Has There Been a ‘Massive’ Rise in IQ Levels in the West? Evidence from Scottish Children

Abstract

A ‘massive’ 18-point (1.2σ) increase in scores (from 1950 to 1980) has been reported on culture-reduced tests of IQ in fourteen of the world’s advanced economies. Here we examine the performance of representative samples of Scottish children in 1961 and 1983/4 on items from six scales of the Wechsler IQ test. We estimate that the rate of the gain in IQ for Scottish children over these 22.5 years did not exceed 2.5 IQ points (0.1 7 σ ) per generation. This result may diverge from the reported international trend because the ‘massive’ IQ-type gains found in other countries reflect the reliance of other investigators on multiple-choice, culture-reduced tests that tend to reward intelligent guessing and to penalise scrupulosity.