Brain Differences Between the Genders

There are three reasons to expect evolution to have produced different mentalities in men and women. The first is that men and women are mammals, and all mammals show sexual differences in behavior. As Charles Darwin put it, "No one disputes that the bull differs in disposition from the cow, the wild boar from the sow, the stallion from the mare."' The second is that men and women are apes, and in all apes there are great rewards for males that show aggression toward other males, for males that seek mating opportunities, and or females that pay close attention to their babies. The third is that men and women are human beings, and human beings are mammals with one highly unusual characteristic: a sexual division of labor Whereas a male and a female chimp seek the same sources of food, a male and a female human being, in virtually every preagricultural society, set about gathering food in different ways. Men look for sources that are mobile, distant, and unpredictable (usually meat), while women, burdened with children, look for sources that are static, close, and predictable (usually plants).

In other words, far from being an ape with fewer than usual sex differences, the human being may prove to be an ape with more than usual sex differences. Indeed, mankind may be the mammal with the greatest division of sexual labor and the greatest of mental differences between the sexes. Yet, though mankind may have added differences between the sexes. Yet, though mankind may have added division of labor to the list of causes of sexual dimorphism, he has subtracted the effect of male parental care.

Of the many mental features that are claimed to be different between the sexes, four stand out as repeatable, real, and persistent in all psychological tests. First, girls are better at verbal tasks. Second, boys are better at mathematical tasks. Third, boys are more aggressive. Fourth, boys are better at some visuo-spatial tasks and girls at others. Put crudely, men are better at reading a map and women are better judges of character and mood—on average. (And, interestingly, gay men are more like women than heterosexual men in some of these respects.)

The case of the visuo-spatial tasks is intriguing because it has been used to argue that men are naturally polygamous^ by analogy with the case of the mice quoted at the beginning of this chapter. Crudely put, polygamist mice need to know their way from one wife's house to another—and it is certainly true that in many polygamous animals, including our relatives, orangutans, males patrol an area that includes the territories of several wives. When people are asked to rotate a diagram of an object mentally to see if it is the same as another object, only about one in four women scores as highly as the average man. This difference grows during childhood. Mental rotation is the essence of map reading, but it seems a huge jump to argue that men are polygamous because they are better at map reading just because the same is true of mice.

Besides, there are spatial skills that women perform better than men. Irwin Silverman and Marion Eals at York University in Toronto reasoned that the male skill at mental-rotation tasks probably reflected not some parallel with polygamous male mice patrolling broad territories to visit many females but a much more particular fact about human history: that during the Pleistocene period, when early man was an African hunter-gatherer tor a million years or more, men were the hunters. So men needed superior spatial skills to throw weapons at moving targets, to make tools, to find their way home to camp after a long trek, and so on.

Much of this is conventional wisdom, but Silverman and Eals then asked themselves: What special spatial skills would women gatherers need that men would not? One thing they predicted was that women would need to notice things more—to spot roots, mushrooms, berries, plants—and would need to remember landmarks so as to know where to look. So Silverman and Eals did a series of experiments that required students to memorize a picture full of objects and then recall them later, or to sit in a room for three minutes and then recall what objects were where in the room. (The students were told they were merely being asked to wait in the room until a different experiment was ready.) On every measure of object memory and location memory, the women students did 60-70 percent better than the men. The old jokes about women noticing things and men losing things about the house and having to ask their wives are true. The difference appears around puberty, just as the social and verbal skills of women begin to exceed those of men.

Notes:

Some dimorphism between the sexes as a result of evolution.

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 The Red Queen: Sex and the Evolution of Human Nature
Books, Brochures, and Chapters>Book:  Ridley , Matt (2003-05-01), The Red Queen: Sex and the Evolution of Human Nature, Harper Perennial, Retrieved on 2011-05-03
Folksonomies: evolution culture sex evolutionary psychology