Gary J. Lewis

Neural correlates of the ‘good life’: eudaimonic well-being is associated with insular cortex volume

Eudaimonic well-being reflects traits concerned with personal growth, self-acceptance, purpose in life and autonomy (among others) and is a substantial predictor of life events, including health. Although interest in the aetiology of eudaimonic well-being has blossomed in recent years, little is known of the underlying neural substrates of this construct. To address this gap in our knowledge, here we examined whether regional gray matter (GM) volume was associated with eudaimonic well-being. Structural magnetic resonance images from 70 young, healthy adults who also completed Ryff’s 42-item measure of the six core facets of eudaimonia, were analysed with voxel-based morphometry techniques. We found that eudaimonic well-being was positively associated with right insular cortex GM volume. This association was also reflected in three of the sub-scales of eudaimonia: personal growth, positive relations and purpose in life. Positive relations also showed a significant association with left insula volume. No other significant associations were observed, although personal growth was marginally associated with left insula, and purpose in life exhibited a marginally significant negative association with middle temporal gyrus GM volume. These findings are the first to our knowledge linking eudaimonic well-being with regional brain structure.

From left to right: How the personality system allows basic traits to influence politics via characteristic moral adaptations

Research on the association of personality to political orientation has suggested that direct influences are modest. Here we used a personality system model in which direct influences on political behaviour flow from moral values, with personality mostly acting on these characteristic moral adaptations, rather than directly affecting political attitudes. Study 1 in 447 subjects supported this model, with significant effects on political orientation flowing from four of the five-factor model personality domains, but largely mediated through moral values concerning the importance of group order and individual rights. This personality system model was replicated in an independent study (n= 476) using a US sample and including a different measure of politics. Both studies support predictions that personality has significant effects on political attitudes, but that these are exerted largely via moral values. These findings help to explain inconsistencies in previous studies attempting to link personality to political orientation that have not included the intermediary level of values.

Childhood Socioeconomic Status Amplifies Genetic Effects on Adult Intelligence

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.

Moral values are associated with individual differences in regional brain volume

Moral sentiment has been hypothesized to reflect evolved adaptations to social living. If so, individual differences in moral values may relate to regional variation in brain structure. We tested this hypothesis in a sample of 70 young, healthy adults examining whether differences on two major dimensions of moral values were significantly associated with regional gray matter volume. The two clusters of moral values assessed were “individualizing” (values of harm/care and fairness) and “binding” (deference to authority, in-group loyalty, and purity/sanctity). Individualizing was positively associated with left dorsomedial pFC volume and negatively associated with bilateral precuneus volume. For binding, a significant positive association was found for bilateral subcallosal gyrus and a trend to significance for the left anterior insula volume. These findings demonstrate that variation in moral sentiment reflects individual differences in brain structure and suggest a biological basis for moral sentiment, distributed across multiple brain regions.

Unearthing the “Green” Personality Core Traits Predict Environmentally Friendly Behavior

Pro-environmental attitudes and behaviors show substantial individual differences, and exploring their predictors can help reveal the origins of pro-environmental behavior. Basic personality traits may provide a partial explanation, but it is unclear which personality traits are reliably associated with pro-environmental behaviors. This article uses a specific type of environmental behavior, reducing greenhouse gas emissions, to clarify which personality correlates are most robustly associated with behavior, and to test mediation of those effects through attitudes. A large (N = 345) sample of United States adults representative in age, gender, and ethnicity completed the 100-item HEXACO personality inventory, a novel self-report measure of behaviors that reduce greenhouse gas emissions, and scales of environmental and political attitudes. Accounting for demographics, emissions-reducing behaviors were most strongly predicted by Openness, Conscientiousness, and Extraversion, and these effects of personality were mediated by attitudes toward the natural environment. These observations broaden the understanding of the etiology of environmental attitudes and behavior.

Genetic Evidence for Multiple Biological Mechanisms Underlying In-Group Favoritism

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.

Genetic Influences on Psychological Well‐Being: A Nationally Representative Twin Study

OBJECTIVE Psychological well-being, or eudaimonia, features strongly in theories of human development and thriving. However, the factors of eudaimonia are debated, and their genetic architecture has not been studied in detail. METHOD A classical twin design was used to decompose behavioral variance into genetic and environmental components implemented in a multigroup, multivariate structural equation modeling framework. Subjects were 837 pairs of adult U.S. twins from the nationally representative MIDUS II sample. Psychological well-being was measured using the 42-item Ryff Psychological Well-Being Scale, which assesses autonomy, environmental mastery, personal growth, positive relations with others, purpose in life, and self-acceptance. RESULTS Substantial genetic influences were observed on all components of well-being. Attempts to model these six factors as reflecting a single common psychological mechanism gave a poor fit to the data. The best-fitting model supported the existence of five distinct genetic effects. Effects of shared environment were weak and nonsignificant. Unique environmental effects for all measures were mostly trait specific. CONCLUSIONS These results indicate that psychological well-being is underpinned by a general genetic factor influencing self-control, and four underlying biological mechanisms enabling the psychological capabilities of purpose, agency, growth, and positive social relations.

Perceiving Aggression from Facial Structure: Further Evidence for a Positive Association with Facial Width‐to‐Height Ratio and Masculinity, but not for Moderation by Self‐Reported Dominance

Recent work has indicated that individual differences in facial structure are linked to perceptions of aggressiveness. In particular, the relative width of a face [facial width–to–height ratio (fWHR)] has been suggested to be a reliable cue to aggressive behaviour, at least in men. Additionally, facial masculinity has been associated with perceptions of dominance, a close proxy of aggressiveness. In two studies, we assessed the robustness of this link using faces transformed along these vectors in men (Studies 1 and 2) and women (Study 2). Additionally, we examined whether individual differences in self–reported dominance of perceivers moderated this association in order to extend previous work indicating that own dominance affects perception of such behaviour in others. Results indicated that both male and female faces with increased fWHR and increased facial masculinity were perceived as more aggressive. However, we found no systematic evidence for moderating effects of self–reported dominance on the perception of aggression in others. Taken together, these results further support the robustness of fWHR and facial masculinity as cues to aggressiveness but question whether observers’ own dominance moderates their perception of these cues in others. Copyright

Common Heritable Effects Underpin Concerns Over Norm Maintenance and In-Group Favoritism: Evidence From Genetic Analyses of Right-Wing Authoritarianism and Traditionalism

Research has shown that in-group favoritism is associated with concerns over the maintenance of social norms. Here we present two studies examining whether genetic factors underpin this association. A classical twin design was used to decompose phenotypic variance into genetic and environmental components in two studies. Study 1 used 812 pairs of adult U.S. twins from the nationally representative MIDUS II sample. Study 2 used 707 pairs of middle-age twins from the Minnesota Twin Registry. In-group favoritism was measured with scales tapping preferences for in-group (vs. out-group) individuals; norm concerns were measured with the Multidimensional Personality Questionnaire-Traditionalism (Study 1) and Right-Wing Authoritarianism (RWA; Study 2) scales. In Study 1, heritable effects underlying traditionalism were moderately (c. 35%) overlapping with the genetic variance underpinning in-group favoritism. In Study 2, heritable influences on RWA were entirely shared with the heritable effects on in-group favoritism. Moreover, we observed that Big Five Openness shared common genetic links to both RWA and in-group favoritism. These results suggest that, at the genetic level, in-group favoritism is linked with a system related to concern over normative social practices, which is, in turn, partially associated with trait Openness.

Identical genetic influences underpin behavior problems in adolescence and basic traits of personality

Background Understanding the etiology of adolescent problem behavior has been of enduring interest. Only relatively recently, however, has this issue been examined within a normal personality trait framework. Research suggests that problem behaviors in adolescence and beyond may be adequately explained by the taxonomy provided by the basic dimensions of normal personality: Such problem behaviors are suggested to be extreme points on a distribution of the full range of the underlying traits. We extend work in this field examining the extent to which genetic factors underlying the five-factor model of personality are common with genetic influences on adolescent behavior problems (namely, anxiety, peer problems, conduct, hyperactivity, and low prosociality). Method A nationally representative twin sample (Twins Early Development Study) from the general population of England and Wales, including 2031 pairs of twins aged 16 years old, was used to decompose variation into genetic and environmental components. Behavioral problems in adolescence were assessed by self-report with the Strengths and Difficulties Questionnaire. Results Adolescent behavior problems were moderately associated with normal personality: Specifically, a fifth to a third of phenotypic variance in problem behaviors was accounted for by five-factor model personality traits. Of central importance here, genetic influences underpinning personality were entirely overlapping with those genetic factors underlying adolescent behavior problems. Conclusions These findings suggest that adolescent behavior problems can be understood, at least in part, within a model of normal personality trait variation, with the genetic bases of these behavior problems the same as those genetic influences underpinning normal personality. Read the Commentary for this article on doi: 10.1111/jcpp.12292