Misjudging Priors

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Science  24 Mar 2006:
Vol. 311, Issue 5768, pp. 1675
DOI: 10.1126/science.311.5768.1675c

Mental models or simulations of future outcomes can be extremely helpful in planning and guiding our behavior, as when a forward model of a reaching movement is used to reduce the variance in the trajectory of the arm. In situations where several outcomes with associated likelihoods exist, there is a known tendency, referred to as hindsight bias, for the actual outcome to inflate our post-outcome estimates of the initial likelihoods.

One arena where this bias comes into play is in the forensic reconstructions of traffic accidents, and Roese et al. have examined whether using computerized simulations (versus text and diagram visual aids) elicits these overestimates. They find that animated sequences exacerbate hindsight bias and, more intriguingly, that the bias reverses when the post-outcome estimate is compared to one made just before the time of collision. This so-called propensity effect describes our sense that the collision is destined to occur before it takes place, something we are surprisingly less certain about after the collision has actually occurred. — GJC

Psychol. Sci. 17, 305 (2006).

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