Flynn effect
Channel: 宇宙のすべての知識 プリンシピア
Date: 2018-12-21

Flynn effect, by Wikipedia https://en.wikipedia.org/wiki?curid=11773 / CC BY SA 3.0

Flynn effect

The Flynn effect is the substantial and long-sustained increase in both fluid and crystallized intelligence test scores that was measured in many parts of the world over the 20th century. When intelligence quotient (IQ) tests are initially standardized using a sample of test-takers, by convention the average of the test results is set to 100 and their standard deviation is set to 15 or 16 IQ points. When IQ tests are revised, they are again standardized using a new sample of test-takers, usually born more recently than the first. Again, the average result is set to 100. However, when the new test subjects take the older tests, in almost every case their average scores are significantly above 100.

Test score increases have been continuous and approximately linear from the earliest years of testing to the present. For the Raven's Progressive Matrices test, a study published in the year 2009 found that British children's average scores rose by 14 IQ points from 1942 to 2008. Similar gains have been observed in many other countries in which IQ testing has long been widely used, including other Western European countries, Japan, and South Korea.

There are numerous proposed explanations of the Flynn effect, as well as some skepticism about its implications. Similar improvements have been reported for other cognitions such as semantic and episodic memory. Research suggests that there is an ongoing reversed Flynn effect, i.e. a decline in IQ scores, in Norway, Denmark, Australia, Britain, the Netherlands, Sweden, Finland, France and German-speaking countries, a development which appears to have started in the 1990s.

The Flynn effect is named for James R. Flynn, who did much to document it and promote awareness of its implications. The term itself was coined by Richard Herrnstein and Charles Murray, authors of "The Bell Curve". Although the general term for the phenomenon - referring to no researcher in particular - continues to be "secular rise in IQ scores", many textbooks on psychology and IQ testing have now followed the lead of Herrnstein and Murray in calling the phenomenon the Flynn effect.

IQ tests are updated periodically. For example, the Wechsler Intelligence Scale for Children (WISC), originally developed in 1949, was updated in 1974, in 1991, 2003 and again in 2014. The revised versions are standardized based on the performance of test-takers in standardization samples. A standard score of IQ 100 is defined as the median performance of the standardization sample. Thus one way to see changes in norms over time is to conduct a study in which the same test-takers take both an old and new version of the same test. Doing so confirms IQ gains over time. Some IQ tests, for example tests used for military draftees in NATO countries in Europe, report raw scores, and those also confirm a trend of rising scores over time. The average rate of increase seems to be about three IQ points per decade in the United States, as scaled by the Wechsler tests. The increasing test performance over time appears on every major test, in every age range, at every ability level, and in every modern industrialized country, although not necessarily at the same rate as in the United States. The increase was continuous and roughly linear from the earliest days of testing to the mid 1990s. Though the effect is most associated with IQ increases, a similar effect has...