"The New York Times" March 10, 2001
A Brain Too Young for Good Judgment

By DANIEL R. WEINBERGER

This week's shootings at Santana High School in California 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 15-year-old is not mature =E2=80=94 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 millennia 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, (e.g., to run from a fire in a crowded
theater), because an abstract memory (e.g., "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 impulses when
they are maladaptive can be a 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.

 =C2 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 pulled 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 he may well have access to
guns. I doubt that most school shooters intend to kill, in the
adult sense of permanently ending a life and paying the price for
the rest of their own 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
the shooter at Santana High, 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.
 
Oryginal:
http://www.nytimes.com/2001/03/10/opinion/10WEIN.html?ex=3D985228761&ei=3D=1&en=3D70e99a4b01be3b61

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