Magazine article Newsweek

Shyness, Sadness, Curiosity, Joy: Is It Nature or Nurture?

Magazine article Newsweek

Shyness, Sadness, Curiosity, Joy: Is It Nature or Nurture?

Article excerpt

The wizards of genetics keep closing in on the biological roots of personality. It's not your imagination that one baby seems born cheerful and another morose. But that's not the complete picture. DNA is not destiny;, experience plays a powerful role, too.

IF ANY CHILD SEEMED DESTINED TO GROW UP afraid of her shadow and just about anything else that moved, it was 2-year-old Marjorie. She was so painfully shy that she wouldn't talk to or look at a stranger. She was even afraid of friendly cats and dogs. When Jerome Kagan, a Harvard professor who discovered that shyness has a strong genetic component, sent a clown to play with Marjorie, she ran to her mother. "It was as if a cobra entered that room;' Kagan says. His diagnosis: Marjorie showed every sign of inherited shyness, a condition in which the brain somehow sends out messages to avoid new experiences. But as Kagan continued to examine her over the years, Marjorie's temperament changed. When she started school, she gained confidence from ballet classes and her good grades, and she began to make friends. Her parents even coaxed her into taking horseback-riding lessons. Marjorie may have been born shy, but she has grown into a bubbly second grader.

For Marjorie, then, biology--more specifically, her genetic inheritance-- was not her destiny. And therein lies our tale. In the last few years scientists have identified genes that appear to predict all sorts of emotional behavior, from happiness to aggressiveness to risk-taking. The age-old question of whether nature or nurture determines temperament seems finally to have been decided in favor of Mother Nature and her ever-deepening gene pool. But the answer may not be so simple after all. Scientists are beginning to discover that genetics and environment work together to determine personality as intricately as Astaire and Rogers danced. "If either Fred or Ginger moves too fast, they both stumble," says Stanley Greenspan, a pediatric psychiatrist at George Washington University and the author of "The Growth of the Mind." "Nature affects nurture affects nature and back and forth. Each step influences the next." Many scientists now believe that some experiences ,:an actually alter the structure of the brain. An aggressive toddler, under the tight circumstances, can essentially be rewired to channel his energy more constructively. Marjorie can overcome her shyness--forever. No child need be held captive to her genetic blueprint. The implications for child rearing--and social policy- are profound.

While Gregor Mendel's pea plants did wonders to explain how humans inherit blue eyes or a bald spot, they turn out to be an inferior model for analyzing something as complex as the brain. The human body contains about 100,000 genes, of which 50,000 to 70,000 are involved in brain function. Genes control the brain's neurotransmitters and receptors, which deliver and accept mental messages like so many cars headed for their assigned parking spaces. But there are billions of roads to each parking lot, and those paths are highly susceptible to environmental factors. In his book "The New View of Self," Dr. Larry Siever, a psychiatry professor at Mount Sinai Medical Center, writes about how the trauma of the Holocaust caused such intense gene fir: scrambling in some survivors that their children inherited the same stress-related abnormalities. "Perhaps the sense of danger and uncertainty associated with living through such a time is passed on in the family milieu and primes the biological systems of the children as well," says Siever. He added that that might explain why pianist David Helfgott, the subject of the movie "Shine," had his mental breakdown.

A gene is only a probability for a given trait, not a guarantee. For that trait to be expressed, a gene often must be "turned on" by an outside force before it does its job. High levels of stress apparently activate a variety of genes, including those suspected of being involved in fear, shyness and some mental illnesses. …

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