Last week, one of my college friends, who now manages vast sums at a hedge fund, visited me. He’s the most rational person I know, so I asked him how he would go about deciding whether to go to grad school in a discipline like English or comparative literature. He dealt immediately with the sample bias problem by turning toward statistics. His first step, he said, would be to ignore the stories of individual grad students, both good and bad. Their experiences are too variable and path-dependent, and their stories are too likely to assume an unwarranted weight in our minds. Instead, he said, he would focus on the “base rates”: that is, on the numbers that give you a broad statistical picture of outcomes from graduate school in the humanities. What percentage of graduate students end up with tenure? (About one in four.) How much more unhappy are graduate students than other people? (About fifty-four per cent of graduate students report feeling so depressed they have “a hard time functioning,” as opposed to ten per cent of the general population.) To make a rational decision, he told me, you have to see the big picture, because your experience is likely to be typical, rather than exceptional. “If you take a broader view of the profession,” he told me, “it seems like a terrible idea to go to graduate school.”Perhaps that’s the rational conclusion, but, if so, it’s beset on all sides by confounding little puzzles; they act like streams that divert and weaken the river of rational thought. Graduate school, for example, is a one-time-only offer. Very few people start doctoral programs later in life. If you pass it up, you pass it up forever. Given that, isn’t walking away actually the rash decision? (This kind of thinking is a subspecies of the habit of mind psychologists call loss aversion: once you have something, it’s very hard to give it up; if you get into grad school, it’s very hard not to go.) And then there’s the fact that graduate school, no matter how bad an idea it might be in the long term, is almost always fulfilling and worthwhile in the short term. As our conversation continued, my friend was struck by this. “How many people get paid to read what they want to read,” he asked, “and study what they want to study?” He paused. ”If I got into a really good program, I would probably go.”