Marking effects in instrumental performance on DRH schedules

Three experiments investigated the effect of presenting a brief stimulus after a response sequence on the rate of lever-pressing by rats on differential reinforcement of high rate (DRH) schedules. In Experiment 1 enhanced responding was produced by a visual stimulus presented during a 500-msec delay of reinforcement compared to a condition in which no stimulus was presented. In Experiment 2 rats responded on a multiple DRH DRH schedule in which the DRH contingency was reinforced on a 50% schedule in each component. Equivalent levels of responding occurred in the components when reinforcement was signalled in one component and when the signal was presented following the non-reinforced schedules in the other components. A further group of rats received the stimulus presented after non-reinforced schedules in one component but not at all in the other component; responding was enhanced in the former component relative to the latter component. In Experiment 3 brief stimuli presented after the completion of DRH components on a second-order VR (DRH) schedule elevated response rates irrespective of whether the signal was presented paired or unpaired with reinforcement. The present data support the view that a brief signal may serve to mark a response sequence in memory and facilitate instrumental performance.     

Conditioned suppression of drl responding: Effect of ucs intensity, schedule parameter, and schedule context

In Experiment I, groups of rats were trained to press a lever for food reinforcement on differential reinforcement of low rate (DRL) schedules which differed in parameter value. A stimulus which terminated with either a 0.5-mA or 2.0-mA electric shock was then superimposed upon each DRL baseline. In general, the magnitude of conditioned suppression was an inverse function of DRL schedule parameter and a direct function of shock intensity. Experiment II demonstrated that the rate of responding maintained by the DRL component of a multiple DRL-extinction schedule decreased during a stimulus preceding a 0.5-mA shock, whereas the rate of responding maintained by the DRL component of a multiple DRL-variable interval schedule showed little change or increased slightly during a stimulus preceding a 0.5-mA shock.     

Conditioned suppression or facilitation as a function of the behavioral baseline

Rats were exposed to a multiple schedule of reinforcement. During one component, a bar-press was followed by reinforcement only if it occurred between 15 and 20 sec after the previous response. This differential-reinforcement-of-low-rate (DRL) schedule produced a typical slow rate of responding. During the other component, reinforcement followed the first response to be emitted during limited periods of time which occurred at fixed intervals. These fixed-interval schedules with a limited hold produced higher response rates, described as `interval' or `ratio-like' behavior. Responding during the DRL component increased in frequency during a tone which ended with an unavoidable shock of low intensity, but decreased during the tone when the shock intensity was raised. The `interval' and `ratio-like' responding decreased in frequency during the tone at all shock intensities. Initial acceleration of the DRL responding appeared to be due to adventitious punishment of collateral behavior which was observed between the bar-presses. The more severe conditioned suppression during the fixed-interval components might be the result of the lower probability of reinforcement after any single response.     

Choice between response units: The rate constancy model

In a conjoint schedule, reinforcement is available simultaneously on two or more schedules for the same response. The present experiments provided food for key pecking on both a random-interval and a differential-reinforcement-of-low-rate (DRL) schedule. Experiment 1 involved ordinary DRL schedules; Experiment 2 added an external stimulus to indicate when the required interresponse time had elapsed. In both experiments, the potential reinforcer frequency from each component was varied by means of a second-order fixed-ratio schedule, and the DRL time parameter was changed as well. Response rates were described by a model stating that time allocation to each component matches the relative frequency of reinforcement for that component. When spending time in a given component, the subject is assumed to respond at the rate characteristic of baseline performance. This model appeared preferable to the absolute-rate version of the matching law. The model was shown to be applicable to multiple-response concurrent schedules as well as to conjoint schedules, and it described some of the necessary conditions for response matching, undermatching, and bias. In addition, the pigeons did not optimize reinforcer frequency.     

Using differential reinforcement of low rates to reduce children's requests for teacher attention

We evaluated the effectiveness of full-session differential reinforcement of low rates of behavior (DRL) on 3 primary school children's rates of requesting attention from their teacher. Using baseline rates of responding and teacher recommendations, we set a DRL schedule that was substantially lower than baseline yet still allowed the children access to teacher assistance. The DRL schedule was effective in reducing children's requests for assistance and approval, and the teacher found the intervention highly useful and acceptable. The possible mechanisms that account for behavior change using full-session DRL schedules are discussed.     

Punishment contras during free-operant avoidance

Punishment of bar-pressing responses of rhesus monkeys with electric shock in one component of a multiple free-operant avoidance schedule suppressed responding in that component. These decreases were concomitant with response rate increases in the unpunished component (punishment contrast). Response rates in both components increased when punishment was removed and decreased in successive sessions. These effects of punishment on unpunished responding were similar to those obtained during single and multiple schedules of positive reinforcement and they suggest a further similarity in the development of discriminations during positive and negative reinforcement schedules.     

Control rate of response or reinforcement and amphetamine's effect on behavior.

The roles of control response rate and reinforcement frequency in producing amphetamine's effect on operant behavior were evaluated independently in rats. Two multiple schedules were arranged in which one variable, either response rate or reinforcement frequency, was held constant and the other variable manipulated. A multiple differential-reinforcement-of-low-rate seven-second yoked variable-interval schedule was used to equate reinforcement frequencies at different control response rates between multiple-schedule components. Amphetamine increased responding under the variable-interval component. In contrast, amphetamine decreased responding equivalently between components of a multiple random-ratio schedule that produced similar control response rates at different reinforcement frequencies. The results provide experimental support to the rate-dependency principle that control rate of responding is an important determinant of amphetamine's effect on operant behavior.     

DIFFERENTIALLY REINFORCING LOW RATES OF MISBEHAVIOR WITH NORMAL ELEMENTARY SCHOOL CHILDREN1

Effective nonpunitive procedures for reducing counterproductive classroom behaviors are of potential benefit to both students and teachers. A recent strategy for dealing with this class of problem behaviors involves the reinforcement of acceptably low levels of such behavior. The laboratory version of this procedure, called differential reinforcement of low rates of responding (or DRL), provides for a reinforcer to be delivered contingent upon a response that is separated from the last preceding response by a minimum amount of time. To make this procedure more amenable to classroom use, the present authors have modified it so that a reinforcer is delivered if fewer than a specified number of responses occur within a preset time interval (Deitz and Repp, Journal of Applied Behavior Analysis, 1973, 6 , 457–463). Previous studies using this procedure have found it effective in reducing and maintaining low rates of targeted behaviors. However, these effects have been demonstrated with groups of subjects and/or individuals from dependent populations. The present study investigated use of this modified DRL procedure with individual students in normal elementary classrooms. In the first of three studies, “talk-outs” of an 11-yr-old fifth-grade male were reduced when nonexchangeable gold stars were made contingent on two or fewer responses per session. During baseline sessions, an average of 4.45 talkouts were observed per 45-min session. Average responding subsequently fell to 1.83 when the modified DRL contingency was applied, increased to 7.60 during a reversal phase, and dropped again to an average of 1.20 when the contingency was reapplied. In the second study, out-of-seat behavior of a 12-yr-old sixth-grade female was reduced when gold stars were made contingent on two or fewer responses per 45-min class period. Baseline responding averaged 6.10 responses per session. When the contingency was applied, average responding fell to 0.16. During the reversal period, responding increased to an average of 6.00 and fell again, after the contingency was re-introduced to an average of 0.40. In the third study, a reduction in both talking-out and out-of-seat behaviors of another 11-yr-old fifth-grade male was demonstrated with a multiple-baseline design. Using different lengths of baselines, gold stars were made contingent first on a low rate of out-of-seat behavior, and then on a low rate of talk-outs. Out-of-seat responding fell from a baseline average of 7.50 to a treatment average of 1.14. Talk-outs went from a baseline average of 4.66 to a treatment average of 1.14. In all three studies, the modified DRL procedure proved effective with the children and was manageable by the classroom teacher. For the students, nonexchangeable conditioned reinforcers (stars) were sufficient to maintain lowered rates of inappropriate behavior with the modified DRL schedule; there was no need for an elaborate token economy, a process that in many cases may be only a form of behavioral “overkill”. As in other studies investigating DRL schedules, students were not informed of their accumulation of responses; the differential effects of providing or withholding this feedback need to be investigated. Overall, these studies add single-subject replication with normal children to the literature on modified DRL procedures.     

The effect of punishment shock intensity upon responding under multiple schedules

In the first of two experiments, responses of two pigeons were maintained by multiple variable-interval, variable-ratio schedules of food reinforcement. Concurrent punishment was introduced, which consisted of a brief electric shock after each tenth response. The initial punishment intensities had no lasting effect upon responding. Then, as shock intensity increased, variable-ratio response rates were suppressed more quickly than variable-interval response rates. When shock intensity decreased, variable-interval responding recovered more quickly, but the rates under both schedules eventually returned to their pre-punishment levels. In the second experiment, the following conditions were studied in three additional pigeons: (1) With each shock intensity in effect for a number of sessions, punishment shock intensity was gradually increased and decreased and responding was maintained by multiple variable-ratio, fixed-ratio schedules of food reinforcement; (2) Changes in punishment shock intensity as described above with responding maintained by either a variable-ratio or a fixed-ratio schedule, which were presented on alternate days; (3) Session-to-session changes in shock intensity with responding maintained by multiple variable-ratio, fixed-ratio schedules. Responding under the two schedules was suppressed to approximately the same extent by a particular shock intensity. Also, post-reinforcement pauses under the fixed-ratio schedule increased as response suppression increased.     

Contrast, component duration, and the following schedule of reinforcement

Experiment 1 investigated component duration in a four-component multiple schedule designed to separate the effects of the preceding schedule of reinforcement from those of the following schedule of reinforcement. The preceding schedule in the preceding component had no consistent effect regardless of component duration. The following schedule was a powerful determinant of behavior, however, with higher response rates resulting from a following period of extinction. Moreover, the effect of the following schedule was greater with short component durations, which strongly suggests that component-duration effects previously found with multiple schedules are due generally to variation in the degree of control by the following schedule. Experiments 2--4 investigated the basis of the effects of the following schedule. In some situations differential responding in the following component was the controlling variable, but in others it was differential reinforcement in the following component. The results are consistent with the view that response rate during a stimulus is inversely related to the "value" of the following component, where the calculation of value must include both primary and conditioned reinforcement.     

Concurrent fixed-interval variable-ratio schedules and the matching relation

Five rats responded under concurrent fixed-interval variable-ratio schedules of food reinforcement. Fixed-interval values ranged from 50-seconds to 300-seconds and variable-ratio values ranged from 30 to 360; a five-second changeover delay was in effect throughout the experiment. The relations between reinforcement ratios obtained from the two schedules and the ratios of responses and time spent on the schedules were described by Baum's (1974) generalized matching equation. All subjects undermatched both response and time ratios to reinforcement ratios, and all subjects displayed systematic bias in favor of the variable-ratio schedules. Response ratios undermatched reinforcement ratios less than did time ratios, but response ratios produced greater bias than did time ratios for every subject and for the group as a whole. Local rates of responding were generally higher on the variable-ratio than on the fixed-interval schedules. When responding was maintained by both schedules, a period of no responding on either schedule immediately after fixed-interval reinforcement typically was followed by high-rate responding on the variable-ratio schedule. At short fixed-interval values, when a changeover to the fixed-interval schedule was made, responding usually continued until fixed-interval reinforcement was obtained; at longer values, a changeover back to the variable-ratio schedule usually occurred when fixed-interval reinforcement was not forthcoming within a few seconds, and responding then alternated between the two schedules every few seconds until fixed-interval reinforcement finally was obtained.     

Multiple determinants of the effects of reinforcement magnitude on free-operant response rates

Four experiments examined the effects of increasing the number of food pellets given to hungry rats for a lever-press response. On a simple variable-interval 60-s schedule, increased number of pellets depressed response rates (Experiment 1). In Experiment 2, the decrease in response rate as a function of increased reinforcement magnitude was demonstrated on a variable-interval 30-s schedule, but enhanced rates of response were obtained with the same increase in reinforcement magnitude on a variable-ratio 30 schedule. In Experiment 3, higher rates of responding were maintained by the component of a concurrent variable-interval 60-s variable-interval 60-s schedule associated with a higher reinforcement magnitude. In Experiment 4, higher rates of response were produced in the component of a multiple variable-interval 60-s variable-interval 60-s schedule associated with the higher reinforcement magnitude. It is suggested that on simple schedules greater reinforcer magnitudes shape the reinforced pattern of responding more effectively than do smaller reinforcement magnitudes. This effect is, however, overridden by another process, such a contrast, when two magnitudes are presented within a single session on two-component schedules.     

Septal lesions lower responding under fixed-ratio schedules of reinforcement.

Albino Sprague-Dawley rats with complete septal lesions and rats with control operations were studied under fixed-ratio (FR) schedules of reinforcement. Both groups were trained for 10 sessions each under FR 10, 20, 40, 60, 80, and 100. In contrast to findings from progressive FR studies and some simple FR studies, septal lesions resulted in lower overall and local response rates along with longer postreinforcement pauses. These effects were especially evident during the FR 100 schedule of reinforcement. A comparison of reinforcement rate as a function of FR size within the context of behavioral economics (i.e., a demand function) indicated that septal lesions did not alter the reward value of food. These findings suggest that responding on FR schedules of reinforcement can be altered by the various procedures used to train rats to reach the terminal value of a reinforcement schedule.     

Multiple reinforcement contingencies to reduce aggression,self-injury and dysfunctional verbal behaviors in an adult who is sensory impaired

Differential reinforcement of other behavior (DRO) and differential reinforcement of low rates of responding (DRL) have been effective techniques in reducing maladaptive behaviors in therapeutic settings. Reported studies of these reinforcement-based procedures indicate that they are usually implemented in isolation, targeting only a single behavior or class of behaviors. In this study, multiple DRO and DRL contingencies were utilized concurrently in reducing two distinct classes of behaviors with a 26 year-old blind man with moderate retardation. One class of behaviors included socially inappropriate verbalizations, while the other included aggressive, self-injurious and environmentally destructive behaviors. Distinct contingencies were established according to the functions of the targeted behaviors and their severity and separate schedules of reinforcement were derived from baseline frequencies. Over a period of 20 months, the differential reinforcement interventions resulted in rapid reduction of behaviors in both classes to near-zero rates and frequencies were maintained at this low level while contingency schedules were systematically lengthened. Collateral effects are discussed including performance in functional academics and participation in community integration activities.     

Matching and maximizing with concurrent ratio-interval schedules.

Animals exposed to standard concurrent variable-ratio variable-interval schedules could maximize overall reinforcement rate if, in responding, they showed a strong response bias toward the variable-ratio schedule. Tests with the standard schedules have failed to find such a bias and have been widely cited as evidence against maximization as an explanation of animal choice behavior. However, those experiments were confounded in that the value of leisure (behavior other than the instrumental response) partially offsets the value of reinforcement. The present experiment provides another such test using a concurrent procedure in which the confounding effects of leisure were mostly eliminated while the critical aspects of the concurrent variable-ratio variable-interval contingency were maintained: Responding in one component advanced only its ratio schedule while responding in the other component advanced both ratio schedules. The bias toward the latter component predicted by maximization theory was found.     

Differential effects of pentobarbital and cocaine on punished and nonpunished responding.

Similar rates of punished and nonpunished responding, maintained with equated rates of reinforcement, were established in pairs of rats. One subject of each pair was exposed to a random-ratio schedule of food presentation. The interreinforcement intervals for this subject comprised the intervals of a random-interval schedule of reinforcement for the other (yoked) rat. The random-ratio schedule maintained rates of responding higher than those maintained by the same rate of reinforcement schedule according to the yoked random-interval contingency. A random-ratio schedule of electric foot shock added to the random-ratio schedule of food presentation suppressed rates of responding such that similar rates of responding were observed in rats of both groups. Pentobarbital (3.0 to 17.0 mg/kg) increased punished responding at doses that had little effect on or decreased nonpunished responding, whereas cocaine (5.6 to 30 mg/kg) increased nonpunished responding at doses that decreased or did not alter punished responding. Qualitatively different effects of pharmacological agents on punished and nonpunished responding can be obtained using procedures that generate similar rates and temporal patterns of punished and nonpunished responding. The effects of pentobarbital and cocaine on responding can be determined by factors other than simply the baseline rate of responding.     

Pavlovian contingencies and resistance to change in a multiple schedule

According to theoretical accounts of behavioral momentum, the Pavlovian stimulus—reinforcer contingency determines resistance to change. To assess this prediction, 8 pigeons were exposed to an unsignaled delay-of-reinforcement schedule (a tandem variable-interval fixed-time schedule), a signaled delay-of-reinforcement schedule (a chain variable-interval fixed-time schedule), and an immediate, zero-delay schedule of reinforcement in a three-component multiple schedule. The unsignaled delay and signaled delay schedules employed equal fixed-time delays, with the only difference being a stimulus change in the signaled delay schedule. Overall rates of reinforcement were equated for the three schedules. The Pavlovian contingency was identical for the unsignaled and immediate schedules, and response—reinforcer contiguity was degraded for the unsignaled schedule. Results from two disruption procedures (prefeeding subjects prior to experimental sessions and adding a variable-time schedule to timeout periods separating baseline components) demonstrated that response—reinforcer contiguity does play a role in determining resistance to change. The results from the extinction manipulation were not as clear. Responding in the unsignaled delay component was consistently less resistant to change than was responding in both the immediate and presignaled segments of the signaled delay components, contrary to the view that Pavlovian contingencies determine resistance to change. Probe tests further supported the resistance-to-change results, indicating consistency between resistance to change and preference, both of which are putative measures of response strength.     

Behavioral parameters of drug action: signalled and response-independent reinforcement

Four pigeons were initially trained under a multiple variable-interval 1-min variable-interval 1-min schedule of food reinforcement. For two of the pigeons, a signal was then presented whenever the reinforcer was available in one component; this resulted in positive contrast. For the other two pigeons, the reinforcer was presented independently of responding on a variable-time schedule in one component; this resulted in negative induction. After 30 to 50 sessions, however, a similar degree of differential responding occurred under both multiple schedules, i.e., high rates in the variable-interval component and low rates in the other component. Reinforcement frequency remained about the same in each of the schedule components. The stable performances then served as baselines for studying drug effects. In the high-rate component of both multiple schedules, small doses of d-amphetamine increased responding, whereas larger doses decreased responding. In the low-rate component of both multiple schedules, there was no rate-increasing effect at any dose of d-amphetamine; such an effect was found, however, with phenobarbital at a dose that decreased responding in the high-rate component. The drug effects thus depended on the interaction of pharmacologic variables (specific drug and dose) with behavioral variables (schedule components).     

Competitive fixed-interval performance in humans

Two persons responded in the same session in separate cubicles, but under a single schedule of reinforcement. Each time reinforcement was programmed, only the first response to occur, that is, the response of only one of the subjects, was reinforced. “Competitive” behavior that developed under these conditions was examined in three experiments. In Experiment 1 subjects responded under fixed-interval (FI) 30-s, 60-s, and 90-s schedules of reinforcement. Under the competition condition, relative to baseline conditions, the response rates were higher and the pattern was “break-and-run.” In Experiment 2, subjects were exposed first to a conventional FI schedule and then to an FI competition schedule. Next, they were trained to respond under either a differential-reinforcement-of-low-rate (DRL) or fixed-ratio (FR) schedule, and finally, the initial FI competition condition was reinstated. In this second exposure to the FI competition procedure, DRL subjects responded at lower rates than were emitted during the initial exposure to that condition and FR subjects responded at higher rates. For all subjects, however, responding gradually returned to the break-and-run pattern that had occurred during the first FI competition condition. Experiment 3 assessed potential variables contributing to the effects of the competitive FI contingencies during Experiments 1 and 2. Subjects were exposed to FI schedules where (a) probability of reinforcement at completion of each fixed interval was varied, or (b) a limited hold was in effect for reinforcement. Only under the limited hold was responding similar to that observed in previous experiments.     

Cholinergic blockade, septal lesions, and DRL performance in the rat.

Four experiments describing the effects of cholinergic blockade produced by systemic injection of either atropine sulfate or atropine methyl nitrate on the differential reinforcement of low rate (DRL) responding of rats are reported. It was shown that atropine sulfate injected either chronically or at high dosage suppressed DRL responding. Injected acutely, atropine sulfate produced disinhibitory effects. When atropine was injected either chronically or acutely into animals with septal lesions, there was suppression of responding. It was suggested that the specific behavioral outcome resulting from cholinergic blockade depends on the balance resulting from the competing peripheral and central effects of such blockade.