Preference for 50% reinforcement over 75% reinforcement by pigeons

Abstract

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 ...

Suboptimal choice behavior by pigeons

“…According to information theory, reducing the probability of reinforcement from 50% (in Gipson et al, 2009) to 20% in the present experiment should have reduced the information provided by the discriminative stimuli, because signals for reinforcement and nonreinforcement should be most informative when without them there would be maximum ambiguity (i.e., 50% reinforcement). Thus, reducing the overall probability of reinforcement should have reduced the preference for the alternative leading to the discriminative stimuli.…”

“…The experiment was conducted in a BRS/LVE (Laurel, MD) sound-attenuating standard operant test chamber (see Gipson et al, 2009, for details).…”

“…In a more recent study, when choice of one alternative provided 75% reinforcement and choice of the other provided only 50% reinforcement but was followed by discriminative stimuli (one followed by 100% reinforcement, the other by 0% reinforcement), pigeons showed a reliable (69%) preference for the 50% reinforcement alternative (Gipson, Alessandri, Miller, & Zentall, 2009). …”

Information Seeking in Animals: Metacognition?

“…Animals preferred to observe stimuli that predicted whether reinforcement would or would not be delivered over cues that were non-informative. Finally, the Gipson et al (2009) experiment showed that pigeons strongly preferred to peck a key that led to only 50% reinforcement over a key that led to 75% reinforcement because the 50% key led to cues consistently predictive of reinforcement and non-reinforcement and the 75% key did not.…”

“…Even more striking is a recent report by Gipson, Alessandri, Miller, and Zentall (2009;Experiment 2; also see Zentall, 2011). Pigeons chose between left and right white keys, with pecks on one key turning the key red on a random 50% of the trials and green on the other 50% of the trials.…”