Perceptual control theory

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Perceptual control theory (PCT) is a psychological theory of animal and Human behavior that follows a tradition from Aristotle through William James, a tradition that emphasises the fact that behaviour is purposeful rather than "reactionary". The unaffiliated scientist William T. Powers recognized that to be purposeful implies control, and that the concepts and methods of engineered control systems could be applied to biological control systems. Powers recognized further that in any control system the variable that is controlled is not the output of the system, but a sensed and transformed function of some state of the environment that could be affected by the control system's output. Powers labelled the controlled variable "perception" because some of these sensed and transformed inputs appear as consciously perceived aspects of the environment. Because control theorists often assert or assume that it is the system's output that is controlled rather than the internal representation of a state of the environment -- "perceptions" in everyday language -- Powers's theory came to be known as "Perceptual Control Theory" or PCT rather than "Control Theory Applied to Psychology".

In recognizing the identification of "purpose" with perceptual control, Powers also recognized a problem with the application of control theory to biological systems. Whereas an engineered control system has a reference value or setpoint adjusted by some external agency, the reference value for a biological control system cannot be set in this way. The setpoint must come from some internal process. Powers noted that if an organism controls inappropriate perceptions or controls some perceptions to inappropriate values, it will die, and hence Natural Selection operates to evolve organisms so that they control those perceptions that, when controlled with appropriate setpoints, tend to maintain critical internal variables within non-lethal limits. Powers called these critical internal variables "intrinsic variables", and the mechanism that influences the development of structures of perceptions to be controlled "reorganization". According to Perceptual Control Theory, reorganization within the individual organism is as subject to natural selection as is the evolved structure of individuals within a species.[1]

Perceptual Control Theory has not been widely accepted in mainstream psychology, but has been effectively used in a considerable range of domains[2] in human factors, clinical psychology, and psychotherapy (the "Method of Levels"), and it has formed the conceptual foundation for the reference model used by a succession of NATO research study groups[3].

Introduction

Perceptual control theory is a proposed model of the psychological and behavioral processes occurring within living beings, including humans. It centers on the concept that animals are goal-driven, purposeful entities rather than automata repeating conditioned responses to external stimuli or computers planning commands that will produce desired actions. Behavior, in PCT, is the means by which an organism controls its perceptions, not its actions. 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, but received little general recognition. It is now better known, being taught in several universities worldwide and being the subject of a number of PhD degrees.

A simple negative feedback control system is a cruise control system for a car . A cruise control has a sensor which "perceives" speed as the spin of the drive shaft directly connected to the wheels. It also has a driver-adjustable 'goal' specifying a particular speed. The sensed speed is continuously compared against the specified speed by a device (called a "comparator") which subtracts the currently-sensed input value from the stored goal value. The difference (the error signal) determines the throttle setting (the accelerator depression), so that the engine output is continuously varied to counter variations in the speed of the car. This is just classical negative feedback control as worked out by engineers in the 1930s and 1940s.

If the speed of the car starts to drop below the goal-speed, for example when climbing a hill, the small increase in the error signal, amplified, causes engine output to increase, which keeps the error very nearly at zero. If the speed exceeds the goal, e.g. when going down a hill, the engine is throttled back so as to act as a brake, so again the speed is kept from departing more than a barely-detectable amount from the goal speed (brakes are needed only if the hill is too steep). The result is that the cruise control system maintains a speed close to the goal as the car goes up and down hills, and as other disturbances such as wind affect the car's speed. This is all done without any advance planning of specific actions, and without any blind reactions to stimuli.

The same principles of negative feedback control (including the ability to nullify effects of unpredictable external or internal disturbances) apply to living control systems. The thesis of PCT is that animals and people do not control their behavior; rather, they vary their behavior as their means for controlling their perceptions, with or without external disturbances. This directly contradicts the historical and still widespread assumption that behavior is the final result of stimulus inputs or cognitive plans.

Perceptions, in PCT, are constructed and controlled in a hierarchy of levels. For example, visual perception of an object is constructed from differences in light intensity or differences in sensations such as color at its edges. Controlling the shape or location of the object requires altering the perceptions of sensations or intensities (which are controlled by lower-level systems). This organizing principle is applied at all levels, up to the most abstract philosophical and theoretical constructs.

If there is a way for behavior to affect it, any perception may be brought to the state momentarily specified by higher levels and then be maintained in that state against unpredictable disturbances. In a hierarchy of control systems, higher levels adjust the goals of lower levels as their means of approaching their own goals set by still-higher systems (or at the highest level, by heredity or adaptive processes).

A control system has an organization that controls its input perceptions, but any part of it can be altered by a proposed "reorganization system", part of the inherited structure of the organism. This is the PCT version of "adaptation".

PCT's reorganizing system changes the underlying parameters and connectivity of the control hierarchy in a random-walk manner. There is a basic continuous rate of change in intrinsic variables (Ashby's "essential variables") which proceeds at a speed set by the total error (and stops at zero error), punctuated by random changes in direction in a hyperspace with as many dimensions as there are critical variables. This is a more or less direct adaptation of Ashby's "homeostat", first adopted into PCT in the 1960 paper and then changed to use E. coli's method of navigating up gradients of nutrients, as described by Koshland (1980).

Reorganization may occur at any level when loss of control at that level causes intrinsic (essential) variables to deviate from genetically-determined set points. This is the basic mechanism that is involved in trial-and-error learning, which leads to the acquisition of more systematic kinds of learning processes.<[4]

In a hierarchy of interacting control systems, different systems at one level can send conflicting goals to one lower system. When two systems are specifying different goals for the same lower-level variable, they are in conflict. Protracted conflict is experienced by human beings as many forms of psychological distress such as anxiety, obsession, depression, confusion, and vacillation. Severe conflict destroys control by the affected systems.

Higher level control systems often may be able to use known strategies (themselves acquired through prior reorganizations) to seek perceptions that don't produce the conflict. Normally, this takes place without notice. If the conflict persists and systematic "problem solving" by higher systems fails, the reorganization system may modify existing systems until they bypass the conflict or until they produce new reference signals (goals) that are not in conflict at lower levels.

Success reduces or eliminates the error that is driving reorganization and slows or stops the process with a new organization in place (this is PCT's replacement for the concept of reinforcement learning). New perceptual constructs and new means of controlling the perceptions involved may also result from reorganization. The reorganization process is to vary things until something works, at which point we say that the organism has learned. When done in the right way, this method can be surprisingly efficient in simulations. The reorganization concept has led to a method of psychotherapy called the Method of Levels (MOL) currently being tested in England, the United States, and Australia.

Perceptual control theory currently proposes a hierarchy of 11 levels of perceptions controlled by systems in the human mind and neural architecture. These are: intensity, sensation, configuration, transition, event, relationship, category, sequence, program, principle, and system concept. Diverse perceptual signals at a lower level (e.g. visual perceptions of intensities) are combined in an input function to construct a single perception at the higher level (e.g. visual perception of a color sensation). The perceptions that are constructed and controlled at the lower levels are passed along as the perceptual inputs at the higher levels. The higher levels in turn control by telling the lower levels what to perceive: that is, they adjust the reference levels (goals) of the lower levels. [5]

While many computer demonstrations of principles have been developed, the proposed higher levels are difficult to model because too little is known about how the brain works at these levels. Isolated higher-level control processes can be investigated, but models of an extensive hierarchy of control are still only conceptual, or at best rudimentary.

History

See interviews with William T. Powers under "External links" below.

Research and applications

Selected readings

  • Marken, R.S. (2002). More Mind Readings: Methods and Models in the Study of Purpose. St. Louis: newview. ISBN 0-944337-43-0
  • Powers, W. T. (1988). Making sense of behavior: The meaning of control. New Canan, CT: Benchmark Publications. ISBN 0964712156
  • Runkel, Philip J. (2003). People as living things. Hayward, CA: Living Control Systems Publishing. ISBN 0-9740155-0-4

References

  • Carey, T.A. (2005). The method of levels. Hayward, CA: Living Control Systems Publishing.
  • Goldstein, D.M. (1989a). Q methodology and control systems theory. Operant Subjectivity, 13, 8-14.
  • Goldstein, D.M. (1989b). Control theory applied to stress management. In WA. Hershberger (Ed.), Volitional action (pp. 481-491). Amsterdam: Elsevier.
  • Goldstein, D.M. (1990). Clinical applications of control theory. In R.S. Marken (Ed.), Purposeful behavior: the control theory approach (Theme). American Behavioral Scientist, 34, 2.
  • Goldstein, D.M. (1991). Q methodology and control theory: II. general considerations. Operant Subjectivity, 14, 61-74.
  • Goldstein, D. M. & Goldstein, S. E. (in press). Q Methodology Study of a Peron in Individual Therapy. Clinical Case Studies.
  • Mahrer, A.R. (1989) . The integration of psychotherapies. New York: Human Sciences Press.
  • Marken, R.S. (Ed.). (1990). Purposeful behavior: the control theory approach (Theme) . American Behavioral Scientist, 34, 2.
  • Powers, W.T. (1973). Behavior: The control of perception. Chicago: Aldine.
  • Powers, W.T. (1989). Living control systems: Selected papers of William T. Powers. Gravel Switch, KY: Control Systems Group.
  • Robertson, R.J. & Powers, W.T. (1990). Introduction to modern psychology: the control-theory view. Gravel Switch, KY: Control Systems Group.
  • Robertson, R. J., Goldstein, D.M., Mermel, M., & Musgrave, M. (1999). Testing the self as a control system: Theoretical and methodological issues. Int. J. Human-Computer Studies, 50, 571-580.

Sociology

  • McClelland, Kent. (1994). Perceptual Control and Social Power. Sociological Perspectives, 37, 461-496.
  • McClelland, Kent. (2004). The Collective Control of Perceptions: Constructing Order from Conflict. International Journal of Human-Computer Studies, 60, 65-99.
  • McClelland, Kent and Thomas J. Fararo, eds. (2006). Purpose, Meaning, and Action: Control Systems Theories in Sociology. New York: Palgrave Macmillan.

General references

External links

Notes

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  1. ↑ For an introduction, see the Byte articles on robotics and the article on the origins of purpose in this collection.
  2. ↑ The June 1999 Issue of The International Journal of Human-Computer Studies contained papers ranging from tracking through cockpit layout to self-image and crowd dynamics
  3. ↑ Reports of these groups are available from the NATO Research and Technology Administration publications page <http://www.rta.nato.int/Abstracts.aspx> under the titles RTO-TR-030, RTO-TR-IST-021, and RTO-TR-IST-059
  4. ↑ Cziko, Gary (1995). Without Miracles. 
  5. ↑ Powers, William T. (1973). Behavior: The Control of Perception. Cziko, Gary (1995). Without Miracles. 
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