1. The cops have put Tony, Uncle Junior, Silvio, Paulie Walnuts and Livia in a lineup, standing in spots numbered 1 through 6 from left to right. There's one empty space. Livia is the third person from the left. Tony is to Uncle Junior's immediate left. If Paulie Walnuts stands in space 6 with no one beside him, where is Silvio?
2. Seven years ago Jack was three times as old as Jill. If Jack is now five years older than Jill, how old is he?
(a) 12-1/2 (b) 13 (c) 13-1/2 (d) 14-1/2 (e) 15
While generations of schoolchildren, military recruits, job applicants and Mensa wanna-bes have wrestled with IQ questions like these, some smart scientists who study intelligence have been stumped by an even more exasperating puzzle: why have IQ scores been rising? And not rising a little, by a point here and there, but soaring--27 points in Britain since 1942, 24 points in the United States since 1918, 22 points in Argentina since 1964, with comparable gains throughout Western Europe, Canada, Japan, China, Israel, Australia and New Zealand. The rise is so sharp that the average child today is as bright as the near genius of yesteryear. "This shatters our belief about the rigidity of IQ," says psychologist Ulrich Neisser of Cornell University. "It's powerful evidence that you can indeed change it."
There's just one little problem. Leaving aside for now the very real question of whether IQ is truly a proxy for intelligence, scientists can't explain what has made IQ scores take off. Neither nature nor nurture--genes nor environment--answers the question, for different reasons. A slew of data, from twin studies to adoption research, suggests that genes account for some 75 percent of the difference between individuals' IQs by late adolescence. That leaves precious little room for environment to play a role. But explaining the IQ rise by "smarter" genes makes no sense, because the genes in a population do not change quickly enough to explain the IQ chasm between the Greatest Generation and Gen Y. That would seem to make environment the leading suspect, but then you're back to that 800-pound gorilla in the corner: psychologists who study intelligence mostly agree that hereditary factors explain the lion's share of IQ differences.
"It's been a paradox," says William Dickens of the Brookings Institution. "The high heritability of IQ suggests that environment is feeble, but IQ gains over time suggest that environment is overwhelmingly powerful." To untangle the mystery, Dickens teamed up with James Flynn, who in 1987 discovered the IQ rise, now called the Flynn effect. In a study being published this week in Psychological Review, the duo offer an explanation that not only might resolve the paradox but may also shed light on the forces that shape intelligence. "People's IQs are affected by both environment and genes, but... their environments are matched to their IQs," the researchers conclude. In other words, genes do indeed have an important effect: they cause people to seek out certain environments, certain life experiences. If you have a biological edge in intelligence, for instance, you will likely enjoy school, books, puzzles, asking questions and thinking abstractly. All of which will tend to amplify your innate brainpower. "Higher IQ leads one into better environments, causing still higher IQ," say Dickens and Flynn. Thanks to that multiplier effect, you will likely study even more, haunt the library, pester adults with questions and choose bright peers as friends, boosting your intelligence yet again.
The dance between genes and environment starts young. A naturally verbal toddler will likely elicit hour after hour of reading from her parents, for instance. That will amplify her cognitive gifts even if her "verbal IQ genes" are only the slightest bit smarter than other kids'. "A modest genetic advantage turns into a huge performance advantage," says Dickens.
But if you start out with a slight deficit in IQ, you may get frustrated by reading and cogitating, stumble in school and grow to hate learning, reinforcing your geneticbent. A modest initial difference again gets pumped up.
As far as scientists can tell, experiences that boost the intelligence of someone born with an IQ edge have just about the same positive effect on people of average intelligence. In other words, whether you seek out an IQ-boosting environment or whether it finds you makes no difference. In either case, experiences and the social and technological surround should work their magic. This effect may account for the IQ rise over the decades. Crowded computer screens, videogames, even fast-foodery place mats and cereal boxes (full of hidden-word games and mazes) might be training young brains in the pattern analysis that IQ tests assess. Smaller families, which offer children more individual attention and indulge their passion for "why's," might boost a generation's IQ. Jobs that demand more brainpower, more free time (at least some of which is spent reading, doing crossword puzzles, traveling to stimulating places) and technological gadgets that challenge our gray matter could also lift all IQ boats. "Leisure and even ordinary conversation are more cognitively demanding today," says Flynn, an American expatriate teaching at the University of Otago in New Zealand. Teen multitaskers--simultaneously IM'ing, downloading and channel-surfing--may be exercising their memory (a component of intelligence) and training their attention to switch focus in the blink of an eye.
All these expressions of social and technological change have one key characteristic: they are enduring. In contrast, a temporary IQ-boosting change--like an early-childhood enrichment program, or parents who provide intellectual stimulation only in their children's prekindergarten years--can have the staying power of a mayfly. "The kids get this great [intervention], but then they go back to their old environment," says psychologist Robert Sternberg of Yale University. "Of course they usually regress." Even 18 years of parental influence fades. All parents can do is hope that the love of learning they imbue in their child takes hold, causing him to seek out the experiences and people that will keep stimulating his intelligence.
Those who believe in the power of genes and those who believe in the power of environment, says Dickens, "are both right." Genes working through environment account for the lion's share of individual differences in IQ, but only because genes lead you to certain life experiences, which collectively form your "environment." It is that environment which directly fosters IQ differences. "People often have a fatalistic sense that IQ is fixed," says psychologist John Gabrieli of Stanford University. "The Flynn effect shows that it can be enhanced by good environment. It doesn't have to be some fixed capacity you're born with."
Oh: Silvio stands in space 4. And Jack is 14-1/2.