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.     

Cross-sequential analysis of genetic influences on cognitive ability in the swedish adoption/twin study of aging

Abstract

Cross-sequential methods of analysis were applied to cognitive data from the Swedish Adoption/Twin Study of Aging. Thirteen measures of cognitive ability assessing four major domains (verbal, spatial, memory, and perceptual speed) were collected at two times of measurement separated by a three-year interval. Data were available from 41 pairs of monozygotic twins reared apart (MZA), 54 pairs of monozygotic twins reared together (MZT), 86 pairs of dizygotic twins reared apart (DZA), and 73 pairs of dizygotic twins reared together (DZT) ranging in age from 41 to 84 years. Cross-sectional differences and longitudinal changes in total variance and sources of variance were examined. With a few exceptions, both cross-sectional and longitudinal stability were found for total variance. In addition, few cross-sectional differences and longitudinal changes were found for genetic and environmental components of variance.     

Contribution of age, genes, and environment to the relationship between perceptual speed and cognitive ability

The aim of this study was to examine genetic influences on cognitive ability in adulthood in the context of the relationship between perceptual speed and cognitive aging. Quantitative genetic analysis of data from the Swedish Adoption/Twin Study of Aging allowed for estimation of the contribution of age, genetic, and environmental effects to the variance in a latent cognitive factor and to the covariance between the cognitive factor and perceptual speed. The sample included 292 pairs of monozygotic and dizygotic twins. both reared together and reared apart, ranging in age from 40 to 84 years. Analysis of components of total variance in the cognitive factor indicated that 90% of the age-related variance in the cognitive factor was shared with perceptual speed and 70% of the genetic variance in the cognitive factor was shared with perceptual speed. The correlation between the speed and cognitive factors was primarily genetically mediated.     

Genetic and Environmental Effects on Openness to Experience, Agreeableness, and Conscientiousness: An Adoption/Twin Study

ABSTRACT Previous research has indicated that extraversion and neuroticism are substantially affected both by genotype and environment. This study assesses genetic and environmental influences on the other three components of the five-factor model of personality: Openness to Experience, Agreeableness, and Conscientiousness. An abbreviated version of the NEO Personality Inventory (NEO-PI) was administered to 82 pairs of identical twins and 171 pairs of fraternal twins reared apart and 132 pairs of identical twins and 167 pairs of fraternal twins reared together. Estimates of genetic and environmental effects for Openness and Conscientiousness were similar to those found in other studies of personality: Genetic influence was substantial and there was little evidence of shared rearing environment. Results for Agreeableness were different: Genetic influence accounted for only 12% of the variance and shared rearing environment accounted for 21% of the variance. Few significant gender or age differences for genetic and environmental parameters were found in model-fitting analyses.     

Genetic and Rearing Environmental Influences on Adult Personality: An Analysis of Adopted Twins Reared Apart

ABSTRACT We report a genetic and environmental analysis of California Psychological Inventory (CPI) scale scores gathered on a sample of 45 sets of monozygotic twins reared apart (MZA) and 26 sets of dizygotic twins reared apart (DZA) Analysis of twin intraclass correlations and the results of models fit to the twin data demonstrate that the heritability of most scales and five factors of the CPI is about 50 When compared to results from studies of adult MZ and DZ twins reared together few of the scales demonstrate any common family environmental influence Placement coefficients on the Family Environment Scale (FES) can explain only a minor portion of the correlations for twins reared apart The influence of specific rearing environmental factors on adult personality was evaluated by analyzing the relationship between the FES and the CPI in this adoptee sample One FES factor (Cohesion vs Conflict) does correlate substantially with the CPI factor of Consensuality and may account for up to 24% of the variance in that factor, but the retrospectively gathered     

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.     

瑞典的双生子与子代研究： 通过双生子及其家庭来增加对遗传与环境互动的了解

双生子及子代研究（TOSS）收集了909对双生子及他（她）们的配偶和他（她）们的青少年子女的数据。设计该项目是为研究以下三个问题：1）遗传与环境是如何影响双生子父母的养育方式的？2）遗传与环境是如何影响成年人的家庭关系的？3）家庭关系是如何影响成年人的心理调适的？由于此研究包括了双生子及其子女,该设计可以与其他研究相比较来具体地分析遗传与环境的关联。此研究的结果有助于厘清遗传与环境在养育方式和家庭关系中的型态,同时也澄清了父母亲个人特征是如何影响他（她）们的养育方式,以及父母的个体特征是如何帮助解释了遗传对家庭关系的影响。此研究今后将进一步分析遗传与环境的关联与互动,以及候选基因与环境的关联与互动     

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.     

Behavioral Genetics, Health, and Aging

A recurring observation from studies of health in the elderly is the pervasiveness of individual differences. For many health-related endpoints, total variation appears to increase across age group; however, few longitudinal studies have reported whether these age differences reflect true age-related changes. There are a growing number of twin studies of aging that provide some insight, at least cross-sectionally, into the nature of individual differences in health. Increases in total variance most often reflect increases in environmental sources of variance. Covariation among traits reflects both genetic and environmental mediation, dependent on the sex of the sample and the measures of interest. Co-twin control approaches have been successful in exploring the role of environmental influences as risk factors for poor health. The most serious limitation to these studies is the lack of longitudinal information to disentangle survival and selection effects from aging.     

Genetic and environmental influences on pubertal development: longitudinal data from Finnish twins at ages 11 and 14

To study sources of individual differences in pubertal development, the authors fit a sex-limitation common factor model to data reported, at ages 11 and 14 years, by 1,891 twin pairs on items that comprise the Pubertal Development Scale (PDS; A. C. Petersen, L. Crockett, M. Richards, & A. Boxer, 1988). The model divides variation into a general pubertal factor and item-specific variation and, in addition, decomposes it into constituent sources. In both boys and girls, genetic influences made the largest contribution to variance common to PDS items. Genetic and nonshared environmental factors accounted for variation specific to PDS items in boys, whereas for girls, common environmental influences were added for growth spurt and menarcheal status. For both common and item-specific variation, genetic effects were partially sex specific. Subsidiary analyses found accelerated maturation in both boys and girls who at age 14 were reared in father-absent homes.     

Sexual behavior in young adulthood: a population-based twin study.

OBJECTIVE: With behavior genetic analyses of data from young adult twins, we evaluated theoretical perspectives that differentially emphasize biological dispositions, social/cultural factors, or universal pathways to explain individual differences in sexual behaviors. DESIGN: We fit biometric sex limitation models to three aspects of sexual behavior reported by 4,925 Finnish twins ages 23-27. MAIN OUTCOME MEASURE: From a postal questionnaire, we obtained self-report information on initiation/abstinence of sexual intercourse, onset age, and number of sexual partners. RESULTS: Genetic and non-shared environmental influences were significant for all three measures. There were trends for common environmental influences on initiation and, in females, age at first intercourse. Some differential effects in males and females were found. Results comparing onset age and number of partners among experienced twins from pairs concordant and discordant for initiation found genetic and environmental influences on initiation/abstinence overlapped those found for the other aspects of sexual behavior. CONCLUSIONS: These results document genetic variation in individual differences in sexual behavior of young adults. Incorporating genetic dispositions into integrated models of sexual behavior will facilitate more effective health promotion and risk taking intervention.     

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.     

The impact of environmental experiences on symptoms of anxiety and depression across the life span

Symptoms of anxiety and depression are relatively stable over time. Can this stability be explained by genetic influences, or is it caused by the long-lasting effects of accumulating environmental experiences? To address this question, we analyzed longitudinally assessed symptoms of anxiety and depression in eight samples of monozygotic twins of widely varying ages. These samples were drawn from American and European population-based registries. Using hierarchical linear modeling, we examined individual differences and individual changes in the level of symptoms over time. This method enabled us to decompose the variance into the predictable variance shared by both members of each pair of twins, the differences between individuals within pairs, and the residual variance. We then modeled how these components of individual variation changed over time. Within pairs, the twins' predicted levels of symptoms increasingly diverged from childhood until late adulthood, at which point the divergence ceased. By middle adulthood, environmental experiences contributed substantially to stable and predictable interindividual differences in levels of anxiety and depression.     

Unravelling the Interplay Between Genetic and Environmental Contributions in the Unfolding of Personality Differences from Early Adolescence to Young Adulthood

In two studies, we examined the genetic and environmental sources of the unfolding of personality trait differences from childhood to emerging adulthood. Using self‐reports from over 3000 representative German twin pairs of three birth cohorts, we could replicate previous findings on the primary role of genetic sources accounting for the unfolding of inter‐individual differences in personality traits and stabilizing trait differences during adolescence. More specifically, the genetic variance increased between early (ages 10–12 years) and late (ages 16–18 years) adolescence and stabilized between late adolescence and young adulthood (ages 21–25 years). This trend could be confirmed in a second three‐wave longitudinal study of adolescents' personality self‐reports and parent ratings from about 1400 Norwegian twin families (average ages between 15 and 20 years). Moreover, the longitudinal study provided evidence for increasing genetic differences being primarily due to accumulation of novel genetic influences instead of an amplification of initial genetic variation. This is in line with cumulative interaction effects between twins' correlated genetic makeups and environmental circumstances shared by adolescent twins reared together. In other words, nature × nurture interactions rather than transactions can account for increases in genetic variance and thus personality variance during adolescence. © 2019 European Association of Personality Psychology     

Multiple regression analysis of twin and sibling data

DeFries and Fulker (1985) employed a multiple regression analysis of twin data in which a cotwin's score is predicted from the proband's score, the coefficient of relationship (R = 1.0 for monozygotic twins and 0.5 for dizygotic twins), and their interaction to yield direct estimates of heritability (h²) and the proportion of variance due to common or shared environmental influences (c²). The purpose of the report is to extend this model to allow for the analysis of data from more than two familial relationships simultaneously. Data from identical twins, fraternal twins, and siblings pairs, in which one member of each pair was selected based on low reading performance, were analyzed. To analyze the data simultaneously, additional coefficients were added to the regression equation in order to differentiate shared environmental influences of twins and siblings. When the model was applied to the combined cognitive data, significant estimates for heritability were obtained in three of the six tests analyzed. The results also indicated a lack of justification for the separate twin and sibling environmental parameters, and a discussion of more parsimonious models is included.     

Accounting for the shared environment in cognitive abilities and academic achievement with measured socioecological contexts

Behavioral and molecular genetic research has established that child cognitive ability and academic performance are substantially heritable, but genetic variation does not account for all of the stratification of cognitive and academic outcomes across families. Which specific contexts and experiences contribute to these shared environmental influences on cognitive ability and academic achievement? Using an ethnically and socioeconomically diverse sample of N = 1728 twins ages 7–20 from the Texas Twin Project, we identified specific measured family, school, and neighborhood socioecological contexts that statistically accounted for latent shared environmental variance in cognitive abilities and academic skills. Composite measures of parent socioeconomic status (SES), school demographic composition, and neighborhood SES accounted for moderate proportions of variation in IQ and achievement. Total variance explained by the multilevel contexts ranged from 15% to 22%. The influence of family SES on IQ and achievement overlapped substantially with the influence of school and neighborhood predictors. Together with race, the measured socioecological contexts explained 100% of shared environmental influences on IQ and approximately 79% of shared environmental influences on both verbal comprehension and reading ability. In contrast, nontrivial proportions of shared environmental variation in math performance were left unexplained. We highlight the potential utility of constructing “polyenvironmental risk scores” in an effort to better predict developmental outcomes and to quantify children's and adolescents’ interrelated networks of experiences. A video abstract of this article can be viewed at: https://youtu.be/77E_DctFsr0     

The Structure and Sources of Right‐wing Authoritarianism and Social Dominance Orientation

Right‐wing authoritarianism (RWA) and social dominance orientation (SDO) are widely used constructs in research on social and political attitudes. This study examined their hierarchical and correlative structure (across sexes, generations and rater perspectives), as well as how genetic and environmental factors may contribute to individual differences in them (using different rater perspectives and nuclear twin family data). We found a substantive common aspect (beyond shared artificial variance arising from socially desirable responding) underlying both RWA and SDO: aggression against subordinate groups. We discussed how this aspect could help to explain the commonly reported correlation between the two concepts in Western countries. Estimates of genetic and environmental components in RWA and SDO based on self‐reports were quite comparable with those based on peer reports. When controlling for error variance and taking assortative mating into account, individual differences in RWA were primarily due to genetic contributions including genotype–environment correlation, whereas variance in SDO was largely attributable to environmental sources shared and not shared by twins. The findings are discussed in terms of the utility of RWA and SDO as basic constructs to describe individual differences in social attitudes and with respect to the different patterns of genetic and environmental influences that underlie them. Copyright © 2016 European Association of Personality Psychology     

Genes Determine Stability and the Environment Determines Change in Cognitive Ability During 35 Years of Adulthood

ABSTRACT— Previous research has demonstrated stability of cognitive ability and marked heritability during adulthood, but questions remain about the extent to which genetic factors account for this stability. We conducted a 35-year longitudinal assessment of general cognitive ability using the Armed Forces Qualification Test administered to 7,232 male twins in early adulthood and readministered to a subset of 1,237 twins during late middle age. The proportion of variance in cognitive functioning explained by genetic factors was .49 in young adulthood and .57 in late middle age. The correlation between the two administrations was .74 with a genetic correlation of 1.0, indicating that the same genetic influences operated at both times. Genetic factors were primarily responsible for stability, and nonshared environmental factors were primarily responsible for change. The genetic factors influencing cognition may change across other eras, but the same genetic influences are operating from early adulthood to late middle age.     

The genetics of economic risk preferences

We examine the influence of genetics on economic risk preferences by administering a measure of these preferences to monozygotic (MZ) (i.e., identical) and dizygotic (DZ) (i.e., non‐identical) twin pairs. Our analysis supports a dominant genetic effect and virtually no additive genetic effect on economic risk preferences, with the heritability of preferences estimated at 0.63. These findings suggest that over half of the variation in such preferences can be explained by genetic factors, with the remainder of the variance explained by environmental influences not shared among sibling twins. We discuss the implications of our findings for the study of individual differences in economic risk preferences. Copyright © 2009 John Wiley & Sons, Ltd.     

Counterproductive behaviors: Relations across life domains,etiology, and implications for applied practice

Previous research on counterproductive work behavior (CWB) has shown that workplace deviance can be predicted from individual differences and environmental variables, but relatively little is known about CWBs’ relations with counterproductive behaviors in other domains of an individual's life. Data from 500 male twins were used to examine relations among counterproductive behaviors from several life domains, including school, non‐work, substance use, and work. The results supported the hypotheses that counterproductivity in work and a variety of personal life domains, previous and contemporaneous, are strongly and positively related. A general counterproductivity factor, giving rise to rule‐ and norm‐breaking behavioral repertoire of individuals, accounted for approximately half the variance across measures of counterproductivity in specific life domains. To inform theory and research, the etiology of inter‐individual differences in counterproductivity was examined. Biometric analyses revealed that most of the variance in the counterproductivity domains examined, including CWB, is attributable to genetic and unique (nonshared) environmental factors. The general counterproductivity factor spanning different counterproductivity domains was most influenced by genetic factors (75.4%), but was also influenced by unique environmental factors (24.6%). Biometric analyses indicated that 27% of the variance in CWB is attributable to genetic influences arising from the general factor of counterproductivity and 20% from genetic factors specific to CWB. Unique environmental influences associated with the work domain explained 12% of the variance in CWB. For the CWB criterion, regression analyses explored the usefulness of information from other counterproductivity domains for prediction and employee selection. Counterproductivity from academic and non‐work domains are potent predictors of counterproductivity at work (multiple Rs ranging between .50 and .54).