Uta: Cordelia, you just published a review article in Science, His brain, her brain? where you argue that it is far harder to interpret gender differences in the brain than people think. And it’s a call for more rigorous science in the field. Now, your paper with Gina Rippon, Rebecca Jordan-Young and Anelis Kaiser earlier this year lays out in some detail what rigorous research designs would actually involve. I would love to know a bit more about why you wrote it.
Mary Cassatt (1878) Woman reading Le Figaro: Courtesy of www,marycassatt.org
Cordelia: We wanted to write something positive about how research in this area could be done better, so we got together to write a paper that would be helpful to researchers, editors, reviewers and science communicators. We wanted to make a constructive contribution. After all, there has been a lot of controversy in this area,
Uta: You can say that again! The papers that report gender differences are almost always suggesting that women’s brains work differently, aka less well. So half the readers say, “At last there is some hard evidence for differences that are blindingly obvious”, and half say, “Of course we know that women and men are equal and there are no real brain differences, and this research must be hopelessly biased.” I expect you call the first position “essentialist”, because it presumes that being female means being one kind of thing, being male another, forever. It’s the forever bit that makes it suspect.
Cordelia: Happily, the perspectives are definitely not that polarized. One thing that’s worth stressing though is that criticisms of this area of research don’t stem from a belief that it’s intrinsically problematic to look at the effects of biological sex on the brain. But implicit assumptions about female/male differences in brain and behavior do influence research design and interpretation. They do this in ways that can give rise to misleading conclusions that additionally reinforce harmful gender stereotypes.
Uta: It would be strange to rule out this type of research on the grounds that it is bound to reinforce gender stereotypes. We can be aware of their influence and take them into account. But we need to be fearless when we read Nature’s book. It does not always tell us what we’d like to hear. I worry about our tendency to be ultra-critical when the findings are against our fondly held beliefs. But isn’t science exactly about being able to overturn fondly held beliefs?
Cordelia: I certainly agree that we shouldn’t rule out particular kinds of research because we may not like the conclusions. The concern is with conclusions that are unwarranted – an issue of ‘scientific correctness’ rather than ‘political correctness’ – and the goal is not to be ultra-critical, but to make visible the implicit assumptions that are guiding research.
Uta: We tend to be less critical when a paper appears in a prestigious journal because we can assume that there has been a stringent peer review process. You discuss the controversial Ingalhalikar et al.’s structural connectome article published in 2013 in PNAS – a reputable journal.
Cordelia: This article measured brain connectivity in a large sample of 8-22 year olds, and found greater intra-hemispheric connectivity in males and inter-hemispheric connectivity in females, on average.
Uta: This sounds like a good sort of gender difference, at first glance it has nothing to do with a gender bias, but it certainly is grist to the essentialist mill. I remember when I first read this paper I was thinking, so there is now some evidence for an essentialist type sex difference, and we can start to think what it means.
Cordelia: In our article, we make the case that researchers are often working from an implicit ‘gender essentialist’ model, that assumes that the brains and psyches of females and males are highly distinct, and differences between them are natural, fixed and invariant across time and place. This subtly influences research design and interpretation, and the Ingalhalikar et al. study was a good example of exactly that.
Uta: So what’s wrong with that?
Cordelia: In an earlier study, the researchers had reported behavioural sex differences in executive control, memory, reasoning, spatial processing, sensorimotor skills and social cognition. This was in a larger sample from which these participants were drawn. But these differences were very modest: 11 of the 26 effect sizes were null/d<0.1, and the largest was d=0.33. Yet despite the substantial behavioural similarity between the sexes, the researchers interpreted their anatomical findings as underlying profound behavioural differences between the sexes, without actually testing for brain-behaviour correlations.
Uta: And what did you think of their interpretation of the brain differences?
Cordelia: They speculated that “[m]ale brains are structured to facilitate connectivity between perception and coordinated action, whereas female brains are designed to facilitate communication between analytical and intuitive processing modes.”
Uta: Perhaps they couldn’t think of what else the differences could be due to.
Cordelia: There were two other possibilities they might have considered, but didn’t, presumably because of the essentialist frame. One is that the female/male interconnectivity differences are a brain size effect, rather than a sex effect. As you know, the male brain is on average about ten per cent larger than the female brain. They also didn’t pay any empirical or theoretical attention to the possible influence of gendered experiences on brain and behaviour. I happened to be sent the article by a journalist for comment, and I wrote back to her:
“Ironically, even though the research from this group provides strong evidence for behavioral similarities between the sexes, provides no evidence that any modest behavioral sex differences are associated with neurological ones, and offers no information about the developmental origins of either, we can probably anticipate that this article will soon be drawn on by popular commentators as evidence that ‘hardwired’ sex differences explain why men are from Mars and women are from Venus.”
Uta: This is precisely what happened.
Cordelia: Yes. The front page of the Independent, for instance, headlined with “Scientists discover the difference between male and female brains: Study reveals variation in hardwiring which may explain skills gap between women and men”.
It’s worth pointing out though that this particular example was unusual for the role of the researchers themselves in making reference to ‘hardwiring’, and in making especially incautious reverse inferences to concepts far beyond any measured behaviours (like motherly intuition). Usually this is a job left to the popularizers.
Uta: Hardwiring usually means that there is a biological cause for a behaviour. But, as you say, it could be the other way round. The hardwiring could be a result of behavioural practice. There are plenty of examples of how learning changes the brain.
Cordelia: Yes, and long before the buzz about neuroplasticity, feminist neurobiologists were writing about this ‘entanglement’: the fact that the social phenomenon of gender (which systematically affects an individual’s psychological, physical, social and material experiences) is literally incorporated, shaping the brain and endocrine system. One of the recommendations of our article is for researchers to attempt to incorporate the principle of entanglement into their research models, including more and/or different categories of independent variables that include ways of capturing the role of the environment.
Uta: We clearly need more thoughtful research in this area: You and your co-authors have made a very constructive start with your paper.
Cordelia Fine is the author of Delusions of gender. She is ARC Future Fellow at Melbourne School of Psychological Sciences and Associate Professor at the Melbourne Business School and the Centre for Ethical Leadership, University of Melbourne.