Men and women appear to employ different brain organization to achieve the same level of general intelligence.
Brain imaging has revealed that men have more gray matter related to intellectual ability while women have more white matter.
Gray matter refers to information processing centers while white matter refers to connections between the processing centers.
Men have about 6.5 times as much general intelligence gray matter as women while women have about 10 times as much white matter, report researchers from the University of California, Irvine and the University of New Mexico.
"These findings suggest that human evolution has created two different types of brains designed for equally intelligent behavior," says researcher Richard Haier of the University of California, Irvine. "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."
Using such tools as magnetic resonance imaging and cognitive tests, Haier and colleagues produced brain maps that correlated brain tissue volume with IQ.
Besides finding differences in amounts of white and gray matter, the researchers also found regional differences. Intelligence-related gray matter, for example, appears to be distributed throughout the brain in men while in women it's more localized to the frontal lobe.
Regionalization may help explain why women and men appear to be hardwired to excel at different tasks, such as mathematics for men and language facility for women. Overall, however, says study coauthor Rex Jung of the University of New Mexico, the different brain organizations produce equivalent overall performance on broad cognitive measures such as intelligence tests.
The research supports clinical findings that women are more cognitively affected by frontal brain injuries. They could ultimately help improve the diagnosis and treatment of brain disorders in men and women.
The research is reported in the journal NeuroImage (read abstract).
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