Sarah and Jim, 1988 & 2011. For the past three years, Argentine photographer Irina Werning has been staging reenactments of old snapshots. The project, “Back to the Future,” includes 270 photographs made in 29 countries.   (Photo: Irina Werning )

Throughout high school, my friend Kenji had never once spoken to the Glassmans. They were a popular, football-­playing, preposterously handsome set of identical twins (every high school must have its Winklevii). Kenji was a closeted, half-Japanese orchestra nerd who kept mainly to himself and graduated first in our class. Yet last fall, as our 25th high-school reunion was winding down, Kenji grabbed Josh Glassman by his triceps—still Popeye spinach cans, and the subject of much Facebook discussion afterward—and asked where the after-party was. He was only half-joking.

Psychologically speaking, Kenji carries a passport to pretty much anywhere now. He’s handsome, charming, a software engineer at an Amazon subsidiary; he radiates the kind of self-possession that earns instant respect. Josh seemed to intuit this. He said there was an after-party a few blocks away, at the home of another former football player. And when Kenji wavered, Josh wouldn’t take no for an answer. “I could see there was no going back,” Kenji explained the next morning, over brunch. “It was sort of like the dog who catches the car and doesn’t know what to do with it.”

The party was fine. For a while, Kenji wondered if he’d been brought along as a stunt guest—a suspicion hardly allayed by Josh’s announcement “I brought the valedictorian!” as they were descending the stairs to their host’s living room—though Kenji’s attendance was in the same spirit, really, just in reverse. (“This is the party I never got invited to in high school,” he told Josh at one point, who didn’t disagree.) At any rate, Kenji didn’t care. His curiosities were anthropological: He had no idea what it was like “to be a football player or a cheerleader, get out of high school, marry someone from your local area, and settle in the same area.” And his conclusion, by the end of the night, was: Nothing special. “It was just an ordinary party, one that might have been a little uncomfortable if we all hadn’t been a little drunk.”

You’d think Kenji’s underwhelmed reaction would have been reassuring. But another classmate of ours, also at that brunch, didn’t take it that way. Like Kenji, Larry was brilliant, musically gifted, and hidden behind awkward glasses during most of his adolescence; like Kenji, he too is attractive and successful today. He received a Tony nomination for the score of Legally Blonde, he has a new baby, he married a great woman who just happens to be his collaborator. Yet his reaction was visceral and instantaneous. “Literally?” he said. “Your saying this makes me feel I wish I’d been invited to that.”

“Well, right,” said Kenji. “Because that’s the way high school is.”

“And maybe the way life is, still, sometimes,” said Larry. “About wanting to be invited to things.” He’s now working on a musical adaptation of Heathers, the eighties classic that culminates, famously, in Christian Slater nearly blowing up a high school.

Not everyone feels the sustained, melancholic presence of a high-school shadow self. There are some people who simply put in their four years, graduate, and that’s that. But for most of us adults, the adolescent years occupy a privileged place in our memories, which to some degree is even quantifiable: Give a grown adult a series of random prompts and cues, and odds are he or she will recall a disproportionate number of memories from adolescence. This phenomenon even has a name—the “reminiscence bump”—and it’s been found over and over in large population samples, with most studies suggesting that memories from the ages of 15 to 25 are most vividly retained. (Which perhaps explains Ralph Keyes’s observation in his 1976 classic, Is There Life After High School?: “Somehow those three or four years can in retrospect feel like 30.”)

To most human beings, the significance of the adolescent years is pretty intuitive. Writers from Shakespeare to Salinger have done their most iconic work about them; and Hollywood, certainly, has long understood the operatic potential of proms, first dates, and the malfeasance of the cafeteria goon squad. “I feel like most of the stuff I draw on, even today, is based on stuff that happened back then,” says Paul Feig, the creator of Freaks and Geeks, which had about ten glorious minutes on NBC’s 1999–2000 lineup before the network canceled it. “Inside, I still feel like I’m 15 to 18 years old, and I feel like I still cope with losing control of the world around me in the same ways.” (By being funny, mainly.)

Yet there’s one class of professionals who seem, rather oddly, to have underrated the significance of those years, and it just happens to be the group that studies how we change over the course of our lives: developmental neuroscientists and psychologists. “I cannot emphasize enough the amount of skewing there is,” says Pat Levitt, the scientific director for the National Scientific Council on the Developing Child, “in terms of the number of studies that focus on the early years as opposed to adolescence. For years, we had almost a religious belief that all systems developed in the same way, which meant that what happened from zero to 3 really mattered, but whatever happened thereafter was merely tweaking.”

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