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PubMed2000

Choice, changing over, and reinforcement delays.

In three experiments, pigeons were used to examine the independent effects of two normally confounded delays to reinforcement associated with changing between concurrently available variable-interval schedules of reinforcement. In Experiments 1 and 2, combinations of changeover-delay durations and fixed-interval travel requirements were arranged in a changeover-key procedure. The delay from a changeover-produced stimulus change to a reinforcer was varied while the delay between the last response on one alternative and a reinforcer on the other (the total obtained delay) was held constant. Changeover rates decreased as a negative power function of the total obtained delay. The delay between a changeover-produced stimulus change had a small and inconsistent effect on changeover rates. In Experiment 3, changeover delays and fixed-interval travel requirements were arranged independently. Changeover rates decreased as a negative power function of the total obtained delay despite variations in the delay from a change in stimulus conditions to a reinforcer. Periods of high-rate responding following a changeover, however, were higher near the end of the delay from a change in stimulus conditions to a reinforcer. The results of these experiments suggest that the effects of changeover delays and travel requirements primarily result from changes in the delay between a response at one alternative and a reinforcer at the other, but the pattern of responding immediately after a changeover depends on the delay from a changeover-produced change in stimulus conditions to a reinforcer.

Animals↗
PubMed2002

Preference and resistance to change with constant- and variable-duration terminal links: independence of reinforcement rate and magnitude.

Pigeons responded in a three-component multiple concurrent-chains procedure in which the variable-interval reinforcement schedules were the same across components but magnitudes differed across components. The terminal links were arranged either as a variable delay followed by presentation of a reinforcer ("variable duration") or as a fixed period of access to the schedule during which a variable number of reinforcers could be earned ("constant duration"). Relative reinforcement rate was varied parametrically across both types of conditions. After baseline training in each condition, resistance to change of terminal-link responding was assessed by delivering food during the initial links according to a variable-time schedule. Both preference and resistance to change were more sensitive to reinforcement-rate differences in the constant-duration conditions. Sensitivities of preference and resistance to change to relative reinforcement rate did not change depending on relative reinforcement magnitude. Taken together, these results confirm and extend those of prior studies, and suggest that reinforcement rate and magnitude combine additively to determine preference and resistance to change. A single structural relation linking preference and resistance to change describes all the data from this and several related studies.

Animals↗
PubMed2004

Within-session delay-of-reinforcement gradients.

Within-session delay-of-reinforcement gradients were generated with pigeons by progressively increasing delays to reinforcement within each session. In Experiment 1, the effects of imposing progressive delays on variable-interval and fixed-interval schedules were investigated while controlling for simultaneous decreases in reinforcer rate across the session via a within-subject yoked-control procedure. Rate of key pecking decreased as a negatively decelerated function of delay of reinforcement within a session. These rate decreases were greater than those during a yoked-interval session in which the rate of immediate reinforcement decreased at the same rate as it did under the progressive-delay procedure. In Experiment 2, delay-of-reinforcement gradients were shallower when the progressive delay intervals were signaled by a blackout than when they were unsignaled. The delay gradients obtained in each experiment were similar to those generated under conditions in which different delays of reinforcement are imposed across blocks of sessions. The present procedure offers a technique for rapidly generating delay-of-reinforcement gradients that might serve as baselines for assessing the effects of other behavioral and pharmacological variables.

Animals↗
PubMed2005

Unsignaled delay of reinforcement, relative time, and resistance to change.

Two experiments with pigeons examined the effects of unsignaled, nonresetting delays of reinforcement on responding maintained by different reinforcement rates. In Experiment 1, 3-s unsignaled delays were introduced into each component of a multiple variable-interval (VI) 15-s VI 90-s VI 540-s schedule. When considered as a proportion of the preceding immediate reinforcement baseline, responding was decreased similarly for the three multiple-schedule components in both the first six and last six sessions of exposure to the delay. In addition, the relation between response rates and reinforcement rates was altered such that both parameters of the single-response version of the matching law (i.e., k and Re) were decreased. Experiment 2 examined the effects of unsignaled delays ranging from 0.5 s to 8.0 s on responding maintained by a multiple VI 20-s VI 120-s schedule of reinforcement. Response rates in both components increased with brief unsignaled delays and decreased with longer delays. As in Experiment 1, response rates as a proportion of baseline were affected similarly for the two components in both the first six and last six sessions of exposure to the delay. Unlike delays imposed between two stimulus events, the effects of delays between responses and reinforcers do not appear to be attenuated when the average time between reinforcers is longer. In addition, the disruptions produced by unsignaled delays appear to be inconsistent with the general finding that responding maintained by higher rates of reinforcement is less resistant to change.

Animals↗
PubMed2006

Feedback functions, optimization, and the relation of response rate to reinforcer rate.

The present experiment arranged a series of inverted U-shaped feedback functions relating reinforcer rate to response rate to test whether responding was consistent with an optimization account or with a one-to-one relation of response rate to reinforcer rate such as linear system theory's rate equation or Herrnstein's hyperbola. Reinforcer rate was arranged according to a quadratic equation with a maximum at a unique response rate. The experiment consisted of two phases, during which 6 Long Evans rats lever pressed for food. In the first phase of the experiment, the rats responded on six fixed-interval-plus-quadratic-feedback schedules, and in the second phase the rats responded on three variable-interval-plus-quadratic-feedback schedules. Responding in both phases was inconsistent with a one-to-one relation of response rate to reinforcer rate. Instead, different response rates were obtained at equivalent reinforcer rates. Responding did vary directly with the vertex of the feedback function in both phases, a finding consistent with optimization of reinforcer rate. The present results suggest that the feedback function relating reinforcer rate to response rate imposed by a reinforcement schedule can be an important determinant of behavior. Furthermore, the present experiment illustrates the benefit of arranging feedback functions to investigate assumptions about the variables that control schedule performance.

Animals↗
PubMed2006

Matching and conditioned reinforcement rate.

Attempts to examine the effects of variations in relative conditioned reinforcement rate on choice have been confounded by changes in rates of primary reinforcement or changes in the value of the conditioned reinforcer. To avoid these problems, this experiment used concurrent observing responses to examine sensitivity of choice to relative conditioned reinforcement rate. In the absence of observing responses, unsignaled periods of food delivery on a variable-interval 90-s schedule alternated with extinction on a center key (i.e., a mixed schedule was in effect). Two concurrently available observing responses produced 15-s access to a stimulus differentially associated with the schedule of food delivery (S+). The relative rate of S+ deliveries arranged by independent variable-interval schedules for the two observing responses varied across conditions. The relation between the ratio of observing responses and the ratio of S+ deliveries was well described by the generalized matching law, despite the absence of changes in the rate of food delivery. In addition, the value of the S+ deliveries likely remained constant across conditions because the ratio of S+ to mixed schedule food deliveries remained constant. Assuming that S+ deliveries serve as conditioned reinforcers, these findings are consistent with the functional similarity between primary and conditioned reinforcers suggested by general choice theories based on the concatenated matching law (e.g., contextual choice and hyperbolic value-added models). These findings are inconsistent with delay reduction theory, which has no terms for the effects of rate of conditioned reinforcement in the absence of changes in rate of primary reinforcement.

Animals↗
PubMed2005

Remembering: the role of extraneous reinforcement.

In two experiments, pigeons' responding on an extraneous task was explicitly reinforced during delayed matching-to-sample trials. In Experiment 1, red or green sample stimuli were followed by retention intervals of 0.2, 1, 4, or 12 sec, during which pecks to a white center key were reinforced with 2.5-sec access to wheat according to extinction, variable-interval 30-sec, and variable-interval 15-sec schedules in different conditions. A proportion of .2, .5, .7, or .9 of subsequent red or green choice responses that matched the sample were reinforced with 3-sec access to wheat. The result was that increasing center key reinforcement, or reducing reinforcer probability, lowered overall accuracy. Initial discriminability fell, but with no change in the rate of forgetting. In Experiment 2, initial discriminability was affected by extraneous reinforcers that were contingent on center key pecking, but not by noncontingent reinforcers. A plausible conclusion is that initial discriminability decreases when reinforcers strengthen competing behaviors.

Animals↗
PubMed2004

Acquisition with partial and continuous reinforcement in pigeon autoshaping.

Contemporary time accumulation models make the unique prediction that acquisition of a conditioned response will be equally rapid with partial and continuous reinforcement, if the time between conditioned stimuli is held constant. To investigate this, acquisition of conditioned responding was examined in pigeon autoshaping under conditions of 100% and 25% reinforcement, holding intertrial interval constant. Contrary to what was predicted, evidence for slowed acquisition in partially reinforced animals was observed with several response measures. However, asymptotic performance was superior with 25% reinforcement. A switching of reinforcement contingencies after initial acquisition did not immediately affect responding. After further sessions, partial reinforcement augmented responding, whereas continuous reinforcement did not, irrespective of an animal's reinforcement history. Subsequent training with a novel stimulus maintained the response patterns. These acquisition results generally support associative, rather than time accumulation, accounts of conditioning.

Animals↗
PubMedDate not supplied

What is a "schedule of reinforcement"?

Several ambiguities in the present terminology of behavior theory obscure some important theoretical assumptions and experimental details in current research. Left unclarified, such ambiguities impede the accurate analysis of laboratory procedures, and prevent reliable communication among researchers. This paper focuses on the term "schedule of reinforcement". It points out that two distinguishable operational rules are implicated in the term: in the case where reinforcement is of the so-called response contingent type, the "schedule" is really a rule to identify the response to be reinforced; in the case of non-contingent reinforcement, the "schedule" is truly a rule for delivery of reinforcement. Other terminological ambiguities that are encountered in a discussion of this term include "reinforcement" and "intermittency." A resolution of these problems will necessarily involve the procedures of non-contingent reinforcement, and the parameter of reinforcement probability.

Conditioning, Classical↗
PubMed1990

Performance on ratio and interval schedules with matched reinforcement rates.

In the first study, rats were trained to pull a chain on a schedule (RPI) that regulates the probability of reinforcement to maintain a constant average reinforcement rate without differentially reinforcing long inter-response times (IRTs). Although the response rate was sensitive to the overall rate of reinforcement, performance was unaffected by variations between 1 and 50 in the IRT memory size used in programming the schedule. In the second study, two groups of animals performed on either a random-interval (RI) schedule or a RPI schedule, with reinforcement rates determined by those generated by a third group performing on a random ratio (RR) 20 schedule. The RI group responded at a lower rate than the RPI group, which, in turn, responded at a lower rate than the RR group, even though the three groups experienced comparable rates of reinforcement. The fact that the RPI group responded at a lower rate than the RR group suggests that the standard response rate difference observed between ratio and interval schedules, which have been matched for reinforcement rate, cannot be attributed solely to the fact that conventional interval schedules differentially reinforce long IRTs.

Animals↗
PubMed1990

Effect of reinforcer devaluation on discriminative control of instrumental behavior.

Two experiments examined the effect of reinforcer devaluation on the ability of a discriminative stimulus (Sd) to control instrumental behavior in Sprague-Dawley rats. In Experiment 1 reinforcer devaluation reduced, but did not eliminate, the ability of the Sd to control performance of the original response and to transfer its control to a new response trained with the same reinforcer. The effect of devaluation was more complete in Experiment 2, in which the reinforcer was delivered directly into the oral cavity. However, retraining the response with a different reinforcer partially restored the ability of the Sd to control performance of that response. These results suggest that an Sd may not augment its trained responses when the reinforcer has been completely devalued but may promote responses with which it shares a reinforcer, as long as those responses are associated with some reinforcer that retains its value. The implications of these results for the way that discriminative stimuli control instrumental behavior are discussed.

Animals↗
PubMed1989

Selective 5-hydroxytryptamine2 antagonists have antidepressant-like effects on differential-reinforcement-of-low-rate 72-second schedule.

The effects of eleven 5-hydroxytryptamine antagonists with varying selectivity for the 5-hydroxytryptamine2 (5-HT2) relative to the 5-HT1 binding site were assessed in rats responding under a differential-reinforcement-of-low rate 72-sec (DRL 72-s) schedule of reinforcement. Three drugs with a 1000-fold selectivity for the 5-HT2 binding site (ketanserin, ritanserin, pipamperone) increased the reinforcement rate and decreased the response rate similar to antidepressant drugs. The two drugs with roughly the same affinity for both 5-HT1 and 5-HT2 binding sites (methysergide and metergoline) did not increase the reinforcement rate. The maximal increase in the reinforcement rate after 5-HT antagonist administration was positively correlated with the selectivity of the 5-HT antagonists for the 5-HT2 versus the 5-HT1 binding site. The increase in the reinforcement rate after administration of 5-HT antagonists was not correlated with the affinity of the 5-HT antagonists for the alpha-1 adrenergic, alpha-2 adrenergic, histamine-1 or dopamine-2 receptors. The 1000-fold selective 5-HT2 antagonist xylamidine, which does not pass the blood-brain barrier, did not increase the reinforcement rate or decrease the response rate. Thus, selective antagonism of central 5-HT2 relative to 5-HT1 receptors results in antidepressant-like effects on the DRL 72-s schedule. Furthermore, the specificity of the DRL 72-s schedule as a screen for antidepressant drugs was strengthened by the observation that the alpha-1 adrenergic antagonist, prazosin, did not increase the reinforcement rate despite significant decreases in the response rate.

Animals↗
PubMed1989

Evidence for involvement of 5-hydroxytryptamine1 receptors in antidepressant-like drug effects on differential-reinforcement-of-low-rate 72-second behavior.

Previous work in this laboratory has suggested that antagonist action of 5-hydroxytryptamine2 (5-HT2) receptors and agonist action of 5-HT1 receptors results in antidepressant-like effects (increased reinforcement rate and decreased response rate) in rats performing under the differential-reinforcement-of-low-rate 72-sec schedule (DRL 72-s) of reinforcement. Serotonergic mediation of antidepressant drug effects on DRL 72-s behavior was assessed with a series of 5-HT agonists, and blockade of the effects of the antidepressant drugs clorgyline and fluoxetine (which presumably indirectly stimulate 5-HT1 receptors) was attempted in separate experiments with the 5-HT1 and 5-HT2 antagonist methysergide and the 5-HT neurotoxin 5,7-dihydroxytryptamine. Direct 5-HT1A agonists 8-hydroxy-2-(di-n-propylamino)tetralin and 5-methoxy-N,N-dimethyltryptamine and the 5-HT precursor 5-hydroxytryptophan all increased the reinforcement rate. The 5-HT1B and 5-HT1C agonists m-chlorophenylpiperazine and 1-(m-trifluoromethylphenyl)piperazine did not increase the reinforcement rate. The 5-HT2 agonist and 5-HT3 antagonist quipazine also did not increase the reinforcement rate. The monoamine oxidase inhibitor clorgyline and the 5-HT uptake inhibitor fluoxetine increased the reinforcement rate and decreased the response rate as seen with other antidepressant drugs on the DRL 72-s schedule. Methysergide antagonized the reinforcement rate increasing effects of both clorgyline and fluoxetine. Depletion of brain 5-HT with i.v.t. 5,7-dihydroxytryptamine blocked the antidepressant-like effects of clorgyline. These results suggest that central 5-HT1A receptors are involved in mediating the antidepressant-like effects of some drugs on DRL 72-s behavior. These results provide evidence that stimulation of 5-HT1A receptors and antagonism of 5-HT2 receptors lead to an antidepressant-like effect on the DRL 72-s schedule and implies that these two receptors may be important in mediating clinical drug effects in depression.

Animals↗
PubMed1981

Effects of differential reinforcement expectancies on successive matching-to-sample performance in pigeons.

A series of experiments employed a symbolic variant of Konorski's delayed successive matching-to-sample task in order to determine whether differential reinforcement expectancies affect discriminative responding. One of two sample stimuli (S1 or S2) was followed, after a delay (0, 5, or 10 sec), by one of two test stimuli (T1 or T2). Pigeons' key pecking during test periods could produce food only on S1-T1 and S2-T2 (positive) trials; nonreinforcement invariably occurred on S1-T2 and S2-T1 (negative) trials. Differential reinforcement was scheduled by following the two positive trial sequences with different probabilities of reinforcement (.2 and 1.0); nondifferential reinforcement was scheduled by following the two positive trial sequences with a single, intermediate probability of reinforcement. (.6). Subjects given differential reinforcement acquired the conditional discriminaton more rapidly and reached higher terminal levels of performance than nondifferential controls (Experiment 1). Moreover, the magnitude of these differences increased as the delay between sample and test stimuli was lengthened. Reversing the probabilities of reinforcement in the differential problem produced a substantial and durable disruption of conditional discrimination performance (Experiment 2). The same general pattern of results was obtained when differential sample key pecking was eliminated (Experiment 3). These results can be parsimoniously interpreted by postulating the existence of learned reinforcement expectancies, and they detract from the merits of trace theory as a complete account of animal memory.

Animals↗
PubMed1997

Ethanol-reinforced responding by AA and ANA rats following the sucrose-substitution initiation procedure.

Ethanol-reinforced responding was initiated in male AA and ANA rats using the sucrose-substitution procedure. Before the initiation procedure, a homecage, two-bottle preference test was conducted. The rats were then trained to respond on an Fixed-Ratio 1 schedule with sucrose reinforcement. Over sessions, ethanol was added gradually to the sucrose solution as the concentration of sucrose was reduced until 10% ethanol (v/v) alone functioned as the reinforcer for lever pressing. The schedule of reinforcement was then increased to Fixed-Ratio 4. Next, the ethanol concentration presented as the reinforcer was increased over weeks to 15%, 20%, 30%, and then returned to 10%. A second homecage test was then performed. The results showed that the AA and ANA lines differed significantly on preference and intake (g/kg) during the homecage preference tests. There was a significant increase in preference during the second homecage test. During sucrose substitution, initial large differences in responding were observed between the lines. When the ethanol concentration was increased, intake (grams per kilogram) increased for the AA line but not for the ANA line. These effects were a function of no change in responding by the AA rats as concentration was increased and a decrease in responding by the ANA rats at the higher concentrations (20% and 30%). Taken together, data indicate that ethanol can function as a positive reinforcer for the behavior of AA and ANA rats. Even though 10% ethanol functioned as a reinforcer similarly for the two lines, ethanol intake in the AA line was significantly greater at the higher concentrations of ethanol, suggesting that ethanol functioned as a qualitatively different reinforcer for the AA rats, compared with the ANA rats.

Alcohol Drinking↗
PubMed1976

Responsiveness of delinquents and non-delinquents to social reinforcement.

A series of six experiments, involving 198 subjects, examined the hypothesis that delinquents are less responsive than non-delinquents to social reinforcement and punishment. The hypothesis received support (a) using two different experimental techniques, one in which the subjects' judgements of autokinetic movement were modified and one using the Taffel (1955) verbal conditioning paradigm; (b) with the female adult administering the reinforcement and with a peer; (c) when the contingent social cues were rewarding (Good or Fine) and when they were punishing ('No'). The hypothesis was not supported when the verbal reinforcement was varied. Control studies using no reinforcement and money reinforcement indicated that the social reinforcement did indeed have a specific reinforcement effect and that delinquents did not show a general learning deficiency.

Adolescent↗
PubMed1977

The influence of behavior preceding a reinforced response on behavior change in the classroom.

The influence of behavior that immediately precedes a reinforced target response on the effectiveness of a reinforcement contingency was examined in two experiments with mentally retarded children in a special-education classroom. Two reinforcement schedules were examined in each experiment. For each schedule, a prespecified period of attentive behavior served as the target response. The schedules differed in whether inattentive or attentive behavior was required immediately to precede the target response. These schedules were examined with one child in a simultaneous treatment design using praise as the reinforcer (Experiment I), and with two children in separate reversal designs using tokens as the reinforcer (Experiment II). While attentive behavior increased under each schedule, the increase was greater when attentive rather than inattentive behavior preceded the reinforced response. The results indicated that the effect of a contingency may be determined not only by the specific response reinforced but also by the behavior that immediately precedes that response.

Attention↗
PubMed1964

EFFECTS OF A DRL CONTINGENCY ADDED TO A FIXED-INTERVAL REINFORCEMENT SCHEDULE.

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

Animals↗