Sexes Get Smarts From Different Brain Areas

Intelligence may be more of a gray matter for men and a white matter for women, according to a new study.

Researchers found major differences in the amount of gray and white matter in the brains of men and women of the same intelligence, suggesting that men and women may derive their intelligence in different ways.

Researchers say white and gray matter are both necessary for general intelligence, but they perform different functions. Gray matter (search) represents information processing centers in the brain, and white matter (search) represents the network or connections between those processing centers.

The study confirms sex differences in human brains (search), with women having more gray matter than white matter. However, the study also showed that in areas related to intelligence men had much more gray matter, which is typically needed for isolated tasks, such as doing a math problem. Women, on the other hand, had much more white matter, which is necessary for integrating information.

“These findings suggest that human evolution has created two different types of brains designed for equally intelligent behavior,” says researcher Richard Haier, professor of psychology at the University of California, Irvine, in a news release. “In addition, by pinpointing these gender-based intelligence areas, the study has the potential to aid research on dementia and other cognitive impairment diseases in the brain.”

The results appear in the online edition of the journal Neuroimage.

Brain Differences May Not Matter to Intelligence

In the study, researchers studied brain scans of men and women who had identical IQ (intelligence quotient, a measure of intelligence) scores.

Overall, the results showed that men had approximately 6.5 times the amount of gray matter in areas related to general intelligence than women. Meanwhile, women had nearly 10 times the amount of white matter in areas related to intelligence than men.

They say the findings may help explain why men tend to excel at tasks that require more local processing, such as mathematics, while women tend to excel at integrating information, a skill used in language.

The study also showed differences in brain regions between men and women related to intelligence. In particular, 84 percent of gray matter regions and 86 percent of white matter regions involved in women’s intelligence were found in their frontal lobes or front portion of the brain compared with 45 percent and 0 percent for men, respectively. Instead, regions throughout the left side of the brain seems to drive male intelligence.

Researchers say this finding confirms previous studies that have shown that frontal brain injuries can be more damaging to intelligence and mental performance in women than in men.

But despite these differences in brain pathways and activity centers, researchers say men and women perform equally on broad measures of intelligence, such as IQ tests.

By Jennifer Warner, reviewed by Brunilda Nazario, MD

SOURCES: Haier, R. Neuroimage, Jan. 16, 2005 online edition. News release, University of California, Irvine.