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.     

Effect of CER on DRL responding

The effect of CER on DRL 16 was studied in four rats. All Ss showed complete CER suppression after five CER trials, together with some unconditioned post-shock suppression. This post-shock suppression showed complete recovery in all Ss after 10 days of five CER trials per day, but complete CER suppression continued throughout.     

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.     

Children's use of verbal collaterals in DRL performance

This study examines the effects of a verbal collateral (counting) on a series of three differential reinforcement of low rates of response (DRL) tasks with progressively longer interresponse time requirements (DRL-2, DRL-6 and DRL-12). Forty-eight 10-year-old children, divided according to sex and conceptual tempo (fast-inaccurate vs. slow-accurate) participated in DRL training, half of them being instructed to count aloud between responses. Counting was found to be related to faster learning of all the tasks and to greater efficiency in obtaining reinforcement in most cases. It also eliminated differences due to sex and conceptual tempo except in DRL-12. However, it had the disadvantage of causing inexact temporal discrimination. The results were replicated in a group of 8-year-old subjects performing the same tasks.     

The effect of acceleration on food-reinforced DRL and FR

Performance on DRL 10 sec and FR 5 was studied after exposure to acceleration. After four rats, two on each of the above schedules, had stabilized they were exposed to 5 hr of acceleration at 5 G immediately before daily experimental sessions. Food intake was also studied in rats given access to food daily in their home cages and exposed to acceleration immediately before the free-feeding session. Weight gain of free-feeding animals and reinforcement intake of experimental animals dropped after acceleration. Over-all response rate on the FR was depressed markedly by acceleration but local response rates did not appear to be affected. IRT distributions of DRL sessions after acceleration were markedly shifted toward the long intervals. A sequential plot of IRTs on acceleration days showed an altered, but relatively stable, temporal patterning of responses followed by an abrupt return to the normal baseline toward the end of the session.     

An analysis of programming DRL schedules in educational settings

Three methods for programming the differential reinforcement of low rate were explained, labeled, illustrated by research studies, and analyzed, but not compared. Spaced Responding DRL, the first and most common method in laboratory studies, was illustrated through the reduction of the inappropriate questioning by three behaviorally disturbed children. Full Session DRL, the most common method in applied studies, was illustrated through the reduction of talk-outs by an EMR male. Interval DRL, not previously presented in either applied or laboratory literature, was illustrated through the reduction of talk-outs by a 6-yr-old first grade girl. All methods proved effective, and an analysis of their differences and similarities was discussed.     

Reinforcement contingencies maintaining collateral responding under a DRL schedule

Two-key conjunctive schedules were studied with one key (food key) under a differential-reinforcement-of-low-rate 20-sec schedule, while the consequences of responding on another key (collateral key) were varied. When food depended not only upon a food-key interresponse time in excess of 20 sec, but also upon the occurrence of one or more collateral-key responses during the food-key interresponse time, the rate of collateral-key responding was low and food-key interresponse times rarely exceeded 20 sec. When collateral-key responses could produce a discriminative stimulus correlated with the availability of food under the DRL schedule, the discriminative stimulus functioned as a conditioned reinforcer to maintain higher rates of collateral-key responding, and the spacing of food-key responses increased. If the occurrence of the discriminative stimulus was independent of collateral-key responses, the rate of collateral-key responding was again low, but the spacing of food-key responses was still controlled by the discriminative stimulus. Both the conditioned reinforcer and the explicit reinforcement contingency could maintain collateral-key responding, but the adventitious correlation between collateral-key responses and the delivery of food could not maintain very much collateral-key responding. The pattern of responding on the food-key was determined to a much greater extent by the correlation between the discriminative stimulus and the delivery of food than by the pattern of responding on the collateral key.     

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.     

Effects of DRL and DRL combined with response cost on perseverative verbal behavior of an adult with mental retardation and obsessive compulsive disorder

Although there has been increased interest in the identification and diagnosis of obsessive compulsive disorder (OCD) in people who have developmental disabilities, clinical research has been reported infrequently. The present single‐case study evaluated the effects from systematic behavioral intervention with a 26‐year‐old man who had moderate mental retardation, OCD, and exhibited perseverative verbalizations. Verbalizations were reduced when the man gained access to preferred activities contingent upon a low response frequency (DRL: differential reinforcement of low‐rate responding). The behavior was reduced further when a DRL contingency was implemented in the form of a response cost procedure. The implications of these findings for the treatment of OCD in people with developmental disabilities are discussed. Copyright © 2001 John Wiley & Sons, Ltd.     

Operant behavior and the galvanic skin potential under DRL schedule

Motor and galvanic skin potential (GSP) activity were investigated during the conditioning, extinction, and reconditioning of motor responses under a differential reinforcement of low rate (DRL) schedule of reinforcement. Interresponse time (IRT) distributions for motor responses during conditioning and reconditioning gradually stabilized at a peak just beyond the minimal IRT required for reinforcement. Few unreinforced motor responses and "bursts" of motor responses were observed during conditioning and reconditioning. Relative to conditioning and reconditioning, extinction effected larger IRTs and smaller GSP amplitudes. GSP amplitudes were greater for unreinforced than for reinforced motor responses during conditioning and reconditioning. However, GSP amplitudes associated with the unreinforced extinction responses were smaller than either the reinforced or unreinforced responses during conditioning and reconditioning.     

RESPONSE INTERRUPTION AND DRL FOR THE REDUCTION OF RAPID EATING

We assessed the efficacy of several procedures for reducing the rate of eating responses during mealtime by three institutionalized mentally retarded clients. A time-based (15 s) response interruption procedure was implemented which resulted in little change in eating responses for 2 of 3 subjects. A spaced-responding DRL 15-s procedure resulted in decreases in eating responses to target levels only after a prompting procedure was added. Procedures were evaluated using a multiple baseline across subjects design with assessment of generalization to nontreated meals. A change in eating behavior during breakfast occurred only after direct training in the breakfast setting. Maintenance data were collected at 1- and 5-month follow-up periods.     

DRL interresponse-time distributions: quantification by peak deviation analysis.

Peak deviation analysis is a quantitative technique for characterizing interresponse-time distributions that result from training on differential-reinforcement-of-low-rate schedules of reinforcement. It compares each rat's obtained interresponse-time distribution to the corresponding negative exponential distribution that would have occurred if the rat had emitted the same number of responses randomly in time, at the same rate. The comparison of the obtained distributions with corresponding negative exponential distributions provides the basis for computing three standardized metrics (burst ratio, peak location, and peak area) that quantitatively characterize the profile of the obtained interresponse-time distributions. In Experiment 1 peak deviation analysis quantitatively described the difference between the interresponse-time distributions of rats trained on variable-interval 300-s and differential-reinforcement-of-low-rate 72-s schedules of reinforcement. In Experiment 2 peak deviation analysis differentiated between the effects of the psychomotor stimulant d-amphetamine, the anxiolytic compound chlordiazepoxide, and the antidepressant desipramine. The results suggest that peak deviation analysis of interresponse-time distributions may provide a useful behavioral assay system for characterizing the effects of drugs.     

Decreasing classroom misbehavior through the use of DRL schedules of reinforcement

In three studies, reinforcing low rates of responding reduced inappropriate behaviors. In the first study, the talking-out behavior of one TMR student was reduced when the teacher allowed 5 min of free time for a talk-out rate less than 0.06 per minute. In a second study, the talking-out behavior of an entire TMR class was reduced when reinforcement was delivered for a response rate less than 0.10 per minute. In a third study, successively decreasing DRL limits were used to reduce off-task verbalizations of an entire high school business class. In each case, the DRL procedure proved manageable for the teacher and successful in reducing misbehavior.     

Effects of a DRL contingency added to a fixed-interval reinforcement schedule

Following 30 days of reinforcement for the bar press response of two white rats on 30-sec fixed-interval (FI), a DRL component was added so that a minimal interresponse time (IRT) for the reinforced response, in addition to the FI variable, was necessary for reinforcement. Marked control over response rate by the superimposed DRL requirement was demonstrated by an inverse hyperbolic function as the DRL component was increased from 1 to 24 sec within the constant 30-sec FI interval. Interresponse time and post-reinforcement (post-S^R) “break” distributions taken at one experimental point (DRL = 24 sec) suggested that a more precise temporal discrimination was initiated by an S^R than by a response, since the relative frequency of a sequence of two reinforced responses appeared greater than that of a sequence of a non-reinforced response followed by a reinforced one. This latter finding was confirmed with new animals in a follow-up experiment employing a conventional 24-sec DRL schedule.     

Intra-habenular injection of 6-hydroxydopamine produces impaired acquisition of DRL operant behavior

The anatomical connections of the habenula complex indicate it provides a relay between limbic forebrain and midbrain. Somewhat paradoxically, consequences of nonspecific lesion of the habenula are ambiguous with little change in basic response evident within simple behavioral paradigms. However, the potential functional importance for this relay has more recently been indicated by the demonstration of deficits in the ability of lesioned animals to alter behavior appropriate to both internal and external stimuli in more demanding behavioral tasks. Doubts concerning the importance of the habenula remain because of the large number of descending fibers of passage through the habenula. To provide more substantive evidence, 6-hydroxydopamine was injected into the habenula of rats to provide more limited lesion of catecholaminergic terminals. Animals were subsequently trained on an operant DRL 20-s schedule for which deficits have been reported following nonspecific lesion of the habenula. Lesioned animals showed a tendency to overrespond and were significantly less efficient on the schedule with decreased number of reinforcements received relative to controls. While the neurotoxic lesion procedure used does not differentiate noradrenergic and dopaminergic damage, the importance of intact catecholaminergic systems within the habenula for effective DRL acquisition is consistent with the suggested importance of the habenula for feedback regulation of dopamine within the ventral tegmental area through ascending dopamine fibers to the habenula.