Researchers have proposed that culture significantly influences perceived stress (PS). To date, however, twin studies on PS have been conducted mostly in western, individualistic cultures, which demonstrate that PS due to controllable (personal) life events is more heritable than PS due to uncontrollable (network) life events. This study aimed to investigate genetic and environmental influences on PS in South Korean twins. South Korea practices a dominant collectivist culture. In total, 1372 twin individuals (mean age = 22.4 ± 2.5 years) completed an online survey on PS, which consisted of the scales, Friendship, Academic Stress, Future Career, Family Conflicts, and Family Financial Difficulties (FFD). Friendship, Academic Stress, and Future Career can be considered PS due to personal life events, and Family Conflict and FFD, PS due to network life events. The general sex-limitation model-fitting analysis revealed the absence of qualitative or quantitative sex differences in genetic and environmental influences. Specifically, additive genetic influences were predominant for Friendship (63%), Academic Stress (67%), and Future Career (57%) for both sexes, with the remaining variance attributable to nonshared environmental influences. In contrast, shared environmental influences were largest for Family Conflict (47% for both genders) and FFD (64% for males, 63% for females) with no significant genetic effects. Despite known cultural differences in the means and variances of PS, South Korean twins exhibited significant genetic effects in PS due to personal life events and large shared environmental effects in PS due to network life events, which is similar to western samples.

Worldwide data indicate a growing number of energy homeostasis disorders, which are especially dangerous in childhood. The distribution and growing trends of overweight and obesity in children have been widely investigated, unlike the prevalence of too-low body weight and its determinants. This study aimed to estimate the frequency of body mass deficiency in Polish rural girls and differences among four Polish regions – Choszczno and Leszno in the north-west, and Ostrów Mazowiecka and Suwałki in the north-east. Data were taken from 7764 rural girls aged 9–18 years examined in 1987, when the country was in economic crisis, and 9431 such girls examined in 2001, when the country was undergoing political transformation. The frequency of weight deficiency was estimated based on BMI by applying the international standards of Cole. An Extent of Overweight (EOW) index was used to create an Extent of Thinness (EOT) index. A significant increase in weight deficiency was found in the rural girls – from 7.5% in 1987 to 8.9% in 2001 – and an increase in the EOT index from 0.37 in 1987 to 0.43 in 2001. Analysis by area of residence demonstrated significant differentiation. In the regions in north-west Poland, mainly inhabited by non-farming families, the prevalence of weight deficiency in girls almost doubled from 1987 to 2001, probably because of the mass and long-term unemployment that resulted from the closure of state farms in 1992. In contrast, in the north-east regions, the prevalence of weight deficiency remained almost unchanged over this period, with only a slight decrease, probably because the inhabitants were mainly farm and farm/working families with better living conditions. Despite the overall increase in thinness prevalence in rural girls in Poland, different living conditions have had different biological effects.

Nudging or ‘choice architecture’ refers to strategic changes in the environment that are anticipated to alter people’s behaviour in a predictable way, without forbidding any options or significantly changing their economic incentives. Nudging strategies may be used to promote healthy eating behaviour. However, to date, the scientific evidence has not been systematically reviewed to enable practitioners and policymakers to implement, or argue for the implementation of, specific measures to support nudging strategies. This systematic review investigated the effect of positional changes of food placement on food choice. In total, seven scientific databases were searched using relevant keywords to identify interventions that manipulated food position (proximity or order) to generate a change in food selection, sales or consumption, among normal-weight or overweight individuals across any age group. From 2576 identified articles, fifteen articles comprising eighteen studies met our inclusion criteria. This review has identified that manipulation of food product order or proximity can influence food choice. Such approaches offer promise in terms of impacting on consumer behaviour. However, there is a need for high-quality studies that quantify the magnitude of positional effects on food choice in conjunction with measuring the impact on food intake, particularly in the longer term. Future studies should use outcome measures such as change in grams of food consumed or energy intake to quantify the impact on dietary intake and potential impacts on nutrition-related health. Research is also needed to evaluate potential compensatory behaviours secondary to such interventions.

Background: Few studies examining the genetic architecture of cigarette smoking have focused on adolescents or examined developmental changes in additive genetic, shared environment, and unique environmental influences on liability to initiate cigarette smoking and quantity of cigarettes smoked. The aim of this study was to add to the literature on liability to initiate and use cigarettes during adolescence using a nationally representative sample. Method: Data for this study came from adolescent and young adult twin pairs (aged 14–33 years) from the National Longitudinal Study of Adolescent to Adult Health. We ran a series of developmental causal–contingent–common pathway models to examine whether additive genetic, shared, and unique environmental influences on liability to the initiation of cigarette use are shared with those on smoking quantity, and whether their contributions change across development. Results: We found evidence for a developmental shift in genetic and shared environmental contributions to cigarette use. Early in adolescence, genetic and environmental influences work independently on liability to cigarette smoking initiation and quantity of cigarettes smoked, but liability to these behaviors becomes correlated as individuals age into young adulthood. Conclusions: These findings provide insight into the causal processes underlying the liability to smoke cigarettes. With age, there is greater overlap in the genetic and environmental factors that influence the initiation of cigarette smoking and quantity of cigarettes smoked.

Otolith shape analyses were conducted on three different species of Mullidae (Mullus barbatus barbatus, M. b. ponticus and M. surmuletus). The otolith shape was described by 19 harmonics from elliptic Fourier descriptors. In a first step, their comparison through canonical discriminant analyses (CDA) was run for all fish with right otoliths, left otoliths and both otoliths pooled. The latter possibility had a higher discriminating power and allowed much more visually explicit results. This implied that the two otoliths were not similar as often claimed, and had each their specific information. In a second step, the CDA demonstrated strong spatial discrimination of local populations from various areas within the Mediterranean basin, i.e. NW Mediterranean, Aegean Sea and Black Sea, and between sites within each area. The percentage of well classified individuals of M. barbatus in predefined groups varied between 78 to 100% depending on sites, and even reached 100% for each site for M. surmuletus. These spatial patterns were most likely linked to differences in environmental conditions between areas and sites, such as effects of strong river runoffs and differences in depths and/or habitat types. In a third step, CDA also evidenced ontogenetic discriminations of mullet populations that could be linked (i) to influence of diet of fish of various sizes and (ii) to changes in physiological conditions according to the stage of development of the fish.

In this study, we explored relations among negative life events, negative attributional style, avoidant coping, and level of fear in 99 children who had survived residential fires. Overall, negative life events, negative attributional style, and avoidant coping were found to be predictive of levels of fear. However, the relation between negative life events and fear was moderated by mother's level of education such that this prediction was obtained only for those children whose mothers were low in education level. Age, ethnicity, and sex did not moderate these relations. In addition, negative attributional style and avoidant coping were related to levels of fear in those children whose mothers were high in education levels but not those whose mothers were low in education level. Results are discussed within a stress and coping framework.

The aim of the study was to examine long-term sequelae in the children of mothers who were depressed at 3 months postpartum. In a community sample from two general practices in South London, 149 women were given psychiatric interviews at 3 months postpartum and 132 of their children (89%) were tested at 11 years of age. The children of women who were depressed at 3 months postpartum had significantly lower IQ scores. They also had attentional problems and difficulties in mathematical reasoning, and were more likely than other children to have special educational needs. Boys were more severely affected than girls, with the sex difference most pronounced on Performance IQ. The links between postnatal depression and the children's intellectual problems were not mediated by parental IQ and were not accounted for by measures of social disadvantage nor by the mother's later mental health problems. Breastfeeding did not remove the effect of the mother's illness on Full Scale IQ, but exerted its own influence on Verbal IQ and appeared to mediate the link with mathematical ability. The findings show that adverse experiences in infancy predict cognitive ability and academic performance a decade later.

Data from two twin studies are examined to assess genetic and environmental influences on literacy, and the etiological relationship between language and literacy. Study 1 used children from 86 families previously recruited for a study of the genetics of specific language impairment (see Bishop, North, & Donlan, 1995), who completed tests of single-word reading and spelling. Literacy problems in this sample were common, were strongly heritable, and showed a close genetic relationship with poor nonword repetition. Study 2 included two subsets of children: 37 twin pairs who had taken part in study 1, 3 to 4 years earlier, and 100 twin pairs recruited from the general population by Bishop et al. (1999). All children were given a standardised test of nonword reading. There was no genetic influence on nonword reading ability, either across the normal range, or at the lower extreme, though there were significant associations with some social variables. However, bivariate DeFries–Fulker analysis suggested that in this study, as in study 1, there was shared genetic variance between poor nonword repetition and literacy deficits. It is concluded that poor nonword repetition, which is known to be highly heritable, puts the child at risk for literacy problems. However, in a general population sample, such as that included in study 2, poor nonword repetition is a relatively rare correlate of literacy problems, which are more likely to have an environmental origin. Thus the different pattern of results in the two studies can be explained if one assumes that genetic influences are substantial only when literacy problems are severe and/or accompanied by oral language difficulties.

Fears and phobias are relatively common in childhood. Both environmental and genetic theories have tried to explain the etiology behind these conditions. However, data supporting the different theories are sparse. To investigate the relative importance of genetic and environmental influences on specific phobias and fears, parental reports of animal, situational, and mutilation fears and phobias were completed for 1106 pairs of 8- to 9-year-old Swedish twins. The prevalence of specific phobias was 7.3% for boys and 10.0% for girls. Genetic, shared environmental, and nonshared environmental effects contributed to individual differences in fears and phobias in young children, but the magnitude of the effects differed between sexes. Shared environmental effects contributed to a general susceptibility for fearfulness. Genetic and nonshared environmental effects, on the other hand, contributed both to the general susceptibility and specific fearfulness, even though these effects primarily were fear specific. These results indicate that both heritable factors as well as environmental factors such as trauma, vicarious learning, and/or negative information are important for differences in fearfulness and phobias—at least in children.

Previous research has shown that children receiving substitute parental care tend to have high rates of emotional/behavioural disturbance, but uncertainty remains on the extent to which this derives from genetic risk, adverse experiences before receiving substitute care, or from risks associated with substitute care experiences. In order to examine the effects of institutional rearing (as a specific form of substitute care), two groups of primary school children reared in substitute care from before the age of 12 months were compared: 19 children in residential group (institutional) care and 19 in continuous stable foster family care (matched for age and gender). The two groups were similar in coming from biological families with high rates of psychopathology and social malfunctioning, but differed with respect to pattern of rearing. Both groups were compared with classroom controls, using teacher questionnaires, systematic classroom observations, and standardised cognitive testing. Parental questionnaires were also obtained for the two substitute care groups. As found previously, the combined substitute care groups differed from controls in showing a high level of hyperactivity/inattention. The observational measures showed a similar effect, indicating that the elevated rate was not attributable to rater bias. The teacher questionnaire and observational measures showed, however, that the increased level of hyperactivity/inattention was substantially higher in the institutional group than the foster family group. Parental questionnaire ratings showed the same contrast between the groups, except that the main difference was on unsociability and emotional disturbance rather than hyperactivity/inattention. It is concluded that, against a background of genetic and early environmental risk, institutional rearing predisposes to a pattern of hyperactivity/inattention.

Thirty hyperactive and 30 non-hyperactive children were confronted with a delay, consisting of a waiting situation of 15 minutes, either with or without extra stimulation provided by the presentation of a videotape. The behaviour of the child during the waiting period was videotaped and later coded by two naive observers. In line with theories that emphasise the stimulation-seeking function of hyperactive behaviours, such as the optimal stimulation account and the delay aversion theory, a group by stimulation effect was hypothesised. For two categories of activity this was found, with ADHD children displaying more activity than non-ADHD children in the no-stimulation but not in the stimulation condition. These data provide support for the stimulation-seeking function of certain features of ADHD hyperactivity.

This review of children's language learning considers historical accounts of acquisition and individual variation, recent advances in methods for studying language learning, research on genetic and environmental input that have contributed to the interactionist perspective, and the relevance of cross-disciplinary work on language disorders and the biology of learning to future theories. It concludes that the study of children's language development is converging on an interactionist perspective of how children learn to talk, incorporating the contributions of both nature and nurture to emergent, functional language systems. Language learning is viewed as an integration of learning in multiple domains.

The aim of this longitudinal sibling adoption study was to estimate genetic and environmental components of variance in parent- and child-reported measures of the family environment (parental negative affect, negative control, and achievement orientation). Participants included 85 adoptive and 106 nonadoptive sibling pairs from the Colorado Adoption Project. Parents and children completed annual assessments of the family environment when the children were 10, 11, and 12 years old, and genetic and environmental parameter estimates were derived. Genetic influences were found for parent-reported negativity and warmth and child-reported achievement orientation, suggesting child genetic effects on these measures of the family environment. Shared environmental influences were found for parent-reported negativity, inconsistent discipline, warmth, and child-reported positivity. Nonshared environmental variance was substantial for children's ratings, but modest for parents' ratings.