Use of the availability heuristic in probability estimates of future events: The effects of imagining outcomes versus imagining reasons

Abstract

Individuals have been shown to estimate the probability of future events by the ease with which they can recall or cognitively construct relevant instances. Previous research, however, has not precisely identified the cognitive processes mediating this “availability heuristic.” We proposed two potential mediators, (1) imagery of the event itself and (2) perceived reasons or causes for the event, and hypothesized that probability estimates are influenced by the latter but not by the former. Using the 1984 presidential debate as the to-be-predicted event, we tested this hypothesis by manipulating debate outcome (Reagan vs Mondale wins), imagery of the outcome, and reasons for the outcome in a factorial design. As hypothesized, debate predictions were affected by the availability of reasons but not by imagery of the outcome. Participants' self-generated reasons for the debate outcome, as assessed during the experiment by a thought-listing procedure, also affected debate predictions. The results are consistent with several lines of research indicating the importance of causal thinking in judgment under uncertainty.