Confidence in judgment: Persistence of the illusion of validity.

An accumulating body of research on clinical judgment, decision making, and probability estimation has documented a substantial lack of ability of both ex-perts and nonexperts. However, evidence shows that people have great confi-dence in their fallible judgment. This article examines how this contradiction can be resolved and, in so doing, discusses the relationship between learning and experience. The basic tasks that are considered involve judgments made for the purpose of choosing between actions. At some later time, outcome feedback is used for evaluating the accuracy of judgment. The manner in which judgments of the contingency between predictions and outcomes are made is discussed and is related to the difficulty people have in searching for discommoning informa-tion to test hypotheses. A model for learning and maintaining confidence in ones own judgment is developed that includes the effects of experience and both the frequency and importance of positive and negative feedback. Everyone complains of his memory and no one com-plains of his judgment. (La Rochefoucauld, 1959, p. 49) Although the study and cataloguing of judgmental fallability has had a long history in psychology (see, e.g., Guilford, 1954, chap. 12; Johnson, 1972), an accumulating body of recent research on clinical judgment, decision making, and probability estimation has docu-mented a substantial lack of ability across both individuals and situations (Slovic, Fisch-hoff, Lichtenstein, 1977; Slovic Lichten-stein, 1971). For example, predictive ability has been shown to have low (and even zero) validity in clinical settings (see, e.g., Einhorn, 1972; Goldberg, 1968, and his references).