Social identity theory was developed in the 1970s and 1980s by Henri Tajfel and John Turner to explain intergroup conflict, and in particular, in-group favoritism and out-group prejudice and discrimination. Social identities are the parts of our self-concept that derive from our membership in groups and the emotional attachment we have to such groups. Social identities emerge in early childhood and are important parts of the self-concept throughout the life span. While individuals can potentially belong to many groups, only groups with which they identify with are meaningful identities—that is, social identities are chosen. These identities can include social structural categories such as age (e.g., adolescents, baby boomers), gender, race/ethnicity, and social class as well as other groups that give people a sense of we, ...