When I was eight or nine, I played a game that I invented with my friends. On index cards, alphabetized in a recipe box, were written descriptions of fictional ailments, each with a ridiculous name and an equally ridiculous cure. In order to diagnose what illness my playmates suffered from, I would ask them a list of questions including, “Do you worry about being late?” “Do you have time to do what you like?” and “Are your shoes or boots uncomfortable?” Then I would just watch them for telltale symptoms, like moving more than three times during the interview. Based ...