IN THE MYTHICAL TOWN OF LAKE Wobegon, as humorist Garrison Keillor tells it, all the women are strong, all the men good looking and all the children are above average. On the last point, Keillor didn't know how right he was. In a phenomenon overlooked even by scholars who study the nature and roots of intelligence, IQ scores throughout the developed world have soared dramatically since the tests were introduced in the early years of this century--27 points in Britain since 1942 and 24 points in the United States since 1918, for instance, with comparable gains throughout Western Europe, Canada, Japan, Israel, urban Brazil, China, Australia and New Zealand (graph). The rise is so sharp that it implies that the average schoolchild today is as bright as the near-geniuses of yesteryear. And not only in Lake Wobegon. "We now have data for 20 nations," James R. Flynn, a political philosopher at the University of Otago in New Zea- land who stumbled upon the phenomenon, told an IQ conference earlier this month. "And there is not a single exception to massive IQ gains."
But while it is easy to tabulate the IQ gains now known as the Flynn effect, explaining them is harder. Scientists agree that the gains are not a statistical artifact. The tests whose results Flynn analyzed have remained basically unchanged over the generations. And in some cases they have even been given to the same populationsevery military-age man in the Netherlands, for instancenot self-selected and therefore variable populations, as is the case with the SATs. "The increase in scores is real, it has been empirically demonstrated and it is widely accepted," says psychologist Wendy Williams of Yale University. But beyond that, agreement breaks down in a debate that recalls the controversy over IQ and race rekindled in 1994 by the book "The Bell Curve." For the implications are just as profound. If IQ measures innate intelligence, then there is a serious IQ generation gap: either a large fraction of today's children are gifted, with IQs of 130 or more, or "almost half of white Americans during World War I had IQs so low [below 76] that they lacked the intellectual capacity to understand the basic rules of baseball," says Flynn. But if, instead, the IQ gains are too large to represent true intelligence gains, as Flynn contends, "they throw a wrench into the theory that intelligence is measured by IQ."
To some veterans of the "Bell Curve" debate, the sharp rise in IQ bolsters the argument that intelligence must be determined more by nurture than by nature. Nature, in the form of the prevalence of "smart" genes in a population, does not change at anything like the speed with which IQ has risen, goes the argument. "The gene pool cannot change so much, so fast," says John Boli of Emory University. But the Flynn effect might in fact be "consistent with either a high or a low heritability of intelligence," argues psychologist Stephen Ceci of Cornell University. He draws an analogy to height. Stature is strongly heritable: short parents tend to have shorter children than tall parents do. Yet height, like IQ, has been rising for decades, not because tallness genes are suddenly more common but because of better nutrition. Similarly, intelligence may have a genetic basis yet still be subject to environmental influences. These influences would shape the form that intelligence takes in a particular society. They would also allow more children to attain their maximum intellectual potential--or keep them from doing so.
On a recent April weekend in Atlanta, psychologist Ulrich Neisser of Emory assembled 16 researchers to discuss these intriguing issues. Could rising living standards explain the IQ gain? Of the 20-odd-point rise, socioeconomic factors account for perhaps 5 points, Flynn calculates. Better schools? The greatest IQ gains have come on nonverbal intelligence tests--those that are heavy on mazes and puzzles. Yet these are the very tests that are designed to be free of such cultural influences as education. On tests of "acquired intelligence" (vocabulary or arithmetic or facts such as where turpentine comes from), which are expected to mirror acquired knowledge such as that from schooling, the gains are much smaller.
Might better nutrition and a more stimulating environment of museums and zoos, Legos and Transformers account for the IQ rise? Both can raise IQ scores, but only because they raise true intelligence by, say, giving the Legomaniac a better grasp of spatial relationships. And there is no evidence that real-world intelligence--an ability to learn faster or make creative leaps or do any of the other things that "intelligence" connotes--is rising at anything like the rate of IQ scores. (If it were, remember, the average American of 1918 couldn't have understood baseball.) Flynn calls this "the broken link" between IQ and intelligence.
At the Emory conference, Yale's Williams, an expert on the development of children's intelligence, pointed out that much of the IQ gain may simply reflect the greater familiarity that today's kids have with the sorts of questions posed on the tests. Taking her data from wherever she can find it, Williams has been collecting kids' cereal boxes and fast-food bags. Both are covered with mazes and puzzles remarkably similar to what IQ tests ask. "In the 1930s a kid may never have seen a maze before finding one on his IQ test," says Williams. "It seems clear that the tests are not measuring innate, immutable intelligence, but a type of practiced learning and familiarity with the test questions."
But part of the IQ gain may reflect something far more meaningful, Williams suggested. Several studies indicate that a more permissive parenting style gives children a greater facility with language. "If the child is leading the parent, rather than always being directed, language skills develop faster," says Williams. "And language is closely linked to overall cognitive capacity. So while test-taking practice and a culture awash in mazes and puzzles would raise IQ scores without increasing intelligence in any meaningful way, parenting style may produce a true increase in intelligence and also in IQ."
Of all the explanations offered for the Flynn effect, Flynn himself is most taken with the idea that every generation comes of age in a world starkly different from their parents'. "Technological development has been going on in all the Flynn-effect countries," points out psychologist Patricia Greenfield of UCLA. And in some places formal schooling was greatly expanded during the same period. Whatever schools teach, they rely on the basic structure of test questions and answers. "The test question is the most basic convention on an intelligence test," says Greenfield. Children who have not had formal schooling would be unfamiliar with this format and therefore might do worse on standard IQ tests for reasons having nothing to do with their innate intelligence. More recently, Greenfield argues, wave upon wave of other cultural forces has lapped onto children's mental shores. Radio and TV drove up basic vocabulary. Videogames like Tetris enhanced such abilities as assembling a puzzle, a common IQ-test question. Action-packed videogames typically demand navigation through a two-dimensional representation of a 3-D space; mental paper folding, a prominent feature of the Stanford-Binet IQ test, demands the same skill. The spread of these image-intense technologies, says Greenfield, could explain the "spurt [in IQ scores] in the U.S. between 1972 and 1989."
Even Charles Murray, coauthor of "The Bell Curve," concedes that the Flynn effect provides "indirect support" for the idea that differences in blacks' and whites' IQs could reflect environmental factors. "It cautions against taking these differences as etched in stone," he says.
Somewhere out there, potent environmental forces are creating IQ differences. Some may raise both genuine intelligence and IQ; some may raise only IQ. Some may operate within generations as well as between generations, inflating the IQ scores of one child and deflating another's. Yet despite these unknowns, we still use IQ scores to sort our children into stimulating classrooms or dull ones, into prestigious schools or mediocre ones. The debate over the Flynn effect makes it clear that we're still not quite sure what we're measuring.