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Longstanding interest has been directed toward the etiology of sociopolitical attitudes. Personality traits have been posited as antecedents; however, most work addressing such links has been limited to cross-sectional study designs. The current study used data from two large (both Ns > 8,700), longitudinal cohorts of individuals from the United Kingdom who were parent-assessed on a measure of temperament (assessing anxiety, conduct problems, and hyperactivity) at age 5 or 7 years and on a range of sociopolitical attitudes at age 30 or 33 years. In both cohorts, higher levels of childhood conduct problems predicted higher levels of economic and political discontent in adulthood. These associations were still evident when controlling for sex, childhood intelligence, and parental social class. In both cohorts, this pathway was partially mediated by educational attainment and achieved social class. These findings are consistent with the perspective that early-life temperament gives rise to adult political sentiment.

Studies of intelligence in children reveal significantly higher heritability among groups with high socioeconomic status (SES) than among groups with low SES. These interaction effects, however, have not been examined in adults, when between-families environmental effects are reduced. Using 1,702 adult twins (aged 24–84) for whom intelligence assessment data were available, we tested for interactions between childhood SES and genetic effects, between-families environmental effects, and unique environmental effects. Higher SES was associated with higher mean intelligence scores. Moreover, the magnitude of genetic influences on intelligence was proportional to SES. By contrast, environmental influences were constant. These results suggest that rather than setting lower and upper bounds on intelligence, genes multiply environmental inputs that support intellectual growth. This mechanism implies that increasing SES may raise average intelligence but also magnifies individual differences in intelligence.

In-group favoritism is ubiquitous and associated with intergroup conflict, yet is little understood from a biological perspective. A fundamental question regarding the structure of favoritism is whether it is inflexibly directed toward distinct, “essentialist” categories, such as ethnicity and race, or is deployed in a context-sensitive manner. In this article, we report the first study (to our knowledge) of the genetic and environmental structure of in-group favoritism in the religious, ethnic, and racial domains. We contrasted a model of favoritism based on a single domain-general central affiliation mechanism (CAM) with a model in which each domain was influenced by specific mechanisms. In a series of multivariate analyses, utilizing a large, representative sample of twins, models containing only the CAM or essentialist domains fit the data poorly. The best-fitting model revealed that a biological mechanism facilitates affiliation with arbitrary groups and exists alongside essentialist systems that evolved to process salient cues, such as shared beliefs and ancestry.