It was the brain scans she took while people took the test.
Compared with adults, teens tended to make less use of brain regions that monitor performance, spot errors, plan, and stay focused—areas the adults seemed to bring online automatically.
At the same time, the frontal areas develop greater speed and richer connections, allowing us to generate and weigh far more variables and agendas than before.
When this development proceeds normally, we get better at balancing impulse, desire, goals, self-interest, rules, ethics, and even altruism, generating behavior that is more complex and, sometimes at least, more sensible.
Luna suspects the improvement comes as richer networks and faster connections make the executive region more effective.
This let the adults use a variety of brain resources and better resist temptation, while the teens used those areas less often and more readily gave in to the impulse to look at the flickering light—just as they're more likely to look away from the road to read a text message.
If offered an extra reward, however, teens showed they could push those executive regions to work harder, improving their scores.
Although you know your teenager takes some chances, it can be a shock to hear about them. Through the ages, most answers have cited dark forces that uniquely affect the teen.
One fine May morning not long ago my oldest son, 17 at the time, phoned to tell me that he had just spent a couple hours at the state police barracks. He did not object when I told him he'd have to pay the fines and probably for a lawyer. My son's high-speed adventure raised the question long asked by people who have pondered the class of humans we call teenagers: What on Earth was he doing? But even that is just another way of wondering, What is wrong with these kids? Aristotle concluded more than 2,300 years ago that "the young are heated by Nature as drunken men by wine." A shepherd in William Shakespeare's The Winter's Tale wishes "there were no age between ten and three-and-twenty, or that youth would sleep out the rest; for there is nothing in the between but getting wenches with child, wronging the ancientry, stealing, fighting." His lament colors most modern scientific inquiries as well. Stanley Hall, who formalized adolescent studies with his 1904 Adolescence: Its Psychology and Its Relations to Physiology, Anthropology, Sociology, Sex, Crime, Religion and Education, believed this period of "storm and stress" replicated earlier, less civilized stages of human development.