Beyond Heritability: Twin Studies in Behavioral Research

ABSTRACT— The heritability of human behavioral traits is now well established, due in large measure to classical twin studies. We see little need for further studies of the heritability of individual traits in behavioral science, but the twin study is far from having outlived its usefulness. The existence of pervasive familial influences on behavior means that selection bias is always a concern in any study of the causal effects of environmental circumstances. Twin samples continue to provide new opportunities to identify causal effects with appropriate genetic and shared environmental controls. We discuss environmental studies of discordant twin pairs and twin studies of genetic and environmental transactions in this context.     

Health Behaviors and Psychological Distress in Women Initiating BRCA1/2 Genetic Testing: Comparison with Control Population

The study objective was to compare breast cancer screening practices, lifestyle behaviors and psychological distress among 640 women initiating BRCA1/2 testing to those among 9,498 similarly-aged women from the general population. Health behaviors and psychological distress were reported in a self-administered questionnaire at pre-test genetic counseling. Regression analyses indicate that high-risk women were more frequently performing breast cancer screening and, in the case of those previously diagnosed with cancer, were more likely to be non-smokers and physically active than women from general population. However, women initiating BRCA1/2 testing were significantly more distressed than controls. Globally, high-risk women seemed to be well informed about recommendations for women who are at high risk and to have access to screening adapted to their risk level. Given their significant psychological distress, providing minimal psychosocial support to all women undergoing BRCA1/2 testing at pre-test genetic counseling is relevant.     

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.     

Genetic and environmental influences on religiousness: findings for retrospective and current religiousness ratings

Estimates of the degree of genetic and environmental influences on religiousness have varied widely. This variation may, in part, be due to age differences in the samples under study. To investigate the heritability of religiousness and possible age changes in this estimate, both current and retrospective religiousness were assessed by self-report in a sample of adult male twins (169 MZ pairs and 104 DZ pairs, mean age of 33 years). Retrospective reports of religiousness showed little correlation difference between MZ (r=.69) and DZ (r=.59) twins. Reports of current religiousness, however, did show larger MZ (r=.62) than DZ (r=.42) similarity. Biometric analysis of the two religiousness ratings revealed that genetic factors were significantly weaker (12% vs. 44%) and shared environmental factors were significantly stronger (56% vs. 18%) in adolescence compared to adulthood. Analysis of internal and external religiousness subscales of the total score revealed similar results. These findings support the hypothesis that the heritability of religiousness increases from adolescence to adulthood.     

Normal and abnormal personality traits: evidence for genetic and environmental relationships in the Minnesota Study of Twins Reared Apart

ABSTRACT Recent studies have demonstrated substantial correlations between normal and abnormal personality traits. Yet little is known about how these correlations are mediated genetically and environmentally: Do normal and abnormal personality traits stem from the same underlying genes and environments? We addressed this question using data from 128 monozygotic and dizygotic twin pairs in the Minnesota Study of Twins Reared Apart (MISTRA). Additive genetic and nonshared environmental correlations between scales of the Minnesota Multiphasic Personality Inventory (MMPI)—an index of abnormal personality—and the Multidimensional Personality Questionnaire (MPQ)—an index of normal personality—were estimated. Results indicated that phenotypic correlations between normal and abnormal personality were mediated by genetic as well as environmental factors, although the magnitude of genetic mediation tended to be larger overall. Moreover, the patterns of phenotypic, genetic, and environmental relationships among the scales were similar, suggesting that influences on normal and abnormal personality act through systems common to both. It is suggested that future research focus on the neurogenetic substrates of these shared systems and how dysfunction in these systems influences development of disordered personality.     

An intentional cohesion call in male chimpanzees of Budongo Forest

Animal Cognition - Many social animals travel in cohesive groups but some species, including chimpanzees, form flexible fission–fusion systems where individuals have some control over group...     

Nymphet or Lolita? A Gender Analysis of Online Child Pornography Websites

ABSTRACT

Previous research on child pornography has primarily focused on the consumption and distribution of the material – the consumer side. In this study, we turn the focus on the content of child pornography websites. While some research assessed the content, there was little consideration of gender. This paper assesses whether gender is important in correlating the presence of images of child exploitation in websites. The 300 websites examined were either directly, or indirectly connected to a known child pornography website. Results suggest that, although the majority of websites in the sample were oriented toward boy-related content, 1) the presence of girl keywords, and 2) an indicator of the sexualization of young girls were both associated with websites known to contain illegal images.