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Introductions and comments by Bill Powers

10 Minutes
Bill Powers's suggestion for a ten-minute introduction to PCT

A Model for Understanding the
Mechanisms and Phenomena of Control

An introduction to Perceptual Control Theory, contrasting it with basic ideas in contemporary science of psychology.

An Introduction to Perceptual Control Theory
ó Standing at the Crossroads

Many people have some sense of what control is about, but very few understand clearly how control works and even fewer (including control engineers) understand clearly what a control systems controls: Not "output" or "action" but perception of whatever is being controlled; that which action accomplishes. When you stop to think about it, you realize that a control system knows nothing about output or actions; it "knows" only what it senses. The distinction may seem trivial, but the consequences are profound. Bill Powers puts it all in context.

PCT in 11 Steps
An outline of PCT written as a proposal for a series of TV programs.

The Dispute Over Control Theory
Comparing behaviorism, cognitive psych and PCT.
Misapprehensions and misstatements.

Bill Powers on Perceptual Control Theory
About Perceptual Control Theory (PCT), some history, status, and what you will experience when studying PCT. Highlights from an introductory essay William T. (Bill) Powers wrote in May, 1980

What’s wrong with ‘Behavioral Science’?
Letter to Philip J. Runkel, November 8, 1985

The Tank that Filled Itself
or The Road Not Taken to a scientific psychology.

BYTE Articles
The BYTE articles are a book unto themselves
– a four-part introduction to PCT and modeling.


Volition: a Semi-Scientific Essay
Every child wonders, sooner or later, how it is that simply wanting one’s hands, arms, legs, body, head, or eyes to move suffices to create the wanted result.... — So begins this lovely essay and overview of the fundamental issues that cry out for answers.

From Reorganization to Evolution and Back
The concept of reorganization as such is irrefutable, but how can it work? In this essay and final comments, Bill Powers touches on the source and evolution of his thinking over the years.

Reorganization and MOL
A continuation of PCT in 11 Steps, this is an overview of how control systems may come into being, change, cause internal conflict, and ways to resolve internal conflict.

An Essay on the Obvious
A hard-hitting essay by the creator of PCT on what you see when you look at behavior through the eyes of a physical scientist.

Things Iíd like to say if they wouldnít think Iím a nut
Or ó Overgeneralizations that arenít that far over.

Another hard-hitting comment on the state of our contemporary behavioral sciences.

The Neglected Phenomenon of Negative Feedback Control
Control of perception has been reported at very basic levels of life.


The Underpinnings of PCT; Systems Theory and PCT
A discussion of the origin of PCT.

On emotions and PCT: A brief overview
Explaining emotion from a PCT perspective.

Perceptual Control Theory at 40
This intro to PCT is slanted toward those coming into to this subject from the physical sciences. Bill Powers develops an argument that leads from conventional views of behavior to the new view that PCT gives us, emphasizing in the end the odd role that organisms, seen through the eyes of PCT, play in a world otherwise dominated by physical laws. The point will be to show that control theory provides us with the germ of a radically new understanding, a break with all traditional theories of behavior—and many new ones as well

About Stimulus Response Theory
and Perceptual Control Theory

A short post to the Control System Group network (CSGnet) on the difference between cataloging behaviors and modeling systems that use behaviors to control perceptions.

Experience, Reality, and HPCT
A short post to CSGnet on how we think about our senses, our experiences, and how we draw conclusions about the reality we live in (or whether we think we observe reality directly and merely need to report what we observe.

PCT and Scientific Revolutions
A short post to CSGnet with comments on LCS III

CT, PCT, RT, PCT again, MOL, and IAACT
Bill Powers discusses each of these acronyms: Control Theory, Perceptual Control Theory, Reality Therapy, The Method of Levels, and The International Association for Applied Control Theory .

On Computing Output
Notes on the notion that the brain plans our movements and issues commands to muscles, pre-computing the precise muscle movements for people or robots.

A New Muscle Model
If you are going to reverse engineer and then simulate living organisms and how they move about, it is important to simulate all the physics correctly, such as the ray tracing included in the Little Man. Here is a paper that offers significant improvements regarding simulating the actions of muscles.


The origins of purpose: the first metasystem transitions
A proposal that the the emergence of negative feedback control and the emergence of life are the same thing. A picture emerges in which the basic principle of control runs like a unifying thread from the first living molecules to modern complex organisms.

The Reafference Principle and Control Theory
...small changes convert von Holst’s model into a true negative feedback control system. lf we assume with von Holst that a similar architecture holds at higher levels in the nervous system, we have a hierarchy of control systems.


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