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.     

Genetic and environmental structure of adjectives describing the domains of the Big Five Model of personality: A nationwide US twin study

We applied multivariate models specifying genetic and environmental influences on adjectives describing each of the five personality domains specified in the Big Five Model of personality (BFM; Extraversion, Neuroticism, Agreeableness, Conscientiousness, and Openness). We selected the specific models to partition the observed covariance among the adjectives describing each domain into genetic and environmental components in order to assess the etiologic basis for each domain's phenotypic coherence. The sample on which our analyses were based was part of the National Survey of Midlife Development in the United States (MIDUS). It consisted of 315 monozygotic and 275 same-sex dizygotic twin pairs. Results revealed both common and specific genetic and environmental influences for each domain, suggesting that all of the domains are etiologically complex. Models specifying the domains as latent phenotypic constructs fit more poorly than models suggesting more complex structures for all domains except Extraversion and Neuroticism. These results raise questions about the BFM as a coherent model of genetic and environmental influences on personality or, alternatively, about the etiological unity of latent phenotypic personality trait constructs beyond Extraversion and Neuroticism.     

Humor styles and borderline personality

The present study examined the phenotypic, genetic, and environmental correlations between four humor styles (affiliative, self-enhancing, aggressive, and self-defeating) and four dimensions of borderline personality disorder (affective instability, identity disturbance, negative relationships, self-harm) as well as a total borderline personality disorder score. Participants were 574 same-sex Australian adult twin pairs. At the phenotypic level, the two adaptive humor style dimensions (affiliative and self-enhancing) were found to correlate negatively with borderline personality and the two maladaptive humor style dimensions (aggressive and self-defeating) were found to have positive correlations with borderline personality. Bivariate genetic analyses demonstrated significant genetic, common environment, and unique environmental correlations. These results indicate that a large component of the phenotypic association between borderline personality disorder and humor style arises from the influence of shared familial and environmental factors associated with both phenotypes.     

MAXIMUM VARIANCE LINEAR COMBINATIONS FROM PHENOTYPIC,GENETIC, AND ENVIRONMENTAL COVARIANCE MATRICES

Vectors of weights derived from principal components analysis of stan- dardized phenotypic, genetic, and environmental covariance matrices were applied to open-field behavioral scores from mice in order to obtain composite scores with maximum phenotypic (Vp), genetic (Va), and environmental (Ve)variance, respectively. Since Va associated with the composite from the genetic covariance matrix is derived as maximum, and since Vp associated with this combination cannot be as large as that associated with the phenotypic com- posite, heritability of the genetic composite must exceed that of the phenotypic composite. In addition, since Ve associated with the environmental composite is maximum and since Vp associated with this score cannot exceed Vp from the phenotypic composite, Va associated with the phenotypic composite should exceed that from the environmental composite. Thus, heritability of the pheno- typic composite scores should exceed that for the environmental composite. The predicted rank order of the heritabilities was observed. Pooled estimates of the heritabilities of the genetic, phenotypic, and environmental components were 0.24, 0.19, and 0.17, respectively.     

Normal and abnormal personality traits: evidence for genetic and environmental relationships in the Minnesota Study of Twins Reared Apart

ABSTRACT Recent studies have demonstrated substantial correlations between normal and abnormal personality traits. Yet little is known about how these correlations are mediated genetically and environmentally: Do normal and abnormal personality traits stem from the same underlying genes and environments? We addressed this question using data from 128 monozygotic and dizygotic twin pairs in the Minnesota Study of Twins Reared Apart (MISTRA). Additive genetic and nonshared environmental correlations between scales of the Minnesota Multiphasic Personality Inventory (MMPI)—an index of abnormal personality—and the Multidimensional Personality Questionnaire (MPQ)—an index of normal personality—were estimated. Results indicated that phenotypic correlations between normal and abnormal personality were mediated by genetic as well as environmental factors, although the magnitude of genetic mediation tended to be larger overall. Moreover, the patterns of phenotypic, genetic, and environmental relationships among the scales were similar, suggesting that influences on normal and abnormal personality act through systems common to both. It is suggested that future research focus on the neurogenetic substrates of these shared systems and how dysfunction in these systems influences development of disordered personality.     

A behavior genetic analysis of personality and loneliness

The phenotypic, genetic, and environmental correlations between the Big Five factors of personality and loneliness were examined. At the phenotypic level, loneliness had a strong significant positive correlation with neuroticism, significant moderate negative correlations with agreeableness, conscientiousness, and extraversion, and a small positive correlation with openness. Both loneliness and personality were found to be heritable. Bivariate genetic analyses resulted in significant positive genetic correlations between loneliness and neuroticism and openness, and significant negative genetic correlations with agreeableness, conscientiousness, and extraversion. Significant unique environment correlations were found between loneliness and four of the five personality factors (all negative except neuroticism) and a non-significant correlation with openness. The results suggest common genetic and unique environmental factors play a role in personality and loneliness.     

General and supplementary factors of personality in genetic and environmental correlation matrices

Genetic and environmental correlation matrices among 7 personality scales were estimated, using samples of adult and young adult twins from Australia (2081 and 1178 pairs, respectively). A general factor of personality and two supplemental factors were obtained in each. The supplemental factors were tentatively identified as Social conformity and Other-dependence. Factors from the genetic and environmental correlations replicated well across samples, and they were similar in both the genetic and environmental covariation. It was concluded that the structure of personality is inherent in the evolved phenotype, and is not the immediate consequence of either genetic or environmental organizing factors.     

Genetic relationships between personality and eating attitudes and behaviors

Genetic and environmental factors underlying relationships between personality traits and disordered eating were examined in 256 female adolescent twin pairs (166 monozygotic, 90 dizygotic). Eating behaviors were assessed with the Total Score, Body Dissatisfaction, Weight Preoccupation, Binge Eating, and Compensatory Behavior subscales from the Minnesota Eating Disorders Inventory (M-EDI; K. L. Klump, M. McGue, & W. G. Iacono, 2000). Personality characteristics were assessed with the Negative Emotionality, Positive Emotionality, and Constraint scales from the Multidimensional Personality Questionnaire (MPQ; A. Tellegen, 1982). Model-fitting analyses indicated that although genetic factors were more likely to contribute to MPQ and M-EDI phenotypic associations than environmental factors, shared genetic variance between the 2 phenotypes was limited. MPQ personality characteristics may represent only some of several genetic risk factors for eating pathology.     

Phenotypic and genetic relationships between vocational interests and personality

Relationships between personality and vocational interest factors were examined at the phenotypic and genetic levels. Twins and siblings (N = 516) completed self-report personality and vocational interest scales. Following factor analyses of each scale, five personality and six vocational interest factors were extracted. At the phenotypic level, correlations between personality and vocational interests ranged from zero to .33. Heritability estimates of the scales showed that genetic components accounted for 0–56% of the variance for the vocational interest factors and 44–65% for the personality factors. Genetic correlations between the two areas ranged from zero to .50. The results suggest that personality is related to some vocational interest dimensions and that some of these observed relationships have a common genetic basis.     

A behavioral genetic study of the overlap between personality and parenting

The current study had three aims. The first was to examine the covariation between personality of parents and parenting behaviors. The second aim was to examine the genetic and environmental influences on parenting behaviors. The third aim was to examine the extent to which the association between personality and parenting was mediated by genetic and environmental factors. Personality (Five Factor Model, NEO-FFI) and parenting data were collected as part of a larger German study of 300 adult twin pairs (GOSAT). The current paper analyzes data on a subset of the 300 twin pairs from the GOSAT sample who were concordant for having children (n=98 pairs or 196 individuals). Results indicated modest overlap between personality and parenting. In addition, univariate behavioral genetic analyses indicated moderate genetic influence on select parenting dimensions. Results also indicated that the moderate phenotypic covariation between personality and parenting was attributed largely to nongenetic factors. Implications of the findings for research on parenting and personality are considered.     

Self‐rated personality and intelligence: a multivariate genetic analysis

The present study investigated the phenotypic, genetic, and environmental correlations between personality factors and measured intelligence. Twin pairs (92 monozygotic and 50 same sex dizygotic) completed 20 sets of personality adjectives in self‐report form as well as a group administered intelligence test, measuring general intelligence and verbal and performance composite scales. The personality adjectives were found to fit a five factor model. Personality aggregates were also created based on multiple regression analyses and used to predict each intelligence dimension. Triangular decompositions were computed to estimate the degree to which the phenotypic personality and intelligence relations were attributable to common genetic and/or environmental factors. Results of these analyses found small to moderate genetic and environmental correlations between intelligence and the personality factors, and moderate to high genetic correlations between intelligence and the personality aggregates, suggesting that intelligence is related to some personality traits at both the phenotypic and the genetic level. Copyright © 1999 John Wiley & Sons, Ltd.     

Genetic and environmental covariance structures among WISC-R subtests: A twin study

Genetic and environmental correlations among 11 Wechsler Intelligence Scale for Children-Revised (WISC-R) subtests were estimated from a sample of 143 twin pairs using the methodology of multivariate behavioral genetics. The genetic correlations among subtests varied in magnitude and exhibited a pattern similar to corresponding phenotypic correlations. Correlations due to within-pair environmental influences were generally small, whereas those due to shared environmental influences tended to be intermediate. Several hypotheses regarding the structures of the additive-genetic, common environmental, and within-pair environmental covariance matrices were tested and evidence for differential factor structures was obtained. A model hypothesizing a three-factor structure for the genetic covariance matrix, a single factor for the common environmental matrix, and a single factor plus specifics for the within-pair environmental matrix fit the data well. Thus, the three-factor phenotypic structure typically observed in Wechsler Intelligence Scale for Children (WISC) data may be due largely to genetic influences.     

Sociability and positive emotionality: genetic and environmental contributions to the covariation between different facets of extraversion

The relation between sociability and positive affect is one of the most often replicated results of research on personality and subjective well-being. It is shown how behavior genetics can contribute to our understanding of the covariance between sociability and positive emotionality. The results of a multimethod behavior-genetic study with 158 monozygotic and 120 dizygotic twins are reported. In this study, sociability and two components of positive emotionality (positive affect, energy) were assessed by self-report and other report. Additionally, positive state affect was assessed in five situations and aggregated across situations. The results showed that there are strong genetic correlations between all variables. Furthermore, there are substantive correlations between the nonshared environmental components of the different variables. Shared environmental influences, however, seemed to be unimportant for explaining the correlations between sociability and the different components of positive emotionality. The results are discussed with respect to their implications for future research on sociability and positive emotionality.     

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.     

Factor structure of the MCMI basic personality scales and common-item artifact

The eight basic personality scales of the Millon Clinical Multiaxial Inventory (MCMI) were derived from Millon's theory of personality, but the adequacy of the MCMI for measuring Millon's personality constructs has never been assessed. One major problem with using factor analysis to illuminate the structure of the MCMI personality scales is that artifactual structure may result from item overlap among the scales. To analyze this, item-overlap coefficients were factored and compared to the factor structures of five subject samples. For the eight basic personality scales, three factors emerged for the overlap matrix and each of the five sample matrices: Aloof-Social, Aggressive-Submissive, and Lability-Restraint. It was concluded that these three factors are inconsistent with Millon's theory and that they will be found artifactually across a wide variety of populations due to overlapping items.     

Why is personality tied to sleep quality? A biometric analysis of twins

Despite consistent links between personality traits and poor sleep, little is known about genetic and environmental influences that may produce them. This study examined how much genetic background and environmental experiences contributed to phenotypic linkages between personality and subjective sleep quality. Seven hundred and thirty-four twin pairs from the Minnesota Study of Twin Aging and Development rated their sleep quality and provided personality reports. Bi-variate analyses revealed that genetic factors accounted for the majority of observed associations between subjective sleep quality and traits, but also that non-shared environmental experience played a role that varied across traits. The findings strongly implicate genotype in tying subjective sleep quality to personality variation, alongside non-shared environmental influences, and suggest indicate influences unique to individual traits.     

Is the genetic structure of human personality universal? A cross-cultural twin study from North America, Europe, and Asia

This study examined whether universality of the 5-factor model (FFM) of personality operationalized by the Revised NEO Personality Inventory is due to genetic influences that are invariant across diverse nations. Factor analyses were conducted on matrices of phenotypic, genetic, and environmental correlations estimated in a sample of 1,209 monozygotic and 701 dizygotic twin pairs from Canada, Germany, and Japan. Five genetic and environmental factors were extracted for each sample. High congruence coefficients were observed when phenotypic, genetic, and environmental factors were compared in each sample as well as when each factor was compared across samples. These results suggest that the FFM has a solid biological basis and may represent a common heritage of the human species.     

The general factor of personality and humor styles

The present study examined the phenotypic, genetic, and environmental correlations between a general factor of personality (GFP) and four humor styles: affiliative, self-enhancing, aggressive, and self-defeating. Participants were 571 same-sex adult twin pairs. Individuals completed the Humor Styles Questionnaire (HSQ) and a short form of the NEO personality scale (from which the GFP was extracted). The GFP was found to be heritable with an estimated value of .31. At the phenotypic level, the GFP was found to correlate significantly with the HSQ scales; positively with affiliative and self-enhancing, and negatively with aggressive and self-defeating. Three of the four phenotypic correlations were found to be attributable to correlated genetic factors, suggesting that these dimensions of humor styles and the GFP may have a common genetic factor.     

A general factor of personality: Evidence for the Big One in the five-factor model

Exploratory and confirmatory factor analyses using different personality measures in three samples confirmed the existence of general factor of personality (The Big One) within the five-factor model. The Big One is characterized by high versus low Emotional Stability, Conscientiousness, Agreeableness, Extraversion, and Openness, and by high versus low higher-order factors of personality, Stability, and Plasticity. A comprehensive theoretical model of personality structure was therefore proposed with the Big One at the highest level of the hierarchy. The Big One was interpreted as a basic personality disposition that integrates the most general non-cognitive dimensions of personality. It is associated with social desirability, emotionality, motivation, well-being, satisfaction with life, and self-esteem. It also may have deep biological roots, evolutionary, genetic, and neurophysiological.