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PubMed1982

Plasma corticosterone and free fatty acid responses and positive behavioral contrast.

Corticosterone and free fatty acid (FFA) responses during water-reinforced operant sessions were examined in rats subjected to reinforcement schedule shifts which may elicit frustration-induced arousal reactions. Rats were trained on a multiple VI VI-30 sec schedule that was subsequently changed to a multiple VI EXT or multiple VI VI-60 sec schedule. The rats shifted to the multiple VI EXT schedule developed positive behavioral contrast. The corticosterone levels of both groups were elevated by the first postshift session, in which the frequency of reinforcement was halved, but returned to preshift levels by the 8th postshift session, which preceded discriminative performance in the Contrast group. The FFA levels of both groups were elevated by the Multiple VI VI-30 sessions (compared to presession basal levels), but the response decreased with the halving of the reinforcement rate. The present findings were interpreted as evidence that the psychological variables associated with the acquired emotional state of frustration influence the blood concentration of corticosterone, but not FFA. The findings are consistent with such explanations of positive behavioral contrast as positive induction or release-from-inhibition. No evidence was found for a direct energizing effect of frustration to account for positive contrast.

Animals↗

PubMed1981

d-Amphetamine and phencyclidine alone and in combination: effects on fixed-ratio and interresponse-time-greater-than-t responding of rats.

The effects of three doses of d-amphetamine (0.5, 1.0, and 2.0 mg/kg) and phencyclidine (0.5, 1.0, and 2.0 mg/kg), alone and in combination, were assessed in rats performing under fixed-ratio 30 and interresponse-time-greater-than-15-sec food reinforcement schedules. When given alone, phencyclidine and d-amphetamine produced similar increases in responding under the interresponse-time-greater-than-t schedule, and decreases in responding under the fixed-ratio 30 schedule. Each drug decreased the number of reinforcers (food pellets) earned relative to control values under both schedules. The effects of the two drugs in combination were nearly always less than additive. That is, the effects of a given dose of phencyclidine and d-amphetamine together were less than an arithmetic summation of the effects of the drugs given alone.

Animals↗

PubMed1988

Naloxone and diprenorphine reduce responding for brain self-stimulation in a fixed-ratio schedule in rats.

Rats were implanted with bipolar stimulating electrodes in the midbrain-central gray area (MID-CG) and trained to lever-press for intracranial self-stimulation (ICSS) on a continuous reinforcement schedule (CRF). When behavior was stable, animals were tested in 30 min ICSS sessions following the administration of either naloxone or diprenorphine, both over the dose-range 0.001-10 mg/kg, or with vehicle. Following testing on the CRF schedule, animals were re-trained on a fixed-ratio:30 (FR:30) schedule. When behavior had again stabilized, testing with naloxone, diprenorphine and vehicle was repeated. In the CRF tests, neither naloxone nor diprenorphine had any effects on response rates over the 10,000-fold dose-range used. In the FR:30 tests, however, both drugs significantly reduced response rates at the 10 mg/kg dose, and the reduction produced by naloxone was significantly greater than that produce by diprenorphine. These results suggested that diprenorphine is qualitatively similar to naloxone in altering the rate of responding maintained by ICSS, but is less potent than the prototypical opioid antagonist in this paradigm.

Animals↗

PubMed1996

Orally delivered methadone as a reinforcer in rhesus monkeys.

Methadone usually is taken orally for drug abuse treatment in humans but oral methadone self-administration by laboratory animals has not been investigated extensively. The present study examines acquisition and maintenance of oral methadone maintained responding in four adult male rhesus monkeys. Drug solution was available from one liquid delivery system and water from a second system during daily 3-h sessions. Locations of liquids were reversed each session, and liquid (0.65 ml per delivery) was delivered according to a fixed-ratio reinforcement schedule. Initially a test for the reinforcing effects of 0.00625-0.4 mg/ml methadone solutions was carried out but a consistent preference for drug over water was not seen. To establish methadone as a reinforcer, a fading procedure was used in which responding was first maintained by solutions of methadone (0.00625-0.4 mg/ml) combined with ethanol (0.0325-2.0% w/v). Subsequently, the concentration of the ethanol in the combination was gradually reduced to zero. Methadone-maintained responding (0.4 mg/ml) persisted when ethanol was no longer present. To confirm that the drug was serving as a reinforcer, the dose was varied: (a) by changing the volume delivered while the concentration was held constant and (b) by changing the concentration of the methadone while the volume per delivery was held constant. Over a wide range of doses, deliveries of methadone solution usually exceeded deliveries of concurrently available water. Orderly relationships were observed among methadone dose, response rate, and drug intake. The study of oral self-administration of opioid drugs by nonhuman primates may be a useful strategy for the development and evaluation of new drug substitution or replacement therapies.

Administration, Oral↗

PubMed1987

Factors controlling drug reinforced behavior.

An overview is provided of factors controlling drug reinforced behavior. Drug reinforced behavior is defined, and control procedures for rigorously identifying such behavior are discussed. Factors affecting drug reinforced behavior include the drug itself, animal species, route of administration, current circumstance variables, subject's experimental history, and response consequences. Current circumstance variables concern conditions present during opportunities for drug self-administration and include such factors as stimulus control, food deprivation, drug-access conditions, and brain lesions. Response consequence variables include reinforcement schedule, punishment, drug dose, and competing reinforcers. Drug reinforced behavior is a member of a more general class of behavior, namely operant behavior. Over the last 25 years there has been a rapid increase in understanding drug reinforcement, and this pattern of expanding knowledge suggests that the high rate of progress will continue.

Animals↗

PubMed1970

Rats' preference for earned in comparison with free food.

Rats were trained to eat free food from a dish, then trained to press a lever for similar food. The free food was then presented while subjects were pressing on several reinforcement schedules. Subjects continued to press for reinforcement when one or two presses were required for reinforcement, and ate little free food. When ten presses were required for reinforcement, rats preferred free food and pressed little or not at all. It was concluded that, when work demands are not too high, rats prefer earned food to free food.

Animals↗

PubMed2006

A Delphi approach to reach consensus on primary care guidelines regarding youth violence prevention.

OBJECTIVE: Anticipatory guidance is a cornerstone of modern pediatric practice. In recognition of its importance for child well being, injury prevention counseling is a standard element of that guidance. Over the last 20 years, there has been growing recognition that intentional injury or violence is one of the leading causes of morbidity and mortality among youth. The US Surgeon General identified youth violence as a major public health issue and a top priority. Yet, only recently has the scope of injury prevention counseling been expanded to include violence. Pediatric health care providers agree that youth violence-prevention counseling should be provided, yet the number of topics available, the already lengthy list of other anticipatory guidance topics to be covered, developmental considerations, and the evidence base make the selection of an agreed-on set a considerable challenge. The purpose of this study was to systematically identify and prioritize specific counseling topics in violence prevention that could be integrated into anticipatory guidance best practice. DESIGN: A modified electronic Delphi process was used to gain consensus among 50 national multidisciplinary violence-prevention experts. Participants were unaware of other participants' identities. METHODS: The process consisted of 4 serial rounds of inquiry beginning with a broad open-ended format for the generation of anticipatory guidance and screening topics across 5 age groups (infant, toddler, school age, adolescent, and all ages). Each subsequent round narrowed the list of topics toward the development of a manageable set of essential topics for screening and counseling about positive youth development and violence prevention. RESULTS: Forty-seven unique topics were identified, spanning birth to age 21 years. Topics cover 4 broad categories (building blocks): physical safety, parent centered, child centered, and community connection. Participants placed topics into their developmentally appropriate visit-based schedule and made suggestions for an appropriate topic reinforcement schedule. The resulting schedule provides topics for introduction and reinforcement at each visit. CONCLUSIONS: The Delphi technique proved a useful approach for accessing expert opinion, for analyzing and synthesizing results, for achieving consensus, and for setting priorities among the numerous anticipatory guidance and assessment topics relevant for raising resilient, violence-free youth.

Adolescent↗

PubMed1976

Reinforcement rate and interresponse time differentiation.

Reinforcement rate and differential reinforcement of IRTs were independently manipulated to assess their relative contribution to the control of interresponse times (IRTs). Modified percentile reinforcement schedules (Platt, 1973) allowed control of reinforcement rate while longest or shortest IRTs were selectively reinforced. In the absence of differential IRT reinforcement, mean IRT decreased with increasing reinforcement rate. Compared to this small effect of reinforcement rate, reinforcement of long IRTs produced large changes in mean IRT at constant reinforcement rates. No interaction of reinforcement rate and IRT reinforcement was detected. The demonstration of large IRT changes in the absence of reinforcement-rate changes indicates the precedence of IRT reinforcement over molar reinforcement-rate correlations in the determination of IRTs in these procedures.

Journal Article↗

PubMed1998

Response acquisition with delayed reinforcement: a comparison of two-lever procedures.

Groups of 8 experimentally naive rats were exposed during 8-hr sessions to resetting delay procedures in which responses on one lever (the reinforcement lever) produced water after a delay of 8, 16, 32, or 64 s. For rats in one condition, responses on a second (no-consequences) lever had no programmed consequences. For rats in another condition, responses on a second (cancellation) lever during a delay initiated by a response on the reinforcement lever prevented delivery of the scheduled reinforcer; responses on the cancellation lever at other times had no programmed consequences. Under both conditions and at all delays, most subjects emitted more responses on the reinforcement lever than did control rats that never received water emitted on either lever. At 8-s delays, both conditions engendered substantially more responding on the reinforcement lever than on the other lever, and performance closely resembled that of immediate-reinforcement controls. At delays of 16 and 32 s, however, there was clear differential responding on the two levers under the cancellation condition but not under the other condition. When the delay was 64 s, differential responding on the two levers did not occur consistently under either condition. These findings provide strong evidence that the behavior of rats is sensitive to consequences delayed by 8, 16, and 32 s, but only equivocal evidence of such sensitivity to consequences delayed 64 s. They also indicate that acquisition depends, in part, on the measure of performance used to index it.

Animals↗

PubMed1987

Does contingent reinforcement strengthen operant behavior?

In Experiment 1, pigeons were trained to peck keys with equal food-reinforcement schedules in components that ended with either noncontingent or contingent transitions to a third component with a five-fold richer schedule. Response rates were higher in the initial component with contingent transitions, but resistance to prefeeding or extinction was not consistently greater. Experiment 2 also included noncontingent or contingent transitions to a signaled period of nonreinforcement. There was no effect of the contingency on transitions to nonreinforcement, but the difference in response rates maintained by contingent versus noncontingent transitions to the richer schedule was replicated. In addition, response rates were higher in components that preceded nonreinforcement than in components that preceded the richer schedule. However, resistance to extinction was greater for noncontingent transitions to the richer schedule than to nonreinforcement, implicating stimulus-reinforcer relations in the determination of resistance to change. Resistance to change was also somewhat greater for noncontingent than for contingent transitions to the richer schedule. The latter result, together with the results of Experiment 1 and related research, suggests that response-contingent reinforcement does not increase resistance to change.

Journal Article↗

PubMed1978

Schedule-induced drinking: entrainment by fixed- and random-interval schedule-controlled feeding.

Six underweight rats drank in a polydipsic pattern of single post-reinforcement bursts of licking before bar-pressing for subsequent food reinforcers scheduled at fixed 60-sec intervals. With a 60-sec random interval schedule they frequently oscillated between barpressing and drinking. On both schedules mean drink durations were shorter than average inter-reinforcement times, but longer drinks occurred under the fixed-interval schedule. We concluded that intermittent reinforcement entrains drinking because food plus water is more reinforcing than dry food alone, and that polydipsia develops when opportunities for drinking do not compete with opportunities for feeding.

Animals↗

PubMed2001

Sensitivity to relative reinforcer rate in concurrent schedules: independence from relative and absolute reinforcer duration.

Twelve pigeons responded on two keys under concurrent variable-interval (VI) schedules. Over several series of conditions, relative and absolute magnitudes of reinforcement were varied. Within each series, relative rate of reinforcement was varied and sensitivity of behavior ratios to reinforcer-rate ratios was assessed. When responding at both alternatives was maintained by equal-sized small reinforcers, sensitivity to variation in reinforcer-rate ratios was the same as when large reinforcers were used. This result was observed when the overall rate of reinforcement was constant over conditions, and also in another series of concurrent schedules in which one schedule was kept constant at VI ached 120 s. Similarly, reinforcer magnitude did not affect the rate at which response allocation approached asymptote within a condition. When reinforcer magnitudes differred between the two responses and reinforcer-rate ratios were varied, sensitivity of behavior allocation was unaffected although response bias favored the schedule that arranged the larger reinforcers. Analysis of absolute response rates ratio sensitivity to reinforcement occurrred on the two keys showed that this invariance of response despite changes in reinforcement interaction that were observed in absolute response rates on the constant VI 120-s schedule. Response rate on the constant VI 120-s schedule was inversely related to reinforcer rate on the varied key and the strength of this relation depended on the relative magnitude of reinforcers arranged on varied key. Independence of sensitivity to reinforcer-rate ratios from relative and absolute reinforcer magnitude is consistent with the relativity and independence assumtions of the matching law.

Animals↗

PubMed1987

Discriminative stimulus control and the effects of concurrent operants.

Discriminative-stimulus-control functions were investigated in a concurrent operant context. Variable-interval reinforcement schedules were arranged for pigeons on two response keys. One key, illuminated with a white vertical line on green background (position irrelevant), was programmed with a given schedule value across groups. For different groups of pigeons, the alternative key, illuminated with green alone, was programmed with twice, the same, or half the reinforcement frequency of the other key. Stimulus-control gradients were collected from both keys as line orientation was varied. On the green-plus-line alternative, flattest gradients were observed when twice the reinforcement frequency was concurrently programmed and the steepest were observed when equal values were concurrently programmed. Also examined were the effects of a programmed changeover delay, important in maintaining the independence of concurrent operants. The changeover delay was found to have relatively minor effects upon stimulus control, despite its typical and marked effects upon steady-state responding.

Animals↗

PubMed1986

Self-control in adult humans: variation in positive reinforcer amount and delay.

In five experiments, choice responding of female human adults was examined, as a function of variations in reinforcer amount and reinforcer delay. Experiment 1 used a discrete-trials procedure, and Experiments 2, 3, 4, and 5 used a concurrent variable-interval variable-interval schedule. Reinforcer amount and reinforcer delay were varied both separately and together. In contrast to results previously reported with pigeons, the subjects in the present experiments usually chose the larger reinforcers even when those reinforcers were delayed. Together, the results from all the experiments suggest that the subjects followed a maximization strategy in choosing reinforcers. Such behavior makes it easy to observe self-control and difficult to observe impulsiveness in traditional laboratory experiments that use adult human subjects.

Adolescent↗

PubMed1987

Effects of response deprivation on the instrumental performance of mentally retarded persons.

The accuracy of the response deprivation and probability differential hypotheses to predict reinforcement effects for mentally retarded persons was evaluated. Fifteen individuals listened to music and looked at slides in baseline phases, in reinforcement schedules and in control phases with no contingent relation between the responses. Individual analysis of instrumental responding indicated increases in those schedules that produced response deprivation but only once in schedules that did not, regardless of the probability differential between responses. The conclusions were that the response deprivation hypothesis identified the necessary and sufficient conditions for producing reinforcement for retarded persons and that this hypothesis might provide an alternative approach to reinforcer selection for retarded individuals.

Adult↗

PubMed1995

Soft commitment: self-control achieved by response persistence.

With reinforcement contingent on a single peck on either of two available keys (concurrent continuous reinforcement schedules) 4 pigeons, at 80% of free-feeding weights, preferred a smaller-sooner reinforcer (2.5 s of mixed grain preceded by a 0.5-s delay) to a larger-later reinforcer (4.5 s of mixed grain preceded by a 3.5-s delay). However, when the smaller-sooner and larger-later reinforcers were contingent on a concurrent fixed-ratio 31 schedule (the first 30 pecks distributed in any way on the two keys), all pigeons obtained the larger-later reinforcer much more often than they did when only a single peck was required. This "self-control" was achieved by beginning to peck the key leading to the larger-later reinforcer and persisting on that key until reinforcement occurred. We call this persistence "soft commitment" to distinguish it from strict commitment, in which self-control is achieved by preventing changeovers. Soft commitment also effectively achieved self-control when a brief (1-s) signal was inserted between the 30th and 31st response of the ratio and with concurrent fixed-interval 30-s schedules (rather than ratio schedules) of reinforcement. In a second experiment with the same subjects, the fixed ratio was interrupted by darkening both keys and lighting a third (center) key on which pecking was required for various fractions of the fixed-ratio count. The interruption significantly reduced self-control. When interruption was complete (30 responses on the center key followed by a single choice response), pigeons chose the smaller-sooner reinforcer as frequently as they did when only a single choice response was required.

Animals↗

PubMed1999

Intracranial self-stimulation under a progressive-ratio schedule in rats: effects of strength of stimulation, d-amphetamine, 7-OH-DPAT and haloperidol.

Progressive-ratio (PR) schedules, which have been widely used to study the reinforcing efficacy of various reinforcers (in particular IV psychostimulants), have been very seldom applied to the study of positively reinforcing electrical brain stimulation (EBS). In the present study, rats were required to emit a progressively increasing number of lever-presses (3,4,6,7,9,11,14,16, etc.) for access to successive reinforcers (periods of VTA self-stimulation). Each period of self-stimulation consisted of ten trains of square pulses of EBS; each train was available under a continuous reinforcement schedule. The number of periods of EBS earned during a session was deemed the breaking point (BP). After acquisition and stabilization of self-stimulation, a study was carried out to verify that changes in the strength of the EBS (i.e. changes in the frequency, the intensity or the pulse duration, one parameter at a time) induced changes in the BP. The effects of IP pretreatments with d-amphetamine, the dopamine D3/D2 receptor agonist 7-OH-DPAT and haloperidol were then assessed. Decreases in the strength of EBS decreased the BP. However, increasing the strength above training values resulted in minimal increases in the BP. d-Amphetamine (0.25-1 mg/kg) dose-dependently increased the BP; additionally, when the reinforcer was withheld (i.e. in conditions of extinction, with the stimulator turned off) d-amphetamine was also found to augment the BP. This might indicate that d-amphetamine preferentially potentiated the motivational (non-rewarded presses) aspects of VTA self-stimulation under this type of PR schedule. 7-OH-DPAT had biphasic effects: at low doses (0.01 and 0.03 mg/kg), it tended to decrease the BP while higher doses (1 and 3 mg/kg) robustly increased the BP. Under conditions of extinction, 7-OH-DPAT (1 mg/kg) had a tendency to increase the BP, but this effect was not statistically significant and did not approach the magnitude of effects observed with d-amphetamine. Haloperidol (0.08-0.48 mg/kg IP) dose-dependently reduced the BP, suggestive of a decrease in the reinforcing efficacy of the EBS. These results show that rats can be trained to self-administer EBS of the VTA under a PR schedule of reinforcement and that this behaviour is sensitive to disruption or potentiation of dopaminergic neurotransmission.

Animals↗

PubMed1983

Local rates of responding and reinforcement during concurrent schedules.

The literature was searched for information about the local rates of responding and reinforcement during concurrent schedules. The local rates of reinforcement obtained from the two components of a concurrent schedule were equal when a long-duration changeover delay was used and when many sessions were conducted, except when the two components provided different simple schedules. The local rates of responding were equal under some conditions, but they differed when one component provided a ratio and the other an interval schedule. Across schedules, local rates of reinforcement changed with changes in the schedule of reinforcement. Local rates of responding did not change with changes in change-over-delay duration but did with changes in the changeover ratio and with changes in the programmed rates of reinforcement. The results generally conform to the Equalizing and Melioration Principles and help to clarify current statements of the Matching Law. The results also suggest that changes in the local rates of responding and reinforcement may be orderly across schedules.

Journal Article↗