Abstract: In this dissertation, I examine a fundamental sociological question: how does conflict between groups affect relations within groups? I present theoretical arguments specifying the conditions under which groups in conflict will develop stricter norms and more centralized systems of leadership than groups that do not experience conflict. I evaluate the predictions using two laboratory studies, in which small groups interact under varying levels of conflict. The results of the studies show that conflict influences the emergence of social norms, group cohesion, and the creation of hierarchies. The project has broader theoretical implications for the study of institutions, social control, and collective action, as well as practical relevance for developing conflict resolution strategies.