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A recent interview with British neuroscientist Sarah-Jayne Blakemore, the author of the 2018 book Inventing Ourselves: The Secret Life of the Teenage Brain, begins with a caveat.

鈥淚 think it鈥檚 important to know before we start that up until 20 years ago we really didn鈥檛 know that the brain changes at all after childhood,鈥� she confides. 鈥淭hat鈥檚 what I was taught during my undergraduate degree. We now know that鈥檚 completely untrue.鈥�

In matters of settled opinion, science has often found itself in the role of provocateur, even saboteur鈥攑rodding at conventional wisdoms until they yield unexpected truths, and sometimes toppling them entirely. The mysteries of celestial bodies, heredity, and mental illness have all undergone dramatic rethinking.

So it shouldn鈥檛 be entirely surprising that new technologies that allow us to peer into the brain as it processes information are driving a revolution in our understanding of human cognition. Images from fMRI machines, for example, reveal that the brain is less like a collection of discrete, specialized modules鈥攐ne for speech and one for vision, the old model鈥攁nd more like an integrated network of functions that support each other. Those same images show that cerebral networks undergo dramatic, global maturation well into our 20s.

The findings have cast doubt on many theories about adolescence. For too long, assertions about teenagers鈥攆rom their purported irrationality to their apparent sense of invulnerability鈥攈ave circulated widely and uncritically. The new research suggests that we have plenty of rethinking to do.

Of Mice and Minors

Adolescent rodents and adolescent humans are susceptible to peer pressure鈥攁nd members of both species take risks at much higher rates when in the presence of companions their own age.

In , neuroscientist Laurence Steinberg asked teenagers and adults to play a virtual driving game that tested their willingness to take risks as traffic lights turned from green to yellow to red. Participants were penalized when accidents occurred. Adolescents responded to the risks as well as adults did聽and performed about equally when playing alone. But in the presence of peers, risk-taking surged among the teenagers and young adults鈥攔isky driving increased threefold for 13- to 16-year-olds, and the number of crashes spiked鈥攚hile remaining flat among adults.

A study involving mice and alcohol consumption reached a similar聽conclusion. That exposed rodents of different ages to the equivalent of an open bar: They could drink alcohol at their leisure. The adolescent mice鈥攖hose at the tender age of 4 to 5 weeks鈥攄rank about as often as adult mice when by themselves. But in the presence of other juveniles, they settled in for a bender, drinking 25 percent more of the time. There was no change in the drinking of adult mice.

These results aren鈥檛 just laboratory tricks. Using real crash data from 2007鈥�10, found that the risk of death for teenagers driving alone increased by 44 percent per mile when traveling with one peer, and quadrupled with three peers in the car. By contrast, Blakemore writes, traveling companions are actually a 鈥減rotective factor鈥� for adults over 26, 鈥渨ho are less likely to crash if they have a passenger than if they鈥檙e alone.鈥�

In a few recent experiments, peer pressure emerges as a measurable biological phenomenon, crossing over into the perceptible world like the first earthquake waves etched onto a seismograph. A 2013 study found that when human subjects were told that a peer was watching them, skin conductance readings鈥攁 measure of the electricity triggered by stress and arousal鈥攚ere consistently higher in adolescents than in either adults or children. Brain scans administered at the same time revealed telltale flares of greater activity in key regions of the teenage brain linked to self-awareness and the ability to understand others.

It鈥檚 never been聽a question of feeling invincible. For teenagers, there鈥檚 just something about the presence of peers that is transfiguring鈥攖hey understand the risks, and take them anyway.

A Telling Mismatch

A likely culprit in adolescent risk-taking is a brain network that stretches back deep into evolutionary history鈥攖he limbic system, the聽seat of primal instincts like fear, lust, hunger, and pleasure. 鈥淭hese are regions in the deep center of the brain,鈥� explained Blakemore. 鈥漈hey are much older, and we share these systems with a lot of other animals.鈥�

In 2014, Blakemore and two colleagues and plotted the growth rates of individual limbic systems over time. They also looked at another critical brain region: the prefrontal cortex.

The charts that resulted (above) show that limbic structures like the nucleus accumbens changed only modestly during adolescence while the prefrontal cortex experienced a dramatic shift in volume, shrinking and reorganizing as it pruned聽away unused synaptic connections. The upshot? The brain scans seem to indicate that the limbic system鈥攖he brain鈥檚 reward system鈥攊s mature and firing on all cylinders in teenagers, while the prefrontal cortex, which is responsible for things like self-control, planning, and self-awareness, is still busy developing.

鈥淥ne major theory of adolescent development is that there is a mismatch between these two systems,鈥� Blakemore elaborated. 鈥淭he limbic system, which gives you the rewarding feeling of taking risks, is structurally more developed before the prefrontal cortex, which stops you from taking risks.鈥�

If that seems too neat to you, Blakemore agrees. 鈥淚 wouldn鈥檛 discount social factors like changing schools,鈥� she cautions, or 鈥渙verlook individual differences in teenagers.鈥�

Still, there鈥檚 plenty of evidence that the limbic聽system is hyperactive during adolescence. It鈥檚 not youthful irrationality or a flair for the dramatic at work; teenagers actually experience things like music, drugs, and the thrill of speed more powerfully than adults do. In his 2014 book Age of Opportunity: Lessons From the New Science of Adolescence, Steinberg draws a straight line to peer influence as well, noting that teenage peers 鈥渓ight up the same reward centers that are aroused by drugs, sex, food, and money.鈥�

All Natural Plastic

It鈥檚 not all gloom and doom. The teenage years are 鈥渢he last, great neuroplastic era in our lifetimes,鈥� according to Steinberg, referring to the brain鈥檚 continued capacity for intellectual and emotional growth. The same emerging circuitry that makes teenagers vulnerable to risky behavior and mood swings also confers significant advantage on adolescent learners.

At the deep neural level, new information is written into the gray matter of the brain itself鈥攅xpressed in structural changes to synapses, which, through repeated exposure, form increasingly durable webs of memory. A provides a fascinating window into the brain at the very moment of learning. The chart above shows the electrical response in both adolescent and adult mice to a novel piece of information, represented by the red arrow. Like a bell struck more sharply, the brain of the adolescent mouse produces a more dramatic reply鈥攁nd then sustains it for longer.

That鈥檚 good news鈥攁nd a clear signal that the teenage brain is by nature more receptive to learning, says Frances Jensen in her 2015 book The Teenage Brain. Adolescent animals simply 鈥渟how faster learning curves than adults,鈥� and we retain the capacity聽to improve even fundamental attributes like our IQ well into our teenage years.

Reaching Teenagers in Class

Take the direct approach: Talking to teenagers frankly about their brain development can provide useful context for their emotional worlds, and reset their expectations about their potential for continued intellectual growth. 鈥淲e know that people like biological explanations. It鈥檚 true in neurological stroke patients鈥攕howing that the brain is plastic and can change and rehabilitate is really useful,鈥� Blakemore said.

Explaining the role of the limbic system, the influence of peers, and the malleability of the teenage brain establishes a basis for students to better understand themselves and exert control over their emotional and academic lives. Blakemore insists there鈥檚 also a simple question of respect at stake: 鈥淭hey have a right to know,鈥� she says emphatically. 鈥淚t鈥檚 happening in their brains.鈥�

Make good use of peer pressure: Peer pressure and social influence can be used for good, too. Smoking research shows, for example, that teens ignore warnings about the long-term health consequences of cigarettes, but respond to the social effects. It鈥檚 more convincing to remind teens that cigarettes 鈥済ive you bad breath, or put younger children in danger,鈥� said Blakemore. Teens 鈥渁lso respond to the idea that this is an adult industry that is exploiting them to make money. That has been shown to help for smoking and also for healthy eating.鈥�

Schools are aware of many of these social dynamics, and have used teen leaders, social influencers, and appeals to fairness and justice to change behaviors around vaping, bullying, and academic cheating.

Teach self-regulation: It鈥檚 not too late. The prefrontal cortex, which governs executive functions, is still developing and remains highly responsive to the environment and to training during adolescence. It stands to reason that explicitly teaching self-regulation, long-term planning, and empathy might have particular benefits for teenagers.

According to Steinberg, efforts to improve the self-regulation of teenagers 鈥渁re far more likely to be effective in reducing risky behavior than are those that are limited to providing them with information about risky activities.鈥� And social and emotional learning programs that show adolescents 鈥渉ow to regulate their emotions, manage stress, and consider other people鈥檚 feelings鈥� can have positive effects on executive functions more generally, improving focus and self-discipline, and setting teenagers up for academic and professional success well beyond high school.

The author of this article is the chief content officer at 麻豆传媒入口. You can follow him on Twitter .

The charts in this story聽were drawn by illustrator Leigh Wells, and adapted from studies by 1) Margo Gardner and Laurence Steinberg, 2005; 2) K.L. Mills, A.L. Goddings, L.S. Clasen, J.N. Giedd, and S.J. Blakemore, 2014; and 3) N.L. Schramm, R.E. Egli, and D.G. Winder, 2002, via Synapse magazine, courtesy of Wiley-Liss, Inc.