If you think you’re so smart, then why don’t you know what intelligence is? Because no one does! Is intelligence a unitary, general factor — the psychometrician’s famed g — or is it more plural and fragmented? What role do genes play in determining IQ? The environment? If intelligence is in the genes, then why do IQ scores continue to rise generation after generation all over the world? Are we actually getting smarter, or are we just getting better at taking tests? While these questions may seem recondite and academic, they are in fact central to ongoing, extremely heated controversies pertaining to education, welfare, and immigration policy. Which is why we have assembled a stellar panel of intelligence experts to delve into the IQ conundrum.

Leading off this month is James R. Flynn, discoverer of the famed “Flynn effect” and author of the new book What Is Intelligence? Beyond the Flynn Effect. Commenting on Flynn’s rich essay we have Linda Gottfredson, co-director of the Delaware-Johns Hopkins Project for the Study of Intelligence and Society; Stephen J. Ceci,the Helen L. Carr Professor of Developmental Psychology at Cornell University, and Eric Turkheimer, professor of psychology at the University of Virginia.

Lead Essay

  • In this month’s lead essay, famed intelligence researcher James R. Flynn draws on his new book, What Is Intelligence? Beyond the Flynn Effect, to help answer some of the puzzles surrounding the controversial issue of IQ. Flynn, who first discovered that IQ scores were rising generation after generation, notes that this improvement has been more dramatic on some parts of IQ tests than on others, challenging ideas of a unified general intelligence or “g.” Flynn argues that the fact cognitive abilities do not develop together has important implications for education. Additionally, Flynn contends that the evidence for the co-determining reciprocal influence of brain and environment should lead us to set aside simple ideas about the primacy of nurture and nature in intelligence. Once we grasp that “the brain is much more like our muscles than we had thought,” we can do more to improve cognitive performance by doing more to exercise the brain.

Response Essays

  • Linda Gottfredson, co-director of the Delaware-Johns Hopkins Project for the Study of Intelligence and Society, defends the unity of general intelligence, or g, against Flynn’s attempt to “unravel g into its component parts” by charging that “his core argument rests on logical fallacies that profoundly misinterpret the evidence.”

  • University of Virginia psychologist Eric Turkheimer contests even James Flynn’s modest accommodation with the construct of g, or general intelligence. Turkheimer argues that the “fundamental intuition” of g is that “universal positive relations among mental tests compels a single dominant explanatory construct,” but that “the fundamental intuition is wrong.” According to Turkheimer, g is not “discovered,” but is simply posited as a convenience, like the Prime Meridian. g may be useful for some purposes, but a multidimensional explanation of ability may still be correct. “The trick is not to get hooked on any particular way of dividing up the pie,” Turkheimer writes, “because it is a short step from there to trying to find the Greenwich Meridian at the bottom of the North Atlantic.”

  • Stephen J. Ceci, the Helen L. Carr Professor of Developmental Psychology at Cornell University, explains why Flynn’s work has been so important. According to Ceci, the received wisdom about the nature and effects of g, or general intelligence, led “some to argue that inequality in the distribution of wealth, prestige, and educational attainment is, in part, a consequence of unequal distribution of the intellectual capacity needed for high levels of functioning.” However, Ceci says, “[Flynn] has shown beyond doubt that general intelligence fluctuates systematically over time and this cannot be due to our having better genes than our grandparents,” and he goes on to explore the puzzles raised by this discovery.

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