The field of interpersonal influence has a long tradition of studying group norms. Norms are the stated and implicit rules of a group that identify the range of acceptable behavior. Often couched in moral terms, these principles provide a basis for action when the situation is confusing. Social exchange theory describes norms as socially rewarded transformations aimed at curbing the use of raw power. The language of prison reveals that there is indeed an enforced honor among thieves. Labels of "cheat," "fink," or "snitch" add to the cost of squealing on a buddy, so the classic prisoner’s dilemma looks different from within the walls.