Tajfel (1979) proposed that the groups (e.g. social class, family, football team etc.) which people belonged to were an important source of pride and self-esteem. Groups give us a sense of social identity: a sense of belonging to the social world.
n order to increase our self-image we enhance the status of the group to which we belong. For example, England is the best country in the world! We can also increase our self-image by discriminating and holding prejudice views against the out group (the group we don’t belong to). For example, the Americans, French etc. are a bunch of losers!
Therefore, we divided the world into “them” and “us” based through a process of social categorization (i.e. we put people into social groups).
This is known as in-group (us) and out-group (them). Social identity theory states that the in-group will discriminate against the out-group to enhance their self-image.
The central hypothesis of social identity theory is that group members of an in-group will seek to find negative aspects of an out-group, thus enhancing their self-image.