Behavioral Genetic Analyses Research Articles

Shared and unique heritability of hippocampal subregion volumes in children and adults

Behavioral genetic analyses have not demonstrated robust, unique, genetic correlates of hippocampal subregion volume. Genetic differentiation of hippocampal longitudinal axis subregion volume has not yet been investigated in population-based samples, although this has been demonstrated in rodent and post-mortem human tissue work. The following study is the first population-based investigation of genetic factors that contribute to gray matter volume along the hippocampal longitudinal axis. Twin-based biometric analyses demonstrated that longitudinal axis subregions are associated with significant, unique, genetic variance, and that longitudinal axis subregions are also associated with significant shared, hippocampus-general, genetic factors. Our study’s findings suggest that genetic differences in hippocampal longitudinal axis structure can be detected in individual differences in gray matter volume in population-level research designs.

Behavioral genetics of temporal framing: Heritability of time perspective and its common genetic bases with major personality traits.

The present study aimed to provide a seminal behavioral genetic analysis of time perspectives (TPs). Moreover, we intended to investigate the magnitude of genetic vs. environmental components of the well-established assocations between TPs and personality features. Individual differences in temporal framing processes, referred to as TPs, are vital psychological and behavioral outcomes. Although proponents of TP theory emphasize mainly environmental origins of the tendencies to adopt certain TPs, research provides evidence for marked associations between the temporal dimensions and major personality traits that are known to be heritable. Hence, it was essential to empirically verify these claims. The article reports an analysis of genetic and environmental components of variance in TPs based on a study adopting a twin design, conducted on a sample of 393 pairs of twins (135 monozygotic and 258 dizygotic). Multivariate Cholesky decomposition supported an EA model assuming impacts of both unshared environmental factors (E) and additive genetic factors (A) across all TP dimensions, suggesting that the effects of shared environment on TPs are plausibly negligible. Heritability indices of TPs ranged between 0.51 for Present-Fatalistic and 0.62 for Present-Hedonistic, suggesting that the majority of the variance in TPs stems from genetic influences. Substantial genetic correlations were found between TPs and the Big Five personality traits. The findings provide further evidence for conceptualizing TPs as biologically based personality traits and challenge the claims that TP is mainly a product of culture, education, and personal experiences.

Nesting biology and social organisation of a silk wasp (Microstigmus rosae) from the North–West Ecuadorian Choco

Microstigmus Ducke (Hymenoptera, Apoidea, Crabronidae, Pemphredoninae) is an intriguing genus of wasp, particularly interesting for the study of social evolution as it contains the only species of apoid wasps known to exhibit eusocial behaviours. Thus far, data concerning the genetics and biology of sociality in Microstigmus are restricted to just two species. Through behavioural observations and genetic analyses, we here present a detailed report on the nesting biology and social organisation of a third species, Microstigmus rosae. Our results indicate that M. rosae nests are founded by a single female and social groups appear when emerging female offspring remain on the natal nests as helpers. Adult females mass provision their offspring and developmental data are consistent with sequential brood production, an average egg laying interval of 10 days and a brood developmental period of more than 35 days. Social group formation is atypical, with 20% of nests containing up to a maximum of four adult females and two males. Adult group size is positively correlated with the number of brood in a nest, but negatively correlated with per capita brood. The sex investment ratio was female biased. Our findings support several theories concerning the behavioural characteristics thought to be important for transitions towards sociality, namely: high genetic relatedness generated by monogamous matrifilial associations, hygienic behaviour and the potential for direct reproduction. In contrast, one hypothesised trait, progressive provisioning, is notably absent, highlighting the need for investigations into the significance of post-provisioning parental care for offspring survival in this genus.

Examining the Potential Association between Callous-Unemotional Traits and Victimization: A Behavioral Genetic Analysis

Examining the Potential Association between Callous-Unemotional Traits and Victimization: A Behavioral Genetic Analysis

Thermal antinociceptive responses to alcohol in DBA/2J and C57BL/6J inbred male and female mouse strains

BackgroundThe phenomenon of alcohol analgesia and tolerance can facilitate misuse and lead to the development of alcohol use disorder (AUD). Numerous alcohol-induced behaviors are genetically influenced; however, it is unknown if alcohol analgesia has a genetic contribution. Rodent studies have shown that alcohol responses differ vastly between two widely studied inbred strains of mice, C57BL/6 J (B6) and DBA/2 J (D2). Here, we used B6 and D2 mice as an initial behavioral genetic analysis of acute alcohol-induced antinociception. MethodsThe antinociceptive effect of orally-administered alcohol was characterized using the hot plate test in B6 and D2 mice of both sexes. Using the opioid receptor antagonist naloxone, the involvement of the opioid system was assessed. Locomotor activity and blood alcohol concentrations were also measured. Ovariectomized mice were used to evaluate the influence of ovarian sex hormones on alcohol-induced antinociception. ResultsAlcohol induced an antinociceptive effect in B6 and D2 male mice in a time- and dose-dependent manner. In addition, D2 male mice were more sensitive to the antinociceptive effect of alcohol than B6 male mice. However, locomotion is not impeded by the tested doses of alcohol in B6 mice. Female D2 and B6 mice failed to show significant antinociceptive effects in alcohol dose-response studies. In addition, alcohol-induced antinociception was still not evident in ovariectomized female mice. Male mice of both strains developed tolerance to this effect after repeated administration of alcohol. Strain differences were found in blood alcohol concentration. Finally, no difference was found in the blockade of alcohol antinociception by 2 mg/kg naloxone. ConclusionOur results indicate that the antinociceptive effects of alcohol in the hot plate test are influenced by strain and sex. These findings support further genetic analysis of alcohol-induced antinociception to identify operative mechanisms and better assess the contribution of this phenotype to AUD.

Individual differences in adolescent and young adult daily mobility patterns and their relationships to big five personality traits: A behavioral genetic analysis

Youth behavior changes and their relationships to personality have generally been investigated using self-report studies, which are subject to reporting biases and confounding variables. Supplementing these with objective measures, like GPS location data, and twin-based research designs, which help control for confounding genetic and environmental influences, may allow for more rigorous, causally informative research on adolescent behavior patterns. To investigate this possibility, this study aimed to (1) investigate whether behavior changes during the transition from adolescence to emerging adulthood are evident in changing mobility patterns, (2) estimate the influence of adolescent personality on mobility patterns, and (3) estimate genetic and environmental influences on mobility, personality, and the relationship between them. Twins aged Fourteen to twenty-two (N = 709, 55 % female) provided a baseline personality measure, the Big Five Inventory, and multiple years of smartphone GPS data from June 2016 - December 2019. Mobility, as measured by daily locations visited and distance travelled, was found via mixed effects models to increase during adolescence before declining slightly in emerging adulthood. Mobility was positively associated with Extraversion and Conscientiousness (r of 0.17–0.25, r of 0.10–0.16) and negatively with Openness (r of −0.11 - −0.13). ACE models found large genetic (A = 0.56–0.81) and small-moderate environmental (C of 0.12–0.28, E of 0.07–0.15) influences on mobility. A and E influences were highly shared across mobility measures (rg = 0.70, re = 0.58). Associations between mobility and personality were partially explained by mutual genetic influences (rg of −0.27–0.53). Results show that as autonomy increases during adolescence and emerging adulthood, we see corresponding increases in youth mobility. Furthermore, the heritability of mobility patterns and their relationship to personality demonstrate that mobility patterns are informative, psychologically meaningful behaviors worthy of continued interest in psychology.

Nostalgia and Satisfaction with Life: A Behavioral Genetic Analysis

Nostalgia, a bittersweet but predominantly positive emotion, arises from self-relevant and social memories. Evidence suggests that nostalgia is a potential source of happiness. Indeed, at the phenotypic level, this relation appears to be positive albeit tenuous. At the etiologic level, the relation is unknown. To fill this knowledge gap, we investigated the phenotypic and genetic association between nostalgia and satisfaction with life (SWL). We assessed nostalgia and SWL in 464 twin siblings, including 117 monozygotic twin pairs and 115 dizygotic twin pairs. By comparing monozygotic twins to dizygotic twins, we analyzed the genetic and environmental effects on nostalgia and SWL simultaneously. We observed a small positive association between nostalgia and SWL (rphenotypic = 0.12), with this association being strengthened after neuroticism was partialled out (rphenotypic = 0.17). More importantly, nostalgia and SWL shared some environmental (but not genetic) sources (rnon-shared environment = 0.21), which accounted for the majority (88%) of their phenotypic association. Taken together, the findings support a positive relation between nostalgia and SWL, and further uncover the bases underlying this relation. The study adds to the burgeoning literature on nostalgia and well-being.

Common genetic and environmental effects on cognitive ability, conscientiousness, self-perceived abilities, and school performance

Personal characteristics (e.g., cognitive ability (CA), conscientiousness, self-perceived abilities (SPA)) predict differences in school performance. While genetic influences on CA and conscientiousness are unequivocal, origins of SPA have long been assumed to be environmental, however substantial genetic contributions have been detected in behavioral genetic analyses. In this study, we investigate the common etiology of these three predictors and their association with school grades in math and German as well as how genetic and environmental contributions differ between age groups and school domains. The sample consists of 2101 twin pairs (aged 11 and 17) and their siblings participating in the German TwinLife study. Using a multivariate twin-sibling design, we analyze common genetic and environmental effects on CA, conscientiousness, SPA and school grades in math and German in two age groups. Results confirm genetic effects for all three predictors (42–51% for CA, 31–42% for conscientiousness, 26–48% for SPA) as well as (non-) shared environmental effects. Multivariate analyses demonstrate that the interrelation between predictors and their association with grades is largely due to common genetic effects. Additional non-shared environmental effects and differences across age groups and school domains are small. We discuss possible underlying mechanisms and implications on individual differences in school performance leading to educational inequality.

Latent, genetic, and molecular genetic structure of the Wisconsin Card Sorting Test.

The main goal of this study was to explore the latent structure and genetic basis of cognitive processes involved in the Wisconsin Card Sorting Task (WCST) within phenotypic, behavioral genetic, and molecular genetic research paradigms. The sample used in phenotypic and behavioral genetic analyses comprised 468 twins (154 monozygotic and 80 dizygotic twin pairs), while molecular genetic analyses were performed on 404 twins from the same sample. The zygosity of most twin pairs (96.8%) was determined via deoxyribonucleic acid (DNA) analysis of buccal swabs. Trained researchers administered the Wisconsin Card Sorting Test (WCST; Heaton et al., 1993) to the entire sample. A phenotypic factor analysis of WCST variables suggested a single-factor solution. Overall heritability ranged from 0.19 to 0.23 across different measures of the WCST. The presence of a single general genetic factor, which could be identified from different measures of the WCST, indicated the unity of various WCST indicators and the existence of a common basic ability. Performance on the WCST did not reveal significant differences between the three genotypes on catechol-O-methyltransferase (COMT) and dopamine receptor D2 (DRD2). Carriers of the brain-derived neurotrophic factor (BDNF) Met + genotype exhibited better performance in cognitive functions in comparison to the BDNF Met- genotype. This study highlighted similarities in the phenotypic and genetic structures of the WCST, suggesting one general factor underlying different cognitive functions. The BDNF Met + genotype showed significant main effects on different WCST measures. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Executive Functions and Impulsivity as Transdiagnostic Correlates of Psychopathology in Childhood: A Behavioral Genetic Analysis.

Executive functions (EFs) and impulsivity are dimensions of self-regulation that are both related to psychopathology. However, self-report measures of impulsivity and laboratory EF tasks typically display small correlations, and existing research indicates that impulsivity and EFs may tap separate aspects of self-regulation that independently statistically predict psychopathology in adulthood. However, relationships between EFs, impulsivity, and psychopathology may be different in childhood compared to adulthood. Here, we examine whether these patterns hold in the baseline assessment of the Adolescent Brain and Cognitive Development (ABCD) sample, a national sample of over 11,000 children (including 749 twin pairs) ages 9–10 years. We examine the phenotypic and genetic relationships among latent variables for different components of EFs and multiple facets of impulsivity. Additionally, we assess how EFs and impulsivity relate to composite measures and latent variables of psychopathology derived from parent report. EFs were weakly correlated with impulsivity, and the strength varied by impulsivity facet, emphasizing their separability. We did not identify significant genetic and environmental correlations between EFs and impulsivity. Moreover, controlling for their small relationships with each other, both EFs and some facets of impulsivity statistically predicted an Externalizing factor, attention problems, and social problems, and twin analyses suggested these relationships were genetic in origin. These findings indicate that EFs and impulsivity represent phenotypically and genetically separable aspects of self-regulation that are both transdiagnostic correlates of psychopathology in childhood.

Mating and Reproductive Success in Free-Ranging Stump-Tailed Macaques: Effectiveness of Male–Male Coalition Formation as a Reproductive Strategy

Male coalition-like formation, recently found in stump-tailed macaques (Macaca arctoides), occurs when several top-ranking males collaboratively guard females to prevent mating with other rival males and actively share secured mating opportunities with their allies. We lack a comprehensive understanding of the proximate mechanisms underlying such male coalitions, e.g., the effect of genetic relatedness. Such cooperative partner choice among males is particularly interesting in animals, such as M. arctoides, that live in matrilineal (female philopatry/male dispersal) society. Theoretically, in such a social system, females, and not males, are often related to each other by kinship. Thus, the occurrence of cooperative behavior between related females are generally common, but it would be rare between unrelated/non-kin males in such matrilineal society. Herein, for the first time, we report detailed copulatory behaviors, including mating and reproductive success, in relation to male coalition-like formation in free-ranging M. arctoides following direct behavioral observation and genetic analysis. We found that coalition-forming male–male alliances often occur among both individuals that are highly related and those that are less related. We identified two groups with different mating strategies, i.e., single-male monopoly and coalition-male monopoly groups. In both groups, nearly 80% of copulations were monopolized by a single male or by coalition males. However, the single-male monopoly strategy allows opportunistic/sneaky copulations by other males with a relatively high probability. Thus, the degree of reproductive success did not reflect mating success. In contrast, the males employing a coalition strategy successfully shared their mating and reproductive success, particularly in the largest group. Compared with single-male monopolized groups, the coalition-male monopoly groups copulated with a considerably more number of females, suggesting that coalition males can effectively guard against opportunistic/sneaky copulation by rival males. We also found that coalition-forming male–male alliances often occur regardless of the degree of kinship/relatedness, indicating the complexity and flexibility inherent in the male social bond of M. arctoides.

Social Adversity Reduces Polygenic Score Expressivity for General Cognitive Ability, but Not Height

AbstractIt has been hypothesized that even ‘perfect’ polygenic scores (PGSs) composed of only causal variants may not be fully portable between different social groups owing to gene-by-environment interactions modifying the expression of relevant variants. The impacts of such interactions involving two forms of social adversity (low socioeconomic status [SES] and discrimination) are examined in relation to the expressivity of a PGS for educational attainment composed of putatively causal variants in a large, representatively sampled and genotyped cohort of US children. A relatively small-magnitude Scarr–Rowe effect is present (SES × PGSEDU predicting General Cognitive Ability [GCA]; sR = .02, 95% CI [.00, .04]), as is a distinct discrimination × PGSEDU interaction predicting GCA (sR = −.02, 95% CI [−.05, 00]). Both are independent of the confounding main effects of 10 ancestral principal components, PGSEDU, SES, discrimination and interactions among these factors. No sex differences were found. These interactions were examined in relation to phenotypic and genotypic data on height, a prospectively more socially neutral trait. They were absent in both cases. The discrimination × PGSEDU interaction is a co-moderator of the differences posited in modern versions of Spearman’s hypothesis (along with shared environmentality), lending support to certain environmental explanations of those differences. Behavior-genetic analysis of self-reported discrimination indicates that it is nonsignificantly heritable (h2 = .027, 95% CI [−.05, .10]), meaning that it is not merely proxying some underlying source of heritable phenotypic variability. This suggests that experiences of discrimination might stem instead from the action of purely social forces.

Child Maltreatment and Substance Use: A Behavior Genetic Analysis.

Child maltreatment is a pervasive social problem often perpetuated by family members and is related to a wide array of negative life outcomes. Although substance use is an outcome commonly associated with experiences of child maltreatment, not all individuals who experience maltreatment struggle with such issues. Many individuals can positively adapt to experiences of maltreatment based on levels of resilience and susceptibility. Research suggests that genetic differences may partly explain why negative outcomes develop for some, but not for others. Few studies have examined the extent to which genetic and environmental factors influence the longitudinal association between child maltreatment and varying forms of substance use, leaving a fundamental gap in our current understanding of this association. The current study aims to address this gap by analyzing a sample of twins from the National Longitudinal Study of Adolescent to Adult Health (Add Health). Findings from a series of univariate and bivariate biometric models reveal that the longitudinal associations between maltreatment, cigarette use, and marijuana use are accounted for by additive genetic and nonshared environmental factors. Moreover, the magnitude of the contribution varies across unique subgroups of cigarette and marijuana use. Directions for future research and theoretical implications are discussed.

Understanding neighborhood disadvantage: A behavior genetic analysis

PurposeStudies have shown that disadvantaged neighborhoods are associated with higher levels of crime and delinquent behaviors. Existing explanations do not adequately address how individuals select neighborhood. Thus, the current study employed a genetically-informed design to test whether living in a disadvantaged neighborhood might be partly explained by individual characteristics, including self-control and cognitive ability. MethodA sibling subsample of N = 1573 Add Health siblings living away from their parents at Wave 4 was used in twin analyses to assess genetic and environmental effects on neighborhood disadvantage. To evaluate which individual-level variables might longitudinally predict neighborhood disadvantage, a sample of N = 12,405 individuals was used. ResultsFindings provided evidence of significant heritability (32%) of neighborhood disadvantage. In addition, a significant negative effect by adolescent cognitive ability on neighborhood disadvantage 14 years later was observed (β = −0.04, p = .002). Follow-up analyses showed a genetic effect on the association between cognitive ability and neighborhood disadvantage. ConclusionsStudy findings indicate substantial heritability of neighborhood disadvantage, showing that individuals themselves might potentially contribute to a self-selection process that explains which neighborhoods they occupy as adults.

Heteropaternal Siblings Misclassified as Dizygotic Twins: A Potential Biasing Factor for Heritability Estimates?

Heteropaternal superfecundation (HP) occurs when two or more ova are fertilized by sperm from separate males. The resulting siblings are genetically equivalent to half-siblings and share, on average, 25% of their inherited genetic material. In the absence of genetic testing HP siblings could be treated as dizygotic (DZ) twins in behavioral genetic analyses and bias heritability estimates in phenotypic decomposition models. However, the extent to which such misclassification could affect calculated estimates of heritability is currently unknown. Employing simulation analyses, the current study assessed the potential biasing impact across a variety of conditions varying by proportions of DZ twins, sample sizes, and low, moderate, and high levels of genetic and environmental contribution to phenotypic variance. Overall, the results indicated that misclassified HP siblings had minimal impact on estimates of heritability. Nonetheless, greater attention should be paid to the identification of HP siblings within existing and future twin datasets.

Genetic and environmental contribution to social dominance orientation and its overlap with HEXACO personality traits

Social dominance orientation (SDO), i.e. the preference toward egalitarian or hierarchically arranged relations within a society may be studied from social/contextual, but also dispositional perspective. The aim of the present study was to explore genetic and environmental contribution to the individual differences in SDO, and its overlap with HEXACO personality traits, both at phenotypic and latent genetic and environmental levels. The sample consisted of 830 Croatian twins aged 19 to 28 years who filled-in the self-report measures. Data analyses indicated the heritability of SDO was over 40%, with no evidence for the common environmental influences. SDO phenotypic variance substantially overlapped with Honesty-Humility, Emotionality, and Openness domains. Numerous significant correlations were found at the facet level, with the highest phenotypic overlap for the “interstitial” altruism facet. However, incremental predictive power of personality (over age and sex) was moderate: 13% and 19% of the phenotypic SDO variance was predicted by HEXACO traits at the domains and facet levels, respectively. Multivariate behavioural genetic analysis indicated that 19% and 3% of the genetic and unique environmental variance of SDO overlapped with the genetic and unique environmental variance of personality, respectively. Substantial genetic correlations of SDO with Honesty-Humility and Openness domains were found, while marginal unique environmental correlation was found for Openness domain only. The etiological overlap between SDO and personality represents an argument in favour of taking dispositional along with social/contextual perspective in explaining social behaviour.

Associations Between Physical Fitness and Brain Structure in Young Adulthood.

A comprehensive analysis of associations between physical fitness and brain structure in young adulthood is lacking, and further, it is unclear the degree to which associations between physical fitness and brain health can be attributed to a common genetic pathway or to environmental factors that jointly influences physical fitness and brain health. This study examined genotype-confirmed monozygotic and dizygotic twins, along with non-twin full-siblings to estimate the contribution of genetic and environmental factors to variation within, and covariation between, physical fitness and brain structure. Participants were 1,065 young adults between the ages of 22 and 36 from open-access Young Adult Human Connectome Project (YA-HCP). Physical fitness was assessed by submaximal endurance (2-min walk test), grip strength, and body mass index. Brain structure was assessed using magnetic resonance imaging on a Siemens 3T customized ‘Connectome Skyra’ at Washington University in St. Louis, using a 32-channel Siemens head coil. Acquired T1-weighted images provided measures of cortical surface area and thickness, and subcortical volume following processing by the YA-HCP structural FreeSurfer pipeline. Diffusion weighted imaging was acquired to assess white matter tract integrity, as measured by fractional anisotropy, following processing by the YA-HCP diffusion pipeline and tensor fit. Following correction for multiple testing, body mass index was negatively associated with fractional anisotropy in various white matter regions of interest (all | z| statistics > 3.9) and positively associated with cortical thickness within the right superior parietal lobe (z statistic = 4.6). Performance-based measures of fitness (i.e., endurance and grip strength) were not associated with any structural neuroimaging markers. Behavioral genetic analysis suggested that heritability of white matter integrity varied by region, but consistently explained >50% of the phenotypic variation. Heritability of right superior parietal thickness was large (∼75% variation). Heritability of body mass index was also fairly large (∼60% variation). Generally, to of the correlation between brain structure and body mass index could be attributed to heritability effects. Overall, this study suggests that greater body mass index is associated with lower white matter integrity, which may be due to common genetic effects that impact body composition and white matter integrity.

Genotype-Environment Correlation and Its Relation to Personality - A Twin and Family Study.

The aim of the study was to examine the Family and School Psychosocial Environment (FSPE) questionnaire in relation to a possible genotype-environment correlation and genetic mediation between the FSPE variables and personality variables, assessed by the Junior Eysenck Personality Questionnaire. A sample of 506 Swedish children aged 10-20 years from 253 families were recruited via the Swedish state population and address register and SchoolList.Eu. The children were divided into 253 pairs: 46 monozygotic twin pairs, 42 dizygotic twin pairs, 140 pairs of full siblings and 25 pairs of half-siblings. The behavioral genetic analysis showed that both FSPE factors, Warmth and Conflicts, may be partly influenced by genetic factors (suggesting genotype-environment correlation) and that nonadditive genetic factors may mediate the relationship between FSPE factors and psychoticism/antisocial personality (P). An indication of a special shared monozygotic twin environment was found for P and Lie/social desirability, but based on prior research findings this factor may have a minor influence on P and L. P and L were negatively correlated, and the relationship seems to be partly mediated by nonadditive genetic factors. Nonshared environment and measurement errors seem to be the most influential mediating factors, but none of the cross-twin cross-dimension correlations suggest a common shared environmental mediating factor.

The intergenerational transmission of suicidal behavior: an offspring of siblings study

We examined the extent to which genetic factors shared across generations, measured covariates, and environmental factors associated with parental suicidal behavior (suicide attempt or suicide) account for the association between parental and offspring suicidal behavior. We used a Swedish cohort of 2,762,883 offspring born 1973–2001. We conducted two sets of analyses with offspring of half- and full-siblings: (1) quantitative behavior genetic models analyzing maternal suicidal behavior and (2) fixed-effects Cox proportional hazard models analyzing maternal and paternal suicidal behavior. The analyses also adjusted for numerous measured covariates (e.g., parental severe mental illness). Quantitative behavior genetic analyses found that 29.2% (95% confidence interval [CI], 5.29, 53.12%) of the intergenerational association was due to environmental factors associated with exposure to maternal suicidal behavior, with the remainder due to genetic factors. Statistical adjustment for parental behavioral health problems partially attenuated the environmental association; however, the results were no longer statistically significant. Cox hazard models similarly found that offspring were at a 2.74-fold increased risk [95% CI, 2.67, 2.83]) of suicidal behavior if their mothers attempted/died by suicide. After adjustment for familial factors and measured covariates, associations attenuated but remained elevated for offspring of discordant half-siblings (HR, 1.57 [95% CI, 1.45, 1.71]) and full-siblings (HR, 1.62 [95% CI, 1.57, 1.67]). Cox hazard models demonstrated a similar pattern between paternal and offspring suicidal behavior. This study found that the intergenerational transmission of suicidal behavior is largely due to shared genetic factors, as well as factors associated with parental behavioral health problems and environmental factors associated with parental suicidal behavior.

Twins Assessing Their Own and Parental Intelligence: Examining the Raters' Agreement and the Effect of Raters' and Targets' Gender.

The goal of this study was to explore the raters’ agreement and the effect of raters’ and targets’ gender on self- and parental intelligence assessments in the sample of Croatian twins. Twins were asked to assess their own and their parents’ overall intelligence, as well as specific abilities from the Gardner’s theory of multiple intelligences. Data was analysed to explore: i) twins’ agreement in parental assessments and behavioural genetic analysis of the overall intelligence estimates; ii) gender differences in self- assessments; and iii) raters’ and targets’ gender effects on parental assessments. The twins’ mean correlation in their assessments of overall parental intelligence was .60. The differences between monozygotic and dizygotic twin correlations were nonsignificant for all of the estimated abilities, and model fitting analysis indicates that hypothesis about genetic effect on parental assessment of intelligence should be rejected. The hypotheses about males’ higher self-assessments for overall intelligence and for the masculine types of abilities - logical-mathematical, body-kinesthetic and spatial abilities - were confirmed. For the feminine types of abilities - verbal/linguistic, inter- and intra- personal intelligences - there were no significant gender effects. Both target and rater effect were found for the parental estimates of intelligence. Fathers were estimated higher on overall intelligence, logical-mathematical, body-kinesthetic and spatial abilities, while mothers were estimated higher on interpersonal and intrapersonal intelligence. The effect of the raters’ gender was found for overall intelligence as well as for inter- and intra- personal intelligences, where males gave higher estimates of parental intelligences than females.