It is well known that teenagers take risks — and that when they do, they like to have company. Teens are five times more likely to be in a car accident when in a group than when driving alone, and they are more likely to commit a crime in a group. Now, a new study sheds light on why. Temple psychologists Jason Chein and Laurence Steinberg set out to measure brain activity in adolescents — alone and with peers — as they made decisions with inherent risks. Their findings, published this month in Developmental Science, demonstrate that when teens are with friends they are more susceptible to the potential rewards of a risk than they are when they are alone.