Book Reviews - Autumn 2007

Nurtural Intelligence

The discoverer of the Flynn effect claims that genes control IQ less than you’d expect

By Richard Restak | September 1, 2007


What Is Intelligence? Beyond the Flynn Effect, by James R. Flynn, Cambridge University Press, $22

During the past hundred years, an impressive increase in IQ scores has occurred in the world’s industrialized countries. In What Is Intelligence? James R. Flynn, the discoverer and chronicler of this phenomenon (dubbed the “Flynn Effect”), suggests that we should not facilely equate IQ gains with intelligence gains. He says that it’s necessary to “dissect ‘intelligence’” into its component parts: “solving mathematical problems, interpreting the great works of literature, finding on-the-spot solutions, assimilating the scientific worldview, critical acumen and wisdom.” When this dissection is carried out, several paradoxes emerge, which Flynn in this engaging book attempts to reconcile.

In the period from 1947 to 2002, Americans gained 24 points on testing for similarities (“In what ways are dogs and rabbits alike?”) but only four points on vocabulary and two points on arithmetic. This is explained, according to Flynn, by our ability to use our intelligence in new ways. “More formal schooling and the nature of our leisure activities have altered the balance between the abstract and the concrete.” As a consequence of this “liberation of the human mind,” which separates us from mindsets of our predecessors of only a century ago, we are “in the habit of reasoning beyond the concrete.”

Flynn’s most intriguing and controversial claim concerns the preponderant influence of the environment over genetic inheritance in determining intelligence. The direct effect of genes on IQ accounts for only 36 percent of IQ variance, Flynn tells us, with 64 percent resulting from the indirect effect of genes plus environmental differences uncorrelated with genes. Yet this cheeky claim would seem to be contradicted by the fact that identical twins separated at birth and raised apart end up with very similar IQs, presumably because of their identical genes. Not so, says Flynn, who buttresses his argument by drawing on an analogy from basketball.

If on the basis of their genetic inheritance, separated-twin pairs are tall, quick, and athletically inclined, both members are likely to be interested in basketball, practice assiduously, play better, and eventually attract the attention of basketball coaches capable of transforming them into world-class competitors. Other twin pairs, in contrast, endowed with shared genes that predispose them to be shorter and stodgier than average will display little aptitude or enthusiasm for playing basketball and will end up as spectators rather than as players.

“Genetic advantages that may have been quite modest at birth have a huge effect on eventual basketball skills by getting matched with better environments,” Flynn writes. He suggests a similar environmental influence on genetic inheritance in regard to IQ: Twins with even a slight genetic IQ advantage are more likely to be drawn toward learning, perform better during their primary and secondary education, and thereby gain acceptance into top-tier universities. In the process, their IQ levels are likely to increase even further.

According to Flynn, the environment will always be the principal determinant of whether or not a particular genetic predisposition gets to be fully expressed. “There is a strong tendency for a genetic advantage or disadvantage to get more and more matched to a corresponding environment,” he writes.

But if IQ can be increased by environmental conditions, then it must be possible— for Flynn’s hypothesis to be correct— for IQ scores to decrease in response to unfavorable environments. Flynn provides the experience of second-generation Chinese Americans as an example.

Chinese-American entrants to Berkeley in 1966 had an IQ threshold seven points below their Caucasian classmates. This held true whether the students were born in the United States or in China. Yet by 1980 55 percent of the Chinese members of the 1966 class occupied managerial, professional, or technical occupations compared to only 34 percent of their Caucasian classmates. Flynn attributes this unexpected result (in terms of their lower IQ scores) to a parentally instilled passion for intellectual achievement. He noted that “Chinese Americans are an ethnic group for whom high achievement preceded high IQ rather than the reverse.”

Not surprisingly Chinese Americans in the highly successful class of 1966 provided their own children with an even more enriched cognitive environment than they themselves had enjoyed. Their children, as a result, by age six had a mean IQ nine points above Caucasian students. But as the children matured further, a surprising finding emerged. By age 10 the IQ differential had fallen four points. By age 18 IQ had declined further to only a three-point advantage. The reason for this IQ drop? According to Flynn, “Much of their advantage was lost when school began to dilute parental influence.”

Flynn balances this criticism of our educational system with the hopeful note that even modest intellectual endowment can be overcome at any stage of life by an enriched cognitive environment buttressed by ambition and sustained, focused individual effort. When these components aren’t present, IQ levels fall.

“It might be that IQ drops three points because a larger number of affluent middle-class children prefer wandering around shopping malls to profiting from schooling. It might be that a larger number of children are raised in solo-parent homes and that such an environment lowers IQ by three points. Then the enhanced social problem would have caused the IQ loss and not the reverse.”

Will IQ gains continue in the 21st century? While Flynn sees no reason to believe that IQ gains in developed countries will “go on forever,” he doesn’t look upon this development as totally negative. “If IQ gains were to cease throughout the developed world during the 21st century, this could give the developing world a chance to catch up.”

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