For an academic researcher who first trained as a philosopher, then as a psychologist, Robyn Dawes was a practical fellow. He would tell a story from his time working in a psychiatric ward in the late 1950s. “There was a client who had this delusion, and the delusion was that he was growing breasts.” The man was locked in a secure ward while the psychiatrists pondered the reason for this fascinating delusion; they suspected that it was most likely the traumatic impact of the recent and shocking death of a parent.

Six weeks later, someone asked the man to take off his shirt. He had a genetic condition, not a delusion. “It was in fact true: he was growing breasts.”

It was a lesson to learn: even experts — no, especially experts — can become sidetracked by elaborate ideas, overlooking the simple and direct approach. No surprise, then, that Dawes would become fascinated by the research of Ted Sarbin and Paul Meehl, psychologists who had studied the surprising power of simple statistical predictions in areas such as clinical diagnoses or academic performance.