See? I knew it.
Dr. Ragini Verma, professor of radiology at the University of Pennsylvania, has published a study in the Proceeedings of the National Academy of Sciences in which she mapped differences in the wiring of male and female brains, using a technique called diffusion tensor imaging. The study was conducted in order to provide better treatment for neurological disorders, but the findings are intriguing for another reason: they appear to confirm and explain stereotypes about the differences between men and women.
The study was conducted on 428 men and boys and 521 women and girls. The diagrams in the image above show an averaging of the "connection trends" in the participants' brains. (Men are on the left; women are on the right.) In the image, we see the connections in the cerebrum, which is above the cerebellum and toward the front. In men, these connections are primarily within hemispheres; in women, they are primarily across the hemispheres.
The connection trends in the cerebellum, which are not visible here since the cerebellum is underneath the cerebrum, are exactly the opposite of what we see in the image above: men's connections go across hemispheres while women's stay within hemispheres. The cerebrum is primarily responsible for thinking; the cerebellum is responsible for acting.
How should we interpret these patterns? Let's start with the cerebrum. The left side of the cerebrum is specialized to handle logical thought, while the right is devoted to intuitive thought. According to Dr. Verma, the "cross-talk" between the left and right sides of the cerebrum in women's brains explains why women tend to have better memories than men, and also why they are (generally) more socially adept, better able to multitask, and more verbal. (One might infer a superiority in matters of social politics and emotional intelligence, both of which require a linking of intuition and logic, although Dr Verma did not say this.)
Men, most of whose cerebrum connections stay within individual hemispheres, are generally superior to women at thinking tasks that "do not need complex inputs from both hemispheres" -- things like tracking prey, fighting predators, and finding the way home after tracking prey and fighting predators. Here too, one might infer -- as one blogger has done -- that the male's lesser dependence on the intuitive side of the cerebrum enables him to act "more rapidly and more decisively" than the female, making him a better, more focused fighter.
The cerebrum pattern, according to Dr. Verma, might explain not only female intuition but also the maternal instinct:
Because the female connections link the left hemisphere, which is associated with logical thinking, with the right, which is linked with intuition, this could help to explain why women tend to do better than men at intuitive tasks...
“Intuition is thinking without thinking. It's what people call gut feelings. Women tend to be better than men at these kinds of skill which are linked with being good mothers,” Professor Verma said.
As to the heightened cross-talk in men's cerebellums -- the action center that lies under the thinking center -- it might explain why men tend to outperform women in motor and spatial relations tasks, have better muscle control, and are generally more coordinated than women.
Interestingly, it seems that we're not born this way. The study involved participants as young as eight, and the brains of boys and girls aged eight to 13 showed very similar connection patterns. The 13-17 age bracket showed more differences, and there were still more in young adults over 17. The differences appear to begin to manifest "mainly when sex itself begins to matter" -- i.e., when puberty hits.
These images make me curious: since men's cerebrum connection patterns run longitudinally, within the hemispheres, does that mean men are more likely than women to be strongly "right-brained" (intuitive) or "left-brained" (logical)? The cerebral cross-talk among women seems to indicate not that they are necessarily more intuitive, but that they are a) better able to harness their intuition to logic, and b) better able to express their intuition coherently. The study also doesn't draw any conclusions about why men dominate women in the sciences and in math, although there are obviously strong social dynamics at work there as well as neurological ones.