Stability and change in genetic and environmental components of personality in old age

Stability and change in the mean levels and sources of variation in personality was examined. A sample of 149 monozygotic and 202 dizygotic twin pairs over 80 years were studied three times with a 2-year interval between measurement occasions. The Eysenck Personality Inventory to measure extraversion and neuroticism was used. Linear mixed models and Cholesky variance decomposition were carried out (age, gender and mortality controlled). High mean level stability was found in extraversion and neuroticism. Mortality was related to lower scores in extraversion and higher scores in neuroticism. In extraversion and neuroticism, genetic effects were moderate. Though no new genetic contributions emerged over time, significant new environmental effects were found over time. Controlling for mortality slightly increased genetic effect in extraversion.     

Nonshared environmental influences and personality differences in adult twins

The twin design was used to examine the importance of different experiences of siblings within the family and to identify relations between twins' personality differences and their differential experiences. A sample of 161 monozygotic and 74 dizygotic twin individuals between the ages of 18 and 75 years retrospectively reported on their different experiences when growing up. The Sibling Inventory of Differential Experience (SIDE) was used for the first time with a sample of twin siblings. In addition, the twins provided self-report measures of affect and personality. In contrast to results from a sibling adoption design, this study of twins showed greater evidence for genetic variance in the SIDE scales. Nevertheless, the SIDE showed significant associations with differences in personality and affect for monozygotic twins, which reflect pure environment-behavior relations.     

Stability and change in personality pathology: revelations of three longitudinal studies

Three major longitudinal studies of personality disorder jointly provide new insights into the nature of stability and change in this important domain of psychopathology. This commentary highlights some of the many convergent results, which indicate robust findings that can be considered "established," and also differences in the studies' purposes and methods that permit each study to make unique contributions. One of the most important findings across the studies is that DSM- diagnosed personality disorder is not as stable as the characteristic traits that underlie personality pathology, leading to the insight that DSM personality disorders are hybrids of more acute, "Axis I-like" symptoms that resolve more quickly and longer lasting affective, cognitive, and behavioral personality dysfunctions. Implications for future research are considered.     

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.     

Adolescent personality moderates genetic and environmental influences on relationships with parents

In contrast with early theories of socialization that emphasized the role of parents in shaping their children's personalities, recent empirical evidence suggests an evocative relationship between adolescent personality traits and the quality of the parent-adolescent relationship. Research using behavior genetic methods suggests that the association between personality and parenting is genetically mediated, such that the genetic effects on adolescent personality traits overlap with the genetic effects on parenting behavior. In the current study, the authors examined whether the etiology of this relationship might change depending on the adolescent's personality. Biometrical moderation models were used to test for gene- environment interaction and correlation between personality traits and measures of conflict, regard, and involvement with parents in a sample of 2,452 adolescents (M age = 17.79 years). They found significant moderation of both positive and negative qualities of the parent-adolescent relationship, such that the genetic and environmental variance in relationship quality varied as functions of the adolescent's levels of personality. These findings support the importance of adolescent personality in the development of the quality of the parent-adolescent relationship.     

Phenotypic, genetic, and nonshared environmental parallels in the structure of personality: a view from the multidimensional personality questionnaire

How closely do observed, phenotypic personality structures correspond with underlying, genetic, and environmental personality structures? This question was addressed using data from 2,490 pairs of twins from the Minnesota Twin Registry, who completed A. Tellegen's (1982) Multidimensional Personality Questionnaire (MPQ). Phenotypic, additive genetic, and nonshared environmental correlations were computed among the MPQ's eleven primary scales. Principal component analyses of all three matrices revealed three broad, higher-order components that were readily interpreted as negative emotionality, positive emotionality, and constraint. The components from all three matrices were highly comparable, suggesting that the observed, phenotypic structure of personality corresponds closely with the underlying, etiological structure of personality.     

Stability and change in adult intelligence: 1. Analysis of longitudinal covariance structures

We address two questions of central interest in adult intellectual development: the equivalence of psychometric tests' measurement properties at different ages, and the stability of individual differences in intelligence over time. We performed a series of longitudinal factor analyses using the LISREL program to model longitudinal data from Schaie's Seattle Longitudinal Study. The results indicate complete invariance in the loadings of five subtests of Thurstone's Primary Mental Abilities battery on a general intelligence factor. Individual differences in general intelligence were highly stable over 14-year epochs, with standardized factor correlations averaging about .9 between adjacent 7-year testing intervals. These results indicate that most individuals in this relatively select longitudinal sample maintained their relative ordering in intelligence.     

Stability and change in personality traits from late adolescence to early adulthood: a longitudinal twin study

We conducted a longitudinal-biometric study examining stability and change in personality from ages 17 to 24 in a community sample of male and female twins. Using Tellegen's (in press) Multidimensional Personality Questionnaire (MPQ), facets of Negative Emotionality (NEM) declined substantially at the mean and individual levels, whereas facets of Constraint (CON) increased over time. Furthermore, individuals in late adolescence who were lowest on NEM and highest on CON remained the most stable over time, whereas those exhibiting the inverse profile (higher NEM, lower CON) changed the most in a direction towards growth and maturity. Analyses of gender differences yielded greater mean-level increases over time for women as compared to men on facets of CON and greater mean-level increases for men than women on facets of Agentic Positive Emotionality (PEM). Biometric analyses revealed rank-order stability in personality to be largely genetic, with rank-order change mediated by both the nonshared environment (and error) as well as genes. Findings correspond with prior evidence of a normative trend toward growth and maturity in personality during emerging adulthood.     

Marriage and personality: a genetic analysis

There is substantial evidence that married people fare better than their unmarried peers on many life outcome variables. The authors asked whether self-selection might partially explain these benefits through genetic influences on personality contributing to propensity to marry. Using a population-based sample of 4,225 women and 2,869 men that included 2,527 complete twin pairs, the authors investigated the phenotypic associations between personality and propensity to marry, the heritability of propensity to marry, and the extent of genetic influence on the link between personality and propensity to marry. The results suggest that propensity to marry is heritable and that the phenotypic link between personality and propensity to marry is genetically influenced.     

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.     

Stability and change in adult intelligence: 2. Simultaneous analysis of longitudinal means and covariance structures

We analyzed data on psychometric intelligence from the Seattle Longitudinal Study, simultaneously estimating longitudinal factors, their covariance structure, and their mean levels. Data on five Thurstone Primary Mental Abilities subtests were available for 412 adults, ages 22-70 at first test, who were tested three times at 7-year intervals. A previous longitudinal factor analysis had shown high stability of individual differences (covariance stability) in general intelligence for three adult age groups. We extended that model to estimate factor means. All three age groups showed high levels of covariance stability, but differed sharply in their mean profiles. The young group showed increasing levels of general intelligence, the middle-aged group had stable levels of intelligence, and the old group showed salient, approximately linear, decline. The patterns of stability in middle-age, followed by mean decline and high covariance stability in old age, suggest a normative developmental transition from a stability pattern to a decline pattern of general intelligence, with the inflection point occurring somewhere around age 60.     

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.     

Interplay between environmental and genetic factors in temperament/personality traits in horses (Equus caballus)

The aim of the present study was to broach the question of the relative influence of different genetic and environmental factors on different temperament/personality traits of horses (Equus caballus). The researchers submitted 702 horses to standardized experimental tests and investigated 9 factors, either genetic or environmental. Genetic factors, such as sire or breed, seemed to influence more neophobic reactions, whereas environmental factors, such as the type of work, seemed to play a more dominant role in reactions to social separation or learning abilities. Additive effects were evident, showing how environmental factors may modulate behavioral traits. This study constitutes a first step toward understanding the relative weights of genetic factors and how the environment may intervene in determining individual behavioral characteristics.     

Prosocial behavior from early to middle childhood: genetic and environmental influences on stability and change

Prosocial behavior is important for the functioning of society. This study investigates the extent to which environment shared by family members, nonshared environment, and genetics account for children's prosocial behavior. The prosocial behavior of twins (9,424 pairs) was rated by their parents at the ages of 2, 3, 4, and 7 and by their teachers at age 7. For parent ratings, shared environmental effects decreased from .47 on average at age 2 to .03 at age 7, and genetic effects increased from .32 on average to .61. The finding of weak shared environmental effects and large heritability at age 7 was largely confirmed through the use of teacher ratings. Using longitudinal genetic analyses, the authors conclude that genetic effects account for both change and continuity in prosocial behavior and nonshared environment contributes mainly to change.     

The basic components of adult playfulness and their relation with personality: The hierarchical factor structure of seventeen instruments

The primary aim of this study was testing the structure of adult playfulness in a joint analysis of seventeen questionnaires and testing the relation of the factors with the big five personality traits. A sample of 244 adults completed the questionnaires and a five factor-solution fit the data best; i.e., (a) Humorousness; (b) Cheerfulness–Uninhibitedness; (c) Expressiveness; (d) Other-directedness; and (e) Intellectuality–Creativity. Correlation analyses (bivariate, canonical) and regression analyses indicated strong overlap of the broader personality factors and the Cheerfulness–Uninhibitedness-factor (extraversion and emotional stability) as well as the Expressiveness-factor (extraversion). The study contributes towards a better understanding of the structure of playfulness in questionnaires developed for adults. Implications for future research are discussed.