Flaws in the neuroscience of sex/gender differences
Sex/gender differences research is inconsistent in neuroscience. Scientists have reported that the brains of women and men are anatomically different. They claim that, on average, women have smaller brains and bodies than men. Men are consistently reported to have greater total brain volume than women, even after statistically controlling for body size differences.
However, focusing on the difference between women and men’s brain size can be misleading because, when you look at the full data, there’s actually considerable overlap between women and men’s brain sizes.
The size of brains vary based on numerous factors, and a human being cannot be confidently identified as male or female — and, by extension, a man or a woman — solely by their brain.
The concern of overlap is also relevant when assessing behavioural differences between women and men. Studies show that cognitive skills such as spatial reasoning or verbal fluency are robustly differentiated by sex/gender. However, the performance scores on these tasks have considerable overlap between samples of women and men, meaning that it is misleading to report these behaviours as being differentiated by sex/gender.
When studying sex/gender differences in the brain, studies often look at how participants carry out certain tasks. Scientists choose tasks that can assess behaviour that is stereotyped with one sex or gender, like multitasking, socializing, and navigating. One type of task is a spatial task called mental rotation, in which men generally outperform women. This is an example of a behavioural difference between women and men.
Since there are potential behavioural differences between women and men, neuroscientists look for corresponding functional differences between women and men’s brains. An example of a functional difference is if women and men perform the same task, and there is brain activity present in one region of the women’s brain that isn’t present in the same region for men.
To examine whether functional brain differences exist, Kenneth Hugdahl and his colleagues had participants perform a mental rotation of an object while using functional neuroimaging to see which regions of the brain were active during this spatial task performance. They reported that men displayed higher neural activity in the parietal lobe than women, who showed more activity in the frontal lobe. This means that this study showed a functional difference in women and men’s brains.
However, despite finding differences in the activity of the brain, there was no difference in how the participants performed the task. Therefore, this particular study shows a functional brain difference but not a behavioural difference.
From Hugdahl and colleagues’ study, we can understand that a functional difference doesn’t automatically work out to a generalizable behavioural difference between women and men. After all, if women and men performed equally on a task but their brains showed different activation, that brain activity cannot tell us about the ability of women or men to perform that task. It can only tell us that their brains achieved the same answer using different resources.
This could be because of neural differences in women and men that are present at birth, or it could be due to socialization and different experiences that provide women and men different strategies to approach the task. Again, you can see how sex and gender are entangled.
Another major fallacy in neuroscience comes with the issue of reverse inference. An example of this is when scientists take a behavioural sex/gender difference or stereotype and use it to interpret the brain activity findings. For instance, the expectation that men perform better on a spatial task can bias the interpretation of differences in brain activity found between women and men. This can lead to erroneous reports of how the brain functions.
Robyn Bluhm exposed how reverse inferences in interpreting brain activity can be detrimental to sex/gender differences research. She showed that several studies monitoring brain activity for the same cognitive task interpreted the neural activity differently so it aligned with expected sex/gender stereotypes.
For instance, high brain activity in men was reported as high task ability, but high brain activity in women was interpreted as low neural efficiency, claiming that women needed more neural resources to complete the task.
This shows that when scientists design a study with a preconceived outcome, such as men performing better on the task, biases are easily woven into the interpretation. This normalizes sex/gender stereotypes.
Neuroscience without sex/gender bias
When you combine the aforementioned anatomical, functional, and behavioural findings, it creates a narrative that women and men have biologically different brains, even though there are shortcomings in the collection and interpretation of the data. Also, this narrative often doesn’t fully factor in the influence of social and environmental factors on neural and psychological development, focusing more on nature than nurture.
However, it’s nearly impossible to disentangle so-called biological sex from socialized gender identity. Think about it: gendered socialization occurs before a baby is even born. We throw elaborate gender reveal parties, buy certain clothes or toys for babies, and decorate nurseries a certain way before birth.
Children are bombarded with gendered paraphernalia from the first baby shower, and we continue to be bombarded throughout adulthood, influencing how we experience and engage with the world.
That raises the question: what is gained from defining biological differences, as opposed to social differences, between women and men? Insisting upon focusing on biological explanations of sex/gender differences is a feature of neurosexism, a term coined by Cordelia Fine, author of Delusions of Gender. Neurosexism saturates neuroscience with antiquated ideals of differences between women and men, perpetuating sex/gender stereotypes.
Neurosexism persistently investigates and re-investigates sex/gender differences in the brain. Although these sex/gender differences have been discredited, new investigations are still being initiated to try to demonstrate biological differences based on sex. Rippon compares this persistence to a game of whack-a-mole — as one claim is debunked, another pops up to take its place.
Advocates of neurofeminism, which is the antithesis of neurosexism, strike down these recurring neurosexist claims by exposing statistical invalidity, reverse inference, and historical inconsistencies.
Neurofeminism operates from an understanding that sex/gender is diverse and fluid. It acknowledges that sex/gender differences exist in the brain, but believes that in order to best interpret results, we must recognize both the biological and social influences of sex/gender. Rather than using sex/gender differences to support a belief that one group is better than the other, neurofeminists recognize that sex/gender differences are a product of sex/gender stereotypes being perpetuated in our society.
A good example of this is the use of the term ‘sex/gender’ instead of ‘sex’ by neurofeminist scholars. This term acknowledges both biological and social factors, whereas ‘sex’ places emphasis on the biological.
It’s important that neuroscientists reflect on the implications of research on sex/gender differences and the persistence of finding sex/gender differences. It’s not always possible to remove sex/gender as a variable from research designs, but scientists can approach the topic with renewed insight.