The Better Angels of Our Nature — By Steven Pinker — Book Review - NYTimes.com →

The average I.Q. is, by definition, 100; but to achieve that result, raw test scores have to be standardized. If the average teenager today could go back in time and take an I.Q. test from 1910, he or she would have an I.Q. of 130, which would be better than 98 percent of those taking the test then. Nor is it easy to attribute this rise to improved education, because the aspects of the tests on which scores have risen most do not require a good vocabulary or even mathematical ability, but instead test powers of abstract reasoning.