An analysis of overcorrection movements.

Overcorrection procedures were designed for three profoundly retarded adults such that the overcorrection activities were topographically dissimilar to (i.e., did not physically prevent) the stereotyped behavior targeted for treatment. Using reversal designs, we recorded data on both the target behavior and the behavior used as the overcorrection responses. Results showed that overcorrection was effective in reducing the stereotyped behavior for each subject; however, the rates of the overcorrection responses either remained variable or decreased during the treatment phases. These findings suggest that although overcorrection is a valuable technique in reducing behavior, the overcorrection responses (e.g., restitutional acts, positive practice, functional movement training) may not increase in the absence of specific reinforcement contingencies. The importance of utilizing differential reinforcement procedures, especially with mentally retarded persons, in conjunction with ocercorrection was discussed.     

Reduction of stereotyped body-rocking using variable time reinforcement: practical and theoretical implications

The first experiment assessed the effectiveness of two schedules of reinforcement in reducing stereotypy engaged in profoundly retarded patients in ward environments. These schedules were the differential reinforcement of other behaviour (DRO) and variable time reinforcement (VT). This experiment was terminated prematurely because of problems in implementing the DRO contingencies. However, the VT contingency appeared to reduce stereotypy. The second experiment evaluated the VT schedule of reinforcement alone. Significant decreases in amounts of stereotypy from baseline measures were observed in all five profoundly retarded female subjects. It is tentatively concluded that stereotypies in ward and laboratory environments differ in function. This has implications for the treatment of patients who engage in stereotyped behaviour.     

Incentive maintenance of self-help skill training programs for non-professional personnel

Two experiments were conducted over 24- and 28-week periods of time to investigate the use of peer competition and two schedules of money reinforcement to increase the rate in the cottage self-help skills training sessions. Nineteen attendants, working with profoundly and severely retarded institutionalized individuals on two cottages, served as subjects. Both experiments included five phases presented in differing order; Baseline I, Peer Competition, Behavioral Engineer Money, Bingo Money, and Baseline II. These experiments indicated that payment of non-professional personnel, with small amounts of money, contingent upon job performance, produced dramatic increases in the rate of daily training sessions conducted in the cottages. The order in which the two schedules of money reinforcement interacted with the ongoing rate of daily sessions produced marketly different results.     

Teaching mute retarded children vocal imitation

This paper describes a system used by eight institution staff members to teach vocal imitative responses to three nonvocal retarded children. The system may be characterized by: (1) a response classification scheme and a recording and graphing procedure which give detailed information regarding the nature and progress of the shaping; (2) the use of objective criteria to guide the trainer in applying differential reinforcement and in shifting reinforcement schedules during the course of training; and (3) the use of specific prompting techniques. Data are presented to illustrate the progress of the children. The system appeared practical and explicit enough to be adopted by child care staff, without involving a great deal of professional supervision.     

Binaural interaction in auditory brainstem responses of mentally retarded and nonretarded individuals

The short-latency auditory brainstem responses of institutionalized mentally retarded individuals (Down syndrome and unknown etiology) and nonretarded control persons were recorded. The results showed that retarded individuals differed in the clarity of initial auditory brainstem response waves (I and II). Down syndrome individuals had significantly smaller auditory brainstem response amplitudes (Waves II and III) when compared with retarded individuals of unknown etiology. Down syndrome individuals also had significantly shorter latencies (Waves III and V) and shorter interwave conduction times (III-I and V-I) when compared with retarded individuals of unknown etiology. Retarded individuals did not differ from control subjects when amplitudes of binaural auditory brainstem responses were compared to the computer summation of such responses evoked by left and right ear stimulation; however, there was evidence for a general binaural interaction effect.     

The behavior of male and female Wistar rats pressing a lever for food is not affected by sex differences in food motivation

Male rats both eat more and weigh more than females. Differences in food intake and body weight result, at least partly, from differences in gonadal hormone secretions. The present experiments were designed to investigate whether sex differences in food motivation might contribute to the behavioral differences observed when food-deprived male and female rats are exposed to appetitively motivated operant learning tasks. Male and female Wistar rats were exposed to different progressive ratio schedules of reinforcement which have been shown to generate reliable indices of 'motivational' conditions. In progressive ratio schedules, subjects are required to make a systematically increasing number of responses for each successive reinforcer, until the requirement becomes so large that the subjects stop responding. Expt. Ia was designed to investigate whether or not food-deprived males would be more motivated than food-deprived females to obtain food. Expt. Ib investigated whether gonadectomy might differentially affect food motivation of male and female rats exposed to a progressive ratio schedule of reinforcement. Motivational differences between males and females were not observed. Males and females obtained an equal number of reinforcers, while differences in the total number of responses and response rate were not observed. Gonadectomy did not affect the total number of responses in the final completed ratio. The results of the present experiments do therefore not support the hypothesis that sex differences in food motivation might underlie sex differences in behavior when food-deprived male and female rats are exposed to operant schedules of positive reinforcement.     

Comparison of DRO and DRI on rate of suppression of self-injurious behavior.

Two procedures were used to compare the effects of differential reinforcement of other behavior (DRO) and differential reinforcement of incompatible behavior (DRI) on self-injurious behavior (SIB) of three profoundly retarded head-bangers in a multiple-schedule within-subjects design. We found that rewarding a response specifically incompatible with SIB suppressed it more rapidly than applying DRO without specifying an alternative response. The relationship of collateral behaviors to SIB were dependent upon the repertoires of the individual clients.     

Fixed-consecutive-number performance in male and female Wistar rats

The present experiment was designed to investigate whether or not response rate differences between male and female Wistar rats observed in many different experimental procedures could be attributed to sex differences in behavioral perseverance, as has been suggested by the results of previous experiments. Male and female Wistar rats were thus exposed to different fixed-consecutive-number schedules of reinforcement. Fixed-consecutive-number schedules require subjects to emit a specified number of responses on one (work) lever, before a response on another (food) lever results in the presentation of reinforcement. The response requirement on the work lever was manipulated in different experimental conditions. Subjects had to emit between 3 and 7, 8 and 12 or 13 and 17 responses on the work lever before a response on the food lever produced reinforcement. When subjects emitted fewer or more than the required number of responses on the work lever, a 5-s time-out period was presented. Males responded at higher rates than females during all experimental conditions; response rates of males and females increased as the response requirement on the work lever was increased. Sex differences in response efficiency were not observed, but males seemed to reach final response efficiency faster than females. Response efficiency decreased as the response requirement on the work lever was increased. Error analysis showed that both males and females made more errors by not producing enough responses on the work lever than by producing too many. However, males were more likely than females to emit more responses than the requirement on the work lever, while females were more likely than males not to produce enough responses on the work lever.     

Effects of response satiation procedures in the treatment of aerophagia

A contingent response that previously increased self-injurious air-swallowing (aerophagia) by a profoundly mentally retarded woman (Holburn & Dougher, 1985) was shown to decrease her air-swallowing when the response was presented in accord with the response deprivation/satiation hypothesis, which suggests that any free-operant response can serve as a reinforcer or a punisher depending upon specific contigency arrangements. The results offer an explanation for the earlier increase in air-swallowing.     

Eyelid conditioning and intellectual level: effects of repeated acquisition and extinction.

Groups of college students and moderately retarded persons averaging approximately equal age received eight alternating phases of acquisition and extinction trials with an electric pulse as the unconditioned stimulus for classical eyelid conditioning. The two conditioning groups did not differ significantly in attaining the acquisition criterion during any phase and showed systematic improvement in approaching the maximal rate of acquisition. However, the college students exhibited abrupt extinction in every phase, in contrast to retarded subjects. "Learning to learn" in the retarded group was more marked across acquisition than across extinction phases. Random control groups of the two subject classes displayed equal relative frequencies of nonconditioned blinks. Some of the findings clearly contradict a stimulus-context hypothesis of differences in learning rate associated with IQ level.     

Sensory reinforcement of head turning with nonambulatory, profoundly mentally retarded persons

Two experiments examined the reinforcing value of response contingent sensory events consisting of combinations of visual, auditory, and vibratory stimulation. Ten nonambulatory, profoundly mentally retarded individuals participated in these studies. Four different stimulus combinations were required to achieve operant conditioning of head turning responses in 6 participants. These sensory reinforcers included 5-s simultaneous presentations of picture, music, and vibration (N = 2), picture and music (N = 2), picture and vibration (N = 1), and picture alone (N = 1). These results indicate that systematically varying a multimodal sensory event is a fruitful procedure for identifying positive reinforcers for nonambulatory, profoundly mentally retarded persons.     

An evaluation of the additive effects of lag schedules of reinforcement

Lag schedules of reinforcement represent an increasingly researched strategy for addressing restricted and repetitive social communication of individuals with autism spectrum disorder (ASD). Although the body of literature suggests that lag schedules of reinforcement are generally effective for this purpose, studies have varied in their utilization of verbal rules describing the contingency. Furthermore, research has yet to evaluate generalized effects of lag schedules of reinforcement to social communication with peers. This study evaluated the implementation of a social skills curriculum, modified to incorporate lag schedules of reinforcement, on novel responding of participants with ASD. Participants attended training twice per week, with probes of novel responding collected with both researchers and non-participating peers. Results indicate that social skills training that incorporated lag schedules of reinforcement generally resulted in larger increases in novel responding than social skills training alone. Furthermore, effects of training generalized to novel responding to non-participant peers.     

Involvement of the basolateral complex and central nucleus of amygdala in the omission effects of different magnitudes of reinforcement

Evidence from appetitive Pavlovian and instrumental conditioning studies suggest that the amygdala is involved in modulation of responses correlated with motivational states, and therefore, to the modulation of processes probably underlying reinforcement omission effects. The present study aimed to clarify whether or not the mechanisms related to reinforcement omission effects of different magnitudes depend on basolateral complex and central nucleus of amygdala. Rats were trained on a fixed-interval 12s with limited hold 6s signaled schedule in which correct responses were always followed by one of two reinforcement magnitudes. Bilateral lesions of the basolateral complex and central nucleus were made after acquisition of stable performance. After postoperative recovery, the training was changed from 100% to 50% reinforcement schedules. The results showed that lesions of the basolateral complex and central nucleus did not eliminate or reduce, but interfere with reinforcement omission effects. The response from rats of both the basolateral complex and central nucleus lesioned group was higher relative to that of the rats of their respective sham-lesioned groups after reinforcement omission. Thus, the lesioned rats were more sensitive to the omission effect. Moreover, the basolateral complex lesions prevented the magnitude effect on reinforcement omission effects. Basolateral complex lesioned rats showed no differential performance following omission of larger and smaller reinforcement magnitude. Thus, the basolateral complex is involved in incentive processes relative to omission of different reinforcement magnitudes. Therefore, it is possible that reinforcement omission effects are modulated by brain circuitry which involves amygdala.     

Role of strategy in reading by mentally retarded persons

Mentally retarded individuals who could read were tested on their ability to pronounce words and produce meaningful associates. Analyses of their responses indicated an overuse of a strategy of memorizing works as a way to recognize words in print and an inability to consider work meanings in terms of abstract referents. A comparison of these results with responses given by nonretarded children suggests that retarded persons use cognitive strategies that lead to inefficient reading and even interfere with the development of effective reading skills.     

Attenuation of sucrose reinforcement in dopamine D1 receptor deficient mice

Dopaminergic systems are thought to mediate the rewarding and reinforcing effects of palatable food. However, the relative contribution of different dopamine receptor subtypes is not clear. We used dopamine D1 receptor deficient mice (D1 -/-) and their wild-type and heterozygous littermates to study the role of the D1 receptor in palatable food reinforced behaviour using operant responding and free access paradigms. Non-deprived mice were trained to press a lever for sucrose pellets under three schedules of reinforcement including fixed ratios (FR-1 and FR-4) and a progressive ratio (PR). Responding on one lever was reinforced by the delivery of a sucrose pellet or solution while responding on a second lever had no programmed consequences. Initially, D1 mutant mice took longer to learn to discriminate between the two levers and had significantly lower operant responding for sucrose pellets and solution than wild-type and heterozygous mice under all schedules of reinforcement. Food deprivation enhanced responding on the active lever in all mice although it remained significantly lower in D1 -/- mice than in control mice. Following extinction of sucrose reinforcement and reversal of the levers, D1 -/- mice showed deficits in extinguishing and reversing previously learned responses. Home cage intake and preference of sucrose pellets and solutions when given under free-choice access paradigms were similar among the groups. These results suggest that the dopamine D1 receptor plays a role in the motivation to work for reward (palatable food) but not in reward perception and is critical in learning new but relevant information and discontinuing previously learned responses.     

Noncontingent reinforcement: effects of satiation versus choice responding

Recent research findings suggest that the initial reductive effects of noncontingent reinforcement (NCR) schedules on destructive behavior result from the establishing effects of an antecedent stimulus (i.e., the availability of "free" reinforcement) rather than extinction. A number of authors have suggested that these antecedent effects result primarily from reinforcer satiation, but an alternative hypothesis is that the individual attempts to access contingent reinforcement primarily when noncontingent reinforcement is unavailable, but chooses not to access contingent reinforcement when noncontingent reinforcement is available. If the satiation hypothesis is more accurate, then the reductive effects of NCR should increase over the course of a session, especially for denser schedules of NCR, and should occur during both NCR delivery and the NCR inter-reinforcement interval (NCR IRI). If the choice hypothesis is more accurate, then the reductive effects of NCR should be relatively constant over the course of a session for both denser and leaner schedules of NCR and should occur almost exclusively during the NCR interval (rather than the NCR IRI). To evaluate these hypotheses, we examined within-session trends of destructive behavior with denser and leaner schedules of NCR (without extinction), and also measured responding in the NCR interval separate from responding in the NCR IRI. Reductions in destructive behavior were mostly due to the participants choosing not to access contingent reinforcement when NCR was being delivered and only minimally due to reinforcer satiation.     

Effects of antiepileptic drugs and seizure type on operant responding in mentally retarded persons

The performance of 129 mentally retarded persons was studied on a progressive fixed-ratio schedule of reinforcement. Subjects were selected according to antiepileptic drug (AED) regimen or membership in one of four control groups. The AEDs studied were: phenobarbital (PB); phenytoin (PHT); PB in combination with PHT (PB/PHT); and valproic acid (VPA) in combination with other AEDs . The control groups were: persons without seizure disorders and on no medications (control); persons without seizure disorders, but on the chronic medication thioridazine ( TDZ ); persons with histories of one or more seizures and treatment with PB and/or PHT, but currently on no AEDs ; and, to control for the effects of multiple AEDs , persons on multiple drug regimens (i.e., PB and/or PHT in combination with carbamazepine and/or ethosuximide). Except for the VPA group, response rates per minute were decreased in high intelligence quotient (greater than 40) persons receiving AEDs or with a history of treated seizures. Deficits in responding were particularly marked in persons with partial seizures. Persons on VPA responded at rates comparable with those of the control and TDZ groups, unless they had partial seizures. This effect was independent of seizure frequency and was inversely related to serum level. Persons on PB most frequently exhibited frustration responses during testing, and when these occurred they were rated as being significantly more severe. Persons on PB also most frequently elected to "leave the experiment" and did so primarily for reasons thought to reflect deficits in inhibition. These results suggest that operant tasks can be sensitive to both AED effects and to underlying alterations of function that accompany seizure disorders in the mentally retarded.     

Effects of delayed reinforcers on the behavior of an animal model of attention-deficit/hyperactivity disorder (ADHD)

Attention-deficit/hyperactivity disorder (ADHD), affecting 3-5% of grade-school children, is a behavioral disorder characterized by developmentally inappropriate levels of inattention, hyperactivity, and impulsivity. It has been suggested that the symptoms are caused by altered reinforcement and extinction processes, behaviorally described as an abnormally short and steep delay-of-reinforcement gradient in ADHD. The present study tested predictions from the suggested shortened and steepened delay gradient in ADHD in an animal model, the spontaneously hypertensive rats (SHRs). It was predicted that SHR responding during baseline would mainly consist of responses with short inter-response times, and that responding would be more rapidly reduced in the SHR than in the controls by the introduction of a time interval between the response and reinforcer delivery. Effects of a resetting delay of reinforcement procedure with water as the reinforcer were tested on two baseline reinforcement schedules: variable interval 30 s (VI 30 s) and conjoint variable interval 60 s differential reinforcement of high rate 1s (VI 60 s DRH 1 s). The results showed a higher rate of responses in the SHR than in the controls during baseline, mainly consisting of responses with short inter-response times. The statistical analyses showed that response rates decreased more rapidly as a function of reinforcer delay in the SHR than in the controls. The analyses of the estimates of the reinforcer decay parameter showed no strain differences during the VI 30 s schedule but showed a significant strain difference at the end, but not at the start, of the sessions during the VI 60 s DRH 1 s schedule. In general, the results support predictions from the suggested steepened delay gradient in SHR. However, the predictions were only partly confirmed by the analyses of the decay parameter.     

Reinforcement delay of one second severely impairs acquisition of brain self-stimulation

The effect of delayed reinforcement on the acquisition of lateral hypothalamic self-stimulation was investigated. Brain stimulation reinforcement minimizes cues associated with reinforcement delivery (secondary reinforcement) and, by eliminating consummatory responses, permits precise temporal control of the interval between the operant response and reinforcement. Different groups were trained in daily 1-h sessions for brain stimulation reinforcement at one of 4 delay intervals (1, 2, 3 or 6 s). Responses made during the delay interval were not reinforced and reset the delay timer. Control groups (IMMEDIATE) were reinforced immediately, but were required to space responses--according to a delayed reinforcement of low rates (DRL) schedule--for an interval corresponding to one of the delay of reinforcement intervals. The DRL schedule equalized opportunities for reinforcement and non-reinforcement. At all intervals, rats trained with delayed reinforcement had significantly lower bar-press rates than controls trained with immediate reinforcement under DRL. When reinforcement schedules were switched (DELAY groups now get IMMEDIATE and vice versa), response rates rapidly shifted to levels appropriate to the new schedule. The pre-switch results indicate that delays even as short as 1 s markedly impede the acquisition of self-stimulation behavior. The post-switch results suggest that delay of reinforcement, like stimulation intensity, may determine the strength of hypothalamic reinforcement and hence final levels of performance.     

Fos expression in the prefrontal cortex and ventral striatum after exposure to a free-operant timing schedule

It has been proposed that cortico-striato-thalamo-cortical circuits that incorporate the prefrontal cortex and corpus striatum regulate interval timing behaviour. In the present experiment regional Fos expression was compared between rats trained under an immediate timing schedule, the free-operant psychophysical procedure (FOPP), which entails temporally regulated switching between two operanda, and a yoked variable-interval (VI) schedule matched to the timing task for food deprivation level, reinforcement rate and overall response rate. The density of Fos-positive neurones (countsmm(-2)) in the orbital prefrontal cortex (OPFC) and the shell of the nucleus accumbens (AcbS) was greater in rats exposed to the FOPP than in rats exposed to the VI schedule, suggesting a greater activation of these areas during the performance of the former task. The enhancement of Fos expression in the OPFC is consistent with previous findings with both immediate and retrospective timing schedules. Enhanced Fos expression in the AcbS was previously found in retrospective timing schedules based on conditional discrimination tasks, but not in a single-operandum immediate timing schedule, the fixed-interval peak procedure. It is suggested that the ventral striatum may be engaged during performance on timing schedules that entail operant choice, irrespective of whether they belong to the immediate or retrospective categories.