The Self-serving Bias and Beliefs about Rationality


  • Todd R. Kaplan,

    1. Kaplan: Lecturer, University of Exeter, Exeter, EX4–4PU, UK. Phone 44–1392–263237, E-mail
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  • Bradley J. Ruffle

    1. Ruffle: Lecturer, Ben-Gurion University, P.O. Box 653, Beer Sheva, 84105, Israel. Phone 972–8–6472308, Fax 972–8–6472941, E-mail
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      We thank Yakov Gilboa for dedicated research assistance, as well as Linda Babcock, Colin Camerer, Robert Kurzban, Orit Tykocinski, seminar participants at the 8th International Conference on Social Dilemmas in Zichron-Yaakov, Learning Rational, Evolutionary, and Experimental Aspects Workshop in Beer Sheva, the ESA Annual Meetings in Lake Tahoe, and the Russell Sage behavioral economics reunion, and especially an anonymous referee of this journal for valuable comments. Financial support was provided by the Department of Economics at Ben-Gurion University.


Most previous experiments attempting to establish the existence of the self-serving bias have confounded it with strategic behavior. We design an experiment that controls for strategic behavior (Haman effects) and isolates the bias itself. The self-serving bias that we measure concerns beliefs about the rationality of others. We find very limited support for the existence of the bias. To help understand why the bias seems to hold in some settings but not in others, we discuss a distinction between biases that are self-serving and those that are actually self-defeating. (JEL C92)