the quality of children’s peer relations during childhood predicted their health and adjustment in adolescence and adulthood. A new wave of prospective longitudinal studies largely substantiated this premise. Childhood peer rejection, victimization, and friendlessness forecasted a variety of later‐life social difficulties and dysfunctions (Ladd, 2005).
Peer relations research eventually broadened to incorporate diverse ethnic and cultural contexts. Within North America, for example, researchers discovered that whereas Euro‐American children had more cross‐ethnic friendships than African‐American children (Kawabata & Crick, 2008), African‐American children had a larger number of friendships and more opposite‐sex friendships (Kovacs et al., 1996). Internationally, research on bullying that had originated in Norway spread to many other nations. Additionally, cross‐national comparisons were made of children’s friendships, peer group relations, social behavior, and interpersonal competencies (Chen et al. 2018).
Childcare and schooling contexts
Cultural and economic changes made childcare and formal schooling foci for social development research. A primary aim for childcare research, as detailed later, was to elucidate the impact of early nonparental care on young children’s socioemotional development. Another investigative thrust centered on the evaluation of compensatory programs for economically disadvantaged preschoolers. Programs such as Head Start, which were designed to prepare children for school, eventually expanded their objectives to include social as well as pre‐academic competencies (Raver & Zigler, 1997).
With older children, researchers endeavored to elucidate the social features and consequences of formal schooling (Wentzel, 2015). Inquiry was wide‐ranging and included factors such as school structure and organization (e.g., size, gender groupings, school transitions, race/ethnic composition), instructional environments and methods (e.g., open vs. traditional classrooms, didactic vs. peer‐mediated learning), and classroom interpersonal dynamics (e.g., classmate and teacher–child relations). Among other discoveries, researchers found that smaller schools facilitated children’s engagement in extracurricular activities which, in turn, predicted favorable student outcomes (Schaefer et al., 2011). School transitions, in contrast, were associated with unfavorable student outcomes, such as stress, declining self‐esteem, and disengagement (Eccles & Roeser, 2003). Research on classroom instruction and dynamics revealed, among other findings, that peer‐mediated learning improved children’s collaborative and interpersonal relations with classmates (Roseth et al., 2006; Tolmie et al., 2010).
Research on after‐school arrangements for school‐age children arose in response to the growth of dual‐earner families. Studies of self‐care (i.e., allowing children to look after themselves after school) often documented hazards and risks (e.g., stress, drug use, antisocial behavior; Lord & Mahoney, 2007). In contrast, children were found to benefit from structured, adult‐supervised after‐school programs (Vandell et al., 2005).
Media
Media, in all of its rapidly expanding forms, received substantial investigative attention. Early research focused on televised violence and its effects on children’s aggressive behavior. Corroboration of this effect and the pervasiveness of violence in media aimed at children (Wilson et al., 2002) spurred additional lines of investigation. Included were studies designed to explicate violent television’s role in fostering hostile attitudes and aggressive, violent, and delinquent behavior (Bushman & Huesmann, 2012). Researchers also examined media’s effects on children’s social relations, perceptions, and emotional sensitivity. Findings indicated that media use not only limited children’s participation in real‐life peer relations (e.g., friendships) and social activities (Pea et al., 2012), but it also distorted their perceptions of the social world. Illustrations included results showing that children, after viewing episodes of interpersonal conflict, developed negative expectations toward unknown peers (i.e., perceived hypothetical classmates as unfriendly; Mares et al., 2012). Additionally, evidence suggested (although see Ferguson, 2007) that violent media and video games desensitized children to violence, reduced their emotional responsiveness, and fostered stereotypes (Bushman & Huesmann, 2012).
It also became evident that media need not be harmful and in fact, could facilitate children’s social development. Research on educational and public‐service television revealed that, depending on its form and content, media could not only discourage antisocial behavior but also increase altruism. Investigators discovered, for example, that children who watched Sesame Street and Mister Rogers – TV programs rich in sociomoral and prosocial content – were more likely to learn and apply prosocial behaviors in real‐life interactions (Mares & Woodward, 2001).
The introduction of the internet (i.e., social media) and its rapid adoption by youth prompted research on its use and impact (Livingstone & Haddon, 2009). Both benefits and risks were identified. For example, whereas evidence showed that children utilized these platforms to meet and maintain friendships (Wolak et al., 2002), it also revealed that internet usage made them vulnerable to cyberbullying and abuse by predators (Ybarra et al., 2006).
Aim 2: Delineate the biological foundations, mechanisms, and processes that launch, regulate, and shape the course of social development
Theory and research on the biological foundations of human development has grown exponentially over the past few decades. Particularly noteworthy are advances in human genetics, neurological and brain development, and child temperament.
Genetics
The discipline of behavioral genetics emerged during the 1960s and one of its aims was to estimate the heritability of human characteristics or behaviors. Because the human genotype could not be studied directly, genetic influence was investigated indirectly using adoption and twin studies and findings substantiated the heritability of many social characteristics (e.g., temperament, personality, aggression; Rutter, 2006).
As subsequently detailed, theoretical and investigative innovations enabled researchers to address more challenging questions (e.g., How do genetic and environmental influences combine to influence behavior? Scarr & McCartney, 1983; Rutter, 2006), but also generated controversies about the relative importance of genetic versus environmental influences. One such debate revolved around the contention that parental genes made a stronger contribution to children’s development than parenting behavior (Harris, 1995; Vandell, 2000).
As direct approaches to studying genes emerged, disciplines such as genomics and molecular genetics were formed. Innovations such as DNA sequencing techniques and the mapping of the human genome (Collins et al., 2003) made it possible to examine the association between specific genes and phenotypical social attributes.
The likelihood that multiple rather than single genes underlie observable characteristics, and the near‐infinite number of combinations thereof, complicated research on the genetic bases of social characteristics. Nonetheless, evidence began to reveal how specific genes, in combination with particular rearing conditions, were linked with children’s social development. In one such study (Caspi et al., 2002), it was discovered that the effects of parental maltreatment were moderated by children’s genetic susceptibility to that particular stressor. Children with low‐activity MAOA (monoamine oxidase A: a gene that breaks down stress‐linked neurotransmitters) tended to develop higher levels of antisocial behavior than those with high‐activity MAOA. Other findings showed that children who possessed a gene configuration linked to self‐regulation difficulties (i.e., chromosome 7 gene with short 5‐HTTPR) and experienced low‐quality parenting were more likely to develop externalizing problems (Davies & Cicchetti, 2014).
Neurological
