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     

多巴胺相关基因甲基化、家庭环境与创造力的关系

“遗传与环境”的争论一直是创造力研究的核心问题, 但目前对于环境以及遗传与环境交互作用对创造力影响的分子生物机制还未有研究涉及。近年来, 随着表观遗传学的兴起, 揭示影响心理行为的表观遗传机制现已成为心理学研究的热点。作为环境与基因组之间的纽带, 表观遗传学研究为揭示环境以及遗传与环境交互作用对创造力影响的分子生物机制提供了机遇。本研究以多巴胺相关基因、家庭环境以及两者对于创造力的交互作用为切入点, 对影响创造力的表观遗传机制进行考察, 并在此基础之上, 对环境以及遗传与环境交互作用对创造力影响的分子生物机制进行探索。具体研究内容包括：(1)通过对多巴胺相关基因甲基化模式与创造力关系的系统考察, 筛选出甲基化模式与创造力有关的基因; (2)对筛选出的基因, 进一步考察其甲基化模式在家庭环境及其遗传多态性与家庭环境交互作用对创造力影响中的中介作用。本研究有助于揭示创造力的表观遗传机制, 深化关于遗传与环境对创造力影响的作用机制的理解。     

Inter-individual differences in sport refereeing: A review of theory and practice

Most studies on sport officials ignore the variance of the data in terms of individual differences. Here we highlight the need to focus on these differences in refereeing as the main point and goal of the current review. We argue that the study of individual differences is important for referee selection, development and performance evaluation. We present the available research on differences related to referee communication styles, types of interactions, and game management. We regard expertise and experience level as a key contributor to individual differences. Given the gap in research around the in-group variance, we discuss new directions for research and further recommendations for the field. We suggest that the areas in which more research and practice will inform our selection, training, and evaluation processes are communication and personal communication style, while having more flexibility in applying different refereeing styles to facilitate performance in different contexts.     

The impact of emotional stress early in life on adult voluntary ethanol intake-results of maternal separation in rats

The combination of genetic and environmental factors determines the individual vulnerability for excessive ethanol intake, possibly leading to dependence. The environmental influences early in life represent examples of determinant factors for adult behaviour and can be protective as well as risk factors. Maternal separation is one model to examine the long-term consequences of early environmental experiences on neurochemistry and behaviour, including drug-taking behaviour in experimental animals. In the present review, findings from studies using repeated short and prolonged periods of maternal separation, with emphasis on effects on voluntary ethanol intake in rats with or without a genetic predisposition for high voluntary ethanol intake, are summarized. Despite some contradictory results, the general picture emerging shows that short periods of maternal separation during the postnatal period result in a lower adult voluntary ethanol intake in male rats. Prolonged periods of maternal separation were found to induce a high voluntary ethanol intake in male rats, including rats with a genetic predisposition for high ethanol intake. Results from the literature also show that changes were not just related to time of separation but were also related to the degree of handling. Interestingly, in terms of voluntary ethanol intake, female rats were generally not affected by postnatal maternal separation. The reasons for these sex differences need further investigation. In terms of neurobiological consequences of maternal separation, conclusive data are sparse and one of the future challenges will, therefore, be to identify and characterize underlying neurobiological mechanisms, especially in the individual animal.     

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.     

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.     

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.     

Why Are Siblings So Different? The Significance of Differences in Sibling Experiences Within the Family

Siblings, who are 50% similar genetically and grow up within the same family, nevertheless differ markedly in personality and psychopathology, and most of these sibling differences cannot be explained by genetic factors. These findings from the field of behavioral genetics imply that within-family processes that lead to sibling differences, called nonshared environment, are crucial for understanding environmental influences on individual development. Such nonshared environmental influences cannot be identified by the conventional strategy of comparing one child per family on a family-by-family basis; what is needed are studies of siblings that focus on why they are so different. The implications of these findings for investigating family process are outlined, and research is reviewed that explores the extent to which siblings in a family have different experiences, and that begins to assess links between such differential experiences and developmental outcomes.     

Sex differences in early verbal and non‐verbal cognitive development

The present study of over 3000 2‐year‐old twin pairs used a sex‐limitation model to examine genetic and environmental origins of sex differences in verbal and non‐verbal cognitive ability. Girls scored significantly higher on both measures (p<0.0001), although gender only accounted for approximately 3% of the variance in verbal ability and 1% of the variance in non‐verbal cognitive ability. For the verbal measure boys showed greater heritability than girls. Also the twin‐pair correlation is significantly lower for opposite‐sex twins than for non‐identical same‐sex twins. This indicates that individual differences in verbal ability include some sex‐specific factors. Non‐verbal cognitive ability did not differ in aetiology for boys and girls. We conclude that genetic and environmental influences differ for girls and boys for early verbal but not non‐verbal development.     

What gene-environment interactions can tell us about social competence in typical and atypical populations

Social competence is a complex human behaviour that is likely to involve a system of genes that interacts with a myriad of environmental risk and protective factors. The search for its genetic and environmental origins and influences is equally complex and will require a multidimensional conceptualization and multiple methods and levels of analysis. Behavioural genetic research can begin to address the fundamental yet complex question of how children develop social competence by uncovering the various influences on social development and disentangling variance due to multiple genes, environments and experiences. In this paper, we review the current status of research on sociability, face recognition, emotion recognition, and theory of mind (TOM)--well defined and measured constructs that are likely to be useful indices for detecting genetic and environmental influences on social competence. We also propose specific milestones as indices of further progress in the field: the development of an operational definition of the construct of social competence, the identification of social endophenotypes-psychological processes that are validly and reliably measured components of social competence, and improving specificity and homogeneity with regard to social endophenotypes within a population of study by employing 'extreme social phenotypes'. These efforts will lead to a better understanding of the specific contributions to the normal variation of social competence in the general population as well as to atypical social development.     

抑郁遗传效应的发展动态性

抑郁的遗传效应存在发展动态性。一方面,在发展过程中,抑郁的遗传率会发生改变,抑郁的风险基因及其与环境的交互作用模式也存在动态变化。另一方面,遗传因素会影响抑郁的发展变化模式。通过梳理既有相关研究,本文从生理成熟因素、表观遗传和发展级联效应三方面分析抑郁遗传效应发展动态性的原因。未来研究应区分重要发展阶段,增加脑功能、性激素、神经生物蛋白以及表观遗传等指标考察抑郁遗传效应的变化模式及其发生机制。     

The growth of developmental thought: Implications for a new evolutionary psychology

Evolution has come to be increasingly discussed in terms of changes in developmental processes rather than simply in terms of changes in gene frequencies. This shift is based in large part on the recognition that since all phenotypic traits arise during ontogeny as products of individual development, a primary basis for evolutionary change must be variations in the patterns and processes of development. Further, the products of development are epigenetic, not just genetic, and this is the case even when considering the evolutionary process. These insights have led investigators to reconsider the established notion of genes as the primary cause of development, opening the door to research programs focused on identifying how genetic and non-genetic factors coact to guide and constrain the process of development and its outcomes. I explore this growth of developmental thought and its implications for the achievement of a unified theory of heredity, development, and evolution and consider its implications for the realization of a new, developmentally based evolutionary psychology.     

Genetic and environmental influences on the positive traits of the values in action classification,and biometric covariance with normal personality

Virtually all human individual differences have been shown to be moderately heritable. Much of this research, however, focuses on measures of dysfunctional behavior and relatively fewer studies have focused on positive traits. The values in action (VIA) project is a comprehensive and ambitious classification of 24 positive traits, also known as character strengths (Peterson, C., & Seligman, M. E. P. (2004). Character strengths and virtues: A handbook and classification. Washington, DC: American Psychological Association), the majority of which have received no behavior genetic attention. Using a sample of 336 middle-aged twins drawn from the Minnesota Twin Registry who completed the VIA inventory of strengths, we detected significant genetic and non-shared environmental effects for 21 of 24 character strengths with little evidence of shared environmental contributions. Associations with a previously administered measure of normal personality found moderate phenotypic overlap and that genetic influences on personality traits could account for most, but not all, of the heritable variance in character strengths.     

The contribution of imaging genetics to the development of predictive markers for addictions

A key challenge for intervention and prevention of addictions is the identification of genetic, neurobiological and cognitive risk profiles that can predict which adolescents are at risk for addiction. Abnormalities in reinforcement behaviour have been linked to addiction vulnerability and imaging genetic studies have begun to elucidate the mechanisms by which genetic and environmental factors influence brain function underlying individual variability in reinforcement behaviour. Most studies have examined associations between a few well-characterised candidate polymorphisms and task-related brain activation differences in individual regions of interest. Here we propose that integrating the imaging genetic strategy with biological network approaches and longitudinal adolescent designs in large multi-centre samples may offer promising opportunities to identify risk markers for early diagnosis, progression and prediction of addictions.     

On the heritability of inspection time and its covariance with IQ: a twin study

Using the classical twin design, this study investigates the influence of genetic factors on the large phenotypic variance in inspection time (IT), and whether the well established IT–IQ association can be explained by a common genetic factor. Three hundred ninety pairs of twins (184 monozygotic, MZ; 206 dizygotic, DZ) with a mean age of 16 years participated, and 49 pairs returned approximately 3 months later for retesting. As in many IT studies, the pi figure stimulus was used and IT was estimated from the cumulative normal ogive. IT ranged from 39.4 to 774.1 ms (159±110.1 ms) with faster ITs (by an average of 26.9 ms) found in the retest session from which a reliability of .69 was estimated. Full-scale IQ (FIQ) was assessed by the Multidimensional Aptitude Battery (MAB) and ranged from 79 to 145 (111±13). The phenotypic association between IT and FIQ was confirmed (−.35) and bivariate results showed that a common genetic factor accounted for 36% of the variance in IT and 32% of the variance in FIQ. The maximum likelihood estimate of the genetic correlation was −.63. When performance and verbal IQ (PIQ & VIQ) were analysed with IT, a stronger phenotypic and genetic relationship was found between PIQ and IT than with VIQ. A large part of the IT variance (64%) was accounted for by a unique environmental factor. Further genetic factors were needed to explain the remaining variance in IQ with a small component of unique environmental variance present. The separability of a shared genetic factor influencing IT and IQ from the total genetic variance in IQ suggests that IT affects a specific subcomponent of intelligence rather than a generalised efficiency.     

IQ heritability estimation: analyzing genetically-informative data with structural equation models

When analyzing genetic data, Structural Equations Modeling (SEM) provides a straightforward methodology to decompose phenotypic variance using a model-based approach. Furthermore, several models can be easily implemented, tested, and compared using SEM, allowing the researcher to obtain valuable information about the sources of variability. This methodology is briefly described and applied to re-analyze a Spanish set of IQ data using the biometric ACE model. In summary, we report heritability estimates that are consistent with those of previous studies and support substantial genetic contribution to phenotypic IQ; around 40% of the variance can be attributable to it. With regard to the environmental contribution, shared environment accounts for 50% of the variance, and non-shared environment accounts for the remaining 10%. These results are discussed in the text.     

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.     

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.     

Epigenetic inheritance and the intergenerational transfer of experience

Currently, behavioral development is thought to result from the interplay among genetic inheritance, congenital characteristics, cultural contexts, and parental practices as they directly impact the individual. Evolutionary ecology points to another contributor, epigenetic inheritance, the transmission to offspring of parental phenotypic responses to environmental challenges-even when the young do not experience the challenges themselves. Genetic inheritance is not altered, gene expression is. Organismic pathways for such transmission exist. Maternal stress during the latter half of a daughter's gestation may affect not only the daughter's but also grand-offspring's physical growth. The author argues that temperamental variation may be influenced in the same way. Implications for theory and research design are presented along with testable predictions.     

Automatic activation of individual differences: A test of the gatekeeper model in the domain of spontaneous helping

The influence of stable individual differences on behaviour need not solely rely upon deliberative processes but can also be exerted through automatic associative processes. In this contribution, three studies that illustrate the role of individual differences in automaticity are presented in the domain of helping behaviour. The first study provides evidence both for a double dissociation and for an additive pattern of implicit and explicit measures in predicting relevant altruistic behaviours. The subsequent two studies show that when the concept of altruism is subliminally primed, individual differences in implicit attitudes significantly predict behaviour. The results are in line with the gatekeeper model, and their implications are discussed focusing on the key role of individual differences in modulating automaticity effects. Copyright © 2011 John Wiley & Sons, Ltd.