Tactical contingencies in the experimental analysis of reinforcement and operant classes

In his “Tactics of Scientific Research” (1960), his work on avoidance, his discovery of equivalence classes and his cautions on applications of coercion, Murray Sidman created high standards for behavior analytic research. I illustrate his influence in the context of three examples he might have characterized as pilot studies. Each examined trial N+1 response probabilities depending on whether trial N responding had produced a reinforcer. Differentially reinforced interresponse times, keys pecked in arbitrary matching, and two-key response sequences provided no robust evidence that reinforcing some response property on trial N raises the probability of responding with that property on trial N+1. These negative findings shed light on the nature of operant classes and on the relation of reinforcers to the responses that produced them. Through selection, reinforcers create operant classes and engender variations of the responses within those classes; operant classes are held together by common contingencies. Sidman extended our understanding of operant classes by expanding them to include equivalence relations.     

Examining the discriminative and strengthening effects of reinforcers in concurrent schedules

Reinforcers may increase operant responding via a response-strengthening mechanism whereby the probability of the preceding response increases, or via some discriminative process whereby the response more likely to provide subsequent reinforcement becomes, itself, more likely. We tested these two accounts. Six pigeons responded for food reinforcers in a two-alternative switching-key concurrent schedule. Within a session, equal numbers of reinforcers were arranged for responses to each alternative. Those reinforcers strictly alternated between the two alternatives in half the conditions, and were randomly allocated to the alternatives in half the conditions. We also varied, across conditions, the alternative that became available immediately after a reinforcer. Preference after a single reinforcer always favored the immediately available alternative, regardless of the local probability of a reinforcer on that alternative (0 or 1 in the strictly alternating conditions, .5 in the random conditions). Choice then reflected the local reinforcer probabilities, suggesting some discriminative properties of reinforcement. At a more extended level, successive same-alternative reinforcers from an alternative systematically shifted preference towards that alternative, regardless of which alternative was available immediately after a reinforcer. There was no similar shift when successive reinforcers came from alternating sources. These more temporally extended results may suggest a strengthening function of reinforcement, or an enhanced ability to respond appropriately to "win-stay" contingencies over "win-shift" contingencies.     

Operant modulation of low-level attributes of rule-governed behavior by nonverbal contingencies

A low-level and nonsalient attribute of behavior (i.e., speed of pressing) was subjected to differential nonverbal operant reinforcement when rules governed a high-level attribute of that behavior (i.e., counting by means of key presses). Unknown to the subjects, reinforcers depended on reduced (slow group) or increased (fast group) speed of pressing rather than on the correct number of presses. The reinforced attribute was modulated according to the arranged speed contingencies independently of the instructed task and independently of subjects' awareness of the critical contingency. A control group receiving random reinforcers demonstrated no systematic speed changes. Possible mechanisms related to behavior changes of this type were examined and discussed, and it was concluded that the behavior changes observed in this situation could be attributed to operant conditioning. The results substantiate the assumption that nonverbal operant contingencies may modulate low-level and nonsalient attributes of rule-governed behavior.     

Contiguity and contingency in the acquisition and maintenance of an operant

Three experiments compared the effects of nondifferential and differential reinforcement of response location on a circular dimension. Rats were required to operate a vertical joystick to produce food. When food was delivered immediately after responses, but independent of response location, the spatial concentration of responding was low and no progressive changes were observed. Traditional and percentile schedules of differential reinforcement for response location produced highly reliable acquisition of spatially concentrated responding. Once concentrated responding had been established, nondifferential reinforcement was sufficient to maintain it in some subjects. Since only the differential reinforcement schedules established a contingency with respect to response location, it was concluded that this relationship was necessary for acquisition, but that response-reinforcer contiguity may be sufficient for maintenance. This conclusion is consistent with the view that operant conditioning is a contiguity-based process, but that contingencies are required to produce reliable contiguity between reinforcers and particular responses.     

Response duration is sensitive to both immediate and delayed reinforcement

We investigated the duration of lever pressing by rats when the delivery of appetitive reinforcers was contingent upon response duration. In the first experiment, response durations increased when duration requirements were imposed, and they decreased when duration requirements were removed. This effect occurred whether reinforcers were immediate or delayed by 8 s. In order to maintain the integrity of the delay intervals, reinforcer delivery was dependent upon both lever depression and release. In a second experiment, lever depression only and a response duration of at least 4 s were required for reinforcer delivery. Compared to immediate reinforcement conditions, delayed reinforcers increased both variability and the length of the maximum response durations. In a third experiment, immediate reinforcers were delivered contingent upon lever depression and release under a variety of duration requirements. Median lever‐press durations tracked the contingencies rapidly. Across all three experiments, rats emitted numerous response durations that were too short to satisfy the reinforcer requirements, and bimodal distributions similar to those produced by differential reinforcement of low rate schedules were evident for most rats. In many aspects, response duration responds to reinforcement parameters in a fashion similar to rate of discrete responding, but an examination of this continuous dimension of behavior may provide additional information about environment–behavior relationships.     

Temporal regulation of children with autism spectrum disorder exposed to a differential-reinforcement-of low-rates schedule

This study investigated temporal adjustment of children with autism spectrum disorder under a differential-reinforcement-of-low-rates (DRL) schedule. Sixteen participants, aged 3.2 to 7 years, were exposed to two conditions, DRL 5 s and DRL 20 s. Children participated in 7 sessions in each condition, except for 1 participant who attained the adjustment criteria in the DRL 5-s schedule. Temporal adjustment was measured with the proportion of reinforced interresponse times (IRTs) and the mean IRT. The operant response was a press on a touch screen and the reinforcers were cartoons. IQ and receptive language were measured prior to the DRL sessions. Results showed that the mean proportion of reinforced IRTs was slightly higher in the DRL 5-s schedule. The mean IRT was above the IRT requirement in both conditions. However, substantial individual variability was observed. Children with higher IQ and receptive language scores presented a greater proportion of reinforced IRTs in both conditions. Moreover, participants who adjusted their responses to the DRL 5-s schedule were more likely to adjust responding to the DRL 20-s schedule. This suggests that some children might be more sensitive to reinforcement contingencies than others. This study points at future research in the field of timing in children.     

Operant variability: evidence,functions, and theory

Although responses are sometimes easy to predict, at other times responding seems highly variable, unpredictable, or even random. The inability to predict is generally attributed to ignorance of controlling variables, but this article is a review of research showing that the highest levels of behavioral variability may result from identifiable reinforcers contingent on such variability. That is, variability is an operant. Discriminative stimuli and reinforcers control it, resulting in low or high variability, depending on the contingencies. Schedule-of-reinforcement effects are orderly, and choosing to vary or repeat is lawfully governed by relative reinforcement frequencies. The operant nature of variability has important implications. For example, learning, exploring, creating, and problem solving may partly depend on it. Abnormal levels of variability, including those found in psychopathologies such as autism, depression, and attention deficit hyperactivity disorder, may be modified through reinforcement. Operant variability may also help to explain some of the unique attributes of voluntary action.     

The momentum of human behavior in a natural setting

Adults with mental retardation in a group home received popcorn or coffee reinforcers for sorting plastic dinnerware. In Part 1 of the experiment, reinforcers were dispensed according to a variable-interval 60-s schedule for sorting dinnerware of one color and according to a variable-interval 240-s schedule for sorting dinnerware of a different color in successive components of a multiple schedule. Sorting rates were similar in baseline, but when a video program was shown concurrently, sorting of dinnerware was more resistant to distraction when correlated with a higher rate of reinforcement. In Part 2 of the experiment, popcorn or coffee reinforcers were contingent upon sorting both colors of dinnerware according to variable-interval 60-s schedules, but additional reinforcers were given independently of sorting according to a variable-time 30-s schedule during one dinnerware-color component. Baseline sorting rate was lower but resistance to distraction by the video program was greater in the component with additional variable-time reinforcers. These results demonstrate that resistance to distraction depends on the rate of reinforcers obtained in the presence of component stimuli but is independent of baseline response rates and response–reinforcer contingencies. Moreover, these results are similar to those obtained in laboratory studies with pigeons, demonstrating that the determination of resistance to change by stimulus–reinforcer relations is not confined to controlled laboratory settings or unique to the pigeon.     

ANALYSIS OF FREE-TIME CONTINGENCIES AS POSITIVE VERSUS NEGATIVE REINFORCEMENT

Providing a short break contingent on completed work may increase responding through positive reinforcement (e.g., access to preferred activities) or negative reinforcement (e.g., escape from work). In this investigation, three analyses conducted with a boy with profound mental retardation showed that (a) a 20-s break increased responding more than a positive reinforcer (cola) did, and (b) the reinforcing effects of a 20-s break were affected by the availability of positive reinforcers during the break.     

Reinforcement contingencies and signal detection.

Pigeons were trained to discriminate temporal stimuli in a discrete-trial signal-detection procedure. Pecks to one side key were reinforced intermittently after exposure to one duration, and pecks to the other side key were reinforced intermittently after exposure to a different duration. In Experiment I, the allocation of reinforcers was varied systematically for correct responses and for errors, using a procedure that controlled the obtained numbers of reinforcers. When reinforcers were allocated symmetrically, the level of discrimination decreased as the proportion of reinforcers for errors increased. When reinforcers were allocated asymmetrically, the decrease in discrimination was less systematic. Bias toward one or the other side key roughly matched the ratio of reinforcers obtained by pecks at those keys, independent of the level of discrimination. In Experiment II, the overall rate of reinforcement for correct responses was varied both within and between experimental conditions. The level of discrimination was positively related to the overall rate of reinforcement. The discrimination data of both experiments were interpreted in relation to the contingencies of reinforcement and nonreinforcement, characterized by the average difference in reinforcement probability for correct responses and errors.     

ON THE RELATIVE REINFORCING EFFECTS OF CHOICE AND DIFFERENTIAL CONSEQUENCES

Research on the reinforcing effects of providing choice-making opportunities to individuals with developmental disabilities (i.e., allowing them to choose reinforcers or tasks) has produced inconsistent results, perhaps because the mechanisms underlying such effects remain unclear. Choice may produce a reinforcement effect because it is correlated with differential consequences (i.e., choice may increase one's access to higher preference stimuli), or it may have reinforcement value independent of (or in addition to) the chosen stimulus. In Experiment 1, we used a concurrent-operants arrangement to assess preference for a choice condition (in which participants selected one of two available reinforcers) relative to a no-choice condition (in which the therapist selected the same reinforcers on a yoked schedule). All 3 participants preferred the choice option. In Experiment 2, we altered the schedules so that the participant selected one of two lower preference reinforcers in the choice condition, whereas the therapist selected a higher preference stimulus for the participant either half or all of the time in the no-choice condition. Participants typically allowed the therapist to select reinforcers for them (i.e., they allocated responding to the no-choice condition) when it resulted in greater access to higher preference stimuli.     

Response Stereotypy in Humans Maintained by Response-Contingent Events

The present study examined stereotyped behaviors developed during human performances that were generated by response-dependent intermittent schedules of reinforcement. Thirty university students were assigned to either fixed-interval 30-s or fixed-ratio 30-s schedules in which points or monetary reinforcers were produced only by presses on the number keys of a 41-key computer keyboard. Behavior patterns developed by all subjects were classified into four categories: optimal, random, unique, and general stereotypes. The general stereotypes category was further subdivided into five idiosyncratic types: connection, order, shift, repeat, and restriction. Analysis of the data demonstrated the role of contiguity: Whatever behavior happened to precede reinforcers was repeated even though reinforcers did not depend on that behavior. These findings support the argument that much of idiosyncratic and stereotyped human behavior is produced and maintained by contingencies of reinforcement, rather than schedule-induced or adjunctive behavior.     

Defining reinforcess — A problem in communication for consultation in behavior modification

This paper reviews the respondent (Hull-Spence) and operant (Skinnerian) conditioning definitions of reinforcers and reinforcement and demonstrates the need to keep the systems separate when consulting about behavior modification. The two systems are shown to lead to different modification procedures.One important distinction between the systems is whether a reinforcer is simply associated with a response (respondent) or whether it must follow the response (operant). A second important distinction is the definition of negative reinforcement. In respondent conditioning, negative reinforcement entails presenting an aversive stimulus in association with the response and results in a decrease in response rate. In operant conditioning, negative reinforcement entails the removal of an aversive stimulus following a correct response, which results in an increase in response rate.     

FUNCTIONAL ANALYSIS OF INAPPROPRIATE SOCIAL INTERACTIONS IN STUDENTS WITH ASPERGER'S SYNDROME

We analyzed the inappropriate social interactions of 3 students with Asperger's syndrome whose behavior was maintained by social positive reinforcement. We tested whether inappropriate social behavior was sensitive to social positive reinforcement contingencies and whether such contingencies could be reversed to increase the probability of socially appropriate responding. Our results show that social positive reinforcers can be identified for inappropriate social interactions and that appropriate social behaviors can be sensitive to reinforcement contingency reversals.     

Treatment of food selectivity: An evaluation of video modeling of contingencies

Many children with disabilities have feeding problems including, but not limited to, food selectivity and/or food refusal. The purpose of this study was to evaluate the effectiveness of video modeling of contingencies alone and combined with direct exposure to the contingencies in the treatment of food selectivity. Treatment procedures included sequentially introducing videos in which models consumed nonpreferred foods or were exposed to differential reinforcement or differential reinforcement plus escape extinction. In addition, during feeding sessions, participants were exposed to differential reinforcement. Results indicated that video modeling of differential reinforcement plus direct exposure to differential reinforcement may be effective at increasing consumption of some nonpreferred foods, but the results were not replicated across all foods. For one participant, consumption of one food increased with video modeling alone.     

Group versus individual reinforcement contingencies within the context of group study conditions

We investigated the effects of two teaching variables on students' Spanish vocabulary quiz performance: (a) group study and (b) individual versus group contingencies. In Experiment 1, we compared students' quiz scores under conditions in which students either studied independently and received no programmed reinforcement or studied in groups and received individual rewards for high scores. The results showed that, on average, the group-study individual-reward condition produced superior quiz scores. In Experiment 2, we compared individual (i.e., the superior condition in Experiment 1) and group contingencies within the context of the group study condition. On average across the class, group contingencies produced performance superior to individual contingencies. In both studies, however, benefits for the classes as a whole were mitigated by effects on individual students. These results extend the literature on the effects of group-based instructional activities and reinforcement contingencies. Educators who choose such procedures may encounter conflicting findings depending on whether they examine results at the group or individual level.     

Differences in the effect of Pavlovian contingencies upon behavioral momentum using auditory versus visual stimuli.

We examined the role of Pavlovian and operant relations in behavioral momentum by arranging response-contingent alternative reinforcement in one component of a three-component multiple concurrent schedule with rats. This permitted the simultaneous arranging of different response-reinforcer (operant) and stimulus-reinforcer (Pavlovian) contingencies during three baseline conditions. Auditory or visual stimuli were used as discriminative stimuli within the multiple concurrent schedules. Resistance to change of a target response was assessed during a single session of extinction following each baseline condition. The rate of the target response during baseline varied inversely with the rate of response-contingent reinforcement derived from a concurrent source, regardless of whether the discriminative stimuli were auditory or visual. Resistance to change of the target response, however, did depend on the discriminative-stimulus modality. Resistance to change in the presence of visual stimuli was a positive function of the Pavlovian contingencies, whereas resistance to change was unrelated to either the operant or Pavlovian contingencies when the discriminative stimuli were auditory. Stimulus salience may be a factor in determining the differences in resistance to change across sensory modalities.     

Continuous versus discrete dimensions of reinforcement schedules: An integrative analysis

An approach to reinforcement-schedule contingencies is presented that accommodates continuous as well as discrete effective dimensions of responses and reinforcers. College students' wheel turning was reinforced by projected reading material according to four schedule contingencies that incorporated either a discontinuous (count) or continuous (duration) dimension of the response and the reinforcer. The contingencies arranged a 1:1 correspondence between (a) response count and consequent stimulus count, (b) response duration and stimulus count, (c) response count and stimulus duration, and (d) response duration and stimulus duration. Contingencies incorporating response count produced moderate to high rates of very short-duration responses. Contingencies incorporating response duration produced very low-rate, long-duration responding. The dimension of the reinforcer had minimal or no additional effect. We suggest that incorporating duration and other continuous dimensions into schedule contingencies may improve our understanding of both laboratory and nonlaboratory behavior.     

Determinants of reinforcer accumulation during an operant task.

Responses by rats on an earn lever made available food pellets that were delivered to a food cup by responses on a second, collect, lever. The rats could either collect and immediately consume or accumulate (defined as the percentage of multiple earn responses and as the number of pellets earned before a collect response) earned pellets. In Experiment 1, accumulation varied as a function of variations in the earn or collect response requirements and whether the earn and collect levers were proximal (31 cm) or distal (248 cm) to one another. Some accumulation occurred under all but one of the conditions, but generally was higher when the earn and collect levers were distal to one another, particularly when the earn response requirement was fixed-ratio (FR) 1. In Experiment 2, the contributions of responses and time to accumulation were assessed by comparing an FR 20 earn response requirement to a condition in which only a single earn response was required at the end of a time interval nominally yoked to the FR interval. When 248 cm separated the earn and collect levers, accumulation was always greater in the FR condition, and it was not systematically related to reinforcement rate. In Experiment 3, increasing the earn response requirement with a progressive-ratio schedule that reset only with a collect response increased the likelihood of accumulation when the collect and earn levers were 248 cm apart, even though such accumulation increased the next earn response requirement. Reinforcer accumulation is an understudied dimension of operant behavior that relates to the analysis of such phenomena as hoarding and self-control, in that they too involve accumulating versus immediately collecting or consuming reinforcers.     

Resistance To Change As A Function Of Stimulus-reinforcer And Location-reinforcer Contingencies

Pigeons responded on two keys in each component of a multiple concurrent schedule. In one series of conditions the distribution of reinforcers between keys within one component was varied so as to produce changes in ratios of reinforcer totals for key locations when summed across components. In a second series, reinforcer allocation between components was varied so as to produce changes in ratios of reinforcer totals for components, summed across key locations. In each condition, resistance to change was assessed by presenting response-independent reinforcers during intercomponent blackouts and (for the first series) by extinction of responding on both keys in both components. Resistance to change for response totals within a component was always greater for the component with the larger total reinforcer rate. However, resistance to change for response totals at a key location was not a positive function of total reinforcement for pecking that key; indeed, relative resistance to extinction for the two locations showed a weak negative relation to ratios of reinforcer totals for key location. These results confirm the determination of resistance to change by stimulus—reinforcer contingencies.