Despite the economic and social significance of crime reduction and criminals' rehabilitation, research evaluating the effects of incarceration on behavior is surprisingly scarce. We conduct an experiment with 105 prison inmates and complement it with administrative data in order to explore several aspects of their social behavior. We first perform a comprehensive analysis of behavior in three economic games, finding evidence of discrimination against a sample from outside prison. In addition, our regression analysis reveals that inmates generally become less pro-social towards this out-group the longer they remain incarcerated. Finally, we introduce and evaluate a priming intervention that asks inmates to reflect on their time spent in prison. This intervention has a very sizeable and significant impact, increasing pro-sociality towards the out-group. Hence, a simple, low-cost intervention of this sort can have desirable effects in promoting rehabilitation and integration into social and economic life after release. (C) 2019 The Authors. Published by Elsevier Inc.