Spaced responding in multiple DRL schedules

Rats were able to adjust to two different temporal requirements within several multiple DRL schedules of reinforcement, and a slight induction between pairs of components was found. Initial administration of dl-amphetamine differentially disrupted spaced responding in the components of a multiple DRL 36 DRL 18 schedule, but did not eliminate discrimination between the components. After maximum drug effects, the continued administration of dl-amphetamine was accompanied by a progressive recovery of the behavior towards the characteristics of saline control.     

Reinforcement of mediating behavior on a spaced-responding schedule

This paper describes a procedure for gaining experimental control over mediating behavior on a spaced-responding schedule of food reinforcement. Three rats, food-deprived, were trained on a DRL 16 sec schedule of food reinforcement. Then, a concurrent schedule of food reinforcement was introduced on a second (mediating) lever, such that the first response to occur on the mediating lever, after the DRL interval had timed out, was reinforced with food, as was the next response to occur on the DRL lever. Reinforcement via the mediating lever became a discriminative stimulus for a food-reinforcement opportunity on the DRL lever. Next, food reinforcement for the mediating behavior was replaced by a conditioned reinforcer consisting of onset of a buzzer signaling timing-out of the DRL interval. Under these conditions, chaining of behavior on the two levers was strong, and timing on the DRL lever was more accurate than under ordinary DRL conditions. As the DRL requirement was lengthened from 16 sec to 24 sec to 60 sec, mediating behavior weakened slightly. When the inter-response requirement for food reinforcement on the DRL lever was made shorter than the inter-response requirement for conditioned reinforcement on the mediating lever, the mediating behavior extinguished. Performance in the experiment was analyzed into a four-component chain, and the factors contributing to the maintenance, and later extinction, of mediating behavior are discussed.     

Implementing a differential reinforcement of low rates schedule to alter vocal stereotypy and task engagement in two adolescents with autism spectrum disorder

Vocal stereotypy (VS) is often observed in individuals with autism spectrum disorder (ASD) which at high rates can interfere with socialization or functioning in structured settings. There are multiple effective interventions available; yet, many procedures target the complete omission of the behavior or are only assessed at short intervals, making it unclear how they will generalize in applied settings. One intervention yet to be assessed as an individual intervention for automatically reinforced VS is differential reinforcement of low rates of behavior (DRL). In the present study, a functional analysis determined that the VS of two female adolescents with ASD was maintained by automatic reinforcement. A DRL procedure was implemented which incorporated: (a) a specified interval for reinforcement; (b) the behavioral expectations; (c) the permissible instances of VS within the interval; (d) learner feedback; and (e) the reset/non-reset aspect of the schedule. As the targeted behavior decreased across sessions, the DRL interval was systematically increased in order to thin out the schedule of reinforcement. The intervention reduced VS and increased untargeted task engagement for both participants. Applied and theoretical implications of the study as well as social validity, limitations, and future research are discussed.     

Differential reinforcement of low rates performance by impulsive and reflective children

Third-grade boys classified as either cognitively impulsive or reflective were reinforced for key pressing according to a DRL (differential reinforcement of low rates) 6-sec schedule of reinforcement. Half of each group received instructions about the behavioral requirements for obtaining reinforcements. Prior to DRL training, impulsive Ss showed a low probability of key press responding at long interresponse time (IRT) intervals while reflective Ss exhibited an equal probability of terminating either short or long IRTs. During training and in the absence of instructions, impulsives exhibited a less precise temporal discrimination, characterized by a greater predominance of response bursts (0–2 sec IRTs) following reinforcements, than reflective Ss. While impulsive and reflective Ss displayed similar frequencies of collateral behavior between successively reinforced responses, impulsives engaged in the reinforced response more frequently and tended (p < .08) to obtain fewer reinforcements. Instructions served to enhance the DRL performance.     

Effects of a brief novel stimulus during temporally spaced responding: Evidence for external inhibition?

Following training on schedules which differentially reinforce low rates of responding (DRL), three rats were exposed to a procedure to test for external inhibition. During test trials, a tone was presented midway in the DRL interval and the latency to the next response recorded. The incidence of external inhibition (defined in terms of the latency and its relative probability) appeared to be positively related to the size of the DRL schedule and not to measures of the subject’s “efficiency” on the schedule. An alternative view to the “pure” disinhibition hypothesis is presented which stresses the disruption of collateral behavior sequences which maintain responding under the DRL schedule.     

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.     

The effect of physical restraint on behavior under the differential-reinforcement-of-low-rate schedule

Previous studies have identified and manipulated collateral behavior to assess the effect of collateral behavior on performance under the differential-reinforcement-of-low-rate (DRL) schedule. However, conclusions could not be applied to subjects not observed to engage in collateral behavior. The present study used a technique that prevented the occurrence of the types of collateral behavior typically observed in the pigeon. This technique did not require the identification of collateral behavior in the subjects. The exclusion of the types of collateral behavior typically observed in pigeons resulted in higher response rates and lower reinforcement rates under large DRL values but had no effect at lower DRL values. It was concluded that collateral behavior is necessary for low response rates and high reinforcement rates under large DRL values.     

THE EFFECT OF CHANGES IN CRITERION VALUE ON DIFFERENTIAL REINFORCEMENT OF LOW RATE SCHEDULE PERFORMANCE

The differential reinforcement of low rate (DRL) schedule is commonly used to assess impulsivity, hyperactivity, and the cognitive effects of pharmacological treatments on performance. A DRL schedule requires subjects to wait a certain minimum amount of time between successive responses to receive reinforcement. The DRL criterion value, which specifies the minimum wait time between responses, is often shifted towards increasingly longer values over the course of training. However, the process invoked by shifting DRL values is poorly understood. Experiment 1 compared performance on a DRL 30‐s schedule versus a DRL 15‐s schedule that was later shifted to a DRL 30‐s schedule. Dependent measures assessing interresponse time (IRT) production and reward‐earning efficiency showed significant detrimental effects following a DRL schedule transition in comparison with the performance on a maintained DRL 30‐s schedule. Experiments 2a and 2b assessed the effects of small incremental changes vs. a sudden large shift in the DRL criterion on performance. The incremental changes produced little to no disruption in performance compared to a sudden large shift. The results indicate that the common practice of incrementing the DRL criterion over sessions may be an inefficient means of training stable DRL performance.     

Some determinants of remote behavioral history effects in humans

Undergraduates were exposed to a series of reinforcement schedules: first, to a fixed-ratio (FR) schedule in the presence of one stimulus and to a differential-reinforcement-of-low-rate (DRL) schedule in the presence of another (multiple FR DRL training), then to a fixed-interval (FI) schedule in the presence of a third stimulus (FI baseline), next to the FI schedule under the stimuli previously correlated with the FR and DRL schedules (multiple FI FI testing), and, finally, to a single session of the multiple FR DRL schedule again (multiple FR DRL testing). Response rates during the multiple FI FI schedule were higher under the former FR stimulus than under the former DRL stimulus. This effect of remote histories was prolonged when either the number of FI-baseline sessions was small or zero, or the time interval between the multiple FR DRL training and the multiple FI FI testing was short. Response rates under these two stimuli converged with continued exposure to the multiple FI FI schedule in most cases, but quickly differentiated when the schedule returned to the multiple FR DRL.     

Reinforcement schedule thinning following treatment with functional communication training

We evaluated four methods for increasing the practicality of functional communication training (FCT) by decreasing the frequency of reinforcement for alternative behavior. Three participants whose problem behaviors were maintained by positive reinforcement were treated successfully with FCT in which reinforcement for alternative behavior was initially delivered on fixed-ratio (FR) 1 schedules. One participant was then exposed to increasing delays to reinforcement under FR 1, a graduated fixed-interval (FI) schedule, and a graduated multiple-schedule arrangement in which signaled periods of reinforcement and extinction were alternated. Results showed that (a) increasing delays resulted in extinction of the alternative behavior, (b) the FI schedule produced undesirably high rates of the alternative behavior, and (c) the multiple schedule resulted in moderate and stable levels of the alternative behavior as the duration of the extinction component was increased. The other 2 participants were exposed to graduated mixed-schedule (unsignaled alternation between reinforcement and extinction components) and multiple-schedule (signaled alternation between reinforcement and extinction components) arrangements in which the durations of the reinforcement and extinction components were modified. Results obtained for these 2 participants indicated that the use of discriminative stimuli in the multiple schedule facilitated reinforcement schedule thinning. Upon completion of treatment, problem behavior remained low (or at zero), whereas alternative behavior was maintained as well as differentiated during a multiple-schedule arrangement consisting of a 4-min extinction period followed by a 1-min reinforcement period.     

Transfer of control of the pigeon's key peck from food reinforcement to avoidance of shock

Eight pigeons were initially trained to peck a white key for food under a variable-interval 1-min schedule of reinforcement. Then, a shock-avoidance schedule was initiated and food was no longer available in the experimental situation. Under the avoidance schedule, each peck on the key postponed shock for 40 sec. A warning signal, consisting of tone and red houselights, was presented after 30 sec without a response. If no response occurred, a shock was delivered 10 sec after warning-signal onset. Shocks were delivered every 10 sec in the presence of the warning signal until a response was made. The warning signal was terminated only by a response. Key pecking of all eight pigeons came under control of the avoidance schedule and responding continued throughout the 20-day avoidance training period.     

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.     

Drug effects on fixed-interval responding with pause requirements for food presentation.

In pigeons performing under a multiple schedule of food presentation, low key-pecking rates (0.18 to 0.29 responses per second) were maintained during 3-min fixed-interval components by requiring a 4-, 5-, or 6-sec pause preceding the food-delivery response (tandem DRL), while higher rates (0.70 to 1.37 responses per second) were maintained in alternative fixed-interval components by requiring a pause of no more than 40 msec preceding the food-delivery response (tandem DRH). Thus, reinforcement density was equal but overall response rates markedly different in the two schedule components. Pentobarbital (3, 10 mg/kg) had effects on overall rates of responding consistent with a rate-dependency interpretation (low rates were increased while higher rates were decreased), but d-amphetamine (0.03 to 3 mg/kg) either failed to increase low overall rates in the tandem DRL components or increased them only slightly. Effects of both drugs on local responding within the fixed-intervals were always related in an orderly way to control response rate, but the extent of rate increases produced by d-amphetamine was modifed in some birds by pause requirements such that the drug increased comparable rates less when these occurred in the tandem DRL component than when they occurred in the tandem DRH components. Control rate is an important determinant of drug effects, independent DRH components. Control rate is an important determinant of drug effects, independent of reinforcement density maintaining rates, and independent of environmental influences, such as response-spacing requirements for food presentation, that can modify the extent of some drug-produced rate changes.     

A developmental study of timing behavior in 4 1/2- and 7-year-old children

The present study investigated effects of age and instructions on temporal regulations of behavior in children. In the first experiment 4 1/2-year-old and 7-year-old subjects were trained with a DRL (differential reinforcement of low rates) 5-s and a DRL 10-s schedule. Results demonstrate that age and timing performance are related. Seven-year-olds are more efficient than the 4 1/2-year-olds. A striking decline in the 4 1/2-year-old children's capacity to space responses was observed in the DRL 10-s schedule as compared to the DRL 5-s schedule. Analysis of individual performances suggests that the evolution of DRL performance between 4 and 7 years of age depends not only on the development of the capacity to delay responding but also on the acquisition of the ability to represent the reinforcement contingencies, that is, the temporal parameters of the task to oneself. In order to test this hypothesis a second experiment was conducted where instructions to wait between operant responses were given to a group of 4 1/2-year-old subjects at the beginning of a DRL 5-s and a DRL 10-s schedule. The results show that these instructions enhance DRL performance. By directing the 4 1/2-year-old subjects' attention to the temporal requirements of the task, instructions led to efficient performance and accurate timing of responses to the DRL schedule.     

Risky economic choices and frontal EEG asymmetry in the context of Reinforcer-Sensitivity-Theory-5

This study investigated individual risky choice behavior in a gambling task and its relation with traits proposed by the Reinforcer-Sensitivity-Theory-5 (RST-5; Corr & McNaughton in Neuroscience and Biobehavioral Reviews, 36(10), 2339–2354, 2012) as well as with frontal EEG asymmetry. As assumed by the RST-5, the results showed independent influences of approach/avoidance and gain/loss sensitivities on participants’ behavior in risky choices. Individual approach/avoidance sensitivity was predicted by trait measures of the behavioral approach system (BAS) and the behavioral inhibition system (BIS), while no such correlation was present for gain/loss sensitivity. EEG recordings revealed relatively stronger left-frontal cortical activity for trials with approach motivation compared to conflict and avoidance motivation. On the individual level, relatively stronger left-frontal cortical activity was associated with trait BAS. In addition, activity changes in frontal EEG asymmetry were associated relatively higher behavioral approach sensitivity. We conclude that frontal EEG asymmetry is an especially useful neuronal marker of BAS sensitivity and that the traits proposed by the RST-5 (measured by frontal EEG asymmetry and self-report) can be used to explain individual differences in risky choice behavior.     

Differential reinforcement of low rates of responding (DRL) to reduce dysfunctional social behaviors of a head injured man

Differential reinforcement of low rates of responding (DRL) is a technique in which a positive reinforcer is delivered at the end of a specific interval if a target behavior has occurred at a criterion rate. Traditionally, it has been used in educational settings to manage classroom behaviors. Recently, therapists have begun to use DRL to reduce the rates of a variety of behaviors in non-educational settings. In this study, DRL was part of a behavioral intervention to reduce dysfunctional verbal and physical behaviors of a head-injured young man. The complete intervention program included DRL, changing criteria, and token reinforcement. Over a period of 15 weeks, the intervention resulted in reductions in behaviors in both categories from high rates to near-zero rates.     

Response suppression on DRL by rats with septal damage

The effectiveness of the differential reinforcement for low rates of responding (DRL) contingency in suppressing response rates of septal rats was investigated by using a Multi-DRL-yoked-VI (variable interval) schedule of reinforcement. The yoking procedure equated the interreinforcement times on the two schedules. Each schedule was in effect for half of each session, and the change in schedule was signaled by the presence or absence of a cue light. Schedule order and DRL delay requirement were varied. For both normal and septal rats, the response rates were higher in the VI component than the DRL component; this effect demonstrates that the responding of septals as well as normals is suppressed by the differential reinforcement of a particular class of IRTs. A sharp difference in the level of responding occurred at the point of transition from one component of the multiple schedule to the other, which provides evidence of a discrimination between the two schedules for both normals and septals. The conclusion is that the responding of septals is suppressed by the DRL contingency and not controlled solely by the density and distribution of reinforcement.     

Schedule-induced licking during multiple schedules

Schedule-induced polydipsia was studied in rats bar pressing under two-component multiple schedules of food reinforcement. The first component of the multiple schedule was a variable-interval 1-min schedule throughout the experiment. The schedule comprising the second component was varied over blocks of sessions in terms of rate and magnitude of reinforcement, and was either variable-interval 3-min (one pellet), variable-interval 3-min (three pellets), variable-interval 1-min (one pellet), or extinction. Water intake per session varied with the rate of reinforcement in the schedule comprising the second component and was highest when the schedule was variable-interval 1-min. Both bar-pressing behavior and licking behavior showed behavioral interactions between the two components of the multiple schedules. With magnitude of reinforcement held constant, a matching relationship was observed between lick rate and reinforcement rate; the relative frequency of licks in the constant component matched the relative frequency of reinforcement in that component. Bar pressing, however, showed only a moderate degree of relativity matching. During the schedule-induced licking, a burst of licking followed each delivery of a pellet (post-prandial drinking). The duration of these bursts of licking was observed to be a function of the inter-reinforcement interval.     

Effects of chlorpromazine on appetitive and aversive components of a multiple schedule

A multiple schedule having both an appetitive and an avoidance component was maintained in two dogs to create a complex behavioral base line for observing the effects of chlorpromazine. Both soluble and “Spansule” chlorpromazine generated similar functions relating drug dose to measures of behavioral output. Although the dose ranges and the drugging procedures differed markedly for the different preparations of CPZ, the functions generated were comparable. There was no evidence that chlorpromazine had a differential depressing effect as a function of type of reinforcement. At low doses, rates of responding on the food-reinforced components increased slightly, whereas rates on the avoidance components remained relatively unchanged. At higher doses, both components showed an approximately equal depression of responding. These results are discussed with reference to some of the logical and experimental difficulties inherent in making comparisons across components of a multiple schedule and across schedules in general.     

Effects of dl-amphetamine under concurrent VI DRL reinforcement

Three adult, food-deprived rats were given IP injections of dl-amphetamine sulfate under DRL and concurrent VI DRL reinforcement schedules. The drug results were as follows.(1) The IRT distributions of DRL responses shifted to the left, but some temporal discrimination remained. (2) The IRT distributions of VI responses shifted slightly to the left. (3) The distinguishing characteristics of VI and DRL IRT distributions were preserved. (4) The frequency distribution of number of VI responses between two consecutive DRL responses was relatively unaffected. (5) Over-all response rates on the two components of the concurrent schedules increased more or less proportionately.These findings imply that the primary behavioral effect of dl-amphetamine was a motor excitatory one. The drug's disruption of timing behavior was not due to a derangement of internal timing mechanisms, nor to interference with the topography or pattern of behavior. Rather, it might be a secondary result of the accelerated emission of overt behavior patterns mediating the temporal spacing of DRL bar presses.