In August of 2001, Mitch Prinstein, a psychology professor who had just been hired at Yale University, offered his first class at the school: a course he had developed about popularity among children and adolescents. When Prinstein arrived at the small classroom the school had assigned him in the center of campus, he was greeted with a crowd outside the lecture hall—one so large that he figured there’d been a fire-drill-mandated building evacuation. It took him a moment to realize that there was no fire; the students were all there for his class. By the time the enrollment for the course was official, 550 students—a tenth of the school’s undergraduate population—had signed up to learn about that thing that is, variously, an aspiration and a scourge and a mystery: popularity.

Was the class size simply the result of the nerdy and the nerd-adjacent wanting to learn more about the thing that had eluded them in their younger years? Not really, Prinstein argues. Their interest in popularity was more anthropological than that. The students “told me that although they had long since departed the playground and the school cafeteria, they never left the world where popularity matters,” Prinstein writes in his new book on that subject, Popular: The Power of Likability in a Status-Obsessed World. The undergrads, in their jobs and internships, had already seen the social dynamics of adolescence affecting people’s interactions in board rooms, in operating rooms, in the world. They saw popularity influencing the workings of juries. And of sports teams. Congressional interns saw popularity playing out in the way laws were written and the American government was run.

The phenomenon that was supposed to be nowhere—popularity as another childish thing, to be given up at the onset of adulthood—was, it turned out, everywhere. “In a very real manner,” Prinstein writes, “our experiences with popularity are always occupying our minds.” He adds: “We never really left high school at all.”

What makes Popular fascinating is not necessarily that central thesis, which will likely feel familiar to people far beyond Yale’s ivy-covered walls. It is, rather, the depth with which Prinstein explains the world in its perma-Mean Girls ways. Prinstein is now a professor at the University of North Carolina, Chapel Hill, and his book reads as a cheerful overview: an exploration of popularity as both a sociological phenomenon and a physiological one. Prinstein is a lively writer, and he illustrates his arguments with personal anecdotes (ask him about the time he tried to get an actual massage from a “massage parlor”—and how his own high school experience conditioned his response) and with evocative turns of phrase (our high school selves, he writes, are “deeply embedded in our souls forever”).

Prinstein also makes a strong case for everlasting adolescence: He cites study after study, conducted by himself and his grad students but mostly by other researchers, all suggesting the ways that popularity imprints itself on people’s lives, far beyond the teenage years, through both its presence and its absence. Popularity affects people’s ability to find success in their careers, regardless of their intelligence or their work ethic. It affects their ability to find fulfilling friendships and romantic relationships.

It also affects their health and longevity. In 2010, Julianne Holt-Lunstad, a psychologist at Brigham Young University, published the results of a meta-analysis she had conducted, combining data from 148 prior investigations into social connections. Those who had large networks of friends, she found, had a 50 percent increase in their chances of surviving to the end point of the study they were participating in. And those who had high-quality relationships, on top of that, had a 91 percent higher survival rate. Being unpopular, on the other hand, Holt-Lunstad’s findings suggested, increased subjects’ chances of death—more strongly, in fact, than did obesity, physical inactivity, or binge-drinking. (The only factor that seemed to be comparably hazardous to subjects’ longevity? Smoking.) Being rejected by one’s peers earlier in life, other studies have found, has also been one of the most consistent risk factors for depression, anxiety, substance abuse, and even criminal behavior.

There is, of course, more than one way to be popular. Prinstein breaks down his own treatment of popularity across two broad dimensions: status—the kind of popularity we tend to associate with high school, the stuff of being known and admired though not necessarily liked—and interpersonal likability. (Only about 35 precent of people who have high status, one study found, are also likable.) Likability is related to charm, to friendliness, to inquisitiveness—it’s the charisma that draws other people to you, largely independent of status or beauty or any of the other metrics that generally give people rank in American culture. It was likability that Holt-Lunstad focused on in her analysis—likability that can have such far-reaching physical effects and wellness outcomes.

But then there is status: the kind of popularity that operates according to hierarchies. The kind that confers admiration but not necessarily true esteem. The kind most commonly associated with, yes, high school. Status, too, Prinstein argues, can affect people’s brains and their bodies overall—in adolescence, and far beyond.

What happens in the teenage years, Prinstein suggests, is a kind of perfect storm, neurologically speaking: At the start of puberty, the brain grows more dramatically than at any other point in one’s life. Myelin, the fatty substance that coats the neurons and allows the brain to function efficiently, increases, affording a burst of neural activity. Those shifts, along with others, aid the brain’s adolescent transition from childish ways of thought (impulsive, relatively un-self-conscious) to adulthood’s more logical, ruminative, and other-oriented modes.  

The result: Newfound brain capacity collides with newfound self-consciousness. The adolescent brain is primed both to take in the world around it more than ever before, and to process that information with more self-awareness than ever before. Which is another way of saying that teenagers are particularly cognizant of identity—and another way, too, of explaining why, as Jennifer Senior put it in New York Magazine, “most American high schools are almost sadistically unhealthy places to send adolescents.” It’s a powder keg, emotionally, and popularity—or, more specifically, teens’ conception of popularity—is a fuse.

And its effects continue long after high school. Whether one, as an adolescent, was accepted or celebrated by others, whether one ranked high or low—the awareness of all that informs the brain’s biases, far into the future. It conditions someone, Prinstein argues, either to be suspicious of other people, or trusting. To assume friendliness, or conflict. (“We don’t see things as they are,” Anaïs Nin had it; “we see them as we are.”) Memories of what we were inform, still, what we become. Or, as Prinstein sums it up: “Our adult brains began to form to help us survive in the hallways of high school. The problem is, we left high school long ago—and our brains never got the memo.”

The other problem? We are, as a culture, extremely reluctant to talk about any of that. We congratulate ourselves for having moved beyond concerns about popularity, beyond such teenage superficialities—suspecting all the while that our adolescences lurk and linger, if only in spectral form. Popularity is in that way much like class in America: It divides people. It defines people. Yet we generally treat it as a relic of the past—as something that was, once, but that thankfully is no more.

Here, via a professor who has studied popularity and its effects, is a book that is frustrated with all the pretense. Popular, as its title suggests, wants us to talk about its subject—forthrightly and, perhaps more to the point, unabashedly. It wants us to question the power that popularity—status, in particular—exerts on our lives. It offers insights that are bolstered by research; it also, more broadly, gives the concept of popularity a specific language, and an insistent voice. Back in 2001, one-tenth of the undergrads at Yale signed up for a psychology class, and that was not (just) because they wanted social advice or an easy A. It was, it seems, because they wanted answers. The students seemed to recognize, intuitively, that adolescence would live on, in their own lives and the lives of their peers, shaping them—shaping all of us. They seemed to be seeking what their professor’s book now offers: an exploration of why, even in adulthood, it can be so hard to grow up.