This article updates an article published in the RoundTable on Jan. 7, 2009. It focuses on the importance of early childhood experiences in forming the architecture of the brain, and primarily relies on five reports issued by the National Scientific Council on the Developing Child (NSCDC), one of which was issued jointly with the National Forum on Early Childhood Program Evaluation (NFECPE).1-5 NSCDC is a multidisciplinary, multi-university collaboration designed to bring the science of early childhood and early brain development to bear on public decision-making. Both NSCDC and NFECPE are based at the Center on the Developing Child at Harvard University.
Continuing scientific research demonstrates that early childhood experiences leave chemical signatures on genes that affect how easily the genes are turned “on” or “off.” In this way, early childhood experiences combine with genes and the environment to physically shape the architecture of a child’s brain.
These early experiences – whether nurturing toward positive growth or stressful to the point of being toxic – have “an enormous impact” on how the brain’s lower-level neural networks are connected or “wired” together and become the building blocks for more advanced circuits.2
Positive experiences establish a strong foundation for more effective learning capacities in the future. Negative experiences, depending on their timing, duration and severity, can produce physiological disruptions that lead to lifelong problems in learning, behavior, and health.5
Scientists and researchers are thus putting increased emphasis on the need to ensure that all children have positive early childhood experiences. The NSCDC says in strong terms: “The need to address significant inequalities in opportunity, beginning in the earliest years of life, is both a fundamental moral responsibility and a critical investment in our nation’s social and economic future.”1
Shaping the Brain
The brain is composed of billions of highly integrated sets of neural circuits (i.e., connections among brain cells) that are “wired” under the interactive influences of genes, the environment, and experience.1
The prenatal environment, “can have a profound influence on [the brain’s] architecture.” After birth, a child’s experiences play “an increasingly important role in shaping the architecture of developing neural circuits so that they can function optimally for each individual child.”3
Genes provide the “initial plan for the brain’s architecture.”3 The 23,000 genes that children inherit from their parents form the “structural genome.” Scientists liken the structural genome to the hardware of a computer – each requires an operating system to tell it what to do. In the genome, that operating system is called the “epigenome.” Like software for a computer, the epigenome determines which functions the genetic “hardware” does and does not perform.4
The epigenome is built over time. Positive experiences, such as exposure to rich learning opportunities, leave a “chemical signature” written on the top of a gene that result in healthy systems, such as effective learning and memory. Negative influences, such as environmental toxins or stressful life circumstances, leave a chemical “signature” on top of a gene that can lead to the development of unhealthy systems, such as setting a stress response system activation too high or too low.4
These chemical signatures can be temporary or permanent, and both types affect how easily the genes are switched “on” or “off,” and thereby significantly influence how brains and bodies develop. “The epigenome is the chemical signature that explains how early life experiences become embedded in the circuitry of the developing brain and are associated with lifelong experiences,” says NSCDC.4
NSCDC says the field of epigenetics is relatively new and on the cutting edge of biological sciences. To date, scientists have found that most chemical signatures left on genes are temporary. They have found, however, that certain experiences can cause “enduring epigenetic modifications” in hundreds of genes that have already been identified, and the list is growing. NSCDC says, “[T]hese latter genes appear to play particularly key roles in brain and behavioral development,” says NSCDC.4
Early Experiences Can Have Far-reaching Effects
Brain development has “sensitive periods” – periods in which certain neural circuits are very receptive and grow dramatically. Different neural circuits pass through sensitive periods at different ages, and they mature at different ages. The sensitive period for neural circuits that perform low-level analyses of sensory stimuli tend to end before or soon after birth. The sensitive periods for higher-level circuits such as language and speech ends later; and the circuits for higher cognitive functions end later still. Neural circuits, particularly those that are specialized for learning, continue to adapt their architecture throughout the adult years.
Different kinds of experiences are critical at different ages for optimal brain development. Different types of experiences are essential to develop low-level neural circuits than to develop high-level circuits.
By age three, a great deal of brain architecture is developed. But vast regions of the brain that are responsible for higher order functions – including most cognitive, social, and emotional capacities – have not yet begun to mature or are at very early stages of maturation. Thus, for most functions the window of opportunity remains open well beyond the age of three. This appears, though, to be subject to one important caveat. NSCDC says, “More complex brain circuits build upon earlier, simpler circuits.”3
The earlier circuits, developed through very early experiences, provide the foundation for more advanced neural circuits. If the lower-level circuits are not wired properly, it becomes more difficult to build the higher-level circuits, according to NSCDC. “Building more advanced cognitive, social and emotional skills on a weak initial foundation of brain architecture is far more difficult and less effective than getting things right the first time.”3
“Just as a faulty foundation has far-reaching detrimental effects on the strength and quality of a house, adverse early experience can have far-reaching effects on the development of brain architecture,” says NSCDC.3
NSCDC says, “The implications for later interventions in development are clear – the task will be harder, more expensive in terms of societal and individual effort, and potentially less extensive and desireable.”
In addition, scientists are finding that certain early childhood experiences can cause enduring epigenetic modifications in hundreds of genes that appear to play particularly key roles in brain and behavioral development. “As we get older, new experiences can continue to change our epigenome. However, science tells us that the chemical signatures imprinted on our genes during fetal and infancy development can have significant influences on brain architecture that last a lifetime.”4
Responsive Environments Build Sturdy Brain Circuits
Research shows that an environment that is nurturing, responsive and language-rich fosters healthy development. This can be found in the home, in a childcare center, or even in a casual local program.
In its most recent report, the NSCDC says, “Beginning after birth, a strong foundation for human well-being requires responsive environments and supportive relationships to build sturdy brain circuits, facilitate emerging capabilities, and strengthen the roots of physical and mental health.”5
A “major ingredient” of a responsive relationship is what NSCDC calls “serve and return” interactions between a child and adults. “Beginning shortly after birth, the typical ‘serve and return’ interactions that occur between young children and the adults who care for them actually affect the formation of neural connections and the circuitry of the developing brain. Over the next few months, as babies reach out for greater engagement through cooing, crying and facial expressions – these reciprocal and dynamic exchanges literally shape the architecture of the developing brain.”5
As children get older, more sophisticated “serve and return” interactions with a child, reading on a regular basis to a child and exposing a child to more cognitive language have positive impacts. The stimulation that occurs in the brain through these activities “can result in epigenetic changes that establish a foundation for more effective learning capacities in the future.”4
While a language-rich, responsive home promotes healthy development, NSCDC cautions against pushing too fast. “When adults or communities expect young children to master skills for which the necessary brain circuits have not yet been formed, they waste time and resources, and may even impair healthy brain development by inducing excessive stress in the child,” says NSCDC.3
“For the vast majority of kids in normal homes, all they will need in order to develop strong brain architecture is the kind of rich experience they will get from everyday interactions,” said developmental psychologist William Greenough, a member of the NSCDC. “But if the parents don’t provide this experience, the children can’t make up for it on their own.”6
Negative Influences Disrupt Brain Development
Adverse early experiences can have far-reaching detrimental effects on the developing architecture of a child’s brain and provide a weak foundation for all future learning, behavior and health, according to NSCDC.3
A child who is malnourished or lacks critical nutrients, or who is exposed to toxins, such as alcohol, cocaine or lead, or who is exposed to toxic stressors such as recurrent child abuse or neglect, severe maternal depression, parental substance abuse, or family violence can suffer adverse effects. These early experiences “can have adverse effects on developing brain architecture, which weakens the foundation upon which future learning, behavior, and health are built,” say the NSCDC and NFECPE.2
Moreover, some of these experiences, such as malnutrition, exposure to chemical toxins, and toxic stress that occur before birth or in early childhood “are not forgotten,” says NSCDC. Rather, they “are built into the architecture of the developing brain through the epigenome,” and can have long-lasting effects.4
Significantly, NSCDC has also found in its most recent report that a significant absence of basic “serve and return” interactions between a child and adults can disrupt the developing brain. Occasional inattention in an otherwise responsive environment is normal and can be growth promoting under caring conditions. Concerns arise when there is “chronic” or “severe” deprivation of responsive care.5
A “chronic” deprivation of responsive care can lead to toxic stress and disrupt and weaken the developing brain architecture, says NSCDC. Over time, it “can lead to academic struggles, difficulties in social adjustment, mental health problems, and even chronic physical disease.”5
“Common examples of such [chronic] under-stimulation,” says NSCDC, “include few daily interactions that provide opportunities for young children to engage in active conversation with adult caregivers or frequent periods in which infants or toddlers are left in front of a television for hours at a time.” This can be caused as result of limited understanding of the developmental needs of young children. It may also be caused by the stresses of poverty, a distracting family illness, and a range of other factors.5
“Chronic” under-stimulation, however, may be addressed effectively by providing effective parenting education or by providing high-quality child care or early education programs, says NSCDC.5
NSCDC defines “severe” under-stimulation as a “significant, ongoing absence of serve and return interaction, often associated with failure to provide for basic needs.” It can “produce serious physiological disruptions that lead to lifelong problems in learning, behavior, and health,” and may result in a higher rate of “more academic problems and special education referrals.”5
The interventions needed to address “severe” deprivations of responsive care are much more complex than those needed to address “chronic” deprivations. “Children’s recovery rates are influenced by the severity, duration and timing of the deprivation as well as by the timing and type of the intervention that is provided.”5
“Neglectful acts or patterns occur in every culture, at all income levels, and within all racial, ethnic, and religious groups,” says NSCDC.5 NSCDC also says, “Greater societal benefits would also be realized if we moved beyond a narrow focus on children whose parents are struggling with significant social and economic hardship and directed more attention to the threat of neglect in families across the spectrum, such as circumstances where parents are overwhelmed by chronic psychological or medical conditions.”5
Implications for Early Childhood Policies
Scientific research on brain development underscores that it is vitally important to ensure that pregnant women receive high quality medical care and that all children have supportive and nurturing experiences starting at birth. A continuing theme of the NSCDC is: “It is more effective and more efficient to get things right the first time than to try to fix them later.”3
Some of the NSCDC’s many suggestions include:
• Assure access to appropriate, affordable, high-quality medical and nutrition services to pregnant women, infants and toddlers.
• Increase the availability of high quality childcare programs that begin immediately after birth to enhance the experiences of young children in families with limited education and low income.
• Educate parents on how to provide a strong responsive and supportive environment for their children, filled with early literacy experiences.
• Provide developmental assessments and intervention services for young children experiencing significant adversity before they exhibit problems in their behavior or development.
• Enroll all children who have sensory or cognitive disabilities in early intervention programs as early as possible.
NSCDC and NFECPE’s joint report says it is not only a fundamental moral responsibility to address significant inequities in opportunity as early in a child’s life as possible, but it pays off to do so in economic terms. Successful programs have generated benefit-cost ratios ranging from a $2 benefit for every $1 spent, to a $17 benefit for every $1 spent, depending on the program. The report cautions, however, “Programs that cost less because they employ less-skilled staff are a waste of money if they do not have the expertise needed to produce measurable results.”2 In addition, interventions “that are poorly planned or implemented have generated few to no beneficial effect.”2
1. “The Science of Early Childhood Development” ( 2007), prepared by the National Scientific Council on the Developing Child (“NSCDC”).
2. “A Science-Based Framework for Early Childhood Policy” (2007), prepared by the NSCDC and the National Forum on Early Childhood Program Evaluation (“NFECPE”).
3. “The Timing and Quality of Early Experiences Combine to Shape Brain Architecture” ( 2008), prepared by NSCDC.
4. “Early Experiences Can Alter Gene Expression and Affect Long-Term Development” (2010), prepared by NSCDC.
5. “The Science of Neglect: The Persistent Absence of Responsive Care Disrupts the Developing Brain” (2012), and the accompanying Brief.
6. “Rich Experiences, Physical Activity Create Healthy Brains” (2006), by William Greenough.
7. NSCDC, Science Briefs: The Effects of Early Reading with Parents on Developing Literacy Skills (2007).
8. “The Effects of Vocabulary Intervention on Young Children’s Word Learning: A Meta-Analysis” (2010), by Loren M. Marulis and Susan B. Neuman.