Journal of the experimental analysis of behavior
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The effects of different voltages of response-dependent and response-independent electric shock on the frequency of key-peck responses engendered by an autoshaping procedure were studied. In Experiments I and II, each response produced a brief electric shock, and response frequency generally decreased more with higher-voltage shock. Preshock frequencies of responding were generally recovered across successive sessions of relatively low-voltage shock delivery but not at higher shock voltages. ⋯ In the final experiment, one response-independent shock per autoshaping trial was scheduled. The number of autoshaped responses per trial was related to shock voltages. These results suggest that response-dependent and response-independent electric shock effectively decrease frequency of autoshaped responses.
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Pigeons' pecks were reinforced according to a variable-interval schedule. A delay-of-reinforcement procedure was then added to the schedule, or a yoked-control procedure was arranged where the reinforcers occurred independently of responding according to the same variable-interval schedule. During the delay-of-reinforcement procedure, the first peck after a reinforcer was scheduled began a delay timer and the reinforcer was delivered at the end of the interval. ⋯ Responding under this procedure was highly variable but, in general, behavior was substantially reduced even with the shortest delay used, 3 sec. In addition, the rates maintained by delayed reinforcement were only slightly greater than those maintained by the yoked-control procedure, suggesting that adventitious pairings of response and reinforcer were responsible for some of the maintenance of behavior that did occur. The results challenge recent conceptions of reinforcement as involving response-reinforcer correlations and re-emphasize the role of temporal proximity between response and reinforcer.
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In three experiments, behavior maintained by fixed-interval schedules changed when response-independent reinforcement was delivered concurrently according to fixed- or variable-time schedules. In Experiment I, a pattern of positively accelerated responding during fixed interval was changed to a linear pattern when response-independent reinforcement occurred under a variable-time schedule. ⋯ In the final experiment, the addition of response-independent reinforcement at fixed times to a fixed-interval schedule resulted in changes in both local and overall response rates and in the occurrence of positively accelerated responding between reinforcements. These results suggest that the temporal distribution of reinforcers determines response patterns and that both the response-reinforcement dependency and the schedule of reinforcement determine overall response rates during concurrently scheduled response-dependent and response-independent reinforcement.
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The effects of promazine on treadle pressing to postpone the presentation of electric shock were studied in three pigeons. The effects of chlorpromazine, d-amphetamine, and pentobarbital were studied in two of these pigeons. Each treadle press postponed electric shock for 20 sec and presentation of a preshock stimulus for 14 sec. ⋯ In the other bird, the 10 mg/kg dose of d-amphetamine increased shock rate but did not change response rate. Some doses of d-amphetamine increased the conditional probabilities of responding both in the absence of the preshock signal and during the preshock signal in both birds. Pentobarbital only decreased response rates and increased shock rates.
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The present study investigated whether choice of a signalled variable-time shock schedule over an unsignalled one was influenced by the average intershock interval. Eight rats were given a choice between signalled and unsignalled shock schedules in a series of conditions with average intershock intervals of 510, 270, 150, 90, 60, and 45 sec. ⋯ The per cent of time in the signalled condition was highest when the average intershock interval was 150 sec or longer and lowest when the average intershock interval was 45 sec. The findings were interpreted as being due to changes in the safety features of the signalled schedule, rather than to changes in the average intershock interval per se.