When animals appear to behave maladaptively, it may inform us about the processes underlying their behavior. Hungry animals generally prefer alternatives that provide more reinforcement or a higher probability of reinforcement. Thus, when Kendall (1974) reported that pigeons p prefered an alternative that provided food 50% of the time over one that provided food 100% of the time, the result was surprising. In Kendall's procedure, choice of one alternative led to a white-lit key and reinforcement 100% of the time, whereas choice of the other alternative led to reinforcement 50% of the time-100% of the time when a green light appeared, 0% of the time when a red light appeared. Kendall found that all four of his pigeons preferred the 50% reinforcement alternative. Fantino, Dunn, and Meck (1979) noted an unusual asp pect of Kendall's (1974) procedure that may have been responsible for the pigeons' surprising preference. By using dark keys in the initial link and by illuminating only the key that was chosen, the unchosen key remained dark, as it was during the initial link. Thus, when the pigeon chose the 50% reinforcement alternative and received the stimulus associated with 100% reinforcement, it continued to peck that key, but when it received the stimulus associated peck that key, but when it received the stimulus associated with 0% reinforcement, it switched to the dark (inoperak tive) key because of its similarity to the dark initial-link key. This meant that the effective rate of reinforcement on the nominal 50% reinforcement side was actually closer to 100%, because the pigeons would switch to the other side when nonreinforcement was predicted. On the other hand, the effective rate of reinforcement on the nominal 100% side was actually less, because although it was 100% on the trials when the pigeons chose the 100% reinforcement side, it was 0% when the pigeon chose the 50% reinforcement side and the 0% reinforcement stimulus appeared, because the pigeon would tend to switch to the other (now inoperative) side key. Fantino et al. found, in fact, that when the stimulus on the chosen key was correlated with nonreinforcement, the pigeons began pecking the inoperative dark key. Fantino et al. (1979) also showed that when the two keys in the initial link were lit (white) and the unchosen d key turned dark, the pigeons more adaptively preferred the high-density reinforcement alternative over the lowdensity reinforcement alternative (about 62% of the time). When they attempted to replicate Kendall's (1974) procedure, although they did not find an overall preference for dure, although they did not find an overall preference for University of Kentucky, Lexington, KentuckyWhen pigeons are given a choice between an initial-link alternative that results in either a terminal-link stimulus correlated with 100% reinforcement or a stimulus correlated with 0% reinforcement (overall 50% reinforcement) and another initial-link alternative that always results in a terminal-link stimulus correlated with 100% reinforcement, some ...

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The recurrence of negatively reinforced responding of humans was studied in three experiments. In each experiment during Baseline, key-pressing produced 3-s timeouts from a requirement to exert finger pressure on a force cell according to variable- or fixed-ratio schedules of reinforcement. In Experiment 1, resurgence was studied by arranging a differential-reinforcement-of-other-behavior schedule in the second phase, and extinction in the Test phase. In Experiment 2, ABA renewal was studied by extinguishing responding in the second phase in a different context and, in the Test phase, by presenting the Baseline-phase context when extinction still was in effect. In Experiment 3, reinstatement was studied by arranging extinction in the second phase, followed by the delivery of response-independent timeouts in the Test phase. Resurgence and renewal occurred consistently for each participant in Experiments 1 and 2, respectively. In Experiment 3, reinstatement was observed less consistently in four participants. The results of these experiments replicate and extend to negatively reinforced responding previous findings of the resurgence and renewal of positively reinforced responding obtained mainly with nonhuman animals.