Journal of the experimental analysis of behavior
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Rats were trained to press a lever under schedules of food postponement. In the absence of lever presses, food was delivered periodically (food-food interval). Responses initiated a second interval (response-food interval) that was reset by each additional response. ⋯ However, responding was maintained in one animal when the food-food interval was decreased from 120 to 15 sec with the response-food interval at 30 sec. Results, in terms of several dependent variables, are compared with data on shock avoidance. Effects of response-independent and response-produced food and shock are discussed.
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Detailed descriptive data are provided on the free-operant avoidance behavior of rats in a shuttlebox during both acquisition and terminal performance. Initially, eighteen 21-min acquisition sessions were given. Each hurdle-cross postponed the next shock 20 sec (response-shock interval) and shocks were scheduled every 5 sec (shock-shock interval) in the absence of a response. ⋯ Maximum response rates were reached by the third session and declined slowly while shock rates continued to drop slowly through Session 15. Three subjects were run an additional five months with a response-shock interval of 20 sec and their terminal response rates were all under five responses per minute and shock rates were 0.07 per minute. Interresponse time distributions for terminal performance showed that over 95% of all responding by all three subjects occurred in the last half of the response-shock interval.
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Five rats (observers) were trained to avoid unsignalled shocks in a shuttlebox and then habituated to brief light presentations. They were next confined on an observation platform while another rat (model) received light-shock pairings in the opposite compartment. ⋯ Following sessions in which the model was not shocked after the light, the light presentations during avoidance eventually failed to elicit any response increases in the observers. When the model was again shocked, immediate recovery of avoidance acceleration occurred in the observers during the light.