Before he arrived at U.T. in the winter of 2012, Yeager worked as a graduate student in the psychology department at Stanford, during an era when that department had become a hotbed of new thinking on the psychology of education. Leading researchers like Carol Dweck, Claude Steele and Hazel Markus were using experimental methods to delve into the experience of students from early childhood all the way through college. To the extent that the Stanford researchers shared a unifying vision, it was the belief that students were often blocked from living up to their potential by the presence of certain fears and anxieties and doubts about their ability. These feelings were especially virulent at moments of educational transition — like the freshman year of high school or the freshman year of college. And they seemed to be particularly debilitating among members of groups that felt themselves to be under some special threat or scrutiny: women in engineering programs, first-generation college students, African-Americans in the Ivy League.

The negative thoughts took different forms in each individual, of course, but they mostly gathered around two ideas. One set of thoughts was about belonging. Students in transition often experienced profound doubts about whether they really belonged — or could ever belong — in their new institution. The other was connected to ability. Many students believed in what Carol Dweck had named an entity theory of intelligence — that intelligence was a fixed quality that was impossible to improve through practice or study. And so when they experienced cues that might suggest that they weren’t smart or academically able — a bad grade on a test, for instance — they would often interpret those as a sign that they could never succeed. Doubts about belonging and doubts about ability often fed on each other, and together they created a sense of helplessness. That helplessness dissuaded students from taking any steps to change things. Why study if I can’t get smarter? Why go out and meet new friends if no one will want to talk to me anyway? Before long, the nagging doubts became self-fulfilling prophecies.

When Yeager arrived at Stanford in 2006, many of the researchers there had begun to move beyond trying to understand this phenomenon to trying to counteract it. In a series of experiments, they found that certain targeted messages, delivered to students in the right way at the right time, seemed to overcome the doubts about belonging and ability that were undermining the students’ academic potential.

Yeager began working with a professor of social psychology named Greg Walton, who had identified principles that seemed to govern which messages, and which methods of delivering those messages, were most persuasive to students. For instance, messages worked better if they appealed to social norms; when college students are informed that most students don’t take part in binge drinking, they’re less likely to binge-drink themselves. Messages were also more effective if they were delivered in a way that allowed the recipients a sense of autonomy. If you march all the high-school juniors into the auditorium and force them to watch a play about tolerance and inclusion, they’re less likely to take the message to heart than if they feel as if they are independently seeking it out. And positive messages are more effectively absorbed when they are experienced through what Walton called “self-persuasion”: if students watch a video or read an essay with a particular message and then write their own essay or make their own video to persuade future students, they internalize the message more deeply.

In one experiment after another, Yeager and Walton’s methods produced remarkable results. At an elite Northeastern college, Walton, along with another Stanford researcher named Geoffrey Cohen, conducted an experiment in which first-year students read brief essays by upperclassmen recalling their own experiences as freshmen. The upperclassmen conveyed in their own words a simple message about belonging: “When I got here, I thought I was the only one who felt left out. But then I found out that everyone feels that way at first, and everyone gets over it. I got over it, too.” After reading the essays, the students in the experiment then wrote their own essays and made videos for future students, echoing the same message. The whole intervention took no more than an hour. It had no apparent effect on the white students who took part in the experiment. But it had a transformative effect on the college careers of the African-American students in the study: Compared with a control group, the experiment tripled the percentage of black students who earned G.P.A.s in the top quarter of their class, and it cut in half the black-white achievement gap in G.P.A. It even had an impact on the students’ health — the black students who received the belonging message had significantly fewer doctor visits three years after the intervention.

Next, Yeager did an experiment with 600 students just entering ninth grade at three high schools in Northern California. The intervention was 25 minutes long; students sat at a terminal in the school computer lab and read scientific articles and testimonials from older students with another simple message: People change. If someone is being mean to you or excluding you, the essays explained, it was most likely a temporary thing; it wasn’t because of any permanent trait in him or you. Yeager chose ninth grade because it is well known as a particularly bad time for the onset of depression — generally, depression rates double over the transition to high school. Indeed, among the control group in Yeager’s experiment, symptoms of depression rose by 39 percent during that school year. Among the group who had received the message that people change, though, there was no significant increase in depressive symptoms. The intervention didn’t cure anyone’s depression, in other words, but it did stop the appearance of depressive symptoms during a traditionally depressive period. And it did so in just 25 minutes of treatment.

After the depression study, Yeager, Walton and two other researchers did an experiment with community-college students who were enrolled in remedial or “developmental” math classes. Education advocates have identified remedial math in community college as a particularly devastating obstacle to the college hopes of many students, especially low-income students, who disproportionately attend community college. The statistics are daunting: About two-thirds of all community-college students are placed into one or more remedial math classes, and unless they pass those classes, they can’t graduate. More than two-thirds of them don’t pass; instead, they often drop out of college altogether.