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Explaining divergent life outcomes in modern societies is a core issue within social science, and of key relevance for policy makers. This debate has long been defined by an uncompromising struggle between "nature" and "nurture", with social and political science mostly preferring environmental explanations for life outcomes such as educational attainment and political participation. The molecular genetics revolution is now providing new insights into the genetics of complex social outcomes, but much stands to be learned about how genetic influences on life outcomes can be conditioned by the environment. Moreover, and surprisingly, we still know rather little about how genetic insights impacts on citizens' perceptions and attitudes towards inequality and government intervention. Building this knowledge is crucial given the complex and contentious nature of debates concerning genetics and social behavior. This thesis contributes with new insights about the interplay between genetics and different types of environments, operating in the fascinating intersection between social science and molecular genetics. The thesis also contributes by exploring the moral and empirical implications of genetic explanations for social life outcomes. The thesis relies on Swedish administrative registers and original survey data.

Study I explores how historical political and institutional changes related to equality of opportunity can be reflected in the association between genetics and educational attainment. Studying Swedish twins born across the 20th century, the paper suggests that the influence of education-related genetic propensities on education have increased across time, while the socioeconomic stratification of genetic effects has also decreased. 

Study II investigates the interaction between education-related genetic propensities and proximal social environments in the shaping of political participation. Contributing to debates concerning inequalities in political participation, the study shows that the effects of genetic resources on voting are lower when family and neighbourhood characteristics are more favourable in terms of socioeconomic status and political engagement.

Study III explores the public understanding of genetic explanations for socioeconomic outcomes, using a survey experiment fielded in the United States and Sweden. Contrary to expectation, the study shows some evidence that citizens increase their beliefs in the effectiveness, and the fairness, of the government reducing socioeconomic differences, as a result of an increased knowledge about how genetics contribute to shaping such differences.  

For half a century, scholars have debated the societal implications of research that suggests genetic explanations for socioeconomic disparities. However, studies of whether and how such genetic explanations affect the attitudes of citizensare surprisingly limited. Using two identical, pre-registered survey experiments fielded in the United States (N=2003) and Sweden (N=2005), this study tests whether a short, twin study-based genetic explanation for income and education differencesleads to citizens adopting a lower perceived possibility, as well as a lower perceived fairness, of the government reducing socioeconomic differences. The results do not provide systematic evidence to this effect. Rather, there are indications that citizens increase their belief in the effectiveness, as well as in the fairness of government intervention. Most clearly, the treatment increased citizens’ support for a set of redistributive policy proposals, particularly in Sweden. Overall, however, the treatment effects appear to have been limited. This is likely attributable to the experimental manipulationbeing inadequate in magnitude. This study suggests that genetic explanations for socioeconomic differences do not necessarily have to cause a naturalization of inequality among citizens, but further research on this important topic is needed.

Spatial concentration is often thought to increase political engagement among minority groups by fostering intragroup contact and strengthening political group consciousness. This study evaluates this relationship with a focus on lesbians, gays, and bisexuals (LGB), extending existing research beyond ethnoracial minorities. Using Swedish population-wide register data, we identify over 20,000 LGB individuals and nearly 8 million comparable heterosexual peers and track their validated voter turnout across four parliamentary elections (1994–2022). To estimate the causal effect of neighborhood LGB concentration on turnout, we apply a triple-difference design leveraging fine-grained geolocation data. We find that increases in local LGB concentration are associated with higher turnout among LGB individuals relative to heterosexual neighbors experiencing the same neighborhood changes. The results provide rare causal evidence that minority spatial concentration can mobilize electoral participation, contributing to research on political geography, urban politics, and minority political behavior.

Previous research has found that political traits have some degree of genetic basis, but researchers have had less success unpacking the relationship between genes and political behavior. We propose an approach for examining this relationship that can overcome many of the limitations of previous research: polygenic indices (PGIs). PGIs are DNA-based individual-level variables that capture the genetic propensity to exhibit a given trait. We begin by outlining how PGIs are derived, how they can be utilized in conventional regression-based research, and how results should be interpreted. We then provide proof of concept, using data on over 50,000 individuals in four samples from the U.S. and Sweden to show that PGIs for health and psychological traits significantly predict measures of political participation, even within families. We conclude by outlining several ideas and providing empirical examples for researchers who may be interested in building on the PGI approach.

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.

The world has seen a massive increase in wealth and wealth inequality over the last decades. Given the skew in policy making towards the preferences of the wealthy, this raises the question of how individual wealth affects political participation. Approaching this question empirically is complicated by the fact that random variation in wealth is rare, and many factors that can bias the estimation of the relationship between wealth and participation are difficult to measure. We address the question using a Swedish discordant identical twin design with a) register-based wealth data, b) validated election turnout for multiple elections, and c) self-reported civic participation measures. This design allows us to rule out all shared confounders, such as genetics, family background and socialization, and shared networks. We find that even though wealthy individuals descriptively vote more often, a causal effect of wealth is not detectable, and may for civic participation even be negative.

New research indicates that genetic variants related to educational attainment influence individuals’ political participation. This suggests that political inequality of opportunity is partially rooted in an inequality in genetic resources. However, the possibility that these genetic influences are contingent on individuals’ environments, such that they are amplified or reduced by certain environmental characteristics, remains unexplored. Using longitudinal and geo-coded register data for a large sample of genotyped twins in the Swedish Twin Registry, this paper explores whether early-life proximal environments that are conducive to participation modifies the effects of individuals’ education-related genetic resources on voting, as measured by a polygenic index for educational attainment. The results suggest that the level of political engagement, and of SES, both within the family and within the neighbourhood, can reduce the effects of genetic resources on voting. This has implications for how we can direct policy to ameliorate genetic inequalities in political participation.

Interest in the role of genetics in influencing key life outcomes such as educational attainment has grown quickly. However, the question of whether genetic influences on educational attainment, on average as well as in conjunction with socioeconomic circumstances, are moderated by macro-level factors has not yet received sufficient attention. This study combines polygenic indices for educational attainment (EA PGI) with high-quality register data in a large sample of Swedish twins of European ancestry born 1920–1999. Employing both conventional between-family and within-family models, the analyses suggest that the influences of education-related genetic propensities on educational attainment have increased in Sweden during the twentieth century, a period featuring major expansions of the Swedish educational system, and decreasing economic inequality. The analyses also suggest that the degree to which socioeconomic background enhances genetic influences on education has decreased across cohorts. Genetic influences on education do not appear to have translated into increased genetic influences on income. Additionally, there is some evidence of floor and ceiling effects in the analyses of dichotomous educational outcomes.

Education is widely believed to predict attitudes toward immigration, but what causal relationship underlies this descriptive pattern? This research employs three distinct natural experiments and considers genetic factors to triangulate this relationship: Study 1 analyses discordant monozygotic twins; Study 2 assesses the impact of a Swedish education reform; and Study 3 analyses dizygotic twins with the use of a polygenic index for education, a DNA-based measure for genetic predispositions toward education. The results indicate that education does modestly promote open views toward immigration (Study 1), yet the reform’s effect remains uncertain (Study 2). Study 3 offers direct evidence of the effects of genetic predispositions and suggests that genetics related to education may influence attitudes beyond achieved educational attainment. These findings confirm the positive impact of education while pointing to the combined influence of genetic and social pathways in shaping immigration attitudes.

Early voting procedures boost voter participation and have therefore been suggested as institutional remedies for the problem of unequal turnout. Scholars have, however, raised concerns that making voting more convenient may actually lead to a less representative electorate. We contribute to this debate by leveraging large-scale Swedish registry data to analyze persons expecting a child around the time of the election. Our results indicate that politically engaged high-status voters are more likely to use the opportunity to vote in advance when faced with the risk of not being able to vote on election day. Given the large number of obstacles to election-day voting that individuals face throughout life, it is therefore conceivable that efforts to make voting more convenient and less costly for citizens may in the end lead to less representative electorates.