Despite the correlation, however, variability in humans is enormous. Average human brain weight is about 1,500 grams (about 10 percent less than the estimate for Neanderthal brains, by the way). Einstein's brain weighed in at about 1,230 grams, which is about 18 percent below average. He did, on the other hand, have somewhat wider than normal parietal lobes, which may have contributed to his mathematical ability.
Clearly, total brain size is only one attribute that underlies intelligence. Brain size may represent a potential capability, like height, that has advantages in some intellectual arenas but not others. The American autodidact Chris Langan, who has a very large head and scores at record levels on some IQ tests, is employed as a bar bouncer.
