The Male Condition
By SIMON BARON-COHEN
TWO big scientific debates have attracted a lot of attention over the past year. One concerns the causes of autism, while the other addresses differences in scientific aptitude between the sexes. At the risk of adding fuel to both fires, I submit that these two lines of inquiry have a great deal in common. By studying the differences between male and female brains, we can generate significant insights into the mystery of autism.
So was Lawrence Summers, the president of Harvard, right when he remarked that women were innately less suited than men to be top-level scientists? Judging from current research, he was and he wasn’t. It’s true that scientists have documented psychological and physiological differences between male and female brains. But Mr. Summers was wrong to imply that these differences render any individual woman less capable than any individual man of becoming a top-level scientist.
In fact, the differences that show up in brain research reflect averages, meaning that they emerge only when you study groups of males and females and compare the two groups’ averages on particular psychological tests or physiological measures. The evidence to date tells us nothing about individuals – which means that if you are a woman, there is no evidence to suggest that you could not become a Nobel laureate in your chosen area of scientific inquiry. A good scientist is a good scientist regardless of sex.
Nonetheless, with brain scanning, we can discern physiological differences between the average male and the average female brain. For example, the average man’s cerebrum (the area in the front of the brain concerned with higher thinking) is 9 percent larger than the average woman’s. Similar, though less distinct, overgrowth is found in all the lobes of the male brain. On average, men also have a larger amygdala (an almond shaped structure in the center of the brain involved in processing fear and emotion), and more nerve cells. Quite how these differences in size affect function, if at all, is not yet known.
In women, meanwhile, the connective tissue that allows communication between the two hemispheres of the brain tends to be thicker, perhaps facilitating interchange. This may explain why one study from Yale found that when performing language tasks, women are likely to activate both hemispheres, whereas males (on average) activate only the left hemisphere.
Psychological tests also reveal patterns of sex difference. On average, males finish faster and score higher than females on a test that requires the taker to visualize an object’s appearance after it is rotated in three dimensions. The same is true for map-reading tests, and for embedded-figures tests, which ask subjects to find a component shape hidden within a larger design. Males are over-represented in the top percentiles on college-level math tests and tend to score higher on mechanics tests than females do. Females, on the other hand, average higher scores than males on tests of emotion recognition, social sensitivity and language ability.
Many of these sex differences are seen in adults, which might lead to the conclusion that all they reflect are differences in socialization and experience. But some differences are also seen extremely early in development, which may suggest that biology also plays a role. For example, girls tend to talk earlier than boys, and in the second year of life their vocabularies grow at a faster rate. One-year-old girls also make more eye contact than boys of their age.