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JOURNAL OF THE EXPERIMENTAL ANALYSIS OF BEHAVIOR ARE THEORIES OF PERCEPTION NECESSARY? A REVIEW OF GIBSON'S THE ECOLOGICAL APPROACH TO VISUAL PERCEPTION A. P. COSTALL UNIVERSITY OF SOUTHAMPTON, U.K. Representational theories of perception postulate an isolated and automonous "subject" set apart from its real environment, and then go on to invoke processes of mental repre- sentation, construction, or hypothesizing to explain how perception can nevertheless take place. Although James Gibson's most conspicuous contribution has been to challenge rep- resentational theory, his ultimate concern was the cognitivism which now prevails in psy- chology. He was convinced that the so-called cognitive revolution merely perpetuates, and even promotes, many of psychology's oldest mistakes. This review article considers Gibson's final statement of his "ecological" alternative to cognitivism (Gibson, 1979). It is intended not as a complete account of Gibson's alternative, however, but primarily as an apprecia- tion of his critical contribution. Gibson's sustained attempt to counter representational theory served not only to reveal the variety of arguments used in support of this theory, but also to expose the questionable metaphysical assumptions upon which they rest. In concentrating upon Gibson's criticisms of representational theory, therefore, this paper aims to emphasize the point of his alternative scheme and to explain some of the important concerns shared by Gibson's ecological approach and operant psychology. My title, "Are theories of perception neces- sary?," makes an obvious reference to Skinner's paper on theories of learning (Skinner, 1950). But it is also based upon the following passage from James Gibson's (1966) book, The Senses Considered as Perceptual Systems: When the senses are considered as percep- tual systems, all theories of perception be- come at one stroke unnecessary. It is no longer a question of how the mind oper- ates on the deliverances of sense, or how past experience can organize the data, or even how the brain can process the inputs of the nerves, but simply how information is picked up. (p. 319) The point of this double reference is that not only Skinner but also Gibson rejected the kind of "theory" which is now so enthusiasti- cally promoted within cognitive psychology. The intention of their rejection was not, it should be stressed, a denial of any role for the- ory in psychology, but an insistence that be- A version of this paper was presented at the First European Meeting on the Experimental Analysis of Be- haviour, Liege, Belgium, July 26-30, 1983. Requests for reprints should be sent to A. P. Costall, Department of Psychology, The University, Southampton S09 5NH U.K. havior is subject to lawful description in its own right without appeal to "underlying" structures, be they mental, neurological, or quasi-neurological (Gibson, 1966, chapter 13; Skinner, 1938, pp. 3-5; 1969, pp. vii-xii). Gib- son's recent book, The Ecological Approach to Visual Perception, presents his final views on this matter (Gibson, 1979; see especially chap- ter 14). Although cognitive psychologists like to de- fine their approach largely by contrast with what they consider behaviorism, the cognitive approach can nevertheless be characterized by its habitual appeal to internal, "mental" rules and representations, which it treats as exclu- sive and primitive, explanatory terms. Skinner has presented some valuable criticism of the cognitivist program-for example, in his paper in Behaviorism (Skinner, 1977a). But the effec- tiveness of his challenge has been limited not only by his contentious style, but also by his stereotyped role as the villain in cognitivist melodrama. The problem is compounded by a troublesome ambiguity about much of his crit- icism. He keeps shifting the grounds of his at- tack so that sometimes he seems to deny the reality of the mental structure invoked by cog- nitivism, while at other times he appears merely to question their heuristic value in gen- erating research. Increasingly, his arguments 109 1984, 41, 109-115 NUMBER I (JANUARY)

Transcript of James Gibson

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JOURNAL OF THE EXPERIMENTAL ANALYSIS OF BEHAVIOR

ARE THEORIES OF PERCEPTION NECESSARY?A REVIEW OF GIBSON'S THE

ECOLOGICAL APPROACH TO VISUAL PERCEPTION

A. P. COSTALL

UNIVERSITY OF SOUTHAMPTON, U.K.

Representational theories of perception postulate an isolated and automonous "subject"set apart from its real environment, and then go on to invoke processes of mental repre-sentation, construction, or hypothesizing to explain how perception can nevertheless takeplace. Although James Gibson's most conspicuous contribution has been to challenge rep-resentational theory, his ultimate concern was the cognitivism which now prevails in psy-chology. He was convinced that the so-called cognitive revolution merely perpetuates, andeven promotes, many of psychology's oldest mistakes. This review article considers Gibson'sfinal statement of his "ecological" alternative to cognitivism (Gibson, 1979). It is intendednot as a complete account of Gibson's alternative, however, but primarily as an apprecia-tion of his critical contribution. Gibson's sustained attempt to counter representationaltheory served not only to reveal the variety of arguments used in support of this theory,but also to expose the questionable metaphysical assumptions upon which they rest. Inconcentrating upon Gibson's criticisms of representational theory, therefore, this paperaims to emphasize the point of his alternative scheme and to explain some of the importantconcerns shared by Gibson's ecological approach and operant psychology.

My title, "Are theories of perception neces-sary?," makes an obvious reference to Skinner'spaper on theories of learning (Skinner, 1950).But it is also based upon the following passagefrom James Gibson's (1966) book, The SensesConsidered as Perceptual Systems:

When the senses are considered as percep-tual systems, all theories of perception be-come at one stroke unnecessary. It is nolonger a question of how the mind oper-ates on the deliverances of sense, or howpast experience can organize the data, oreven how the brain can process the inputsof the nerves, but simply how informationis picked up. (p. 319)

The point of this double reference is thatnot only Skinner but also Gibson rejected thekind of "theory" which is now so enthusiasti-cally promoted within cognitive psychology.The intention of their rejection was not, itshould be stressed, a denial of any role for the-ory in psychology, but an insistence that be-

A version of this paper was presented at the FirstEuropean Meeting on the Experimental Analysis of Be-haviour, Liege, Belgium, July 26-30, 1983. Requests forreprints should be sent to A. P. Costall, Department ofPsychology, The University, Southampton S09 5NHU.K.

havior is subject to lawful description in itsown right without appeal to "underlying"structures, be they mental, neurological, orquasi-neurological (Gibson, 1966, chapter 13;Skinner, 1938, pp. 3-5; 1969, pp. vii-xii). Gib-son's recent book, The Ecological Approach toVisual Perception, presents his final views onthis matter (Gibson, 1979; see especially chap-ter 14).Although cognitive psychologists like to de-

fine their approach largely by contrast withwhat they consider behaviorism, the cognitiveapproach can nevertheless be characterized byits habitual appeal to internal, "mental" rulesand representations, which it treats as exclu-sive and primitive, explanatory terms. Skinnerhas presented some valuable criticism of thecognitivist program-for example, in his paperin Behaviorism (Skinner, 1977a). But the effec-tiveness of his challenge has been limited notonly by his contentious style, but also by hisstereotyped role as the villain in cognitivistmelodrama. The problem is compounded by atroublesome ambiguity about much of his crit-icism. He keeps shifting the grounds of his at-tack so that sometimes he seems to deny thereality of the mental structure invoked by cog-nitivism, while at other times he appearsmerely to question their heuristic value in gen-erating research. Increasingly, his arguments

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are pragmatic, concerned with the effectivenessof particular kinds of analysis for the purposes

of control. As a result of this ambiguity, cog-

nitive psychologists have felt free to disregardhis metaphysical criticisms and insist thatchoice of means and ends in science is merelya matter of taste. Indeed, cognitive psycholo-gists have felt free to enter the confines of theexperimental analysis of behavior movement

itself, and even to own up to their alien al-legiances.

Cognitivism is under real threat, however,and from within one of its own strongholds,the theory of perception. James Gibson's chal-lenge to the representational theory of percep-

tion has provoked some truly fundamental de-bate within the Establishment journals in thelast couple of years. In this paper I shall try to

explain the nature of his challenge and to ex-

amine both its origins in the behaviorist tra-

dition and some of the important concerns itshares with operant psychology.James Gibson engaged in a sustained attack

upon cognitivism over many years, from thethirties until his death in 1979, and, like Skin-ner, his motives were frankly epistemological(Gibson, 1967; Skinner, 1977b, p. 380; see alsoCostall, 1981; Michaels & Carello, 1981; Reed& Jones, 1982). He credits the behaviorist E. B.Holt as a major influence on his thinking, butafter initially attempting to repair the S-R(stimulus-response) formula promoted by Holt,Gibson eventually came to recognize that per-

ception must be viewed as an act rather thanas a response. Perceptual information, accord-ing to Gibson, is obtained, not imposed (Gib-son, 1979, pp. 56-57, 149-150). But in his recog-

nition that such behavior does not conform tothe classical scheme of reflex psychology, heshared Skinner's conviction that so-called spon-

taneous behavior is nonetheless related to theenvironment in a lawful way (cf. Skinner, 1938,p. 20). His encounters with the Gestalt psy-chologist Kurt Koffka fired his interest in theproblems of perception and reinforced Holt'searlier insight (Holt, 1914, e.g., p. 122) that therepresentational theory of perception presentsa primary target for the attack on cognitivism(Gibson, 1967, 1971).The representational theory of perception is

one of those strange doctrines that most psy-

chologists are convinced they just cannot livewithout. Richard Gregory promotes this doc-

trine with such evident enthusiasm that he notonly lets slip its ultimate absurdities, but actu-ally seems to relish them:

Perceptions are constructed, by complexbrain processes, from fleeting fragmentaryscraps of data signalled by the senses anddrawn from the brain's memory banks-themselves snippets from the past. On thisview, normal everyday perceptions are notpart of-or so directly related to-theworld of external objects as we believe bycommon sense. On this view all percep-tions are essentially fictions; fictions basedon past experience selected by present sen-sory data. (Gregory, 1974, p. xviii)

There is something almost disarming aboutconfusion of this magnitude, a theory whichdenies the possibility of objective knowledgeand then goes on to marshall facts in itssupport. But surely sympathy cannot in itselfexplain why representational theory has per-sisted for so long. As has become increasinglyevident, this paradoxical theory has muchdeeper metaphysical ramifications.While operant psychology takes as unprob-

lematic the fact that organisms can come todetect and discriminate the events occurringwithin their surroundings, the preoccupationof perceptual theory, especially the theory ofvision, has been with how this is possible,given that the organism is in contact not withthe events as such but rather with ambientenergy, such as light or sound. The classicalpuzzle of perceptual theory is that there isnothing in the structure of the immediate stim-ulus which is specific to its source; the sameimage on the retina, for example, would seemto be consistent with an infinite set of possiblecircumstances in the world. Internal represen-tations were invoked to restore in some magi-cal fashion the absence of constraint availablefrom stimulation. Gibson's most conspicuouscontribution has been to question this, themost explicit function of representational the-ory, as a deus ex machina resolving the sup-posed ambiguity of the structures available inambient energy. By urging a molar or higherlevel description of such structures, and bypointing to the constraints which obtain uponsuch structures given the actual environmentin which the organism lives, Gibson, and his

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students, have begun to identify variables instimulation that are uniquely related to envi-ronmental properties and events (see Gibson,1979, chapters 4-8). Strangely enough, however,many cognitivists have eventually come to con-cede Gibson's point about specification-thatis, the existence of information in Gibson'sstrict sense-and yet still persist in their ways(e.g., Palmer, 1978). Quite clearly, representa-tional theory is (to borrow James's commenton Wundt's psychology) like a worm: You cutit up and each fragment crawls. It was Gib-son's persistence in dissecting the cognitivistsystem that enabled him to unmask the variousenchantments of representational theory, thehidden agenda of the current debates.As I mentioned earlier, while developing his

information-based theory of perception, Gib-son came to reject his earlier commitment toS-R theory. He insisted that the organism isactive in a very literal sense in its perceptualexploration of the environment. Gibson, there-fore, like Skinner (e.g., 1969, pp. 3-13, 175; seealso Skinner, 1938), came to abandon the S-Rformula-and has suffered the same fate. Crit-ics simply refuse to believe that he can be any-thing other than a bald proponent of a mecha-nistic behaviorism if he denies that perceptionis an active effort after meaning-active, thatis, in the peculiar sense that cognitive processesmust somehow intervene between the stimulusand the response. It is the very failure of cog-nitive psychologists even to comprehend, letalone answer, the arguments of the oppositionthat indicates that more fundamental issuesare at stake. So let us delve a little more deeply.

Consider another curious statement of therepresentational theory, this time by Fred Att-neave:

Naively, it seems to us that the outsideworld, the world around us, is a given; it isjust there.... We all feel as if our experi-encing of the world around us were quitedirect. However, the apparent immediacyof this experience has to be more or lessillusory because we know that every bit ofour information about external things iscoming through our sense organs, or hascome in through our sense organs at sometime in the past. All of it, to the best ofour knowledge, is mediated by receptoractivity and is relayed to the brain in the

form of Morse code signals, as it were, sothat what we experience as the "realworld", and locate outside ourselves, can-not possibly be anything other than a rep-resentation of the external world. (p. 493)

(I first encountered this passage in a valuablecritique of representational theory by NoelSmith, 1983.)

Interestingly enough, here there is no ap-peal to the usual argument for the ambiguityof perception. Here we find the uncritical re-tention of another aspect of the Cartesianscheme, the notion of a mind lurking withinthe body, in direct contact only with the bodyand not with the environment itself. This no-tion, as Reed has recently argued, derives fromthe Cartesian hypothesis of corporeal ideas(Reed, 1982). Gibson's own criticisms of thisassumption-for example, in his discussion ofthe visual control of manipulation-echo theimportant arguments Skinner has voiced overmany years concerning the persuasive myth ofthe "inner man" (e.g., Skinner, 1938, chap-ter 1):

The movements of the hands do not con-sist of responses to stimuli.... Is the onlyalternative to think of the hands as instru-ments of the mind? Piaget, for example,sometimes seems to imply that the handsare tools of a child's intelligence. But thisis like saying that the hand is a tool of aninner child in more or less the same waythat an object is a tool for a child withhands. This is surely an error. The alter-native is not a return to mentalism. Weshould think of the hands as neither trig-gered nor commanded but controlled.(Gibson, 1979, p. 235)

Unfortunately, the resources of representa-tional theory are not easily exhausted. In itsdefense, it exposes yet further reliance uponthe mechanistic scheme of classical physics. Itsnext resort is to the argument that only an in-stantaneous stimulus can be said to have animmediate effect, or can be considered to enterinto causal or lawful relations. The influenceof past events can enter into an account of be-havior, the argument goes, only insofar as wecan invoke some mediating representationalstructure to fill the gap in time. This plea of

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cognitivism is familiar enough, of course,

though its lineage is not always appreciated.Yet, as Jack Marr (1983) has recently noted:

It is not unlike the old problem in physicsof action at a distance. Newton suggestedthe possibility . . . that an all-pervading"aether" served as the medium for suchphenomena as gravitation and light. Psy-chology has been replete with mentalaethers that mediate between stimuli andresponses. Indeed, cognitive psychologyseems to be paralleling classical physicsin the search for an understanding of thestructure and mechanics of the mentalaether. The mental aether must have theproperty of mediating action at a tempo-ral distance. (p. 13)

It is evidently not enough to insist, as Skin-ner does, that appeal to cognitive structures isunnecessary, or a "diversion" (Skinner, 1977a,p. 10), in the sense that we can conduct re-

search and solve problems perfectly well with-out them. The argument that such structurescan be disregarded does not in itself call intoquestion their very existence, and indeed Skin-ner at times talks as if they might well existafter all. What we require is an alternativescheme that does not merely question the solu-tions put forward by cognitive psychologistsbut converts their very problems from implicitto conspicuous nonsense. It is in Gibson's finalwork towards such an alternative scheme, a

new ontology, that his fundamental impor-tance for psychology really lies.

Gibson, like Skinner, viewed science not as

some sublime logical structure but as an aspectof human practice, and he showed a similarrespect for the reflexive status of psychologywhich this view entails. Both saw that the the-ory (and metatheory) of psychology must atthe very least be compatible with the fact ofthe human practice of science. Yet, as a num-

ber of critics have remarked, Skinner himselfretains, and indeed sometimes recommends,the physicalist ontology which has proved sotroublesome for psychology, and, despite thedialectical status of the concept of the operant,tends to treat the environment as though itwere an autonomous cause (Kvale & Grenness,1975; Malone, 1975).Gibson proved a good deal more alert to the

unfortunate sense in which psychology has

been "set up" by the program of classicalmechanics. For if, to use Locke's metaphor,philosophers have been keen to serve as un-derlaborers clearing away the rubbish gener-ated by such master-builders as Galileo andNewton, Gibson was not alone in realizing thatpsychology had been used as an all too con-venient dumping ground. Indeed, Edwin Burtt(1954) made this point most clearly in his im-portant text, The Metaphysical Foundationsof Modern Science:

It does seem like strange perversity inthese Newtonian scientists to further theirown conquests of external nature by load-ing on mind everything refractory to exactmathematical handling and thus render-ing the latter still more difficult to studyscientifically than it had been before....Mind was to them a convenient receptaclefor the refuse, the chips and whittlings ofscience, rather than a possible object ofscientific knowledge. (p. 320; see alsoKoyre, 1965; Mead, 1938; Whitehead,1926)

The dependence of representational theor-ists upon the ontology of classical science ismost explicit in their ultimate resort to thedistinction between primary and secondaryqualities of experience. Many aspects of per-ceptual experience, they argue, must be purelysubjective, mere mental constructions, in thatthey have no counterpart in the "real" world-the world, that is, described by physics. Gib-son's misgivings about this distinction (Gib-son, 1979, p. 31) began in some early work ofhis in the 1930s when he found that perceptualaftereffects held to be distinctive of such sec-ondary qualities as color and warmth also oc-curred for so-called primary qualities such asline and curvature (Gibson, 1933). By the1940s, he came to reject the classical, essen-tially Euclidean, notion of space as a vast,structureless container-as an abstraction ir-relevant to the psychology of perception-infavor of a conception of the visual world as aset of overlapping surfaces (e.g., Gibson, 1950;cf. Carr, 1935, p. 1). Later still, he came to in-sist that the physicalist dimension of time wasnot perceived; rather we perceive ongoingevents (Gibson, 1975; 1979, pp. 253-254). Inhis last book, in his theory of affordances, hewent on to argue that we can properly be said

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to immediately perceive the functions that ob-jects serve for our activities (1979, chapter 8).The crucial claim of Gibsonian theory is thatmany of the so-called secondary qualities areindeed real properties of our environment,and, furthermore, the structures available inambient energy are related to such environ-mental properties and events in a lawful way-they uniquely specify them. All the organismneeds to do is detect these informative struc-tures, and all that perceptual theory has todo, in turn, is explain what these structures areand how they are "picked-up":

The theory of psychophysical parallelismthat assumes that the dimensions of con-sciousness are in correspondence withthe dimensions of physics and that theequations of such correspondence can beestablished is an expression of Cartesiandualism. Perceivers are not aware of thedimensions of physics.... They are awareof the dimensions of the information inthe flowing array of stimulation that arerelevant to their lives. (Gibson, 1979, p.306)

Gibson's effort to deny the metaphysicalbasis of the distinction between primary andsecondary qualities, far from being an obsti-nate attempt to deny the very existence andsuccesses of science, was a considered efforttowards determining its proper empiricalbasis, a task anticipated in some detail, in fact,in the writings of Whitehead (e.g., Whitehead,1926, 1930, p. 48).Two points should be added about the eco-

logical ontology which Gibson developed todisplace Cartesian dualism. The first concernsthe fact that the ecological laws referred to byGibson are certainly circumscribed; as he takescare to stress, they hold within the normalecology of the organism. Such restriction, how-ever, is not a peculiarity of ecological laws. Acrucial insight of modern physics has been thatlaws specifying invariant relations need to bedefined relative to an appropriate "domain ofvalidity" (Bohm, 1965, chapter 25). Neverthe-less, many psychologists still happily pit onetheory against another, or uncritically invokePopper's canon of falsification, without any re-gard for the different sets of circumstances towhich the theories might apply.The second point concerns a more profound

implication of the ecological perspective. Gib-son denied perhaps the most central Cartesianassumption underlying cognitivism, that therelation between organism and environment isan essentially external one, the idea that theorganism can be construed as if it could existoutside of any kind of coordination with anenvironment. In contrast, both ecological andoperant psychology draw upon the importantinsight of early functionalist psychology (e.g.,Dewey, 1896, 1898/1976) that it is the verycoordination of organism and environmentthat must constitute the basic unit of analysisfor psychology. Both operant and ecologicalpsychology are committed to the view that therelation between organism and environment isinternal; neither term in this relation can bedefined independently of the relation itself.But in taking this view we should be clearabout its implication, for it follows that theenvironment can no longer be considered, asit is in the Cartesian scheme, as an autonomouscause (cf. Hocutt, 1967). I cannot say thateither Gibson or Skinner is altogether clear onthis point, but a most lucid statement can befound in the writings of the evolutionary biol-ogist Richard Lewontin (1982):

This view of environment as causallyprior to, and ontologically independentof, organisms is the surfacing in evolution-ary theory of the underlying Cartesianstructure of our world view. The world isdivided into causes and effects, the exter-nal and the internal, environments andthe organisms they 'contain'. While thisstructure is fine for clocks, since main-springs move the hands and not vice versa,it creates indissoluble contradictions whentaken as the meta-model of the livingworld. (p. 159)

(Lewontin moves towards overstatement, how-ever, when he continues that "organismswithin their individual lifetimes and in thecourse of their evolution as a species do notadapt to environments; they construct them"[p. 163; cf. Dewey, 1898/1976, pp. 279-284].)So far I have tried to set out the ways in

which Gibson's attack upon representationaltheory has served to expose and challenge thedeeper metaphysical assumptions of cognitivepsychology. Cognitivism is hardly about togive up the ghost of Cartesian dualism, and

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perhaps it will only succumb to death by athousand qualifications. But there can be nodoubt that its complacency has been disturbed,and so I must finally examine its usual retreatfrom the field of theoretical wrangling to theapparently clearer ground of empirical data.The first appeal, to laboratory experiments,

seems incontrovertible enough until we real-ize that the psychological laboratory is the verymicrocosm of the Cartesian scheme. After all,our major experimental paradigms are de-signed explicitly to prevent the organism fromtransforming the experimental situation, aswould be possible to some degree in real life(Gadlin & Rubin, 1979). The subjects are freeonly in the sense that they can react to, ratherthan change, the conditions which are imposedupon them. Furthermore, when critics, such asFodor and Pylyshyn (1981), for example, dis-miss Gibson's claims for the existence of eco-logical laws on the grounds that "it has beenrepeatedly shown in psychological laboratoriesthat percepts can be caused by samples of theambient medium which demonstrably under-determine the corresponding layout" (p. 172),they not only choose to ignore Gibson's re-quirement that our experiments should modelthe normal ecology of the organism, but theyalso disregard the carefully defined limits Gib-son has set to his theory. Gibson's is a theoryof direct perception, not a direct theory of per-ception. How people cope with the bizarre sit-uations dreamt up in most psychological labo-ratories is quite explicitly outside the scope ofecological theory.The last resort of cognitive theory is to the

fact that people do indeed follow rules andrepresent things-though, of course, they domuch else besides. Cognitive psychologists arequite wrong, however, to suppose that thesefacts about human beings can alone supporttheir entire edifice of cognitive structures, andthey are just dishonest when they pretend thatSkinner or Gibson ever wished to deny thesefacts. Gibson (1979, pp. 258-263) was quiteclear that the obtaining of "secondhand infor-mation" through words, pictures, and writingsmust be considered as truly mediated percep-tion, and Skinner has gone even further inelaborating an account of how the verbal com-munity comes to mediate much of our behav-ior (Burton, 1982; Skinner, 1945, 1957; seealso Tikhimorov, 1959). In fact, Skinner andGibson were working towards what they saw as

a proper psychology of cognition, a psychologywhich treats the relevant phenomena as neces-sarily grounded in social practices rather thanupon the essentially private and individualmental structures invoked by cognitive psy-chology. Much more needs to be said abouttheir contributions in this direction, but inthis paper I can on-ly take the opportunity toset the record straight.My primary concern in this review article

has been to introduce Gibson's critique of rep-resentational theory and to explain the waythat it has served to expose so many vestigesof Cartesian metaphysics within contemporarycognitivism. I hope I have made clear some ofthe common ground which exists between eco-logical and operant psychology. The ecologicalapproach and operant psychology share a gooddeal more than mere disenchantment with thestatus quo. Both insist that behavior presentsa primary datum for psychology which is notto be treated as a mere symptom of underlyingstructures of either the cognitive or physiologi-cal kind. They recognize that the descriptionof behavior is nevertheless difficult, and theypromote a molar and functional classificationof behavior rather than muscle-twitch psychol-ogy or classical reflexology. In rejecting theS-R scheme, however, they insist that behavioris nonetheless subject to lawful description andthat these laws refer to an irreducible organ-ism-environment relationship. Finally, theyeach have special contributions to maketowards a proper psychology of cognition-apsychology, that is, concerned with truly medi-ated modes of behavior.

In 1915, Gibson's mentor, Edwin Holt, at-tempted to survey the many groups seeking analternative to the traditional cognitivistscheme, and came to the following conclusion:

It should be obvious that a fundamentalunity of purpose animates the investiga-tors of these several groups, although theyapproach the question of cognition fromvery different directions. Will it not be asource of strength for all if they can man-age to keep a sympathetic eye on the meth-ods and discoveries of one another? (Holt,1915, p. 208)

Some seventy years after Holt's suggestion,this alliance is surely overdue. Operant psy-chologists and ecological psychologists are not,

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of course, the sole opponents of the cognitivismthat still prevails. But, as I have tried to ex-plain, they, at least, should keep "a sympa-thetic eye" on one another's progress.

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