The immature brain

Biology and other people develop our moral judgment

By Daniel R. Weinberger

WASHINGTON -- Last week's shootings at Santana High School led quickly to now-familiar attempts to explain the seemingly unexplainable in terms of culture and circumstance: violent entertainment, a lack of accountability for deviant behavior, broken homes. While each of these issues may play some role in the tragedies of school shootings, to understand what goes wrong in the teenagers who fire the guns, you have to understand something about the biology of the teenage brain.

Andy Williams, the boy held in the Santana shootings, is 15. Many other school shooters have been about the same age or even younger. And the brain of a I5-year-old is not mature particularly in an area called the prefrontal cortex, which is critical to good judgment and the suppression of impulse.

The human brain has required many millenniums and many evolutionary stages to reach its current complex status. It enables us to do all kinds of amazing and uniquely human things: to unravel the human genome, to imagine the future, to fall in love. .

As part of its capacity for achievement, it must also be able to exercise control that stops maladaptive behavior. Everyone gets angry; everybody has felt a desire for vengeance. The capacity to control impulses that arise from these feelings is a function of the prefrontal cortex.

This is the part that distinguishes our brain most decisively from those of all other animals, even our closest relatives. It allows us to act on the basis of reason. It can preclude an overwhelming tendency for action (for example, to run from a fire in a crowded theater) because an abstract memory ("don't panic") makes more sense. It knows that all that glitters is not gold. Without a prefrontal cortex, it would be impossible to have societies based on moral and legal codes. .

Sometimes violent behavior may be adaptive (for example, in self-defense), in which case the prefrontal cortex will help plan an effective strategy. However, controlling violent impulse when they are maladaptive can be very taxing duty for the prefrontal cortex, especially if the desire for action is great or if the brain is weakened in its capacity to

exercise such control.

. Many factors can impair the capacity of the prefrontal cortex to serve its full impulse-control function: for example, neurological diseases that kill cells in the prefrontal cortex, head injuries that damage these cells, alcohol and drugs that impair their function and biological immaturity. ..' . . . , ',

The inhibitory functions are not present at birth; it takes many years for the necessary biological processes to hone a prefrontal cortex into an effective, efficient executive. These .processes are now being identified by scientific research. They involve how nerve cells communicate with each other, how they form interactive networks to handle complex computational tasks and how they respond to experience. It takes at least two decades to form a fully functional prefrontal cortex. .

Scientists have shown that the pace of the biological refinements quickens considerably in late adolescence, as the brain makes a final maturational push to tackle the exigencies of independent adult life. .

But the evidence is unequivocal that the prefrontal cortex of a 15-year-old is biologically immature. The connections are not final, the networks are still being strengthened and the full capacity for inhibitory control is still years away.

The 15-year-old brain does not have the biological machinery to inhibit impulses in the service of long-range planning. This is why it is important for adults to help children make plans and set rules, and why institutions are created to impose limits on behavior that children are incapable of limiting.

Parents provide their children with a lend-lease prefrontal cortex during all those years that it takes to grow one, particularly when the inner urges for impulsive action intensify.

Adolescents have always had to deal with' feeling hurt, ashamed and powerless. In the face of ridicule, they may want revenge. Thirty years ago, a teenager in this position might have started a fight, maybe even pul1ed a knife If he was afraid that he could not defend himself, he might have recruited a tough guy to help him out. One way or another, he would have tried to teach his tormentors a lesson. Very likely, however, no one would have died. But times have changed, and now this angry teenager lives in a culture that romanticizes gunplay and may well himself have access to guns.

I doubt that most school shooters intended to kill, in the adult sense of permanently ending a life and paying the consequences for the rest of their lives. Such intention would require a fully developed prefrontal cortex, which could anticipate the future and rationally appreciate cause and effect.

The young school shooter probably does not think about the specifics of shooting at all. The often reported lack of apparent remorse illustrates how unreal the reality is to these teenagers.

This brief lesson in brain development is not meant to- absolve criminal behavior or make the horrors any less unconscionable. But Williams, like other adolescents, needed people or institutions to prevent him from being in a potentially deadly situation where his immature brain was left to its own devices.

No matter what the town or the school, if a gun is put in the control of the prefrontal cortex of a hurt and vengeful 15-year-old, and it is pointed at a human target, it will very likely go off.

Daniel R. Weinberger is director of the Clinical Brain Disorders Laboratory' at the National Institutes of Health. This article appeared in the New York Times.

HOW DO YOU LOCK THIS TRIGG£R. SAC BEE 3/4/01

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