The Left accuses the Right of being anti-science, but even the least educated conservative knows that men and women are different. While radical feminists keep propagandizing the gullible that gender differences are a myth perpetuated by the Patriarchy (email me the whens and wheres of our next secret meeting), real scientists are documenting the biological realities.
This meta-analysis of 126 studies shows very clearly that from birth to death males have bigger brains than females. Men, on average, had greater total volumes on all of the following measures: intracranial, cerebrum, gray matter, white matter, cerebellum, and cerebrospinal fluid. There was no major region that was larger in women. Depending on the study, male brains were between 8 and 13% larger.
The researchers also found significant volume differences in small regions. Men averaged larger gray matter volumes in 33 areas, and 17 regions in females had more gray matter. They also looked at gray matter density and reported that six regions in men were denser, while one area had greater density in women.
When regions are larger in males, they tend to be in the left hemisphere. When areas are larger in women, they tend to be in the right one, so there is evidence of lateralization differences between the sexes.
Differences seem to emerge in regions known to be involved in language and emotion. This makes sense since women tend to have a verbal advantage, and the sexes differ significantly in certain emotions like empathy.
Why do men have larger brains? It looks like the studies did not adjust for body size, but even if you argue that male brains are bigger simply because their bodies are bigger, why are many areas larger in women? Brains are very costly organs: they use a tremendous amount of energy, and big heads can kill mothers during birth. Bigger brains are there for a reason.
After reading Arthur Jensen, I assumed men and women had identical average IQs, and that men were simply more diverse with a greater number of dullards and geniuses. In recent years, evidence has emerged that, compared to females, male IQ peaks more slowly, and at a somewhat higher level (about four IQ points). Researchers like Jensen supposedly missed this by focusing on samples of adolescents rather than fully developed adults.
Perhaps the 10% bigger brain gives men a little more mental horsepower. It's a hazardous business to speculate why this would be. Whatever the reason, the difference is real, and the feminists are wrong.
I imagine a skeptic will argue that perhaps the differences are due to environmental factors: male babies are fed and treated better, boys are given more intellectual stimulation, etc. But why the differentiation where some regions are larger in men, while other areas are larger in women? And while the samples didn't allow a detailed study of age, it looks like the sex differences are in place among neonates. Differences emerge early in life before many social factors are able to kick in.
UPDATE: Many of the regions with a male advantage are in the limbic system which is associated with aggression and sexual interests. There are, of course, big sex differences in these traits.
UPDATE 2: As mentioned, areas that have greater volume in women tend to be in the right hemisphere which is associated with a proneness to negative emotions. While women are not more prone to anger than men, they do tend to be more anxious and depressed.
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