Certainty and Uncertainty: The Two Faces of the Hindsight Bias

“Hindsight Bias” is a person's tendency, after learning about the actual outcome of a situation or the correct answer to a question, to distort a previous judgment in the direction of this new information. In the literature, hindsight bias has been mostly discussed as an inevitable result of a “judgment under uncertainty.” We think that the hindsight bias is due to memorial as well as inferential processes: Whereas certainty about the recollection is memorial and concerns the recollective experience, certainty at the time of the judgment is inferential and concerns the individual's metaknowledge (“I know that I knew that”). In two experiments participants' feelings of certainty were measured indirectly (Koriat & Goldsmith, 1996) by giving participants the option of leaving those questions unanswered about which they felt uncertain. This free-report option was offered to half of the participants in the first estimate phase (concerning time of judgment) and to the second half in the memory phase (concerning the recollective experience). At the end of the session, participants were presented again with the questions they had skipped and were now required to answer them. This procedure allowed us to compare the amount of hindsight bias for the skipped, uncertain items to the spontaneously answered, certain ones. Both experiments demonstrated that the hindsight bias is a result of the interaction of both uncertainty and certainty.