Peter K. Hatemi

Genetic and Environmental Transmission of Political Attitudes Over a Life Time

Recently political scientists have looked anew at the source of political preferences and find support for the heuristic that political attitudes and behaviors are influenced by endogenous factors. The present research attempts to characterize how the transmission of political orientations develops over the life course. Using longitudinal data collected on twins throughout childhood and adolescence combined with cross-sectional data from adult twins, the present study finds that genetic influences on political attitudes are absent prior to young adulthood. During childhood and adolescence, individual differences in political attitudes are accounted for by a variety of environmental influences with the role of shared “family” environment, including parental socialization, accumulating markedly between the ages of 9 and 17. However, at the point of early adulthood (in the early 20s), for those who left their parental home, there is evidence of a sizeable genetic influence on political attitudes which remains stable throughout adult life. The pattern of genetic transmission shows some similarity to an “impressionable years” model of attitude crystallization showing both the important influence of family and other shared environmental influences in adolescence and then an increased role of genetic factors as familial environmental influences diminish.

Is There a 'Party' in Your Genes?

Utilizing quantitative genetic models, the authors examine the sources of party identification and the intensity of that identification. The results indicate genes exert little, if any, influence on party identification, directly or indirectly through covariates. However, we find that genes appear to play a pivotal role in shaping the strength of an individual’s party identification. Together with recent examinations of political attitudes and vote choice, these findings begin to provide a more complete picture of the source of partisanship and the complex nature of the political phenotype.

A Genome-Wide Analysis of Liberal and Conservative Political Attitudes

The assumption that the transmission of social behaviors and political preferences is purely cultural has been challenged repeatedly over the last 40 years by the combined evidence of large studies of adult twins and their relatives, adoption studies, and twins reared apart. Variance components and path modeling analyses using data from extended families quantified the overall genetic influence on political attitudes, but few studies have attempted to localize the parts of the genome which accounted for the heritability estimates found for political preferences. Here, we present the first genome-wide analysis of Conservative-Liberal attitudes from a sample of 13,000 respondents whose DNA was collected in conjunction with a 50-item sociopolitical attitude questionnaire. Several significant linkage peaks were identified and potential candidate genes discussed.

The Politics of Mate Choice

Recent research has found a surprising degree of homogeneity in the personal political communication network of individuals but this work has focused largely on the tendency to sort into likeminded social, workplace, and residential political contexts. We extend this line of research into one of the most fundamental and consequential of political interactions—that between sexual mates. Using data on thousands of spouse pairs in the United States, we investigate the degree of concordance among mates on a variety of traits. Our findings show that physical and personality traits display only weakly positive and frequently insignificant correlations across spouses. Conversely, political attitudes display interspousal correlations that are among the strongest of all social and biometric traits. Further, it appears the political similarity of spouses derives in part from initial mate choice rather than persuasion and accommodation over the life of the relationship.

Modeling extended twin family data I: description of the Cascade model.

The classical twin design uses data on the variation of and covariation between monozygotic and dizygotic twins to infer underlying genetic and environmental causes of phenotypic variation in the population. By using data from additional relative classes, such as parents, extended twin family designs more comprehensively describe the causes of phenotypic variation. This article introduces an extension of previous extended twin family models, the Cascade model, which uses information on twins as well as their siblings, spouses, parents, and children to differentiate two genetic and six environmental sources of phenotypic variation. The Cascade also relaxes assumptions regarding mating and cultural transmission that existed in previous extended twin family designs. The estimation of additional parameters and relaxation of assumptions is potentially important, not only because it allows more fine-grained descriptions of the causes of phenotypic variation, but more importantly, because it can reduce the biases in parameter estimates that exist in earlier designs.

Transmission of Attitudes Toward Abortion and Gay Rights: Effects of Genes, Social Learning and Mate Selection

The biological and social transmission of attitudes toward abortion and gay rights are analyzed in a large sample of adult twins, siblings, and their parents. We present a linear model for family resemblance allowing for both genetic and cultural transmission of attitudes from parents to offspring, as well as phenotypic assortative mating (the tendency to marry like) and other environmental sources of twin and sibling resemblance that do not depend on the attitudes of their parents. The model gives a close fit to the patterns of similarity between relatives for the two items. Results are consistent with a substantial role of genetic liability in the transmission of both attitudes. Contrary to the dominant paradigm of the social and political sciences, the kinship data are consistent with a relatively minor non-genetic impact of parental attitudes on the development of adult attitudes in their children. By contrast, the choice of mate is a social action that has a marked impact on the polarization of social attitudes and on the long-term influence that parents exert upon the next generation.

Population composition, public policy, and the genetics of smoking.

In this article, we explore the effect of public policy on the extent to which genes influence smoking desistance. Using a sample of adult twins (nmz = 363, ndz = 233) from a large population registry, we estimate Cox proportional hazards models that describe similarity in the timing of smoking desistance among adult twin pairs. We show that identical twin pairs are significantly more likely to quit smoking within a similar time frame compared with fraternal twin pairs. Importantly, we then show that genetic factors for smoking desistance increase in importance following restrictive legislation on smoking behaviors that occurred in the early and mid-1970s. These findings support the social push perspective and make important contributions to the social demography and genetic epidemiology of smoking as well as to the gene-environment interaction literatures.

Integrating social science and genetics: news from the political front.

There has been growing interest in the use of genetic models to expand the understanding of political preferences, attitudes, and behaviors. Researchers in the social sciences have begun incorporating these models and have revealed that genetic differences account for individual differences in political beliefs, behaviors, and responses to the political environment. The first Integrating Genetics and the Social Sciences Conference, held at Boulder, Colorado in May of 2010, brought together these researchers. As a result, we jointly review the last 5 years of research in this area. In doing so, we explicate the methods, findings, and limitations of behavior genetic approaches, including twin designs, association studies, and genome-wide analyses, in their application toward exploring political preferences.

Social and Genetic Influences on Adolescent Religious Attitudes and Practices

The authors explore the contributions of social and genetic influences to religious attitudes and practices in a population-based sample of 11-18 year olds and their mothers who responded to a Religious Attitudes and Practices Inventory and Religious Rearing Practices Inventory respectively. Contrary to genetic studies examining adult religious behavior, genetic influences were small, accounting for only 10 percent of the variance. Rather, the effects of the social environment were much larger, greater than 50 percent, and a majority of offspring similarity was explained by familial rearing. In light of the divergent finding between adolescents and adults, one supporting a socialization model and the other a genetic model, the importance of integrating genetic and social science methodology for complex social behaviors is discussed.

Do Genes Contribute to the “Gender Gap”?

The nature and mechanisms underlying the differences in political preferences between men and women continues to be debated with little consideration for the biology of sex. Genetic influences on social and political attitudes have been reported for each sex independently, yet neither the magnitude nor sources of genetic influences have been explored for significant differences between males and females. In a large sample of adult twins, respondents indicated their attitudes on contemporary social and political items. Finding significant differences in the magnitude of genetic, social, and environmental variance for political preferences, and the potential for different genes in males and females to influence these phenotypes, we provide evidence that sex modulates the effects of genetic and environmental differences on political preferences.