Good Choice, Bad Judgment: How Choice Under Uncertainty Generates Overoptimism

We examine a fundamental feature of choice under uncertainty: Overestimating an alternative makes one more likely to choose it. If people are naive to this structural feature, then they will tend to have erroneously inflated expectations for the alternatives they choose. In contrast to theories of motivated reasoning, this theory suggests that individuals will overestimate chosen alternatives even before they make their choice. In four studies, we found that students and managers exhibited behavior consistent with naïveté toward this relationship between estimation error and choice, leaving them overoptimistic about their chosen alternatives. This overoptimism from choosing positive error is exacerbated when the true values of the alternatives are close together, when there is more uncertainty about the values of alternatives, and when there are many alternatives to choose from. Our results illustrate how readily overoptimism emerges as a result of statistical naïveté, even in the absence of a desire to justify one's decision after the choice.