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'''Perceptual control theory''' ('''PCT''') is a model of [[behavior]] based on the properties of [[negative feedback]] control loops. A control loop maintains a sensed variable at or near a reference value by means of the effects of its outputs upon that variable, as mediated by physical properties of the environment. In [[Control theory|engineering control theory]], reference values are set by a user outside the system. An example is a thermostat. In a living organism, reference values for controlled perceptual variables are endogenously maintained. Biological [[homeostasis]] and [[reflex]]es are simple, low-level examples. The discovery of mathematical principles of control introduced a way to model a negative feedback loop closed through the environment (circular causation), which differs fundamentally from theories of [[behaviorism]] and [[cognitive psychology]] which model stimuli as causes of behavior (linear causation). PCT research is published in [[experimental psychology]], [[neuroscience]], [[ethology]], [[anthropology]], [[linguistics]], [[sociology]], [[robotics]], [[developmental psychology]], [[organizational psychology]] and management, and a number of other fields. PCT has been applied to design and administration of educational systems, and has led to a psychotherapy called the [[method of levels]].
==History==
PCT has roots in physiological insights of [[Claude Bernard]] and in 20th century [[control systems engineering]] and [[cybernetics]]. Classical negative feedback control was worked out by engineers in the 1930s and 1940s,<ref name="black93">Harold Black and the Negative-Feedback Amplifier, Ronald Kline, IEEE Control Systems Magazine, Aug 1993, Volume 13, Issue 4, Pages 82-85</ref><ref name=Bennett>{{cite journal | last =Bennett | first =Stuart | title =A brief history of automatic control | journal =IEEE Control Systems Magazine | volume =16 | issue =3 | pages =17–25 | date =June 1996 | url =http://ieeecss.org/CSM/library/1996/june1996/02-HistoryofAutoCtrl.pdf | doi =10.1109/37.506394 | access-date =18 July 2016 | archive-url =https://web.archive.org/web/20160809050823/http://ieeecss.org/CSM/library/1996/june1996/02-HistoryofAutoCtrl.pdf | archive-date =9 August 2016 | url-status =dead }}</ref> and further developed by [[Norbert Wiener|Wiener]],<ref name=Wiener48>{{cite book | title =Cybernetics: Or Control and Communication in the Animal and the Machine | publisher =Hermann & Cie | date =1948 | ___location =Paris }} 2nd revised ed. 1961, MIT Press, Cambridge, MA. {{ISBN|978-0-262-73009-9}}.</ref> [[William Ross Ashby|Ashby]],<ref name=Ashby.DFB>{{cite book | last =Ashby | first =
▲<ref name=Ashby.DFB>{{cite book | last =Ashby | first =W[illiam] Ross | title =Design for a Brain | publisher =Chapman & Hall | date =1952 | ___location =London | url =https://archive.org/details/designforbrainor00ashb }}</ref> and others in the early development of the field of [[cybernetics]]. Beginning in the 1950s, [[William T. Powers]] applied the concepts and methods of engineered control systems to biological control systems, and developed the experimental methodology of PCT.<ref name=Runkel.cast>{{cite book | last =Runkel | first =Philip J. | title =Casting nets and testing specimens: Two grand methods of psychology | publisher =Praeger | date =1990 | ___location =New York | page =103 | isbn =978-0-275-93533-7 }}</ref><ref name=Cziko.TWD>{{Citation | last =Cziko | first =Gary | title =The things we do: Using the lessons of Bernard and Darwin to understand the what, how, and why of our behavior | place =Cambridge, MA | publisher =MIT Press | year =2000 | page =[https://archive.org/details/thingswedousingl0000czik/page/9 9] | isbn =978-0-262-03277-3 | url =https://archive.org/details/thingswedousingl0000czik/page/9 }}</ref>
A key insight of PCT is that the controlled variable is not the output of the system (the behavioral actions), but its input, that is, a sensed and transformed function of some state of the environment that the control system's output can affect. Because these sensed and transformed inputs may appear as consciously perceived aspects of the environment, Powers labelled the controlled variable "perception". The theory came to be known as "Perceptual Control Theory" or PCT rather than "Control Theory Applied to Psychology" because control theorists often assert or assume that it is the system's output that is controlled.<ref name=Astrom>{{cite book | last1 =Astrom | first1 =Karl J. | last2 =Murray | first2 =Richard M. | title =Feedback Systems: An Introduction for Scientists and Engineers | publisher =Princeton University Press | date =2008 | url =http://www.cds.caltech.edu/~murray/books/AM08/pdf/am08-complete_28Sep12.pdf | isbn =978-0-691-13576-2 }}</ref> In PCT it is the internal representation of the state of some variable in the environment—a "perception" in everyday language—that is controlled.<ref>For additional information about the history of PCT, see:
* [http://www.pctweb.org/BillPowersAudioInterview1.mp3 Interview with William T. Powers on origin and history of PCT (Part One – 20060722 (58.7M)]
* [http://www.pctweb.org/BillPowersAudioInterview2.mp3 Interview with William T. Powers on origin and history of PCT (Part Two – 20070728 (57.7M)]</ref> The basic principles of PCT were first published by Powers, Clark, and MacFarland as a "general feedback theory of behavior" in 1960,<ref name=PCM1960>{{cite journal | last1 =Powers | first1 =William T. | last2 =Clark | first2 =R.K. | last3 =McFarland | first3 =R.L. | title =A general feedback theory of human behavior (Part I) | journal =Perceptual and Motor Skills | volume =11 | issue =1 | pages =71–88 | date =1960 | doi = 10.2466/pms.1960.11.1.71| s2cid =145256548 }} and {{cite journal | last1 =Powers | first1 =William T. | last2 =Clark | first2 =R.K. | last3 =McFarland | first3 =R.L. | title =A general feedback theory of human behavior (Part II) | journal =Perceptual and Motor Skills | volume =11 | issue =3 | pages =309–323 | date =1960 | doi = 10.2466/pms.1960.11.3.309| s2cid =220712715 }} [Reprinted in {{citation | last1 =Bertalanffy | first1 =Ludwig von | last2 =Rapoport | first2 =Anatol | title =General Systems: Yearbook of the Society for General Systems Research | place =Ann Arbor, Michigan | publisher =Society for General Systems Research | volume =5 | year =1960 }}, pages 63-73, 75-83. Partial reprint in {{cite book | last =Smith | first =A. G. | title =Communication and Culture | publisher =Holt, Rinehart, and Winston | date =1966 | ___location =New York | url =https://archive.org/details/communicationcul00smit| url-access =registration }}]</ref> with credits to cybernetic authors [[Norbert Wiener|Wiener]] and [[William Ross Ashby|Ashby]], and has been systematically developed since then in the research community that has gathered around it.<ref>[http://www.pctresources.com/ Archives of the Control Systems Group (CSG)], also in the [http://discourse.iapct.org/ IAPCT Discourse forum].</ref> Initially, it was overshadowed by the promises of the '[[Cognitive revolution]]', but has now become better known.<ref name="Marken2009rev" /><ref name=Mansell2011>{{cite journal | last =Mansell | first =Warren | title =Control of perception should be operationalized as a fundamental property of the nervous system | journal =Topics in Cognitive Science | volume =3 | issue =2 | pages =257–261 | date =2011 | doi =10.1111/j.1756-8765.2011.01140.x | pmid =25164294 }}</ref><ref name=Mansell.Carey.revolution>{{cite journal | last1 =Mansell | first1 =Warren | last2 =Carey | first2 =Timothy A. | title =A perceptual control revolution? | journal =The Psychologist | publisher =The British Psychological Society | date =28 November 2015 | url =https://thepsychologist.bps.org.uk/volume-28/november-2015/perceptual-control-revolution | access-date =17 July 2016 }}</ref><ref>{{cite book |date=2020 |editor-last=Mansell |editor-first=Warren |title=The Interdisciplinary Handbook of Perceptual Control Theory: Living Control Systems IV |___location=Cambridge |publisher=Academic Press |doi= |isbn=978-0128189481 }}</ref>▼
▲<ref name=PCM1960>{{cite journal | last1 =Powers | first1 =William T. | last2 =Clark | first2 =R.K. | last3 =McFarland | first3 =R.L. | title =A general feedback theory of human behavior (Part I) | journal =Perceptual and Motor Skills | volume =11 | issue =1 | pages =71–88 | date =1960 | doi = 10.2466/pms.1960.11.1.71| s2cid =145256548 }} and {{cite journal | last1 =Powers | first1 =William T. | last2 =Clark | first2 =R.K. | last3 =McFarland | first3 =R.L. | title =A general feedback theory of human behavior (Part II) | journal =Perceptual and Motor Skills | volume =11 | issue =3 | pages =309–323 | date =1960 | doi = 10.2466/pms.1960.11.3.309| s2cid =220712715 }} [Reprinted in {{citation | last1 =Bertalanffy | first1 =Ludwig von | last2 =Rapoport | first2 =Anatol | title =General Systems: Yearbook of the Society for General Systems Research | place =Ann Arbor, Michigan | publisher =Society for General Systems Research | volume =5 | year =1960 }}, pages 63-73, 75-83. Partial reprint in {{cite book | last =Smith | first =A. G. | title =Communication and Culture | publisher =Holt, Rinehart, and Winston | date =1966 | ___location =New York | url =https://archive.org/details/communicationcul00smit| url-access =registration }}]</ref> with credits to cybernetic authors [[Norbert Wiener|Wiener]] and [[William Ross Ashby|Ashby]], and has been systematically developed since then in the research community that has gathered around it.
Powers and other researchers in the field point to problems of purpose, causation, and teleology at the foundations of psychology which control theory resolves.<ref>{{cite journal |last1=Powers |first1=William T. |date=1978 |title=Quantitative analysis of purposive systems: Some spadework at the foundations of scientific psychology |journal=Psychological Review |volume=85 |issue=5 |pages=417–435 |doi=10.1037/0033-295X.85.5.417 }}</ref> From Aristotle through William James and John Dewey it has been recognized that behavior is purposeful and not merely reactive, but how to account for this has been problematic because the only evidence for intentions was subjective. As Powers pointed out, behaviorists following [[Wilhelm Wundt|Wundt]], [[Edward Thorndike|Thorndyke]], [[John B. Watson|Watson]], and others rejected introspective reports as data for an objective science of psychology. Only observable behavior could be admitted as data.<ref>"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.</ref> 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.<ref name=Marken2009rev>{{cite journal | last =Marken | first =Richard S. | title =You say you had a revolution: Methodological foundations of closed-loop psychology | journal =Review of General Psychology | volume =13 | issue =2 | pages =137–145 | date =June 2009 | doi =10.1037/a0015106 | s2cid =145458091 }}</ref>▼
▲</ref> From Aristotle through William James and John Dewey it has been recognized that behavior is purposeful and not merely reactive, but how to account for this has been problematic because the only evidence for intentions was subjective. As Powers pointed out, behaviorists following [[Wilhelm Wundt|Wundt]], [[Edward Thorndike|Thorndyke]], [[John B. Watson|Watson]], and others rejected introspective reports as data for an objective science of psychology. Only observable behavior could be admitted as data.<ref>"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.</ref> 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.<ref name=Marken2009rev>{{cite journal | last =Marken | first =Richard S. | title =You say you had a revolution: Methodological foundations of closed-loop psychology | journal =Review of General Psychology | volume =13 | issue =2 | pages =137–145 | date =June 2009 | doi =10.1037/a0015106 | s2cid =145458091 }}</ref>
Another, more specific reason that Powers observed 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]].<ref name=Runkel-PLT>{{cite book | last =Runkel | first =Philip J. | title =People as living things | publisher =Living Control Systems Publishing | date =2003 | ___location =Hayward, CA | isbn =978-0-9740155-0-7 }}</ref>
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The principal datum in PCT methodology is the controlled variable. The fundamental step of PCT research, the test for controlled variables, begins with the slow and gentle application of disturbing influences to the state of a variable in the environment which the researcher surmises is already under control by the observed organism. It is essential not to overwhelm the organism's ability to control, since that is what is being investigated. If the organism changes its actions just so as to prevent the disturbing influence from having the expected effect on that variable, that is strong evidence that the experimental action disturbed a controlled variable. It is crucially important to distinguish the perceptions and point of view of the observer from those of the observed organism. It may take a number of variations of the test to isolate just which aspect of the environmental situation is under control, as perceived by the observed organism.<ref>{{cite book | last =Runkel | first =Philip J. | title =People as living things | publisher =Living Control Systems Publishing | date =2003 | ___location =Hayward, CA | pages =77–79 | isbn =978-0-9740155-0-7 }}</ref><ref name=marken.center.fielder>{{cite journal | last =Marken | first =Richard S. | title =Controlled variables: psychology as the center fielder views it | journal =American Journal of Psychology | volume =114 | issue =2 | pages =259–281 | date =2001 | jstor =1423517 | doi =10.2307/1423517 | pmid =11430151 | citeseerx =10.1.1.554.9588 }}</ref>
PCT employs a [[black box]] methodology. The controlled variable as measured by the observer corresponds quantitatively to a reference value for a perception that the organism is controlling. The controlled variable is thus an objective index of the purpose or intention of those particular behavioral actions by the organism—the goal which those actions consistently work to attain despite disturbances. With few exceptions, in the current state of [[neuroscience]] this internally maintained reference value is seldom directly observed as such (e.g. as a rate of firing in a neuron), since few researchers trace the relevant electrical and chemical variables by their specific pathways while a living organism is engaging in what we externally observe as behavior.<ref>See e.g.
Data for individuals are not aggregated for statistical analysis;
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===Learning===
Currently, no one theory has been agreed upon to explain the synaptic, neuronal or systemic basis of learning. Prominent since 1973, however, is the idea that [[long-term potentiation]] (LTP) of populations of [[synapse]]s induces learning through both pre- and postsynaptic mechanisms.<ref>{{cite
LTP has received much support since it was first observed by [[Terje Lømo]] in 1966 and is still the subject of many modern studies and clinical research. However, there are possible alternative mechanisms underlying LTP, as presented by Enoki, Hu, Hamilton and Fine in 2009,<ref name="Enoki et al 2009">{{cite journal | last=Enoki | first=Ryosuke | last2=Hu | first2=Yi-ling | last3=Hamilton | first3=David | last4=Fine | first4=Alan | title=Expression of Long-Term Plasticity at Individual Synapses in Hippocampus Is Graded, Bidirectional, and Mainly Presynaptic: Optical Quantal Analysis | journal=Neuron | publisher=Elsevier BV | volume=62 | issue=2 | year=2009 | issn=0896-6273 | doi=10.1016/j.neuron.2009.02.026 | doi-access=free | pages=242–253}}</ref> published in the journal ''[[Neuron (journal)|Neuron]]''. They concede that LTP is the basis of learning. However, they firstly propose that LTP occurs in individual synapses, and this plasticity is graded (as opposed to in a binary mode) and bidirectional.<ref
These theories do agree on one element of LTP, namely, that it must occur through physical changes to the synaptic membrane/s, i.e. synaptic plasticity. Perceptual control theory encompasses both of these views. It proposes the mechanism of [[#Reorganization in evolution, development, and learning|'reorganisation']] as the basis of learning. Reorganisation occurs within the inherent control system of a human or animal by restructuring the inter- and intraconnections of its hierarchical organisation, akin to the neuroscientific phenomenon of neural plasticity. This reorganisation initially allows the trial-and-error form of learning, which is seen in babies, and then progresses to more structured learning through association, apparent in infants, and finally to systematic learning, covering the adult ability to learn from both internally and externally generated stimuli and events. In this way, PCT provides a valid model for learning that combines the biological mechanisms of LTP with an explanation of the progression and change of mechanisms associated with developmental ability
Powers
===Hierarchical organisation===
Botvinick
Recent neuroimaging data has supported the hypothesis that the frontal lobes are organized hierarchically, such that control is supported in progressively caudal regions as control moves to more concrete specification of action. However, it is still not clear whether lower-order control processors are differentially affected by impairments in higher-order control when between-level interactions are required to complete a task, or whether there are feedback influences of lower-level on higher-level control.<ref
Botvinik
Perceptual control theory (PCT) can provide an explanatory model of neural organisation that deals with the current issues. PCT describes the hierarchical character of behavior as being determined by control of hierarchically organized perception. Control systems in the body and in the internal environment of billions of interconnected neurons within the brain are responsible for keeping perceptual signals within survivable limits in the unpredictably variable environment from which those perceptions are derived. PCT does not propose that there is an internal model within which the brain simulates behavior before issuing commands to execute that behavior. Instead, one of its characteristic features is the principled lack of cerebral organisation of behavior. Rather, behavior is the organism's variable means to reduce the discrepancy between perceptions and reference values which are based on various external and internal inputs.<ref>{{cite
Hierarchies of perceptual control have been simulated in computer models and have been shown to provide a close match to behavioral data. For example, Marken<ref name=Marken86>{{cite journal | last =Marken | first =Richard S. | title =Perceptual organization of behavior: A hierarchical control model of coordinated action. | journal =Journal of Experimental Psychology: Human Perception and Performance | volume =12 | issue =3 | pages =267–276 | date =Aug 1986 | doi =10.1037/0096-1523.12.3.267 | pmid =2943855 }}</ref> conducted an experiment comparing the behavior of a perceptual control hierarchy computer model with that of six healthy volunteers in three experiments. The participants were required to keep the distance between a left line and a centre line equal to that of the centre line and a right line. They were also instructed to keep both distances equal to 2 cm. They had 2 paddles in their hands, one controlling the left line and one controlling the middle line. To do this, they had to resist random disturbances applied to the positions of the lines. As the participants achieved control, they managed to nullify the expected effect of the disturbances by moving their paddles. The correlation between the behavior of subjects and the model in all the experiments approached 0.99. It is proposed that the organization of models of hierarchical control systems such as this informs us about the organization of the human subjects whose behavior it so closely reproduces.
==Current situation and prospects==
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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.
Perceptual control theory has not been widely accepted in mainstream psychology, but has been effectively used in a considerable range of domains<ref>{{Cite web | url=https://thepsychologist.bps.org.uk/volume-28/november-2015/perceptual-control-revolution |title = A perceptual control revolution?
==Selected bibliography==
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