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: Reckless behavior might in fact be a sign of adultness. Some adults do risky things (speeding, drinking, having unprotected sex) quite commonly without causing great alarm. Automatically considering such behaviors to be more objectionable just because someone is young runs into what the researchers call in their paper "a conundrum of defining risk (or dangerousness) based not on the objective attributes of the activity but on the person engaging in them."
Room for skepticism
Berns also acknowledges that 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, he says, but it is also possible that "engaging in adult activities makes the brain mature faster," he says.
Not everyone thinks the new study will overturn thinking about the teenage brain. Developmental psychologist Laurence Steinberg of Temple University says he has been aware of the Berns research for several years and that it is flawed. "There are findings from other studies that in some respects contradict these findings," Steinberg says. "For instance, it's been shown that individuals with more developed white matter tracts are less oriented toward immediate rewards and less susceptible to peer pressure”—meaning they are probably less prone to risk-taking.
Michael S. Gazzaniga of the University of California, Santa Barbara, one of the pioneers in modern neuroscience, sees the Berns study more positively. The large number of subjects makes the results hard to ignore, he says, and they need to be taken seriously. Says Gazzaniga: "So much for the much touted model that the tumultuous teenage brain is that way because it is not fully developed. Back to the drawing board again."