The role of contingency discriminability in suboptimal choice

Suboptimal choice consists of a preference for an alternative with a lower probability of reinforcement (suboptimal alternative) over another with a higher probability of reinforcement (optimal alternative) when the former has discriminative stimuli that signal in which trials a reinforcer will be delivered and in which trials it will not. Discriminating the contingencies of reinforcement associated with the stimuli of the suboptimal alternative is necessary to produce suboptimal choice, but the impact of different degrees of discriminability has not been systematically studied. The discriminability of the contingencies of reinforcement depends on the difference in the probability of reinforcement of the two stimuli; higher differences yield higher discriminability. Pigeons were exposed to a procedure that presented a choice between two alternatives, each associated with two stimuli. The contingency discriminability of the suboptimal alternative was manipulated across conditions, while the contingency discriminability of the optimal alternative was absent in all conditions. The overall probability of reinforcement of each alternative remained the same throughout the experiment (p = .2 and p = .5 for the suboptimal and optimal alternatives, respectively). The preference for the suboptimal alternative increased as its discriminability increased. There was a positive correlation between discrimination index and preference for the suboptimal alternative. These results highlight the importance of contingency discriminability to generate suboptimal choice.