Research in evolutionary psychology and related fields has uncovered the distinct ways that men’s minds and women’s minds operate. Few have made greater contribution to the discovery of the “male brain” and the “female brain” than Simon Baron-Cohen of the University of Cambridge, Bernard Crespi of Simon Fraser University, and my esteemed LSE colleague Christopher Badcock. So what is the male brain? What is the female brain?

The male brain is characterized by systemizing tendencies (to use Baron-Cohen’s term) and mechanistic thinking (to use Crespi and Badcock’s term). “Systemizing” is the drive to analyze, explore, and construct a system. The systemizer intuitively figures out how things work, or extracts the underlying rules that govern the behavior of a system. The purpose of this is to understand and predict the system, or to invent a new one.

In contrast, the female brain is characterized by empathizing tendencies (to use Baron-Cohen’s term) or mentalistic thinking (to use Crespi and Badcock’s term). “Empathizing” is the drive to identify another person’s emotions and thoughts, and to respond to them with an appropriate emotion. Empathizing occurs when we feel an appropriate emotional reaction in response to the other person’s emotions. The purpose of this is to understand another person, to predict his or her behavior, and to connect or resonate with him or her emotionally.

The difference between “mechanism” and “mentalism” is similar to the difference between “systemizing” and “empathizing.” In short, mechanism is about figuring things out (folk physics); mentalism is about understanding people (folk psychology).

There are many individual exceptions to any empirical generalization, but exceptions do not invalidate generalizations. For example, there are many women who are taller than the average man, and there are many men who are shorter than the average woman. But the generalization “Men are on average taller than women” is still valid. Similarly, not all men have a strong male brain, and not all women have a strong female brain, but there are average differences between men and women, and men are far more likely to have the male brain and women are far more likely to have the female brain.

These sex differences emerged during the course of human evolution because men and women often faced different selection pressures. Men have come to acquire systemizing and mechanistic skills because such skills were necessary for inventing and making tools and weapons. At the same time, low empathizing ability was helpful for men in tolerating solitude during long hunting and tracking trips, and for committing acts of interpersonal violence and aggression necessary for male competition. (It is very difficult to kill other people if you strongly feel for them.) Similarly, women have come to acquire empathizing and mentalistic skills because they facilitate various aspects of mothering, such as anticipating and understanding the needs of infants who cannot yet talk, or making friends and allies in new environments, in which ancestral women found themselves upon marriage. (In the ancestral environment, women left their natal group and married into a neighboring group upon puberty, a practice necessary to avoid inbreeding.)

The late William D. Hamilton, the Oxford evolutionary biologist who is universally regarded as “the best Darwinian since Darwin,” said it best, when he noted, “People divide roughly, it seems to me, into two kinds, or rather a continuum is stretched between two extremes. There are people people, and things people.” What the recent work of Baron-Cohen and Crespi and Badcock shows is that, to a large extent, people people are women, and things people are men.

Men’s greater systemizing and mechanistic skills are the primary reasons why they are better than women at mathematics, physics, and engineering, because all of these fields deal with various rational “systems” governed by rules. Women’s greater empathizing and mentalistic skills are the primary reasons why they are better at languages and why they are better judges of character. Women also dominate primatology, which, like mothering of infants, requires understanding and reading the minds of individuals with whom they cannot communicate by language.

But these adaptive sex differences sometimes misfire and manifest themselves in comical ways. For example, men’s greater tendency toward systemizing and mechanistic thinking means that they often try to “figure out” their relationships with their girlfriends as if they are logical systems or a carburetor. They don’t realize that relationships involve other human beings with emotions and feelings, which are not always rational and logical, and they instead treat other people as if they were machines. Similarly, women often talk to their cars and copy machines, as if they had minds and feelings. They don’t realize that they cannot really relate to their cars and copy machines, because they have no feelings or emotions; they have no “minds” they can read.

On the whole, however, these sex differences are adaptive. Men and women are different because their brains function in different ways and as a result they have different strengths and weaknesses. But what happens when their brains are too strong in one way or the other? What happens if they have an “extreme male brain” or “extreme female brain”? That’s the topic of the next post.

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