IQ's Generation Gap: Is Intelligence Reaching New Heights, or Is Something Amiss with the Tests That Measure It?
Bower, Bruce, Science News
IQ's Generation Gap
In the Netherlands, IQ points are blooming faster than tulips. In fact, according to an analysis by political scientist James R. Flynn, the average IQ of Dutch draftees increased by 20 points in the span of one generation, from 1952 to 1982.
And the IQ increase is not just a Dutch treat. Flynn, of the University of Otago in Dunedin, New Zealand, collected data from investigators around the world whose work is largely unknown to one another. He found single-generation IQ gains ranging from 5 to 25 points in 13 other developed nations. Among these are the United States, Japan, France, Belgium, Norway, New Zealand and Canada.
If IQ tests really tap into a fundamental aspect of intelligence, says Flynn, the implications of this trend are staggering. In the Netherlands, for instance, the 30-year increase implies that about one-quarter of the population qualifies as mentally gifted, with IQs of at least 130. Those with IQs over 150 have increased almost 60-fold since 1952--a jump that translates into 300,000 potential geniuses. "The result should be a cultural renaissance too great to be overlooked,' maintains Flynn.
There are, of course, no indications of such a dramatic leap forward in thought. Instead, as Flynn explains in an upcoming book (Measurement, Realism and Objectivity, John Forge, Ed., Reidel Publishing Co., 1987) and in the March PSYCHOLOGICAL BULLETIN, it appears that IQ tests measure not intelligence but some form of abstract problem-solving ability that has little ultimate effect on intelligence. IQ estimates of this ability have been shown to predict real-world achievements, such as job status and performance, fairly well for siblings raised in the same family or people of the same generation who share the same cultural environment. But Flynn contends that intelligence test scores cannot bridge the cultural distance that separates generations in modern industrial societies, or, for that matter, Americans from Japanese and American whites from American blacks.
A time span of 30 years is hardly long enough for genetic changes to boost IQ scores, he notes. Furthermore, the Dutch data surprisingly reveal that three environmental factors often invoked to explain improved performance on IQ tests-- more education, higher socioeconomic standing and experience in test taking-- account for only about 5 of the 20 IQ points gained. Flynn concludes that most of the increase must be due to currently unknown environmental influences.
Ironically, the greatest IQ gains occurred on "culture-fair' tests that present subjects with novel problems requiring no prior experience. One such test consists of geometric patterns, each containing a gap; the correct missing piece must be chosen from six alternatives. Other tests, such as the Stanford-Binet and Wechsler that are given in the United States, have similar measures of problemsolving but also contain items on general information, vocabulary and mathematics.
"No experience required' intelligence tests have been heralded by some researchers, most notably psychologist Arthur R. Jensen of the University of California at Berkeley, as the best measure of general mental ability, or g for short. This is a statistical calculation of what Flynn calls "the significant tendency of those who do well on one test to excel on all mental tests,' from vocabulary to number series, logical reasoning to coding digits. According to Jensen, although the true nature of g is far from clear, it is the best known predictor of success in school and college, in the armed forces and in business and industry. A substantial portion of g, in his view, is determined genetically.
Since large single-generation jumps in IQ and g have not been accompanied by proportional real-world achievements, Flynn says that Jensen's theory, grounded in the work of British psychologist Charles Spearman at the turn of the century, needs to be revised. …