Flynn Effect - The Rise in IQ

The Rise in IQ

IQ tests are updated periodically. For example, the Wechsler Intelligence Scale for Children (WISC), originally developed in 1949, was updated in 1974, in 1991, and again in 2003. The revised versions are standardized to 100 using new standardization samples. In ordinary use IQ tests are scored with respect to those standardization samples. The only way to compare the difficulty of two versions of a test is to conduct a study in which the same subjects take both versions. Doing so confirms IQ gains over time. The average rate of increase seems to be about three IQ points per decade in the US on tests such as the WISC. The increasing raw scores appear on every major test, in every age range and in every modern industrialized country although not necessarily at the same rate as in the US using the WISC. The increase has been continuous and roughly linear from the earliest days of testing to the present. Though the effect is most associated with IQ increases, a similar effect has been found with increases of semantic and episodic memory.

Ulric Neisser estimates that using the IQ values of today the average IQ of the US in 1932, according to the first Stanford–Binet Intelligence Scales standardization sample, was 80. Neisser states that "Hardly any of them would have scored 'very superior,' but nearly one-quarter would have appeared to be 'deficient.'" He also writes that "Test scores are certainly going up all over the world, but whether intelligence itself has risen remains controversial."

Raven (2000) found that, as Flynn suggested, data interpreted as showing a decrease in many abilities with increasing age must be re-interpreted as showing that there has been a dramatic increase of these abilities with date of birth. On many tests this occurs at all levels of ability.

Some studies have found the gains of the Flynn effect to be particularly concentrated at the lower end of the distribution. Teasdale and Owen (1989), for example, found the effect primarily reduced the number of low-end scores, resulting in an increased number of moderately high scores, with no increase in very high scores. In another study, two large samples of Spanish children were assessed with a 30-year gap. Comparison of the IQ distributions indicated that the mean IQ-scores on the test had increased by 9.7 points (the Flynn effect), the gains were concentrated in the lower half of the distribution and negligible in the top half, and the gains gradually decreased as the IQ of the individuals increased. Some studies have found a reverse Flynn effect with declining scores for those with high IQ.

Flynn originally took the extreme position that the very large increase indicates that IQ tests do not measure intelligence but only a minor sort of "abstract problem-solving ability" with little practical significance. He argued that if IQ gains do reflect intelligence increases, there would have been consequent changes of our society that have not been observed (a presumed non-occurrence of a "cultural renaissance"). Flynn has later changed his arguments as noted in the next section.