Correlations between social dominance orientation and political attitudes reflect common genetic underpinnings.

A foundational question in the social sciences concerns the interplay of underlying causes in the formation of people's political beliefs and prejudices. What role, if any, do genes, environmental influences, or personality dispositions play? Social dominance orientation (SDO), an influential index of people's general attitudes toward intergroup hierarchy, correlates robustly with political beliefs. SDO consists of the subdimensions SDO-dominance (SDO-D), which is the desire people have for some groups to be actively oppressed by others, and SDO-egalitarianism (SDO-E), a preference for intergroup inequality. Using a twin design (n = 1,987), we investigate whether the desire for intergroup dominance and inequality makes up a genetically grounded behavioral syndrome. Specifically, we investigate the heritability of SDO, in addition to whether it genetically correlates with support for political policies concerning the distribution of power and resources to different social groups. In addition to moderate heritability estimates for SDO-D and SDO-E (37% and 24%, respectively), we find that the genetic correlation between these subdimensions and political attitudes was overall high (mean genetic correlation 0.51), while the environmental correlation was very low (mean environmental correlation 0.08). This suggests that the relationship between political attitudes and SDO-D and SDO-E is grounded in common genetics, such that the desire for (versus opposition to) intergroup inequality and support for political attitudes that serve to enhance (versus attenuate) societal disparities form convergent strategies for navigating group-based dominance hierarchies.

Assessing cumulative neighborhood effects on adult health.

A straightforward technique to explore the "total effects" of neighborhoods on health outcomes is to compare the degree of similarity of outcomes of neighbors with those of non-neighbors. Several issues arise in interpreting these estimates around spatial and temporal definitions of "neighbors" and life course mobility patterns. Indeed, much work uses "cross- sectional neighbors," which makes the interpretation of the estimates unclear because they combine short-term effects (for movers) and long-term effects (for stayers). This paper contributes to the literature by assessing the importance of measuring neighbor mobility as well as neighborhood selection. Using the Panel Study of Income Dynamics, we examine the extent to which having longitudinal measures of "neighbors" shapes estimates of neighborhood effects, and also use a negative test of neighborhood effects to assess the importance of neighborhood selection. Specifically, we estimate similarity in self-rated health of adults over 30 years old who live in the same county over various periods of time and find that "cross-sectional" neighbor definitions may understate neighborhood effect estimates by as much as 35%. However, when we contrast these health estimates with contemporaneous neighborhood "effects" on completed education, we find that much of the "understated" effects on health are likely related to selection effects rather than causal effects of neighborhoods.

Socioeconomic Status and Adolescent Alcohol Involvement: Evidence for a Gene-Environment Interaction.

OBJECTIVE: Adolescence is an optimal developmental stage for examining the interplay of environmental factors and the genetic risk for alcohol involvement. The current study aimed to examine how socioeconomic status might interact with genetic risk for alcohol involvement among adolescents. METHOD: A total of 839 same-sex adolescent twin pairs (509 monozygotic and 330 dizygotic) from the 1962 National Merit Twin Study completed a questionnaire containing items assessing alcohol involvement. Twins were approximately 17 years old at the time of participation. Parents provided reports of family income and educational attainment. Models were fit examining parental education and family income as moderators of genetic and environmental influences on alcohol use. RESULTS: There was evidence for moderation of genetic and environmental influences on alcohol involvement by family income. For twins with the lowest levels of family income, genetic and shared environmental influences accounted for 50% and 26% of the variance in alcohol involvement, respectively, compared with 2% and 67% of the variance among those at the highest level of income. CONCLUSIONS: These findings suggest that etiological influences on alcohol involvement vary as a function of an adolescent's socioeconomic status.

On the genetic and environmental sources of social and political participation in adolescence and early adulthood.

Political participation (POP), social participation (SOP), and political interest (PI) are important indicators of social status and social inequality. Previous studies on related trait differences yielded genetic and environmental contributions. However, focusing on adult samples, classical twin designs, and convenience samples often restricts parameter estimation and generalizability, and limits the understanding of age differences. We investigated sources of variance in POP, SOP, and PI in late adolescence and early adulthood with an extended twin family design (ETFD). We analyzed data from over 2,000 representative German twin families. Individual environments not shared by family members reflected the major source of variance for all variables, but genetic influences were also pronounced. Genetic effects were mostly higher for young adults, whereas effects of twins' shared environment were significant in adolescence. Our study deepens the understanding of the interplay between genetic and environmental factors in shaping differences in young persons' integration in society.

Negative social comparisons and psychosis proneness in a healthy adolescent population.

There is growing evidence of an association between negative social comparisons (NSC) and both psychosis, and psychosis proneness. The majority of the work thus far, however, has focused largely on one type of NSC, namely, social rank. Whilst social rank is clearly an important factor, an individual's perception of belonging is likely also of importance; particularly, when considering individuals from collectivistic cultures such as China, where greater emphasis is placed on fitting into the group. There is also limited research investigating what factors may contribute towards the relationship between NSC and psychosis proneness, and to what extent this relationship may be due to common familial factors. To address these issues, we examined whether (1) Social rank and perceived belonging predict negative, positive and depressive psychotic experiences in a Chinese, adolescent, twin and sibling population, (2) coping styles moderate the impact of these relationships and (3), there is a familial association between NSC and psychosis proneness. Both social rank and perceived belonging were found to predict the negative and depressive dimensions of psychosis. These relationships were moderated by problem-focused coping styles. Interestingly, the association between perception of belonging, and negative psychotic experiences was familial-and stronger in Monozygotic twins-indicating perhaps shared aetiology due to common genes. Our findings highlight NSC as potential vulnerability markers for negative and depressive psychotic experiences, and suggest potentially different aetiological pathways amongst different NSC and different psychotic experiences. On a clinical level, our findings emphasize the need to consider coping styles when treating at-risk individuals.

The genetic and environmental foundations of political, psychological, social, and economic behaviors: a panel study of twins and families.

Here we introduce the Genetic and Environmental Foundations of Political and Economic Behaviors: A Panel Study of Twins and Families (PIs Alford, Hatemi, Hibbing, Martin, and Smith). This study was designed to explore the genetic and environmental influences on social, economic, and political behaviors and attitudes. It involves identifying the psychological mechanisms that operate on these traits, the heritability of complex economic and political traits under varying conditions, and specific genetic correlates of attitudes and behaviors. In addition to describing the study, we conduct novel analyses on the data, estimating the heritability of two traits so far unexplored in the extant literature: Machiavellianism and Baron-Cohen's Empathizing Quotient.

Socioeconomic status and sick leave granted for mental and somatic disorders: a prospective study of young adult twins.

BACKGROUND: Low socioeconomic status (SES), indicated by low income and education, has consistently been found to be a strong predictor of sick leave. Several possible pathways from SES to sick leave have been described in previous literature, but there are also evidence indicating that the association can be confounded by common underlying factors. This study utilizes a population-based sample of employed young adult twins to estimate (i) the degree to which education and income are prospectively related to sick leave granted for mental, somatic, and any disorder, and (ii) whether these associations are confounded by familial factors. METHODS: Registry data on educational attainment and income at age 30 and subsequent sick leave were available for 6,103 employed young adult twins, among which there were 2,024 complete twin pairs. The average follow-up time was 6.57 years. Individual-level associations and fixed effects within twin pairs were estimated. RESULTS: Low education and income were associated with sick leave granted for both mental and somatic disorders, and with sick leave granted for any disorder. Associations were attenuated within dizygotic twin pairs and reduced to non-significance within monozygotic twin pairs, suggesting influence of familial factors on the associations between SES and sick leave. CONCLUSIONS: Low SES is associated with a higher level of sick leave granted for both mental and somatic disorders among young adults, but these associations are confounded by factors that are common to co-twins. Education and income are therefore not likely to strongly affect sick leave in young adulthood.

Midlife dietary patterns and mortality in the population-based study of Swedish twins.

BACKGROUND: We examined midlife dietary patterns in relation to (1) sociodemographic and health-related characteristics and (2) survival. METHODS: A two-step cluster analysis of a 12-item food questionnaire was used to derive dietary patterns in a cohort of 16 649 members of the Swedish Twin Registry, a prospective, population-based study of twins. The average age at baseline (1967) was 55.5 years; the follow-up for all-cause mortality extended until 2011 (26.8±12.35 years or 345,127 person-years) via death records. RESULTS: Four dietary patterns (classes) distinguishable by demographic and health characteristics emerged: Moderate Intake and Starch Diet (Class 1), Moderate Intake Diet with Low Flour-Based Foods (Class 2), Meat and Starch Diet (Class 3) and Low Meat Intake Diet (Class 4). Membership in Class 3 was associated with 7% increased risk of mortality compared with Class 2 independent of baseline age, cohort, sex and body mass index. These results were mostly explained by sociodemographic and lifestyle factors. When follow-up was restricted to those in the study for 20+ years, both Classes 1 and 3 conferred increased risk of mortality compared with Class 2, independent of covariates. Analyses conducted within twin pairs revealed similar results. CONCLUSIONS: Midlife diet over-represented by meat and starch-based foods may increase the risk of mortality, whereas the diet low in starch may be beneficial. These results appear to be independent of factors shared by twins, as well as at least partially a function of social and lifestyle factors, particularly marital status and smoking.

Intellectual interest mediates gene × socioeconomic status interaction on adolescent academic achievement.

Recent studies have demonstrated that genetic influences on cognitive ability and academic achievement are larger for children raised in higher socioeconomic status (SES) homes. However, little work has been done to document the psychosocial processes that underlie this Gene × Environment interaction. One process may involve the conversion of intellectual interest into academic achievement. Analyses of data from 777 pairs of 17-year-old twins indicated that Gene × SES effects on achievement scores can be accounted for by stronger influences of genes for intellectual interest on achievement at higher levels of SES. These findings are consistent with the hypothesis that higher SES affords greater opportunity for children to seek out and benefit from learning experiences that are congruent with their genetically influenced intellectual interests.

Gene-by-socioeconomic status interaction on school readiness.

In previous work with a nationally representative sample of over 1,400 monozygotic and dizygotic twins born in the US, Tucker-Drob et al. (Psychological Science, 22, 125-133, 2011) uncovered a gene × environment interaction on scores on the Bayley Short Form test of mental ability (MA) at 2 years of age-higher socioeconomic status (SES) was associated not only with higher MA, but also with larger genetic contributions to individual differences in MA. The current study examined gene × SES interactions in mathematics skill and reading skill at 4 years of age (preschool age) in the same sample of twins, and further examined whether interactions detected at 4 years could be attributed to the persistence of the interaction previously observed at 2 years. For early mathematics skill but not early reading skill, genetic influences were more pronounced at higher levels of SES. This interaction was not accounted for by the interaction observed at 2 years. These findings indicate that SES moderates the etiological influences on certain cognitive functions at multiple stages of child development.

Preschools reduce early academic-achievement gaps: a longitudinal twin approach.

Preschools may reduce inequalities in early academic achievement by providing children from disadvantaged families with higher-quality learning environments than they would otherwise receive. In this study, longitudinal data from a nationally representative sample of more than 600 twin pairs were used to estimate the contributions of genes, the shared environment, and the nonshared environment to cognition and achievement scores in children enrolled versus not enrolled in preschool. Attending preschool at age 4 was associated with reductions in shared environmental influences on reading and math skills at age 5, but was not associated with the magnitude of shared environmental influences on cognition at age 2. These prospective effects were mediated by reductions in achievement gaps associated with minority status, socioeconomic status, and ratings of parental stimulation of cognitive development. Lower socioeconomic status was associated with lower rates of preschool enrollment, which suggests that the very children who would benefit most from preschools are the least likely to be enrolled in them.

Gene-environment processes linking aggression, peer victimization, and the teacher-child relationship.

Aggressive behavior in middle childhood is at least partly explained by genetic factors. Nevertheless, estimations of simple effects ignore possible gene-environment interactions (G × E) or gene-environment correlations (rGE) in the etiology of aggression. The present study aimed to simultaneously test for G × E and rGE processes between aggression, on the one hand, and peer victimization and the teacher-child relationship in school, on the other hand. The sample comprised 124 MZ pairs and 93 DZ pairs assessed in Grade 1 (mean age = 84.7 months). Consistent with rGE, children with a presumed genetic disposition for aggression were at an increased risk of peer victimization, whereas in line with G × E, a positive relationship with the teacher mitigated the genetically mediated expression of aggression.

A 35-year longitudinal assessment of cognition and midlife depression symptoms: the Vietnam Era Twin Study of Aging.

OBJECTIVE: To determine whether early adult cognitive ability is a risk factor for depressive symptoms in midlife and how genetic and environmental influences explain the association and to examine cross-sectional relationships between depressive symptoms and specific cognitive abilities at midlife. DESIGN: A 35-year longitudinal and cross-sectional twin study of cognitive aging. SETTING: Large multicenter study in the United States. PARTICIPANTS: One thousand two hundred thirty-seven male twins aged 51 to 60 years. MEASUREMENTS: At the age of 20 years and midlife, participants completed the same version of a general cognitive ability test (Armed Forces Qualification Test [AFQT]). Midlife testing included an extensive neurocognitive protocol assessing processing speed, verbal memory, visual-spatial memory, working memory, executive function, and visual-spatial ability. Participants completed the Center for Epidemiologic Studies Depression Scale before cognitive testing and provided health and life style information during a medical history interview. RESULTS: Lower age 20 AFQT scores predicted higher levels of depressive symptoms at age 55 years (r = -0.16,p <0.001). In bivariate twin modeling, 77% of the correlation between early cognitive ability and midlife depressive symptoms was due to shared genetic influences. Controlling for current age, age 20 AFQT, and nonindependence ofobservations, depressive symptoms were associated with worse midlife AFQT scores and poorer performance in all cognitive domains except verbal memory. CONCLUSION: Results suggest that low cognitive ability is a risk factor for depressive symptoms; this association is partly due to shared genetic influences. Crosssectional analyses indicate that the association between depressive symptoms and performance is not linked to specific cognitive domains.

Genetic and environmental influences on internalizing psychopathology vary as a function of economic status.

BACKGROUND: Different theories of the link between socio-economic status (SES) and mental illness have been postulated. In particular, two theories of this association, social causation and social selection, differ in the implied causal pathway. The authors employ behavior genetic modeling to consider evidence for both social selection and social causation in the relationship between income variation and internalizing disorders. METHOD: Behavior genetic modeling was used to estimate the presence of gene-environment interaction (GxE, social causation) in the presence of gene-environment correlation (rGE, social selection). Participants were members of a sample of 719 twin pairs from the Midlife in the United States study. Four internalizing (INT) syndromes were assessed: major depression (MD); generalized anxiety disorder (GAD); panic attacks (PA); neuroticism (N). SES was measured with total family household income. RESULTS: One factor best accounted for the variance shared between MD, GAD, PA and N. The etiology of variation in INT changed from high to low levels of income, with unique environmental factors playing a larger role in INT variation at lower levels of income. Across levels of income, rGE between income and INT was modest (low income ra=0.39 to high income ra=0.54), implying a selection process operating through genetic effects linking lower income with INT psychopathology. CONCLUSIONS: Findings support social causation by suggesting that low income contributes significantly to environmental variation in INT. Modest support was found for social selection, but should be extended using longitudinal designs. Effective interventions for internalizing psychopathology may differ depending on income.

Differential age and sex effects in the assessment of major depression: a population-based twin item analysis of the DSM criteria.

A twin item factor analytic model was developed to test for the presence of noninvariant age, sex, and age by sex interaction effects on the individual DSM-III-R criteria for major depression (MD). Based on 1-year reports, six of the nine MD criteria and duration requirement were found to have covariate factor loading and/or threshold effects that significantly deviated from their corresponding factor level expectations. A significant age effect was found for the binary duration variable factor loading. The 'loss of interest', 'weight problems' and 'psychomotor problems' criteria all displayed forms of threshold only effects. 'Depressed mood', 'fatigue', and 'feeling worthless' had more complex patterns that included both factor loading and threshold effects. A significant factor age by sex interaction effect indicating an increasing female mean difference with age was found to be largely associated with the presence of differential threshold covariate effects. Disagreement between estimated factor scores and DSM-derived affected vs. unaffected classification was approximately 1.3%. Status on the duration requirement was found to be the one feature common to all discrepancies. The MD criteria set provided maximum information for calibrating MD factor scores in the scale region where discrepancies occurred. The dimensional modeling results are discussed in the broader context of epidemiological research and clinical assessment of major depression.

Are attitudes towards economic risk heritable? Analyses using the Australian twin study of gambling.

Abstract This study employs multiple regression models based on DeFries and Fulker (1985), and a large sample of twins, to assess heritability in attitudes towards economic risk, and the extent to which this heritability differs between males and females. Consistent with Cesarini et al. (2009), it is found that attitudes towards risk are moderately heritable, with about 20 percent of the variation in these attitudes across individuals being linked to genetic differences. This value is less than one-half the estimates reported by Zyphur et al. (2009) and Zhong et al. (2009). While females are more risk averse than males, there is no evidence that heritability in attitudes towards risk differs between males and females. Even though heritability is shown to be important to economic risk-taking, the analyses suggest that multivariate studies of the determinants of attitudes towards risk which to not take heritability into consideration still provide reliable estimates of the partial effects of other key variables, such as gender and educational attainment.

Four-dimensional sonographic assessment of inter-twin contact late in the first trimester.

OBJECTIVE: To evaluate the total number of inter-twin contacts between monochorionic diamniotic (MD) and dichorionic diamniotic (DD) twins using four-dimensional (4D) sonography late in the first trimester of pregnancy. METHOD: Six MD and 8 DD pregnancies were studied for 30 minutes with 4D sonography at 10-11 and 12-13 weeks of gestation. A total of 10 types of inter-twin contact was evaluated. RESULTS: There was a significant difference in the total number of all contacts between MD and DD twins at the 10-11 weeks of gestation (P<0.05). There was also a significant difference in the total number of contacts between 10-11 and 12-13 weeks of gestation in DD twins (P<0.05). CONCLUSION: Four-dimensional sonography provides a means of evaluating inter-twin contact in the first trimester of pregnancy and could be an accurate and reliable tool in studies of inter-twin behavior.

Sex differences and science: the etiology of science excellence.

BACKGROUND: Are there sex differences in the etiology of high performance in science in childhood that could contribute to the under-representation of women in scientific careers? In this study the relative contributions of genetic and environmental influences on high performance in science in both boys and girls were assessed using standard twin analyses. METHODS: The sample included 3000 twin pairs from the UK Twins Early Development Study (TEDS). Science performance ratings based on the UK National Curriculum were collected from teachers when the twins were 9, 10 and 12 years old. Science excellence was defined as performing above the 85th percentile. Sex-limitation liability threshold models were used to assess sex differences in etiology. RESULTS: We found no evidence for quantitative or qualitative sex differences in the etiology of science excellence, which was moderately heritable (30-50%), and influenced by both shared (40-56%) and non-shared (10-13%) environmental influences. CONCLUSIONS: Although boys and girls do not differ genetically in relation to school science performance per se, the under-representation of women in scientific careers may be due to attitudes rather than aptitudes.

Twins' temperament: early prenatal sonographic assessment and postnatal correlation.

OBJECTIVE: To study inter-twin differences in activity during early pregnancy and to examine their relationship to subsequent infant twins' temperament. STUDY DESIGN: Measures of fetal motor activity (frequency, duration and number of movements) were collected from 26 twin pairs during ultrasound nuchal translucency scan at late first trimester and early second trimester (11 to 14 weeks gestation). In twenty-two patients, the twins were dizygotic (dichorionic); of them, 13 twin pairs were of different sexes, five were both females and four were both males. Of the four monozygotic twin pregnancies, two were dichorionic and two were monochorionic, three were both females.The more active fetus in each pair was noted according to the position and/or sex without reporting to parents. Reported maternal perception of the more active twin was documented at the mid-trimester anatomical scan. Maternally reported postnatal temperament data of the infants were collected at 3 and 6 months, using Rothbarts' Infant Behavior Questionnaire (IBQ). RESULTS: After birth, maternal reports on infants' temperament and the more active twin in each pair were in good correlation with prenatal inter-twin differences in activity. The receiver operating characteristic (ROC) curves shows a better performance of ultrasound compared with maternal perception in prediction of the more active twin. CONCLUSIONS: The features of fetal neurobehavioral activity provide the basis for individual differences in twins' activity in infancy. Differences in activity in early pregnancy even before the emergence of fetal behavioral patterns were followed by temperamental differences postnatally.

Socioeconomic status and social support following illicit drug use: causal pathways or common liability?

The negative social attributes associated with drug use and abuse/dependence may arise as a result of shared genetic or environmental factors rather than through causal pathways. To evaluate this possibility, structured interviews were conducted for 3969 male and female twins from the Mid-Atlantic Twin Registry and evaluations of their socioeconomic status (SES), social interactions, and use of drugs were obtained. Drug involvement was categorized as never used, tried, or met criteria for abuse or dependence. A co-twin control design was implemented using hierarchical linear modeling to assess whether twins who used drugs experienced lower SES and social support than non-using co-twins. Poorer social functioning in the drug-exposed twin is consistent with a causal relationship, while similar functioning in the drug exposed versus naive twins imply shared genetic or common environmental factors. Use of drugs was not significantly related to any SES measures. However, education and job status appear to share genetic influences with drug abuse/dependence. Lower income was not related to abuse/dependence of drugs. Negative interactions with friends and relatives share genetic factors with use of drugs, but the escalation from trying drugs to abusing them appears to generate discord between the abuser and friends and relatives in a causal fashion. These results indicate that presumptive causal influences of drug abuse/dependence on low SES may actually be mediated by shared genes. Drug use and social discord also appear to have shared genetic factors, but increased levels of drug involvement seem to causally influence social interactions.