JOURNAL OF THE EXPERIMENTAL ANALYSIS OF BEHAVIOR

BEHA VIOR REGULA TION AND LEARNED PERFORMANCE:SOME MISAPPREHENSIONS AND DISAGREEMENTS

WILLIAM TIMBERLAKE

INDIANA UNIVERSITY

The behavior-regulation approach to learned performance has been the subject of misap-prehension and disagreement concerning: (1) the nature and importance of behaviorregulation, (2) the definition and role of behavioral set-points, (3) the relation of optimalschedule performance to behavioral set-points, and (4) the question of whether deviationsfrom total responding or from response patterns are the primary determinant of molarresponding under schedule constraint. After clarifying the nature and role of behaviorregulation and set-points, this paper shows that the data used to question optimal scheduleperformance (Allison, 1981a) actually strongly support the general behavior-regulation ap-proach. These data also indicate a role for response-pattern set-points in determiningschedule behavior, but contradict the hypothesis that deviations from response-patterncharacteristics are the primary determinant of molar schedule effects.

Key words: behavior regulation, behavioral set-points, optimization, molar equilibrium,response deprivation, response-pattern set-points, fixed-ratio schedules, concurrentschedules

This paper began as a modest attempt toresolve a few disagreements concerning thenature and role of set-points in the behavior-regulation approach to learned perfor-mance. Reviews of the original paper re-vealed a considerable lack of appreciation ofthe disagreements and, more importantly,wide-spread and diverse misgivings aboutthe concepts of set-point and behaviorregulation. Because behavior regulation insome form underlies a large number of re-cent models of learned performance (e.g.,Allison, 1976; Hanson & Timberlake, 1983;Lea, 1983; Rachlin & Burkhard, 1978; Stad-don, 1979; Timberlake & Allison, 1974),and because this approach deals well with aconsiderable range of data (e.g., Hanson &Timberlake, 1983; Staddon, 1979; Timber-lake, 1977, 1980) that are often omitted inmore traditional theories, it seemed impor-tant to address the misapprehensions anddisagreements that might impede its con-

Preparation of this manuscript was supported bygrants from the National Science Foundation. I thankSteven Hanson and Gary Lucas for important discus-sions, and Gary Lucas, Don Gawley, and JamesAllison for comments. Requests for reprints may besent to the author at the Department of Psychology,Indiana University, Bloomington, Indiana 47405.

tinued development. Thus, the presentpaper was written to clarify the basic con-cepts of behavior regulation and to suggestresolutions to several current disagreementsin this area.The behavior-regulation approach real-

izes the concepts of response deprivation(Timberlake & Allison, 1974) and molarequilibrium theory (Timberlake, 1980) inthe language of control theory (McFarland,1971) and behavioral instigation (Atkinson& Birch, 1970). The approach clarifies andmakes more precise the basic disequilibriumanalysis of learned performance stemmingfrom early work by Premack (1965, 1971).The fundamental assumption is that asymp-totic learned performance is produced by asubject's regulatory response to a dis-equilibrium condition (challenge) imposedby the contingency schedule (Allison, 1976,1981b; Allison & Boulter, 1982; Allison,Miller, & Wozny, 1979; Ettinger & Stad-don, 1983; Hanson & Timberlake, 1983;Hursh, 1978; Lea, 1983; Mazur, 1975;Rachlin & Burkhard, 1978; Staddon, 1979;Timberlake, 1980; Timberlake & Allison,1974; Timberlake & Wozny, 1979). Most in-vestigators presume that responding underthe constraint of a schedule is regulated with

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1984. 41, 355-375 NUMBER 3 (MAY)

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respect to a pre-schedule equilibrium condi-tion, which can be measured in a free base-line. This baseline indexes the instigation(the combined response-inducing qualities ofthe environment and the internal state of thesubject) for each important activity during a

period in which all activities are uncon-

strained and simultaneously available. Inthe context of control theory, these baselinelevels of responding can be viewed as set-

points (Hanson & Timberlake, 1983; Stad-don, 1980; Timberlake, 1980), and withinan economic framework as an ideal or "bliss"point (Rachlin, Battalio, Kagel, & Green,1981).A typical contingency schedule imposes a

challenge by constraining relative access tothe baseline level of one of the responses,

which is usually referred to as the contingentresponse or "reinforcer." The resultant dis-equilibrium produces a change in the instru-mental response that counteracts the direc-tion of the challenge and, within limits, isdirectly related to the severity of the con-

straint. The severity of the constraint can begauged by the reduction in one response

(e.g., drinking) that would result if the otherresponse (e.g., wheel running) were to re-

main at its baseline level. Thus, a schedulethat requires relatively too much wheel run-

ning for access to relatively too little watershould produce an increase in wheel runningleading to drinking (Timberlake & Allison,1974). Further, the increase in wheel run-

ning should be directly related to the severityof the initial decrease in drinking imposed bythe schedule.

Figure 1 illustrates some importantelements of the behavior-regulation ap-

proach. The free-baseline set-points of in-strumental and contingent responding are

represented as a single point in a behaviorspace in which they axis shows instrumentalresponding (e.g., wheel running) and the x

axis shows contingent responding (e.g.,drinking). A contingency schedule producesa disequilibrium condition by preventing thesubject from simultaneously regaining itsset-points of wheel running and drinking.For example, under a reciprocal ratio

WILLIAM TIMBERLAKE

w

I>

CONTINGENT RESPONSE

Fig. 1. A two-dimensional behavior space showing

amount of instrumental responding (e.g., wheel run-

ning) on they axis and amount of contingent respond-

ing (e.g., drinking) on the x axis. The point (Or,O) )

designates the baseline set-points of total instrumental

and contingent responding; the diagonal line indicates

the locus of responding specified by a ratio schedule.

Dc represents the deficit in contingent responding if the

subject were to perform the instrumental response at

its baseline level under the terms of the ratio schedule;

E1 represents the excess in instrumental responding if

the subject were to perform the contingent response at

its baseline level under the terms of the ratio schedule.

schedule (represented in Figure 1 by a

straight line beginning at the origin), if the

subject were to perform wheel running at its

baseline level, it would fall considerably

short of its baseline amount of drinking. On

the other hand, if the subject were to drink at

its baseline level, it would be forced to ex-

ceed its baseline amount of wheel running.

The typical resolution of such a disequilib-

rium condition is a compromise in which the

subject increases wheel running above its

baseline, though not enough to return drink-

ing to its baseline (Timberlake, 1980).

The important contributions of the behav-

ior-regulation approach include a priori

designation of the conditions of reinforce-

ment, punishment, or no effect, and the

prediction of qualitative and quantitative ef-

fects of manipulating schedule values.

However, despite its potential importance

and power, the behavior-regulation ap-

proach has had a mixed reception. Its con-

tributions frequently have been obscured by

misapprehensions on the part of advocates

and detractors alike. The intent of this paper

is to clarify four important areas of misun-

derstanding and disagreement: (1) the nature

BEHAVIOR REGULATION AND LEARNED PERFORMANCE

and importance of behavior regulation, (2)the role and measurement of behavioral set-points, (3) the role of behavioral set-points intheories of optimal regulation, and (4) therelative importance of response-pattern set-points in determining schedule performance.The initial sections clarify the concepts ofbehavior regulation and behavioral set-points. The final two sections address some

specific disagreements within the behavior-regulation approach.

THE NATURE AND IMPORTANCEOF BEHAVIOR REGULATION

The Nature ofBehavior RegulationA frequent question about the nature of

behavior regulation concerns its relationshipto physiological drive states and homeostasis(Cannon, 1932). Behavior regulation is nottied directly to physiological mechanisms.Instead, it is related to the instigating(response-producing) qualities in the animaland the environment. In traditional lan-guage instigation refers to the combinedresponse-producing effects of stimulus in-centives in the environment and the physio-logical state of the organism. Instigation isnot contained in the animal or in the en-

vironment; it is a product of their interactionand can be thought of as a force underlyingbehavior (Atkinson & Birch, 1970). For ex-

ample, in the case of drinking, the in-stigating qualities of the situation include theintra-cellular and extra-cellular fluiddeficits, other internal cues that controldrinking, and external cues such as the odor,physical location, taste, and temperature ofthe water. Though physiological mechan-isms are involved, it is not necessary thatthey be understood or that their action bestrictly homeostatic (Bolles, 1980). Thesingle basic requirement is that the total in-stigation in the situation be reliable duringthe interval of interest.The fundamental assumption of behavior

regulation is that, in the absence of changesin instigation, a forced deviation in the ex-

pression of behavior results in a disparitybetween expression and instigation that

motivates a return to previous levels ofresponding. Under a schedule that links tworesponses, the tendency to return to theprevious level of one response must be ex-pressed by changes in the other response.For example, if a ratio schedule allows lessthan the baseline amount of drinking for thebaseline amount of wheel running, then partof the instigation for drinking is expressed byincreasing wheel running above its baselinelevel, thereby providing further access todrinking.

Thus, what is regulated in the present ap-proach is any disparity between the expres-sion of a type of behavior and its instigation.Under a schedule linking two responses, themeans of regulation most frequently involveschanges in expression of the linked response(Hanson & Timberlake, 1983). Allison(1976) has referred to regulation as the "con-serving" of an unspecified dimension under-lying responding (instigation). An alter-native phrasing is that the animal substitutesor exchanges increases in one response forthe amount of constraint on the other re-sponse (Allison & Boulter, 1982; Rachlin etal., 1981; Timberlake, 1971, 1979). Stillanother phrasing is that the animal balances(or minimizes) the deviations of the re-sponses from their respective baseline set-points (Hanson & Timberlake, 1983; Stad-don, 1979; Timberlake, 1971). Basically allthese views are related characterizations ofthe way disparities between expression andbaseline instigation are regulated by expres-sion under schedule constraint.

It is worth emphasizing that schedule per-formance is related to all important devia-tions in the situation, not just the relativedeficit in the contingent response. Figure 1makes clear that as the subject increases in-strumental responding (e.g., wheel running)and thereby gains access to the contingentresponse (e.g., drinking), it simultaneouslydecreases the deviation from the set-point ofdrinking and increases the deviation fromthe set-point of wheel running. Asymptoticperformance will be determined by relatingthe size and value of the deficit in drinking tothe size and value of the excess in wheel run-

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WILLIAM TIMBERLAKE

ning. This balancing of weighted deviationscan be used to predict nonmonotone rela-tions between schedule parameters and totalinstrumental responding (see Staddon,1979, or Hanson & Timberlake, 1983, formore extensive development of this point).

In this light, the original term "response

deprivation" (Timberlake & Allison, 1974),though calling attention to the behaviorallevel of regulation, had two unfortunate con-

notations. First, it focused attention on theresponse that was relatively in a condition ofdeficit with respect to its set-point withoutdirecting similar attention to the response

that was relatively in a condition of excess

(Timberlake, 1980). Both deviations are ob-viously important in producing learned per-

formance. Second, the term could be misin-terpreted as referring to an actual reductionin responding (as in Premack, 1965), ratherthan to an a priori condition of relative con-

straint (disequilibrium) imposed by theschedule on expression of the instigationunderlying the contingent response. To treatthe actual reduction of responding as a

causal variable changes the behavior-regula-tion approach from an a priori to a post hoctheory with attendant loss of power (Timber-lake, 1980).

In sum, the behavior-regulation approachdoes not require homeostatic physiologicalmechanisms, but merely reliable instigationunder schedule constraint and the tendencyto reduce disparitites between levels of in-stigation and their expression in behavior.Instigation is the product of a particularanimal in a particular environment at a par-

ticular time, and its expression in learnedperformance is the product of a schedule thatlinks the disparity between the levels of in-stigation and expression for one responsewith the expression of the other response

(Hanson & Timberlake, 1983). At presentthe level of instigation in a situation must bereliably known before behavior-regulationtheories can be applied. This is not a largeproblem in laboratory studies because it ispossible to run long baseline assessmentsand ensure consistency of instigation over

sessions, but it may be a drawback in ap-

plied settings, especially those with variableinstigation. Some common-sense proceduresand guesses about instigation would behelpful here. Perhaps in the long run atheory of instigation combined with a singlebehavioral assessment or knowledge of phys-iological processes will allow predictionsacross circumstances with variable instiga-tion.

The Importance ofBehavior RegulationTraditionally, learned performance has

been attributed to the combined effects oflocal associative (reinforcement) variablesand more general motivation or drive vari-ables. With few exceptions, operant researchhas focused on the local "reinforcement" ef-fects produced by different schedules, whileholding overall motivation constant by usinghighly deprived organisms and small, infre-quent rewards. Within this framework thebehavior-regulation approach is oftenviewed as a theory of general drive ormotivation that can be used to set the overallpotency of a given reinforcing agent, butwhich is unrelated to the particulars ofschedule effects. Reinforcement theoriesmust be used to determine the reinforcementeffects of schedules on the instrumentalresponse.

In fact, behavior regulation is not a theoryof the overall potency of "reinforcers," but isa theory of how the schedule interacts withinstigation levels to produce learned perfor-mance. What is confusing to many is thatthe language and the conceptual develop-ment of behavior regulation are in terms ofmotivation or function, not of the shaping ofbehavior or of discriminative control. Fur-ther, the presumed level of regulation ismost often at the session level, not at thelocal level of individual "reinforcers" con-tingent on individual responses (however,see Allison & Timberlake, 1975; Timberlake& Hopp, 1979; see also the matching law,which despite its avowed allegiance to rein-forcement shares the same strategy of focus-ing on the "balancing' of different responsesover larger intervals of time [Herrnstein,1970; Herrnstein & Vaughan, 1980]).

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BEHA VIOR REGULATION AND LEARNED PERFORMANCE

In essence, the behavior-regulation ap-proach accounts for the effects of schedulevariables on responding on the basis of theirregulatory effects viewed across the entiresession, not on the basis of their presumedlocal response-strengthening effects. How-ever, I disagree with Rachlin and Burkhard's(1978) argument that the ability to predictand fit responding without direct appeal toreinforcement mechanisms implies that learn-ing is unimportant. All this means is thatgiven circumstances that allow expression ofconstrained instigation through an instru-mental response, the regulation of unex-pressed instigation accounts for much of thechange in behavior. I expect future work todeal more carefully with the contribution ofassociative effects to schedule responding(Timberlake, 1979) and with regulation oc-curring at both shorter and longer intervalsthan the session.An example may help clarify the distinc-

tion between the typical interpretation ofbehavior regulation as a theory of themotivational determinants of the overallpotency or value of a "reinforcer," and themore appropriate view of behavior regula-tion as a theory of learned performance. Atheory of value creates a "reinforcer" bydepriving the animal of access outside theexperimental session (and, without acknowl-edging it, imposing a schedule within the ex-perimental session that constrains the con-tingent response relative to its baseline).Thus we might take water away from an ani-mal in its home cage to ensure its potency asa reinforcer for wheel running, or take thewheel away from the animal to ensure itspotency as a reinforcer for drinking (cf.Premack, 1962). In contrast, the behavior-regulation approach holds that depriving theanimal of access to a commodity outside theexperimental situation is neither a necessarynor a sufficient conditon to create a "rein-forcer."The circumstances of reinforcement are

created by imposing a relative deprivation ofthe expression of a response within the ex-perimental session. Thus, to create drinkingas a "reinforcer" for running, the schedule

must produce an initial constraint on drink-ing during the session relative to its baselinelevels. In theory it is irrelevant whetherwater has been available to the subject out-side the experimental session. Conversely, tocreate running as a "reinforcer" for drinking,the schedule need only be altered to producean initial constraint on wheel running (Tim-berlake & Wozny, 1979).To be sure, there are pragmatic limits on

all this. If the animal will not drink at allduring the experimental session, a disequi-librium cannot be created. Thus, deprivingthe animal of water outside the experimentalsession will facilitate procedures deprivingthe animal within the experimental sessionby increasing the amount of drinking avail-able to manipulate. But this does not alterthe basic theoretical issue. At the most fun-damental level, "reinforcers" (actually cir-cumstances in which reinforcement occurs)are created by combinations of schedulesand instigation levels, not by noncontingentdeprivation manipulations imposed outsidethe experimental situation. In practicalterms, the world does not divide easily intocategories of reinforcers and nonreinforcers(Premack, 1965, 1971), nor into neat cate-gories of drive operations and reinforcementoperations. Instead, learned performance isthe outcome of the regulation of the disparitybetween instigation and expression, wherethis disparity depends conjointly on driveand reinforcement operations and on thestability of instigation.To summarize: Whatever kind of theory it

may appear to be, behavior regulation ac-counts for learned performance, includingany associative effects that occur as a prod-uct of the schedule. It is not a theory ofgeneral reinforcer potency because whetheran organism is deprived of a commodity out-side the experimental situation is nottheoretically important or interesting. Tocreate the circumstances for reinforcementacross a session, one must create a within-session disequilibrium in the relative expres-sion of the responses linked by a schedule.Behavior regulation is clearly not welldeveloped at the level of conceptualizing the

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local effects of access to constrainedresponses ("reinforcers") and integratingthese effects into a complete account oflearned performance, but it is nonetheless atheory of learned performance at the level oftotal responding in a session. And there areconsiderable advantages to this approach,including predicting the circumstances forreinforcement and both direct and inverserelations between reward density and in-strumental performance (Allison, 1981b;Hanson & Timberlake, 1983; Staddon,1979; Timberlake, 1977, 1980), predictionsnot made by most traditional models.

BEHAVIORAL SET-POINTS

The concept of behavioral set-points hasproven to be the most controversial aspect ofthe behavior-regulation approach, perhapsbecause set-points are seen as implying aninvariant internal state. It should be clear bynow that a behavioral set-point is basicallyan index of the instigation for an activitypresent in a particular situation. For thatsituation only, it can be viewed as a "blisspoint" representing the preferred level of ex-pression of an activity when unconstrainedby a schedule. When the expression of a set-point is constrained by a schedule, the dis-parity between expression and instigationbecomes a driving force for learned perfor-mance, given mechanisms that allow thecoupling of the instigation for one responseto the expression of another (Hanson & Tim-berlake, 1983). For example, when drinkingis constrained as in Figure 1, its deviationfrom set-point level drives instrumentalwheel running. A most critical question forthe behavior-regulation approach is how abehavioral set-point is identified andmeasured. There are two current answers tothis question: (1) assessment of respondingin a free baseline, and (2) calculation fromschedule performance on the basis of amodel. I will consider them in turn.

The Assessment ofBehavioral Set-PointsAny measurement procedure for defining

behavioral set-points must satisfy several

criteria. Inasmuch as a behavioral set-pointis simply the expression of instigation under-lying a particular activity, the more accu-rately behavior reflects the underlying in-stigation, the more accurately it should serveas a set-point. Thus, a behavioral set-pointshould be measured under unconstrainedconditions so that its current level of instiga-tion is clearly expressed. Further, because aset-point will change with changes in instiga-tion, the conditions during both assessmentand constraint must be as constant as possi-ble. Session length, physical environment,time of day, available responses, and thesubject's physiological and experiential statemust remain fixed except for the preciseschedule manipulations of interest. Ifresponse determinants other than the im-position of the schedule are allowed to varybetween baseline and contingency, it isnecessary to reassess the baselines. This isthe price paid for the advantage of using thebaseline to estimate the set-points.The free-baseline procedure (previously

termed the paired or multiple baseline) ap-pears to fulfill these criteria in a reasonablefashion. The baseline is measured with allrelevant responses freely available under thereliable instigating conditions that will bepresent when the schedule is imposed. Con-siderable data show that free-baselinemeasures are reliable and recoverable(Peden, Rohe, & Keller, 1983; Timberlake,1980). However, some data suggest thatthese measures may change over time and asthe result of a contingency (Timberlake,1980; see also Tierney, Smith, & Gannon,1983). It could be argued that the freebaseline itself contains a certain degree ofconstraint and thus tends to underestimatethe amount of instigation present. In fact,there are data compatible with this assertion.Timberlake (1980) reviewed results thatshowed increases in both instrumental andcontingent responding under relatively easyschedules, a result that would be expected ifthe free baseline tended to underestimate theinstigation present. Nonetheless, with ap-propriate precautions concerning the separa-tion of response alternatives (e.g., Allison et

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al., 1979) the free baseline appears to be areliable and reasonable empirical assessmentof basic instigation.

Several investigators have suggested otherbaselines. However, typically the rationale isnot as compelling. Some have argued that asingle baseline involving only one of theresponses is a more accurate assessment ofthe instigation for a particular response.However, to the extent that two responsesmay share instigation, the single baselineoverestimates the total instigation present bymeasuring the common instigation twice,once as it is expressed in each type of behav-ior. Rachlin et al. (1981) suggested a base-line that measures instrumental respondingwith the contingent response constrained butin the absence of an instrumental require-ment. This baseline does not allow indepen-dent assessment of the instigation for con-tingent responding. It is most appropriatefor assessing contingent versus noncontin-gent effects of the schedule (Timberlake,1979).A more common approach is to measure

baselines under a schedule imposing a lowdegree of constraint - for example, FR 1.Such baselines may accurately reflect the in-stigation for an inelastic contingent responsesuch as feeding, given a flexible instrumen-tal response such as bar pressing. In suchcases the experimenter infers the indepen-dent instigation of bar pressing to be nearzero, and presumes that bar pressing isessentially transparent to the expression ofinstigation for feeding. However, with otherresponse combinations, failure to use thefree baseline may make a considerable dif-ference in assessing the amount of instiga-tion present. Instrumental responses such aswheel running have significant levels of in-dependent instigation and are not transpar-ent in expressing the instigation for con-tingent responses. Thus, schedule assess-ment of instigation is of more limited use.There is one notable limitation on free-

baseline measures as predictors of respond-ing under schedule constraint. Although thebaseline provides evidence of the fundamen-tal levels of response instigation, it does not

indicate how this instigation will be trans-lated into expression under a schedule(although Hanson & Timberlake, 1983, pro-posed a relationship between expressioncharacteristics in baseline and contingency).For example, some responses (or more prop-erly, some response combinations, such asbar pressing and eating) show great resil-ience to challenge; other response combina-tions (such as wheel running and saccharinlicking in satiated rats) show only momen-tary or asymmetric defense of baselinelevels. Such expression characteristics havebeen previously noted under concepts suchas elasticity (Allison et al., 1979; Burkhard,1982; Hursh, 1980; Lea, 1978; Rachlin,Green, Kagel, & Battalio, 1976; Rachlin etal., 1981), consummatory force (Atkinson &Birch, 1970), resilience (Houston & McFar-land, 1980), and resistance to change(Nevin, Mandell, & Atak, 1983). Thesemodifying characteristics are best deter-mined under conditions of constraint, butsystematic rules for the assessment of somehave not yet been agreed on. What is neededat this point is more research into the natureof expression characteristics and models thatexplicitly take them into account.The second general technique of assessing

set-points is to use a model sufficiently com-plex to infer baselines from fits to scheduleperformance. This technique has been usedor suggested by Allison (1981b), Allison andBoulter (1982), Hanson and Timberlake(1983), Rachlin and Burkhard (1978), Rach-lin et al. (1981), and Staddon (1979). Thetechnique requires a model that referencesresponding to some basic preferred responsedistribution, and allows the conceptualseparation of such a "bliss point" from ex-pression characteristics and schedule effects.There are several drawbacks to this ap-proach. First, in some cases the reality statusof these set-points is the subject of confusion(Motherall, 1981; Rachlin et al., 1981; how-ever, see Houston & McFarland, 1980). It isnot clear whether they refer literally to inter-nal states of the organism, potentially to ex-ternal expressions in behavior, or simply toimaginary entities.

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A second problem is that when models in-clude the set-points as free parameters, thenumber of parameters fit from the data in-creases, usually to four or five. This meansthat models cannot reasonably be testedwithout a large number of data points, 25 to40 depending on different rules of thumb.Very few, if any, data sets are based on thisnumber of manipulations. A reasonable fu-ture strategy would be to compare the resultsof free-baseline measures of instrumentaland contingent responding with measurescomputed from different models. Dependingon the outcome, this might allow the relativeassessment of the strengths of differentmodels as well as an indication of the generalaccuracy of the free-baseline measure (Tim-berlake, 1981).

Common Reservations about Behavioral Set-Points

Although the rationale for behavioral set-points and their assessment is reasonablyclear, several reviewers have remained reluc-tant to accept their use. Their reservationstake several forms: (1) It appears that theconcept of a behavioral set-point requires asubject to keep track of its amount and pat-tern of behavior with unreasonable precisionand timing. (2) Any phenomenon that canbe explained by set-points and behavior reg-ulation can be explained by reinforcementand punishment. (3) How does one knowthere really are set-points?On the problem of unreasonable measure-

ment sensitivity, it is apparent that behaviorshows extreme reliability in duration andpattern in many situations. Animals keptunder constant conditions perform reliablyday after day in behavior patterns rangingfrom exploration and grooming (Timber-lake, 1969) through feeding (Le Magnen,1981; Richter, 1927) to direction and timingof running in a wheel (Kavanau, 1969; Kav-anau & Rischer, 1968). The typical reliabil-ity of baselines obtained by investigatorswithin the present approach, and the reliablemathematical relations between baseline andcontingency performance (e.g., Allison,1976; Hanson & Timberlake, 1983; Stad-

don, 1979) show that reliable timing ofresponding occurs.

It is interesting that arbitrary tests of theability to time intervals reveal systematiclimitations (e.g., Gibbon, 1977), but thisresult is not necessarily related to theorganization and timing of naturally occur-ring activities. A mechanism that distributesmeals or bursts across a session may not beavailable under experimental demands fortiming arbitrary intervals in arbitrary cir-cumstances. Because it appears unquestion-able that precise and accurate timing ofbehavior occurs, our concern should be withits description and cause, not with a priorirejection of its existence. An importantdirection for research might well be the in-vestigation of the control of the timing andduration of natural behavior under free andconstrained conditons coupled with a morecareful look at its precision of expression.The second contention, that results pre-

dicted by behavior regulation and set-pointscan be explained by reinforcement and pun-ishment, is basically an argument for thefamiliar rather than the unfamiliar, comfor-ting ourselves with knowledge we do notreally have. Reinforcement and punishmentare too often merely labels for particularcombinations of procedures and results.Presumed reinforcers and punishers are notadequately assessed as independent causalagents. Whatever the shortcomings of thebehavior-regulation approach, it has exertedconsiderable effort to assess alleged causalvariables in the reinforcement situation in-dependent of their presumed effects (Tim-berlake & Allison, 1974).One reviewer suggested that behavior-reg-

ulation phenomena could be explained byrelating the presumed effects of "reinforcers"and "punishers" to the disequilibrium condi-tion produced by the schedule. Reinforce-ment is then a function of the same variablesas behavior regulation, and therefore canreplace it as an explanation for learned per-formance. This sort of free use of the conceptof reinforcement strikes me as akin to aclaim that the physical theory of combustionis simply a more complete characterization

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of the action of phlogiston. The existence ofphlogiston and reinforcers can always be in-voked from their presumed effects, but inthese contexts they are basically superfluousconcepts that are not adequately predictive.

Further, to identify reinforcement withthe determinants of behavior regulation re-quires abandoning many previous assump-tions and practices of reinforcement theory.For example, responding should typically bea bitonic rather than a monotonic or unspec-ified function of variables such as amount ofreward and ratio size. The distinction be-tween the contingent and noncontingent ef-fects of schedules is no longer critical inpredicting performance. The presentation ofa known reinforcer in close temporal andspatial juxtaposition to a response need notproduce reinforcement, and may actuallyproduce punishment. In general, behavior-regulation and reinforcement theories havebeen based on rather different concepts andphenomena. As a result they are not com-pletely interchangeable. We should be work-ing toward an empirical and theoretical in-tegration, not toward "explaining" thephenomena with a term that is not clearlydefined before the fact, and that does notseem to apply in its usual way.The final question of how one knows there

are set-points seems to be nearest the heartof the matter. In general, one knows thereare set-points in the same way one knowsthere is any theoretical concept (e.g., rein-forcement). One defines a measurement pro-cedure for the concept, predicts a relationbetween it and other variables, and deter-mines whether the relations hold. The keycharacteristic of a behavioral set-point is thatit expresses specific instigation. Thus, if theinstigating circumstances remain reliable, soshould the response characteristic. Secondly,if the expression of the instigation in respond-ing is challenged, it should be given upgradually and monotonically with increasedchallenge, not suddenly or nonmonotoni-cally. Third, the response characteristicshould be recoverable, and may show a re-bound in expression following release of con-straint. If a response characteristic has these

properties, we expect it to suport instrumen-tal behavior that reduces schedule constraintimposed on it. If it does not have these prop-erties, we do not expect learned perfor-mance.By way of illustration, if total drinking in

constant circumstances were reliable, if itresisted reduction by challenge through ad-justments of rate or pattern, and if it rapidlyrecovered following release of constraint, wewould be confident that it reflected specificunderlying instigation and would supportinstrumental behavior reducing a scheduleconstraint imposed on it. On the other hand,if total drinking in constant circumstanceswere not reliable, if it were maximally re-duced by any challenge, and if it were notrecoverable following release of constraint,we would conclude that it did not reflectspecific underlying instigation and wouldnot expect it to support instrumental behav-ior. It should be clear that simple alterationsin the environment, such as providing accessto an additional water source, may changedrinking directed to the original watersource from a strongly to a weakly defendedresponse characteristic.Another interesting issue not typically

addressed is the number of potential set-points. It is quite possible that we have onlyscratched the surface of this approach bydealing largely with total instrumental andcontingent responding. Individual back-ground responses may reflect set-points, aswell as measures of more molecular responsecharcteristics such as burst length,topography, or local rate of drinking, ormore molar characteristics such as daily in-take. Further, it may be that reliable levelsof instigation are uniquely related to timeperiods such that instigation is best viewedin the context of particular intervals or struc-tures of responding, such as half-hourperiods, meals, or bouts. I will address someof these issues again in the final section ofthis paper. The next section considers fur-ther questions concerning the importance ofset-points in determining instrumental per-formance, and their relevance to optimalitymodels of learned performance.

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In general, the set-point concept has pro-vided a useful and powerful tool in modelbuilding and predicting behavior. Free-baseline responding serves reliably andreasonably in identifying the circumstancesof reinforcement and in facilitating modelingof absolute schedule performance. Severalcommon misgivings about the use of behav-ioral set-points are not well founded. Thereis nothing magical or mysterious aboutthem. They are simply a priori estimates ofthe instigation for a response that can beused to provide in advance a reasonableestimate of response instigation under aschedule. If we could measure this instiga-tion directly via some physiological index,the assessment and use of behavioral set-points would be unnecessary. Since we can-not, their assessment becomes critical.Whatever its flaws, the behavior-regulationapproach invites, if not demands, empiricalanalysis of the reinforcement situation, notin terms of an arbitrary classification ormanipulation of schedules, but in terms ofthe effects of schedules in expressing andaltering instigation for responding. Basicallythe use of behavioral set-points provides thepossibility of grounding learned perfor-mance in behavior in a more specific waythan has previously been the case.

BEHAVIORAL SET-POINTS INOPTIMAL REGULATION

The accuracy of set-points is particularlyimportant in evaluating a subset of behavior-regulation models based on the assumptionof optimal behavior (e.g., Rachlin &Burkhard, 1978; Rachlin et al., 1981; Stad-don, 1979, 1980). These optimal regulationmodels predict that responding under sched-ule constraint should minimize deviationsfrom behavioral set-points (the bliss point).As Allison (1981a) pointed out, it is difficultto test the minimization prediction directly(instead of in terms of whether the functioncan be adjusted to fit the data), because it isdifficult to establish an a priori basis for scal-ing the deviations of different responses. (Itshould be noted that this problem of a priori

scaling of constants is shared by nearly allbehavioral models.) Appropriate indirecttests might include comparing the bliss pointderived from fitting schedule data with theactual levels of responding obtained in freebaseline, and examining the consistency ofconstants across schedule manipulations.

Allison (1981a) proposed a more directtest of the minimization prediction by argu-ing that subjects should approach as close topresumed behavioral set-points as was phys-ically possible. On the basis of a reanalysis ofpreviously published data, he showed thatanimals working on simple and concurrentratio schedules typically did not achieve theirmaximum possible proximity to presumedset-points. As a result Allison concluded thatthe baseline must not actually represent set-points (ideal points) of behavior and,therefore, that any theory using baselinemeasures as ideal or set-points must be in er-ror. As we shall see, this conclusion is basedon several misapprehensions concerningbehavior regulation and set-points, but thedata are of considerable interest to furtherdevelopment of the behavior-regulation ap-proach.

Simple Ratio SchedulesThe initial data cited in Allison's (1981a)

critique were obtained in studies of rats barpressing on simple ratio schedules that con-trolled access to water (Marwine & Collier,1979) or food (Collier, Hirsch, & Hamlin,1972). These researchers measured free base-line intake of water (or food) and then madeaccess contingent upon bar pressing, over along ascending series of fixed-ratioschedules, followed by a short descending orrandom series of schedules. A critical aspectof the procedure was that each subject wasallowed to set its own amount of reward in-take per access. Each time the reward be-came available, it remained available untilthe animal failed to take any within a fixedtime (5 min for water, 10 min for food), andthen was withdrawn. This indeterminate ac-cess allowed the rat to increase its intake peraccess and thus decrease the effectiveschedule ratio of bar pressing to amount

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of reward, below the initial ratio imposed bythe experimenter. In fact, the data show thatthe rats systematically increased their intakeper access to reward as a function of the ratiorequirement, the greatest intake occurring ator very near the largest requirement.

Allison (1981a) argued that optimal regu-lation theory required each animal toachieve its maximum intake per access at allschedule values, thereby minimizing the dis-tance between the schedule ratio and thebaseline ratio of bar pressing to amount ofreward. Allison made his point with a seriesof plots for each animal which showed thatthe actual ratio of intake per access to barpressing was smaller than it would havebeen had the animal always taken its max-

imum intake of water per access. A minorproblem with this test is that using the entireschedule line as the standard, rather than an

appropriate point of minimal distance,means that data would have been inter-preted as supporting optimal regulationtheory if the subject had completed the ratiorequirement only once and then taken itsmaximum length of intake for that single ac-

cess. In no sense would this result haveminimized deviations from baseline set-points. Since no animal did this, the point isnot critical.

Figures 2 and 3 replot the data in questionas total bar pressing, intake per access, totalintake (drinking or eating), and frequency ofaccess, all as a function of ratio requirement.To reduce them to the same relative scale,all measures are shown as log percentage ofbaseline level. In terms of these plots,Allison's argument is that the line for intakeper access should have gone to maximum atthe first ratio and remained there rather thanshowing systematic increases with increasingschedule challenge. However, there are sev-

eral problems with Allison's assumptionsand analysis.

First, failure to minimize set-point devia-tions is not a general criticism of the use ofset-points in the behavior-regulation ap-proach, but only evidence against optimalregulation. In a simple form, the behavior-regulation approach requires only that

changes in responding under schedule con-straint counteract and be directly related tothe severity of that constraint (Hanson &Timberlake, 1983; Timberlake, 1980). Ascan be seen, the data support the generalbehavior-regulation approach by showing adirect functional relation between degree ofchallenge (fixed-ratio size) and set-pointdeviation.

Second, because the animals took in lessfood or water at each successive ratio, the in-stigation for intake may have varied acrossratios, thus questioning the reasonablenessof a single measurement of the intake per ac-cess as an appropriate general index of theanimal's capacity. Supporting this argumentis the finding that the maximum intake peraccess always occurred at the ultimate orpenultimate ratio requirement (Marwine &Collier, 1979; Collier et al., 1972; it mightbe noted that Allison's reworking of the datashows slightly more variability in the max-imum point). It is important to emphasizethat the animals were not fed or watered out-side the experimental session and that thedata were taken from the ratios administeredin ascending order. The resultant cumula-tive decrease in intake across bar-press re-quirements probably increased the instiga-tion for intake of reward and contributed tothe large increase in intake per access at thehighest ratios. Thus, the maximum intake atthe final ratios probably was not appropriateas an estimate of the "working capacity" ofthe subject at lower ratio schedules, becausethe instigating conditions were different.

Third, the maximum physical capacity ofthe subject in performing a response is notthe primary determinant of responding un-der schedule challenge using any behavior-regulation model. The key to performance isthe regulation of responding with respect todeviations from all relevant set-points. In thecase of optimal regulation theories, asymp-totic performance is determined by simul-taneously minimizing deviations from base-line set-points for instrumental, contingent,and "background" responding (e. g., Stad-don, 1979). Although the concept of "back-ground" responding is not well articulated,

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in fairness to current theories Allison's criti-que should have considered the potentialcontribution of a set-point for backgroundresponding. Finally, these data also indicatethat a complete theory of learned perfor-mance must consider the possibility ofdefended response patterns, set-points of

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clusively choose the most liberal of two ratioschedules as would occur if they were ap-proaching baseline set-points as closely as

possible (Herrnstein & Loveland, 1975; Lea& Roper, 1977; Shapiro & Allison, 1978). Inpresenting the data, Allison constructed twopotential outcomes - all responding on themore liberal schedule or all responding on

the more conservative schedule. He thenplotted the obtained ratio of responding,which generally fell between the two extreme

outcomes, though most often closer to theliberal alternative.Again this test does not bear on the

general behavior-regulation approach, andit is imprecise because responding anywhereon the minimum schedule line would havebeen taken as supporting optimal regulationtheory. Other important issues are the po-

tential contribution of interference effects onmemory, discriminability of reward rates,and the baseline frequency of switching be-

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WILLIAM TIMBERLAKE

tween alternative sources of reward. TheShapiro and Allison (1978) study ofbar press-ing for food in rats prevented the uniquerelation of a particular bar with a scheduleby reversing the relation from day to day.Allison (1981a) claimed that this proceduredid not affect the results because he infor-mally observed sampling of both scheduleslate as well as early in each session.Presumably, the rats would have learnedwhich bar was correlated with the moreliberal schedule within the first few minutesof the session. However, this suppositionmay be too strong. Daily switching of theschedules between two bars might well pro-duce considerable proactive interference.Shapiro and Allison (1978), for example,reported that data for one animal showed ashift from a three-to-one to a five-to-onepreference after twenty choices of each bar.The other experimenters mentioned

(Herrnstein & Loveland, 1975; Lea &Roper, 1977) followed the more typical pro-cedure of correlating each schedule with aunique location and obtained results that inmost cases reflected a preference for themore liberal schedule. Their findings arealso supported by more recent work reportedby Herrnstein and Vaughan (1980) and byKrebs, Kacelnik, and Taylor (1978). How-ever, the pattern of data does raise a ques-tion of discriminability of rate of rewardunder the two schedules. The studies of bothLea and Roper (1977) and Herrnstein andLoveland (1975) revealed more nearly ex-clusive preferences for the liberal schedulewhen the schedules differed considerably. Atvery similar ratio requirements (FR 8 vs. FR11; FR 6 vs. FR 8) or overlapping ratios(VR 25 vs. VR 35; VR 50 vs. VR 70) re-sponding tended toward indifference be-tween the two schedules.The data are also compatible with the ex-

istence of a baseline tendency (set-point) tosample alternative sources of food, a ten-dency that is expressed most clearly underlow instrumental requirements, and de-creases systematically under increasingschedule challenge. The pigeons of Herrn-stein and Loveland (1975) showed a moder-

ate initial tendency to sample both responses,a tendency that decreased in favor of ex-clusive preference for the more liberalschedule as a function of the strictness of theleaner schedule (Allison, 1981a, Figure 10).Thus, the greater the difference between thetwo schedules, the more likely the animalswere to exclusively prefer the more liberalschedule. A similar trend is shown in thedata of Lea and Roper (1977) between thebottom two figures and the top two (Allison,1981a, Figure 8), and in the data of Shapiroand Allison (1978, Table 1).A tendency to sample alternative and even

depleted sources of food has been frequentlycited as a sound evolutionary strategy forforaging in patchy environments (Krebs,1978; McNamara & Houston, 1980; Smith& Sweatman, 1974). Depleted resources areoften renewed and plentiful resources aredepleted at unpredictable intervals. Thus, atendency to sample alternative sources of acommodity would be expected because itcould easily be an advantage in makingmaximum use of available resources. It maybe important that the animals in Lea andRoper's (1977) study showed the mostsampling, because their alternative sourcesof food were at spatially different locations.This might be more typical of sampling innatural circumstances than a situation suchas Herrnstein and Loveland's (1975) inwhich alternative forms of the same responseproduced access to food at the same location.Taking the simple and concurrent-ratio

data together, the force of Allison's (1981a)critique of behavioral set-points and optimalregulation is weak. The criticism does notapply to regulatory theories in a generalway, and its application to optimal regula-tion theory can be questioned. There aremany bases for the results cited other thanthe failure of the animal to minimize itsdistance from baseline set-points. Themeasure of physical capacity on which theargument turns was obtained at what ap-peared to be the highest level of a variabledeprivation regime, and the interpretationfailed to consider the effects of set-points ofbackground responding in meliorating the

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BEHA VIOR REGULATION AND LEARNED PERFORMANCE

predicted outcome. Further, failure alwaysto choose the most liberal of the concurrentlyavailable ratio schedules was confoundedwith problems of memory interference andschedule discriminability. Finally, impor-tant regularities in both the simple andconcurrent-ratio data suggest that behavioris regulated around more than simple molarset-points, including baseline patterns ofcontingent responding and the tendency tosample alternative reward sources.

RESPONSE-PATTERN SET-POINTSAND MOLAR REGULATION

As indicated in the introduction, mostregulatory theorists have assumed that thechange in total instrumental responding un-der a schedule was determined by a molardisequilibrium condition involving the set-points of total instrumental and contingentresponding (and perhaps background re-sponding). However, a rather different viewof the appropriate level of analysis has beenadvanced by Premack (1971) and by Dun-ham (1977). These authors argued that thechange in total instrumental responding re-sults from schedule constraints on local re-sponse patterns (response-pattern set-points).Specifically, Dunham (1977) claimed thatthe key to increased instrumental respond-ing was a schedule that decreased the burstlength of contingent responding and in-creased its interburst interval. Premack(1971) argued in a similar vein that the keyto reinforcement was an increase in themomentary probability of the contingentresponse, presumably related to decreasedburst length and/or increased interburst in-terval imposed by the schedule.

Their fundamental argument, that theoverall change in instrumental responding isdriven by deviations from response-patterncharacteristics rather than by deviationsfrom total responding, has not been testedadequately. There is some evidence thatresponse patterns serve as set-points-thatthere is unique instigation for a particularpattern of responding. Schedules that con-strain the patterns of contingent responding

produce increases in the local probability orrate of the contingent response under sched-ule constraint (Lucas, 1981; Terhune, 1978;Timberlake, 1979), although contradictorydata have been provided by Mazur (1977)and by Bernstein and Dearborn (1978,reported in Timberlake, 1980). However,there has been no independent assessment ofthe effects of deviations from response-pattern set-points on molar instrumentalresponding.The major problem in assessing the im-

portance of response-pattern set-points isthat constraints on response patterns andconstraints on total contingent respondingare usually completely confounded. A typi-cal schedule imposes similar a priori restric-tions on molar and response-pattern charac-teristics, so that both approaches make thesame predictions of effects on instrumentalresponding. For example, a ratio schedulethat constrains the subject's total access toeating typically reduces its burst length andincreases its interburst interval relative tobaseline. Thus, both views predict an in-crease in instrumental responding, and onecannot separate the potential contributionsof the two sources.

An Important TestThe work of Marwine and Collier (1979)

and Collier et al. (1972), discussed above, isunique in that the procedure of indetermin-ate access to the contingent response permit-ted evaluation of the relation between devia-tions from molar and response-pattern base-lines, and made possible assessment of theirrelative importance in driving increases intotal instrumental responding. The key prop-erty of the procedure is that it allowed an in-strumental requirement to constrain totalcontingent responding without placing anyconstraint on the intake per access to thecontingent response. As a result, these dataprovide a test of four possible relationsamong deviations from molar and response-pattern set-points in determining total in-strumental responding. (1) If deviationsfrom response-pattern set-points are the keyelement, two things would be expected: (a)

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maintenance of the intake per access at base-line level (inasmuch as this is not con-strained), and (b) slow decrease in frequencyof access with increasing challenge accom-panied by rapid increase in bar pressing tocombat the constraint of the bar-press re-quirement for access. (2) If only deviationsfrom total response set-points are critical,one would expect response-pattern charac-teristics to be given up instantly to the max-imum extent possible, thus allowing mainte-nance of total instrumental and contingentresponding (e.g., intake per access shouldimmediately increase to its maximum, main-taining total intake without requiring amarked increase in bar pressing). (3) Iflevels of response characteristics have ef-fects, but one or the other is the morecritical, all characteristics should showsystematic deviations from baseline with in-creasing schedule challenge, but eithermolar or response-pattern characteristicsshould be given up more rapidly. (4) Ifmolar and response-pattern set-points areequally important, we would expect to findparallel rates of change with increasingschedule constraint.The data in Figures 2 and 3 contradict

three of these possibilities and provide strongevidence for both response-pattern and totalresponse set-points. By way of reminder,these figures show the log percentage ofbaseline plotted as a function of ratio re-quirement for total bar presses, intake peraccess, total intake, and frequency of intake.Figure 2 represents rats' bar pressing thatproduced access to water (Marwine & Col-lier, 1979), and Figure 3 represents rats' barpressing that produced access to food (Col-lier et al., 1972). None of the responsecharacteristics was either preserved or givenup immediately. Instead, deviations fromthe baseline of each measure were a mon-otonic increasing function of degree of con-straint. However, the baseline character-istics did not appear to be equally resistant tochange. Bar pressing, intake per access, andaccess frequency showed rapid initialchanges for all animals, followed by fairlystable asymptotes for intake per access and

access frequency, and by a slowed rate of in-crease for bar pressing.

In contrast to these measures, total wateror food intake showed a very slow rate of de-crease across increasing schedule challenge.If we refer to the initial rate of change of acharacteristic as its resistance to change, andthe maximum change as its flexibility, thenwithin the range of schedules used the datacan be described: The response-pattern char-acteristics of intake per access and access fre-quency showed low resistance to change andrelatively high flexibility; the molarcharacteristic of total bar pressing showed lowresistance to change and still greater flexibil-ity; total intake showed high resistance tochange and relatively low flexibility.

Thus, these data both support the ex-istence of response-pattern set-points andcontradict the notion that deviations fromthem are the primary determinant of in-strumental responding in molar contingen-cies. Despite the absence of constraint on in-take per access, there were large increases intotal bar pressing. It might be argued thatthe increase in bar pressing was the result ofconstraints on frequency of access, but thischaracteristic was given up to the maxi-mum possible extent almost immediately-scarcely what would be anticipated for acritical causal variable. Further, there wasan unforced increase in the burst length ofthe contingent response to well above itsbaseline, an outcome completely at oddswith any theory that deviations from re-sponse patterns are the critical determinantof molar schedule performance. By the pre-dictions of Dunham (1977), such an increasein the burst length of the contingent re-sponse should have produced punishment ofbar pressing rather than reinforcement.Thus, instead ofbeing the fundamental driv-ing force in the system, deviations fromresponse-pattern set-points appear to bedriven by deviations from total intake, andto a lesser extent by deviations from total barpressing. At least in the case of waterreward, maximum bar pressing occurredonly after near maximum changes inresponse patterns were obtained.

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Practical Problems and Future DirectionsThe possibility of sharply increasing the

number and importance of presumed set-points relevant to learned performanceraises two important questions: First, howmany set-points are there and can each onebe independently justified? Second, what isthe relation among the different set-points?Last, given its power and flexibility, how canthe behavior-regulation approach be inte-grated with other ways of viewing thelearned performance situation?On the first question, the concept of set-

points may have seemed harmless enoughwith only two or three, but with potentiallylarge numbers of set-points facing us, whereshould we stop? In other words, how doesone guard against invoking imaginary set-points whenever it seems necessary to ex-plain some irregularity in the data? Theanswer is in two parts. First, there should bea theoretical or consistent empirical reasonfor exploring the possibility that a particularresponse characteristic serves as a set-point.Second, the purported set-point must passthe criteria discussed previously. Any set-point is identified by (1) reliability andrecoverability under conditions of minimalconstraint and constant instigation; (2) adirect and gradual monotonic relation be-tween the amount of deviation and thedegree of challenge; (3) the ability to supportinstrumental behavior leading to reductionin constraint. The interdependence andcompensatory nature of changes in respond-ing also may provide evidence for the ex-istence of multiple set-points.

It is not the case, as one reviewer argued,that a set-point is inferred on the basis ofany functional relation between dependentand independent variables. Set-points areinferred only when there is a direct relationbetween deviations from the baseline of areliable and recoverable response character-istic and increasing challenge to its expres-sion. Schedule constraint on the responsecharacteristics should also increase respond-ing that is instrumental in reducing the con-straint. For example, that latency to eat in anovel environment is inversely related to

hours without food does not suggest thatlatency to eat is a set-point. However, latencyto eat under a particular set of environmen-tal and organismic circumstances couldserve as a set-point supporting bar pressinginstrumental in maintaining a low latency.

Caution must be exercised in identifyingset-points when several response character-istics are related and there is no independenttest of the regulatory effects of each one. Inthe data above (Marwine & Collier, 1979;Collier et al., 1972) molar and response-pattern measures were related in that totalintake could be determined by the frequencyof access multiplied by the average intakeper access, and frequency of access could bedetermined by total bar presses divided bythe ratio requirement. Do these relationsmean that only two set-points are possible(in the sense that there are only two indepen-dent measures of total or average respondingafter the experimenter has determined theschedule)? The answer is no, because themathematical relations among the measuresdo not necessarily predict the form of thedeviation functions with increasing chal-lenge. For example, if the animal were con-cerned only with deviations from total in-strumental and contingent responding, thenone would expect a maximum increase in in-take per access at the first challenge; in-stead, intake per access changed system-atically with degree of challenge up to someasymptotic degree of change. Similararguments can be made by taking intake peraccess and instrumental responding, or in-take per access and contingent responding,as two set-points and determining whetherchanges in the remaining response appear toreflect only tendencies to reduce deviationsfrom the other two.However, such a careful analysis casts

doubt on the independent effects of thefourth measure, frequency of access. If weassume that the other three measures repre-sent set-points, then the form of the relationbetween changes in frequency of access anddegree of challenge can be seen as deter-mined by compromises among the deviationsfrom the other three set-points. It is clear

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WILLIAM TIMBERLAKE

that with multiple related response mea-sures, reliability and recoverability cannotbe considered the sole criteria of a behavioralset-point. A test of the ability of eachresponse characteristic alone to controlregulatory behavior is necessary. In the caseof frequency of access, it cannot be manipu-lated while holding constant the deviationsfrom total responding and burst length, butperhaps a choice situation could be devel-oped in which deviations from frequency ofaccess and burst length were pitted againsteach other.The second issue, that of modeling the

relation among different set-points, has onlybeen broached. Previous work has treated allpresumed set-points the same, with littlespecific concern with their unique character-istics and relations (Staddon, 1979; Timber-lake & Allison, 1974). The data describedhere clearly suggest the existence of a hierar-chical relation between the set-points of totalintake and the set-points related to responsepatterns. Deviations from response-patterncharacteristics did not appear to drive totalbar pressing, but deviations from total barpressing and intake did appear important indetermining response patterns. However, itis not yet clear how deviations from re-sponse-pattern set-points are related tochanges in response patterns, whether theserelations involve different time periods of in-tegration as would be expected under a hier-archical control system (Powers, 1978), andto what extent relations depend upon thepresence of the schedule. Further develop-ment of the behavior-regulation approachmight well explore questions of hierarchy,periods of integration of set-points, and therole of learning in modifying existing controlsystems. Finally, as suggested earlier, acomplete model of behavior regulation couldeliminate the necessity of requiring abaseline assessment of instigation over thesame time course and under the same condi-tions as the subsequent schedule constraint.The last problem, that of integrating the

behavior-regulation view with more typicalcontrol theory and reinforcement notions,

may well be critical in further developnmentof a general theory of learned performance.As noted previously, part of the difficulty inaccepting the concept of behavioral set-points is the historical ties between set-pointsand presumably inflexible physiologicalmechanisms. In fact, in both physiology andbehavior, the term set-point could be replacedby the term defended characteristic, which playsdown the notion that there is a single criticalpoint. There is suggestion that set-pointsmay function more as bi-directional thresh-olds than as individual points. Compensa-tory reactions to deviations from baselineresponding may occur only for deviationsgreater than a threshold value. This thresh-old may vary as a function of the direction ofthe deviation from baselines, as well as withthe expression characteristics and baselinesof the response combinations involved. Forthe time I prefer the term set-point because itincludes all these uses and creates specificconnections with the powerful concepts andinodels of control theory (Hanson & Timber-lake, 1983; Powers, 1978).The integration of behavior regulation

and the traditional reinforcement view ismost hindered by habitual patterns of think-ing about reinforcement. It appears quitedifficult to consider learned performance interms of reinforcement theory and behaviorregulation at the same time (cf. Rachlin &Burkhard, 1978; Rachlin et al., 1981). Con-cepts are filtered and translated in awkwardways in moving from one approach to theother. This is obvious in the comments ofreviewers, in textbook treatments, and in in-teractions with colleagues and students. Inmy experience it was necessary to let gomany preconceptions about the action ofreinforcers to get to the behavior-regulationapproach, even given the reasonably cleardirection pointed by Premack (1965, 1971).In the past investigators have appeared toembrace one or the other viewpoint. Sinceboth approaches have defensible aspects, Iam hopeful, but not entirely sanquine, thatwe can move toward a more integrated view(see Timberlake, 1983).

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CONCLUSIONS

The behavior-regulation approach tolearned performance provides a unique andpotentially powerful mechanism, the regula-tion of disparities between instigation andexpression of behavior, for the identificationof the circumstances of reinforcement andthe prediction of asymptotic performanceunder schedules. The present paper clarifiesseveral of its assumptions and procedures.First, behavior regulation does not imply aparticular physiological model of responsedeterminants, only reliable levels of responseinstigation and the mechanism to translatedisparities between instigation and expres-sion into instrumental behavior. Second,behavioral set-points are not arbitrarilychosen, but are identified by their invarianceand recoverability under conditions of reli-able instigation and minimum constraint,and by the functional relation betweendegree of challenge and amount of deviationfrom them. The free baseline, although itdoes not account for all determinants ofresponding, appears to provide a reasonableindex of basic instigation.

Third, that animals may fail to exert max-imum physical effort to minimize deviationsfrom presumed set-points of instrumentaland contingent responding (Allison, 1981a)was shown to be irrelevant to the generalbehavior-regulation approach, and to be ofquestionable relevance to optimal behaviorregulation. Fourth, the question of whetherinstrumental responding is driven by devia-tions from response-pattern or total-responding set-points was resolved in twoways. First, there was reasonable evidencethat response patterns could serve as set-points. Second, in the data considered, devi-ations from response-pattern characteristicsnot important in driving instrumentalresponding; rather, deviations from total in-take were important in driving deviationsfrom response-pattern characteristics. It issuggested that future work focus on thestudy of different levels of behavioral set-points and their relations, as well as promote

the development of a more complete view oflearned performance.

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suppression, and conservation. Joumal of the Experi-mental Analysis of Behavior, 25, 185-198.

Allison, J. (1981a). Paired baseline performance as abehavioral ideal. Journal of the Experimental Analysisof Behavior, 35, 355-366.

Allison, J. (1981b). Economics and operant condi-tioning. In P. Harzem & M. D. Zeiler (Eds.),Advances in analysis of behaviour: Vol. 2. Predictability,correlation and contiguity (pp. 321-353). Chichester:Wiley.

Allison, J., & Boulter, P. (1982). Wage rate, non-labor income, and labor supply in rats. Learning andMotivation, 13, 324-342.

Allison, J., Miller, M., & Wozny, M. (1979). Con-servation in behavior. Journal of Experimental Psy-chology: General, 108, 4-34.

Allison, J., & Timberlake, W. (1974). Instrumentaland contingent saccharin licking in rats: Responsedeprivation and reinforcement. Learning and Moti-vation, 5, 231-247.

Allison, J., & Timberlake, W. (1975). Response de-privation and instrumental performance in thecontrolled-amount paradigm. Learning and Motiva-tion, 6, 112-142.

Atkinson, J. W., & Birch, D. (1970). The dynamics ofaction. New York: Wiley.

Bernstein, D. J., & Dearborn, M. (1978). Utility oftime-based theories of reinforcement in human behavior.Unpublished manuscript, University of Nebraska,Lincoln.

Bolles, R. C. (1980). Some functionalistic thoughtsabout regulation. In F. M. Toates & T. R. Halli-day (Eds.), Analysis of motivational processes (pp.63-75). New York: Academic Press.

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Received March 7, 1983Final acceptance February 24, 1984