What’s Up With Teenagers?

From the Marshall Memo #441

In this thought-provoking National Geographic article, David Dobbs examines the impulsive, supposedly dysfunctional teenage brain through the lens of evolutionary science. He begins by describing the phone conversation he had with his 17-year-old son after he was arrested for driving “a little fast.” How fast was that? Dobbs inquired. “Turns out this product of my genes and loving care, the boy-man I had swaddled, coddled, cooed at, and then pushed and pulled to the brink of manhood, had been flying down the highway at 113 miles an hour.” The boy was contrite, but he was also upset about being booked for (among other things) “reckless” driving. “It’s just not accurate,” he protested. “Reckless sounds like you’re not paying attention. But I was. 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. I mean, I wasn’t just gunning the thing. I was driving.” 

What explains this kind of behavior? What are teenagers thinking? Complaints about their erratic behavior go back to Aristotle and Shakespeare, but modern brain scans are providing a more complex explanation. As young people move through adolescence, their brains go through an extensive remodeling – basically a network and wiring upgrade. The brain’s axons are gradually coated with myelin, boosting their transmission speed up to a hundred times. The dendrites get twiggier and the most heavily-used synapses grow richer and stronger while those that aren’t being used wither away. The cortex, where most complicated thinking takes place, becomes thinner and more efficient. The corpus callosum, which connects the two hemispheres, gets progressively thicker, and the hippocampus, which acts as a memory directory, forms more robust connections to other parts of the brain, making it easier for the person to set goals, weigh different options, and integrate memory and experience. 

The most intriguing finding is that these physical changes move in a slow wave from the rear of the brain to the front – from the brain stem (which controls vision, movement, and basic processing) to the front, where higher-order thinking takes place. 

“When this development proceeds normally,” says Dobbs, “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. But at times, and especially at first, the brain does this work clumsily. It’s hard to get all those new cogs to mesh… These studies help explain why teens behave with such vexing inconsistency: beguiling at breakfast, disgusting at dinner; masterful on Monday, sleepwalking on Saturday. Along with lacking experience generally, they’re still learning to use their brain’s new networks… They act that way because their brains aren’t done! You can see it right there in the scans!” 

But a different theory about the adolescent brain is emerging. Scientists are moving from the “immature brain” model to believing that the teenager is, Dobbs explains, “an exquisitely sensitive, highly adaptable creature wired almost perfectly for the job of moving from the safety of home into the more complicated world outside.” This theory is more flattering to teens, and it’s also a better fit with Darwin’s survival of the fittest – a construct that has no room for dysfunctional traits. “If adolescence is essentially a collection of them – angst, idiocy, and haste; impulsiveness, selfishness, and reckless bumbling – then how did those traits survive selection?” asks Dobbs. “They couldn’t – not if they were the period’s most fundamental or consequential features.” 

His point is that these annoying features aren’t the most fundamental and consequential characteristics of adolescence. They’re just the ones that are bugging us. “To see past the distracting, dopey teenager and glimpse the adaptive adolescent within,” says Dobbs, “we should look not at specific, sometimes startling, behaviors, such as skateboarding down stairways or dating fast company, but at the broader traits that underlie those acts.” Here are four:

• The love of novelty and excitement – “Sensation-seeking, the hunt for the neural buzz, the jolt of the unusual or unexpected – these are at their height during the teen years,” says Dobbs. Not all of it is impulsive, viz. his son’s carefully planned 113-mph drive. Impulsivity drops throughout life, but thrill-seeking soars at 15. Not all of it is dangerous. “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,” says Dobbs. “A love of novelty leads directly to useful experience. More broadly, the hunt for sensation provides the inspiration needed to ‘get out of the house’ and into new terrain…”

• Risk-taking – From unprotected sex to driving too fast to experimenting with alcohol and drugs, high-risk behavior spikes from 15 to 25. One-third of deaths among American teens are from auto accidents, many involving drunkenness. Isn’t this the immature brain talking? Not so, say scientists who have carefully studied adolescent thought patterns. It turns out that 14-17-year-olds, the biggest risk-takers, use the same basic cognitive strategies as adults, are fully aware of their mortality, and overestimate risks. Teens take more chances than adults because they weigh risks and rewards differently. “In situations where risk can get them something they want, they value the reward more heavily than adults do,” says Dobbs. And one of the most powerful payoffs for teens is social – the approval of their peers. This is why there are fewer accidents when a teenager is driving alone. Adolescents’ brains are especially sensitive to the neural hormones dopamine and oxytocin, which are associated with pleasure and social connection. “Engage one, and you often engage the other,” says Dobbs. “Engage them during adolescence, and you light a fire.” 

• Preferring peers – “Teens prefer the company of those their own age more than ever before or after,” he says. This is about the quest for novelty – peers offer much more of this than the family – and also investing in the future rather than the past. “We enter a world made by our parents,” he says. “But we will live most of our lives, and prosper (or not) in a world run and remade by our peers. Knowing, understanding, and building relationships with them bears critically on success… This supremely human characteristic makes peer relations not a sideshow but the main show. 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. Knowing this might make it easier to abide the hysteria of a 13-year-old deceived by a friend or the gloom of a 15-year-old not invited to a party.”

• Prolonged plasticity – The final trait of adolescence revealed by brain research is that the frontal lobes – which control higher-order thinking – are the last to lay down the myelin insulation that increases processing power so dramatically. “At first glance this seems like bad news,” says Dobbs: “If we need these areas for the complex tasks of entering the world, why aren’t they running at full speed when the challenges are most daunting?” But once the frontal lobes are myelinized, they become less flexible; when the wiring upgrade is finished, it’s harder to adapt and change. “This delayed completion – a withholding of readiness – heightens flexibility just as we confront and enter the world we will face as adults,” says Dobbs. “This long, slow, back-to-front developmental wave, completed only in the mid-20s, appears to be a uniquely human adaptation. It may be one of our most consequential. It can seem a bit crazy that we humans don’t wise up a bit earlier in life. But if we smartened up sooner, we’d end up dumber.” 

The desire for excitement, novelty, risk, and the company of peers is dominant among adolescents in virtually all human cultures around the world, and has been, say anthropologists, for thousands of generations. This suggests that the four traits described above evolved for a reason: to help humans leave a safe home and move into uncharted territory. “The move outward from home is the most difficult thing that humans do, as well as the most critical,” says Dobbs, “not just for individuals but for a species that has shown an unmatched ability to master challenging new environments. In scientific terms, teenagers can be a pain in the ass. But they are quite possibly the most fully, crucially adaptive human beings around. Without them, humanity might not have so readily spread across the globe.” 

Seeing adolescence as evolutionarily adaptive is intriguing, but Dobbs acknowledges that “natural selection swings a sharp edge, and the teen’s sloppier moments can bring unbearable consequences. We may not run the risk of being killed in ritualistic battles or being eaten by leopards, but drugs, drinking, driving, and crime take a mighty toll… Our children wield their adaptive plasticity amid small but horrific risks.” Adults struggle to help their teenagers get through the dangerous years safely, spending around $1 billion on a variety of sex ed, drug ed, drivers ed, and other programs. Unfortunately, most of them aren’t very effective. 

Why don’t teens listen to us? Because they prefer to learn from their friends. But sometimes they will listen to adults – especially when we offer wisdom from our own struggles as adolescents. 

“Beautiful Brains” by David Dobbs in National Geographic, October 2011 (Vol. 220, #4, p. 36-59), http://ngm.nationalgeographic.com/2011/10/teenage-brains/dobbs-text