There’s no such thing as a ‘male’ or ‘female’ brain

It is said that men are from Mars and women are from Venus, but in fact it seems both are very much from Earth. New research finds that while there are sex/gender differences in the brain, human brains do not belong to one of two distinct categories: male brain or female brain.

While some ‘male’ and ‘female’ features do exist, the vast majority of people have a mix, so a general binary categorisation does not emerge.

Research by Joel et al studied the physical features of the brains of 1400 people aged between 13 and 85.

    The team looked for variations in the size of brain regions as well as the connections between them. In total, the group identified 29 brain regions that generally seem to be different sizes in self-identified males and females. These include the hippocampus, which is involved in memory, and the inferior frontal gyrus, which is thought to play a role in risk aversion.

    When the group looked at each individual brain scan, however, they found that very few people had all of the brain features they might be expected to have, based on their sex. Across the sample, between 0 and 8 per cent of people had “all-male” or “all-female” brains, depending on the definition. “Most people are in the middle,” says Joel.

    This means that, averaged across many people, sex differences in brain structure do exist, but an individual brain is likely to be just that: individual, with a mix of features. “There are not two types of brain,” says Joel.

Since the research is paywalled I haven’t read the paper, so I can’t say why the features designated “male” and “female” were so designated. I gather they were not completely different.

The bottom line is that the terms ‘male’ or ‘female’ brain make no sense when referring to the physical nature of the brain. However, that still leaves open the question of whether there are gender differences in what the brain does.

Gina Rippon in commenting about the article refers to other gender research, including work by Harry Reis and Bobbi Carothers. They say:

    Many people assume that sex differences in social behavior are categorical—that these differences represent fundamental distinctions between two distinct categories (taxa) of humans. Contrasted with this view is the idea that sex differences are dimensional—that differences between men and women indicate nothing more than relative positions along overlapping continuous dimensions.

To illustrate what a taxon is they use human measurements and strength. If you plot height and hair length, for example, you come up with something like this:


While there is overlap, the proportion of men who are taller than all women is quite substantial. In these circumstances it makes sense to think in terms of categories or taxa.

When they turn to social, psychological and personality characteristics, the categorical or taxonic analysis makes no sense. While there are statistical differences they lie along a dimension. What stands out is the overlap, the similarities.

Their analyses:

    were run on a series of 22 discrete data sets in the published literature, which comprised 122 indicators and 13,301 individuals from 13 unique studies.

They point out that their samples were limited to modern North America, possibly a culture that may have become “detaxonified.” There may be cultural differences elsewhere in the world. They conclude:

    At least with regard to the properties that we studied, rather than representing distinct categories of humans, women and men are cut from the same psychological cloth.

To follow their title, it’s a case of shades of grey rather than black and white.

I’ve turned on the “moderate comments” button on the discussion thread, because I’d like to stay on topic rather than to stray into gender relations and feminism.

5 thoughts on “There’s no such thing as a ‘male’ or ‘female’ brain”

  1. Over time men and women have faced different evolutionary pressures. Evolutionary pressures that may differ for different environments, cultures and points in history. Compared with many species the physical differences between human males and females are more pronounced.
    Given the above it would be surprising if there weren’t some differences between male and female brains. The problems that traditional males and females had to solve well were different. Keep in mind that the ability to solve particular problems may reflect the richness of the interconnections in parts of the bran rather than physical size.
    It is difficult to separate genetics and use when looking at differences. For example, one man may be more muscular than another because of training or genetic difference. The same applies to mental skills.
    Brian: The study concentrates on gross physical differences. One obvious question is the extent to which say a male with a brain more similar to the “female” brain has a more “female” set of skills. (i.e. Do the gross physical differences count?

    So it would be su

  2. John, they say they looked at the interconnections and found no significant difference. In any case the Reis and Carothers research found that functionally there was no significant gender difference in the brains of North Americans.

  3. It’s my understanding that every human body starts off as female and then the males get differentiated a month or two down the track (this is the reason male mammals have nipples). It seems to me that “male” and “female” brains would therefore be fundamentally the same.
    If in reality women were from Venus and men were from Mars, where would trans-gendered people be from? The older I get and the more I know, the less I can accept that Male/Female is a valid dichotomy. In my experience gender is a garden where a thousand flowers bloom, all of them different.

  4. Well said, zoot. This article, linked by Gina Rippon, tells the story of how gender develops in the uterus.

    It also says:

    What’s more, new technologies in DNA sequencing and cell biology are revealing that almost everyone is, to varying degrees, a patchwork of genetically distinct cells, some with a sex that might not match that of the rest of their body.

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