Left or right? Sources of political orientation: the roles of genetic factors, cultural transmission, assortative mating, and personality

In this study, we used an extended twin family design to investigate the influences of genetic and cultural transmission as well as different sources of nonrandom mating on 2 core aspects of political orientation: acceptance of inequality and rejecting system change. In addition, we studied the sources of phenotypic links between Big Five personality traits and political beliefs using self- and other reports. Data of 1,992 individuals (224 monozygotic and 166 dizygotic twin pairs, 92 unmatched twins, 530 spouses of twins, 268 fathers, and 322 mothers) were analyzed. Genetically informative analyses showed that political attitudes are genetically but not environmentally transmitted from parents to offspring and that a substantial proportion of this genetic variance can be accounted for by genetic variance in personality traits. Beyond genetic effects and genotypic assortative mating, generation-specific environmental sources act to increase twins' and spouses' resemblance in political beliefs. The results suggest multiple sources of political orientations in a modern democracy.     

Covariance structure of neuroticism and agreeableness: a twin and molecular genetic analysis of the role of the serotonin transporter gene

The Revised NEO Personality Inventory domains of Neuroticism and Agreeableness are considered factorially distinct despite several intercorrelations between these domains. The genetic correlation, an index of the degree to which these intercorrelations are caused by genetic influences, was estimated using data from 913 monozygotic and 562 dizygotic volunteer twin pairs from Canada, Germany, and Japan. The serotonin transporter gene, 5-HTTLPR, was assayed in a sample of 388 nontwin sibling pairs from the United States to determine the contribution of the serotonin transporter locus to the covariation between the Neuroticism and Agreeableness scales. In all four samples, genetic influences contributed to the covariance of Neuroticism and Agreeableness, with the serotonin transporter gene accounting for 10% of the relationship between these domains.     

Predictors of treatment outcome for youth receiving intensive residential treatment for obsessive–compulsive disorder (OCD)

ABSTRACT

Little is known about the predictors of outcome from intensive residential treatment of OCD. This study aimed to examine age, gender, and baseline OCD severity, as well as measures of comorbid anxiety and depressive, internalizing/externalizing, and inattention symptoms, as predictors of treatment outcome in adolescents receiving intensive residential treatment for OCD.

The sample comprised 314 adolescents aged 13–17 years with treatment-resistant OCD and a Children’s Yale–Brown Obsessive–Compulsive Scale Self-Report (CY-BOCS-SR) total score ≥16. Bivariate and multiple regression models were used to evaluate the predictors of continuous OCD severity outcome and treatment response.

Results of the bivariate regression analyses of predictors demonstrated that length of treatment, pre-treatment OCD severity, and symptoms of anxiety and depression significantly predicted post-treatment OCD severity, while only symptoms of depression and anxiety predicted treatment response. When including all predictors in the same model, only baseline OCD severity remained a significant predictor of post-treatment OCD severity, and none of the assessed variables significantly predicted treatment response.

Results indicate that low pre-treatment OCD severity predicts lower OCD severity following treatment, although it did not predict treatment response.     

Implicit learning, thought-focused attention and obsessive-compulsive disorder: a replication and extension

Although significant empirical support exists for both cognitive and neurobiological models of obsessive-compulsive disorder (OCD), there have been few efforts to integrate findings. In this investigation, we attempted to link models by examining relationships between performance on information processing tasks posited to be markers of OCD-related neuropathology and a self-report measure of excessive thought-focused attention (cognitive self-consciousness; CSC). Congruent with predictions and prior research, OCD patients' performance was impaired in comparison to an anxious control group on the Serial Reaction Time (SRT) Task, a measure of implicit procedural learning. Following completion of the SRT, participants' awareness of the embedded stimulus pattern was assessed. As predicted, participants with OCD demonstrated superior performance on this task. Scoring on a measure of CSC correlated with performance on both tasks, although the amount of variance accounted for was modest. Evaluation of OCD symptom subgroups revealed greater procedural learning impairment in a hoarding subgroup. Implications for theory and treatment are discussed.     

Personality in Germany and Minnesota: an IRT-based comparison of MPQ self-reports

We compared personality across cultures to explore the extent of cultural differences. This study used samples matched on gender and age from Germany and Minnesota to compare traditional scale scores and IRT-based parameters for Tellegen's (1982) Multidimensional Personality Questionnaire scales. Because the samples consisted of twins, we were able to replicate the findings from the subsamples consisting of one member of each pair with the subsamples consisting of their co-twins. When the full scales were considered, Germans were higher in Aggression and Absorption and Minnesotans were higher in Well-being, Control, and Traditionalism, but, except for those in Traditionalism, different item-difficulty parameters explained most of these differences. IRT highlighted less than optimal scale properties as well as differentially functioning items. We discuss the theoretical implications of these findings.     

Sources of structure: genetic, environmental, and artifactual influences on the covariation of personality traits

The phenotypic structure of personality traits has been well described, but it has not yet been explained causally. Behavior genetic covariance analyses can identify the underlying causes of phenotypic structure; previous behavior genetic research has suggested that the effects from both genetic and nonshared environmental influences mirror the phenotype. However, nonshared environmental effects are usually estimated as a residualterm that may also include systematic bias, such as that introduced by implicit personality theory. To reduce that bias, we supplemented data from Canadian and German twin studies with cross-observer correlations on the Revised NEO Personality Inventory. The hypothesized five-factor structure was found in both the phenotypic and genetic/familial covariances. When the residual covariance was decomposed into true nonshared environmental influences and method bias, only the latter showed the five-factor structure. True nonshared environmental influences are not structured as genetic influences are, although there was some suggestion that they do affect two personality dimensions, Conscientiousness and Love. These data reaffirm the value of behavior genetic analyses for research on the underlying causes of personality traits.     

The genetic links between the big five personality traits and general interest domains

This is the first genetically informative study in which multiple informants were used to quantify the genetic and environmental sources of individual differences in general interests as well as the phenotypic and genetic links between general interests and Big Five personality traits. Self-reports and two peer ratings from 844 individuals, including 225 monozygotic and 113 dizygotic complete twin pairs, were collected. Multiple-rater scores (composites) revealed that the averaged levels of genetic and environmental effects on seven broad interest domains were similar to those on personality traits. Multivariate analyses showed that about 35% of the genetic and 9% of the environmental variance in interests were explained by personality domains, in particular by Openness. The findings suggest that interests cannot easily be considered as a byproduct of the interactions between personality genotypes and the environmental influences but rather as an internal regulation of behavior with an own genetic basis.     

Unravelling the Interplay Between Genetic and Environmental Contributions in the Unfolding of Personality Differences from Early Adolescence to Young Adulthood

In two studies, we examined the genetic and environmental sources of the unfolding of personality trait differences from childhood to emerging adulthood. Using self‐reports from over 3000 representative German twin pairs of three birth cohorts, we could replicate previous findings on the primary role of genetic sources accounting for the unfolding of inter‐individual differences in personality traits and stabilizing trait differences during adolescence. More specifically, the genetic variance increased between early (ages 10–12 years) and late (ages 16–18 years) adolescence and stabilized between late adolescence and young adulthood (ages 21–25 years). This trend could be confirmed in a second three‐wave longitudinal study of adolescents' personality self‐reports and parent ratings from about 1400 Norwegian twin families (average ages between 15 and 20 years). Moreover, the longitudinal study provided evidence for increasing genetic differences being primarily due to accumulation of novel genetic influences instead of an amplification of initial genetic variation. This is in line with cumulative interaction effects between twins' correlated genetic makeups and environmental circumstances shared by adolescent twins reared together. In other words, nature × nurture interactions rather than transactions can account for increases in genetic variance and thus personality variance during adolescence. © 2019 European Association of Personality Psychology