In a typical probability learning task participants are presented with a repeated choice between two response alternatives, one of which has a higher payoff probability than the other. Rational choice theory requires that participants should eventually allocate all their responses to the high-payoff alternative, but previous research has found that people fail to maximize their payoffs. Instead, it is commonly observed that people match their response probabilities to the payoff probabilities. We report three experiments on this choice anomaly using a simple probability learning task in which participants were provided with (i) large financial incentives, (ii) meaningful and regular feedback, and (iii) extensive training. In each experiment large proportions of participants adopted the optimal response strategy and all three of the factors mentioned above contributed to this. The results are supportive of rational choice theory. Copyright # 2002 John Wiley & Sons, Ltd.key words probability matching; maximization; choice; rationality; feedback; payoffs; learning; reinforcement A striking violation of rational choice theory is commonly observed in simple repeated binary choice tasks in which a payoff is available with higher probability given one response than another. In such tasks people often tend to 'match' probabilities: That is, they allocate their responses to the two options in proportion to their relative payoff probabilities. Thus suppose that a monetary payoff of fixed size is given with probability p ¼ 0.7 for choosing left and with probability 1 À p ¼ 0.3 for choosing right. Probability matching refers to behavior in which left is chosen on about 70% of trials and right on 30%. Such responding violates rational choice theory because the optimal strategy in such tasks, after an initial period of experimentation and assuming that the payoff probabilities are stationary, is always to select the option associated with the higher probability of payoff. On any trial, the expected payoff for choosing left is higher than the expected payoff for choosing right.