You view a screen on which the red crosshairs at the center occasionally disappear just as a light flickers elsewhere on the screen.
Your instructions are to not look at the light and instead to look in the opposite direction. It's a tough assignment, since flickering lights naturally draw our attention.
"Well," I huffed, sensing an opportunity to finally yell at him, "what would you call it? " 'Reckless' sounds like you're not paying attention. I made a deliberate point of doing this on an empty stretch of dry interstate, in broad daylight, with good sight lines and no traffic. —and revealed an answer that surprised almost everyone.
Our brains, it turned out, take much longer to develop than we had thought.
But at times, and especially at first, the brain does this work clumsily. Beatriz Luna, a University of Pittsburgh professor of psychiatry who uses neuroimaging to study the teen brain, used a simple test that illustrates this learning curve.
Luna scanned the brains of children, teens, and twentysomethings while they performed an antisaccade task, a sort of eyes-only video game where you have to stop yourself from looking at a suddenly appearing light.
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.
Abigail Baird, a Vassar psychologist who studies teens, calls this neural gawkiness—an equivalent to the physical awkwardness teens sometimes display while mastering their growing bodies.The corpus callosum, which connects the brain's left and right hemispheres and carries traffic essential to many advanced brain functions, steadily thickens.Stronger links also develop between the hippocampus, a sort of memory directory, and frontal areas that set goals and weigh different agendas; as a result, we get better at integrating memory and experience into our decisions.But as we move through adolescence, the brain undergoes extensive remodeling, resembling a network and wiring upgrade.
For starters, the brain's axons—the long nerve fibers that neurons use to send signals to other neurons—become gradually more insulated with a fatty substance called myelin (the brain's white matter), eventually boosting the axons' transmission speed up to a hundred times.
The brain doesn't actually grow very much during this period.