Behold the American teenager, a lump in a hoodie who's capable of little more than playing "Grand Theft Auto," raiding the liquor cabinet, and denting the minivan, thanks to a brain so unformed that it's more like a kindergartner's than a grown-up's. That's the message that seemed to emerge from the past decade's neuroscientific discoveries: that the brain, once thought to be virtually complete by age 6, is very much a work in progress during adolescence and not to be trusted. But experts now are realizing that the popular parental response—to coddle teens in an attempt to shield them from every harm—actually may be counterproductive.
Yes, teenagers make woefully errant decisions that factor big in the 13,000 adolescent deaths each year. And yes, their unfinished brains appear to be uniquely vulnerable to substance abuse and addiction. But they also are capable of feats of learning and daring marvelous enough to make a grown-up weep with jealousy. How they exercise these capabilities, it now appears, helps shape the brain wiring they'll have as adults. "You have this power you're given," says Wilkie Wilson, codirector of DukeLEARN, a new program at Duke University designed to teach teenagers how to best deploy their brains. Far from coddling the kids, he says, Mom and Dad need to figure out how to allow enough "good" risk-taking to promote growth and prevent wasted talent—while also avoiding disaster.
It can be a nerve-racking exercise. "These kids are such a crazy mix of impulsiveness and shrewdness," says Marcia Harrington, a survey researcher in Silver Spring, Md. She recalls the time she thought her then 16-year-old daughter, Alexandra Plante, had sleepover plans, but the girl instead ditched school and flew to Chicago to visit an acquaintance she'd met briefly during a family trip. The scheme was revealed only because bad weather delayed the flight home. Alex returned unharmed and has never conceded that the escapade was too risky. "She's going to be a great adult someday," says Harrington. "But, boy, there are moments that are terrifying." Further along the road to adulthood now, Alex has applied her daring spirit to becoming an emergency medical technician and volunteer for the local fire department, and to heading off to college 2,500 miles from home.
Taking a peek under the hood. While society has known since forever that adolescents can be impulsive risk-takers, it wasn't until the 1990s, when MRI scans became a common research tool, that scientists could peek into the teenage cranium and begin to sort out why. What they found astonished them. The brain's gray matter, which forms the bulk of its structure and processing capacity, grows gradually throughout childhood, peaks around age 12, and then furiously "prunes" underused neurons.
By scanning hundreds of children as they've grown up, neuroscientists at the National Institute of Mental Health have been able to show that the pruning starts at the back of the brain and moves forward during adolescence. Regions that control sensory and motor skills mature first, becoming more specialized and efficient. The prefrontal cortex, responsible for judgment and impulse control, matures last. Indeed, the prefrontal cortex isn't "done" until the early 20s—and sometimes even later in men. Meantime, the brain's white matter, which acts as the cabling connecting brain parts, becomes thicker and better able to transmit signals quickly. Recent research shows that this myelination process of white matter continues well past adolescence, perhaps even into middle age.
Now, dozens of researchers are studying how all these changes might affect adolescent behavior, and also shape adult skills and behavior, for good and for ill. The maturation lag between emotional and cognitive brain centers may help explain why teenagers get so easily upset when parents see no reason, for example; teens seem to process input differently than do adults.
In one experiment, young teenagers trying to read the emotions on people's faces used parts of the brain designed to quickly recognize fear and alarm; adults used the more rational prefrontal cortex. Deborah Yurgelun-Todd, the researcher at McLean Hospital in Belmont, Mass., who led this work, believes young teens are prone to read emotion into their interactions and miss content. Therefore, parents may have better luck communicating with middle-schoolers if they avoid raising their voice (easier said than done) and instead explain how they're feeling.