Biomedical neuroengineers have recently noticed that when visitors to the Prado in Madrid pause in front of Bosch’s triptych The Garden of Earthly Delights they make short work of paradise and instead opt for perdition. The panel on the left depicts a blithe, bucolic Eden, where the average museum-goer spends only 16 seconds. The central section, which shows a polymorphous orgy that is about as shocking as a weekend of suburban wife-swapping in the 1960s, detains viewers for 26 seconds. But when reaching the far end, they spend 33 seconds exploring a perverse inferno in which people copulate with birds,...