Why do people form groups, and why do they feel so strongly about them? Consider the celebrations that follow a sports team’s winning a national champi-onship. Fans have staked their own self-image on the performance of someone else. The winner’s supporters are elated, and sales of team-related shirts, jackets, and hats declaring support for the team skyrocket. Fans of the losing team feel dejected, even embarrassed. Our tendency to take personal pride or offense for the accomplishments of a group is the territory of
social identity theory