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 “Flynn Effect”). From the early 1900s to today, Americans have gained three IQ points per decade on both the Stanford-Binet Intelligence Scales and the Wechsler Intelligence Scales. These tests have been around since the early 20th century in some form, though they have been updated over time. Another test, Raven’s Progressive Matrices, was invented in 1938, but there are scores for people whose birth dates go back to 1872. It shows gains of five points per decade.
In 1910, scored against today’s norms, our ancestors would have had an average IQ of 70 (or 50 if we tested with Raven’s). By comparison, our mean IQ today is 130 to 150, depending on the test. Are we geniuses or were they just dense?
These alternatives sparked a wave of skepticism about IQ. How could we claim that the tests were valid when they implied such nonsense? Our ancestors weren’t dumb compared with us, of course. They had the same practical intelligence and ability to deal with the everyday world that we do. Where we differ from them is more fundamental: Rising IQ scores show how the modern world, particularly education, has changed the human mind itself and set us apart from our ancestors. They lived in a much simpler world, and most had no formal schooling beyond the sixth grade.
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