Thrill seeking and poor judgment go hand in hand when it comes to teenagers—an inevitable part of human development determined by properties of a growing but immature brain. Right? Not so fast. A new study turns that thinking upside down: The brains of teens who behave dangerously are more like adult brains than are those of their more cautious peers.

Psychologists have long believed that the brain's judgment-control systems develop more slowly than emotion-governing systems, not maturing until people are in their mid-20s. Hence, teens end up taking far more risks than adults do. Evidence supporting this idea comes from studies looking at functional and structural properties of gray matter, the important part of the brain that contains the neurons that relay brain signals.

At least two observations undermine this theory, however. First, American-style teen turmoil is absent in more than 100 cultures around the world, suggesting that such mayhem is not biologically inevitable. Second, the brain itself changes in response to experiences, raising the question of whether adolescent brain characteristics are the cause of teen tumult or rather the result of lifestyle and experiences. Because brain research is virtually always correlational in design, determining whether brain properties are causes or effects is impossible.

Now neuroscientists Gregory S. Berns, Sara Moore and Monica Capra of Emory University suggest that teen risk-taking is associated not with an immature brain but with a mature, adultlike brain—exactly the opposite of conventional wisdom.

The new research discovered a strong positive correlation between engagement in dangerous behaviors and increased brain white matter, typical of mature brains. In other words, young people who engage in dangerous behaviors generally have a more adultlike brain than their conservative peers.

If valid, the study has important implications for interpreting risk-taking in teens. It suggests that the brains of many teens who behave dangerously are maturing early. The new study says nothing about causation, just like the gray matter studies. "Could someone whose brain develops earlier start to engage in adult activities earlier?" That is one possibility, Berns says, but it is also possible that "engaging in adult activities makes the brain mature faster."

Source: Scientific American
http://www.scientificamerican.com/article.cfm?id=are-teens-who-behave-reck