A model of egocentric social categorization (ESC-model) is presented. It predicts an asymmetry in the cognitive construal of ingroups and outgroups which is traced back to an egocentrism in the cognitive differentiation of the social world. The more specific assumptions are: (1) At the most basic level of cognitive differentiation, the perceiver distinguishes between the categories ME and NOT-ME. (2) This basic level categorization predicates an asymmetry in the cognitive construal of ingroup and out-group as social categories: The ingroup is construed as a heterogeneous aggregate of separate entities and the outgroup as a homogeneous social category. (3) Egocentric social categorization thus facilitates self-definition in terms of personal identity relative to self-definition in terms of social identity.

The ESC-model is highly relevant to research on perceived ingroup and outgroup homogeneity. Moreover, it alerts researchers to the possibility of ‘quasi-intergroup’ situations in which the outgroup, but not the ingroup, is a salient entity. This article also discusses the relationship between the ESC-model and self-categorization theory and points out some prospects for future research.