Increased or reversed? The effect of surprise on hindsight bias depends on the hindsight component.

Two diverging hypotheses concerning the influence of surprising events on hindsight effects have been proposed: Although some authors believe that surprising events lead to a reversal of hindsight bias, others have proposed that surprise increases hindsight bias. Drawing on the separate-components view of the hindsight bias (which argues that hindsight bias consists of 3 independent components: memory distortions, impressions of inevitability and impressions of foreseeability), we reconcile these 2 perspectives by relating them to foreseeability and inevitability. Specifically, we assume that reversals in hindsight bias are to be found when foreseeability is considered, and increases in hindsight bias are found when inevitability is considered. To test these assumptions, we arranged for participants to learn about a highly surprising outcome and subsequently judge its foreseeability and inevitability. Results were consistent with our hypotheses: Participants perceived a highly surprising but explainable outcome to be both more inevitable and less foreseeable than participants who did not received outcome information. On the basis of experimentally induced dissociations between hindsight components, the present results thus strongly support the separate-components view of the hindsight bias.