Like the other parts of the body, different parts of the brain grow at different rates. Myelination and maturation occur in sequence, proceeding from the lower and inner parts of the brain to the cortex and from the back to the prefrontal cortex (Sowell et al., 2007). That means that the limbic system (site of fear, anxiety, and other intense emotions) matures before regions where planning, emotional regulation, and impulse control occur.

Furthermore, pubertal hormones target the amygdala and other crucial parts of the HPA axis directly (Romeo, 2013), but full functioning of the cortex requires maturation and experience beyond the teen years. Thus, the instinctual and emotional areas of the adolescent brain develop ahead of the reflective, analytic areas. Puberty means emotional rushes, unchecked by caution. Immediate impulses thwart long-term planning.

Brain scans confirm that emotional control, revealed by fMRI studies, is not fully developed until adulthood. During adolescence, the prefrontal cortex is limited in connections and engagement (Luna et al., 2013).

When compared with the brains of emerging adults, adolescent brains show heightened arousal in the brain’s reward centers. Teens seek excitement and pleasure, especially the social pleasure of a peer’s admiration (Galván, 2013). In fact, when others are watching, teens find it thrilling to take dramatic risks that produce social acclaim, risks they would not dare take alone (Albert et al., 2013).

The fact that the frontal lobes are the last to mature may explain something that has long bewildered adults: Especially when they are with their friends, many adolescents seek the thrill of new experiences and sensations, forgetting the caution that their parents have tried to instill. The following is one example.

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The normal sequence of brain maturation (limbic system at puberty, then prefrontal cortex sometime in the early 20s) combined with the earlier onset of puberty means that, for contemporary teenagers, emotions rule behavior for a decade. The limbic system makes powerful sensations—loud music, speeding cars, strong drugs—compelling.

It is not that the prefrontal cortex shuts down. Actually, it continues to mature throughout childhood and adolescence, and, when they think about it, adolescents are able to assess risks better than children are (Pfeifer et al., 2011). The balance and coordination between the various parts of the brain is awry, even as the brain continues to develop (Casey et al., 2011).

When stress, arousal, passion, sensory bombardment, drug intoxication, or deprivation is extreme, the adolescent brain is flooded with impulses that might shame adults. Teenagers brag about being so drunk that they were “wasted,” “bombed,” “smashed”—a state most adults try to avoid and would not admit.

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Also, unlike most adults, many teenagers choose to spend a night without sleep, to eat nothing all day, to exercise in pain, or to risk parenthood or an STI by not using a condom. The parts of the brain dedicated to analysis are immature until long after the first hormonal rushes and sexual urges begin.

Sadly, teenagers have access to fast cars, lethal weapons, and dangerous drugs before their brains are ready. My friend said to his neighbor, who gave his son a red convertible for high school graduation, “Why didn’t you just give him a loaded gun?” The mother of the 20-year-old who killed 20 children and 7 adults (including the mother) in Newtown, Connecticut, did just that.

A more common example of the cautious part of the brain being overwhelmed by emotions comes from teens sending text messages while they are driving. In one survey, among U.S. high school seniors who have driven a car in the past month, 60 percent texted while driving, even though that is illegal almost everywhere (MMWR, June 13, 2014).

More generally, despite quicker reflexes and better vision than adults, far more teenagers die in motor-vehicle accidents than older drivers do. Thoughtless impulses and poor decisions are almost always to blame, not skill.

Any decision, from whether to eat a peach to where to go to college, requires balancing risk and reward, caution and attraction. Experiences, memories, emotions, and the prefrontal cortex help people choose to avoid some actions and perform others. Since the reward parts of adolescents’ brains are stronger than the inhibition parts (Luna et al., 2013), many adolescents act in ways that seem foolhardy to adults.

It is easy to criticize adolescent behavior and blame it on hormones, peers, culture, or the latest chosen culprit, brains. Yet remember that difference is not always deficit. Gains as well as losses are part of every developmental period. There are benefits as well as hazards in the adolescent brain.

For instance, with increased myelination and slower inhibition, reactions become lightning fast. Such speed is valuable, making adolescent athletes potential superstars, quick and fearless as they steal a base, tackle a fullback, or sprint when their lungs feel about to burst. Ideally, coaches have the wisdom to channel such bravery.

Furthermore, as the brain’s reward areas activate positive neurotransmitters, teenagers become happier. A new love, a first job, a college acceptance, or even an A on a term paper can produce a rush of joy, to be remembered and cherished lifelong.

Societies need some people who question assumptions, and adolescents are primed to question everything, often raising issues that need to be raised. As social and ecological circumstances change, someone needs to think critically about having lots of children, or eating bacon every breakfast, or burning fossil fuels. If tradition were never questioned, customs would ossify, and societies die.

Further, teenagers need to take risks and learn new things, because “the fundamental task of adolescence—to achieve adult levels of social competence—requires a great deal of learning about the social complexities of human social interactions” (Peper & Dahl, 2013, p. 135). That is exactly what their brains enable adolescents to do.

Synaptic growth enhances moral development as well. Adolescents question their elders and forge their own standards. Values embraced during adolescence are more likely to endure than those acquired later, after brain connections are firmly established. This is an asset if adolescent values are less self-centered than those of children or are more culturally attuned than those of older generations.

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Thus the developing prefrontal cortex “confers benefits as well as risks. It helps explain the creativity of adolescence and early adulthood, before the brain becomes set in its ways” (Monastersky, 2007, p. A17). The emotional intensity of adolescents “intertwines with the highest levels of human endeavor: passion for ideas and ideals, passion for beauty, passion to create music and art” (Dahl, 2004, p. 21). One application: Since adolescents are learning lessons about life, adults who care about the next generation need to ensure those lessons are good ones.