How does war shape human altruism? Some find warfare increases generosity within groups only. Others maintain that war's prosocial effects extend to outgroup members as well. To make sense of these disparate findings, we offer a theoretical framework that highlights the role of threat sensitivity in altruism. Refugees from Syria and Iraq (N = 1521) completed a welfare tradeoff task and threat perceptions scale where the other's group identity, gender and age were experimentally varied. We found that individuals belonging to social categories associated with more threat (outgroup members, males, and younger individuals) were afforded less altruism compared to individuals belonging to non-threatening social categories (ingroup members, females and the elderly). War exposure enhanced bias against threatening social categories through increased threat-sensitivity. Our results have implications for understanding how warfare shapes altruism and welfare tradeoffs in light of cross-cutting social categories and for policies promoting post-conflict cooperation.

战争如何塑造人类的利他主义？有些人发现战争只会增加团体内的慷慨。其他人则坚持认为，战争的亲社会影响也扩大到了集团外成员。为了理解这些不同的发现，我们提供了一个理论框架，强调了威胁敏感性在利他主义中的作用。从叙利亚和伊拉克（难民ñ = 1521）完成了福利权衡任务和威胁感知量表，在实验中，对方的群体身份，性别和年龄发生了变化。我们发现，与属于非威胁性社会类别的人（团体成员，女性和老年人）相比，属于与更多威胁相关的社会类别的人（团体成员，男性和年轻人）的利他行为更少。战争暴露通过提高对威胁的敏感性而增强了对威胁社会类别的偏见。我们的研究结果对于理解战争如何根据交叉的社会类别影响利他主义和福利权衡以及促进冲突后合作的政策具有重要意义。