ''purposeful'' rather than merely reactive. However, the only evidence for intentions was subjective. Behaviorists following Wundt, Thorndyke, Watson, and others rejected introspective reports as data for an objective science of psychology. Only observable behavior could be admitted as data.〔"The behaviorist asks: Why don't we make what we can observe the real field of psychology? Let us limit ourselves to things that can be observed, and formulate laws concerning only those things. Now what can we observe? We can observe behavior—what the organism does or says." Watson, J.B. (1924). ''Behaviorism''. New York: People's Institute Publishing Company.〕 There follows from this stance the assumption that environmental events (stimuli) cause behavioral actions (responses). This assumption persists in cognitive psychology, which interposes cognitive maps and other postulated information processing between stimulus and response, but otherwise retains the assumption of linear causation from environment to behavior. Another, more specific reason 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. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「perceptual control theory」の詳細全文を読む スポンサード リンク
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