(1) From the article on dyslexia (click here) by Shaywitz on this website.

"Our investigation has already revealed a surprising difference between men and women in the locus of phonological representation for reading. It turns out that in men phonological processing engages the left inferior frontal gyrus, whereas in women it activates not only the left but the right inferior frontal gyrus as well. These differences in lateralization had been suggested by behavioral studies, but they had never before been demonstrated unequivocally. Indeed, our findings constitute the first concrete proof of gender differences in brain organization for any cognitive function. The fact that women's brains tend to have bilateral representation for phonological processing explains several formerly puzzling observations: why, for example, after a stroke involving the left side of the brain, women are less likely than men to have significant decrements in  their language skills, and why women tend more often than men to compensate for dyslexia. Our investigation has already revealed a surprising difference between men and women in the locus of phonological representation for reading. It turns out that in men phonological processing engages the left inferior frontal gyrus, whereas in women it activates not only the left but the right inferior frontal gyrus as well. These differences in lateralization had been suggested by behavioral studies, but they had never before been demonstrated unequivocally. Indeed, our findings constitute the first concrete proof of gender differences in brain organization for any cognitive function. The fact that women's brains tend to have bilateral representation for phonological processing explains several formerly puzzling observations: why, for example, after a stroke involving the left side of the brain, women are less likely than men to have significant decrements in  their language skills, and why women tend more often than men to compensate for dyslexia"

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from Time, July 17, 1996

Just last week a new study showed hat in science tests teenage boys who scored in the top 5% outnumbered girls 7 to 1, while girls outperformed boys in reading comprehension. In general, men as a group excel at tasks that involve orienting objects in space --like reading a map without having to turn it so it lines up with the road. Women, on the other had, seem to be more adept a communication, both verbal and nonverbal. Readings of MRI [Magnetic Resonance Imaging] scans suggest one reason: women seem to have stronger connections between the two halves (hemispheres) of the brain.

What's sauce for the goose need not be a problem for the gander, however. The relative lack of cross talk between their hemispheres may actually benefit men by allowing each half of the brain to concentrate on what it does best. Studies have sown that when men are confronted with problems that deal with spatial orientation -- a function that can be handled by both the left and right hemispheres-- they tend to use the right hemisphere only. Thus, there aren't many distracting messages coming in from the left hemisphere, which concentrates on language. This cerebral division of labor could also explain why there are so many more male architects and chess champions. Their brains may simply be better able to concentrate on solving problems involving spatial relations.

Just because scientists can measure these differences, however, does not mean they understand their causes. Are men born with better spatial abilities, or do they develop them by playing sports in which eye-hand coordination is crucial? Are women innately better at reading words and understanding emotions, or do they just get more practice? If heredity and biology are important, though, then it's a pretty good bet that the sex hormones are somehow involved. For that reason, researchers have begun delving into the effects of testosterone and estrogen on the brain.

Although romantics of all ages can recall occasions when lust interfered with reason, scientists once believed that sex hormones had very little effect on the brain. The chemicals' only target was supposed to be a tiny target called the hypothalmus, buried deep in the brain, which is the seat for sexual drive and other urges, such as appetite and aggression. Recent research, however, has shown that the entire brain, including the thought-processing cortex, is awash in sex hormones, even before birth. The larger amounts of testosterone produced by males may predispose men's brains toward greater specialization of the two hemispheres.

This oversimplifies the case, of course. There are men whose brains are not especially compartmentalized, and women whose brains are. And when a brain fits the mold, performance is not always predictable. Consider Judit Polgar, who at 15 became the world's youngest chess grandmaster. Her success does not mean that she has a male-wired brain. Nor did Shakespeare, whose intuitions about women were uncanny, necessarily have female wiring. The variation between the sexes pales in comparison with individual differences --and shows how marvelously vesatile a 3-lb. mass of nerve cells can be.