How genetic and environmental variance in personality traits shift across the life span: Evidence from a cross-national twin study

The education-health gradient: Revisiting the role of socio-emotional skills

Is the education-health gradient inflated because both education and health are associated with unobserved socio-emotional skills? We find that the gradient in health behaviors and outcomes is reduced by about 15 to 50% from accounting for fine-grained personality facets and up to another 50% from Locus of Control. Traditional aggregated Big-Five scales, however, have a much smaller contribution to the gradient. We use sibling-fixed effects to net out the contribution from genes and shared childhood environment, decomposing the gradient into its components with an order-invariant method. We rely on a large survey (N = 28,261) linked to high-quality Danish administrative registers with information on parental background and objectively measured diagnoses and care use. Accounting for Locus of Control yields the strongest gradient reduction in self-rated health status and objective diagnoses (30%-50%), and in health behaviors the most important factor is Extraversion, a skill that has been shown to be malleable in interventions.

Broad and narrow environmental and genetic sources of personality differences: An extended twin family study

OBJECTIVE

Several personality theories distinguish between rather genetically rooted, universal dispositional traits (DTs) and rather environmentally shaped, more contextualized characteristic adaptations (CAs). However, no study so far has compared different measures of theoretically postulated DTs and CAs regarding their environmental and genetic components while considering differences in measurement abstraction and reliability. This study aims to bridge this gap by testing the assumed differences in the sensitivity to environmental influences based on representative sets of DTs (Big Five and HEXACO domains and facets) and CAs (goals, interests, value priorities, religiousness, and self-schemas).

METHOD

Using intra-class correlations and running extended twin family and spouses-of-twins model analyses, we analyzed a large data set (N = 1967) encompassing 636 twin pairs, 787 parent-offspring dyads, and 325 spouses/partners.

RESULTS

Findings consistently support lower environmentality of DTs compared to CAs. On average, more than half of reliable variance in DTs was genetic, whereas the reverse was found for CAs. Larger environmental components in CAs were primarily attributable to larger individual-specific effects (beyond error of measurement) and factors shared by spouses.

CONCLUSIONS

Findings are discussed against the background of the definitional distinction between DTs and CAs and the value of extended twin family data.

The Epigenetics of Animal Personality

Animal personality, consistent individual differences in behaviour, is an important concept for understanding how individuals vary in how they cope with environmental challenges. In order to understand the evolutionary significance of animal personality, it is crucial to understand the underlying regulatory mechanisms. Epigenetic marks such as DNA methylation are hypothesised to play a major role in explaining variation in phenotypic changes in response to environmental alterations. Several characteristics of DNA methylation also align well with the concept of animal personality. In this review paper, we summarise the current literature on the role that molecular epigenetic mechanisms may have in explaining personality variation. We elaborate on the potential for epigenetic mechanisms to explain behavioural variation, behavioural development and temporal consistency in behaviour. We then suggest future routes for this emerging field and point to potential pitfalls that may be encountered. We conclude that a more inclusive approach is needed for studying the epigenetics of animal personality and that epigenetic mechanisms cannot be studied without considering the genetic background.

Relations between HEXACO personality and ideology variables are mostly genetic in nature

Existing work indicates that socio-political attitudes (or: ideology) are associated with personality, with Social Dominance Orientation and Right-Wing Authoritarianism relating most strongly to honesty-humility and openness to experience, the two value-related domains of the HEXACO framework. Using a sample of 7067 twins and siblings of twins (including 1376 complete twin pairs), we examined the degree to which these relations arise from common genetic and environmental sources. Heritability estimates for the HEXACO personality and ideology variables ranged from .34 to .58. Environmental factors shared by twins reared together showed negligible effects on individual differences in personality and ideology. At the phenotypic level, Social Dominance Orientation and Right-Wing Authoritarianism dimensions related most strongly to honesty-humility and openness to experience. These associations were mostly explained by genetic factors (48%–93%). Genetic correlations between openness to experience and the ideology scales ranged from –.29 to –.53; those between honesty-humility and the ideology scales ranged from –.31 to –.43. None of the environmental correlations exceeded | r| = .18. These results suggest that the relations between the two value-related domains of the HEXACO personality model and ideology are mostly genetic in nature, and that there is substantial overlap in the heritable components of personality and ideology.

Introducing two types of psychological resilience with partly unique genetic and environmental sources

Psychological resilience is indicated when individuals demonstrate good mental health despite exposure to significant stress or adversity. Good mental health may involve low levels of illbeing and/or high levels of wellbeing. There is still very limited knowledge about the potential differences between these outcomes in relation to stressors. We propose a distinction between type 1 and type 2 resilience, examine their underlying genetic and environmental architecture, and identify modifiable resilience factors. The data come from a population-based twin sample (N = 1987, mean age = 63) in the Norwegian Twin Registry. Type 1 and type 2 resilience are operationalised as the residual of anxiety/depression symptoms and life satisfaction, respectively, after lifetime cumulative adversity has been regressed out. We used biometric modelling and cotwin-control linear mixed models to estimate underlying factors and identify predictors while controlling for genetic confounding. The results support the notion of two separate, but partly overlapping types of resilience. We find heritabilities of 0.30 (type 1) and 0.24 (type 2) and a genetic correlation of 0.43. Potentially causal resilience factors include, but are not limited to, meaning in life, physical activity, positive affect and relationship satisfaction. Whereas some factors are associated with both resilience types, other factors are unique to each type.