Size seems to matter—for certain kinds of intelligence —according to a new study by Sandra Witelson, professor of psychiatry and behavioral neuroscience at McMaster University in Ontario.
Witelson asked 100 terminally ill cancer patients to take a series of cognitive tests. After each person died, she and her colleagues measured the volume of the subject’s cerebral hemispheres. On average, women with larger brains had performed better on verbal tests than women with smaller brains had. There was also a less pronounced association between brain size and visual-spatial ability. The results were equivalent for right-handed and nonright-handed women.
Right-handed men showed similar results for verbal skills, but no correlation registered among nonright-handed men; for lefties and ambidextrous males, brain volume did not predict how well they had done on the language tests. Witelson also found that for all men, overall brain size had no relation to visual-spatial abilities. Yet in one case, she found an exception. In earlier work, Witelson had studied the anatomy of Albert Einstein’s brain and showed that although it was of average overall size, the inferior parietal lobes were expanded. These regions are crucial to processing visual imagery.
The new work also unveiled one correlation that is sure to make for a few sharp quips at cocktail parties. As men age from 25 to 80, the size of their brain generally decreases, yet age barely alters brain size in women. Experts do not yet know whether genes, hormones or environmental factors underlie different aging patterns.