On a subway train not long ago, I had the familiar, unsettling experience of standing behind a fellow-passenger and watching everything that she was doing on her phone. It was a crowded car, rush hour, with the dim but unwarm lighting of the oldest New York City trains. The stranger’s phone was bright, and as I looked on she scrolled through a waterfall of videos that other people had filmed in their homes. She watched one for four or five seconds, then dispatched it by twitching her thumb. She flicked to a text message, did nothing with it, and flipped back. The figures on her screen, dressed carefully and mugging at the camera like mimes, seemed desperate for something that she could not provide: her sustained attention. I felt mortified, not least because I saw on both sides of the screen symptoms I recognized too clearly in myself.

For years, we have heard a litany of reasons why our capacity to pay attention is disturbingly on the wane. Technology—the buzzing, blinking pageant on our screens and in our pockets—hounds us. Modern life, forever quicker and more scattered, drives concentration away. For just as long, concerns of this variety could be put aside. Television was described as a force against attention even in the nineteen-forties. A lot of focussed, worthwhile work has taken place since then.

But alarms of late have grown more urgent. Last year, the Organization for Economic Cooperation and Development reported a huge ten-year decline in reading, math, and science performance among fifteen-year-olds globally, a third of whom cited digital distraction as an issue. Clinical presentations of attention problems have climbed (a recent study of data from the medical-software company Epic found an over-all tripling of A.D.H.D. diagnoses between 2010 and 2022, with the steepest uptick among elementary-school-age children), and college students increasingly struggle to get through books, according to their teachers, many of whom confess to feeling the same way. Film pacing has accelerated, with the average length of a shot decreasing; in music, the mean length of top-performing pop songs declined by more than a minute between 1990 and 2020. A study conducted in 2004 by the psychologist Gloria Mark found that participants kept their attention on a single screen for an average of two and a half minutes before turning it elsewhere. These days, she writes, people can pay attention to one screen for an average of only forty-seven seconds.

“Attention as a category isn’t that salient for younger folks,” Jac Mullen, a writer and a high-school teacher in New Haven, told me recently. “It takes a lot to show that how you pay attention affects the outcome—that if you focus your attention on one thing, rather than dispersing it across many things, the one thing you think is hard will become easier—but that’s a level of instruction I often find myself giving.” It’s not the students’ fault, he thinks; multitasking and its euphemism, “time management,” have become goals across the pedagogic field. The SAT was redesigned this spring to be forty-five minutes shorter, with many reading-comprehension passages trimmed to two or three sentences. Some Ivy League professors report being counselled to switch up what they’re doing every ten minutes or so to avoid falling behind their students’ churn. What appears at first to be a crisis of attention may be a narrowing of the way we interpret its value: an emergency about where—and with what goal—we look.

“In many ways, it’s the oldest question in advertising: how to get attention,” an executive named Joanne Leong told me one afternoon, in a conference room on the thirteenth floor of the midtown office of the Dentsu agency. We were speaking about a new attention market. Slides were projected on the wall, and bits of conversation rattled like half-melted ice cubes in the corridor outside. For decades, what was going on between an advertisement and its viewers was unclear: there was no consensus about what attention was or how to quantify it. “The difference now is that there’s better tech to measure it,” Leong said.

Dentsu is one of the world’s leading advertising agencies, running accounts for Heineken, Hilton, Kraft Heinz, Microsoft, Subway, and other global corporations. In 2019, the firm began using digital technology to gather data that showed not only how many people attended to its ads but in what ways they did—information that could be applied to derive a quantitative unit of attention value. In 1997, the technology pundit Michael Goldhaber had envisaged a world in which attention supplanted money as a dominant currency. (“If you have enough attention, you can get anything you want,” he lamented.) Since then, advertising has caught up with the trade.

“Six years ago, the question was around ‘Can this usefully be measured?’ ” Leong said. Now it’s a circus. “There are companies that use eye tracking. There are companies that do facial coding”—reading emotions through micro-expressions. “It’s no longer a matter of convincing clients that this is something they should lean into—it’s how.”

There is a long-standing, widespread belief that attention carries value. In English, attention is something that we “pay.” In Spanish, it is “lent.” The Swiss literary scholar Yves Citton, whose study of the digital age, “The Ecology of Attention,” argues against reducing attention to economic terms, suggested to me that it was traditionally considered valuable because it was capable of bestowing value. “By paying attention to something as if it’s interesting, you make it interesting. By evaluating it, you valorize it,” he said. To treat it as a mere market currency, he thought, was to undersell what it could do.