Cumulative Distortion of Judgment

Abstract

A method is proposed for investigating in the laboratory the development of progressively biased judgments over time. If each successive judgment applies a bias to the results of previously biased judgments, cumulative judgmental distortions of extreme magnitude result. Two-person groups judge the lengths of a set of recurring lines, and they are corrected after each judgment. Each correction contains a bias applied to Ss' previous judgment of the same line. After 30 test trials, Ss were overestimating lines by 300%. The importance of cumulative distortion in natural settings is discussed. It is further shown how different mechanisms for internalizing judgmental bias proposed by Kelman may be studied by the present method.