And here’s the upsetting punch line: intelligence seems to make things worse. The scientists gave the students four measures of “cognitive sophistication.” As they report in the paper, all four of the measures showed positive correlations, “indicating that more cognitively sophisticated participants showed larger bias blind spots.” This trend held for many of the specific biases, indicating that smarter people (at least as measured by S.A.T. scores) and those more likely to engage in deliberation were slightly more vulnerable to common mental mistakes. Education also isn’t a savior; as Kahneman and Shane Frederick first noted many years ago, more than fifty per cent of students at Harvard, Princeton, and M.I.T. gave the incorrect answer to the bat-and-ball question.

What explains this result? One provocative hypothesis is that the bias blind spot arises because of a mismatch between how we evaluate others and how we evaluate ourselves. When considering the irrational choices of a stranger, for instance, we are forced to rely on behavioral information; we see their biases from the outside, which allows us to glimpse their systematic thinking errors. However, when assessing our own bad choices, we tend to engage in elaborate introspection. We scrutinize our motivations and search for relevant reasons; we lament our mistakes to therapists and ruminate on the beliefs that led us astray.