A WSJ review of a new book on bullying begins with a description of an experiment conducted by Temple psychologist Laurence Steinberg. Subjects played a driving game requiring swift risk-evaluation and decision-making while wired to brain-scanning machines. In teens, the parts of the brain associated with rewards lit up under the observation of their peers. They drove more recklessly and crashed more often. Steinberg called the results "one very plausible explanation for why adolescents do a lot of stupid things with their friends that they wouldn't do when they are by themselves."