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 and brain development
The emergence of neuroscience as a discipline and ensuing innovations advanced knowledge about neurological and brain development during childhood. Research strategies progressed from static, circumscribed techniques, such as mapping individual neurons and electrically stimulating brain tissue (Penfield, 1961), to dynamic, encompassing modes of inquiry made possible by imaging tools such as fMRI (Functional Magnetic Resonance Imaging). These innovations, along with other scientific initiatives (e.g., the “Decade of the Brain”) furthered efforts to elucidate the interface between brain growth and children’s social development.
Research on prenatal and infant development strengthened the premise that neurological development underlies early‐emerging social abilities and, when compromised, contributes to social dysfunctions. Findings, for example, implied that infants are biologically prepared to attend and respond to caregivers and to participate in rudimentary forms of social interaction (Bornstein, 2013). In contrast, neurological impairments attributable to prenatal teratogens (e.g., cocaine, marijuana, alcohol) were linked with early‐emerging, and in some cases, lasting social and emotional difficulties (Behnke et al., 2013).
Studies of brain maturation revealed that, throughout childhood and adolescence, there were periods of rapid growth and pruning within specific brain regions (e.g., visual, motor, auditory, language centers) and progress toward hemispheric lateralization and connectedness. Growth of this type was found to be associated with improvements in infants’ and children’s social and emotional capacities, skills, and regulatory abilities (Nelson et al., 2006).
Neuroscientific findings also supported the conclusion that social experience is a necessary component of brain development. Evidence implied that, although the brain is wired to “expect” species‐wide forms of experience (i.e., experience‐expectant processes), it also is influenced by experiences that are unique to the individual (i.e., experience‐dependent processes; Shonkoff & Phillips, 2000). On this basis, it was argued that experience essentially “customizes” the child’s brain (e.g., builds, differentially strengthens, prunes neuronal networks). Support for this contention included evidence linking brain alterations with differences in children’s early experiences and rearing conditions (e.g., deprivation, isolation, abuse; Nelson et al., 2007).
Recent innovations include the construct of the “social brain” which was conceived to be a network of brain sites (Blakemore, 2008; Bornstein, 2013) that facilitated the processing and interpretation of social phenomena (e.g., recognizing faces, predicting another’s actions). It was postulated that this network, along with other brain regions, contained a “mirror” system of neurons that enabled children to empathize or “experience” the same emotions they observed in others. Imaging data provided considerable support for the existence of these networks and their hypothesized functions (Blakemore, 2008).
Temperament
Beginning in the 1950s, investigators such as Thomas and Chess (Thomas et al., 1968) utilized the construct of temperament to account for early‐emerging, stable individual differences in infants’ and children’s responses to their environments. Subsequent refinements to theory and research extended knowledge about the origins of temperament. Much of what was learned supported the hypothesis that temperament, although not impervious to environmental influences, has a genetic or neurological basis (Kagan, 2007).
Advances were made in the conceptualization of temperament, the specification of component dimensions, and the development of reliable assessments. Descriptive taxonomies (e.g., easy, difficult, slow‐to‐warm‐up) were replaced with theory‐driven models that attributed temperamental variations to specific emotional, cognitive, or behavioral processes (emotional reactivity to novel stimuli; Kagen & Snidman, 2007; effortful control, negative affectivity, extroversion‐surgency; Rothbart, 2007). Empirical work clarified how temperamental characteristics were related to other aspects of children’s social development, including their behavior, relationships, and adjustment (Rothbart 2007).
Aim 3: Explicate the nature and development of children’s internal social‐cognitive, psychological, and emotional processes
Another prominent objective was to expand knowledge about processes that transpire within the child, that is, nonobservables such as social‐cognitive, psychological, and emotional representations and processes. Largely, investigative efforts were focused on explicating theory (e.g., specifying mechanisms driving development), gathering evidence about developmental transformations (i.e., age or stage changes, growth patterns), and linking specific internal processes with other aspects of child development (e.g., behavior, health, dysfunction).
Self‐understanding
Priorities within this sphere were to further illuminate when children develop a sense of self (i.e., emergence of self‐recognition), how children revise their self‐construals with age and experience (i.e., development of self‐concept), and how children appraise their abilities and worth (i.e., self‐esteem). Findings suggested that self‐recognition emerges early (i.e., around age two) and becomes more reliable and less context‐dependent across early childhood (Miyazaki & Hiraki, 2006).
Constructivist perspectives dominated research on self‐concept and, for the most part, investigators examined stability and change children’s self‐construals using self‐descriptive tools and methodologies. Principal findings implied that children’s self‐theories become more complex and abstract as they are shaped by age‐, gender‐, and context‐related experiences (Harter, 2012).
Self‐esteem was investigated for scientific purposes