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PubMed1975

Concurrent second-order schedules of reinforcement.

Responses on one key (the main key) of a two-key chamber produced food according to a second-order variable-interval schedule with fixed-interval schedule components. A response on a second key (the changeover key) alternated colors on the main key and provided a second independent second-order variable-interval schedule with fixed-interval components. The fixed-interval component on one variable-interval schedule was held constant at 8 sec, while the fixed interval on the other variable-interval schedule was varied from 0 to 32 sec. Under some conditions, a brief stimulus terminated each fixed interval and generated fixed-interval patterns; in other conditions, the brief stimulus was omitted. Relative response rate and relative time deviated substantially from scheduled relative reinforcement rate and, to a lesser extent, from obtained relative reinforcement rate under both brief-stimulus and no-stimulus conditions. Matching was observed with equal components on both schedules; with unequal components, increasingly greater proportions of time and responses than the matching relation would predict were spent on the variable-interval schedule containing the shorter component. Preference for the shorter fixed interval was typically more extreme under brief-stimulus than under no-stimulus schedules. The results limit the extension of the matching relation typically observed under simple concurrent variable-interval schedules to concurrent second-order variable-interval schedules.

Journal Article↗

PubMed1976

Relative reinforcer magnitude under a nonindependent concurrent schedule of cocaine reinforcement in rhesus monkeys.

Lever pressing by three rhesus monkeys was maintained under a two-lever concurrent schedule of cocaine reinforcement. Responding on one lever (constant-dose lever) produced a constant dose of 0.05 or 0.1 mg/kg/injection arranged according to a variable-interval 1-min schedule. Responding on the other lever (variable-dose lever) produced a comparison dose of cocaine (0.013 to 0.8 mg/kg/injection), also under a variable-interval 1-min schedule. The two variable-interval schedules were made nonindependent by arranging that the assignment of a reinforcer by one schedule inactivated the second schedule until the assigned reinforcer had been obtained. This modification ensured that the two cocaine doses were obtained with approximately equal frequency, regardless of the distribution of the subject's responding. Preference, indicated by relative response frequency on the variable-dose lever, was almost always for the larger of the doses and was a monotonic function of the comparison dose, except at the highest doses. Preferences at the highest comparison doses may have resulted from the low overall response rates exhibited at these doses. Relative response frequencies on the variable-dose lever roughly matched relative reinforcer magnitude (mg/kg/injection available on the variable-dose lever divided by the sum of mg/kg/injections available on each lever).

Animals↗

PubMed2001

Schedules of reinforcement as determinants of human causality judgments and response rates.

Experiments examined the effect of relationships between a response and an outcome on human judgments of causal effectiveness. In Experiment 1, the time between outcomes obtained on a variable ratio (VR) schedule became the intervals for a yoked variable interval (VI) schedule. Response rates were higher on the VR than on the VI schedule. In Experiment 2, the number of responses required per outcome on a VR schedule were matched to that on a master VI 20-s schedule. Both ratings of causal effectiveness and response rates were higher in the VR schedule. In Experiment 3, tandem VI fixed-ratio (FR) schedules produced higher rates and judgments than equivalent conjunctive VI FR schedule. In Experiment 4, a VI schedule with a reinforcement requirement for a short interresponse time (IRT) produced higher rates and judgments than a simple VI schedule. These results corroborate the view that schedules are a determinant of both response rates and causal judgments. Few current theories of causal judgment predict this pattern of results.

Adolescent↗

PubMed1991

Behavioral effects of ethanol inhalation in rats.

Behavioral effects of ethanol inhalation were studied on two fixed-ratio (FR) liquid-reinforced schedules and a continuous reinforcement (CRF) schedule intracranial self-stimulation (SS) in rats using the inhalational behavioral chamber designed in our laboratory. In the FR-24 schedule ethanol caused a decrease of reinforcement rate at 161 ppm and higher concentrations. In the FR-50 schedule decreases of the rate were observed at 102 ppm and 203 ppm. In the SS behavior ethanol produced a decrease in the rate of reinforcement at 603 ppm and higher concentrations. In rats of this schedule, blood ethanol concentrations were measured to be 393 micrograms/ml and 545 micrograms/ml after exposure to 600 ppm and 1200 ppm of ethanol respectively. Acute tolerance to ethanol was observed in these experiments, particularly in the FR-24 schedule. Thus ethanol inhalation could produce adequate blood concentrations so as to produce behavioral effects.

Administration, Inhalation↗

PubMed1996

Temporal control by progressive-interval schedules of reinforcement.

Progressive-interval performances are described using measures that have proven to be successful in the analysis of fixed-interval responding. Five rats were trained with schedules in which the durations of consecutive intervals increased arithmetically as each interval was completed (either 6-s or 12-s steps for different subjects). The response patterns that emerged with extended training (90 sessions) indicated that performances had come under temporal control. Postreinforcement pausing increased as a function of the interval duration, the pauses were proportional to the prevailing duration, and the likelihood of the first response within an interval increased as the interval elapsed. To assess the resistance of these patterns to disruption, subjects were trained with a schedule that generated high response rates and short pauses (variable ratio). When the progressive-interval schedule was reinstated, pausing was attenuated and rates were elevated, but performances reverted to earlier patterns with continued exposure. The results indicated that temporal control by progressive-interval schedules, although slow to develop, is similar in many respects to that for fixed-interval schedules.

Animals↗

PubMed1985

Rate-dependency and hyperactivity: methylphenidate effects on operant responding.

The two most common treatment for hyperactivity are psychopharmacological regimens and behavior therapy. Although the concurrent use of stimulant medication has been purported to enhance a child's rate of responding under a behavior management program, studies examining the interaction of the two treatments have been unable to confirm this hypothesis. The present investigation sought to examine the effects of differing levels of methylphenidate hydrochloride (Ritalin) upon operant responding with hyperactive children. After an initial drug-free training period, 10 first through fourth grade hyperactive males performed an operant key-pressing task under a mult VR 5 FI 30 sec reinforcement schedule across four randomly determined, double-blind drug conditions (placebo, 5, 10, 15 mg). Only VR responding changed significantly during medication conditions; however, rate-dependent psychostimulant effects were found within both reinforcement schedules. Discrepancies with animal rate-dependency and implications for treatment and future research are discussed. Medication effects on operant responding appear to depend upon the reinforcement schedule and dose employed.

Attention Deficit Disorder with Hyperactivity↗

PubMed1984

Interval and ratio reinforcement contingencies as determinants of methadone's effects.

The effects of methadone hydrochloride on lever pressing rats maintained under multiple fixed-interval and fixed-ratio, or multiple variable-interval and variable-ratio reinforcement schedules equated for reinforcement density were examined. Under a multiple fixed-interval, fixed-ratio schedule overall response rate was decreased during both components but was most affected under the ratio schedule. Response rate decreases were due primarily to changes in running rate rather than pause time. Under a multiple variable-interval, variable-ratio schedule, overall response rate was also decreased by methadone, with the greatest decrease again occurring during the ratio schedule. These schedule-specific methadone effects are not due to differences in reinforcement frequency. Evidence for rate-dependency with methadone is not consistent across subjects.

Animals↗

PubMed1988

Detomidine: a preliminary analysis of its duration of action in the horse by variable interval responding.

Variable interval (VI) reinforcement scheduling is a specific type of operant conditioning that is sensitive to drug effects even when overt clinical signs of the drug have diminished. Six horses were conditioned to break a light beam with a head-bobbing movement and this behaviour was reinforced with a reward of clean oats (approximately 30 mg/reinforcement). Initial training procedures included familiarisation with the behavioural equipment and fixed-ratio reinforced scheduling. To establish baseline rates of behaviour, the horses were converted to a variable interval (60 secs) reinforcement schedule and kept on this schedule for the remainder of the study. A within subjects cross-over design was used with three treatments counterbalanced with the six horses. Detomidine (40 micrograms/kg bodyweight, xylazine (1.1 mg/kg bodyweight) and saline (10 ml) were administered intravenously on Monday mornings with VI responding rates measured during a routine 30 min session each day from Monday to Friday. Responses and reinforcements were recorded and dispensed by use of an electromechanical relay system wired to an electric eye, an automatic feeder and a programming and recording system. Xylazine produced a small decrease in responding rates at 1 h post dose, while detomidine treated horses showed a dramatic decrease in responding rates after 1 h and a lingering effect at 24 h. No long range effects were seen with either treatment and all horses returned to baseline responding rates by 48 h post dose.

Animals↗

PubMed1975

Second-order schedules of token reinforcement: effects of varying the schedule of food presentation.

In the initial link of a complex schedule, one discriminative stimulus was presented and lever pressing produced tokens on fixed-ratio schedules. In the terminal link, signalled by a second discriminative stimulus, deposits of the tokens produced food. With two rats, the terminal link was presented after each sixth component schedule of token reinforcement was completed. With the other two rats, the terminal link was presented following the first component schedule completed after a fixed interval. During the terminal link, each token deposit initially produced food. The schedule of food presentation was subsequently increased such that an increasing number of token deposits in the terminal link was required for each food presentation. Rates of lever pressing in the initial link were inversely related to the schedule of food presentation in the terminal link. These results are similar to those of experiments that have varied schedules of food presentation in chained schedules. Rates and patterns of responding controlled throughout the initial link were more similar to those ordinarily controlled by second-order brief-stimulus schedules than to those controlled by comparable extended chained schedules.

Journal Article↗

PubMed1997

Effects of medial prefrontal or anterior cingulate cortex lesions on responding for cocaine under fixed-ratio and second-order schedules of reinforcement in rats.

Four experiments examined the effects of excitotoxic, axon-sparing lesions of the medial prefrontal cortex or anterior cingulate cortex in rats on responding under different schedules of intravenous cocaine self-administration and on the locomotor stimulant effects of cocaine. Experiment 1 tested the acquisition and maintenance of cocaine self-administration under a fixed ratio schedule. Rats with medial prefrontal cortex lesions showed facilitated acquisition and enhanced responding for low doses of the drug when lesions were induced before self-administration behaviour was established. Lesions of the anterior cingulate cortex did not affect cocaine self-administration. In experiment 2, rats were trained to respond under a second-order schedule of cocaine reinforcement, where responding during the fixed interval was reinforced by presentation of a cocaine-associated visual stimulus under fixed-ratio contingencies. In control rats, these schedule conditions were found to maintain high rates of responding and a scalloped pattern of responding over time. Omission of conditioned stimulus presentation during the fixed interval significantly disrupted response patterns, confirming that the stimulus served to maintain responding during the fixed interval. By contrast, rats with medial prefrontal cortex lesions showed higher rates and disrupted patterns of responding that were unchanged by stimulus omission. Rats with lesions of the anterior cingulate cortex responded at high rates throughout the fixed interval under all test conditions, indicating that the cocaine-associated stimulus did not serve to maintain temporal patterns of responding in these rats. Experiment 3 demonstrated the lack of effect of either lesion on the acquisition of responding for a non-drug reinforcer, sucrose. In experiment 4, measures of spontaneous and cocaine-induced locomotor activity revealed that rats in both lesion groups were significantly more active than controls regardless of test conditions. These data indicate that facilitated acquisition of cocaine self-administration and disrupted response patterns under second-order schedule contingencies may result from deficits in behavioural inhibition induced by medial prefrontal cortical lesions that contrast with deficits following damage to other limbic cortical regions, such as the basolateral amygdala or anterior cingulate cortex.

Animals↗

PubMed1983

Simultaneous modulation of hippocampal cholinergic activity and extinction by intraseptal muscimol.

The relationship between regulation of acetylcholine metabolism in the septal-hippocampal pathway and extinction of a food reinforced lever press response was investigated by comparing the turnover rate of acetylcholine (TRACh) in the rat hippocampus with the amount of responding during extinction after intraseptal injection of the gamma-aminobutyric acid receptor agonist muscimol. Doses (0.3-3.0 nmol) which decreased the TRACh in the hippocampus also increased the responding during extinction over that of saline controls. Responding during the continuous reinforcement schedule before extinction was also increased, but to a lesser extent. Higher doses (10-30 nmol) further decreased the TRACh in the hippocampus, decreased it in the cortex and were accompanied by irregular responding and sedation. The TRACh in the hippocampus was also measured in drug-free rats undergoing extinction after training on a continuous reinforcement or variable interval 60 sec reinforcement schedule. Although the variable interval 60 sec reinforcement schedule rats responded more than the continuous reinforcement rats during extinction, there were no differences between the TRACh in the hippocampus. The present results indicate that the decrease in the hippocampal TRACh which is produced by intraseptal muscimol is accompanied by an increase in the response rate during extinction, but that operantly induced differences in this behavior are not accompanied by detectable changes in hippocampal TRACh.

Acetylcholine↗

PubMed1998

Acquisition, maintenance and reinstatement of intravenous cocaine self-administration under a second-order schedule of reinforcement in rats: effects of conditioned cues and continuous access to cocaine.

Second order schedules of IV cocaine reinforcement in rats provide a reliable method for evaluating the effects of conditioned stimuli on cocaine-seeking behaviour, and for measuring the motivational aspects of cocaine reinforcement. In the procedure established here, each infusion of cocaine (0.25 mg/infusion) was initially made contingent on a lever press and was paired with a 20-s light conditioned stimulus (CS). When rats acquired stable rates of cocaine self-administration, the response requirement for cocaine was increased progressively to a second-order schedule of the type FI15 min(FR10:S), whereby the IV cocaine infusion was self-administered following the completion of the first FR10 responses (and CS presentation) after a 15-min fixed interval (FI) had elapsed. Evaluation of the animals' responding during the first, drug-free interval of each daily session provided a measure of cocaine-seeking behaviour, independent of other pharmacological effects of the self-administered drug. Thus, a dose-response study (dose range: 0.083, 0.25 and 0.50 mg/infusion) revealed that responding under this schedule during the initial, drug-free interval changed monotonically with dose, whereas an inverse relationship between cocaine dose and response level tended to appear during the rest of the session, after rats had self-administered the drug. Responding under this schedule was also shown to occur under the control of the CS, which had acquired conditioned reinforcing properties. Thus, a decrease in responding and an increase in the latency to initiate responding followed the omission of the CS for 3 consecutive days. In addition, extinction of cocaine-seeking behaviour was slower when contingent CS presentations occurred compared to extinction when the CS was not present. Furthermore, the reinstatement of responding for cocaine, which followed a brief period of non-contingent CS presentations, was retarded when this conditioned reinforcer had been extinguished together with cocaine. Finally, cocaine-seeking behaviour decreased markedly for the first 6 h that followed a 12-h period of continuous access to cocaine, when compared to responding 6 h after a 90-min session of limited access to the drug. Responding subsequently increased to baseline levels within 72 h. These results emphasise the utility of second-order schedules for studying drug-seeking behaviour and the importance of drug-associated cues in maintaining such responding for cocaine.

Animals↗

PubMedDate not supplied

Schedule-controlled behavior in rats exposed perinatally to the PCB mixture Aroclor 1254.

Exposure to polychlorinated biphenyls (PCBs) has been shown to detrimentally affect learning and memory in children as well as schedule-controlled behavior in experimental animals. The objective of the present series of experiments was to extend research into the effects of PCBs on behavior maintained under both short (30 s) and long (5 min) fixed-interval (FI) schedules as well as an FI 3-min with reinforcement omission. Long-Evans rats were exposed to 0 or 6 mg/kg/day Aroclor 1254 (A1254) via oral gavage from Gestation Day 6 (GD 6) through Postnatal Day 21 (PND 21). At approximately PND 90, acquisition and steady-state performance were assessed under a series of FI reinforcement schedules consisting of FI 30-s, FI 5-min, and FI 3-min with 33% of the scheduled reinforcers omitted. Performance measures included index of curvature (IOC), response rate, and postreinforcement pause (PRP). There were no effects of A1254 on the acquisition of behavior under the FI 30-s schedule. Subsequently, there was an initial decrease in response rate and IOC and an increase in PRP following the transition from FI 30-s to the FI 5-min; there were, however, no treatment-related effects on any measure. During the reinforcement-omission procedure, there was an increase in the rate of responding and a decrease in IOC and PRP following omission intervals irrespective of treatment. These data are inconsistent with previous findings and suggest that perinatal A1254 exposure in the rat does not disrupt temporally organized behavior.

Animals↗

PubMed1974

Latency and frequency of responding under discrete-trial fixed-interval schedules of reinforcement.

Pigeons' key pecking was studied under a number of discrete-trial fixed-interval schedules of food reinforcement. Discrete trials were presented by briefly illuminating the keylight repetitively throughout the interreinforcement interval. A response latency counterpart to the fixed-interval scallop was found, latency showing a gradual, negatively accelerated decrease across the interval. This latency pattern was largely invariant across changes in fixed-interval length, number of trials per interval, and maximum trial duration. Frequency of responding during early trials in the intervals varied, however, with different schedule parameters, being directly related to fixed-interval length, inversely related to number of trials, and complexly affected by conjoint variations of fixed-interval length and number of trials. Response latency thus was found to be simply related to elapsed time during the interval while response frequency was complexly determined by other factors as well.

Journal Article↗

PubMed1994

Effect of 6-hydroxydopamine lesions of the amygdala on intravenous cocaine self-administration under a progressive ratio schedule of reinforcement.

Bilateral six-hydroxydopamine (6-OHDA) lesions were placed in the amygdala of rats self-administering cocaine (1.5 mg/kg per injection i.v.) under a progressive ratio schedule of reinforcement. Post-lesion access to three doses of cocaine (1.5, 0.75 and 0.37 mg/kg per injection i.v.) revealed a lesion effect only at the highest dose. At this dose, the lesion caused a significant increase in breaking point. No change in the breaking point was produced at the lower two doses. The biochemical results show a significant reduction in dopamine and DOPAC levels within the amygdala and an increase in dopamine within the NACC. In contrast, noradrenaline and serotonin (5-HT) levels were unaffected by the lesion in any of the dissected areas. These results demonstrate that no specific effect on cocaine reinforcement was produced by 6-OHDA lesions of the amygdala. The possibility that the lesion may have attenuated the anxiogenic qualities of the high dose of cocaine is discussed.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1986

Preference for multiple versus mixed schedules of reinforcement.

Five pigeons were trained in a concurrent-chain procedure. In the initial links, equal nonindependent variable-interval schedules were available concurrently on two keys. Completing the schedule on either key led to exclusive presentation of one of two further variable-interval schedules for a fixed period of time. During these terminal links, as many reinforcers as were scheduled could be obtained. If the response producing this terminal link occurred on one key, differential stimuli signaled which variable-interval schedule had been produced. If the response producing the terminal link occurred on the other key, no such differential stimuli were available. Once the fixed period of time elapsed, the initial links were reinstated. In Experiment 1, the period of time for which the terminal links were available was always 10 s and the absolute duration of the initial links was varied. Subjects preferred the alternative leading to the multiple schedule when the initial-link duration was short, but preferred the alternative leading to the mixed schedule when the initial-link durations were longer. In Experiment 2, both the initial-link duration and the duration of the terminal links were varied. The effect of initial-link duration was identical to that in Experiment 1 and there was no systematic effect of varying the terminal-link duration.

Journal Article↗

PubMed2006

Contingency management: schedule effects.

Contingency management interventions provide reinforcement for abstaining from drugs and withhold reinforcement when drug use is detected. Previous work demonstrates that the reinforcement schedule with which reinforcement is delivered modulates the efficacy of the intervention. This pilot study explores the effects of reinforcement in methamphetamine-dependent individuals. Results suggest that schedules incorporating an increasing magnitude of reinforcement for consecutive abstinences with a reset in reinforcer magnitude for a positive drug test produce superior results.

Adolescent↗

PubMed1985

The use of response deprivation to increase the academic performance of EMR students.

This research was designed to evaluate the proposed advantages of response deprivation as the basis for establishing reinforcement schedules in applied settings. In Experiment 1, response deprivation was used to improve the cursive writing of six EMR children, using math as the contingent response. The results suggested that writing improved in schedules that produced response deprivation and when the children were given corrective feedback on their performances. In Experiment 2, reversibility of reinforcement was investigated in four EMR children working on math and writing tasks. The students were sequentially presented two reinforcement schedules that produced response deprivation; however, the instrumental and contingent responses were reversed from the first to the second. Consistent with the response deprivation view, the results indicated an increase in instrumental responding in both schedules, which suggests that reversibility of reinforcement can be achieved simply by changes in schedule requirements. In summary, the results of both experiments offered support for response deprivation as an alternative method of producing reinforcement in educational settings.

Achievement↗