The most popular course in the history of Yale University was offered in the fall of 2017—PSYCH 157: Psychology and the Good Life. Nearly one-fourth of Yale undergraduates registered for it. Laurie Santos, the psychology professor who teaches the course, says that she "tries to teach students how to lead a happier, more satisfying life." No wonder the course has caught on—a 2013 report by the Yale College Council found that "more than half of undergraduates sought mental health care from the university" while enrolled.

One of Santos' principle lessons is that the things Yale undergraduates most associate with achieving happiness—a high grade, a prestigious internship, a good-paying job—do not increase happiness at all. "Scientists didn't realize this in the same way 10 or so years ago," Santos says. "Our intuitions about what will make us happy, like winning the lottery and getting a good grade, are totally wrong."