No Functional Differences Between Male And Female Brains, Finds Sweeping Review

An analysis of 30 years’ worth of MRI and cadaver studies found that once brain size is corrected for, sex accounts for just 1 percent of any differences. Image Credit: pathdoc / Shutterstock.com

A review of decades’ worth of research has concluded that the human brain is remarkably similar between sexes. Contrary to the belief of "that one sexist uncle", women’s brains are no different from males, and no observed differences were consistent from one study to the next.  

The review, published in Neuroscience and Biobehavioural Reviews, is an analysis of 30 years’ worth of MRI and cadaver studies, finding that once brain size is corrected for, sex accounts for just 1 percent of any differences.  

Neurology has been steeped in sexism over the past few decades, dubbed "neurosexism". Stemming from a range of misinterpreted or biased studies, neurosexism has resulted in the belief that women's brains are either much less developed, worse at logical work, or have less grey matter, supposedly leaving them more suited to multitasking and classical gender roles. A dive into this data suggests that it was never founded in concrete evidence, but that hasn't stopped many people from citing it anyway. 

So, Lise Eliot – a neuroscientist and champion against all things neurosexist – took a deeper look to try and distinguish any differences between the sexes’ brains. The data spanned a large number of studies, many of which had results that directly conflicted with one another, with Eliot and her team looking at the results and methodology of each. 

“Like many neuroscientists, I was under the impression that if we can just get up to bigger sample sizes, we will get rid of the noise; we’ll be able to see these reliable differences,” said Eliot, speaking to Academic Times

“And the sample sizes are getting larger and larger – well into the thousands – but we’re not finding these reliable differences.” 

This isn’t to say that male and female brains are exactly the same. It’s true the male brain is slightly larger – around 11 percent in volume – but larger brains generally just have more white matter regardless of whether they're from a male or a female. White matter simply passes messages across the brain and doesn't correlate with functional improvements. In fact, brain size is not correlated with smarts in any way – if so, the sperm whale would be exploring the galaxy by now.  

Once accounting for size, it appears that male and female brains are monomorphic (showing little or no variation between each other) instead of dimorphic. Some large studies claimed to find larger specific structures in females as a result of estrogen receptor distribution, but actual measurements of brain volumes were unreliable and insignificant.  

This review marks the most comprehensive and up-to-date comparison of brain differences between sexes. It finds results that many already knew – there is absolutely no consensus on strong sexual dimorphism in human brains.

[H/T: Academic Times]

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