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PubMed1993

The nature of sexual reinforcement.

Sexual reinforcers are not part of a regulatory system involved in the maintenance of critical metabolic processes, they differ for males and females, they differ as a function of species and mating system, and they show ontogenetic and seasonal changes related to endocrine conditions. Exposure to a member of the opposite sex without copulation can be sufficient for sexual reinforcement. However, copulatory access is a stronger reinforcer, and copulatory opportunity can serve to enhance the reinforcing efficacy of stimulus features of a sexual partner. Conversely, under certain conditions, noncopulatory exposure serves to decrease reinforcer efficacy. Many common learning phenomena such as acquisition, extinction, discrimination learning, second-order conditioning, and latent inhibition have been demonstrated in sexual conditioning. These observations extend the generality of findings obtained with more conventional reinforcers, but the mechanisms of these effects and their gender and species specificity remain to be explored.

Animals↗
PubMed1994

Social reinforcement of operant behavior in rats: a methodological note.

An apparatus was developed to study social reinforcement in the rat. Four Long-Evans female rats were trained to press a lever via shaping, with the reinforcer being access to a castrated male rat. Responding under a fixed-ratio schedule and in extinction was also observed. Social access was found to be an effective reinforcer. When social reinforcement was compared with food reinforcement under similar conditions of deprivation and reinforcer duration, no significant differences were observed.

Animals↗
PubMed1994

Autoshaping the pigeon's gape response: acquisition and topography as a function of reinforcer type and magnitude.

The pigeon's key-pecking response is experimentally dissociable into transport (head movement) and gape (jaw movement) components. During conditioning of the key-pecking response, both components come under the control of the conditioned stimulus. To study the acquisition of gape conditioned responses and to clarify the contribution of unconditioned stimulus (reinforcer) variables to the form of the response, gape and key-contact responses were recorded during an autoshaping procedure and reinforcer properties were systematically varied. One group of 8 pigeons was food deprived and subgroups of 2 birds each were exposed to four different pellet sizes as reinforcers, each reinforcer signaled by a keylight conditioned stimulus. A second group was water deprived and received water reinforcers paired with the conditioned stimulus. Water- or food-deprived control groups received appropriate water or food reinforcers that were randomly delivered with respect to the keylight stimulus. Acquisition of the conditioned gape response frequently preceded key-contact responses, and gape conditioned responses were generally elicited at higher rates than were key contacts. The form of the conditioned gape was similar to, but not identical with, the form of the unconditioned gape. The gape component is a critical topographical feature of the conditioned key peck, a sensitive measure of conditioning during autoshaping, and an important source of the observed similarities in the form of conditioned and consummatory responses.

Animals↗
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↗
PubMed2000

Reinforcer control and human signal-detection performance.

Eight humans participated in a two-choice signal-detection task in which stimulus disparity was varied over four levels. Two procedures arranged asymmetrical numbers of reinforcers received for correct left- and right-key responses (the reinforcer ratio). The controlled procedure ensured that the obtained reinforcer ratio remained constant over changes in stimulus disparity, irrespective of subjects' performances. In the uncontrolled procedure, the asymmetrical reinforcer ratio could covary with subjects' performances. The receiver operating characteristic (ROC) patterns obtained from the controlled procedure approximated isobias functions predicted by criterion location measures of bias. The uncontrolled procedure produced variable ROC patterns that were somewhat like the isobias predictions made by likelihood ratio measures of bias; however, the obtained reinforcer ratio became more extreme as discriminability decreased. The obtained pattern of bias was directly related to the obtained reinforcer ratio. This research indicates that criterion location measures seem to be preferable indices of response bias.

Adult↗
PubMed2001

Response-independent milk delivery enhances persistence of pellet-reinforced lever pressing by rats.

If, during training, one stimulus is correlated with a higher rate of reinforcement than another, responding will be more resistant to extinction in the presence of that higher rate signal, even if many of the reinforcers have been presented independently of responding. For the present study we asked if the response-independent reinforcers must be the same as the response-dependent reinforcers to enhance the response's persistence. Twelve Long-Evans hooded rats obtained 45-mg food pellets by lever pressing (variable-interval 100-s schedules) in the presence of two discriminative stimuli (blinking vs. steady lights) that alternated every minute during daily sessions. Also, in the presence of one of the stimuli (counterbalanced across rats), the rats received additional response-independent deliveries of sweetened condensed milk (a variable-time schedule). Extinction sessions were exactly like training sessions except that neither pellets nor milk were presented. Lever pressing was more resistant to extinction in the presence of the milk-correlated stimulus when (a) the size of the milk deliveries during training (under a variable-time 30 s schedule) was 0.04 ml (vs. 0.01 ml) and (b) 120-s or 240-s blackouts separated components. Response-independent reinforcers do not have to be the same as the response-dependent reinforcers to enhance persistence.

Animals↗
PubMed2005

Rate of conditioned reinforcement affects observing rate but not resistance to change.

The effects of rate of conditioned reinforcement on the resistance to change of operant behavior have not been examined. In addition, the effects of rate of conditioned reinforcement on the rate of observing have not been adequately examined. In two experiments, a multiple schedule of observing-response procedures was used to examine the effects of rate of conditioned reinforcement on observing rates and resistance to change. In a rich component, observing responses produced a higher frequency of stimuli correlated with alternating periods of random-interval schedule primary reinforcement or extinction. In a lean component, observing responses produced similar schedule-correlated stimuli but at a lower frequency. The rate of primary reinforcement in both components was the same. In Experiment 1, a 4:1 ratio of stimulus production was arranged by the rich and lean components. In Experiment 2, the ratio of stimulus production rates was increased to 6:1. In both experiments, observing rates were higher in the rich component than in the lean component. Disruptions in observing produced by presession feeding, extinction of observing responses, and response-independent food deliveries during intercomponent intervals usually were similar in the rich and lean components. When differences in resistance to change did occur, observing tended to be more resistant to change in the lean component. If resistance to change is accepted as a more appropriate measure of response strength than absolute response rates, then the present results provide no evidence that higher rates of stimuli generally considered to function as conditioned reinforcers engender greater response strength.

Animals↗
PubMed2006

Choice between single and multiple reinforcers in concurrent-chains schedules.

Pigeons responded on concurrent-chains schedules with equal variable-interval schedules as initial links. One terminal link delivered a single reinforcer after a fixed delay, and the other terminal link delivered either three or five reinforcers, each preceded by a fixed delay. Some conditions included a postreinforcer delay after the single reinforcer to equate the total durations of the two terminal links, but other conditions did not include such a postreinforcer delay. With short initial links, preference for the single-reinforcer alternative decreased when a postreinforcer delay was present, but with long initial links, the postreinforcer delays had no significant effect on preference. In conditions with a postreinforcer delay, preference for the single-reinforcer alternative frequently switched from above 50% to below 50% as the initial links were lengthened. This pattern of results was consistent with delay-reduction theory (Squires & Fantino, 1971), but not with the contextual-choice model (Grace, 1994) or the hyperbolic value-added model (Mazur, 2001) as they have usually been applied. However, the hyperbolic value-added model could account for the results if its calculations were expanded to include reinforcers delivered in later terminal links. The implications of these findings for models of concurrent-chains performance are discussed.

Animals↗
PubMed1999

Dysphoric mood and preference for immediate versus delayed monetary reinforcement.

It has been proposed that depression is the product of deficits in self-management skills: self-monitoring, self-evaluation, and self-reinforcement. While interventions based on this theory have shown promise, some of the basic tenets upon which the theory is based lack empirical support. The present experiment tested one such tenet--the claim that depressed individuals select smaller more immediate reinforcers (an impulsive choice) at the expense of larger more delayed reinforcers (a self-control choice). Currently, empirical support for this notion is sparse and contradictory. This study addressed several methodological problems in earlier studies by creating divergent groups based on Beck Depression Inventory scores, employing a task requiring multiple responses and applying a quantitative model to determine reinforcer value. Analyses indicated no systematic difference between participants in the dysphoric and nondysphoric groups in ability to delay reinforcement. Thus, the current results provide no support for the hypothesis that the 36 dysphoric individuals were unable to delay reinforcement relative to the 21 nondysphoric individuals. Because respondents across the sample as a whole showed a self-control preference, however, the data are consistent with findings in the experimental study of choice responding with adult human subjects. Interpretations in terms of sensitivity and pseudosensitivity to the experimental contingencies are explored.

Adolescent↗
PubMed2006

Operant variability when reinforcement is delayed.

Operant responses are often weakened when delays are imposed between the responses and reinforcers. We examined what happens when delayed reinforcers were contingent upon operant response variability. Three groups of rats were rewardedfor varying their response sequences, with onegroup rewarded for high variability, another for middle, and the third for low levels. Consistent with many reports in the literature, responding slowed significantly in all groups as delays were lengthened. Consistent with other reports, large differences in variability were maintained across the three groups despite the delays. Reinforced variability appears to be relatively immune to disruption by such things as delays, response slowing, prefeeding, and noncontingent reinforcement. Furthermore, the small effects on variability depended on baseline levels: As delays lengthened, variability increased in the low group, was statistically unchanged in the middle group, and decreased in the high group, an interaction similar to that reported previously when reinforcement frequencies were lowered. Thus, variable operant responding is controlled by reinforcement contingencies, but sometimes differently than more commonly studied repetitive responding.

Animals↗
PubMed2000

A new assessment of the ability of oral ethanol to function as a reinforcing stimulus.

BACKGROUND: In animal studies, the ability of ethanol to function as a reinforcer has been described as weak to moderate. This is in contrast with the human condition, where the consumption of alcoholic beverages can result in a variety of unwanted drinking behaviors. However, when the ethanol self-administration pattern is examined, animal studies over the last several years indicate that the ability of ethanol presentation to maintain behavior may be greater than originally assumed. METHODS: We reevaluated the ability of ethanol to function as a reinforcing stimulus in two paradigms by using an analysis of drinking bout characteristics. Data from previous studies that employed two self-administration models were analyzed. With the "dipper" model, small amounts of ethanol are presented after each completion of a response requirement; with the "sipper" model, the animal is allowed access to a drinking tube that contains ethanol for an extended period after completing a single response requirement. For both models, the consumption pattern could be characterized as occurring in a bout. Each drinking bout was divided into runs within the bout, and run rates and size were analyzed. As well, in the sipper model, the data on response requirement size were reviewed to demonstrate the ability of ethanol presentation to maintain high levels of responding in this model. RESULTS: From this assessment, we suggest that ethanol presentation in non-food- or non-water-restricted rats is as reinforcing as many other stimuli generally considered to be strong reinforcers (i.e., food in food-restricted rats). Using run size, we demonstrated that intake control appears to be regulated by shifts in run size during the bout and not run rate. CONCLUSIONS: Assessment of the pattern of ethanol consummatory bouts and the behaviors that precede them is critical in understanding how ethanol functions as a reinforcer. By using a drinking pattern analysis, the shifts in the momentary salience of the ethanol stimulus can be evaluated in these animal models. In addition, the separation of responding required to gain access to ethanol from consumption of ethanol demonstrated that ethanol presentation in this procedure can be a strong reinforcer for rats.

Alcohol Drinking↗
PubMed2000

A behavioral economic analysis of concurrent ethanol- and water-reinforced responding in different preference conditions.

BACKGROUND: The reinforcing properties of orally self-administered drugs have been evaluated by using choice procedures. The preference for the drug over a nondrug alternative has indicated that the drug has greater value than the nondrug alternative as a reinforcer at some drug concentrations. However, at large drug concentrations, the fluid deliveries of the drug may be equal to or less than those of the nondrug alternative, whereas the actual drug intake (milligrams per kilogram of body weight) may continue to increase. In this study, we used behavioral economics to evaluate the reinforcing strength of ethanol in conditions where baseline ethanol fluid deliveries were greater than, equal to, or less than those of the concurrently available water. METHODS: Four male rhesus monkeys were allowed access to ethanol (2%, 8%, or 32%) and water for 2 hr/day under a fixed ratio (FR) 4 reinforcement schedule. At each ethanol concentration, the FR for both fluids was gradually increased to FR 64. RESULTS: During the FR 4 schedule, the fluid deliveries of ethanol at 2%, 8%, and 32% were greater than, equal to, and less than those of water, respectively. When the FR was increased at 2% ethanol, fluid deliveries and responding decreased for both the ethanol and water. When the FR was increased at 8% ethanol, water fluid deliveries and responding decreased more rapidly than did those of ethanol. When the FR was increased at 32% ethanol, the ethanol fluid deliveries remained the same across all FRs, whereas water fluid deliveries decreased rapidly. At 8% and 32% ethanol, the responding for ethanol, relative to water, increased dramatically. CONCLUSIONS: In behavioral economic terms, demand for ethanol was more inelastic regardless of whether the ethanol or water maintained more absolute fluid deliveries at baseline FRs. Therefore, researchers should examine the reinforcing effects of ethanol in a variety of concentration and schedule conditions rather than drawing inferences regarding reinforcing effects simply based on a preference measure.

Alcohol Drinking↗
PubMed2000

Ethanol reinforcement in nondeprived mice: effects of abstinence and naltrexone.

BACKGROUND: Operant experiments which indicate that ethanol can serve as a reinforcer to maintain lever responding during limited periods of access have not been conducted on non-food-deprived mice, as they have for rats and monkeys. Furthermore, there are no reports of the effects of chronic ethanol and subsequent abstinence on ethanol reward in mice. Finally, although naltrexone reduces responding for ethanol in food-deprived mice, the effects of the drug on ethanol reward for non-food-deprived mice have not been reported. METHODS: In three experiments, lever responding for ethanol (10-12%) was established in C57BL/6 (B6) mice by using either sucrose or saccharin fading procedures commonly used for rats. Experiment 1 examined both appetitive and consummatory responses while sucrose was faded from the ethanol solutions. Experiment 2 examined lever responding and ethanol intake (1) during saccharin fading; (2) when reinforcement schedules, reward availability, and primary conditioned reinforcers were manipulated; and (3) when mice were allowed chronic ethanol consumption followed by forced abstinence. Experiment 3 examined the effects of low doses of naltrexone on ethanol reward. RESULTS: Lever responding for ethanol can be established in non-food-deprived mice with the sucrose and saccharin fading procedures commonly used for rats. Lever responses increased with decreases in the reinforcer and increases in schedule demand, which indicated the reward value of the ethanol solution. Removal of ethanol from the solution reduced consumption with no change in the appetitive, instrumental response, which indicated that the two responses were under control of different stimuli, perhaps mediated by different neural mechanisms. Forced abstinence after chronic ethanol exposure increased responding for the drug, which suggested increased reward value. Naltrexone reduced responding as previously reported for food-deprived B6 mice. CONCLUSIONS: Ethanol appears to serve as a reinforcer for non-food-deprived or non-water-deprived B6 mice. Its reinforcing effects are increased by forced abstinence after chronic exposure and are decreased by naltrexone.

Animals↗
PubMed1975

Classical skin conductance response conditioning: effects of intermittent reinforcement and information about schedule contingencies.

Skin conductance responses were differentially conditioned using reinforcement schedules of 25%, 50%, 75%, and 100%, manipulated between subjects. Half of the subjects were informed about schedule contingencies, and half were uninformed. The interstimulus interval was 6 sec. Discrimination of first-interval responses (1.0-3.5 sec after conditioned stimulus [CS] onset) by informed subjects did not vary with the ratio variable, but that by uninformed subjects improved with increasing reinforcement ratio because of diminished response levels to the nonreinforced CS (CS-). Discrimination of second-interval responses (3.6-7.0 sec after CS onset) improved as a function of increasing reinforcement ratio because of elevated response levels to the reinforced CS (CS+), but the effect was not persistent across trials in informed subjects. Performance in the first and second intervals did not reflect sequential increments and decrements as a function of reinforced and nonreinforced trials. Third-interval responses (7.1-9.9 sec after CS on nonreinforced trials) were not affected by schedule manipulations, but unconditioned responses diminished with increasing reinforcement ratio. Information about schedule contingencies led to superior discrimination of first-, second-, and third-interval responses and to suppression of unconditioned responses.

Adolescent↗
PubMedDate not supplied

[Probabilistic reinforcement and neurotic breakdown in unrestrained dogs].

The substitution of a constant reinforcement for a random one with a probability of 0.5 in experiments on two dogs with a simple motor stereotype was attended with nervous breakdowns with motor excitation, inadequate orienting reactions or passive-defensive behaviour. The change in the probability of reinforcement from 0.5 to 0.3 had a positive effect in experiments on one dog, while in the other it developed drowsiness. In two other dogs with a complicated stereotype, the change in the mode of reinforcement was attended with a peculiar preventive effect of probabilistic, but ordered reinforcement in experimental surroundings, including signals with a probabilistic random reinforcement as well. In this case the dogs displayed primarily signs of emotional stress only. Behaviour was somewhat disturbed in one animal only when testing signals with a probabilistic random reinforcement.

Animals↗
PubMedDate not supplied

[The dependence of hippocampal electrical activity on the probability of the reinforcement of a conditioned food stimulus].

In three dogs the dynamics was studied of changes in the number of instrumental motor reactions, the heart rate and the hippocampus theta rhythm was studied at the change of constant reinforcement to various regimes of probable reinforcement of alimentary conditioned stimulus. At 70 and 50% levels of the reinforcement the instrumental reflex appeared in response to all presentations of the signal stimulus. The greatest decrease in the number of reactions took place at 5% probability. The heart rate both in the intersignal period and at getting of empty feeder depended on the used probability of reinforcement and individual characteristics of animals. The frequency of the theta rhythm in all dogs was the highest at the 30% level and the lowest values were found at the 5% level of reinforcement. The obtained facts testify once more to complex genesis of emotional excitation, the value of which depends both on informational (uncertainty) and motivational (significance of reinforcement) factors.

Animals↗
PubMed1990

Expectancies of reinforcer location and quality as cues for a conditional discrimination in pigeons.

Experiment 1 demonstrated that reliably correlating different reinforcer locations (top vs. bottom) with sample stimuli markedly enhanced the performance of White Carneaux pigeons in a spatial conditional discrimination. This differential outcome effect was more evident at longer retention intervals. In Experiment 2, pigeons were given the opportunity to learn about two redundant reinforcer features--location (top vs. bottom) and quality (grain vs. chow). Which reinforcer feature exerted control over choosing depended on task structure. In the congruent task, where pecks to the top key operated the top feeder and pecks to the bottom key operated the bottom feeder, reinforcer location exerted predominant control. In the incongruent task, where pecks to the top key operated the bottom feeder and vice versa, reinforcer quality exerted exclusive control. These results have implications for the nature of reinforcer representations in instrumental learning.

Animals↗
PubMed1988

What is the role of reinforcement in early language acquisition?

Monolingual American and Mexican 2- and 3-year-old children were exposed to a foreign language in a naturalistic but controlled environment. Children were randomly assigned to 2 groups. 1 group was differentially reinforced throughout the study for the use of foreign vocabulary. The control group was first reinforced nondifferentially for use of the native language or the foreign language and later was switched to differential reinforcement for the foreign language. Frequencies of spontaneous foreign word production and other verbal responses were computed, and formal assessments of comprehension and production of the foreign words were conducted. Differential reinforcement resulted in accelerating frequencies of spontaneous foreign language use and better performance on both comprehension and production tests. Under nondifferential reinforcement, rates of spontaneous foreign language use were low and static. Results are interpreted as evidence that the acquisition of expressive vocabulary is a function of socially mediated reinforcement.

Child, Preschool↗