Child Development

Abstract

Child development is a type of human development: the course of biological, cognitive, language and social change from birth through childhood. This article names the classic cognitive-developmental works of Piaget and Vygotsky and covers the contexts in which children develop, the maturation of the cortex, executive functions and self-control, the development of theory of mind, early language learning, attachment, adverse childhood experiences and resilience, early deprivation and intervention, and the global scale of children at risk of not reaching their developmental potential. A recurring question is how much early experience shapes later outcomes, and how far later experience can change them.

Keywords: child development, early childhood, executive functions, theory of mind, adverse childhood experiences

One review concluded that research, programmes and policies on early childhood development have advanced substantially since 2000, with new neuroscientific evidence linking early adversity and nurturing care with brain development and function throughout the life course (Black et al., 2017). An ecological approach to development focuses on the progressive accommodation, throughout the life span, between the growing human organism and the changing environments in which it actually lives and grows (Bronfenbrenner, 1977).

What Child Development Is

Many children younger than 5 years in developing countries are exposed to multiple risks, including poverty, malnutrition, poor health and unstimulating home environments, which detrimentally affect their cognitive, motor and social-emotional development (Grantham-McGregor et al., 2007). Classic accounts of cognitive development include Piaget's study of the origins of intelligence in children (Piaget, 1952) and Vygotsky's account of the development of higher psychological processes in Mind in Society (Vygotsky, 1978). Piaget's theory long served as the field's overarching guide; one review argued that with its loss cognitive development had become disjointed, and that evolutionary theory is on its way to becoming a new metatheory for the field (Bjorklund, 2018). Vygotsky's theory has been synthesised around the zone of proximal development, treated in one analysis as an overarching concept that integrates the main tenets of his theory of human development and reflects the sociogenetic root of all human mental functioning (Eun, 2019). One account of skill formation holds that it is a dynamic process in which early inputs strongly affect the productivity of later inputs (Heckman, 2006).

Types of Child Development

MeSH places child development within human development, lists infant development as an entry term of the same descriptor, and files one narrower descriptor beneath it, language development.

This is a classification for indexing literature, not a partition of developmental processes: MeSH files only language development as a narrower descriptor, while brain, cognitive and social development in childhood are indexed under the broader term.

Contexts of Development

The environments in which children develop include not only the immediate settings containing the developing person but also the larger social contexts, both formal and informal, in which these settings are embedded (Bronfenbrenner, 1977). Socioeconomic status, usually quantified from family income, parental education and occupational status, is associated with a wide array of health, cognitive and socioemotional outcomes in children, with effects beginning prior to birth and continuing into adulthood, and a review described these effects as moderated by characteristics of the child and family and by external support systems (Bradley & Corwyn, 2002). Behavior-genetic work bears on how such associations are read: in a sample of 7-year-old twins, the proportions of IQ variance attributable to genes and environment varied nonlinearly with socioeconomic status, with models suggesting that in impoverished families 60% of the variance in IQ is accounted for by the shared environment and the contribution of genes is close to zero, and that in affluent families the result is almost exactly the reverse (Turkheimer et al., 2003). A later meta-analysis found clear support for moderately sized gene × SES effects in U.S. studies, but effects that were zero or reversed in studies from Western Europe and Australia (Tucker-Drob & Bates, 2016). Using the prevalence of early childhood stunting and the number of people living in absolute poverty as indicators of poor development, one analysis estimated that over 200 million children under 5 years were not fulfilling their developmental potential, most of them in south Asia and sub-Saharan Africa (Grantham-McGregor et al., 2007). New estimates a decade later, based on proxy measures of stunting and poverty, indicated that 250 million children (43%) younger than 5 years in low-income and middle-income countries are at risk of not reaching their developmental potential (Black et al., 2017).

Brain Development

In a study of thirteen healthy children scanned every 2 years for 8 to 10 years, time-lapse maps of cortical gray matter revealed that higher-order association cortices mature only after lower-order somatosensory and visual cortices, the functions of which they integrate, are developed, and that phylogenetically older brain areas mature earlier than newer ones (Gogtay et al., 2004). Across four separate longitudinal samples spanning ages 8 to 30 years, cortical grey matter volume was at its highest in childhood, decreasing steadily through the second decade, while cerebral white matter volume increased until mid-to-late adolescence (Mills et al., 2016).

Executive Functions and Self-Control

Executive functions make possible mentally playing with ideas, taking the time to think before acting, meeting novel, unanticipated challenges, resisting temptations and staying focused, and a review identified the core executive functions as inhibition, working memory and cognitive flexibility (Diamond, 2013). The same review concluded that executive functions are trainable and can be improved with practice, and that stress, lack of sleep, loneliness or lack of exercise each impair them (Diamond, 2013). A meta-analysis of 23 studies with 30 group comparisons, however, found that working memory training programs produced reliable short-term improvements in working memory skills but no convincing evidence of generalization to other skills, and concluded that such programs appear to produce short-term, specific training effects that do not generalize (Melby-Lervag & Hulme, 2013).

Following a cohort of 1,000 children from birth to the age of 32 years, one study found that childhood self-control predicts physical health, substance dependence, personal finances and criminal offending outcomes, following a gradient of self-control, and that these effects could be disentangled from intelligence and social class (Moffitt et al., 2011). In a second cohort of 500 sibling pairs, the sibling with lower self-control had poorer outcomes, despite shared family background (Moffitt et al., 2011). Executive functions are covered further under executive function.

Theory of Mind

In initial studies of theory of mind, older preschoolers consistently passed false-belief tasks whereas younger children systematically erred, while more recent studies found evidence of false-belief understanding in 3-year-olds or demonstrated conditions that improve children's performance (Wellman et al., 2001). A meta-analysis of 178 separate studies found that a model including age, country of origin and four task factors accounted for 55% of the variance in false-belief performance, and that preschoolers went from below-chance performance to above-chance performance even across various countries and task manipulations (Wellman et al., 2001). The authors concluded that the findings are inconsistent with early competence proposals that attribute developmental changes to task artifacts, and are consistent with accounts that propose genuine conceptual change in the preschool years (Wellman et al., 2001). A later study used a novel nonverbal task to examine whether 15-month-old infants predict an actor's behavior on the basis of her true or false belief about a toy's hiding place; the results were positive, and the authors took them to support the view that, from a young age, children appeal to mental states to explain the behavior of others (Onishi & Baillargeon, 2005). The authors argued that this interpretation calls into question the notion that preschoolers undergo a fundamental change from a nonrepresentational to a representational theory of mind (Onishi & Baillargeon, 2005), the view the earlier meta-analysis supported. A later preregistered large-scale attempt to replicate four influential anticipatory-looking implicit theory-of-mind tasks, a related family of nonverbal methods, reliably replicated only one, which was no longer replicated once confounds were removed, and concluded that findings from such paradigms seem less reliable and valid than previously assumed (Kulke et al., 2018). The topic is covered further under theory of mind.

Language

Infants learn language with remarkable speed, and data reviewed in one account show that infants use computational strategies to detect the statistical and prosodic patterns in language input, leading to the discovery of phonemes and words (Kuhl, 2004). The same review proposed that the brain's commitment to the statistical and prosodic patterns experienced early in life might help to explain why infants are better language learners than adults (Kuhl, 2004). In a study of 36 children aged 4 to 6 years from varied socioeconomic backgrounds, those who had experienced more conversational turns with adults, independently of socioeconomic status, IQ and adult-child utterances alone, exhibited greater left inferior frontal activation during story listening, which significantly explained the relation between language exposure and verbal skill (Romeo et al., 2018).

Attachment

The construct goes back to the first volume of Bowlby's Attachment and Loss (Bowlby, 1969); Ainsworth and colleagues' Patterns of Attachment, reissued as a classic edition (Ainsworth et al., 2014), presented the Strange Situation and the secure base concept in which later measures of attachment have their roots. A summary of a 30-year longitudinal study argued that understanding the role of attachment entails grasping the organizational nature of the attachment construct and embracing a non-linear transactional model (Sroufe, 2005). In that study, attachment history was related to the growth of self-reliance, the capacity for emotional regulation, and the emergence and course of social competence, and specific patterns of attachment had implications for both normal development and pathology (Sroufe, 2005). Meta-analyses of early attachment and children's social competence with peers, externalizing problems, internalizing symptoms and temperament were summarized as supporting attachment theory, though with caveats (Groh et al., 2017).

Adversity and Resilience

In a study of 9,508 adults who completed a questionnaire about seven categories of adverse childhood experiences, a graded relationship was found between the number of categories of childhood exposure and each of the adult health risk behaviors and diseases that were studied (Felitti et al., 1998). A later meta-analysis of 37 studies with 253,719 participants found that individuals with at least four adverse childhood experiences were at increased risk of all health outcomes compared with individuals with none, with associations ranging from weak or modest for physical inactivity, overweight or obesity and diabetes to strongest for problematic drug use and interpersonal and self-directed violence (Hughes et al., 2017). The same meta-analysis identified considerable heterogeneity between estimates for almost half of the outcomes (Hughes et al., 2017). A review of cumulative risk concluded that childhood exposure to multiple risk factors exceeds the adverse developmental impacts of singular exposures, while noting that the usual cumulative risk index designates risk arbitrarily, loses data on risk intensity and is additive (Evans et al., 2013). In two birth cohorts with adverse childhood experiences measured prospectively in childhood, higher scores were associated with greater risk of later health problems, but had poor accuracy in predicting an individual's risk, and the authors concluded that although such scores can forecast mean group differences in health, targeting interventions on the basis of screening is likely to be ineffective (Baldwin et al., 2021).

One review argued that the study of resilience in development has overturned many negative assumptions and deficit-focused models about children growing up under the threat of disadvantage and adversity (Masten, 2001). Converging findings suggest that resilience is common and that it usually arises from the normative functions of human adaptational systems, with the greatest threats to human development being those that compromise these protective systems (Masten, 2001). A critical appraisal of the construct noted that criticisms of resilience research have focused on ambiguities in definitions and central terminology, heterogeneity in the risks experienced and competence achieved by individuals viewed as resilient, instability of the phenomenon, and concerns about its usefulness as a theoretical construct (Luthar et al., 2000). Resilience is covered further under psychological resilience.

Early Deprivation and Intervention

In a randomized controlled trial, young children living in institutions were randomly assigned to continued institutional care or to placement in foster care, and their cognitive development was tracked through 54 months of age (Nelson et al., 2007). The cognitive outcome of children who remained in the institution was markedly below that of never-institutionalized children and children placed into foster care, the improvement was most marked for the youngest children placed in foster care, and the authors suggested a possible sensitive period in cognitive development (Nelson et al., 2007).

Worked Example

The two global estimates can be compared directly. The earlier analysis estimated over 200 million children under 5 years not fulfilling their developmental potential (Grantham-McGregor et al., 2007), and the later one 250 million (43%) at risk (Black et al., 2017). Taking 250 million as 43% of the population of children younger than 5 years in low-income and middle-income countries implies about 250 / 0.43 ≈ 581 million children in that population. The two estimates come from separate analyses, so their difference of about 50 million is not a measured change over time.

Discussion

The sources combine strong claims about early experience with evidence of change. Early inputs are said to strongly affect the productivity of later inputs (Heckman, 2006), and early institutional care was followed by markedly lower cognitive outcomes (Nelson et al., 2007); yet children moved to foster care improved (Nelson et al., 2007), executive functions can be improved with practice (Diamond, 2013), although trained working memory gains did not generalize to other skills in one meta-analysis (Melby-Lervag & Hulme, 2013), and one review suggested that resilience under adversity is common (Masten, 2001).

Current Directions

One review of early childhood development called for increased multisectoral coverage of quality programming that incorporates health, nutrition, security and safety, responsive caregiving and early learning (Black et al., 2017). A meta-analysis of adverse childhood experiences concluded that sustaining improvements in public health requires a shift in focus to include prevention of adverse childhood experiences, resilience building and service provision informed by adverse childhood experiences (Hughes et al., 2017).

Common Misconceptions

Children exposed to adversity are usually damaged for life.

Converging findings suggest that resilience is common and usually arises from the normative functions of human adaptational systems (Masten, 2001).

Executive functions are fixed.

A review concluded that executive functions are trainable and can be improved with practice (Diamond, 2013), although a meta-analysis found that working memory training produced short-term, specific effects that did not generalize to other skills (Melby-Lervag & Hulme, 2013).

The amount of speech children hear is all that matters for language.

One study's results suggest that conversational experience impacts neural language processing over and above socioeconomic status or the sheer quantity of words heard (Romeo et al., 2018).

Glossary

Adverse childhood experiences.

Harmful experiences occurring during childhood or adolescence, such as child maltreatment or exposure to domestic violence.

Association cortices.

Higher-order cortical regions that integrate the functions of lower-order somatosensory and visual cortices.

Attachment.

The construct, studied from infancy, whose history was related in one longitudinal study to self-reliance, emotional regulation and social competence.

Cognitive flexibility.

One of the core executive functions, alongside inhibition and working memory.

Conversational turns.

Exchanges between a child and an adult, measured in one study from home audio recordings.

Developmental potential.

The development a child could reach; the number of children younger than 5 years in low-income and middle-income countries at risk of not reaching it has been estimated from proxy measures of stunting and poverty.

Executive functions.

The functions that make possible mentally playing with ideas, thinking before acting, meeting novel challenges, resisting temptations and staying focused.

False-belief task.

A test of whether a child understands that another person can hold a belief that differs from reality.

Inhibition.

A core executive function covering response inhibition and interference control.

Resilience.

Positive development under the threat of disadvantage and adversity, described in one review as arising usually from ordinary adaptational systems.

Self-control.

In the cited cohort study, the childhood capacity whose gradient predicted later health, wealth and offending outcomes.

Sensitive period.

A window in development, suggested for cognitive development by the outcomes of early foster-care placement.

Theory of mind.

Understanding of mental states such as belief, assessed in children with false-belief tasks.

Working memory.

One of the core executive functions, alongside inhibition and cognitive flexibility.

Key Researchers

Urie Bronfenbrenner

(1917-2005). Psychologist at Cornell University; proposed an experimental ecology of human development focused on the accommodation between the developing person and the changing environments in which it lives. Wikidata - Wikipedia - Faculty Page

Adele Diamond

. Researcher at the University of British Columbia (Department of Psychiatry); reviewed the core executive functions and evidence that they can be improved with practice. ORCID - Wikipedia - Google Scholar - Faculty Page

Patricia K. Kuhl

. Scientist at the University of Washington (Institute for Learning & Brain Sciences); reviewed how infants detect statistical and prosodic patterns in language input. ORCID - Wikipedia - Google Scholar - Faculty Page

Ann S. Masten

. Psychologist at the University of Minnesota; argued that resilience in development is common and usually arises from ordinary adaptational processes. ORCID - Wikipedia

Terrie E. Moffitt

. Psychologist at Duke University; led the cohort study showing that a gradient of childhood self-control predicts adult health, wealth and public safety. ORCID - Wikidata - Wikipedia - Google Scholar - Faculty Page

Henry M. Wellman

. Psychologist at the University of Michigan; led the meta-analysis of theory-of-mind development across 178 false-belief studies. ORCID - Wikipedia

Frequently Asked Questions

How does the brain mature in childhood?

In one longitudinal imaging study, higher-order association cortices matured only after lower-order somatosensory and visual cortices, and phylogenetically older brain areas matured earlier than newer ones (Gogtay et al., 2004).

What are executive functions?

A review identified the core executive functions as inhibition, working memory and cognitive flexibility (Diamond, 2013).

When do children understand false beliefs?

A meta-analysis found that preschoolers went from below-chance to above-chance performance on false-belief tasks (Wellman et al., 2001); one nonverbal study reported sensitivity to false belief in 15-month-olds (Onishi & Baillargeon, 2005), but a systematic replication of related anticipatory-looking paradigms found them less reliable and valid than previously assumed (Kulke et al., 2018).

How do infants learn language?

One review reported that infants use computational strategies to detect the statistical and prosodic patterns in language input, leading to the discovery of phonemes and words (Kuhl, 2004).

Does childhood self-control predict adult outcomes?

In a cohort followed from birth to age 32 years, childhood self-control predicted physical health, substance dependence, personal finances and criminal offending outcomes (Moffitt et al., 2011).

What are adverse childhood experiences?

They are harmful experiences occurring during childhood or adolescence, such as child maltreatment or exposure to domestic violence, and individuals with at least four were at increased risk of all health outcomes studied in one meta-analysis (Hughes et al., 2017).

Is resilience rare?

One review concluded that resilience is common and usually arises from the normative functions of human adaptational systems (Masten, 2001).

Can children recover from early deprivation?

In a randomized trial, institutionalized children placed into foster care had better cognitive outcomes than those who remained, most markedly for the youngest children placed (Nelson et al., 2007).

References