For the past six years, my colleague Jason Chein and I have been studying how peers affect adolescent decision-making. It is well known, for example, that a great deal of teenagers' risky behavior occurs when they are with their friends. In 2005, Margo Gardner and I published an experiment showing that, when adolescents played a video driving game with their friends watching, they took more chances (and crashed more often) than they did when alone, but we found no such peer effect on adults. Jason, who is a neuroscientist, and I wanted to understand what the underlying neural processes for this might be.
Studying peer influence in the fMRI environment is a challenging task, because we can't squeeze a group of people into the scanner at the same time. So we set up the adolescent's peers in an adjacent room, where they could see how the adolescent was "driving" when playing the game inside the magnet. We had a mike wired from that room into the scanner, so that the friends could let the adolescent know when they were watching.