From Smart Money May 9, 2011 By JACK HOUGH
If this prose fails to sparkle, I’ll blame my cold. An adult male’s brain consumes 23% of his metabolic budget, biologists say, and viruses, bacteria and parasites can leave it temporarily short-changed.
The matter is more serious among newborns, whose rapidly developing brains demand 87% of their energy, declining to 44% by age five. A cold will do no lasting damage. A tapeworm or amoeba might.
New research on how disease affects intelligence might solve a global mystery and change the way countries, including the U.S., spend money on their poor.
A controversial 2002 book titled “IQ and the Wealth of Nations” gathered existing data on IQs to map them by country. North American and Europe looked good. Sub-Saharan Africa did not. Asia shined. Critics cried racism; there’s a long history of intelligence research that blurs the divide between bigotry and investigation. In 2007, research by James Flynn published in “What is Intelligence” proved race-based arguments lacking. IQs the world over have been climbing for half a century, and they tend to jump quickly in poor countries that experience a spasm of economic growth–a phenomenon now called the Flynn Effect.
Whatever the fix is for regional IQ deficits, it must be economic. Researchers have looked at nutrition, income, school enrollment, farm employment, low birth weight and more, and found all of them to be correlated with IQ, although in some cases, it’s not clear which is the cause and which is the effect.
Disease rates trump all of these variables, explaining 67% of worldwide variation in intelligence, found Christopher Eppig of the University of New Mexico in a study published last year by the Royal Society in its biology journal. For a follow-up study published in the March-April issue of Intelligence, Eppig focused his “parasitic stress hypothesis” on the U.S., where average IQs range from 104 in New England to 94 in the Deep South. The result was much the same. A hodgepodge of diseases beat out wealth, differences in education and other variables to predict intelligence.
That doesn’t make schools a less-worthy destination for taxpayer cash, or course. “Anything humans do that affects parasite stress will indirectly affect IQ,” says Eppig. Even better than using parasite stress alone to predict intelligence, he says, is to add to it factors like wealth, education and climate.
This last variable, climate, is both powerful and inevitable. Warm, swampy climates favor the survival of infectious organisms. But the research suggests some cheap ways the world can buy more intelligence. Sanitation and clean water are surely among them in the U.S. and Africa–and in Africa in particular, mosquito nets and vaccines. Eppig suspects diarrheal diseases, tuberculosis, intestinal worms and malaria are big IQ drains, but says the next step in his research might be to study the links between intelligence and individual diseases to know for sure.
If disease helps explain the Flynn Effect, it might also make sense of a movie and television stereotype–the science whiz puffing on his inhaler or sneezing at pollen. Asthma and allergies have been linked with young immune systems growing rowdy from having too few diseases to fight. Regions that effectively banish diseases might thus end up smarter for it–but also frailer.