THE OPERATIONAL ANALYSIS OF PSYCHOLOGICAL TERMSBY B. F. SKINNERUniversity of Minnesota

An answer to Question 6 will definethe position to be taken in what follows.Operationism is not regarded asa new theory or mode of definition.The literature has emphasized certaincritical or hitherto neglected instances,but no new kind of operation has beendiscovered and none should be singledout. There is no reason to restrict operationalanalysis to high-order constructs;the principle applies to all definitions(Question 9). This means, inanswer to Question 1 (a), that we mustexplicate an operational definition forevery term unless we are willing to adoptthe vague usage of the vernacular.Operationism may be defined as thepractice of talking about (1) one's observations,(2) the manipulative andcalculational procedures involved inmaking them, (3) the logical and mathematicalsteps which intervene betweenearlier and later statements, and (4)nothing else. So far, the major contributionhas come from the fourth provisionand, like it, is negative. Wehave learned how to avoid troublesomereferences by showing that they areartifacts, which may be variously tracedto history, philosophy, linguistics, andao on. No very important positive advanceshave been made in connectionwith the first three provisions becauseoperationism has no good answer toQuestion 10. It has not developed a"satisfactory formulation of the effective

verbal behavior of the scientist.The operationist, like most contemporarywriters in the field of linguistic and %semantic analysis, is on the fence betweenlogical 'correspondence' theoriesof reference and empirical formulationsof language in use. He has not improvedupon the mixture of logical andpopular terms usually encountered incasual or even supposedly technical discussionsof scientific method or thetheory of knowledge {e.g., BertrandRussell's recent An inquiry into meaningand truth). 'Definition' is a keyterm but is not rigorously defined.Bridgman's original contention that the'concept is synonymous with the correspondingset of operations' cannot betaken literally, and no similarly explicitbut satisfactory statement of the relationis available. Instead, a few roundaboutexpressions recur with rather tiresomeregularity whenever this relationis mentioned. We are told that a conceptis to be defined 'in terms of certainoperations, that propositions are tobe 'based upon' operations, that a termdenotes something only when there are'concrete criteria for its applicability,'that operationism consists in 'referringa n y c o n c e p t for i t s d e f i n i t i o n t o . . .concrete operations . . . ,' and so on.We may accept expressions of this sortas outlining a program, but they do notprovide a general scheme of definition,much less an explicit statement of therelation between concept and operation.The weakness of current .theories oflanguage may be traced to the fact that

an objective conception of human behavioris still incomplete. The doctrinethat words are used to express or conveymeanings merely substitutes 'meaning'for 'idea' (in the hope that meaningscan then somehow be got outsidethe skin) and is incompatible with modernpsychological conceptions of the organism.Attempts to derive a symbolicfunction from the principle of conditioning(or association) have been characterizedby a very superficial analysis.It is simply not true that an organismreacts to a sign 'as it would to the objectwhich the sign supplants' (Stevens,2, p. 250). Only in a very limited area(mainly in the case of autonomic responses)is it possible to regard the signas a simple substitute stimulus in thePavlovian sense. Modern logic, as aformalization of 'real' languages, retainsand extends this dualistic theory ofmeaning and can scarcely be appealedto by the psychologist who recognizeshis own responsibility in giving an accountof verbal behavior.It is not my intention to attempt amore adequate formulation here. Thefundamental revision is too sweeping tobe made hastily. I should like, however,to try to make a small but positivecontribution to this symposium by consideringa few points which arise in connectionwith the operational definitionof psychological terms. Much of thematerial which follows is adapted froma much longer work now in preparation,in which the necessary groundwork ismore carefully prepared.

The operational attitude, in spite ofits shortcomings, is a good thing in anyscience but especially in psychology becauseof the presence there of a vastvocabulary of ancient and non-scientificorigin. It is not surprising that thebroad empirical movement in the philosophyof science, which Stevens hasshown (2) to be the background of operationism,should have had a vigorousand early representation in the field ofpsychology—namely, behaviorism. Inspite of the differences which Stevenspretends to find, behaviorism has been(at least to most benaviorists) nothingmore than a thoroughgoing operationalanalysis of traditional mentalistic concepts.We may disagree with some ofthe answers (such as Watson's dispositionof images), but the questions askedby behaviorism were strictly operationalin spirit. I also cannot agree withStevens that American behaviorism was'primitive.' The early papers on theproblem of consciousness by Watson,Weiss, Tolman, Hunter, Lashley, andmany others, were not only highly sophisticatedexamples of operational inquiry,they showed a willingness to dealwith a wider range of phenomena thando current streamlined treatments, particularlythose offered by logicians (e.g.,Carnap) interested in a unified scientificvocabulary.) But behaviorism, too,stopped short of a decisive positive contribution—and for the same reason: itnever finished an acceptable formulationof the 'verbal report.' The conceptionof behavior which it developed could

not convincingly embrace the 'use ofsubjective terms.'A considerable advantage is gainedfrom dealing with terms, concepts, constructs,and so on, quite frankly in theform in which they are observed—namely, as verbal responses. There isthen no danger of including in the conceptthat aspect or part of nature whichit singles out. (Several of the presentquestions seem to mix concept and referent;at least they seem to becometrivial when, in order to make the mixtureless likely, 'term' is substituted for'concept' or 'construct.') Meanings,contents, and references are to be foundamong the determiners, not among theproperties, of response. The question'What is length?' would appear to besatisfactorily answered by listing thecircumstances under which the response'length' is emitted (or, better, by givingsome general description of such circumstances).If two quite separate sets ofcircumstances are revealed, then thereare two responses having the form'length' (Question 2), since a verbalresponse-class is not denned by phoneticform alone but by its functional relations.This is true even though the twosets are found to be intimately connected.The two responses are not controlledby the same stimuli, no matterhow clearly it is shown that the differentstimuli arise from the same 'thing.'What we want to know in the case ofmany traditional psychological terms is,first, the specific stimulating conditionsunder which they are emitted (this corresponds

to 'finding the referents') and,second (and this is a much more importantsystematic question), why eachresponse is controlled by its correspondingcondition. The latter is not necessarilya genetic question. The individualacquires language from society,but the reinforcing action of the verbalcommunity continues to play an importantrole in maintaining the specific relationsbetween responses and stimuliwhich are essential to the proper functioningof verbal behavior. How languageis acquired is, therefore, onlypart of a much broader problem.We may generalize the conditions responsiblefor the standard 'semantic' relationbetween a verbal response and aparticular stimulus without going intoreinforcement theory in detail. Thereare three important terms: a stimulus,a response, and a reinforcement suppliedby the verbal community. (All ofthese need more careful definitions thanare implied by current usage, but thefollowing argument may be made withoutdigressing for that purpose.) Thesignificant interrelations between theseterms may be expressed by saying thatthe community reinforces the responseonly when it is emitted in the presenceof the stimulus. The reinforcement ofthe response 'red,' for example, is contingentupon the presence of a red object.(The contingency need not be invariable.)A red object then becomesa discriminative stimulus, an 'occasion,'for the successful emission of the response'red' (1).

This scheme presupposes that thestimulus act upon both the speaker andthe reinforcing community; otherwisethe proper contingency cannot be maintainedby the community. But thisprovision is lacking in the case of many'subjective' terms, which appear to beresponses to private stimuli. The problemof subjective terms does not coincideexactly with that of privatestimuli, but there is a close connectionWe must know the characteristics olverbal responses to private stimuli inorder to approach the operational analysisof the subjective term.The response 'My tooth aches' ispartly under the control of a state ofaffairs to which the speaker alone is ableto react, since no one else can establishthe required connection with the toothin question. There is nothing mysteriousor metaphysical about this; thesimple fact is that each speaker possessesa small but important privateworld of stimuli. So far as we know,his reactions to these are quite like hisreactions to external events. Neverthelessthe privacy gives rise to two problems.The first difficulty is that wecannot, as in the case of public stimuli,account for the verbal response bypointing to a controlling stimulus. Ourpractice is to infer the private event, butthis is opposed to the direction of inquiryin a science of behavior in whichwe are to predict response through,among other things, an independentknowledge of the stimulus. It is oftensupposed that a solution is to be found

in improved physiological techniques.Whenever it becomes possible to saywhat conditions within the organismcontrol the response 'I am depressed,'for example, and to produce these conditionsat will, a degree of control andprediction characteristic of responses toexternal stimuli will be made possible.Meanwhile, we must be content withreasonable evidence for the belief thatresponses to public and private stimuliare equally lawful and alike in kind.But the problem of privacy cannotbe wholly solved by instrumental invasion.No matter how clearly theseinternal events may be exposed in thelaboratory, the fact remains that in thenormal verbal episode they are quiteprivate. We have not solved the secondproblem of how the community achievesthe necessary contingency of reinforcement.How is the response 'toothache'appropriately reinforced if the reinforcingagent has no contact with the tooth?There is, of course, no question ofwhether responses to private stimuli arepossible. They occur commonly enoughand must be accounted for. But whydo they occur, what is their relation tocontrolling stimuli, and what, if any,are their distinguishing characteristics?There are at least four ways in whicha verbal community which has no accessto a private stimulus may generateverbal behavior in response to it:(1) It is not strictly true that thestimuli which control the response mustbe available to the community. Anyreasonably regular accompaniment will

suffice. Consider, for example, a blindman who learns the names of a trayfulof objects from a teacher who identifiesthe objects by sight. The reinforcementsare supplied or withheld accordingto the contingency between the blindman's responses and the teacher's visualstimuli, but the responses are controlledwholly by tactual stimuli. A satisfactoryverbal system results from the factthat the visual and tactual stimuli remainclosely connected.Similarly, in the case of privatestimuli, one may teach a child to say'That hurts' in agreement with theusage of the community by making thereinforcement contingent upon publicaccompaniments of painful stimuli (asmart blow, tissue damage, and so on).The connection between public andprivate stimuli need not be invariable;a response may be conditioned withmerely periodic reinforcement and evenin spite of an occasional conflicting contingency(1). The possibility of suchbehavior is limited by the degree of associationof public and private stimuliwhich will supply a net reinforcementsufficient to establish and maintain aresponse.(2) A commoner basis for the verbalreinforcement of a response to a privatestimulus is provided by collateral responsesto the same stimulus. Althougha dentist may occasionally beable to identify the stimulus for a toothachefrom certain public accompanimentsas in (1), the response 'toothache'is generally transmitted on the

basis of responses which are elicited bythe same stimulus but which do notneed to be set up by an environmentalcontingency. The community infers theprivate stimulus, not from accompanyingpublic stimuli, but from collateral,generally unconditioned and at leastnon-verbal, responses (hand to .jaw,facial expressions, groans, and so on).The inference is not always correct, andthe accuracy of the reference is againlimited by the degree of association.(3) Some very important responsesto private stimuli are descriptive of thespeaker's own behavior. When this isovert, the community bases its instructionalreinforcement upon the conspicuousmanifestations, but the speakerpresumably acquires the response inconnection with a wealth of additionalproprioceptive stimuli. The latter mayassume practically complete control, asin describing one's own behavior in thedark. This is very close to the exampleof the blind man; the speaker and thecommunity react to different, thoughclosely associated, stimuli.Suppose, now, that a given responserecedes to the level of covert or merelyincipient behavior. How shall we explainthe vocabulary which deals withthis private world? (The instrumentaldetection of covert behavior is againnot an answer, for we are interested inhow responses to private stimuli arenormally, and non-instrumentally, setup.) There are two important possibilities.The surviving covert responsemay be regarded as an accompaniment

of the overt (perhaps part of it), inwhich case the response to the privatestimulus is imparted on the basis of thepublic stimulus supplied by the overtresponse, as in (1). On the other hand,the covert response may be similar to,though probably less intense than, theovert and hence supply the same stimulus,albeit in a weakened form. Wehave, then, a third possibility: a responsemay be emitted in the presenceof a private stimulus, which has no publicaccompaniments, provided it is occasionallyreinforced in the presence ofthe same stimulus occurring with publicmanifestations.Terms falling within this class areapparently descriptive only of behavior,rather than of other internal states orevents, since the possibility that thesame stimulus may be both public andprivate (or, better, may have or lackpublic accompaniments) seems to arisefrom the unique fact that behavior maybe both covert and overt.(4) The principle of transfer or stimulusinduction supplies a fourth explanationof how a response to private stimulimay be maintained by public reinforcement.A response which is acquiredand maintained in connection with publicstimuli may be emitted, through induction,in response to private events.The transfer is not due to identicalstimuli, as in (3), but to coincidingproperties. Thus, we describe internalstates as 'agitated,' 'depressed,' 'ebullient,'and so on, in a long list. Responsesin this class are all metaphors

(including special figures like metonomy).The term 'metaphor' is notused pejoratively but merely to indicatethat the differential reinforcement cannotbe accorded actual responses to theprivate case. As the etymology suggests,the response is 'carried over' fromthe public instance.In summary, a verbal response to aprivate stimulus may be maintained instrength through appropriate reinforcementbased upon public accompanimentsor consequences, as in (1) and(2), or through appropriate reinforcementaccorded the response when it ismade to public stimuli, the private caseoccurring by induction when the stimuliare only partly similar. If these are theonly possibilities (and the list is hereoffered as exhaustive), then we mayunderstand why terms referring to privateevents have never formed a stableand acceptable vocabulary of reasonablyuniform usage. This historicalfact is puzzling to adherents of the'correspondence school' of meaning.Why is it not possible to assign namesto the diverse elements of private experienceand then to proceed with consistentand effective discourse? Theanswer lies in the process by which'terms are assigned to private events,'a process which we have just analyzedin a rough way in terms of the reinforcementof verbal responses.None of the conditions that we haveexamined permits the sharpening ofreference which is achieved, in the caseof public stimuli, by a precise contingency

of reinforcement. In (1) and(2) the association of public and privateevents may be faulty; the stimuliembraced by (3) are of limited scope;and the metaphorical nature of those in(4) implies a lack of precision. It is,therefore, impossible to establish arigorous scientific vocabulary for publicuse, nor can the speaker clearly 'knowhimself' in the sense in which knowingis identified with behaving discriminatively. In the absence of the 'crisis'provided by differentia] reinforcement(much of which is necessarily verbal),private stimuli cannot be analysed.(This has little or nothing to do withthe availability or capacity of receptors.)The contingencies we have reviewedalso fail to provide an adequate checkagainst fictional distortion of the relationof reference (e.g., as in rationalizing). Statements about private eventsmay be under control of the drives associatedwith their consequences ratherthan antecedent stimuli. The communityis skeptical of statements of thissort, and any attempt by the speakerto talk to himself about his privateworld (as in psychological system making)is fraught with self-deception.Much of the ambiguity of psychologicalterms arises from the possibilityof alternative or multiple modes of reinforcement.Consider, for example,the response 'I am hungry.' The communitymay reinforce this on the basisof the history of ingestion, as in (1),or collateral behavior associated withhunger, as in (2), or as a description of

behavior with respect to food, or stimulipreviously correlated with food, as in(3). In addition the speaker has (insome instances) the powerful stimulationof hunger pangs, which is private,since the community has no suitableconnection with the speaker's stomach.'I am hungry' may therefore be variouslytranslated as 'I have not eatenfor a long time' (1), or 'That foodmakes my mouth water' (2), or 'I amravenous' (3) (compare the expression'I was hungrier than I thought' whichdescribes the ingestion of an unexpectedlylarge amount of food), or 'Ihave hunger pangs.' While all of thesemay be regarded as synonymous with'I am hungry,' they are not synonymouswith each other. It is easy forconflicting psychological systematise tocite supporting instances or to tramspeakers to emit the response 'I amhungry' in conformity with a system.With the balloon technique one mightcondition the verbal response exclusivelyto stimulation from stomach contractions.This* would be an example ofeither (1) or (2) above. Or a speakermight be trained to make nice observationsof the strength of his ingestivebehavior, which might recede to thecovert level as in (3). The response'I am hungry' would then describe atendency to eat, with little or no referenceto stomach contractions. Everydayusage reflects a mixed reinforcement.A similar analysis could be madeof all terms descriptive of motivation,emotion, and action in general, including

(of special interest here) the acts ofseeing, hearing, and so on.When public manifestations survive,the extent to which the private stimulustakes over is never certain. In the caseof a toothache, the private event is nodoubt dominant, but this is due to itsrelative intensity, not to any conditionof differential reinforcement. In a descriptionof one's own behavior, theprivate component may be much lessimportant. A very strict external contingencymay emphasize the publiccomponent, especially if the associationwith private events is faulty. In arigorous scientific vocabulary private effectsare practically eliminated. Theconverse does not hold. There is apparentlyno way of basing a responseentirely upon the private part of a complexof stimuli. A differential reinforcementcannot be made contingent uponthe property of privacy. This fact is ofextraordinary importance in evaluatingtraditional psychological terms.The response 'red' is imparted andmaintained (either casually or professionally)by reinforcements which arecontingent upon a certain property ofstimuli. Both speaker and community(or psychologist) have access to thestimulus, and the contingency may bemade quite precise. There is nothingabout the resulting response that shouldpuzzle anyone. The greater part ofpsychophysics rests upon this solid footing.The older psychological view, however,was that the speaker was reporting,not a property of the stimulus, but

a certain kind of private event, thesensation of red. This was regarded asa later stage in a series beginning withthe red stimulus. The experimenterwas supposed to manipulate the privateevent by manipulating the stimulus.This seems like a gratuitous distinction,but in the case of some subjects a similarlater stage could apparently be generatedin other ways (by arousing an'image'), and hence the autonomy of aprivate event capable of evoking the response'red' in the absence of a controllablered stimulus seemed to beproved. An adequate proof, of course,requires the elimination of other possibilities(e.g., that the response is generatedby the procedures which are intendedto generate the image).Verbal behavior which is 'descriptiveof images' must be accounted for in anyadequate science of behavior. The difficultiesare the same for both behavioristand subjectivist. If the privateevents are free, a scientific descriptionis impossible in either case. If lawscan be discovered, then a lawful descriptionof the verbal behavior can beachieved, with or without references toimages. So much for 'finding the referents;'the remaining problem of howsuch responses are maintained in relationto their referents is also soluble.The description of an image appears tobe an example of a response to a privatestimulus of class (1) above. Thatis to say, relevant terms are establishedwhen the private event accompanies acontrollable external stimulus, but responses

occur at other times, perhaps inrelation to the same private event. Thedeficiencies of such a vocabulary havebeen pointed out.We can account for the response 'red'(at least as well as for the 'experience'of red) by appeal to past conditions ofreinforcement. But what about expandedexpressions like 7 see red' or7 am conscious of red'? Here 'red'may be a response to either a public ora private stimulus without prejudice tothe rest of the expression, but 'see' and'conscious' seem to refer to events whichare by nature or by definition private.This violates the principle that a reinforcementcannot be made contingentupon the privacy of a stimulus. A referencecannot be narrowed down to aspecifically private event by any knownmethod of differential reinforcement.The original behavioristic hypothesiswas, of course, that terms of this sortwere descriptions of one's own (generallycovert) behavior. The hypothesisexplains the establishment and maintenanceof the terms by supplying naturalpublic counterparts in similar overt behavior.The terms are in general ofclass (3). One consequence of the hypothesisis that each term may be givena behavioral definition. We must, however,modify the argument slightly. Tosay 'I see red' is to react, not to red(this is a trivial meaning of 'see'), butto one's reaction to red. 'See' is a termacquired with respect to one's own behaviorin the case of overt responsesavailable to the community- But according

to the present analysis it maybe evoked at other times by any privateaccompaniment of overt seeing. Hereis a point at which a non-behavioral privateseeing may be slipped in. Althoughthe commonest private accompanimentwould appear to be the stimulationwhich survives in a similar covertact, as in (3), it might be some sort ofstate or condition which gains controlof the response as in (1) or (2).The superiority of the behavioral hypothesisis not merely methodological.That aspect of seeing which can be definedbehaviorally is basic to the term asestablished by the verbal communityand hence most effective in public discourse.A comparison of cases (1) and(3) will also show that terms which recedeto the private level as overt behaviorbecomes covert have an optimalaccuracy of reference, as responses toprivate stimuli go.The additional hypothesis followsquite naturally that being conscious, asa form of reacting to one's own behavior,is a social product. Verbal behaviormay be distinguished, and convenientlydenned, by the fact that thecontingencies of reinforcement are providedby other organisms rather than bya mechanical action upon the environment.The hypothesis is equivalent tosaying that it is only because the behaviorof the individual is important tosociety that society in turn makes it importantto the individual. The individualbecomes aware of what he isdoing only after society has reinforced

verbal responses with respect to his behavioras the source of discriminativestimuli. The behavior to be described(the behavior of which one is to beaware) may later recede to the covertlevel, and (to add a crowning difficulty)so may the verbal response. It is anironic twist, considering the history ofthe behavioristic revolution, that as wedevelop a more effective vocabulary forthe analysis of behavior we also enlargethe possibilities of awareness, sodenned. The psychology of the otherone is, after all, a direct approach to'knowing thyself.'The main purpose of this discussionhas been to answer Question 10 byexample. To be consistent the psychologistmust deal with his own verbalpractices by developing an empiricalscience of verbal behavior. He cannot,unfortunately, join the logician in defininga definition, for example, as a'rule for the use of a term' (Feigl); hemust turn instead to the contingenciesof reinforcement which account for thefunctional relation between a term, as .a verbal response, and a given stimulus.This is the 'operational basis' for hisuse of terms; and it is not logic butscience.The philosopher will call this circular.He will argue that we must adopt therules of logic in order to make and interpretthe experiments required in anempirical science of verbal behavior.But talking about talking is no morecircular than thinking about thinking orknowing about knowing. Whether or

not we are lifting ourselves by our ownbootstraps, the simple fact is that wecan make progress in a scientific analysisof verbal behavior. Eventually weshall be able to include, and perhaps tounderstand, our own verbal behavior asscientists. If it turns out that our finalview of verbal behavior invalidates ourscientific structure from the point ofview of logic and truth-value, then somuch the worse for logic, which will alsohave been embraced by our analysis.

REFERENCES1. SKINNER, B. F. The behavior of organisms:an experimental analysis. New York:D. Appleton-Century Co., 1938.2. STEVENS, S. S. Psychology and the scienceof science. Psyckol. Bull., 1939, 36,221-263.