Demos and Explanations: Getting Started with PCT

Introductory Articles

Which article should you read? Try one that looks interesting; if it doesn't hold your interest, try another.

The Nature of PCT, by William Powers (1995)

Includes the well-known rubber band demo and a quick vocabulary lesson. A 20-minute talk that gives a brief description of perceptual control theory. read it

PCT in a Nutshell, by Dag Forssell (1994)

PCT introduced from a behavior perspective: "We act to make our wants come true and stay true until we change the want." read it

Understanding Purposeful Behavior, by Dag Forssell (1997)

Defines PCT and hierarchical PCT (HPCT); Uses the example of driving a car. read it

What PCT is about, by William Powers

This introductory paper by William Powers, on his web site, covers a beginning definition of "control", what's wrong with the two prevailing theories of behavior, and how controlling works. Explains the components of a control system and shows and explains the basic PCT control system diagram. Uses the example of driving a car. read it on his site

more articles

Books

Making Sense of Behavior - The Meaning of Control, by William Powers (1998)

A brief (less than 200 pages), non-mathematical summary of PCT authored by its originator, William Powers. Written for the intelligent layperson.

Behavior: The Control of Perception, by William Powers (1973)

This is the 1973 book that started it all. Anyone who is serious about the technical side of perceptual control theory should read it.

Original Book Jacket Text on this site

Table of Contents and Preface on this site

more books & printed articles

Computer Software Demos

There are more demos available at both sites than are listed individually here. These are just to get you started. Feel free to explore more.

Rick Marken's java demos

These are simple to run if you have a java-enabled web browser (note: javascript and java are two different things). If you're not sure, you can try one and see if it works.

• Nature of Control - A tracking task illustrating the basic variables and relationships involved in the process of control.
• Stimulus-Response vs. Control - Shows differences between the stimulus-response model and the perceptual control theory model.
• These and over a dozen more demos are available at http://www.mindreadings.com/demos.htm. They are intended to be run in sequence - you run the first one, then the second one, and so forth, so they make a kind of course.

Bill Powers' demos

These computer programs are for the PC (Windows) only. For more "platform-independent" demos, you might want to look at the list above.

Bill Powers' home page (www.brainstorm-media.com/users/powers_w/) contains several demos created by the originator of perceptual control theory. The descriptions below are taken from longer descriptions on his site; the reader is encouraged to visit it and read the full descriptions. To download and try a demo, go to the site and search for the demo you want; then you can click on the link to download the demos. Most are in .zip format.

If you don't already have a program to uncompress the .zip files, here's one you can try: Ultimate Zip. It's free. Please note that we can't take responsibility for any software you install, but we think it should be fine.

• Demo 1 - The first demo you should try (if you have a PC). This is a self-paced introduction to the phenomenon of control (and control theory). In a series of instructional screens, you're guided through the basics and exerts increasingly informative types of control.
• Demo 2 - A control system block diagram is built up step by step. At each step, you use the mouse to explore the model and change parameters from the keyboard. The program finishes by showing how the behavior of the model can be matched to that of a real person.
• Arm Model - A simulation of a visual-kinesthetic control system: a human arm that reaches out to touch a user-movable target in three dimensions. There's an additional demo Arm with Artificial Cerebellum which makes the model adaptive; given a randomly-moving target, it learns how to reach for it.
• Controlling perceptions in arithmetic learning - Shows that you can indicate the right answer even when there is no correlation between your "response" and the indicated answer. The message: when we solve arithmetic problems, we do not learn to emit motor responses, but to produce controlled perceptions.
• Crowd Simulation - simulates up to 255 individuals moving around on a field.
• Inverted Pendulum Demo - a demonstration of hierarchical control (HPCT).

Again, there are more demos on Powers' site than are listed here.