Scans prove there’s no such thing as a ‘male’ or ‘female’ brain
Petr Strnad/Millennium Images, UK
You may have read that having a male brain will
earn you more money. Or maybe that female brains are
better at multitasking. But there is no such thing as a female or male brain, according to the first search for sex differences across the entire human brain. It reveals that most people have a mix of male and female brain features. And it also supports the idea that gender is non-binary, and that gender classifications in many situations are meaningless.
“This evidence that human brains cannot be categorised into two distinct classes is new, convincing, and somehow radical,” says
Anelis Kaiser at the University of Bern, Switzerland.
The idea that people have either a “female” or “male” brain is an old one, says
Daphna Joel at Tel Aviv University in Israel. “The theory goes that once a fetus develops testicles, they secrete
testosterone which masculinises the brain,” she says. “If that were true, there would be two types of brain.”
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To test the theory, Joel and her colleagues looked for differences in brain scans taken from 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.
Spatial awareness
Although the team only looked at brain structure, and not function, their findings suggest that we all lie along a continuum of what are traditionally viewed as male and female characteristics. “The study is very helpful in providing biological support for something that we’ve known for some time – that gender isn’t binary,” says
Meg John Barker, a psychologist at the Open University in Milton Keynes, UK.
Scans prove there’s no such thing as a ‘male’ or ‘female’ brain