Are humans good intuitive statisticians after all? Rethinking some conclusions from the literature on judgment under uncertainty

Professional probabilists have long argued over what probability means, with, for example, Bayesians arguing that probabilities refer to subjective degrees of confidence and frequentists arguing that probabilities refer to the frequencies of events in the world. Recently, Gigerenzer and his colleagues have argued that these same distinctions are made by untutored subjects, and that, for many domains, the human mind represents probabilistic information as frequencies. We analyze several reasons why, from an ecological and evolutionary perspective, certain classes of problemsolving mechanisms in the human mind should be expected to represent probabilistic information as frequencies. Then, using a problem famous in the "heuristics and biases" literature for eliciting base rate neglect, we show that correct Bayesian reasoning can be elicited in 76% of subjectsindeed, 92% in the most ecologically valid condi t ionsimply by expressing the problem in frequentist terms. This result adds to the growing body of literature showing that frequentist representations cause various cognitive biases to disappear, including overconfidence, the conjunction fallacy, and base-rate neglect. Taken together, these new findings indicate that the conclusion most common in the literature on judgment under uncertaintythat our inductive reasoning mechanisms do not embody a calculus of probability will have to be re-examined. From an ecological and evolutionary perspective, humans may turn out to be good intuitive statisticians after all. * Corresponding author; e-mail: [email protected]; fax: 805-965-1163. 0010-0277/96/$15.00 ~ 1996 Elsevier Science B.V. All rights reserved SSDI 0010-0277(95)00664-8 2 L. Cosmides, J. Tooby / Cognition 58 (1996) 1-73