|Neuroscience offers a wealth of research on the human brain and how children learn. The question is: Will educators put their faith in it?|
A baby is born with more than 100 billion brain cells, more than he or she will ever use in a lifetime. Some of these brain cells, called neurons, have already been hard-wired to other cells. They control the baby's heartbeat, command its breathing, produce reflexes, and regulate other functions essential to survival.
But the rest are just waiting to be hooked up and played like orchestra instruments in a complex musical composition. Parents, educators, the baby's early experiences--all these factors will determine which neurons connect and which connections will eventually wither and die from lack of use.
The circuits that form essentially decide who we are. They can influence whether a child becomes shy or outgoing, musically talented or tone-deaf, silver-tongued or tongue-tied. Chances are a child bathed in language from birth will learn to speak quickly. A baby whose coos are met with smiles, rather than impassivity, will likely become emotionally responsive.
Over the past 20 years or more, neuroscientists have amassed a wealth of knowledge on the brain and its development from birth to adulthood. And they are beginning to draw some solid conclusions about how the human brain grows and how babies acquire language, sight and musical talents, and other abilities.
The question now is: How much of these data can educators use? The answer is uncertain. Some findings hint at definite directions for education. Others, stemming primarily from animal studies, are tentative at best.
"If you tell
decisionmakers or parents, 'Your child will have a better brain if
you do this or that,' then that seems to have a more seductive
appeal than anything we educators can say."
But a few points are clear. One is that the brain matters. Helping parents nurture healthy brains in their children will lead to a payoff in school later on. That means that babies, while still in the womb, should receive proper nutrition and protection from the harmful effects of drugs, alcohol, and cigarette smoke. After birth, it means immersing children in environments that are emotionally and intellectually rich and stimulating.
The second point is that neuroscience, with its reputation as a "hard science," could be a potential ally for educators. Educators for years have claimed that the early years of childhood were critical to learning. But their own studies, coming from a body of scientific work perceived as "soft" and lacking in the kinds of graphic evidence that come from brain scans and biological studies, have sometimes fallen on deaf ears.
"If you tell decisionmakers or parents, 'Your child will have a better brain if you do this or that,' then that seems to have a more seductive appeal than anything we educators can say," says Edward Zigler, the director of the Bush Center in Child Development and Family Policy at Yale University.
The connections neurons make with one another are called synapses. While various parts of the brain develop at different rates, study after study has shown that the peak production period for synapses is from birth to the later elementary school years.
During that time, the receptive branches of the nerve cells, or dendrites, are growing and reaching out to form trillions upon trillions of synapses. The brain's weight triples to nearly adult size. What's more, periods of rapid synapse production in specific parts of the brain seem to correspond to the development of behaviors linked to those parts of the brain.
But at almost the same time the brain is linking up cells, it also begins pruning off or fine-tuning connections. "We know the brain in other species, as well as in man, goes through a period when it makes too many connections," says Harry Chugani, a neuroscientist at Children's Hospital and Wayne State University in Detroit. The synapses that are not repeatedly used die off while others remain. "The child who learns piano will learn those connections and, 20 years later, will learn to play again easier than someone who has not studied it," says Chugani, whose studies have looked specifically at glucose production in the developing brain.
The brain uses glucose at each cell connection as a source of energy. By age 4, Chugani found, a child's brain uses more than twice the glucose that an adult brain uses. Between ages 4 and 10, the amount of glucose a child's brain uses remains relatively stable. But at age 10, glucose utilization begins to drop off until it reaches adult rates at age 16 or 17.
Chugani's findings suggest that a child's peak learning years occur just as all those synapses are forming. Yet, in practice, students rarely study foreign language, complex mathematics, or music until their later elementary years. And the most intense periods of instruction often do not come until college.
"In Japan, they play in college, don't they?" Chugani asks, noting how the rigorous pace of instruction for Japanese students drops off once they enter a college or university. "It's almost as if they understand that."
|Nature may open doors for developments that slowly begin to close as the years go by.|
None of these findings is to suggest that people cannot learn later on in life. The findings do indicate, however, the possibility that critical periods exist for some skills. In other words, nature may open doors for development that slowly begin to close as the years go by. Chugani's work puts the key years at age 0 to 10. But other neuroscientists, such as Yale University's Patricia Goldman-Rakic, believe the critical period may be even shorter.
Some of the most compelling experiments in early brain development have focused on vision. Scientists have known for years that babies afflicted with cataracts in the first two years of life will never have perfect vision once the cataracts have been surgically removed. Similarly, Torsten Wiesel and David Hubel, in a 1970s experiment, found that sewing shut one eye of a newborn kitten rendered it blind--even after the eye was reopened. The reason: Too few neurons had connected from the closed eye to the visual cortex.
The same idea may also bear on learning in other areas, such as language. Patricia K. Kuhl, a researcher at the University of Washington in Seattle, has shown in a series of recent studies that infants are drawn to speech sounds common to their native language even before they speak.
Kuhl studied 6-month-old babies in the United States and Sweden. Each infant sat on a parent's lap while a nearby loudspeaker continuously repeated a speech sound, such as "ee." If the sound changed from the original, the infants were taught to look at the speaker where an animated toy would pop out.
Once the infants had learned this trick, Kuhl and her colleagues tested them to gauge their sensitivity to sounds in their native tongue vs. sounds peculiar to a foreign tongue. For example, the "ee" sound common in English is not found in Swedish. The Swedish "y," on the other hand, is absent from English. Sure enough, both American and Swedish babies turned their heads more for the sounds from the foreign language. That is, American babies could distinguish small acoustic differences in Swedish sounds but could not hear the same small differences for English. Swedish infants turned more often to the English sounds. So, by age 6 months, babies from both cultures were behaving in a "language specific" way.
Yet, other studies suggest that even younger babies--newborns--are still "language generalists" in that they distinguish between sounds of all languages. What happens in the intervening months?
"We started looking at caretakers," Kuhl says. The researchers noticed that caretakers, in addressing infants, tended to speak more slowly, to stretch out sounds, and to use higher pitch voices and curvy intonations. Aided by this most natural form of instruction, she says, babies over time develop a "perceptual magnet" for familiar sounds. In other words, by 6 months, the babies' brains may have already hard-wired particular pathways for their native language. That's why adult speakers of Japanese, for example, pronounce an English word such as "lake" as "rake." In their native language, they hear "l" in the same sound cluster as "r."
"I'm not so sure I believe there is an absolute critical period for language learning," Kuhl concludes, "but I believe it's difficult learning a second language past a certain point, and that is due to this interference effect" that comes once the language "magnets" are firmly in place.
Does this mean parents should hang Berlitz tapes from their children's cribs? No, Kuhl says. But it does suggest that second languages should be taught as early as preschool and that children with otitis media, a chronic inflammation of the middle ear that hampers hearing in young children, may develop speech problems later on.
In music, too, researchers have used magnetic-resonance imaging to examine the cortex, or the outer "bark," of the brain. Each sense has its own relay station in the cortex. They found, for example, that the earlier a string musician had begun playing an instrument, the greater the amount of cortex dedicated to controlling the finger movements needed to play that instrument.
And psychiatrists have long known that babies whose parents fail to appropriately mirror or reward their emotional responses sometimes lose the ability to display a full repertoire of emotions. Even at 3 months of age, infants of depressed mothers mirror their mothers' moods while playing with them.
Of course, nature's doors of opportunity are not completely inflexible. The brain is noted for its plasticity--its ability to adapt and change. And studies have shown that new synapses form over a lifetime with exposure to new experiences.
But there is little question among brain researchers that early experience, education, and environment play a primary role in determining who we are. That notion runs counter to several long-entrenched views of learning, says Frank Newman, the president of the Education Commission of the States, which held a conference on neuroscience and education in July with support from the Charles A. Dana Foundation. "It is widely assumed, for example, that most of us are born on a bell curve," he says, referring to the 1995 book asserting that intelligence is fixed at birth.
Brain studies, on the other hand, suggest the opposite. They indicate that parents and educators have a golden opportunity to mold a child's brain. And that calls for a full-court press during the early years--that is, a rich child-care environment without undue academic stress.
Psychologists like Zigler have advocated for such a push for a long time. And education researchers have offered their own statistical ammunition in that struggle. Among the strongest of those efforts is a 20-year study by Craig T. Ramey, a researcher with the Civitan International Research Center in Birmingham, Ala.
|Children with preschool experiences had significantly higher IQs throughout elementary school.|
Beginning in the 1970s, Ramey and his colleagues provided social services and five years of preschool to groups of black and disadvantaged children. Compared with similar groups of children who received no such services, or who only received special help later on in elementary school, the children with preschool experiences had significantly higher IQs throughout elementary school. Moreover, the gains they made lasted at least through age 15--the last time researchers tested the children.
Yet, says Zigler, policymakers have largely ignored such evidence. "We know rotten environments hurt kids, yet we don't have a problem putting millions of kids in rotten day care every day," he says. "One implication of all this is that mothers ought to be home at least several months after a child's birth--if not a whole year. But in the United States, we have only 12 weeks unpaid leave, and young families can't afford to take unpaid leave."
At the least, says Zigler, neuroscience offers additional--and somewhat more glamorous--evidence strengthening educators' case.
But critics are quick to caution against a hasty marriage between the two disparate fields. "There's a misunderstanding that if science discovers a fact it is irrational, immoral, or unintelligent not to use that fact in schools," says Jerome Kagan, a Harvard University psychologist. "But schools are a creation of the populace. For example, he says, it's probably true that boys are biologically better prepared to do mathematics than girls or that men make better fighter pilots than women.
"Does that mean we should have separate classes for girls or prevent women from becoming fighter pilots?" Kagan asks. "Of course not. Society has every right to say, 'Yes, that's an interesting fact, yet my values tell me to ignore that fact."
Kagan, for one, is wary of resurrecting the centuries-old notion that a child's entire future is determined in the first year of life. "For learning to read, write, or do arithmetic, yes, children vary," he says. "But it is a mistake to assume if you have the right experiences the first year, you will be prepared, or, if not, you will not be prepared." Certain Guatemalan tribes, for example, sometimes raise their infants in isolation to protect them from "the evil eye." Yet, those children still develop language.
Ever the cautious researchers, some neuroscientists also worry that educators will jump on findings before they have been conclusively proved. In the 1980s, for example, some educators, psychologists, and entrepreneurs extended research findings from neuroscience to suggest that either the left or right hemisphere of an individual's brain would be dominant. Left-brainers were thought to be highly verbal, sequential learners who preferred logical and analytic thinking. Right-brain learners, on the other hand, were thought to have difficulty expressing themselves verbally but excellent spatial memories and highly developed recall abilities, among other characteristics. Consequently, curricula were developed to appeal to one or the other learning style.
But, say Renate Nummela Caine and Geoffrey Caine in Making Connections: Teaching and the Human Brain, the original studies that gave rise to the theory involved severing the corpus callosum, the band of nerve fibers that connects both brain hemispheres, to provide relief from epileptic seizures. That procedure prevents the two halves of the brain from communicating. But normal brain activity, on the other hand, involves interaction between both sides of the brain.
"The most accurate statement that we can make at this point is that research on hemisphericity is inconclusive," they write.
Early childhood is not the only developmental period for which neuroscience can inform educators. Studies have shown, for example, that stress and constant fear--at any age--can circumvent the brain's normal circuits.
Joseph LeDoux at the Center for Neuroscience at New York University was among the first to show that the amygdala, the part of the brain that controls fear, rage, or other strong emotions, can perceive things that trigger those emotions before the rational, thinking part of the brain does. What's more, this almond-shaped cluster perched just above the brain stem can actually command the body into action. It can, in the words of Daniel Goleman, the author of the best-selling book Emotional Intelligence, essentially "hijack" the rest of the brain.
The more this pathway is used, the easier it is to trigger--a notion that may help explain why battered or abused children find it difficult to learn. Verbal or visual cues that remind them of their experiences may be constantly shifting their amygdalas into gear, getting in the way of more rational thinking.
|Researchers found that people were better at recalling stories or slides that had aroused strong feelings in them than those that were devoid of emotional context.|
But emotion may also serve to enhance memory. Larry Cahill, James McGaugh, and their colleagues at the Center for Neurobiology, Learning, and Memory at the University of California-Irvine, have found that people were better at recalling stories or slides that had aroused strong feelings in them than those that were devoid of emotional context.
In another experiment, the two researchers also discovered they could improve memory in laboratory rats by injecting them with Adrenalin. Administering beta blockers, on the other hand, to inhibit the effect of the Adrenalin, tended to erase memory improvements.
"I think this is something that ought to be used in the classroom all the time," McGaugh says. "Teachers should present information in an exciting way. We shouldn't act as though there is a difference between cognition and emotion.
"Good teachers," he adds, "already do this."
Whether educators will begin to take more cues from neuroscience remains to be seen. The Dana Foundation, which co-sponsored the July conference on education and neuroscience, has launched a small grant program designed to encourage partnerships between the two fields. In the meantime, McGaugh suggests that teachers should look to the field in the same way astronomers once looked to the National Aeronautics and Space Administration. They should ask: "Here's what we want to know; how can you help us?"
Some Neuroscience Terminology
amygdala: An almond-shaped cluster just above the brain stem that triggers emotions.
axon: A slender fiber--along which impulses travel--branching out from the cell body to the dendrites of other neurons. Most neurons have only one axon.
cell body: The part of the neuron where information is received and stored.
cerebral cortex: The "bark" of the brain. It is the layer of gray matter that covers the cerebrum. Each of the five senses has its own relay station and its own area of the cortex.
dendrite: The short, branching extensions of a nerve cell that receive stimuli from other cells. It is one of three parts that make up the neuron. The other parts are the cell body and the axon.
neuron: One of the impulse-conducting cells that make up the brain, spinal cord, and nerves. Humans are born with more than 100 billion neurons, most of which are yet to be connected to one another.
plasticity: The brain's ability to change and adapt over time.
synapse: The connection formed between one neuron and another through which message impulses travel. Scientists believe the stimulation that babies and young children receive determines which synapses form in the brain--that is, which pathways become "hard wired." Anindividual brain cell may be connected to 10,000 or more other cells.