Winter is coming: detecting and exploiting period changes in probability


Summer and winter, day and night: periodic change is abundant in the natural environment. We examine whether people can detect and exploit period changes in probability in two tasks: (1) estimating the probability of success and (2) choosing to gamble on success. Probability varied sinusoidially across trials. We demonstrate that people are sensitive to periodic trends but the effects of trends differed markedly in the two tasks. In probability reports, people give more weight to positive evidence when they are on an upslope and less weight to negative evidence with the opposite pattern on downslopes. In the gambling tasks, the effects were reversed.