StartingSmartHow EarlyExperiences AffectBrain Development

S

Second Edition

THEOUNCE OFPREVENTIONFUND

Starting SmartHow Early Experiences Affect Brain Development

Michael Stevens is a healthy, beautiful newborn baby. As his

parents admire him, they wonder, "What will Michael be like

when he grows up? Will he do well in school? Will he get along

with other kids and be happy?" Scientists now believe that the

answers to these questions depend in large part on how young

Michaels brain develops, and that this development in turn depends

largely on the nutritional, medical, emotional, and intellectual support

his parents, extended family, and community provide for him during

his childhood.

Recent advances in brain research have provided great insight into how the brain,

the most immature of all organs at birth, continues to grow and develop after birth.

Whereas this growth had been thought to be determined primarily by genetics, scientists now

believe that it is also highly dependent upon the childs experiences. Research shows that, like protein, fat,

and vitamins, interactions with other people and objects are vital nutrients for the growing and developing brain,

and different experiences can cause the brain to develop in different ways. It is this "plasticity" of the brain, its

ability to develop and change in response to the demands of the environment, that will enable Michael to learn

how to use computers as successfully as his ancestors learned how to hunt animals in the wild.

As he grows, Michaels ability to understand language, solve problems, and get along with other people will be

influenced by what he experiences as an infant and young child. This is not to say that individual genetic differences

have no influence on how a child develops; they do. But there is mounting evidence that experiences affect the way

genes are expressed (i.e., turned on and off) in the developing brain. While good early experiences help the brain to

develop well, experiences of neglect and abuse can literally cause some genetically normal children to become

mentally retarded or to develop serious emotional difficulties.

StartingSmart

Understanding How the Brain Develops

To understand how this happens, we need to understand a bit about how the brain works. The brain is comprised of many regions that perform specific functions, such as identifying what we see, processing spokenlanguage, or assessing whether we are in danger. Within each of these brain areas are millions of neurons, ornerve cells, which send messages to each other across synapses. These trillions of nerves and synapses and thepathways they form make up the "wiring" of the brain; they allow all of the various areas to communicate andfunction together in a coordinated way. The number and organization of connections in the brain influenceeverything from the ability to recognize letters of the alphabet to facility at managing complex social relationships.

In most regions of the brain, no new neurons are formed after birth. Instead, brain development consists of anongoing process of wiring and re-wiring the connections among neurons. New synapses between cells are con-stantly being formed, while others are broken or pruned away. This happens throughout life. However, in earlychildhood the brain is genetically programmed to produce more synapses than it will ultimately use. Indeed, by8 months of age a baby may have an astounding 1,000 trillion synapses in his brain! This blooming of synapseshappens at different times in different areas of the brain. Development then proceeds by keeping the synapsesthat are used and pruning away those that arent. The pruning of synapses happens over the childhood years asthe different areas of the brain develop(Huttenlocher & Dabholkar, 1997).

Pruning allows the brain to keep the connections that have a purpose, while eliminating those that arent doinganything. In short, pruning increases the efficiency with which the brain can do what it needs to do. But, becausethe brain operates on the "use it or lose it" rule, an "over-pruning" of these connections can occur when a childis deprived of normally expected experiences in the early years. This leaves the child struggling to do whatwould have come more naturally otherwise.

Some areas of the brain, such as those which help us see clearly, become less "plastic" or changeable when thepruning is over. This has led to tremendous concern about providing what the brain needs to prune and organ-ize itself correctly before the "windows of opportunity" close. For example, surgeons now remove congenitalcataracts as early in infancy as possible, because they know that if they wait until the child is older, the neuralconnections between his eyes and his brain will fail to develop properly, and he will never be able to see. Brainscientists are also working diligently to unlock the secrets of how the brain turns on and off its ability to changeitself. There is real hope that if we can understand the ways this happens, we can create therapies, both thosethat use drugs and those that use carefully structured experiences and training exercises, that can open up windows and re-wire brains that were deprived of normally expected experiences early in life or those that getdamaged later in life.

StartingSmart

The Power of Early Experiences

Our brains shape and reshape themselves in ways that depend on what we use them for throughout our lives.Learning language is a nice example of how experiences contribute to each persons unique pattern of braindevelopment. The ability to speak and to understand others speech requires only the minimal opportunity tocommunicate that almost all children experience. However, which language a child learns to speak depends on the language he experiences, and his brain will adapt to this specific language. When an infant is 3 monthsold, his brain can distinguish several hundred different spoken sounds, many more than are present in hisnative language. Over the next several months, however, his brain will organize itself more efficiently so that it only recognizes those spoken sounds that are part of the language that he regularly hears. For example, a one-year-old Japanese baby will not recognize that "la" is different from "ra," because the former sound is neverused in his language. During early childhood, the brain retains the ability to re-learn sounds it has discarded, so young children typically learn new languages easily and without an accent. After about age 10, however, plasticity for this function is greatly diminished; therefore, most people find it difficult to learn to speak a foreign language as well as a native speaker if they only begin to learn it in adolescence or adulthood.

More importantly, early experiences can determine how proficient a child becomes in his or her native language.Researchers found that when mothers frequently spoke to their infants, their children learned almost 300 morewords by age 2 than did their peers whose mothers rarely spoke to them (Huttenlocher et al., 1991; also, Hart& Risley, 1995). Furthermore, studies have suggested that mere exposure to language such as listening to thetelevision or to adults talking amongst themselves provides little benefit. Rather infants need to interact directlywith other human beings, to hear people talking about what they are seeing and experiencing, in order for themto develop optimal language skills. Unfortunately, many parents are under the mistaken impression that talkingto babies is not very important because they are too young to understand what is being said.

A new consensus is emerging about the importance of intervening with families of disadvantaged children in thefirst months and years of life to ensure they provide the kinds of experiences that support optimal development.Psychologists have long known that children of poorly educated, low-income parents often dont reach the sameintellectual levels as children of well-educated, wealthy parents. The recent developments in brain research haveprovided new insights into why this is so. Parents who are preoccupied with a daily struggle to ensure that theirchildren have enough to eat and are safe from harm may not have the resources, information, or time they needto provide the stimulating experiences that foster optimal brain development. Infants and children who arerarely spoken to, who are exposed to few toys, and who have little opportunity to explore and experiment withtheir environment may fail to fully develop the neural connections and pathways that facilitate later learning.Despite their normal genetic endowment, these children are at a significant intellectual disadvantage and arelikely to require costly special education or other remedial services when they enter school. Fortunately, inter-vention programs that start working with children and their families at birth or even prenatally can help preventthis tragic loss of potential (see box below).

Intervention Can Help Kids Who Are at RiskThrough the University of North Carolinas "Abecedarian Project," Craig Ramey and his colleagues demonstrated thatintensive early intervention could greatly enhance the development of children whose mothers have low income and education levels. The children in the project were randomly assigned to receive either an intensive 5-year program of full-day, full-year child care and parent involvement activities beginning in the first few months after the childs birth, or to receive only free formula and diapers. After just 3 years, dramatic results were evident: the program children had anaverage IQ score of 105, while the control group children averaged only 85. And unlike many