These days, when the word “brain” has all but replaced the word “mind” in the popular press, attempts at justifying gender stereotypes and bigotry seem to have found a new frontier – neuroscience. Studies indicating even the slightest difference between the “wiring” of male and female brains tend to get blown way out of proportion, and hailed as concrete proof that men are, in fact, fundamentally different from women.
One of the mainstays of “neuro-sexist” accounts of the “female brain” is the long-held idea that women have much larger hippocampi – parts of the brain located under both sides of the cerebral cortex, and linked to memory and connecting emotions to the senses – that would explain their being more emotionally expressive, and having better interpersonal skills and verbal memory.
As the majority of neuroscientists themselves have suspected, however, this is, quite simply, not true – a recent meta-analysis, carried out by researchers at the Rosalind Franklin University of Medicine and Science, and published in the journal NeuroImage, looked at the findings of 76 published studies, involving more than 6,000 MRI scans from healthy subjects of all ages, and found no statistically significant differences.
“Sex differences in the brain are irresistible to those looking to explain stereotypic differences between men and women,” said lead author Lise Eliot, PhD, an Associate Professor of Neuroscience at the university’s medical school. “They often make a big splash, in spite of being based on small samples. But as we explore multiple datasets and are able to coalesce very large samples of males and females, we find these differences often disappear or are trivial.”
The oft-cited claim that women possess better-developed hippocampi was based on studies comparing these structures in both male and female brains, but failing to account for total brain volume (TBV) or intracranial volume (ICV). Controlling for that, the perceived differences vanished.
“In summary, we found that human males of all ages exhibit a larger HCV [hippocampal volume] than females, but adjusting for individual differences in TBV or ICV results in no reliable sex difference. The frequent claim that women have a disproportionately larger hippocampus than men was not supported,” wrote the authors in their study.
According to Eliot, although many people believe there to be a neurologically-defined “male brain” and a concomitant “female brain”, looking beyond the few popularised studies reveals the differences to be, at best, minimal.
Large-scale meta-analyses carried out in the past have already debunked a number of other culturally-influential ideas tying observed behaviours with physical characteristics in the brain – as it turns out, there is no difference in the size of the corpus callosum, white matter that allows the two sides of the brain to communicate, nor do men and women differ in the way their left and right hemispheres process language.
Few people would deny there are observable differences between the way men and women behave, but as more research rolls in, it becomes increasingly clear that these differences are not easy to pin down to neural disparity, and, in the end, might have more to do with culture than the “wet stuff” of our minds.