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Early Childhood: The Nature of Early Experiences

Professor James Heckman of the University of Chicago, a Nobel prize-winner in economics known for his work on statistics and labour economics, has been involved in research on early childhood[1] with a number of scientists including neurobiologist Professor Eric Knudsen of Stanford University, whose laboratory studies of neural mechanisms of learning and attention use the barn owl as a model system. Other collaborators include Professors Judy L. Cameron (University ofPittsburgh) and Jack P. Shonkoff (HarvardUniversity).

Knudsen and colleagues assert that the uniquely powerful nature of early experiences is central to the principles which unify the economic, developmental psychology and neurobiology perspectives on early environment. Skill development and brain maturation are hierarchical processes in which higher level functions depend on, and build on, lower level functions. The capacity for change in skill development and neural circuitry is highest early in life and decreases over time. Early experiences influence cognitive and social skills and brain maturation.

“Language is an example of a cognitive skill that is acquired readily in early life but that requires great effort and is never learned as thoroughly as an adult. The dependence of language learning on age holds for first languages and second languages and for spoken languages and sign languages. For most people, a thorough command of language is attained when learning occurs before 7 years of age.  For language, as for many cognitive skills, early learning begets later learning. In the first stage of language learning, young children learn to discriminate among acoustically similar sounds (phonemes) that convey different meaning. This learning is critical to the next stage of language acquisition, which is to learn to segment phonemes into words. Sound segmentation is critical, in turn, to attaching meaning to words and finally to deriving meaning from grammar and syntax.”

In drawing on research on animals other than humans, Knudsen and colleagues noted that monkeys which lack close nurturing relationship with the primary caregiver – usually the mother – early in life respond aberrantly to social signals in later life and do not integrate well into social groups. The representation of cues in the auditory space map of owls is individually customized through experience. Manipulations of experience that alter auditory orienting behaviour also alter the functional properties of neurons in this circuit. The magnitude of the changes induced by experience is greatly influenced by the age of the owl. And in kittens, changes in the visual cortex which take place if vision in one eye is restricted during the sensitive period of early life become resistant to change and persist into adult life. Early learning establishes brain architecture which affects functional plasticity in adulthood.

Early experiences have a uniquely powerful influence on the development of cognitive and social skills and on brain architecture and neurochemistry: both skill development and brain maturation are hierarchical processes in which higher level functions depend on, and build on, lower level functions, and the capacity for change in the foundations of human skill development and neural circuitry is highest earlier in life and decreases over time. [2]

An environment of relationships – healthy development

A number of James Heckman’s colleagues are members of the National Scientific Council on the Developing Child at Harvard University. The Council was established in 2003 as a multi-disciplinary collaboration of scientists and scholars from universities across the United States and Canada designed to bring the science of early childhood and early brain development to bear on public policy decision-making. The Council is based at Harvard University. The Council strongly advocates investment in improving quality of life of disadvantaged children during the early childhood years. Research of the kind reported by Knudsen, Heckman and colleagues constitutes the basis of the Council’s policies. The Council emphasises that failure to so invest in early life makes cognitive development in later life more difficult and more expensive. The health of the mother during pregnancy and involvement of the mother in early years of the child’s life is critical!

The Council on the Developing Child at Harvard University, in their first ‘working paper’ stated, “Healthy development depends on the quality and reliability of a young child’s relationships with the important people in his or her life, both within and outside the family. Even the development of a child’s brain architecture depends on the establishment of these relationships.”[3]

“Young children experience their world as an environment of relationships, and these relationships affect virtually all aspects of their development – intellectual, social, emotional, physical, behavioral, and moral. The quality and stability of a child’s human relationships in the early years lay the foundation for a wide range of later developmental outcomes that really matter – self-confidence and sound mental health, motivation to learn, achievement in school and later in life, the ability to control aggressive impulses and resolve conflicts in nonviolent ways, knowing the difference between right and wrong, having the capacity to develop and sustain casual friendships and intimate relationships, and ultimately to be a successful parent oneself.

“Stated simply, relationships are the “active ingredients” of the environment’s influence on healthy human development.” Emphasising that scientific fact must be differentiated from popularly accepted fiction the Council points out that relationships are important throughout a child’s life. “Young children can benefit significantly from secure relationships with other nurturing and reliable adults whom they trust, while their attachments to their parents remain primary and central.” However, “there is no scientific evidence to support the belief that frequently rotating relationships with large numbers of adult caregivers provide valuable learning opportunities in the early years of life… prolonged separations from familiar caregivers and repeated “detaching” and “re-attaching” to people who matter is emotionally distressing and can lead to enduring problems.”

“The importance of ensuring that relationships in child care are nurturing, stimulating, and reliable leads to an emphasis on the skills and personal attributes of the caregivers, and on improving the wages and benefits that affect staff turnover.  School readiness must include the capacity to form and sustain positive relationships with other children and adults and the social and emotional skills for cooperating with others. Childhood education must strive to involve young children in reciprocal learning interactions with teachers and peers and it should capitalize on children’s natural interests and intrinsic drive to learn, rather than follow an adult-determined agenda: young children learn best in an interactive, relational mode rather than through an education model that focuses on rote instruction.”

A summary of recent research posted on the Council’s website points out “New scientific research shows that environmental influences can actually affect whether and how genes are expressed. Thus, the old ideas that genes are “set in stone” or that they alone determine development have been disproven. In fact, scientists have discovered that early experiences can determine how genes are turned on and off and even whether some are expressed at all. Therefore, the experiences children have early in life—and the environments in which they have them—shape their developing brain architecture and strongly affect whether they grow up to be healthy, productive members of society.”[4]

The fundamental point made in the studies by Knudsen and colleagues and pointed out strongly by the Council on the Developing Child at Harvard University is the extremely important relationship of mother and child in the earliest months of life. In this context a finding by the Centers for Disease Control and Prevention in the United States concerning breast feeding in the first year of life by American mothers is very interesting.[5] “Breast-feeding practices vary widely across race and ethnicity. More than 80 percent of Hispanics and Asians begin breast-feeding, but only 74 percent of whites and 54 percent of non-Hispanic blacks do so. The higher the education level of the mother, the more likely she is to breast-feed… There were sharp geographical differences as well: in 13 states, most in the Southeast, the differences between blacks and whites were more than 20 percent.”

Of further interest is this: “Because breast-feeding confers a large number of benefits to mother and child, the Department of Health and Human Services views a high prevalence of breast-feeding as an important public health goal. The study published online on April 5, 2010 in the journal Pediatrics concluded that if 90 percent of mothers breast-fed exclusively for at least six months, the United States would save $13 billion in medical costs and prevent 911 deaths every year.” (Keep in mind that a major ‘education gap’ in the U.S. is between African Americans and other groups!)

Studies in the UK using data from the UK also show benefits of breastfeeding in terms of improved cognitive development of the child and fewer behavioural problems.[6] Maria Quigley of the National Perinatal Epidemiology Unit at Oxford University who conducted the research with colleagues from the University of Essex, University College London and the University of York pointed out that “that observation might not have been the direct result of breastfeeding – it could have been down to a number of factors. As a group, mothers who breastfed for four months were very different socially to those who formula fed. They were more likely to be older, better educated and in a higher socio-economic position, on average. Having controlled for these and other differences between the groups, we found there was still a 30% lower risk of behaviour problems associated with prolonged breastfeeding.”

Whilst in human society the majority of successful early childhood interventions start in the preschool years, socioeconomic gradients in cognitive skills, socio-emotional functioning and health can be observed by age three. Therefore, preventative programmes starting earlier in childhood may be even more effective.[7] Knudsen and colleagues conclude that building America’s workforce requires attention to these kinds of findings (see below).


Evidence from studies of neurophysiology, psychology, anthropology and the natural sciences provide compelling and important evidence about early childhood in humans. The most recent research by psychologist Elliot Tucker-Drob of the University of Texas demonstrates dramatically from studies of twins that socioeconomic differences reflected in the home environment are evident in children’s ability even at 10 months.[8] For children of higher socioeconomic background later development in the stimulating environment which more likely typifies their home means the parents’ activities matters less than for less well-off young children. Preschool is an essential first step in every child reaching their potential: it closes the gap for children of poorer backgrounds. Trying to overcome the performance gap at school costs more and achieves less.

Jonah Lehrer writing in the online magazine Wired about Tucker-Drob’s research observes, “Tucker-Drob used a national sample of 1,200 identical and fraternal twins born to 600 families of various incomes and ethnicities across the United States in 2001. Because he was comparing identical twins, who share 100 percent of their genes, and fraternal twins, who share 50 percent, he was able to calculate the relative genetic and environmental influences on achievement at age five, both for those kids who had been enrolled in preschool and those who went without.

“His main finding might, at first glance, seem somewhat paradoxical. According to the twin data, family environmental factors — the nurture side of the equation — accounted for about 70 percent of the variance in test scores for children who did not attend preschool. In contrast, those same family factors only accounted for about 45 percent of variance among children who attended preschool.”

A study by Tucker-Drob reported earlier, also mentioned by Lehrer, found “In children from poorer households, the decisions of parents still mattered. In fact … the home environment accounted for approximately 80 percent of the individual variance in mental ability among poor 2-year-olds. The effect of genetics was negligible.

The opposite pattern appeared in 2-year-olds from wealthy households. For these kids, genetics primarily determined performance, accounting for 50 percent of all variation in mental ability. For parents, then, the correlation appears to be clear: As wealth increases, the choices of adults play a much smaller role in determining the mental ability of their children.”



[1] Eric I. Knudsen, James J. Heckman et al, ‘Economic, neurobiological and behavioral perspectives on building America’s future workforce’,  Proceedings of the National Academy of Sciences  103(27), p10155–10162, July 5, 2006

[2] Eric I. Knudsen, James J. Heckman, Judy L. Cameron, and Jack P. Shonkoff, ‘Economic, neurobiological, and behavioral perspectives on building America’s future workforce’, World Economics, 7(3), July-September, 2006.

[3] National Scientific Council on the Developing Child, Young Children Develop in an Environment of Relationships. (2004). Working Paper No. 1.

[4] Early Experiences Can Alter Gene Expression and Affect Long-Term Development’: Working Paper #10

[5] Reported by Nicholas Bakalar, ‘Despite Advice, Many Fail to Breast-Feed’, New York Times April 19, 2010.

[6] M A Quigley et al, Breastfeeding is associated with improved child cognitive development: evidence from the UK Millennium Cohort Study Community Health 63 (8), 9 September 2009 ; ‘Prolonged breastfeeding may be linked to fewer behaviour problems’, University of Oxford Science | Health 10 May 11; the data does not include mothers from non-white or mixed-ethnic backgrounds.

[7] Orla Doyle et al, ‘Investing in early human development: Timing and economic efficiency’, Economics and human biology. Jan-Feb 2009.

[8] Jonah Lehrer, ‘ Does Preschool Matter?’, Wired March 5, 2012