Social identity theory defines group cognitively, in terms of people’s self-conception as group members. A group exists psychologically if three or more people construe and evaluate themselves in terms of shared attributes that distinguish them collectively from other people. Social identity theory addresses phenomena such as prejudice, discrimination, ethnocentrism, stereotyping, intergroup conflict, conformity normative behavior, group polarizations, crown behavior, organizational behavior, leadership, deviance, and group cohesiveness.
Social identity theory was first developed at the start of the 1970s in Britain by Henri Taijfel, out if his scientific and personal interest in social perception, social categorization, and social comparison and prejudice, discrimination, and intergroup conflict. Over the past 30 years social identity theory has attracted many collaborators and followers. It has developed and matures conceptually and has motivated, and continues to motivate, a prodigious quantity research. Although initially a European analysis of intergroup relations, since the early 1990s it has become accepted around the world as one of mainstream social psychology’s most significant general theories of the relationship between self and group. However, this popularity has sometimes brought with it a disjunction between some readings of social identity concept and the