He is primarily known for his work on identity, self and self-esteem, but has also done research on relationships, social cognition, group processes, accuracy in person perception and interpersonal expectancy effects.
Once people develop firmly held beliefs about themselves, the theory suggests that they will come to prefer that others see them as they see themselves—even if their self-views are negative.
[12] Identity fusion is a visceral sense of "oneness" with a group and its individual members that motivates personally costly, pro-group behaviors.
[16][17][18][19] Moreover, feelings of personal agency, perceptions of family-like ties to other group members, and a sense of group-related invulnerability mediate the link between identity fusion and pro-group behaviors.
Moreover, identity fusion is associated with actual extreme behaviors, such as willingness to volunteer for front-line duty among Libyans during the 2011 revolution.