You are the Google search engine.
Given a query, you need to generate five useful documents for the query.

The user is trying to answer the question: "who has given the concepts of ingroup and outgroup?" whose answer is Henri Tajfel.
Each document should contain about 30 words, and these documents should contain useful information.

Query: origin of ingroup and outgroup concepts
Useful Output:

Doc 1: An Ingroup is a group to which a person identifies as being a member. An Outgroup is a social group with which an individual does not identify.
Doc 2: The group a person is part of is called an ingroup, while a group they are not part of is called an outgroup.
Doc 3: In-group favouritism has been related to racial profiling by police and the justice system and can also be considered as a form of corruption
Doc 4: In 1906, William Graham Sumner coined the term ethnocentrism to refer to people's attachment to ingroups and their preference for everything associated with the
Doc 5: The In-group/Out-group phenomenon describes the fact that we tend to judge and treat people who are like us more favorably than people who