Born in Korea-adopted apart: Behavioral development of monozygotic twins raised in the United States and France

Monozygotic (MZ) twins raised in different countries and cultures are rare. This report examines behavioral and physical similarities and differences of MZ female twins from South Korea, but raised separately in the United States and France. Analyses of the twins’ intelligence, special cognitive abilities, personality traits, self-esteem, job satisfaction and health histories are considered with reference to their genetic relatedness and rearing conditions. Both striking similarities and intriguing differences were noted.     

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     

The portrait of a hedonist: The personality and ethics behind the value and maladaptive pursuit of pleasure

Hedonism is the prioritizing of pleasure over other life values and is theorized to be independent of well-being. However, popular culture depicts hedonists as unhappy, as well as selfishly unconcerned with others’ well-being. Because the current literature has not differentiated between people’s value of pleasure and their maladaptive pursuit of it, we examined if these related, but not equivalent, dispositions had different personality and morality profiles. We found that value-based hedonists have a distinct moral profile (i.e., they are less likely to endorse moral foundations associated with social conservatism) and, yet, they differ little from others in regard to personality traits. We also found that people’s maladaptive hedonism (i.e., excessive pleasure-seeking) was best predicted by their personality traits (i.e., being less agreeable, less conscientious, and more neurotic) rather than by their conceptions of right and wrong. We discuss how these results contribute to our understanding of hedonism and why some people pursue their value of pleasure into over-indulgence.     

Emergenesis. Genetic traits that may not run in families.

Traits that are influenced by a configuration--rather than by a simple sum--of polymorphic genes may not be seen to be genetic unless one studies monozygotic twins (who share all their genes and thus all gene configurations) because such "emergenic" traits will tend not to run in families. Personal idiosyncrasies that have been found to be surprisingly concordant among MZ twins separated in infancy and reared apart may be emergenic traits. More speculatively, important human traits like leadership, genius in its many manifestations, being an effective therapist or parent, as well as certain psychopathological syndromes may also be emergenic. These ideas reemphasize the importance of the role played in human affairs by genetic variation.     

Genetic and environmental influences on observed personality: evidence from the German Observational Study of Adult Twins

Previous behavior-genetic research on adult personality relied primarily on self-reports or peer reports that may be subject to contrast effects, resulting in biased estimates of genetic and environmental influences. In the German Observational Study of Adult Twins (GOSAT), personality traits of 168 monozygotic (MZ) and 132 dizygotic (DZ) twin pairs were rated on 35 adjective scales, largely markers of the Big 5. The ratings were provided by 120 judges who never met the twins but observed videotaped behaviors of 1 twin of each pair in 1 of 15 different settings. The aggregated video-based trait ratings were highly reliable, and substantial correlations were obtained between MZ as well as DZ twins. Model-fit analyses suggested about 40% genetic, 25% shared environmental, and 35% nonshared environmental influence. Extraversion was the only trait that seemed not to be influenced by shared environment.     

Genetic and environmental determinants of temperament: a comparative study based on Polish and German samples

This study of 1555 adult mono‐ and dizygotic twins reared together estimates the heritability of temperament traits in a Polish and a German sample. We test whether the etiology of temperament traits differs between the two cultures and between different temperament traits. We assessed temperament traits with the Formal Characteristics of Behaviour–Temperament Inventory (FCB‐TI), the Pavlovian Temperament Survey (PTS), the Revised Dimensions of Temperament Survey (DOTS‐R), and the Emotionality–Activity–Sociability Temperament Survey (EAS‐TS). Taking error of measurement into account, genetic sources of variance explained about 50% of the variance of temperament traits. We found neither reliable cultural differences nor robust differences in the etiology of the traits. However, the four questionnaires differed systematically with respect to the proportion of genetic and environmental influences on their scales. Copyright © 2002 John Wiley & Sons, Ltd.     

The equal environments assumption of classical twin studies may not hold

The classical twin method ‐ comprising comparisons of monozygotic (MZ) and dizygotic (DZ) twins ‐ in the domain of cognitive abilities and attainments has led to wide acceptance of results suggesting a large amount of additive genetic variance, with far‐reaching implications both for the nature of future studies on the causes of cognitive variance and for intervention policies, as in education. However, this interpretation is only valid if the method observes a number of conditions, which have to hold. Here, we show that the most crucial of these, namely, the equal environments assumption (EEA), may not hold. Consequently, differences in twin correlations might be at least partly explained by treatment effects from parents, teachers, peers, and so on. In addition, well‐known interactions at various levels confound the model of simple additive effects on which the classical twin method is predicated and results are interpreted. For example, at a socio‐cognitive level, DZ twins may respond to treatments differently from MZ twins. This interaction may further explain MZ—DZ correlation differences. There is abundant evidence for such interactive effects in published twin data. We suggest that there is a need for a more thorough examination of these problems.     

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.     

Traits and trade-offs are insufficient for evolutionary personality psychology

Comments on the article by D. Nettle, who has clearly shown that evolutionary psychologists need to focus more attention on individual differences, not just species-typical universals. Such differences are not mere "noise," and evolutionary theory will gain by understanding how they are produced and maintained. However, by focusing on personality traits and the five-factor personality model, Nettle left unaddressed many of the most important aspects of human personality. An evolutionary psychology of personality must ultimately explain not just trait differences but also differences in personal goals, values, motives, identities, and life narratives--essential elements of human individuality and functionality. K. M. Sheldon et al suggest four reasons why traits and the five-factor personality model do not provide an optimal approach for explaining the evolution of personality: (a) As constructs, traits provide little purchase for explaining the causes of behavior; (b) trait concepts do not acknowledge or explain people's variations around their own baselines, variations that are likely crucial for adaptation; (c) traits do not explain or even describe true human uniqueness, i.e. the ways in which a person is different from everybody else; and (d) traits do not explain personality from the inside, by considering what people are trying to do in their lives. In raising these issues Sheldon et al are suggesting that the important question for evolutionary personality study is not why people fall at different points on a continuum regarding traits x, y, and z, but rather why each person is inevitably unique while still sharing the same evolved psychology.     

The heritability of cognitive functioning in very old adults: evidence from Danish twins aged 75 years and older

Heritable influences on cognitive functioning were investigated in a sample of 403 pairs of like-sex Danish twins aged 75 years and older. Twins completed the Mini-Mental State Examination and 3 other cognitive tests. Genetic factors accounted for 26-54% of the variance on these measures, with the balance being due to environmental factors that create differences rather than similarities among reared-together relatives. Deleting twins with severe cognitive impairment had little effect on the results, indicating that the heritability of cognitive functioning was not due entirely to genes affecting dementia. Neither age nor gender moderated twin similarity, and differential social contact could not account for correlation differences between monozygotic and dizygotic twins. These results replicate G. E. McClearn et al.'s (1997) study in indicating substantial genetic influences on late-life cognitive functioning.     

The General Factor of Personality: A critical test

The present study provides evidence supporting the presence of a General Factor of Personality (GFP), which has been proposed to represent the apex of the hierarchy of personality traits. Furthermore, the construct validity of this general factor is assessed to address recent criticisms suggesting that the GFP may merely be a statistical artefact rather than a genuine higher-order personality dimension. In this study, two samples of monozygotic (MZ) and same-sex dizygotic (DZ) twins completed the NEO Personality Inventory-Revised (NEO-PI-IR), assessing individual differences in the Big Five traits of personality, and the Dimensional Assessment of Personality Problems-Differential Questionnaire (DAPP-DQ) measuring variance in abnormal personality traits. First unrotated factors were extracted from each of the two measures separately within each sample. Correlations between these factors were significant and high in both samples (.78 and .77), indicating that the factors represent similar constructs. The manner in which these findings help to validate the GFP is discussed.     

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.     

Gender-Typed Toy Play in Dizygotic Twin Pairs: A Test of Hormone Transfer Theory

Hormone transfer theory predicts thatopposite-sex twins will be affected in utero by thehormones their twins produce. This study examines theprediction that opposite-sex dizygotic twins should showless stereotyped toy play than same-sex dizygotictwins should show less stereotyped toy play thansame-sex dizygotic twins as a result of exposure toopposite-sex hormones in utero. Participants in thisstudy included 32 male-female dizygotic twin pairs,27 female-female pairs, and 24 male-male pairs. Allranged in age from 7 to 12 years and were primarilyCaucasian and middle class. Differences in the amount of time children played with feminine,masculine, and neutral stereotyped toys during free playwere examined. Results did not support hormone transfertheory. Girls played with feminine toys more than boys and boys played with masculine toys morethan girls, but there were no significant differencesbetween children with opposite- vs. same-sextwins.     

Veterans’ Offspring’s Personality Traits and the Intergenerational Transmission of Posttraumatic Stress Symptoms

Following war and war captivity, many combat veterans and former prisoners of war (ex-POWs) may suffer from posttraumatic psychopathologies, and these may be transmitted to their offspring. Though there are considerable individual differences between offspring in this respect, the mechanisms underlying such differences remain unclear. The current longitudinal study examined the role that veterans’ offspring’s Big Five personality traits may play within this intergenerational transmission. One hundred and twenty-three dyads consisting of veterans (79 ex-POWs and 44 combat veterans) and their adult offspring were examined. Fathers’ posttraumatic stress symptoms (PTSS) and global psychiatric distress (GD) were assessed 30 and 35 years after the war, and offspring’s PTSS, GD, and Big Five personality traits were assessed 40 years after the war. Findings indicate that veterans’ psychopathologies were associated with those of their offspring. Furthermore, analyses revealed significant positive associations between offspring’s psychopathologies and their Neuroticism, and negative associations with their Agreeableness and Conscientiousness. Finally, a mediation effect was found wherein the fathers’ PTSS and GD were related to their offspring’s Neuroticism levels, and the offspring’s Neuroticism was related to their PTSS and GD levels. These findings suggest that offspring’s personality traits may indeed play a role in the transmission of posttraumatic psychopathologies from veterans to their offspring, and may explain individual differences in this respect. Specifically, high levels of Neuroticism may place offspring at risk for secondary traumatization. Possible explanations and limitations are discussed, and future research directions are suggested.     

Personal Growth and Meaning in Life Among First-Time Mothers and Grandmothers

This cross-sectional study examined personal growth and meaning in life among mothers and grandmothers who recently went through major transitions in a woman’s life. It investigated the contribution of the internal resources of perception of self (self-esteem) and perceived characteristics of the situation (cognitive appraisal of threat, challenge, and self-efficacy) and the external resource of perceived social support, as well as two background variables: age, and frequency of meetings between mothers and grandmothers. Participants were 152 first-time mothers 6–24?months after delivery, and their own mothers who were first-time grandmothers (n?=?152). The results showed differential contributions to meaning in life and personal growth in the two generations, indicating that the proposed variables can indeed explain growth and meaning in life in these life stages. They reveal not only the similarities and differences between the response of mothers and grandmothers to these parallel life transitions, but also how information about one generation may help explain the response of the other. The different patterns of associations which emerged for growth and meaning in life are also discussed.     

人格差异性的进化心理学解释

进化心理学一直热衷于人格共同性的探讨,但一些研究者也认为应该关注人格差异性,因为共同性和差异性是人格必不可分的两面。对人格差异性的进化解释比较成熟的有三种：生活历史理论、基因多样性理论和代价信号理论。生活历史理论认为是不同的环境(稳定和不稳定),造成了不同的生活历史策略(K策略和R策略),人格特质差异是这些策略的进化产物。基因多样性理论主要从基因突变和平衡选择的角度来解释人格差异性。前者强调突变基因的不可避免性引发了个性差异的存在和发展;后者强调概率的调节作用,解释了不同人格特质之所以能够并行存在的原因。代价信号理论则认为是个体拥有的先天禀赋或者资源差距导致其传递信号的能力差异,从而选择了不同的行为策略。未来研究需要加大遗传学、神经科学等方面的力度,以及研究范式的创新。     

Left or right? Sources of political orientation: the roles of genetic factors, cultural transmission, assortative mating, and personality

In this study, we used an extended twin family design to investigate the influences of genetic and cultural transmission as well as different sources of nonrandom mating on 2 core aspects of political orientation: acceptance of inequality and rejecting system change. In addition, we studied the sources of phenotypic links between Big Five personality traits and political beliefs using self- and other reports. Data of 1,992 individuals (224 monozygotic and 166 dizygotic twin pairs, 92 unmatched twins, 530 spouses of twins, 268 fathers, and 322 mothers) were analyzed. Genetically informative analyses showed that political attitudes are genetically but not environmentally transmitted from parents to offspring and that a substantial proportion of this genetic variance can be accounted for by genetic variance in personality traits. Beyond genetic effects and genotypic assortative mating, generation-specific environmental sources act to increase twins' and spouses' resemblance in political beliefs. The results suggest multiple sources of political orientations in a modern democracy.     

Race,social relationships,and mental health

Researchers often assume that the extent, quality, and effectiveness of personal relationships explain why African Americans have relatively good mental health despite experiencing high levels of stress. This study tests this assumption using data from the 1990–1992 National Comorbidity Survey. Few racial differences emerge in patterns of social relationships, and the nature and quality of social relationships do not explain African Americans’ resiliency on mental health. Several aspects of social relationships benefit African Americans’ mental health more than Whites’, but these moderating effects are insubstantial. Hence, the data do not support the assumption. If social relationships help explain the lack of racial differences in mental health, their nature and effects must be more adequately conceptualized.     

Genetic and Environmental Contributions to Individual Differences: The Three Major Dimensions of Personality

ABSTRACT This article deals with the contribution of genetic and environmental factors to individual differences in the three major dimensions of personality (Psychoticism, Extraversion, and Neuroticism) Twin studies indicate, and family studies confirm within limits, the strong genetic determination of these and many other personality factors, additive genetic variance accounting for roughly half the total phenotypic variance On the environmental side, shared family environment plays little or no part, all environmental effects being within-family Assortative mating, important in the formation of social attitudes, has little impact on personality Dominance may be important for Extraversion Epistasis (emergenesis) may account for the comparative low values of dizygotic (DZ) twins' correlations Evidence for differential heritability of traits is present, but not very strong It is concluded that behavioral genetics forms a vital part of the psychological understanding of the causes of individual differences in personality     

Does Economic Development Affect Life Satisfaction? A Spatial–Temporal Contextual Analysis in China

Social context affects people’s life satisfaction because it provides a natural reference for evaluating their own socioeconomic standing. Given their reference role, social contexts operationalized by space versus time may have very different implications. Our hypothesis is that spatial variation in economic development has little impact on life satisfaction as individuals living in different locales are unlikely to experience this variation personally, but that short-term temporal changes in economic development, on the other hand, do have an impact, as individuals in a given locale experience these changes directly. These two very different implications of spatial versus temporal social contexts are tested with an analysis of repeated survey data in 60 counties of China from 2005 to 2010. The results show that life satisfaction does not vary much with regional differences in economic development but responds positively to the local level of economic development over time. That is, the contextual effects of economic development vary greatly depending on how social context is operationalized. Temporal context matters far more than regional context where individuals’ life satisfaction is concerned.