The Disjunction Effect and Reason-Based Choice in Games

This paper reports an experiment that extends previous find ings of the disjunction effect, sometimes described as a violation of Savage's sure-thing principle. Evidence of the disjunction ef fect is observed using elicited beliefs about others' actions (rather than controlled beliefs) in a prisoners' dilemma studied by Shafir and Tversky (1992) as well as in an asymmetric version of it and in a nondilemma game with a unique equilibrium. Debiasing tech niques as well as implications for these extensions are discussed. Copyright 1999 Academic Press.