Neural Correlates of Social Group Perception - Mapping Perceived Social Categories in Brain Activation

Abstract

This thesis investigates the cognitive and neural mechanisms underpinning the perception of group homogeneity and the similarity between individuals belonging to the same or different social groups. Across three empirical studies, it explores how social identity and categorization influence both behavioral judgments and brain activation patterns associated with perceived similarity. <br/> Study 1 replicates and extends foundational work on Optimal Distinctiveness Theory, testing how identity threat modulates perceived similarity and stereotypicality in in-group and out-group evaluations. Despite using both group-based and individual-based tasks, the study found only partial support for the predicted increase in perceived outgroup homogeneity, while revealing nuanced differences based on measurement type and participant identification strength. Study 2 introduces a novel pairwise similarity rating paradigm to quantify fine-grained behavioral ratings of perceived similarity between individuals belonging to two social groups. The study establishes this method's effectiveness in measuring social categorization of individuals and demonstrates how information about group membeship of individuals influence perceived similarity judgments between these individuals, even on traits which are indirectly related to the group membeship. Study 3 combines behavioral similarity measures with fMRI to identify brain regions encoding social categorization. Using representational similarity analysis (RSA), it reveals that the right orbitofrontal cortex, bilateral inferior temporal gyri,and the right inferior frontal and bilateral middle frontal gyri are sensitive to social group and reflect changes in perceived similarity induced by social categorization. <br/> Together, these studies advance our understanding of how the human brain dynamically constructs and updates social similarity representations. The findings highlight the interplay between identity processes, cognitive evaluations, and neural coding, contributing to theories of social cognition and the neural basis of categorization.