<P> In sociology and social psychology, an ingroup is a social group to which a person psychologically identifies as being a member . By contrast, an outgroup is a social group with which an individual does not identify . For example, people may find it psychologically meaningful to view themselves according to their race, culture, gender, age or religion . It has been found that the psychological membership of social groups and categories is associated with a wide variety of phenomena . </P> <P> The terminology was made popular by Henri Tajfel and colleagues during his work in formulating social identity theory . The significance of ingroup and outgroup categorization was identified using a method called the minimal group paradigm . Tajfel and colleagues found that people can form self - preferencing ingroups within a matter of minutes and that such groups can form even on the basis of seemingly trivial characteristics, such as preferences for certain paintings . </P> <P> The psychological categorization of people into ingroup and outgroup members is associated with a variety of phenomena . The following examples have all received a great deal of academic attention . </P>

Who introduced the term in group and out group