Christian Kandler

It has been argued that facets do not represent the bottom of the personality hierarchy-even more specific personality characteristics, nuances, could be useful for describing and understanding individuals and their differences. Combining 2 samples of German twins, we assessed the consensual validity (correlations across different observers), rank-order stability, and heritability of nuances. Personality nuances were operationalized as the 240 items of the Revised NEO Personality Inventory (NEO-PI-R). Their attributes were examined by analyzing item residuals, controlling for the variance of the facet the item had been assigned to and all other facets. Most nuances demonstrated significant (p < .0002) cross-method agreement and rank-order stability. A substantial proportion of them (48% in self-reports, 20% in informant ratings, and 50% in combined ratings) demonstrated a significant (p < .0002) component of additive genetic variance, whereas evidence for environmental influences shared by twins was modest. Applying a procedure to estimate stability and heritability of true scores of item residuals yielded estimates comparable with those of higher-order personality traits, with median estimates of rank-order stability and heritability being .77 and .52, respectively. Few nuances demonstrated robust associations with age and gender, but many showed incremental, conceptually meaningful, and replicable (across methods and/or samples) predictive validity for a range of interest domains and body mass index. We argue that these narrow personality characteristics constitute a valid level of the personality hierarchy. They may be especially useful for providing a deep and contextualized description of the individual, but also for the prediction of specific outcomes. (PsycINFO Database Record

Both genetic and environmental factors are known to affect body mass index (BMI), but detailed understanding of how their effects differ during childhood and adolescence is lacking. We analyzed the genetic and environmental contributions to BMI variation from infancy to early adulthood and the ways they differ by sex and geographic regions representing high (North America and Australia), moderate (Europe), and low levels (East Asia) of obesogenic environments. Data were available for 87,782 complete twin pairs from 0.5 to 19.5 y of age from 45 cohorts. Analyses were based on 383,092 BMI measurements. Variation in BMI was decomposed into genetic and environmental components through genetic structural equation modeling. The variance of BMI increased from 5 y of age along with increasing mean BMI. The proportion of BMI variation explained by additive genetic factors was lowest at 4 y of age in boys (a(2) = 0.42) and girls (a(2) = 0.41) and then generally increased to 0.75 in both sexes...

Height variation is known to be determined by both genetic and environmental factors, but a systematic description of how their influences differ by sex, age and global regions is lacking. We conducted an individual-based pooled analysis of 45 twin cohorts from 20 countries, including 180,520 paired measurements at ages 1-19 years. The proportion of height variation explained by shared environmental factors was greatest in early childhood, but these effects remained present until early adulthood. Accordingly, the relative genetic contribution increased with age and was greatest in adolescence (up to 0.83 in boys and 0.76 in girls). Comparing geographic-cultural regions (Europe, North-America and Australia, and East-Asia), genetic variance was greatest in North-America and Australia and lowest in East-Asia, but the relative proportion of genetic variation was roughly similar across these regions. Our findings provide further insights into height variation during childhood and adolesc...

This multitrait multimethod twin study examined the structure and sources of individual differences in creativity. According to different theoretical and metrological perspectives, as well as suggestions based on previous research, we expected 2 aspects of individual differences, which can be described as perceived creativity and creative test performance. We hypothesized that perceived creativity, reflecting typical creative thinking and behavior, should be linked to specific personality traits, whereas test creativity, reflecting maximum task-related creative performance, should show specific associations with cognitive abilities. Moreover, we tested whether genetic variance in intelligence and personality traits account for the genetic component of creativity. Multiple-rater and multimethod data (self- and peer reports, observer ratings, and test scores) from 2 German twin studies-the Bielefeld Longitudinal Study of Adult Twins and the German Observational Study of Adult Twins-we...

Despite cross-cultural universality of core human values, individuals differ substantially in value priorities, whereas family members show similar priorities to some degree. The latter has often been attributed to intrafamilial socialization. The analysis of self-ratings on eight core values from 399 twin pairs (ages 7-11) and their biological parents (388 mothers, 249 fathers; ages 26-65) allowed the disentanglement of environmental from genetic transmission accounting for family resemblance in value orientations. Results indicated that parent-child similarity is primarily due to shared genetic makeup. The primary source of variance in value priorities represented environmental influences that are not shared by family members. These findings do not provide evidence for parental influences beyond genetic influences contributing to intrafamilial similarity in value priorities.

A trend toward greater body size in dizygotic (DZ) than in monozygotic (MZ) twins has been suggested by some but not all studies, and this difference may also vary by age. We analyzed zygosity differences in mean values and variances of height and body mass index (BMI) among male and female twins from infancy to old age. Data were derived from an international database of 54 twin cohorts participating in the COllaborative project of Development of Anthropometrical measures in Twins (CODATwins), and included 842,951 height and BMI measurements from twins aged 1 to 102 years. The results showed that DZ twins were consistently taller than MZ twins, with differences of up to 2.0 cm in childhood and adolescence and up to 0.9 cm in adulthood. Similarly, a greater mean BMI of up to 0.3 kg/m2 in childhood and adolescence and up to 0.2 kg/m2 in adulthood was observed in DZ twins, although the pattern was less consistent. DZ twins presented up to 1.7% greater height and 1.9% greater BMI than ...

Jüngste Ergebnisse konnten zeigen, dass Freizeitinteressen relativ wenig mit Berufsinteressen konvergieren und dass die Ausübung von Freizeitinteressen positive Konsequenzen nach sich ziehen (z.B. steigende Lebenszufriedenheit). Leider existierte bisher kein entsprechendes Messinstrument, welches eine breite aber auch ökonomische Messung von Freizeitinteressen sowie für einen breiten Erwachsenenaltersbereich differenzierte Untersuchungen von Freizeitinteressen im deutschen Sprachraum erlaubt. Aus diesem Grund wurde das Fragebogen-Inventar für Freizeitinteressen (FIFI) für Erwachsene entwickelt. Anhand exploratorischer Faktorenanalysen ließen sich 21 primäre und fünf sekundäre Freizeitinteressendimensionen an einer Stichprobe von 836 Erwachsenen (18-94 Jahre) extrahieren. Mithilfe konfirmatorischer Faktorenanalysen wurden die fünf übergeordneten Dimensionen zweiter Ordnung bestätigt. Darauf aufbauend wurden 21 Primärskalen und fünf Sekundärskalen gebildet, welche befriedigende bis gu...

ABSTRACT An established position, long recognized in the literature, maintains that political party identification (PID) arises mainly from familial socialization and has a major impact on political outlooks and behaviors. An alternative view, also entrenched in the literature, holds that the direction of causation may go the other way, with political orientations influencing PID insofar as individuals seek out parties that match their ideological viewpoints. Here we use univariate and multivariate twin modeling to examine the underlying etiology assumed by those two positions, and introduce a new perspective that may help researchers make sense of PID, political orientations, and the relationships between them. Our findings indicate that: (1) PID is substantially heritable; and (2) there is empirical support for a model in which genetic and environmental factors influence political orientations, which in turn affect PID.

ABSTRACT Konservativ oder progressiv? Hierarchie oder Gleichheit? In unserem politischen Denken und Handeln werden wir durch Medien, Bildung und vor allem durch wichtige Bezugspersonen wie Familie und Freunde beeinflusst. Doch kann es sein, dass es schon genetisch zu einem gewissen Grad angelegt ist, welche politischen Ansichten wir vertreten und für welche Partei mit welcher Ideologie und mit welchem Wahlprogramm wir uns entscheiden? LINK: http://de.in-mind.org/article/rechts-oder-links-wie-gene-unsere-politische-orientierung-beeinflussen

This study quantified genetic and environmental roots of variance in prejudice and discriminatory intent toward foreign nationals and examined potential mediators of these genetic influences: right-wing authoritarianism (RWA), social dominance orientation (SDO), and narrow-sense xenophobia (NSX). In line with the dual process motivational (DPM) model, we predicted that the two basic attitudinal and motivational orientations-RWA and SDO-would account for variance in out-group prejudice and discrimination. In line with other theories, we expected that NSX as an affective component would explain additional variance in out-group prejudice and discriminatory intent. Data from 1,397 individuals (incl. twins as well as their spouses) were analyzed. Univariate analyses of twins' and spouses' data yielded genetic (incl. contributions of assortative mating) and multiple environmental sources (i.e., social homogamy, spouse-specific, and individual-specific effects) of variance in negat...

ABSTRACT This study examined genetic and environmental sources of variance in two core political attitudes: acceptance of inequality and resistance to change. Based on an extended twin family design including twins’ parents and spouses, genetic and environmental transmissions as well as different sources of spouse correlations were taken into account. Furthermore, I examined the proportion of genetic and environmental variance in political attitudes that could be accounted for by genetic and environmental variance in Big Five personality traits using selfand other reports. Analyses revealed that variance in political attitudes showed multiple environmental (e.g., generation-specific social homogamy, spouse- and twin-specific effects) and genetic sources (e.g., additive effects and epistatic interaction, genotypic assortative mating). A substantial proportion of genetic variance could be accounted for by genetic variance in personality traits. Acceptance of inequality showed negative links to openness and agreeableness. Resistance to change was positively related to extraversion and conscientiousness and negatively related to openness. These links were primarily mediated by genetic effects. The results provide support for multiple sources of variance in political attitudes and for the position that Big Five personality traits and political attitudes are systematically related due to common genetic factors.

ABSTRACT There is an ongoing debate among political scientists and others about the relationship between partisan attachment (i.e., affiliation or identification with a particular political party) and political orientations. An established position, long recognized in the literature, maintains that partisanship is the lens through which people view the political world. According to that perspective, partisanship is stable over time and influences political choices and ideological positions. A competing interpretation maintains that partisan attachment is an outcome or choice based on one’s political attitudes. This view maintains that individuals seek out parties that match their political outlooks and orientations. The first approach assumes that the flow of causation goes from partisan attachment to political orientations; the second that it goes in the opposite direction. To the best of our knowledge, behaviour genetic methods have never been brought to bear on this issue. To rectify that shortcoming, this paper uses data from the 2008 Minnesota Twin Study to conduct Cholesky decomposition and direction of causation analysis to address the problem. Four hypotheses are tested: (1) a correlational model in which all latent factors affecting partisanship also affect political orientations; (2) a model allowing for reciprocal causation; (3) a unidirectional model where partisanship affects political orientations; and (4) a unidirectional model in which political orientations affect partisanship.

ABSTRACT Different types of continuity and change have revealed interesting developmental patterns of personality traits across the life span. The stability (i.e., rank-order, individual, and profile continuity) of personality traits tends to increase from .30 in childhood until it plateaus between .70 and .80 in middle adulthood (Roberts & DelVecchio, 2000; Terracciano, McCrae, & Costa, 2010). The continuity finally appears to decrease in old age (Lucas & Donnellan, 2011). Mean-level and individual-level change occur across the entire life span and stability tends to decrease as the time intervals between occasions of personality assessment increase (Fraley & Roberts, 2005; Soto, John, Gosling, & Potter, 2011). These patterns show that personality development is a lifelong process. Though personality is relatively stable in middle adulthood, personality change is possible in every age, in particular in young and old ages, and the more time goes by, the more change is likely. Yet the sources of these patterns are unknown. Some theories suggest that the patterns of personality continuity and change may result from age-graded social roles, individual life experiences and major life transitions reflecting an environmental maturation to a socially and culturally functional identity (Roberts & Jackson, 2008; Roberts, Wood, & Caspi, 2008). Other theories, however, explain continuity by genetic set-points and change by biological maturation and short-term but reversible environmental changes (Carey, 2002; McCrae & Costa, 2008). Whereas phenotypic findings provide partial support for both perspectives on personality development, genetically informative and environmentally sensitive longitudinal studies across different age cohorts allow a differentiated picture of genetic and environmental sources of personality development. I will give a short overview of the genetic and environmental contributions to the rank-order stability and change of Neuroticism and Extraversion (Kandler, 2012). Both genetic and environmental factors contribute to continuity and change, but genetic factors represent the primary source of continuity and appear to affect change only in younger decades of life, whereas environmental influences appear to represent a lifelong source of personality development. Heritability of Neuroticism and Extraversion progressively decreases after people enter adulthood due to an increase of environmental variance compared to the genetic variance. The findings indicate a model of personality development that integrates genetically driven development (e.g., niche-picking) and social maturation (e.g., changes in social roles and social identity formation). Personality development is a complex affair. We can only understand the complete picture, if we focus on both genetic and environmental processes as well as the complex interplay between nature and nurture (e.g., processes of individual adaptation to maintain the created niches and the functionality of identity).

ABSTRACT The controversial construct posttraumatic growth as positive personality change comes along with numerous conceptual and methodological problems, which have vividly been outlined in the target article by Jayawickreme and Blackie. As we point out here, existing empirical results also contradict the paradoxical hypothesis of an interrelation between negative life events and positive personality change. Given the oppressive evidence against this paradox, we propose some adjustments of the concept and suggest three areas of personality research in which traumatic experiences might show great promise for positive personality changes.

ABSTRACT Since the pioneering work of Eaves and Eysenck (1974), it has consistently been found that socio-political attitudes are genetically influenced. More recently, researchers have sought to clarify the nature of those genetic effects. In particular, they have examined the role of basic personality traits (Kandler et al. 2012; Verhulst et al. 2012). In an ongoing cross-cultural study based on German, Japanese, and US twin data, we focused on the sources and direction of the association between the Big Five personality traits (Neuroticism, Extraversion, Openness, Agreeableness, and Conscientiousness) and political orientations. The latter are typically treated as either a single left–right dimension or divided into two core aspects: resistance to change (or authoritarian conservatism) and acceptance of inequality (or social dominance orientation). Political attitudes were consistently associated with Openness, Conscientiousness, and Agreeableness in all three samples. These links were primarily due to common genetic factors. However, our direction-of-causation analyses cast doubt on the conventional wisdom that personality traits cause socio-political attitudes. The findings provide support for the position that personality traits and core socio-political attitudes are systematically related but distinct elements of an individual’s identity.