We test the assumption that social preferences are unchanged throughout a one-shot strategic game. To do so, we study the relationship between the strategic nature of a game and identi...cation in social groups. In our experiment, the subjects play one of two versions of the prisoner's dilemma game where the attractiveness of the uncooperative action is manipulated. We refer to the version with a relatively attractive uncooperative action as the Mean Game and the other as the Nice Game. Note

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... t choice is relatively more di¢ cult in the Nice Game as a result of the smaller di¤erence between the payo¤s associated the actions. We ...nd that the strategic nature of the game a¤ects the strength of identity. Speci...cally, we ...nd that in the Mean Game there is little di¤erence in the change in identi...cation of those playing cooperatively and those playing uncooperatively. However, in the Nice Game those playing cooperatively exhibit a signi...cantly stronger change in identi...cation than those playing uncooperatively. We also present evidence regarding the timing of the change in identity and what causes this change. In particular, the decision di¢ culty literature is helpful in interpreting the results.