As immigration becomes increasingly central to public discourse and policymaking, understanding why individuals differ in their attitudes and responses to immigration and diversity is crucial given the significant political and social implications. Social theories explaining variation in sociopolitical attitudes and behaviours are well established, but recent research in social science genetics reveals that genetic differences contribute to a wide range of life outcomes, including educational attainment, aspects of one’s social environment, and political attitudes. These findings underscore the need to actively incorporate genetical information into social research.

This interdisciplinary dissertation investigates three key questions concerning public attitudes toward immigration and generalised trust, using a genetically informed perspective to account for both genetic confounding and individual-level heterogeneity. The analyses draw on a large cohort of Swedish twins, linked to rich survey data (2009–2010), register records, and molecular genetic information.

Paper 1 addresses the educational divide in immigration attitudes. While self-selection partly explains this divide, the findings suggest that higher formal education exerts a moderate liberalising effect. The study is the first to use genetic data to assess the role of education-related genetic predispositions in shaping immigration attitudes. 

Paper 2 examines generalised trust as a source of immigration attitudes, distinguishing it from prosociality — the willingness to help others — and controlling for twin-shared confounding. Trust is robustly associated with more open views on immigration, independently of prosociality, though primarily linked to support for immigrant admission.

Paper 3 offers new explanations concerning the debate over whether ethnic diversity compromises social cohesion. Focusing on residential interethnic exposure as a common form of everyday contact with diversity, it finds a modest negative association with trust in strangers, but no consistent links to outgroup negativity or social engagement. Moreover, this association is concentrated among individuals genetically predisposed to higher neuroticism. The influence of interethnic exposure is therefore limited in scope and dependent on individual psychological predispositions.

Collectively, these papers shed new light on the foundations of natives’ attitudes towards immigration and trust, and on broader debates surrounding immigration and social cohesion, while demonstrating how social science questions can be approached using genetically informed designs.