Habituation To The Reinforcer May Contribute To Multiple-schedule Behavioral Contrast

An investigation of variety effects during operant responding in the rat utilizing different reward flavors

Humans and nonhuman animals respond to food diversity by increasing intake and appetitive behaviors, reflecting enhanced valuation for items presented in the context of variety. Previous work on food variety effects has posited two main explanatory mechanisms. Variety could slow habituation processes by decreasing exposure to a single food item or could elicit contrast effects in which comparisons between items impact relative valuation. This study used three flavors of sucrose rewards to investigate rats' responses to qualitative reward variety in different variety contexts: low (2 flavors) and high (3 flavors) conditions. Control sessions used only a single flavored pellet (no variety). Animals were tested in low (10 trials), moderate (20 trials) and high consumption (30 trials) sessions. A trial within each session was defined as completion of the operant response and acquisition of the reward pellet. Cues associated with flavors were used to examine predictability and between-trial ('micro') variety. Indicators of a variety effect were found including faster responding for rewards during the variety context compared to an initial control (no variety) context. This decrease in response latency continued to be observed for some measures in post-variety control contexts. The most robust statistical finding of variety effects was found using trial-by-trial analysis, with shorter response latencies obtained for trials with outcomes differing from the preceding trial compared to successive trials with identical outcomes. These results have implications for understanding how a general reward context like variety impacts behavior, and for informing clinical approaches focusing on motivation and eating disorders.

An examination of within-session responding following access to reinforcing stimuli

Previous research has shown tangibly maintained challenging behavior can be temporarily decreased by providing presession access to the relevant tangible. However, the duration of this beneficial effect is unknown. We measured the subsequent duration of behavior reduction effects following presession access during extended classroom observation sessions by analyzing within-session patterns of responding in three children with autism. An alternating treatments design was used to analyze within- and across-session responding following presession access and presession restriction conditions. The cumulative frequency of challenging behavior was higher following the presession restriction condition for all participants and lower following presession access. Within-session analysis revealed the same basic pattern of responding across participants. Specifically, the first half of the sessions contained very little, if any, challenging behavior; however, after 60 min, the rate of challenging behavior began to increase rapidly for two of the three participants. Results are discussed in terms of implications for practitioners, satiation, habituation, and behavioral contrast.

Altering participants' hypothetical annual income can alter their rates of discounting the same delayed monetary outcome

Delay discounting occurs when the subjective value of an outcome decreases because its delivery is delayed. Past research has shown that how steeply participants discount an outcome varies inversely with the value of previously discounted outcomes. In the present study, participants discounted the same hypothetical monetary outcome ($1,000) after their hypothetical annual income was halved (Experiment 1) or doubled (Experiment 2). Rates of discounting decreased and increased, respectively, after these manipulations (although a similar change in discounting was observed for the control and treatment groups in Experiment 2). These results suggest that altering the context in which the discounting task is framed alters the subjective value of the outcome itself, in this case money. This result has implications for understanding contrast effects that are observed in rates of discounting, as well as for researchers and practitioners who are interested in determining methods for altering how individuals discount delayed outcomes.

Dynamic changes in reinforcer effectiveness: satiation and habituation have different implications for theory and practice

Reinforcers lose their effectiveness when they are presented repeatedly. Early researchers labeled this loss of effectiveness as satiation without conducting an experimental analysis. When such an analysis is conducted, habituation provides a more precise and empirically accurate label for the changes in reinforcer effectiveness. This paper reviews some of the data that suggest that habituation occurs to repeatedly presented reinforcers. It also argues that habituation has surprisingly different implications than satiation for theory and practice in behavior analysis. For example, postulating that habituation occurs to repeatedly presented reinforcers suggests ways for maintaining the strength of an existing reinforcer and for weakening the strength of a problematic reinforcer that differ from those implied by an account in terms of satiation. An habituation account may also lead to different ways of conceptualizing the regulation of behavior. For example, habituation may be a single-process contributor to the termination of behaviors that are usually attributed to satiation (e.g., ingestive behaviors such as eating and drinking), fatigue (e.g., energetic behaviors such as running), the waning of attention (e.g., cognitive behaviors such as studying), and pharmacodynamic factors (e.g., drug taking).

The Role of Shaping the Client's Interpretations in Functional Analytic Psychotherapy

Clinical behavior analysis often targets the shaping of clients' functional interpretations of/or rules about his own behavior. These are referred to as clinically relevant behavior 3 (CRB3) in functional analytic psychotherapy (FAP). We suggest that CRB3s should be seen as contingency-specifying stimuli (CSS), due to the their ability to change the function of stimuli-including descriptions of variables involved in the client's behavioral problems as well as descriptions of variables associated with improvement or therapeutic change. This paper discusses the role of rule-governed behavior in FAP and the processes of shaping client interpretations of his or her behavior, and proposes that this may be an overlooked and important mechanism of change in FAP. To shape CRB3 in FAP, the therapist describes CSSs related to the therapy relationship that are consistent with the client's social environment, and reinforces improvements of the client's following his or her own newly shaped CSS descriptions during the session.

Sensitization and habituation regulate reinforcer effectiveness

We argue that sensitization and habituation occur to the sensory properties of reinforcers when those reinforcers are presented repeatedly or for a prolonged time. Sensitization increases, and habituation decreases, the ability of a reinforcer to control behavior. Supporting this argument, the rate of operant responding changes systematically within experimental sessions even when the programmed rate of reinforcement is held constant across the session. These within-session changes in operant responding are produced by repeated delivery of the reinforcer, and their empirical characteristics correspond to the characteristics of behavior undergoing sensitization and habituation. Two characteristics of habituation (dishabituation, stimulus specificity) are particularly useful in separating habituation from alternative explanations. Arguing that habituation occurs to reinforcers expands the domain of habituation. The argument implies that habituation occurs to biologically important, not just to neutral, stimuli. The argument also implies that habituation may be observed in "voluntary" (operant), not just in reflexive, behavior. Expanding the domain of habituation has important implications for understanding operant and classical conditioning. Habituation may also contribute to the regulation of motivated behaviors. Habituation provides a more accurate and a less cumbersome explanation for motivated behaviors than homeostasis. Habituation also has some surprising, and easily testable, implications for the control of motivated behaviors.

Investigating the devaluation explanation for negative anticipatory contrast

This study addressed whether negative anticipatory contrast results in a decrease in the value of the low-valued substance. Rats responded in training conditions designed to produce negative contrast. They then responded in test sessions in which the low-valued substance from the training sessions was the reinforcer for an operant response. Despite the finding of contrast in the training conditions, the low-valued substance was a more effective reinforcer early in testing after training conditions in which it had been followed by access to the high-valued substance than after training conditions in which it had not. The findings question the devaluation explanation for contrast but may be similar to other findings of reversals of "preference."

Duration, response, and location: the influence of upcoming 32% sucrose on rats' licking or lever pressing for 1% liquid sucrose

The present study investigated whether rats' rates of licking or pressing a lever for 1% liquid sucrose delivered by a continuous reinforcement schedule would decrease (contrast) or increase (induction) when the upcoming period would allow access to 32% sucrose and whether such changes would be influenced by how long each substance was available. In Experiment 1, different groups of rats licked a spout or pressed a lever for 1% sucrose in the first half of the session and, in different conditions, for 1% or 32% sucrose in the second half. Across conditions, halves of the session were 3, 6, 12, or 24 min long. Upcoming 32% sucrose significantly decreased rates of licking at each duration whereas it increased rates of lever pressing except when access duration was 3 min. Experiment 2 replicated Experiment 1 with the exception that rats that licked did so from the same spout in both halves of the session and rats that pressed a lever collected the sucrose reinforcers in the different halves at different locations. In these procedures, upcoming 32% sucrose significantly increased rates of licking. Significant, but small, increases in rates of lever pressing were still observed. The present results suggest that continuous reinforcement or duration of access to sucrose are not primary determinants of whether contrast or induction is observed. Rather, they suggest that the type of behavior (licking versus pressing a lever) and the location at which the substances are collected and consumed play a large role in which effect occurs.

Varying reinforcer duration produces behavioral interactions during multiple schedules

The experiments tested the idea that changes in habituation to the reinforcer contribute to behavioral interactions during multiple schedules. This idea predicts that changing an aspect of the reinforcer should disrupt habituation and produce an interaction. Pigeons and rats responded on multiple variable interval variable interval schedules. Introducing variability into the duration of reinforcers in one component increased response rates in both components when the schedules provided high, but not low, rates of reinforcement. The increases in constant-component response rates grew larger as the session progressed. Within-session decreases in responding were smaller when the other component provided variable-, rather than fixed-, duration reinforcers. These results are consistent with the idea that changes in habituation to the reinforcer contribute to behavioral interactions. They help to explain why interactions do not occur for some subjects under conditions that produce them for others. Finally, the results question the assumption that induction and behavioral contrast are always produced by different theoretical mechanisms.

Within-session rates of responding when reinforcer magnitude is changed within the session

In the present experiment, the authors investigated the idea that within-session changes in operant response rates occur because subjects sensitize and then habituate to the reinforcer. If that is true, then altering an aspect of the reinforcer within the session should alter the observed within-session responding. The authors tested that idea by having rats press a lever for 2 food-pellet reinforcers delivered by a variable-interval 120-s schedule during 60-min baseline sessions. In treatment conditions, the magnitude of the reinforcer was halved (1 pellet) or doubled (4 pellets) 10, 20, 30, 40, or 50 min into the session. That magnitude of reinforcement then remained in effect for the rest of the session. Altering reinforcer magnitude altered the rates of responding within the session in a fashion consistent with the habituation explanation, that is, response rates increased, relative to baseline, when the magnitude of reinforcement was increased. They decreased when the magnitude was decreased. Those results were seemingly inconsistent with the competing idea that within-session decreases in responding rates are produced by satiation.

Dynamic changes in reinforcer effectiveness: theoretical, methodological, and practical implications for applied research

Reinforcers lose their effectiveness when they are presented repeatedly. Traditionally, this loss of effectiveness has been labeled satiation. However, recent evidence suggests that habituation provides a more accurate and useful description. The characteristics of behavior undergoing satiation differ for different stimuli (e.g., food, water), and these characteristics have not been identified for the noningestive reinforcers often used by applied behavior analysts (e.g., praise, attention). As a result, the term satiation provides little guidance for either maintaining or reducing the effectiveness of reinforcers. In contrast, the characteristics of behavior undergoing habituation are well known and are relatively general across species and stimuli. These characteristics provide specific and novel guidance about how to maintain or reduce the effectiveness of a reinforcer. In addition, habituation may lead to a better understanding of several puzzling phenomena in the conditioning literature (e.g., extinction, behavioral contrast), and it may provide a more precise and accurate description of the dynamics of many different types of behavior.

The relation of multiple-schedule behavioral contrast to deprivation, time in session, and within-session changes in responding

Pigeons' keypecking was reinforced by food on baseline schedules of multiple variable interval (VI) x VI x and on contrast schedules of multiple VI x VI y. Deprivation of food was varied by maintaining subjects at 75%, 85%, and 95% (+/- 2%) of their free-feeding weights. Positive and negative behavioral contrast were observed. The size of the contrast was not systematically altered by changes in deprivation. Positive and negative contrast were both larger later in the session than they were earlier. Within-session decreases in responding were steeper for the baseline than for the contrast schedules for positive contrast. Within-session decreases were steeper for the contrast than for the baseline schedules for negative contrast. These results were predicted by the idea that different amounts of habituation to the reinforcer during the baseline and contrast schedules contribute to behavioral contrast. The results show that contrast occurs under conditions that reduce the effect of the following component. The results support the assumption that positive and negative contrast are produced by symmetrical theoretical variables.

Effect of upcoming reward type when rats press a lever for ethanol

Rats' operant responding for sucrose rewards in the 1st half of a session can vary directly with the conditions of reward in the 2nd half. The authors investigated whether that induction effect represented an animal model of emotive states. Rats pressed a lever for either ethanol or sucrose rewards in the 1st half of a 40-min session. The reward in the 2nd half of the session was, across conditions, 1% sucrose, a food pellet, or the same reinforcer delivered in the 1st half. When subjects responded for sucrose, upcoming reward type had little influence on responding in the 1st half of the session. However, when subjects responded for ethanol, upcoming 1% sucrose and food-pellet reinforcement both produced increases in responding. The results suggest that the procedure produced different emotive states, but further work is needed to support such a model. The results also have potential applied implications.

Reinforcement context and resistance to change

Eight pigeons responded in a multiple variable-interval (VI) schedule in which a constant component always delivered 40rft/h, and an alternated component was either rich (200rft/h) or lean (6.67rft/h) in different conditions. Four tests of resistance to change were conducted in each condition: prefeeding, full extinction, constant-component-only extinction, and response-independent food. Resistance to both prefeeding and full extinction in the constant component varied inversely with the reinforcement rate in the alternated component, but resistance to response-independent food did not. The extinction and response-independent food results were consistent with [J. Exp. Psychol.: Anim. Behav. Proc. 25 (1999) 256] behavioral momentum model. Maintaining reinforcement in the alternated component increased resistance to extinction in the constant component, as predicted by the behavioral momentum model but not accounts of multiple-schedule performance based on [J. Exp. Anal. Behav. 13 (1970) 243] equation. Overall, the momentum model gave a good account of the results with the exception of the prefeeding data. Possible ways to reconcile the prefeeding results with behavioral momentum theory are considered.

Dishabituation with component transitions may contribute to the interactions observed during multiple schedules

Rates of responding by rats were usually higher during the variable interval (VI) 30-s component of a multiple VI 30-s fixed interval (FI) 30-s schedule than during the same component of a multiple VI 30-s VI 30-s schedule (Experiment 1). Response rates were also usually higher during the FI 30-s component of a multiple VI 30-s FI 30-s schedule than during the same component of a multiple FI 30-s FI 30-s schedule (Experiment 2). The differences in response rates were not observed when the components provided VI or FI 120-s schedules. These results were predicted by the idea that differences in habituation to the reinforcer between multiple schedules contribute to behavioral interactions, such as behavioral contrast. However, differences in habituation were not apparent in the within-session patterns of responding. Finding differences in response rates in both experiments violates widely-held assumptions about behavioral interactions, including that behavioral contrast does not occur for rats and that improving the conditions of reinforcement decreases, rather than increases, response rate in the alternative component.

On the determinants of induction in responding for sucrose when food pellet reinforcement is upcoming

Rats' rates of leverpressing for low-concentration liquid-sucrose reinforcers in the first half of an experimental session increase when food pellet, rather than sucrose, reinforcers will be available in the second half. Experiment 1 determined that this induction effect was the outcome of food pellet reinforcement's increasing response rates, not of continued sucrose reinforcement's decreasing them. Experiments 2 and 3 showed that induction was primarily controlled by the conditions of reinforcement in the current session, not by those in the previous one. Experiment 4 showed little evidence that the induction was the outcome of Pavlovian processes. These results suggest that induction may occur because of processes operating at the level of the entire session. They also provide a link to a seemingly related area of study: contrast effects. Some of the results are consistent with what is known about contrast effects, but there are also several, yet unexplained differences.

Common processes may contribute to extinction and habituation

Psychologists routinely attribute the characteristics of conditioned behavior to complicated cognitive processes. For example, many of the characteristics of behavior undergoing extinction have been attributed to retrieval from memory. The authors argue that these characteristics may result from the simpler process of habituation. In particular, conditioned responding may decrease during extinction partially because habituation occurs to the stimuli that control responding when those stimuli are presented repeatedly or for a prolonged time (e.g., the experimental context, the conditioned stimulus in classical conditioning). This idea is parsimonious, has face validity, and evokes only processes that are well established by other evidence. In addition, behavior undergoing extinction shows 12 of the fundamental properties of behavior undergoing habituation. However, this model probably cannot provide a complete theory of extinction. It provides no obvious explanation for some of the other characteristics of extinguished behavior.

Up or down: the influence of upcoming reinforcement on consummatory and operant behavior

Research has shown that animal subjects that are given a chance to consume a low-valued substance will consume less of it if a high-valued substance will soon be available than they would if the low-valued substance were to remain available (negative consummatory contrast). Research has also shown that subjects that lever press for a low-valued reinforcer will press the lever more often for that reinforcer if they will soon be able to lever press for a high-valued reinforcer than they would if they continue to press for the low-valued reinforcer (positive induction). The present study investigated these different changes in behavior across 3 experiments. The results suggest that the occurrence of contrast or induction does not depend on the type of substances that are used. We argue that further investigation of the contrast vs. induction issue is warranted because it has empirical, theoretical, and applied implications.

Behavioral contrast redux

Behavioral contrast is defined as a change in response rate during a stimulus associated with a constant reinforcement schedule, in inverse relation to the rates of reinforcement in the surrounding stimulus conditions. Contrast has at least two functionally separable components: local contrast, which occurs after component transition, and molar contrast. Local contrast contributes to molar contrast under some conditions, but not generally. Molar contrast is due primarily to anticipatory contrast. However, anticipatory contrast with respect to response rate has been shown to be inversely related to stimulus preference, which challenges the widely held view that contrast effects reflect changes in stimulus value owing to the reinforcement context. More recent data demonstrate that the inverse relation between response rate and preference with respect to anticipatory contrast is due to Pavlovian contingencies embedded in anticipatory contrast procedures. When those contingencies are weakened, anticipatory contrast and stimulus preference are positively related, thus reaffirming the view that the reinforcing effectiveness of a constant schedule is inversely related to the value of the context of reinforcement in which it occurs. The underlying basis of how the context of reinforcement controls reinforcement value remains uncertain, although clear parallels exist between contrast and the effects of contingency in both Pavlovian and operant conditioning.

Three tests of 'anticipatory responding' as an account for induction produced by upcoming food-pellet reinforcement

Previous research has demonstrated that rats' rates of lever pressing for low-concentration liquid-sucrose reinforcers are increased when food-pellet, rather than sucrose, reinforcement will be upcoming in the same session (i.e. induction). The present experiments were designed to determine whether this induction was the product of 'anticipatory responses' for the upcoming food pellets being added to the responses being made for the currently available sucrose reinforcement. Experiment 1 tested this idea by summing sucrose-reinforced responding and 'anticipatory responding' from different conditions and comparing the sum to responding from a third condition in which subjects responded for sucrose when food-pellet reinforcement was upcoming. The comparison yielded similar response rates. Experiment 2 employed a blackout, of different durations in different conditions, to delay the upcoming food-pellet reinforcement. Consistent with the anticipatory-responding account, the delay decreased the size of the induction. However, results from the blackouts were not entirely consistent with the anticipatory-responding explanation. Experiment 3 provided, in some conditions, sucrose and food-pellet reinforcement in the first and second halves of the session, respectively, for responding on separate levers. These conditions separated 'anticipatory responses' for the food pellets from responses for the sucrose reinforcers. However, induction in responding for sucrose was still present. Together, these experiments demonstrate that, although anticipatory responses may contribute to induction in some instances, they are not solely responsible for the effect.

Criticisms of the satiety hypothesis as an explanation for within-session decreases in responding

The authors of four papers recently reported that satiation provides a better explanation than habituation for within-session decreases in conditioned responding. Several arguments question this conclusion. First, the contribution of habituation to within-session changes in responding seems clearly established. Information that is consistent with habituation, but that is difficult to reconcile with satiation, is not adequately addressed. Second, the limited evidence offered in support of satiation is ambiguous because the results are just as compatible with habituation as with other satiety variables. Finally, the term satiation is used in an intuitive way that is sometimes contradicted by research about the termination of ingestion. Use of the technical term satiation in a way that differs from its conventional usage will only isolate operant psychology from other areas of psychological research.