An out-group is a social group to which a person does not belong and may feel opposition or hostility toward. It is the counterpart to the in-group. The distinction is not about objective difference. It is about perceived membership. A person can be in one group and out of another simultaneously.

Out-group homogeneity bias makes people see members of out-groups as more alike than they really are. They are all the same. In-group members are seen as diverse individuals. This bias fuels stereotypes and prejudice. It also makes it easier to justify discrimination.

How out-groups form

• Competition for resources or status
• Historical conflict or trauma
• Cultural difference and lack of contact
• Political rhetoric that demonizes the other

Contact theory suggests that positive interaction between groups can reduce hostility. But contact alone is not enough. It works best when groups have equal status, shared goals, and institutional support. Otherwise, contact can reinforce divisions.