The propensity effect: when foresight trumps hindsight.

The hindsight bias is an inability to disregard known outcome information when estimating earlier likelihoods of that outcome. The propensity effect, a reversal of this hindsight bias, is apparently unique to judgments involving momentum and trajectory (in which there is a strongly implied propensity toward a specific outcome). In the present study, the propensity effect occurred only in judgments involving dynamic stimuli (computer animations of traffic accidents vs. text descriptions), and only when foresight judgments were temporally near to (vs. far from) a focal outcome. This research was motivated by the applied question of whether the courtroom use of computer animation increases the hindsight bias in jurors' decision making; findings revealed that the hindsight bias was more than doubled when computer animations, rather than text-plus-diagram descriptions, were used. Therefore, in addition to providing theoretical insights of relevance to cognitive, perceptual, and social psychologists, these results have important legal implications.