Abstract
This chapter examines the psychosociological foundations of intergroup discrimination through the lens of social identity theory (SIT), with a particular focus on how domain-relevant self-esteem and perceived threats to group value shape discriminatory behavior. Drawing on two experimental studies, the authors explore how individuals within both minimal and realistic social categories respond to identity threat-offering insights into the mechanisms that underlie political polarization, symbolic leadership, and civic belonging in the United States. Experiment 1 employed a minimal group paradigm and found that participants exhibited increased verbal self-esteem-identified as central to their ingroup identity-following acts of discrimination. Participants with low public collective self-esteem (CSE), who believed their ingroup was negatively evaluated by an outgroup, demonstrated significantly heightened bias. Experiment 2 extended these findings to real-world national categories (New Zealanders vs. Australians), revealing that discriminatory behavior (i.e., allocation of white noise to the outgroup) led to elevated physical self-esteem, particularly among those with low public CSE who perceived their national identity as devalued. Overall, these findings suggest that self-esteem regulation-especially in domains salient to the ingroup-plays a pivotal role in both subtle and overt forms of intergroup bias. In the context of American governance, such mechanisms help explain how presidential rhetoric, policy framing, and symbolic representation can activate or attenuate identity-based divisions. The chapter underscores the importance of understanding psychosociological group dynamics when evaluating leadership influence on belonging, exclusion, and the architecture of social cohesion in a polarized political landscape.