Self-Categorization and Autism: Exploring the Relationship Between Autistic Traits and Group Homogeneity

The Integrated Self-Categorization model of Autism (ISCA; Bertschy et al., 2019; Skorich & Haslam, 2021) argues that the theory of mind differences seen in autism arises from Enhanced Perceptual Functioning/Weak Central Coherence, via a dysfunctional self-categorization mechanism. The ISCA model also makes the novel prediction that phenomena that arise from self-categorization should also be affected in autistic people. In this article, we report three studies exploring this prediction in the context of one such phenomenon: Group homogeneity. We first measure participants’ autistic traits, then ask them to make homogeneity judgments of their ingroup alone or their outgroup alone (in Study 1, and in the Alone conditions of Studies 2a and 2b); or of their ingroup in comparison to their outgroup or their outgroup in comparison to their ingroup (in the Compare conditions of Studies 2a and 2b). As predicted, we find that: the degree of autistic traits negatively predicts ratings of group homogeneity; this relationship is mediated by social identification/self-categorization; and typical comparison-related homogeneity effects are strengthened at higher relative to lower levels of autistic traits. These studies provide convergent evidence for the ISCA model and suggest important avenues for well-being and social skills interventions for autistic people.