Most of his previous and current research has in common a concern with social identity; that is, the contribution of various group memberships—including gender, nation, and organization—to the self. This research has had the dual purpose of (a) examining the nature of social identification from a multidimensional perspective; and (b) investigating the correlates and consequences of various facets of group identification, including intergroup attitudes, collective action, psychological well-being, nationalism, and internationalism.