A prognostic utility bias in judgments of similarity between past and present instances: How available information is deemed useful for prediction

A variety of theorists have proposed that individuals desire to be confident in their inferences and predictions. One way this can be accomplished is by overestimating the extent to which available information provides a logic basis for such conclusions. Thus, when one's goal is to make an accurate prediction, if information about a prior known instance has potential implications for the prediction, one may overestimate the similarity of the prior known instance to the current instance. In this way, the perceived utility of the information as a basis for prediction can be inflated. To test this idea, three studies were conducted. In each study, subjects were asked to judge the similarity of past instances to an upcoming instance for which an outcome prediction was required. Judging a past instance as similar to the upcoming instance should only provide a firm basis for outcome prediction if outcome information regarding the past instance is known. Therefore, it was expected that when subjects are asked to make an outcome prediction, they would judge a past instance more similar to the upcoming instance if outcome information about the past instance is known than if it is not. Support for this hypothesis was obtained along with evidence concerning the conditions under which the eflect does and does not occur.