Reconsidering the Heritability of Intelligence in Adulthood: Taking Assortative Mating and Cultural Transmission into Account

Heritability estimates of general intelligence in adulthood generally range from 75 to 85%, with all heritability due to additive genetic influences, while genetic dominance and shared environmental factors are absent, or too small to be detected. These estimates are derived from studies based on the classical twin design and are based on the assumption of random mating. Yet, considerable positive assortative mating has been reported for general intelligence. Unmodeled assortative mating may lead to biased estimates of the relative magnitude of genetic and environmental factors. To investigate the effects of assortative mating on the estimates of the variance components of intelligence, we employed an extended twin-family design. Psychometric IQ data were available for adult monozygotic and dizygotic twins, their siblings, the partners of the twins and siblings, and either the parents or the adult offspring of the twins and siblings (N = 1314). Two underlying processes of assortment were considered: phenotypic assortment and social homogamy. The phenotypic assortment model was slightly preferred over the social homogamy model, suggesting that assortment for intelligence is mostly due to a selection of mates on similarity in intelligence. Under the preferred phenotypic assortment model, the variance of intelligence in adulthood was not only due to non-shared environmental (18%) and additive genetic factors (44%) but also to non-additive genetic factors (27%) and phenotypic assortment (11%).This non-additive nature of genetic influences on intelligence needs to be accommodated in future GWAS studies for intelligence

Examining the Link Between Domestic Violence Victimization and Loneliness in a Dutch Community Sample: A Comparison Between Victims and Nonvictims by Type D Personality

The current study investigated whether differences in loneliness scores between individuals with a distressed personality type (type D personality) and subjects without such a personality varied by domestic violence victimization. Participants (N = 625) were recruited by random sampling from the Municipal Basic Administration of the Dutch city of ‘s-Hertogenbosch and were invited to fill out a set of questionnaires on health status. For this study, only ratings for domestic violence victimization, type D personality, feelings of loneliness, and demographics were used. Statistical analyses yielded main effects on loneliness for both type D personality and history of domestic violence victimization. Above and beyond these main effects, their interaction was significantly associated with loneliness as well. However, this result seemed to apply to emotional loneliness in particular. Findings were discussed in light of previous research and study limitations

Sense of place amongst adolescents and adults in two rural Australian towns: the discriminating features of place attachment, sense of community and place dependence in relation to place identity

This study investigates whether dimensions of sense of place can discriminate those residents who identify with their rural town, and prefer to stay, from those who do not, and whether patterns of association between these dimensions differ between adolescent and adult residents. Participants were 246 adults and 365 adolescents in two remote rural towns in Australia. Place identity was determined from residents’ responses on a single item, ‘I would really rather live in a different town. This one is not the place for me.’ Three groups were classified: those agreeing, undecided and disagreeing with the statement. Discriminating variables were place attachment (emotional bonding and behavioural commitment), sense of community (affiliation and belonging) and place dependence (available activities, quality and quality comparison with alternative communities). A direct discriminant function analysis showed 76.4 per cent of adults were correctly classified from one discriminant function accounting for 92 per cent of the variance. Indicators of dependence, belonging, behavioural commitment and emotional bonding, loaded above 0.45. Sixty-two per cent of adolescents were correctly classified from one discriminant function accounting for 93.6 per cent of the variance. Indicators of dependence and belonging loaded 0.45 and above. Discussion considers distinguishing dimensions of sense of place and identifying associations amongst them as ways to explore the experience of community in everyday life

The Neighbourhood Youth Inventory: development and validation

This paper describes the development and validation of an inventory to uncover youths' experiences in their neighbourhoods. The Neighbourhood Youth Inventory (NYI) was developed from conversations with youths in Grades 7, 9 and 11. This paper reports the psychometric analyses of the NYI. Responses from 934 youths (511 urban, 423 rural) to the NYI resulted in a four-factor solution. This solution was stable across responses from youths in Grades 7, 9 and 11, and for urban and rural youths. Cronbach alphas ranged from 0.64 to 0.94. Construct, convergent and discriminant validity of the NYI subscales are demonstrated. Using the NYI we will be able to assess youths' experiences within their neighbourhoods, which may contribute to a more ecological understanding of healthy developmental outcomes beyond family, peer and school environments