Conditional probability judgments: Effects of imagining vs experiencing the conditioning event

Abstract

Applications of Bayesian conditionalization often involve two temporal aspects: a probability judgment is based on knowledge at a point in time and is revised over time in light of added information. Let t, t′, and t″ designate three chronological points in time. E designates a target event which occurs or not at t″, and C designates a conditioning event which occurs or not at t′. Suppose that an individual judges P( E⧹ C) at t. If C occurs, Bayesian conditionalization requires that a judgment of P( E) at t′ is equal to the earlier judgment of P( E⧹ C). However, inconsistencies may result because a judgment of P( E⧹ C) at t is based on imagining C, while a judgment of P( E) at t′ is based on experiencing C. This study examines two sources of such inconsistencies. First, C normally is an abstraction of what might happen between t and t′. What actually happens may differ, such that an individual observes extraconditional information which affects a judgment of P( E) at t′. Second, experiencing C may change an individual's affective state, leading to greater optimism or pessimism about the occurrence of E. We report an experiment which documents both effects.