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PubMed1963

Random interval schedules of reinforcement.

A method for generating a reinforcement schedule that closely approximates idealized VI schedules in which reinforcement assignments occur randomly in time (RI schedules) is described. Response rates of pigeons exposed for 20 sessions to this schedule appeared very similar to response rates characteristic of arithmetic series VIs. The distribution function describing these schedules was derived and its relations to other VI distributions, as well as to FI and random ratio (RR) were shown.

Journal Article↗
PubMed1968

A quantitative analysis of the responding maintained by interval schedules of reinforcement.

Interval schedules of reinforcement maintained pigeons' key-pecking in six experiments. Each schedule was specified in terms of mean interval, which determined the maximum rate of reinforcement possible, and distribution of intervals, which ranged from many-valued (variable-interval) to single-valued (fixed-interval). In Exp. 1, the relative durations of a sequence of intervals from an arithmetic progression were held constant while the mean interval was varied. Rate of responding was a monotonically increasing, negatively accelerated function of rate of reinforcement over a range from 8.4 to 300 reinforcements per hour. The rate of responding also increased as time passed within the individual intervals of a given schedule. In Exp. 2 and 3, several variable-interval schedules made up of different sequences of intervals were examined. In each schedule, the rate of responding at a particular time within an interval was shown to depend at least in part on the local rate of reinforcement at that time, derived from a measure of the probability of reinforcement at that time and the proximity of potential reinforcements at other times. The functional relationship between rate of responding and rate of reinforcement at different times within the intervals of a single schedule was similar to that obtained across different schedules in Exp. 1. Experiments 4, 5, and 6 examined fixed-interval and two-valued (mixed fixed-interval fixed-interval) schedules, and demonstrated that reinforcement at one time in an interval had substantial effects on responding maintained at other times. It was concluded that the rate of responding maintained by a given interval schedule depends not on the overall rate of reinforcement provided but rather on the summation of different local effects of reinforcement at different times within intervals.

Animals↗
PubMed1979

Constituents of response rates.

Response rate and the proportion of time pigeons allocated to a key-pecking activity were measured on several basic types of reinforcement schedules. Reinforcement frequency was varied within each type of basic schedule, and the effects on two constituents of response rate were noted. Propensity, the proportion of time the birds spent on a platform in front of the key, showed very consistent effects as reinforcement frequency varied: in general, it decreased when reinforcement frequency markedly decreased and it increased when reinforcement frequency increased. Speed, key pecks per unit of time spent on the platform, showed inconsistent effects when reinforcement frequency varied. Consequently, response rate showed less consistent effects than did propensity. Cumulative response records demonstrated the existence of several different types of transitions or boundary states between the key-pecking activity and other activities. The types of transitions that occurred between activities depended on both the type of reinforcement schedule and the frequency of reinforcement. The propensity data support the position that general laws of behavior can be based on temporal measures of behavior. The speed data suggest that, if a complete assessment of the dynamic properties of behavior is to be achieved, measures of behavior must incorporate the structural variations in the operant unit.

Journal Article↗
PubMed1979

Effects of contingent payment on compliance with a naltrexone regimen.

The effects of several schedules of payment on duration and patterns of compliance with a naltrexone regimen were examined. Patients were paid under contingencies based on either number of doses ingested or on a fixed time schedule. Reinforcement schedules based on number of doses ingested produced more consistent treatment-oriented behavior than a time-based schedule. Covariation between behavior and alternating contingencies (A-B-A) indicated that the schedules contributed to increased duration of treatment compared to previous noncontingent payment. The issue of using extrinsic reinforcers such as monetary payment to enhance compliance is discussed and additional procedures are suggested.

Adult↗
PubMed1997

Running and responding reinforced by the opportunity to run: effect of reinforcer duration.

The present study investigated the effect of reinforcer duration on running and on responding reinforced by the opportunity to run. Eleven male Wistar rats responded on levers for the opportunity to run in a running wheel. Opportunities to run were programmed to occur on a tandem fixed-ratio 1 variable-interval 30-s reinforcement schedule. Reinforcer duration varied across conditions from 30 to 120 s. As reinforcer duration increased, the rates of running and lever pressing declined, and latency to lever press increased. The increase in latency to respond was consistent with findings that unconditioned inhibitory aftereffects of reinforcement increase with reinforcer magnitude. The decrease in local lever-pressing rates, however, was inconsistent with the view that response strength increases with the duration of the reinforcer. Response rate varied inversely, not directly, with reinforcer duration. Furthermore, within-session data challenge satiation, fatigue, and response deprivation as determinants of the observed changes in running and responding. In sum, the results point to the need for further research with nonappetitive forms of reinforcement.

Animals↗
PubMed1976

A comparison of the key-peck and treadle-press operants in the pigeon: differential-reinforcement-of-low-rate schedule of reinforcement.

Key pecking and treadle pressing in pigeons were compared under concurrent (key-treadle) and single-operant differential-reinforcement-of-low-rate schedules of food reinforcement ranging from 5 to 60 sec (concurrent procedure) or 5 to 120 sec (single-operant procedure). Under both procedures, the two operants followed the same general law: decreasing response rate and reinforcement rate and increasing number of responses per reinforcement as a function of increasing schedule interval. High correlations were found between key pecking and treadle pressing for the measures of response rate, reinforcement rate, and responses per reinforcement. Regression equations allowed the prediction of treadle pressing from key pecking. More bursting occurred in responding to the key, and key pecking showed a more precise temporal discrimination than treadle pressing. A test for sequential dependencies between key and treadle responses showed significant dependencies not only under the concurrent procedure but also in data created artificially by merging key and treadle sequences from different pigeons under the concurrent procedure and from the same pigeon under the single-operant procedure. It seems likely that the sequential dependencies found were due to the independent action of the schedule on each operant and that behavioral dependencies did not occur with the concurrent training procedure. The key-peck operant does not appear to have any special qualities that preclude its use in discovering general laws of behavior, at least under the differential-reinforcement-of-low-rate schedule. The usefulness of the key peck in other situations requires direct experimental study.

Journal Article↗
PubMed1962

Licking behavior of rats on a schedule of food reinforcement.

Rats were trained on a variable-interval food reinforcement schedule. Lever presses and licks at the milk reinforcement were recorded independently. A dose of d-amphetamine which increased lever-pressing rates failed to affect licking rates. Licking rates increased as the duration between reinforcements on the variable-interval schedule increased.

Animals↗
PubMed1995

Beta-amyloid(1-40) effects on behavior and memory.

Beta amyloid 1-40 is a primary protein in plaques found in the brains of patients with Alzheimer's disease. There is evidence that unaggregated soluble beta-amyloid may be neurotoxic and may have behavioral effects on some types of memory. In the current study, the 1-40 fragment of beta-amyloid protein (beta A4), or vehicle, was bilaterally injected into the rostral hippocampus of rats performing under stable food-maintained schedules of reinforcement or under a delayed conditional discrimination procedure. Under the first procedure, rats were trained to stability under a multiple fixed interval 15 s, fixed ratio 30 reinforcement schedule. This reinforcement schedule has proven sensitive to low-dose drug effects. Acute bilateral hippocampal beta A4 (1.0, 2.0 and 3.0 microliters of 10(-3) M) administration did not significantly alter responding, compared to vehicle, under either reinforcement condition. Following the acute single-injection regimen, rats were administered chronic daily beta A4 (1 microliter of 10(-3) M), bilaterally, for 15 days. No significant changes in lever-pressing performance were observed during the chronic injection regimen, but performance declined significantly 30 days after termination of the chronic daily regimen. Histological examination revealed three of six rats showed positive reactions under Thioflavin S staining in and around the area of cannulae termination. The second assessment employed a delayed conditional discrimination procedure to evaluate the effects of intrahippocampal injections of beta A4 on short-term working memory. This conditional discrimination procedure assesses appropriate responding, dependent on a previously presented stimulus, after delays of various lengths have been imposed between the stimulus and the response opportunity.(ABSTRACT TRUNCATED AT 250 WORDS)

Amyloid beta-Peptides↗
PubMed2000

Self-administration of remifentanil, an ultra-short acting opioid, under continuous and progressive-ratio schedules of reinforcement in rats.

RATIONALE: Remifentanil is a mu-opioid agonist with an exceptionally short duration of action. Evaluating remifentanil's effects within the self-administration model of drug abuse may provide insight into the relationship between a drug's duration of action and its effectiveness as a reinforcer. OBJECTIVES: This study was conducted to establish a dose-effect function for intravenous remifentanil self-administration in rats and to assess the drug's ability to maintain responding under intermittent schedules of reinforcement. METHODS: Inter-infusion intervals were recorded under two continuous-reinforcement schedules of remifentanil self-administration. In the fixed-dose schedule, the unit dose (0.25-32 micrograms/kg) was held constant within sessions but varied across sessions. In the variable-dose schedule, four different doses were self-administered in random order within each session. For comparison, heroin (6.25-125 micrograms/kg) was studied with the variable-dose schedule. Remifentanil and heroin were also compared under a progressive-ratio schedule of reinforcement in which the response requirements increased exponentially with each successive infusion until responding ceased within each session. RESULTS: Under the continuous-reinforcement schedules, inter-infusion intervals for both drugs increased monotonically as a function of dose, with the remifentanil curve being considerably flatter. Under the progressive-ratio schedule, breaking points varied as an inverted-U shaped function, and the highest breaking points maintained by remifentanil and heroin were similar. At the doses that maintained the highest breaking points under the progressive-ratio schedule, post-infusion pauses under the continuous-reinforcement schedule were about three times shorter with remifentanil than with heroin. CONCLUSIONS: Although rates of self-administration are clearly influenced by a drug's duration of action, the ability to maintain responding under intermittent schedules of reinforcement may be independent of duration of action.

Analgesics, Opioid↗
PubMed1989

Response-reinforcer dependency location in interval schedules of reinforcement.

In five experiments we studied the effects on pigeons' key pecking of the location of four or more successive response-dependent reinforcers imbedded in a schedule arranging otherwise response-independent reinforcers. In Experiment 1, high local response rates early in the session were extended farther into the session as the number of response-dependent reinforcers at the beginning of the session increased. A block of four successive response-dependent reinforcers then was scheduled at the beginning, middle, or end of the session (Experiment 2) resulting in higher local response rates at those times in the session when the response-dependent reinforcers were arranged. When placed in random locations in successive sessions (Experiment 3), uniform local rates occurred throughout the session. In Experiments 1, 2, and 3, delivery of the remaining response-independent reinforcers was precluded until the response-dependent reinforcers were collected. Experiment 4 was similar to Experiments 1 and 2, except that all response-independent reinforcers occurred irrespective of whether the response-dependent reinforcers had been collected. This yielded results similar to those obtained in the first two experiments. In Experiment 5, responding early in the session had no consequence other than allowing access to the schedule of response-independent food delivery. As in the first experiment, local rates generally were higher early in the session. The results indicate that the location of response-reinforcer dependencies precisely control behavior and that such effects often are not captured by descriptions of behavior in terms of overall response rates.

Journal Article↗
PubMed1999

Operant ethanol reward in C57BL/6 mice: influence of gender and procedural variables.

Food-deprived C57BL/6 (C57) mice of either sex responded for oral ethanol rewards delivered on ratio schedules of reinforcement, thus extending to female C57 mice effects previously reported only for male members of the strain. Lever responding for ethanol reward was influenced by thirst motivation (post- vs. preprandial tests), time of access to ethanol reward, ethanol concentration, and reinforcement schedule. A particularly high response output for 12% ethanol delivered on a PR2 schedule (e.g., approximately 1400/15 min test session) indicates its efficacy as a reinforcer for C57 mice. Estimated consumption of ethanol differed from lever responding when reward access time was relatively long (10 s) and response demand of the reinforcement schedule was low, but paralleled lever responding when reward access time was restricted (3 s) and response demands were greater. Gender influenced lever responding for ethanol reward and its consumption, the difference depending upon reward access time and reinforcement schedule. When the response demands were low and the reward access time long, females tended to respond more than males for ethanol reward; with greater response demands and shorter reward access time, males tended to respond more. In conjunction with our companion report, the present study helps define the behavioral conditions under which ethanol is rewarding for C57 mice and establish the conditions under which ethanol reward differs for male and female mice.

Animals↗