Random-interval Schedules Of Reinforcement Research Articles

Rate-dependent effects of amphetamine on responding under random-interval schedules of reinforcement in the rat

The parameters of 12 random-interval schedules (cycle length and interreinforcement interval) were varied systematically in order to examine the ability of these schedules to separate the usual relationship between response rate and reinforcement frequency using rats. Response rates varied over a two-fold range for the same frequency of reinforcement under random-interval 30-sec schedules. However, cycle length did not alter response rates significantly at other interreinforcement intervals. Subsequently, the effects of amphetamine on random-interval responding were examined in order to evaluate the roles of control rates of responding and reinforcement in amphetamine's actions. Amphetamine's effects were significantly correlated with both control response rate and control rate of reinforcement. However, by comparison, control response rate was the better predictor of amphetamine behavioral effects. The results support the rate dependency hypothesis that control rate of responding is closely associated with amphetamine's effects on operant behavior.

Microwave Irradiation and Ambient Temperature Interact to Alter Rat Behavior Following Overnight Exposure

Each of twelve male hooded rats was trained to insert its head into a food cup for food pellets on a random-interval schedule of reinforcement. After performances stabilized, the rats were assorted into 3 groups of 4 animals. Groups were matched for response rates. Animals were exposed in groups of 4 for 15.5 h to CW 2450-MHz microwaves once every 6 nights. Animals of each group were exposed to microwaves at only one power density, either 5, 10, or 15 mW/cm2; they were exposed three times at an ambient temperature of 22 degrees C, then three times at 28 degrees C, and then once more at 22 degrees C. The relative humidity was 50% during all exposures. Rats were sham irradiated (at 0 mW/cm2) the night before each microwave exposure. Behavior was tested daily after termination of microwave irradiation or after sham exposures. None of the exposures to microwaves at 22 degrees C altered rates or durations of responding. Exposures at 28 degrees C reduced response rates and increased response durations in direct relation to the power density. The results are interpreted as the transient debilitation of behavior produced by the interaction of a mild elevation of ambient temperature and microwave irradiation.

The effects of d-amphetamine on the temporal control of operant responding in rats during a preshock stimulus.

The operant behavior of six rats was maintained by a random-interval schedule of reinforcement. Three-minute periods of noise were superimposed on this behavior, each period ending with the delivery of an unavoidable shock. Overall rates of responding were generally lower during the periods of noise than in its absence (conditioned suppression). These suppressed response rates also exhibited temporal patterning, with responding becoming less frequent as each noise period progressed. The effects of d-amphetamine on this behavioral baseline were then assessed. In four animals the relative response rates during the noise and in its absence suggested that the drug produced a dose-related decrease in the amount of conditioned suppression. However, this effect was often due to a decrease in the rates of responding in the absence of the preshock stimulus, rather than to an increase in response rates during the stimulus. Temporal patterning in response rates during the preshock stimulus was abolished, an effect that was interpreted in terms of rate-dependent effect of d-amphetamine. This study thus extends rate-dependent analyses of the effects of amphetamines to the patterns of operant behavior that occur during a preshock stimulus, and which have been discussed in terms of the disrupting effects of anxiety on operant behavior.

Response-Reinforcer Relationships in Variable Delay and Non-Contingent Schedules of Reinforcement

Following 30 sessions of training on a 60-sec. random-interval schedule of reinforcement, 2 pigeons were exposed to a multiple schedule containing non-contingent and variable delay components that provided equal frequencies of reinforcement. The introduction of the multiple schedule resulted in decreased response rare in both components, with a higher rate maintained under the variable delay. Post-reinforcement pauses were systematically increased during the non-contingent schedule, but no systematic increases in pause duration were noted for the variable delay component.

Concurrent random interval schedules of reinforcement

Two pigeons were trained on concurrent random interval schedules of reinforcement. The parameters of the schedules were then changed to make them progressively more ratio-like, while maintaining their average interreinforcement intervals of 32 and 64 sec. Both the relative response rate and the relative amount of time spent on each schedule matched the relative rate of reinforcement, as it varied from 36% to 2%. Preference became extreme when the changeover delay was increased from 2 to 5 sec, but matching was still obtained.

PROPERTIES OF BEHAVIOR UNDER RANDOM INTERVAL REINFORCEMENT SCHEDULES.

In a temporally defined system of reinforcement schedules, the fixed interval case is defined when reinforcement probability, P, is equal to unity for the first response in any cycle length, T; when P is less than 1.0, random interval schedules emerge wherein T/P specifies the expected interval between reinforcements. Key-pecking rates were found to be: (a) inversely related to T/P; (b) higher at T=1.0 second than at other T parameter values; (c) low and linear at several T and T/P values. The mean post-reinforcement pause, if initially small, increased, and if initially large, decreased, as T/P increased.