Journal of Personality and Social Psycholocy 1977, Vol 35, No. 11, 817-829 Social Explanation and Social Expectation: Effects of Real and Hypothetical Explanations on Subjective Likelihood Lee Ross, Mark R. Lepper, Fritz Strack, and Julia Steinmetz Stanford University Subjects in three experiments were induced to explain particular events in the later lives of clinical patients whose previous case histories they had read, and they were then asked to estimate the likelihood of the events in question. Each experiment indicated that the task of identifying potential antecedents to ex- plain an event increases that event's subjective likelihood This phenomenon was replicated across a variety of clinical case studies and predicted events and was evident both under conditions in which subjects initially believed the events they explained to be authentic, only to learn afterward that no information actually existed about the later life of the patient, and under conditions in which sub- jects knew from the outset that their explanations were merely hypothetical. Implications of these findings for previous investigations dealing with belief perseverance and the consequences of hindsight perspective are outlined, and potential boundary conditions of the observed effect are discussed. Our perceptions of social phenomena—from automobile accidents to political upheavals, from academic failures to acts of altruism—are organized in considerable measure by the underlying causal connections we detect or postulate. Attribution theorists, among many others, have long emphasized the extent to which causal inferences add coherence to our perceptions of the entities and events in our social world. Indeed, several generations of such theorists have explored both the logical rules or schemata that may underlie judgments of social causality and the biases that may distort such judgments (e.g., deCharms, 1968; Two of the three experiments described in this article were previously reported in a paper by Fritz Strack, Mark R. Lepper, and Lee Ross entitled "Explaining is Believing: The Effects of Providing a Causal Explana- tion on the Perceived Probability of an Event's Occur- rence " This paper was presented at the 56th Annual Meeting of the Western Psychological Association, Los Angeles, April 1976. The present research was supported, in part, by National Institute of Mental Health Research Grant MH-26736 to Lee Ross and Mark R. Lepper and by a Harkness Foundation Fellowship held by Fritz Strack. The authors gratefully acknowledge helpful comments on the manuscript and/or research by Robert Abelson, John Carroll, David Greene, and Richard Nisbett. Julia Steinmetz is now at the University of Oregon. Requests for reprints should be sent to Lee Ross, department of Psychology, Jordan Hall, Stanford University, Stanford, California 94305. Heider, 1944, 1958, Jones & Davis, 1965; Jones etal., 1972; Kelley, 1967,1973; Kruglan- ski, 1975, Ross, 1977). Recently, however, Ross, Lepper, and Hubbard (1975) have suggested that an un- warranted perseverance of initial beliefs and impressions may be one cost of man's proclivity for causal explanation. Briefly, Ross et al. (1975) reported two studies in which false feedback concerning performance on a novel discrimination task (i.e., distinguishing au- thentic suicide notes from fictitious ones) continued to influence both the self-perceptions of the actors and the social perceptions of observers even after that initial feedback had been totally discredited through an extensive, standard debriefing procedure. This persever- ance effect has since been replicated using a variety of experimental settings and pro- cedures for discrediting the evidential basis for these impressions of information (cf. Lau, Lepper, & Ross, Note 1; Jennings, Lepper, Ross, & Steinmetz, Note 2). For instance, Lau et al. (Note 1) demonstrated that students' erroneous impressions concerning their logical problem-solving abilities (based on their performance in an initial test situation) persevered, even after the students learned that good or poor teaching performance had virtually guaranteed their original success or failure. Despite subsequent exposure to alter- 817