Nature, nurture, and social development*

The nature and nurture of network evolution

Although the origin of the fat-tail characteristic of the degree distribution in complex networks has been extensively researched, the underlying cause of the degree distribution characteristic across the complete range of degrees remains obscure. Here, we propose an evolution model that incorporates only two factors: the node's weight, reflecting its innate attractiveness (nature), and the node's degree, reflecting the external influences (nurture). The proposed model provides a good fit for degree distributions and degree ratio distributions of numerous real-world networks and reproduces their evolution processes. Our results indicate that the nurture factor plays a dominant role in the evolution of social networks. In contrast, the nature factor plays a dominant role in the evolution of non-social networks, suggesting that whether nodes are people determines the dominant factor influencing the evolution of real-world networks.

Are Adolescents More Emotional? A Study of the Daily Emotions of Middle Class Indian Adolescents1

This study evaluates the hypothesis that adolescence is a time of greater emotionality, focusing on urban middle class Indian youth. A sample of 100 8th graders and their parents provided 13,674 reports on their experience when signalled at random times by alarm watches over one week. Consistent with the hypothesis, the adolescents reported significantly more negative states and extreme positive states than both their mothers and fathers. Further analyses indicated that the negative emotional states of adolescents were related to school stress and inversely related to family and peer variables. These factors may contribute to adolescent emotionality. Significant inverse correlations between rates of negative emotions and mental health indicated that frequent negative emotions among adolescents should not be dismissed as normative.

A Behavioural Genetic Perspective on Close Relationships

This paper examines how genetic, shared environment, and nonshared environment influence individual differences in close relationships. First, a brief explanation of behavioural genetic methods is given. Next, we review behavioural genetic studies of the close relationships in which people are typically involved (parent-child, sibling, friend, and spouse). Many of the studies reviewed indicate a modest to moderate role for genetic factors. This suggests that genetic make-up can affect the nature of close relationships. It also implies that genetic factors may be involved in the influence of close relationships on individual adaptation. Behavioural genetic research has begun to show that this is the case. Close relationships may be especially important sources of nonshared environment. Behavioural genetic research consistently shows that environmental factors that have a functional effect on psychological traits work to make siblings in the same family different from one another rather than similar. Attempts to pinpoint specific aspects of the nonshared environment are under way. Parent-child relationships have been systematically explored, and found not to play an important role in nonshared environment. This leaves open the possibility that extrafamilial relationships, in particular friendships, may be important contributors to the nonshared environment.

Attachment, Emergent Morality, and Aggression: Toward a Developmental Socioemotional Model of Antisocial Behaviour

Does attachment play a role in the development of moral reasoning and antisocial behaviour? In this contribution we discuss the role of attachment relationships in the development of early precursors of morality and antisocial behaviour, in particular compliance and aggression in infancy and in childhood. Findings are presented on the role of attachment representations in the development of morality, authoritarianism, and criminal behaviour in adolescence and young adulthood. For heuristic purposes, two socioemotional models of the development of mild and serious types of antisocial behaviour are proposed in which attachment is a prominent feature.

Gender and birth order as determinants of parental behaviour

This study analyses the effect of gender and birth order of fifty-eight 3-month-old first- and laterborn boys and girls on parental treatment. Presence of parents, maternal primary care, and maternal and paternal facial exchange with the baby were assessed during videotaped observation sessions equivalent to a full day. The data reveal a sound birth rank effect, indicating that firstborns are preferred over laterborns in several respects: presence of mothers, presence of fathers, and father’s face-to-face behaviour when the mother is also present. With respect to gender differences, mothers prefer their daughters in terms of presence and primary care. Fathers prefer their sons in terms of presence. Unexpectedly, fathers prefer their daughters in terms of face-to-face exchange. The social context of fathers’ and mothers’ joint presence reveals the only interaction effect between gender and birth order with the preference of firstborn boys. The findings are related to previous research results as well as evolutionary considerations about parental investment.

Psychological aspects of human cloning and genetic manipulation: the identity and uniqueness of human beings

Human cloning has become one of the most controversial debates about reproduction in Western civilization. Human cloning represents asexual reproduction, but the critics of human cloning argue that the result of cloning is not a new individual who is genetically unique. There is also awareness in the scientific community, including the medical community, that human cloning and the creation of clones are inevitable. Psychology and other social sciences, together with the natural sciences, will need to find ways to help the healthcare system, to be prepared to face the new challenges introduced by the techniques of human cloning. One of those challenges is to help the healthcare system to find specific standards of behaviour that could be used to help potential parents to interact properly with cloned babies or children created through genetic manipulation. In this paper, the concepts of personality, identity and uniqueness are discussed in relationship to the contribution of twin studies in these areas. The author argues that an individual created by human cloning techniques or any other type of genetic manipulation will not show the donor's characteristics to the extent of compromising uniqueness. Therefore, claims to such an effect are needlessly alarmist.

Examining Genetic and Environmental Effects on Social Aggression: A Study of 6-Year-Old Twins

Using a genetic design of 234 six-year-old twins, this study examined (a) the contribution of genes and environment to social versus physical aggression, and (b) whether the correlation between social and physical aggression can be explained by similar genetic or environmental factors or by a directional link between the phenotypes. For social aggression, substantial (shared and unique) environmental effects but only weak genetic effects were found. For physical aggression, significant effects of genes and unique environment were found. Bivariate modeling suggests that social and physical aggression share most of their underlying genes but only very few overlapping environmental factors. The correlation between the two phenotypes can also be explained by a directional effect from physical to social aggression.

Maternal sensitivity, infant attachment, and temperament in early childhood predict adjustment in middle childhood: the case of adopted children and their biologically unrelated parents

In a longitudinal study, internationally adopted children (N = 146) placed before 6 months of age were followed from infancy to age 7. Results showed that girls were better adjusted than boys, except in cognitive development, and that easy temperament was associated with higher levels of social, cognitive, and personality development and fewer behavior problems. Higher quality of child-mother relationships, in terms of attachment security and maternal sensitivity, uniquely predicted better social and cognitive development. The combination of attachment disorganization and difficult temperament predicted less optimal ego-control and lower levels of cognitive development. It is concluded that even in adopted children, who are not biologically related to their adoptive parents, early mother-infant interactions and attachment relationships predict later socioemotional and cognitive development, beyond infant temperament and gender.

Importance of nonshared environmental factors for childhood and adolescent psychopathology

OBJECTIVE

To briefly summarize behavioral genetic findings in relation to child and adolescent psychopathology, paying special attention to the environmental rather than genetic components of variation, and to describe recent research exploring specific nonshared environmental processes in the development of adolescent depression.

METHOD

Behavioral genetic studies of child and adolescent psychopathology were outlined, with special attention given to findings from the Nonshared Environment and Adolescent Development Project. This project was also used to explore maternal negativity as a "candidate" nonshared environmental influence for adolescent depression.

RESULTS

These studies indicate that the environmental factors influencing developmental psychopathology are primarily of the nonshared variety (with the notable exception of juvenile delinquency). In addition, consistent results have not yet emerged from assessments of adolescent depression. Finally, maternal negativity was identified as a specific nonshared environmental factor related to adolescent depression.

CONCLUSIONS

The environment as well as genetics is important to understanding childhood psychiatric disorders, and behavioral genetic designs provide the best evidence for this. Specifically, environments not shared by siblings are particularly salient. From a clinical standpoint, these considerations point to the importance of assessing the entire family rather than only the family member with the "problem."

The genetic basis of complex human behaviors

Quantitative genetic research has built a strong case for the importance of genetic factors in many complex behavioral disorders and dimensions in the domains of psychopathology, personality, and cognitive abilities. Quantitative genetics can also provide an empirical guide and a conceptual framework for the application of molecular genetics. The success of molecular genetics in elucidating the genetic basis of behavioral disorders has largely relied on a reductionistic one gene, one disorder (OGOD) approach in which a single gene is necessary and sufficient to develop a disorder. In contrast, a quantitative trait loci (QTL) approach involves the search for multiple genes, each of which is neither necessary nor sufficient for the development of a trait. The OGOD and QTL approaches have both advantages and disadvantages for identifying genes that affect complex human behaviors.