Perceptual control theory

Perceptual control theory

Perceptual control theory (PCT) is a psychological theory of animal and Human behavior originated by maverick scientist William T. Powers. In contrast with other theories of psychology and behavior, which assume that behavior is a function of perception — that perceptual inputs determine or cause behavior — PCT postulates that an organism's behavior is a means of controlling its perceptions. In contrast with engineering control theory, the reference variable for each negative feedback control loop in a control hierarchy is set from within the system (the organism), rather than by an external agent changing the setpoint of the controller.Engineering control theory also makes use of feedforward, predictive control, and other functions that are not required to model the behavior of living organisms.] PCT also applies to nonliving autonomic systems.For an introduction, see the "Byte" articles on robotics and the article on the origins of purpose in this [ collection] .]


Perceptual control theory is a testable, comprehensive model of the psychological processes occurring within living beings, including humans, which centers on the concept that animals are goal-driven, purposeful entities rather than automata repeating conditioned responses to external stimuli. Behavior is the means by which the animal controls its perceptions.

Familiar examples of a simple negative feedback control system include a thermostat and a cruise control system. Cruise control has a sensor which "perceives" the speed of the automobile (the speedometer) and an internal, preset 'goal' (the set speed). The sensed input is continuously compared against the goal by a comparatorThe comparator is somewhat misleadingly termed the controller in engineering control theory.] function, which subtracts the sensed input value from the goal value. This is called negative feedback. The difference (the error signal) determines the throttle setting (the accelerator), so that the engine output is continuously varied to counter variations in the speed of the car. If the speed of the car is lower than the goal, for example when climbing a hill, the engine output increases and then gradually declines as the speed approaches the goal; 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, and then as the car slows toward the set speed the engine output is gradually increased. 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.

The same principles of negative feedback control apply to living control systems. Animals and people do not control their behavior, rather, their behavior is their means for controlling their perceptions. This means that perceptions and goals drive the system or organism, not preset behavior patterns as implied by early theories of Behaviorist Psychology. Perceptions are constructed in a hierarchy. For example, visual perception of an edge is constructed from differences in light intensity, perception of the configuration of an object is constructed from edges, and so on, up to the most abstract philosophical and theoretical constructs. Any perception may be brought under control, to maintain it in preferred states. In a hierarchy of control systems, higher levels adjust the goals of lower levels as their means of approaching their own preset goals. Of course a control system has output behaviors that it uses to attempt to control its input perceptions, but these are theorized to be selected for and controlled by a parallel system within the hierarchy, the reorganization system. This changes behavioral outputs of the control systems when the outputs are no longer reducing the 'error' being perceived by the control systems, and it seemingly does this randomly to test and select as many options as possible until a new behavior produces a reducing error signal. Reorganization may occur at any level when control at that level causes error at levels above them.The regression of reference-setting is hypothesized to terminate with intrinsic variables essential to physical survival, such as body temperature and blood sugar in mammals.] This is the mechanism that is involved in learning."Conditioned responses" are obtained by coercive manipulation of controlled variables (usually by food deprivation).] It closely parallels within the individual the processes of evolution by natural selection in the species. [cite book| title=Without Miracles| year=1995| first=Gary| last=Cziko]

In a hierarchy of interacting control systems conflicting outputs and perceptions are possible. When two systems are controlling the same variable with different goals, they are in conflict. When two opposing systems are locked into a static pattern, it is a source of psychological distress. Higher level control systems may seek perceptions that don't produce the conflict. Normally, this takes place without notice. If the conflict persists, the "problem solving" by higher systems comes to awareness, and if it fails the reorganisation system may find new systems that bypass the conflict or may construct new reference signals (goals) that are not in conflict. 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.

Perceptual control theory identifies a hierarchy of at least 11 levels of control 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 an edge). Partial input may suffice to construct the higher-level perception (e.g. partial occlusion of the edge by a shadow). 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 what the lower levels "want" to perceive, that is, they preset the reference levels (goals) of the lower levels. [cite book| title=| year=1973| first=William T.| last=Powerscite book| title=Without Miracles| year=1995| first=Gary| last=Cziko]

This setting of goals or expectations for perceptions that are constructed from diverse inputs at lower levels is a plausible cause of many common optical illusions and cognitive flaws in which expectations influence what is perceived in a situation when sensory input is only partial. A PCT interpretation of recent evidence for "grandmother neurons" storing individual memories in the brain's cortex suggests that a partial stimulation of a memory should produce a 'goal' or expectation of a full perception. An example is when we partially see a face and momentarily perceive it as a familiar face until enough sensory information is received to falsify that expectation and disclose it as a stranger.


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

Research and applications

elected 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


Kinesiology is a technique used by practitioners of complementary medicine to directly address the body-mind's control systems. Sceptics of the technique believe it is an example of the ideomotor effect - the practitioner unwittingly cues desired subconscious reactions in their usually receptive client. The ideomotor effect neatly explains similar unconsciously caused behaviors like the automatic writing produced by use of a Ouija board, and the apparent independent motion of a dowser's dowsing rod. However as a kinesiology practitioner is actually attempting to address the client's subconscious directly, how the ideomotor effect negates this possibility is ambiguous.


(see also the Method of Levels)

This refers to a method of doing individual therapy which is derived from perceptual control theory.

PCT psychotherapy components

The following is a description of PCTP in terms of Dr. Alvin Mahrer's components.

;The useful material to be elicited::The therapist should be concerned with those perceptions(experiences) of a patient which are not being controlled to the patient's satisfaction. The therapist is free to explore any avenue which helps do this. PCTP has no restrictions on what is useful material to be elicited other than it addresses inadequately controlled experiences. It is reasonable to assume that the topics a person wants to talk about will be topics that have error signals associated with them and therefore are stressful for the person.;Listening/observing -- "How to" and "What for"::Powers has proposed a special method of listening/observing which he calls the Method of Levels (MOL). Suppose that the therapist/patient have been discussing topic A for a time period. At an appropriate point in the conversation, the therapist may ask the patient to check for a "topic B" which is any background thought, attitude, reaction, theme, etc., and if present, to talk about it. By doing this, the therapist is drawing attention toward another topic that is already present, although not "stage center." Perhaps the patient is operating from the viewpoint of topic B without being aware of it. Topic B is one that seems to be behind or in the background of the one being discussed. It is up to the patient whether s/he wants to talk about topic B or not.:Suppose that the patient chooses to talk about topic B. As the conversation continues, the therapist may notice that topic C is in the background of the conversation. Either the patient will notice this and start talking about topic C or the therapist will point it out. This process of talking and noticing background topics in the conversation continues. The result of this iterative process is to help the patient direct awareness to the right place in the organization of control systems.:The method of levels describes "how to" listen according to PCT. Powers says that what the therapist should listen for is evidence of the next level up. The therapist listens without preconceptions of what that level is, or whether it is conflicted or not. The idea is to follow the patient's lead.

The Method of Levels (MOL)

Dr. Tim Carey wrote a manual entitled "The Method of Levels". Based on this book, the following guidelines can be given for the therapist:

# Treat the patient with respect and make it clear that the therapist role is to help the patient listen to and observe himself/herself.
# Let the patient choose the initial topic to be discussed.
# Encourage the patient to observe what he/she is experiencing at the moment in the session.
# Notice when the patient reacts to his/her own statements.
# Notice when the patient's body language suggests a reaction to his own statements.
# Talk just enough.
# Listen just enough.
# Do not give the patient an interpretation/explanation of what he/she said.
# Do not give the patient advice or make suggestions.
# Do not become overly involved in the content of what is being discussed.
# Be good at knowing what topic a patient is talking about.
# Be good at noticing when the patient has deviated from the topic he/she is talking about.
# Do not share your own experiences.
# Stop the therapy session when the patient is ready to stop, even if the time originally allotted for the session is not up.
# Ask permission before moving on to a new "higher level" topic.
# Treat the patient as an equal in the therapy process whose preferences are important and are accommodated as much as possible.
# "Stay out of the patient's way" and do not draw him/her off track.
# Be aware when the therapy deviates from the "Pure Vanilla" MOL.Fact|date=June 2008

The area of internal conflicts is theoretically emphasized by Powers. This is because it interferes with the Reorganization System from working at the proper level.

If there is an internal conflict, it will become evident. The therapist, upon encountering a conflict, just keeps going, if possible. The therapist tries to continue until another level comes into view. The conflict should resolve or begin to resolve when the patient directs awareness to the level from which the conflict originates.

An internal conflict exists when a patient wants a perception to be in two incompatible states; the patient wants but doesn't want a certain perception. For example, a person wants to eat in a healthy way but winds up eating too much or eats the wrong things. When a person reaches the appropriate level, the control systems that are responsible for these mutually incompatible goals will become apparent. The person then can come up with a solution which allows better control of the goal. Internal conflict is the main cause of psychological problems in people Powers hypothesizes. This is because awareness is drawn to the wrong place in the organization of control systems by conflict. Conflict results in a person's awareness being drawn too low in the organization of control systems. The reorganization system is working at too low a level and as a result, the person does not resolve the conflict.

As indicated above, the key to resolving a conflict according to Powers is to trace the conflict to the level from which the conflict originates. A patient has to get above the level of the conflicting control systems and see that the goals for these conflicting control systems comes from control systems at a higher level. Upon realizing where the conflict is coming from, the person can make a different choice at the level of the culprit control systems which will eliminate the conflict. If a person tries to resolve the conflict at the level of the conflicting control Systems, then the person will not choose wisely. The conflict will remain and continue to plague the patient. On this basis, Powers is against trying to force a patient to take one side of a conflict and ignore the other side.

; Higher-order description of patient and target of change::In PCT a complete description of a person would consist of the entire hierarchy of perceptions for that person. In that the goal of describing the entire perceptual hierarchy is not usually achievable, the therapist should take a more moderate approach to description. Focusing on selected system (for example, self-image), principle (for example generalizations about the person) and program levels of perception are probably as good as can be achieved.

The methodology to obtain the hierarchy of perceptions consists of clinical discussions with a person in which the Method of Levels and the Test for the Controlled Perception may be employed. The MOL was discussed above.

The test for the controlled perception works as follows. The therapist will do or say something which is intended to change a perception of the patient which the therapist hypothesizes might be a controlled variable. The therapist does or says something that tends to exaggerate or minimize the perception but not change its nature. If the patient does or says something which "undoes" the impact of the therapist and restores the perception to its pre-disturbance value, then this provides some evidence to believe that the perception may be a controlled perception. Instead of introducing the disturbance, the therapist may simply observe the impact of a naturally occurring disturbance. The idea that a person is a perception controlling being implies that resistance or opposition is a normal phenomenon. A control system resists being pushed away from the reference perception state.

The targets of change in PCTP are the control systems which are not controlling satisfactorily. Powers does not believe that it is possible, or advisable, to directly intervene to bring about the identified needed changes. His attitude is that the therapist has to remove the obstacles which are blocking the Reorganization System form working properly. Once the obstacles are removed, the person's own psychological self-healing processes, the Reorganization System, will come into play and bring about the needed changes.

The placing of awareness on the control system(s) which have chronic error signals in them is necessary for the Reorganization System to work. The "observer", which is associated with the Reorganization System, can tune into control systems at any level of the hierarchy, from very concrete to very abstract.

;Therapeutic goals and directions of change::The basic therapeutic goal is to help a person regain control of the problematic life areas so that a person is better controlling experiences.

The better control of experiences is the means by which the person controls body state so as to feel good and to stay healthy.Progress is measured by the increase in control over problematic life areas and the ability of the patient to function independently as the result of participation in therapy. In other words, the job of the therapist is to help a person reach a state in which the help of the therapist is no longer required. The normal self-correcting mechanisms within the person are once again all the person needs. A second, supplemental goal is to provide the patient with the PCT concepts of human nature. In this way, the patient is believed to have a better chance of solving his/her own problems in the future.

Powers suggests that therapists may have been trying to do too much. Therapist should primarily focus our therapeutic efforts at helping people remove the internal conflicts which stop the Reorganization System from bringing about the needed changes in control systems.

; Principles of Therapeutic Change:: The Reorganization System is responsible for changes within the person. The therapist cannot force a patient to change or to change in any specific way. The old joke about the number of psychologists it takes to change a light bulb (one if the light bulb(patient) wants to change) is taken as a truth in PCTP. The Reorganization System is thought of as operating in a trial-and-error, random mode. It comes into play when the acquired control systems are not working to reduce intrinsic error.

A major role of the therapist is to help direct a person's awareness to the right places in the organization of acquired control systems, in the person's "mind." If the Reorganization System is the conductor of a symphony orchestra, and if the musicians in the orchestra are the control systems within a person, the therapist helps the conductor know which musicians to focus on. Once the therapist points the conductor in the right direction, the conductor knows what to do. The therapist help's the person "go-up-a-level" until the person is free to change. The person goes to a point of view in which both sides of a conflict can be viewed and the person can choose new reference signals. As long as the person stays at the level to which conflict attracts awareness, the conflict will not be resolved and will continue. The person will remain stuck.

Once the person is focusing awareness in the right place, the Reorganization System takes over from there. Focusing awareness on a control system can start the reorganization process even without any deliberate intention to change it. In Gestalt therapy this used to be called "paradoxical change" since mere paying attention to something changes what has been paid attention to. In quantum physics it is known as Uncertainty principle. A common example of this is the disruption of a skilled performance when a person directs awareness to the performance.

; General therapeutic stratagems::Mahrer is referring to principle level perceptions which can guide the therapist. These are not spelled out by Powers in any detail. He has made generalizations such as:

*Be mindful of PCT as you work with the patient.
*Educate your patient about the Reorganization System to avoid premature therapy termination.
*Maintain a relationship with the patient which indicates that the patient is an equal and a collaborator.
*Respect the opinion of the patient when it comes to verifying clinical hypotheses.

The point about educating the patient about reorganization is an especially important one. The attitude is communicated that the reorganization system is a friend/self-healing process which is always there when a person's life is out of control. The patient is told that anxious feelings are to be expected during reorganization. The patient may feel worse before s/he feels better and this is the normal course of events in therapy. Many patients have the belief that they will feel immediately better if the therapy is working. We can't rush the Reorganization System. We can direct it to the life areas which are out of control by means of directing awareness. According to meta-emotions model patient internalizes the therapist's meta-interest in the life areas which are out of control and in the spontaneous emotions that are controlled by dysfunctional meta-emotions.

Powers (l979) has suggested that the building a new control system occurs in a certain sequence. The input function is acquired first. A person gains a new ability to perceive. Then the comparator/memory function is acquired. A person develops a preference for one value of the new perceptual variable. Lastly, the output function is acquired. A person learns how to reduce the error signals using the old control systems or with new skills.

These learning ideas have implications for diagnosis and psychotherapy. The development of a symptom, for example, an obsessive-compulsive symptom, might be expected to proceed from perception to action, from obsession to compulsion. If significant others can intervene early when the symptom is at the input function acquisition stage, then maybe they can shorten the life of the symptom.

; Conditions-operations-consequences::If X conditions occur, the therapist will engage Y operations with the expectation that the patient will change in Z way. In PCT terms, these are program level perception statements. PCTP example 1--If a person is experiencing an internal conflict, then the therapist will use the method of levels with the expectation that the patient will resolve the internal conflict.

PCTP example 2--If a person is controlling perception A, and the therapist disturbs perception A in some way, then the patient is expected to say or do something to undo the impact of the therapists actions on perception A.


PCTP is based on the following propositions:

#An adult person comes to therapy because s/he is not able to control experiences to a satisfactory degree.
#Internal conflict is behind most psychological problems that a person is not able to handle on his/her own.
##Internal conflict is best resolved by helping a person become aware of both sides of the conflict. I want to experience "A" and I want to experience "not A." Then it is necessary to trace each side of the conflict to the higher level control systems which are giving the conflicting orders for experiencing..
##The Method of Levels is a good way to do this because it takes a person above the level of the conflict and helps the Reorganization System focus awareness on the control systems that need changing.
#Once the internal conflict is removed, the person's Reorganization System will take care of the rest.
##The perceptions which are out of control will now come under better control.
##The aspects of control which were deficient will correct themselves without a special intervention by the therapist.


*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.


* [ 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

* [ Cziko, Gary.] (1995). "Without miracles: Universal selection theory and the second Darwinian revolution". Cambridge, MA: MIT Press (A Bradford Book). ISBN 0-262-53147-X ( [ Online] )
* [ Cziko, Gary.] (2000). "The things we do: Using the lessons of Bernard and Darwin to understand the what, how, and why of our behavior". Cambridge, MA: MIT Press (A Bradford Book). ISBN 0-262-03277-5 ( [ Online] )
* [ Marken, Richard S.] (1992) "Mind readings: Experimental studies of purpose". Benchmark Publications: New Canaan, CT.
* [ Marken, Richard S.] (2002) "More mind readings: Methods and models in the study of purpose". Chapel Hill, NC: New View.
* [ Powers, William T.] (1973). "Behavior: The control of perception." Chicago: Aldine de Gruyter. ISBN 0-202-25113-6
* [ Powers, William T.] (1998). "Making sense of behavior: The meaning of control." New Canaan, CT: Benchmark Publications. ISBN 0964712156

* Runkel, Philip J. (2003). "People as living things". Hayward, CA: [ Living Control Systems Publishing.] ISBN 0-9740155-0-4

External links

* Articles
** [ Web articles on PCT]
** [ PCT for the Beginner by William T. Powers (2007)]
** [ The Dispute Over Control theory by William T. Powers (1993)]
** [ Demonstrations of perceptual control by Gary Cziko (2006)]
* Audio
** [ Interview with William T. Powers on origin and history of PCT (Part One - 20060722 (58.7M)]
** [ Interview with William T. Powers on origin and history of PCT (Part Two - 20070728 (57.7M)]
* Websites
** [ The Control Systems Group]
** [ Living Control Systems Publishing] - resources and books about PCT
** [ William T. Powers' website]
** [ Mind Readings] - Rick Marken's website on PCTashok kumar


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