New York Times' Well blog:
In studies at Temple University, psychologists used functional magnetic resonance imaging scans on 40 teenagers and adults to determine if there are differences in brain activity when adolescents are alone versus with their friends. The findings suggest that teenage peer pressure has a distinct effect on brain signals involving risk and reward, helping to explain why young people are more likely to misbehave and take risks when their friends are watching.
For parents, the study data reinforce the notion that groups of teenagers need close supervision.
“All of us who have very good kids know they’ve done really dumb things when they’ve been with their friends,” Dr. Steinberg said. “The lesson is that if you have a kid whom you think of as very mature and able to exercise good judgment, based on your observations when he or she is alone or with you, that doesn’t necessarily generalize to how he or she will behave in a group of friends without adults around. Parents should be aware of that.”
Tips for safeguarding and monitoring teenagers is available at Parents: The Anti-Drug.