IQ tests aren't perfect, but they can be useful. If a boy doing badly in class does really well on one, it is worth investigating whether he is being bullied at school or having problems at home. The tests also roughly predict who will succeed at college, though factors like motivation and self-control are at least as important.

Advanced nations like the U.S. have experienced massive IQ gains over time (a phenomenon that I first noted in a 1984 study and is now known as the...