Unexpected experimental result suggests young people’s brains can be tamed

By Laura Sanders

Web edition: October 15, 2012
Print edition: November 17, 2012; Vol.182 #10 (p. 14)

The oft-maligned teenage brain is getting some reputation rehab. When offered the incentive of a modest reward in a recent experiment, teens took more time than adults to make a thoughtful, reasoned decision.

That surprising result, presented October 14 at the annual meeting for the Society for Neuroscience, counters the image of a flaky, impulsive adolescent brain, and shows that incentives may be a powerful way to curb reckless behavior. 

“Teenagers are quite capable of waiting, as opposed to reacting impulsively,” said study coauthor BJ Casey of Weill Cornell Medical College in New York City at a press briefing.  The result “really flies in the face of some of my previous research and research by other investigators,” she said.

Casey and her colleague Theresa Teslovich spotted the contemplative teenage brain as participants had to decide which way a cloud of dots was moving across a computer screen. Random jitters of individual dots made it hard to detect the direction of overall motion. When playing for a reward—in this case, five arbitrary points—teenagers took longer than adults to decide. This delay, the researchers think, allowed teenagers to accumulate more information before making up their minds.

“Here’s an example in which we’re seeing adolescents being not impulsive at all, but in fact, incredibly thoughtful before making a decision,” Casey said.

Brain scans helped the researchers pinpoint the neural origins of this teenage thoughtfulness. When points were on the line, both adults and teenagers had a boost of brain activity in the ventral striatum, a region that handles rewards. But there was a big difference between the teen brains and adult brains in other regions that deal with decision making. Compared with adults, teenagers showed much higher brain activity in the prefrontal cortex and parietal cortex, perhaps reflecting the buildup of evidence.

Finding evidence that teens can be measured in their decision making is surprising, said neuroscientist Jay Giedd of the National Institute of Mental Health in Bethesda, Md. “It doesn’t fit the stereotype,” he said.

The results may be context-dependent, Giedd said. Other studies (and no doubt centuries of personal observation) argue that teenagers are more impulsive than adults. Teenagers have trouble keeping their eyes on a target when a distraction hovers nearby, for instance. But the new results are encouraging because they show that this impulsivity, in certain situations, can be managed, Giedd said. “It’s there, but it’s not something that’s insurmountable.”