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Over the years, people have ____1____ a lot of theories to explain why intelligence differs, from person to person and even around the world. Health, wealth, schooling, nutrition, even climate have all come up. Now, researchers at the University of New Mexico suggest that parasites might play a role. They find that the prevalence of infectious diseases can be a powerful predictor of regional smarts. Their work appears in the Proceedings of the Royal Society.
It takes a lot of energy to build and operate a human brain. This ____2____ organ commands 87 percent of the body's metabolic budget in infants, and about 25 percent in adults. So things that ____3____ our energy are likely to hinder our intellectual growth. That's why malnourishment's not good for the mind.
But what about parasites? Fighting off nasty bugs can ____4____ you. So the scientists got to wondering whether excessive infections might ____5____ impaired cognitive development. Looking at IQs from around the world, they found that high levels of infectious disease ____6____ lower average national intelligence.
Although the authors have not demonstrated cause-and-effect, it's nice to think that ____7____ parasites could bring up our IQs.