Vol. 10, No. 1, 2004 Page 2


The human brain is the most fantastic thing on earth. Nothing could do what the human brain does, yet somehow the brain does it—and keeps getting better at it. During six million years of human development, the brain has continued to enlarge and to become more complex.

Our understanding of the brain is growing as well, although far too slowly. (Only near the end of the last century did the U.S. Department of Health and Welfare decide to declare a "Decade of the Brain.") The Human Genome Project, increasingly sophisticated scanning techniques, and other advances are allowing a greater understanding of how the brain functions and—even more important—how it can malfunction.

One of the most complex features of the brain is its control of behavior, and research in this area is demonstrating that many of our long-held ideas about behavior are incorrect. Not many decades ago, even scientists thought the newborn brain was a "blank slate," and that all behavior, good and bad, was learned. Research now shows conclusively that this idea was wrong. Today researchers estimate that around fifty percent of behavior is genetically acquired, and thus attributable to "nature." Even a trait such as poor logic, which can lead to bad behavior, may be transmitted genetically, possibly by preventing the brain's neurons from connecting normally.

In retrospect, it is surprising that both science and society have been so slow to recognize that if people can genetically acquire hair and eye color, a predisposition to diabetes, and so much more, we can also inherit different behaviors—just as dogs and horses inherit different behavioral tendencies. It is equally remarkable that it has taken us so long to understand that when a malfunctioning brain is inherited, bad behavior can be the result.

The 'nurture' factor

It doesn't take much calculation to determine that if "nature" is responsible for 50 percent of behavior, "nurture" has to be responsible for the other half. Because society thinks of nurturing as pertaining to home conditions, and especially parenting, billions of dollars are spent by governments in an effort to improve troubled children's home environments.

These billions, however, are failing to help. Why? Judith Rich Harris in her book, The Nature Assumption, presents a strong argument that neither home conditions nor parenting have any effect on the development of a child's personality and behavior. Harris shows, step by step, how past research on the subject was flawed due to errors of correlation, and errors in confusing cause with effect. (For example, researchers often attributed children's behavior problems to parental discipline styles, failing to note that those disciplinary styles frequently evolved in response to children's aberrant behavior.) Indeed, Harris cites evidence showing that peers have a greater influence on a child's behavior than parents do.

The effect of both parents and peers on behavior, however, is dwarfed by another form of "nurture:" a child's biophysical environment. For example, malnutrition, smoking, or alcohol use by the mother during gestation can adversely affect the brain of a fetus in ways that alter the child's behavior forever. So can birth trauma, postnatal malnutrition, or exposure to environmental contaminants. Moreover, research shows that many children are particularly vulnerable to these insults, due to their genetic makeup.

It is critical that we recognize the crucial role that genes, often coupled with biological insults, play in determining behavior. Parents, including parents of adopted children, need to realize that if their children have "gone bad," it may be the result of an innate genetic vulnerability or physical insult rather than psychological trauma. And governments need to realize that a far greater share of the funds targeted at reducing crime and violence should be spent on finding ways to help the genetically vulnerable children who are most at risk for dangerous brain dysfunction.

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