Human IQ

Human intelligence is based on the volume of gray matter tissue in certain parts of the brain.

A comprehensive structural brain-scan study conducted by researchers at The University of California, Irvine, College of Medicine has found that general human intelligence appears to be based on the volume of gray matter tissue in certain parts of the brain.

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The study led by Dr. Richard Haier and his colleagues at UCI and at the University of New Mexico also discovered that because these parts related to intelligence are located throughout the brain, a single "intelligence center," such as the frontal lobe, is unlikely.

The researchers used MRI to obtain structural images of the brain in 47 normal adults who also took standard intelligence quotient tests. They used a technique called voxel-based morphometry to determine gray matter volume throughout the brain which was correlated to IQ scores.

"This may be why one person is quite good at mathematics and not so good at spelling, and another person, with the same IQ, has the opposite pattern of abilities," Haier said.

"There is a constant cascade of information being processed in the entire brain, but intelligence seems related to an efficient use of relatively few structures, where the more gray matter the better. In addition, these structures that are important for intelligence are also implicated in memory, attention and language," he added.

The findings also suggest that in middle age, more of the frontal and parietal lobes are related to IQ while in younger adults its less of frontal and more temporal areas.