[From Dick Robertson, 2007.11.19.1640CST]
Hi Rick,
I will tell the guys from Wiley to contact you.
Here is a bad copy of the prior article. The encyclopedia pages havesuch narrow borders that I couldn’t bend the book enough to get all ofthe text into the scan. I have run out of time editing it, but you’llget enough to see what the last one covered.
Here it is
“Perceptual control theory” is a name adopted bya group of scientists interested in the feedback-system organization of humanand animal behavior to distinguish their work from the control theory field ofservo engineers. The members are engaged in the development and applicationofthe thesis advanced in W. T. Powers’s (1973) book, Behavior:
TheControl of Perception. While a majority of this group arepsychologists, it also includes biologists, sociologists, systems engineers,mathematicians, and members of other professions-all finding themselves able tocommunicate with the common language of Powers’s theory, a rather unusualexperience in this age of high specialization.
One member of thegroup, Richard Marken, observed that Powers has not one but two accomplishmentsto his credit. First, he discovered, or noted, that behavior is the control ofperception, contrary to what psychologists have believed ever since Descartes.For Descartes, the environment controlled behavior in the sense that he believedperception of phenomena of the environment stimulates or triggers behavior byentering sensory receptors to set offreflex responses in the organism. Second,Powers developed a theory to explain how behavior does work, showing thatfeedback-control theory can account for how perceptual variables are maintainedagainst external influences! disturbances by control systems, whether inorganisms or robots. The theory he developed finally *provided*a *coherent* mechanismfor the phenomenon of homeostasis, which had been observed much earlier bybiologists but had remained an inexplicable phenomenon.
Although biologists hadgradually accepted self-regulatory-homeostatic-mechanisms after Bernard asapplying to many bodily functions, the idea that the same principles couldaccount for mental phenomena gained ground more slowly. However, beginning inthe 1940s a number of scientists, such as Norbert Wiener, began to suggest thatsuch principles could explain certain aspects of behavior, if not all. Finally,in 1960 the team of W. T. Powers, R. K. Clark, and R. L. McFarland published A General Feedback Theoryof Human Behavior, which presented the first fully comprehensive view of howall behavior could be accounted for by an integrated assembly of hierarchically-orderedfeedback control systems. This work then led to Powers’s 1973 book.
The basic scheme is asfollows. Behavior occurs via a system comprised of a closed feedback loop in which a variable perceptualsignal (PS) is held to a specified value–reference signal (RS)-by the workingsof a comparator (C ). The comparator subtracts the value of the referencesignal from the value of the perceptual signal to obtain an error(ES) that is fed into an output mechanismcapable of affecting the perceptual signal in such a way as to counteract anydisturbance (D) comingfrom the environment. It does so by :’ driving the perceptual signal back toward (maintaining)itat the reference value. The system worksto keep minimizing the error signal, and in so doing it controls thepertinentperceived aspect of the environment as a by product. Peceptualvariables in organisms derive from sensory signals.
Reference signals are previouslystored sensory signals. Output mechanisms are ultimately muscles and glands. Powers pointedout a number of examples of feedback circuitry inneuroanatomy in his book and has continued to find additional anatomicalevidence in his further work.
Figure 1 shows the feedback loop outlined in itssimplest
form.
The same scheme is repeated in hierarchical fasw which thesensory signal is relayed to higher order sys:; and the output ofthe orderabove determines the RS ci order below. This simple schema may be effectively ap;". to a host of everyday behaviors to explain what is hag ing. A popularillustration is the action of driving a car:, driver keeps the car in its laneagainst external dis bances such as wind, curves, bumps, and so forth by toringthe relationship between the front of the car anc: edgeof the road, both of which are perceptual variable:; ducible to a higher ordervariable: the constancy ofrk lationship. The latter is thus the presumptiveperC-E~ signal of interest. It is matched in the brain to the refe! signal;that is, the desired condition of that relation the result being the continualflow of error signals r!::.a::: minimized by the actions of the driver on thesteering. wheel.
Powers showed that this analysis could be quanri£ied in simultaneous equations 5:l1ultaneousequations as PS = ° + D andES =PS - RS, ,.-’:iere D represents a disturbing condition in the environI:'2nt,and 0,the output ofthe system, is some function of ~ as determined by theproperties of the particular sys"L::D… He applied these equations to manydifferent analy!E:oof behavioral phenomena, adding constants as appro~ate to specificsystems, and created a number of com;rc.:er simulations of various types ofbehavior showing that i:::man actions can be imitated by programs using hisfunc-:lUllS, the implication being that if a feedbackmodel, and .~ya feedback model, imitates a humanperformance, it s=:gests that the behavior is feedback controlled.
Theperceptive reader might have noticed in the above that Powers has also solvedthe problem of purpose, or intention, that has been a dilemma forstimulus-response psychologists. It is identical with the reference signal. Thec:r:JITol system realizes what one intends as the organism's rion brings whatis being perceived to match the specifiman that is to be perceived. Powerswent on to propose theoretical answers to many other questions that one might !""'- -eabout the nature of behavior. He sketched out a hierJ!I"'.:nyof control systems to account for the complexity of behavnir, in whichindividual control systems of each level receive their reference signals fromthe output of systems of ttte level above.
Another proposal is that ofan organizing-reorganizing system powered by an intrinsic system comprised ofgenetically determined reference settings. He postulated that if any-readings" in the intrinsic system go into an error state (ie indicatephysical malfunctioning), the reorganizing system would be triggered to injectrandom signaling into ~ control-system hierarchy to bring about changes inneural circuitry which, when successful in controlling some JIFi’ forthat organism) condition, constitutes what we regard. aslearning. His insight was that only random action could afford the chance toproduce a new type of action (in .~2n organism) because any disturbance toconditions al*~iy* under control would immediately benullified by exiJK:.n:g systems. A moment’s reflection leads one toconceive of how thehuman being comes to have a learnedhierarchy in the first place, startingfrom only an intrinsic system of genetically given life-supporting systems atbirth, acting via the reorganizing system upon a growing mass of uncommittedneurons forming and reforming connections as human development proceeds.
O)thermembers of this group have gone on to apply Powers/s analysis to a widevariety of experiments and applica;n:= based upon the idea thatliving organisms do not control Their environments by controlling theiroutputs, but*.* by controlling their inputs-theirperceptions. Much of this work constitutes a significant advance in the testingof hyotheses by quantitative model building and computer simulation rather thanby inferences of causality from correlations, as is commonly practiced incontemporary psy::c: ~)gy. This work can be accessed through the information :0-: CSGnet;the Control Systems Group homepage, http:// ed.uiuc.edu/csg/csg.html; W.T. Powers web site, and thos of manyothers.