 Group-specific norms have (among other things) the twofold function of minimizing perceived differences among group-members and maximizing differences between the group and outsiders. Once formed, such norms become stable cognitive representations of appropriate behavior as a group-member. Social identity is built around group characteristics and behavioral standards, and hence any perceived lack of conformity to group norms is seen as a threat to the legitimacy of the group. Self-categorization accentuates the similarities between one’s behavior and that prescribed by the group norm, thus causing conformity as well as the disposition to control and punish transgressors. In the social identity framework, group norms are obeyed because one identifies with the group, and conformity is mediated by self-categorization as an in-group member. A telling historical example of the relationship between norms and group membership was the division of England into the two parties of the Roundheads and Cavaliers. Charles Mackay reports that 