[4] The out-group homogeneity effect is part of a broader field of research that examines perceived group variability.
[6] An example of this phenomenon comes from a study where researchers asked 90 sorority members to judge the degree of within-group similarity for their own and 2 other groups.
One might think that people thought members of their own groups were more varied and different simply because they knew them better and thus have more information about ingroups,[9] but this is actually not the case.
Researchers have postulated that such an effect is present when viewing a group as homogeneous helps to promote in-group solidarity.
In an intergroup context the ingroup would also be predicted to be seen as comparatively homogeneous as the perceiver attends to the differences between "us" and "them" (in other words, depersonalization occurs).
[14] Another body of research looked at ingroup and outgroup homogeneity from the perspective of social identity theory.
[3] While complementary to the self-categorization theory account, this body of research was concerned more with specific homogeneity effects associated with the motivations of perceivers.
[17] Recent research also has reaffirmed that this effect of in-group homogeneity on in-group defining dimensions and out-group homogeneity on out-group defining dimensions may occur because people use their ratings of perceived group variability to express the extent to which social groups possess specific characteristics.