Why Teenagers Are New

Key concepts

Every work — at a glance

• The Invention of the Teenager — — (social history)

  The word appears around 1900 but only takes hold after the Second World War, when compulsory high school (US enrolment roughly 30% to 60% between 1920 and 1936), teenage income and cars built a life stage large enough to have a culture of its own.

• Prefrontal Cortex — — (term)

  The brain's planning-and-brakes region, and the last to finish maturing — still rewiring through the teens and into the thirties, which is why a teenager can argue like an adult and still act on impulse.

• Neural Pruning — — (term)

  Adolescence trims the rarely-used connections childhood over-built so the busy pathways run faster. Grey matter shrinks, and the shrinking is a gain — but whatever you practise now is what survives the cut.

• Risk-taking — — (term)

  A timing mismatch rather than stupidity: the reward system matures early and says go while the prefrontal brake is still being built. The gap widens when friends are watching.

• Neophilia — — (term)

  Love of the new — the adolescent pull toward unfamiliar music, food and ideas. Peter Marler called the equivalent window in young songbirds an 'instinct to learn': they sit beside adult singers and copy the tune.

• Differentiation — — (term)

  The work of becoming your own person by separating from your family's identity. Its animal parallel is dispersal — the young must leave the burrow or pack, and the leaving is rarely peaceful.

• The Scans That Stopped at Twenty — Nitin Gogtay (study)

  Gogtay's team rescanned the same children every two years and stopped at age 20, so nobody could say when the frontal lobe finished. Twenty-five was a best guess past the edge of the data — and it hardened into a fact.

• Back to Front — — (finding)

  Inside the frontal lobe the regions mature in order, from the back forward. The parts that move your muscles finish early; the parts that weigh a decision, hold a temper and read a room finish last.

• The Brain's Adolescence Ends at Thirty-two — — (study)

  A study of more than 4,200 brains, from babies to ninety-year-olds, found one long developmental phase running from age nine to thirty-two. Its authors named that whole stretch adolescent — which puts most graduates inside it.

• Neighbourhoods and Highways — — (concept)

  A growing brain does two opposite jobs. Segregation builds neighbourhoods of related thought; integration builds highways between them. Teens and twenties are spent laying highways; the thirties are spent maintaining the busiest routes.

• Teenocratic — Derek Thompson (term)

  Derek Thompson's word for the flip. Most old societies were gerontocratic, run by the oldest. Modern culture is teenocratic: the young set the taste in music, clothes and technology, and everybody older plays catch-up.

• Hoover's Appalling Increase — J. Edgar Hoover (historical event)

  In 1953 the FBI's J. Edgar Hoover predicted 'an appalling increase in the number of crimes that will be committed by teenagers in the years ahead'. Two years later Eisenhower asked Congress for money to fight it.

• Keep Away from the Fellow Who Owns an Automobile — Irving Berlin (song)

  Irving Berlin's 1909 warning song: 'He'll take you far in his motor car — too darn far from your Pa and Ma.' Before the car, a first date meant talking to her parents in their front room.

• Seduction of the Innocent — Fredric Wertham (book)

  Fredric Wertham's bestseller blamed comic books for juvenile crime on thin evidence. He called Superman a fascist and said Wonder Woman turned women into lesbians — and the book helped put American comics under censorship.

• The Line Socrates Never Said — — (misattribution)

  'Our youths now love luxury. They have bad manners, contempt for authority… they tyrannize their teachers.' The complaint is quoted everywhere as Socrates from the fifth century BC. No ancient text contains it.

• Check Here If a Veteran — — (historical event)

  A 1947 magazine piece called the five million Americans who were aged 10 to 13 at Pearl Harbor a lost generation. They were born too late to fight, and every job form carried a box they could not tick.

• A Leisure Class of the Young — — (criticism)

  A 1957 critic put the whole argument in one sentence: ending child labour and lengthening school 'have given us a huge leisure class of the young, with animal energies never absorbed by tasks of production'.

• Twice as Many Chances — Laurence Steinberg (study)

  Laurence Steinberg put drivers of every age in a simulator. Adults drove the same whether or not anyone watched. Teenagers took twice as many chances — running a yellow light — when their friends were in the room.

• The Nucleus Accumbens — — (term)

  The brain's reward centre, enlarged in adolescence while the brake is still being built. Adults see the downside of a risk in high definition; teenagers see the payoff as if it were on an IMAX screen.

• Coolness as Positive Rebellion — — (concept)

  Sociology's definition: breaking away from a mainstream you can show is unfair, in a way other people accept. Break a rule nobody thinks is unfair — an untucked shirt at a funeral — and the same act reads as rude.

• The Logo and the Screen — — (social history)

  In the 1980s and 1990s teenagers spent their money on logos: a Ralph Lauren emblem had real power in a school hallway. The smartphone replaced it. Now Snapchat and Instagram are the hallway.

• School Instead of the Mill — — (social history)

  Compulsory schooling began as a countermovement against child labour in factories. School buses then ended the one-room schoolhouse and packed hundreds of same-age young people into one building, where they could make their own rules.

• The Richest Fifth Doubled Down — — (statistic)

  Since the 1970s the wealthiest fifth of American households have more than doubled what they spend on childhood enrichment — camps, sports, tutors. Fewer children per family, and far more money aimed at each one.

• The Sea Otters and the Shark — Barbara Natterson-Horowitz (finding)

  In Wildhood, Barbara Natterson-Horowitz describes adolescent sea otters darting in groups into great white shark territory. It looks suicidal. It is probably how they learn a predator's habits in time to survive being adults.

• The Female Chimpanzee Leaves — Rachna Reddy (finding)

  In most species the males travel farthest and take the bigger risks. Rachna Reddy's chimpanzees reverse it: the adolescent females leave, walking into a neighbouring group that has been hostile to their family.

• Dispersal — — (term)

  The young of many species must leave their pack, burrow or birthplace, and the reason is genetic: staying means breeding with relatives. The cost is long travel through unknown ground full of predators.

• Teen-age Triumphs — — (historical event)

  Britain met the word through clothes. One of the earliest British uses is a 1945 fashion spread in The Sketch headed 'Teen-age Triumphs'. The term existed before the war but only caught on in the late 1940s.

What to know

1. 01
   Why is the teenager so new when adolescence is ancient? Because the word names a social slot, not a body. Three mid-century forces built the slot: compulsory high school put thousands of same-age young people together away from their families, rising income gave them money of their own, and cars gave them somewhere to take it.
2. 02
   The brain offers no finish line either. Pruning and prefrontal maturation run on for decades, so the popular 'the brain is done at 25' is a leftover from 1990s scans rather than a fact — newer imaging tracks change well into the thirties.

Across subjects