The truth about the female brain A part of popular science is unthinkingly biased

Gina Rippon’s study The Gendered Brain: The New Neuroscience that Shatters the Myth of the Female Brain – which featured on The Guardian‘s ‘Summer reading’ list – is the latest example of this unfortunate genre. The book is concerned with the question of whether the brain exhibits sex differences, and whether they are caused by nature or nurture.

Rippon’s argument is blunt. The idea that “you can describe a brain a ‘male’ or ‘female,'” she declares, “is characterised by bizarre claims which can be readily dismissed, only to pop up again in another form”. She contends that scientists who have studied sex differences in the brain have historically been sexist and have hunted down differences that did not really exist, in an attempt to prove the inferiority of women.

“The so-called ‘female’ brain,” says Rippon, “has suffered centuries of being described as undersized, underdeveloped, evolutionarily inferior, poorly organised and generally defective.” Such assertions were, and still are, so widespread that Rippon admits feeling as though she’s playing “Whac-a-Mole”. She has barely disproved the newest study professing to demonstrate how men and women’s brains differ, when another is published.

Rippon’s opponents, whom she calls biological determinists, argue that we know sex differences in the brain are innate because they are evident even in young infants, before socialisation has had the opportunity to exert its influence. But according to Rippon, “the general consensus appears to be that, once variables such as birth weight and head size have been taken into account, there are very few, if any, structural sex differences in the brain at birth”.

She claims that the emergence of sex differences between boys and girls’ brains as they age is evidence for the role of brain plasticity and socialisation in shaping these differences – that is, if and when sex differences exist at all. If there is “a genuine sex difference, indeed an ‘essential’ sex difference, and hard-wired to boot, you might expect it to be present at birth or certainly to emerge pretty early thereafter”.

Plenty of popular science authors have taken a similar position to that of Rippon. Cordelia Fine, for instance, asserts that “the notion of fundamentally female and male brains or natures is a misconception”. In her 2017 book, Testosterone Rex, she writes: “In the first year of life, baby boys and girls provide little in the way of evidence that their brains are tuned to different radio stations of life” but “children see that the category of sex is the primary way that we carve up the social world, and are driven to learn what it means to be male or female.”

Let’s consider this argument more seriously. Across our lifespans, despite the fact that our genetic code stays largely unchanged, we develop in remarkable ways. We grow larger and we mature, cells and organs proliferate and become specialised for various purposes, our teeth erupt, fall out and are replaced. Many of these changes occur in predictable ways, because the patterns of the effects of genes are themselves regulated by our DNA. The genes that affect a trait at one point in time may not be the same ones that affect the trait later on, and the intensity of the effects of genes fluctuates in turn. 

None of this precludes the environment from influencing these processes either, so when we observe a difference between boys’ and girls’ anatomy or psychology that diverges as they age, we cannot immediately point to the environment as a cause for this disparity.

For example, can you think of any process that is largely innate that might cause boys and girls to diverge physically and psychologically as they grow older? An elusive word beginning with “p” and ending with “uberty” is curiously missing from the index of Rippon’s 358-page-long treatise.

It is worth noting that puberty is not the only period of time in which boys and girls diverge in predictable ways. Hormonal surges influence the organisation of neural connections in the prenatal environment, during adolescent puberty, and during a “mini-puberty” that occurs in the first few months after birth. These subtle differences in the anatomy of boys’ and girls’ brains that have developed very early on can also cause them to react differently to the same environments later on, without them needing to experience differences in sex hormone levels subsequently.

This crucial point is not missed by Lise Eliot in her book Pink Brain, Blue Brain, when she explains that “this mini-puberty in both sexes suggests neonatal hormones might also influence babies’ brains. Just as the surge of testosterone before birth apparently organises the brain for later male-type behaviours, so this neonatal surge might create a critical period for launching brain development down the boy or girl trajectory.”

When it comes to disentangling these causes, it seems we are at an impasse — if both innate and socialised factors can cause differences between sexes, how do we know which of them is responsible for an observed difference? The truth is, we shouldn’t be focused on age-related changes alone to inform us about the nature or nurture of sex differences. Simply looking at correlations between traits and hormones cannot elucidate these causes either, especially considering that hormonal levels can be both a cause of behavioural changes and a consequence of socialised environmental factors, such as nutrition and medication.

Instead, a more accurate way to understand what it means for something to be innate is to imagine the trajectory of an individual over time and how that trajectory might be resistant or sensitive to systematic changes in the environment. The trajectory’s resistance and sensitivity reflect its innateness and socialisation respectively. This perspective is long-established in the philosophical literature on biology.

So we might turn to evaluating how the same men and women might act if they were exposed to a change in environment – a change in socialisation, we might say. Plenty of studies that investigate this do indeed find effects of socialisation on children’s outcomes, including randomised controlled experiments, such as an educational intervention that changed boys’ and girls’ attitudes and behaviours to gender egalitarianism in different ways, and natural experiments, such as boys and girls responding differently to school exams when their stakes were increased. 

Fascinatingly, Rippon herself concurs with this perspective, saying that “your brain may start out on a fairly standard trajectory but can then be diverted by quite small shifts” due to “different events or experiences”. But this does not stop her from making wild leaps in reasoning and frequent insinuations that when sex differences are not apparent at birth, they cannot be innate. When research suggests that 13-18-week old babies exhibit a sex difference in eye gaze behaviour, but newborns do not, she concludes that “social learning may be the primary impetus of the development of gender differences”.

Rippon exhibits a very transparent bias towards any result that confirms her views. It’s difficult to untangle all the factors that influence our cognitive processes, but easy to selectively criticise or minimise findings that contradict our views and uncritically accept those that do not.

The most egregious example of this one-sidedness is her discussion of functional magnetic resonance imaging (fMRI) studies. fMRI is a technique that attempts to detect changes in brain activity in response to a stimulus. In the fourth chapter of The Gendered Brain, Rippon extensively lists the limitations and difficulties that scientists face when conducting fMRI studies and interpreting their results. In fact, she brilliantly explains how difficult it is to find robust examples of sex differences in brain activity using fMRI, pointing out the number of arbitrary and potentially exploitable decisions that researchers have to make to construct brain images, the often small sample sizes, the publication biases, and so on.

Yet only two chapters later, she draws heavily on exactly the same kinds of fMRI studies to describe how socialisation can influence our brain activity through social rejection and stereotype threat – without the slightest critical evaluation, or any explanation of why these methods should be more credible when they support the effects of socialisation rather than sex differences.

Stereotype threat, incidentally, is a topic that Rippon frequently revisits to demonstrate the effects of socialisation on behaviour. It is the idea that informing individuals that people have a negative stereotype of their performance on a task causes them to then perform worse on that task. She states that “stereotype threat has also been shown to have a powerful effect on women, particularly with respect to performance on subjects such as science and maths.” She believes that, “stereotyping the kind of toys that are ‘for girls’ or ‘for boys’ can affect the range of skills they acquire; girls who think Lego is for boys are slower at construction-based tasks.”

But Rippon mischaracterises the findings of the study she cites on the effects of stereotype threat on boys and girls’ performance on a LEGO block construction task. In contrast to her portrayal, the authors describe their main finding in the paper as such:

“Contrary to our hypothesis, girls in kindergarten through third grade were not slower or less accurate in stereotype-threat conditions compared to a control condition [at constructing shapes using LEGO blocks]. They were, however, significantly slower than boys of the same age.”

And apparently unknown to Rippon is that stereotype threat is fairly widely-known to have been afflicted by the replication crisis, with its research suffering from publication bias, its results highly dependent on arbitrary decisions made by researchers, and notably, its failures to replicate findings relating to maths and science performance, the particular findings she draws on.

On the occasions when Rippon evaluates some of the simplistic claims made by critics, her scrupulousness and insight shines through, and the real shame is that she fails to apply this standard of rigour to any research on the effects of socialisation. Just like the video clips attempting to show how “Jordan Peterson debunks white privilege”, the most consistent feature of The Gendered Brain is this reckless, unrelenting one-sidedness.

The trouble with these debates is not simply that they tie people to a conclusion and make them work backwards, cherry-picking the evidence to bolster their arguments, but that they give people the impression that every argument and every line of evidence must fall neatly on their side of the debate. It is as if conceding on a single point is akin to surrendering, or that thinking up a clever but shallow ‘gotcha!’ is sufficient because it humiliates opponents, causing their standing to crumble like the lightest touch to a house of cards.

So while Lise Eliot might believe that the “basically unisex brain” is “no more gendered than the liver or kidneys or heart”, and Gina Rippon might contend that this book “shatters the myth of the female brain”, the only thing that has been shattered here is any faith I had that debates of this kind could help us arrive at the truth at all.

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