Why do some teens drive fast, drink too much and obsess about their social lives? The traditional narrative has been that teens' brains are a work in progress or "still under construction." But that's not the whole story. A recent National Geographic article explored the evolutionary logic of teenage thought, and why thrill-seeking and risk-taking may be beneficial.
In our teens and early 20s, our brains go through changes that make it harder to learn new things but make us better at what we already know. This transformation shows up as a significant but not insurmountable solidifying of brain structure, and while it's happening teens experience mental and emotional instability. We know that socially this is "a delicate time in a young person's life," but it's true on a neurological level as well. According to a paper published recently in Archives of General Psychiatry, patients with schizophrenia showed a larger loss of gray matter during the adolescent transformation than did healthy subjects.
During adolescence, we respond strongly to the neurotransmitter dopamine and the hormone oxytocin, which influence the brain's reward systems and empathy, respectively. This helps explain teens' 'sensation-seeking,' whether that comes in the form of daredevil stunts or social climbing. Dobbs notes that "Some brain-scan studies, in fact, suggest that our brains react to peer exclusion much as they respond to threats to physical health or food supply. At a neural level, in other words, we perceive social rejection as a threat to existence." But insofar as a teen's social skills determine much of his or her bearing in an adult community later on, social underperformance among prehistoric teens may really have been (almost) life or death.
"Although sensation seeking can lead to dangerous behaviors," Dobbs says, "it can also generate positive ones: The urge to meet more people, for instance, can create a wider circle of friends, which generally makes us healthier, happier, safer, and more successful."
This sort of evolution-via-delayed-gratification is far from unprecedented, showing up in the brain development of younger children as well. We know that human brains are relatively underdeveloped in their first years, compared with the brains of other large mammals. But this handicap, too, may have a straightforward evolutionary explanation: in a landmark 1981 paper, L. Godfrey and K.H. Jacobs theorized that if our extremely complex brains were any larger, our skulls wouldn't fit through the birth canal.
Unfortunately, it's much tougher to see the long term benefits of our small baby-brains and our emotional teenage-brains than it is to see helpless infants and reckless teens. As long as teenagers make mistakes, we'll probably continue to think of them as "under construction," even if we know it's good for them.