Choice between small certain and large uncertain reinforcers

Abstract

When choosing between two alternatives that deliver the same amount of food per trial in the long run, organisms are called risk-averse if they choose a small certain reinforcer over a larger probabilistic reinforcer. They are called risk-prone if they choose the larger probabilistic reinforcer. This experiment attempted to predict whether rats would be risk-prone or risk-averse on the basis of their separate choices between reinforcers differing in probability and reinforcers differing in amount. Choice was measured with an adjusting-delay procedure, which provided estimates of indifference points, or pairs of alternatives that a subject chose about equally often. The subjects were usually more responsive to differences in amount than to differences in probability, leading to predictions of risk-proneness for choices between two probability-amount combinations. The predictions were confirmed in almost every case. As the number of food pellets delivered by the two alternatives was increased while maintaining a 2:1 difference between them, the tendency toward risk-proneness declined. These results suggest an explanation of the inconsistent findings obtained in previous experiments on risk-taking by rats. © 1988 Psychonomic Society, Inc.