In sociology and social psychology, an in-group is a social group to which a person psychologically identifies as being a member. By contrast, an out-group is a social group with which an individual does not identify. People may for example identify with their peer group, family, community, sports team, political party, gender, religion, or nation. It has been found that the psychological membership of social groups and categories is associated with a wide variety of phenomena. The terminology was made popular by Henri Tajfel and colleagues during his work in formulating social identity theory. The significance of in-group and out-group categorization was identified using a method called the minimal group paradigm. Tajfel and colleagues found that people can form self-preferencing in-groups within a matter of minutes and that such groups can form even on the basis of completely arbitrary and invented discriminatory characteristics, such as preferences for certain paintings.
Associated phenomena
The psychological categorization of people into in-group and out-group members is associated with a variety of phenomena. The following examples have all received a great deal of academic attention.
In-group favoritism
This refers to the fact that under certain conditions, people will prefer and have affinity for one's in-group over the out-group, or anyone viewed as outside the in-group. This can be expressed in one's evaluation of others, linking, allocation of resources, and many other ways.
Out-group derogation
Discrimination between in-groups and out-groups is a matter of favoritism towards an in-group and the absence of equivalent favoritism towards an out-group. Out-group derogation is the phenomenon in which an out-group is perceived as being threatening to the members of an in-group. This phenomenon often accompanies in-group favoritism, as it requires one to have an affinity towards their in-group. Some research suggests that out-group derogation occurs when an out-group is perceived as blocking or hindering the goals of an in-group. It has also been argued that out-group derogation is a natural consequence of the categorization process.
Social influence
People have been shown to be differentially influenced by in-group members. That is, under conditions where group categorization is psychologically salient, people will shift their beliefs in line with in-group social norms.
This generally refers to the tendency of groups to make decisions that are more extreme than the initial inclination of its members, although polarization toward the most central beliefs has also been observed. It has been shown that this effect is related to a psychologically salient in-group and outgroup categorization.
Group homogeneity
Categorization of people into social groups increases the perception that group members are similar to one another. An outcome of this is the out-group homogeneity effect. This refers to the perception of members of an out-group as being homogenous, while members of one's in-group are perceived as being diverse, e.g. "they are alike; we are diverse”. This is especially likely to occur in regard to negative characteristics. Under certain conditions, in-group members can be perceived as being similar to one another in regard to positive characteristics. This effect is called in-group homogeneity.
In evolutionary psychology, in-group favoritism is seen as an evolved mechanism selected for the advantages of coalition affiliation. It has been argued that characteristics such as gender and ethnicity are inflexible or even essential features of such systems. However, there is evidence that elements of favoritism are flexible in that they can be erased by changes in social categorization. One study in the field of behavioural genetics suggests that biological mechanisms may exist which favor a coexistence of both flexible and essentialist systems.
