Journal of the experimental analysis of behavior
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Free-operant avoidance responding was maintained by a shock avoidance schedule in three monkeys. The frequency of avoidance responses during a stimulus terminated by response-independent food pellet presentation was dependent upon the method of pellet delivery. Avoidance rates were relatively increased when food retrieval responses followed pellet delivery. Avoidance rates were decreased when retrieval responses preceded pellet delivery.
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Pigeons were exposed to a two-key concurrent chains schedule in which identical frequencies and distributions of food presentations generated different response rates in the terminal links. An inverse relation between local rate of response in the terminal links and relative frequency of response in the initial links was observed. ⋯ Under initial training and after spatial reversal of the terminal-link schedules, two of three pigeons had lower relative frequencies of response in the initial member of the chain with the higher terminal link response rate. The third pigeon showed no change in preference at reversal.
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Hungry rats were allowed to lick an 8% sucrose solution and then one of four lick-shock contingency conditions was superimposed on the licking baseline. These conditions were: free-operant avoidance, free shock, punishment, and no shock. From highest to lowest response rates, the groups fell in the order-avoidance, no shock, free shock, and punishment. ⋯ Post-shock responding was lowest in the punishment condition and highest in the free shock condition. No method was found simultaneously to equate shock frequency and separate response rates for the three shock contingency conditions. Only small, or no, reductions in shock rate occurred over sessions under the free-operant avoidance schedule when the shock-shock interval was 10 sec but large reductions occurred when the shock-shock interval was reduced to either 1 or 2 sec.
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Goldfish were trained to swim back and forth in a shuttle tank to avoid unsignalled shocks. The response-shock interval and the shock-shock interval were always of equal duration; both were either 15, 30, 45, or 60 sec. Response rates varied inversely with response-shock-shock-shock interval duration, as has been found with rats. ⋯ As the response-shock-shock-shock interval increased, the fish made increasingly more responses than necessary to avoid all shocks. Interresponse-time distributions showed that response probability rose to a maximum at about 15 to 25 sec after a response, regardless of the response-shock-shock-shock interval. Thus, at the longer intervals the fish were responding too early in the response-shock-shock-shock interval to minimize response rates.
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Hyperthermia was observed at the end of each conditioning session in rats trained to avoid electric shocks by jumping on a platform. The temperature rise was also observed after the conditioned behavioral response was well established and was elicited even in the absence of shocks. There was no tendency for the hyperthermia to diminish over the course of nine extinction sessions.