Heritability of the Big Five Personality Dimensions and Their Facets: A Twin Study

ABSTRACT The genetic and environmental etiology of the five-factor model of personality as measured by the revised NEO Personality Inventory (NEO-PI-R) was assessed using 123 pairs of identical twins and 127 pairs of fraternal twins. Broad genetic influence on the five dimensions of Neuroticism, Extraversion, Openness, Agreeableness, and Conscientiousness was estimated at 41%, 53%, 61%, 41%, and 44%, respectively. The facet scales also showed substantial heritability, although for several facets the genetic influence was largely nonadditive. The influence of the environment was consistent across all dimensions and facets. Shared environmental influences accounted for a negligible proportion of the variance in most scales, whereas nonshared environmental influences accounted for the majority of the environmental variance in all scales.     

Importance of shared genes and shared environments for symptoms of depression in older adults.

The Center for Epidemiologic Studies-Depression scale was administered to 68 identical and 161 fraternal twin pairs reared apart and 114 identical and 138 fraternal pairs reared together to ascertain relative genetic and environmental contributions to individual differences in self-reported depressive symptoms. Intraclass correlations and model fitting indicated that genetic influences explained 16% of the variance in total depression scores and 19% for the Psychomotor Retardation and Somatic Complaints subscale, but heritability was minimal for the Depressed Mood and Well-Being subscales. Influence of family rearing context played a substantial role in explaining twin similarity, whereas unique life experiences accounted for the greatest proportion of variance. Significant age group differences were observed, with heritability greater in twins of 60 years of age or older than in twins under 60, especially for Psychomotor Retardation.     

Beyond the heritability of life satisfaction – The roles of personality and twin-specific influences

In a behavior genetic design, we investigated individual differences in life satisfaction and its relation to personality with respect to both internal and external influences. We questioned the absence of shared environment and examined the specific contribution of additive and non-additive genetic influences. We also tested for twin-specific environmental influences in a total sample of 1308 dyads including identical and fraternal twins, siblings, mother–child and grandparent–child pairs. The results showed substantial shared environmental influences on life satisfaction that varied between twins and non-twins, supporting twin-specific environmental influences. Additive and non-additive genetic influences on life satisfaction were completely shared with personality. The remaining variance could be explained by unique non-shared environmental influences for life satisfaction independent of personality.     

Analysis of genetic influences on the consistency and variability of the Big Five across different stressful situations

Several studies have demonstrated that individual differences in personality traits, known as the Big Five, have a genetic component. These personality traits are considered important predictors of everyday behaviour. In addition to personality traits there are also factors in the environment that govern behaviour. This dual influence on behaviour is statistically reflected in a P × S interaction. This study examines the genetic and environmental influences on the interactions between a person and his daily life environment for the Big Five. Fifty‐seven identical twin pairs and 43 fraternal twin pairs participated in this study. Trait related behaviour was measured in 30 different situations with the aid of an SR inventory. The heritability coefficients for the main effect of P were in the normal range, varying between 0.35 for Agreeableness and 0.53 for Conscientiousness. The heritability coefficients for the P × S interactions were moderately high, explaining between 26% and 69% of the total P × S variance. The consequences of these results for general and behavioural genetic research on the Big Five will be discussed. Copyright © 2001 John Wiley & Sons, Ltd.     

EAS temperaments during the last half of the life span: twins reared apart and twins reared together

In this first behavioral genetic study of personality in the last half of the life span, results are reported using the powerful adoption/twin design that compares identical and fraternal twins reared apart and identical and fraternal twins reared together. Traits studied were the EAS temperaments (emotionality, activity level, and sociability), traits that show substantial genetic influence in childhood. It was hypothesized that the EAS traits would also show significant genetic influence later in life and that most of the environmental variation would be nonshared--that is, twins reared together would show no greater resemblance for the EAS traits than twins reared apart. Both hypotheses are supported.     

Genetic influence on life events during the last half of the life span

Genetic influence on perceptions of major events later in life was assessed with a combination of twin and adoption designs as part of the Swedish Adoption/Twin Study of Aging (SATSA). The SATSA design includes 4 groups totaling 399 pairs of same-sex twins: identical and fraternal twins reared apart and matched twins reared together. The average age of the twins was 59 years. The results demonstrate significant genetic influence on reports of the occurrence of life events, especially for controllable events in which the individual can play an active role. Maximum likelihood model-fitting estimates of genetic influence indicate that 40% of the variance of the total life events score is due to genetic differences among individuals. How genetic factors can affect life experiences and directions for future research are discussed.     

Genetic mediation of the relationship between social support and psychological well-being.

This study assessed genetic and environmental influences on the association between social support and psychological functioning using the combined adoption/twin design from the Swedish Adoption/Twin Study of Aging. A subsample of 424 twin pairs, 50 years and older, was used: 64 pairs of identical twins reared apart, 95 pairs of identical twins reared together, 132 pairs of fraternal twins reared apart, and 133 pairs of fraternal twins reared together. Multivariate model-fitting analyses indicated that the relationship between the perceived adequacy of social support and psychological well-being (depression and life satisfaction) was mediated in part by genetic factors.     

The genetics and evolution of the general factor of personality

Three studies tested the hypothesis that a general factor of personality (GFP) underlies diverse individual differences including altruism, the Big Five factors of Openness, Conscientiousness, Extraversion, Agreeableness, and Emotional Stability, and the EAS temperament traits of Emotional Stability, Activity, and Sociability. In Study 1, 214 university students completed 36 personality scales. In Study 2, 322 pairs of monozygotic (MZ) and dizygotic (DZ) twins completed 29 5-point rating scales plus questionnaires. In Study 3, 575 pairs of 2- to 9-year-old Korean twins were rated by their mothers on 25 temperament scales. Factor analyses revealed a hierarchical organization with GFP at the apex and the Big Five and/or EAS temperament scales intermediate. The twin data show GFP has an early age of onset with 50% of the variance attributable to non-additive (dominance) genetic influence and 50% to unique, non-shared environmental influence. We discuss a life history matrix encompassing brain size, maturational speed, and longevity, plus emotional intelligence and the personality disorders, and suggest natural selection acted directionally to endow people with more cooperative and less contentious personalities than their archaic ancestors, or nearest living relatives, the chimpanzees.     

Happiness is a personal(ity) thing: the genetics of personality and well-being in a representative sample.

Subjective well-being is known to be related to personality traits. However, to date, nobody has examined whether personality and subjective well-being share a common genetic structure. We used a representative sample of 973 twin pairs to test the hypothesis that heritable differences in subjective well-being are entirely accounted for by the genetic architecture of the Five-Factor Model's personality domains. Results supported this model. Subjective well-being was accounted for by unique genetic influences from Neuroticism, Extraversion, and Conscientiousness, and by a common genetic factor that influenced all five personality domains in the directions of low Neuroticism and high Extraversion, Openness, Agreeableness, and Conscientiousness. These findings indicate that subjective well-being is linked to personality by common genes and that personality may form an "affective reserve" relevant to set-point maintenance and changes in set point over time.     

Nature,nurture and academic achievement: A twin study of teacher assessments of 7‐year‐olds

Background: Twin research has consistently shown substantial genetic influence on individual differences in cognitive ability; however, much less is known about the genetic and environmental aetiologies of school achievement. Aims: Our goal is to test the hypotheses that teacher‐assessed achievement in the early school years shows substantial genetic influence but only modest shared environmental influence when children are assessed by the same teachers and by different teachers. Sample: 1,189 monozygotic (MZ) and dizygotic (DZ) twin pairs born in 1994in England and Wales. Methods: Teachers evaluated academic achievement for 7‐year‐olds in Mathematics and English. Results were based on the twin method, which compares the similarity between identical and fraternal twins. Results: Suggested substantial genetic influence in that identical twins were almost twice as similar as fraternal twins when compared on teacher assessments for Mathematics, English and a total score. Conclusions: The results confirm prior research suggesting that teacher assessments of academic achievement are substantially influenced by genetics. This finding holds even when twins are assessed independently by different teachers.     

The extended genotype: the heritability of personality accounts for the heritability of recalled family environments in twins reared apart

Abstract How are retrospective accounts of family rearing environments linked to adult personality? We addressed this question by measuring both domains in a sample of 180 reared‐apart twins. Twins completed extensive measures of rearing environments (the Minnesota‐Briggs History Record, the Block Environmental Questionnaire, the Family Environment Scale, and the Physical Facilities Questionnaire) and an omnibus measure of adult personality (the Multidimensional Personality Questionnaire). Retrospective accounts of family environments were partially heritable and all the heritable variance in environmental measures could be accounted for by heritable variance in personality. In addition, differences between twins in their accounts of their rearing environments (nonshared environmental factors) were not significantly linked to differences between twins in their personalities. Hence, family environmental measures appear to be heritable because personality genes influence the way people shape and recall their rearing environments. In addition, differences in reared‐apart twins' retrospectively recalled rearing environments appear to have little impact on differences in their personalities in adulthood.     

Personality,identity styles and authoritarianism: an integrative study among late adolescents

The relations between five personality factors, three identity styles, the prejudice dispositions of right‐wing authoritarianism (RWA), social dominance orientation (SDO) and racial prejudice were investigated in a Flemish‐Belgian late adolescent sample (N = 328). Results show that Openness to Experience and Agreeableness relate to racial prejudice but that these relations were fully mediated by RWA and SDO. In addition, results show that whereas RWA relates to Conscientiousness and lack of Openness to Experience, SDO relates to lack of Agreeableness and lack of Openness to Experience. The relation between Conscientiousness and RWA and between Openness to Experience and SDO was fully mediated by the identity styles. However, Openness to Experience had a direct influence on RWA and Agreeableness had a direct influence on SDO. The implications of these findings are discussed. Copyright © 2006 John Wiley & Sons, Ltd.     

Neuroticism, extraversion, and related traits in adult twins reared apart and reared together

The relative importance of genetic and environmental factors for neuroticism, extraversion, impulsivity, and monotony avoidance were estimated in a sample of 99 monozygotic and 229 dizygotic pairs of twins reared apart (TRA) and a matched sample of 160 monozygotic and 212 dizygotic pairs of twins reared together (TRT). The average age was 58.6 (SD = 13.6); 72% of the twins were 50 or older. Model-fitting analyses verified the importance of genetic factors for all four measures; from 23% to 45% of the total variation was attributable to genetic sources. There was considerable evidence that these factors were operating in a nonadditive manner for extraversion and impulsivity. Shared environment accounted for less than 10% of the variance; some evidence for selective placement was found for neuroticism.     

Task orientation, parental warmth and SES account for a significant proportion of the shared environmental variance in general cognitive ability in early childhood: evidence from a twin study

Prior research suggests shared environmental influences on cognitive performance are important in early childhood. However, few studies have attempted to identify the factors comprising this shared environmental variance. To address this issue, we examined the covariance between task orientation, parental warmth, socioeconomic status and general cognitive ability in a British twin study of 125 pairs of identical and same-sex fraternal twins. Task orientation correlated r =.41 with general cognitive ability Bivariate genetic analyses suggested that this correlation was mediated by shared environmental influences. Additional analyses suggested that SES and parental warmth mediated about two-thirds of the shared environmental covariance between task engagement and cognitive skills.     

Heritabilities of Common and Measure-Specific Components of the Big Five Personality Factors

Three different measures of the Big Five personality dimensions were developed from the battery of questionnaires used in the National Merit Twin Study: one from trait self-rating scales, one from personality inventory items, and one from an adjective check list. Behavior-genetic models were fit to what the three measures had in common, and to the variance distinctive to each. The results of the model fitting agreed with other recent studies in showing the Big Five dimensions to be substantially and about equally heritable, with little or no contribution of shared family environment. Heritabilities for males and females did not differ significantly. For Agreeableness and Conscientiousness, some effect of shared environment was found for measure-specific variance on the personality inventory, and for Extraversion and Neuroticism, models involving nonadditive genetic variance or twin contrast effects provided slightly better fits.     

Personality at midlife: stability, intrinsic maturation, and response to life events

Although developmental theories and popular accounts suggest that midlife is a time of turmoil and change, longitudinal studies of personality traits have generally found stability of rank order and little or no change in mean levels. Using data from 2,274 men and women in their 40s retested after 6 to 9 years, the present study examined two hypotheses: (a) that retest correlations should be no higher than about .60 and (b) that there should be small decreases in Neuroticism, Extraversion, and Openness, and small increases in Agreeableness and Conscientiousness. The study also explored the effects of recalled life events on subsequent personality scores. Results did not support the first hypothesis; uncorrected retest correlations uniformly exceeded .60. This was true for all personality traits, including facets of Agreeableness and Conscientiousness not previously included in longitudinal studies. The hypothesized decreases in Neuroticism, Extraversion, and Openness were found, but Conscientiousness showed a small decrease instead of the predicted increase. Life events in general showed very little influence on the levels of personality traits, although some effects were seen for changes in job and marital status that warrant further research.     

Genetic and environmental effects on daily life stressors: more evidence for greater variation in later life

People vary in the occurrence and perceived severity of stressors experienced in their daily lives. In the current study, the authors examined the extent to which individual differences in these relatively minor occurrences are determined by genetic endowment as well as environmental influences and how these effects vary by age. Identical (n-sub(pairs) = 111) and fraternal (n-sub(pairs) = 99) twin adults ranging from 25 to 73 years old reported the occurrence and severity of their daily stressors on 8 consecutive evenings. Both genetic and unique environmental effects accounted for the variance in stressor occurrence, whereas shared family and unique environmental effects accounted for the variance in the perceived severity of these stressors. In addition, the influence of unique environment on perceived stress exerted a stronger influence among the older adults than the younger adults.     

Parent-child mutuality in early childhood: two behavioral genetic studies

Parent-child dyadic mutuality (shared positive affect, responsiveness, and cooperation) is an important component of family socialization processes. This study sought to extend previous research on mutuality by using a quantitative genetic design to examine between- and within-family variations (e.g., sibling differences) and gene-environment processes. The first study included 125 pairs of identical and same-sex fraternal 3-year-old twins. Observations of mutuality and parents' and observers' ratings of family environment and child behavior were gathered. Greater mutuality was associated with higher socioeconomic status. Moderate sibling similarity in parent-child mutuality was accounted for by child genetic similarity, suggesting evocative gene-environment correlation and nonshared environmental processes. These findings were replicated in a 2nd study of 102 pairs of adoptive and biological siblings.     

The effects of shared environment on adult intelligence: A critical review of adoption, twin, and MZA studies

There has been a vigorous debate for decades concerning the heritability of intelligence. In recent years, the debate has been focused on whether the components of IQ variability change with age and on separating environmental effects into shared and unshared components. Citing evidence from adoption studies, studies comparing identical and fraternal twins, and studies of identical twins raised apart, some prominent psychologists have concluded that the shared environment has a significant effect on the intelligence of children but little or no effect on the intelligence of adults. In this article, the evidence from such studies is reviewed. The article reaches the conclusion that while there is some evidence from adoption studies supporting the claim that shared environment has little or no effect on adult intelligence, that evidence is inconclusive and is inconsistent with evidence from twin studies and from studies of identical twins reared apart. (PsycINFO Database Record (c) 2012 APA, all rights reserved).     

A Rorschach Study of Personality Development In Identical and Fraternal Twins

To determine whether identical twins show greater resemblances in their general personality make-up than fraternals, seven pairs of identical and eight pairs of fraternal twins were studied using the Rorschach Inkblot test. The results of the inter-twin correlations, on the various Rorschach categories indicated clearly striking similarity or resemblance in identical twins, but no similarity in the case of fraternal twins. This study also clearly demonstrated the usefulness of the Rorschach technique for the study of personality.