Sex on the Brain
Yes, men and women's brains differ. No, this has no political implication.
Posted Apr 11, 2019
Imagine someone you admire—morally and politically. If it helps, picture Martin Luther King, or the Dalai Lama. Maybe it’s a family member who convinced you, by their words and deeds, that they were committed—deep down where it matters—to the moral unity of humanity. To the decent treatment of all, to kindness as the guide to interactions with others. Now, imagine this person coming across a surprising fact in a neuroscience or genetics textbook. Something that they didn’t know, that for example, the corpus callosum of women is thicker than it is in men, or that red-headed people alone have two recessive copies of the MC1R gene. They look up from the book, their faces ashen. Realizing that their lives up until now have been based on a lie, they stalk the earth, repudiating their earlier exhortations to treat one another as equals. Their eloquence and passion brings followers in their wake. Followers who had previously been treating their neighbor as themselves, giving back good for evil, and consistently fighting for social justice. Not now. Now these previously decent people call for segregation. Internment of the deviant. Even darker things.
Such a vision is grotesque. And, I put it you, if you find it absurd that previously decent people could upend their lives and repudiate their morals on the basis of a contingent (probably contentious) and highly technical scientific claim then this is because it is absurd. Do your moral codes rest on such contingent factual claims? Does your decent treatment of your fellows hang by such a slender thread? Gawd help the rest of us if you open the wrong book at the wrong time…
Saying that people deserve to be treated decently is not a factual claim. You can’t look it up in a textbook, and no amount of brain-scanning is going to reveal why it’s true. People have been either succeeding (or more often failing) to treat each other kindly, fairly, and honorably, since before there was science, since before there were people really. And—they will continue to try (and often fail) far into the future, whatever science reveals about our natures.
If I am trying to help a child understand why stealing from another child was wrong, or that they should share the sandpit, or apologize to that other annoying (and now crying) kid…yes…I know he took your dolly, but you still can’t hit him with that Lego dinosaur… Well, I don’t get out my copy of Eric Kandel's Principles of Neural Science, and start pointing meaningfully to the diagram of Brodmann area 11 in the prefrontal cortex.
All the foregoing seems blindingly obvious. However, the corollary: That you don’t need neurological backup to argue that you should treat people fairly, seems lost on writers like Cordelia Fine and Gina Rippon. Both are trying to argue that humans are neurological hermaphrodites, as if somehow admitting any sex differences in brains would mandate the unfair treatment of women.
Gina Rippon is back to “debunk” neuroscience with her latest, The Gendered Brain: The New Neuroscience That Shatters The Myth Of The Female Brain. It is tempting to rebunk these debunkings but, if I am right in my guess about what is going on here, no amount of factual piling on is going to help. In fact—it may make things worse, because it’s going to convince writers like Fine and Rippon that some hideous conspiracy is occurring and, like some horrible feminist version of Alex Jones, that the whole of brain science is fake news. Let’s stop things before they get out of hand.
Fine and Rippon have decided that women are often not treated fairly. No argument there, they often aren’t. We (almost) all agree on this. But they have decided that the way to counter unfairness, is to claim that men and women are neurologically identical. No. They aren’t. This is silly, and it’s got to stop. It’s hurting people. And it’s getting out of hand. A 2017 issue of Neuroscience Research devoted an entire issue to detailing large, repeatable, sex-typed brain differences that have clinical significance (If you want a partial list I’ve prepared one below—and brace yourself because it's long) because they were concerned that this sort of politically-motivated science denial was hindering medicine. Nature recently penned an anguished rebuttal to its earlier review in support of Rippon.
All of that factual back-and-forth is important (although it must be danged confusing to non-specialists watching from the sidelines) but, if my guess is right this is going to make Rippon et al. double down and come back with yet more "debunkings." This is because they have confused facts and values. So—let’s address that directly.
Do they really think that chauvinists and bigots are leaning back in their La-Z-Boy recliners, reading the latest issue of Neuroscience Research, and going “Heck woman, it sez here that the female olfactory bulb is right 40% more neurologically dense than the male one. By the sacred jockstrap of Jordan Peterson, I did not know that! Now get into that kitchen and make me a sammich!”?
Less facetiously, they have become confused by the fact that, historically bigots, have (and still do) take weird factual claims about sex differences morally seriously, and come to the conclusion that the way to address this is to attack those claims. But it’s naïve to think that those factual claims, rather than the desire to treat people unfairly, were the cause of the behavior, rather than the consequence. If you “debunk” those facts the bigots aren’t going to go away. They will find new reasons, invent them if they have to, and ignore the whole of science if they must. You can see them doing all these things right now. What I’m saying should not, therefore, come as a surprise. Why does this matter? Because failing to treat sex differences as real means that things like drug dosages, disease susceptibility, and differential diagnoses, are being swept under the carpet.
Sexual dimorphism does not mean that males and females are different in every respect. It means that sex is a meaningful variable that allows us to predict differences. Brain differences. Go and look at that list I made below. I’ll wait. And consider what would have to be true for sexual dimorphism not to apply to brains. It would mean that an entire chromosome, which has about 800 genes on the X bit, and 70 on the Y, has no effect on the resultant organism and its control center. Evolution just doesn’t work that way. Evolution couldn't work that way.
But, you don’t have to be a neuroscientist to see that men and women’s brains have to be different. Their bodies are different. Not as different as some sexually dimorphic species—but different nonetheless. Brains control bodies. For those brains to be indistinguishable, would be like saying that any TV remote should control all other TVs. Of course, there are similarities—more similarities than differences—but (and this is the really important point): So what? Put it this way: What systematic brain difference would mandate treating half the human population as inferior to the other half? Name one. I dare you. I double dare you.
And if sexual dimorphism doesn’t convince you—try heterosexuality. Most of us fancy the opposite sex (most, not all, there are very interesting variations but they don’t affect the central tendency or my argument). “Fancying the opposite sex” is not a single brain state. For males to find females attractive, they have to be attracted to female-typical bodies. For females to find males attractive, they have to be attracted to male-typical bodies. Now, let me say this slowly and carefully, these are not the same bodies. Therefore, the systems (brains) that attract us to them (bodies) can’t be exactly the same either.
However, if recent experience is anything to go by, simply elucidating facts is not going to stop this daftness going away. What might make it go away is if we all do better at treating each other fairly and decently. And doing that is a lot harder than having an ideology.
A (partial) list of reliable and robust sex-based brain differences all showcased in the January 2017 Journal of Neuroscience Research. Bear in minds that most of these are meta-analyses, summaries of dozens (sometimes hundreds) of other studies.
Responses to ischemic stroke (Dotson & Offler, 2017); sex-dependent gene expression of activity-dependent neuroprotective protein (important in the response to Alzheimers, autism and schizophrenia and is evident in humans, mice and birds; Gozes, 2017); sex-specific hormones affect huge numbers of brain functions (for instance estrogen affects functions in the hippocampus, prefrontal cortex, cerebral cortex, nigro-striatial pathway, mesolimbic dopamine pathways, paraventricular nucleus, brainstem and Periaqueductal grey and cerebellum with functional differences detectable in, among other things, learning and memory, excitability and seizures, neuroprotection, addiction, cardiovascular regulation, pain sensitivity, fine motor skills, co-ordination and reaction time McEwen & Milner, 2017); decision making in rodents (Orsini & Setlow, 2017); fear responses (Merz & Wolf, 2017); various stress responses and social defeat in rodents (Laman-Maharg & Trainor, 2017); face processing (Proverbio, 2017); relative corpus callosum size (greater in females and implicated in sex-typed patterns of social behavior, Holloway, 2017); gustatory function (Martin & Sollars, 2017); sex-dependent brain regions and the actions of oxytocin or vasopressin (Rubin, Yao, Keedy, Reilly, Bishop, Carter, Pournajafi-Nazarloo, Drogos, Tamminga, Pearlson, Keshavan, Clementz, Hill, Liao, Ji, Lui, and Sweeney, 2017); sex differences in number, morphology and signaling of immunocompetent brain cells (Nelson & Lens, 2017); cortical area, brain volume and white and gray matter volumes in adolescents which were all assessed as being of large effect size and more different in terms of effect size than all other measures of body changes at adolescence apart from voice differentiation (Paus, Pui-Yee Wong, Syme, and Pausova, 2017); detectable differences in the development and aetiology of Alzheimer’s disease (Pike, 2017); responses to hypoxia-induced brain damage (Netto, Sanches, Odorcyk, Duran-Carabali, and Weis, 2017); sex-differentiated effects of decision-making following damage to the ventro-medial prefrontal cortex, Reber & Tranel, 2017); sex-based differences in spatial-tasks (males typically higher) and verbal tasks (females typically superior)(Gur & Gur, 2017); chronic pain responses (Rosen, Ham, & Mogil, 2017); and brain alterations across pain conditions (Gupta, Mayer, Fling, Labus, Naliboff, Hong, and Kilpatrick, 2017); responses to particular drugs that limit brain-damage following injury in males, but not females (Cahill & Hall); sex differences at the level of synapses (Dachtler & Fox, 2017); cortisol responses to social stressors (Reschke-Hern-andez, Okerstrom, Bowles Edwards, and Tranel, 2017); underlying neural differences in stress-responding structures (Seo, Ahluwalia, Potenza, and Sinha, 2017); glial cells in their opioid-receptor response (Doyle & Murphy, 2017); type and susceptibility to various forms of epilepsy (Reddy, 2017) and strokes (Sohrabji, Park, and Mahnke, 2017); functional cerebral asymmetries (Hausmann, 2017); nicotine preference (Pogun, Yarabas, Nesil, &Kanit, 2017), including differneces on the developing brain (Cross, Linker, & Leslie, 2017); responses to parenting (Sundstrom Poromaa, Comasco, Georgakis, and Skalkidoul, 2017); sensitivity to corticotrophin-releasing factor, implicated in cocaine addiction (McRae-Clark, Cason, Kohtz, Santa-Maria, Aston-Jones, and Brady, 2017); other forms of addiction (Becker, McClellan,& Glover Reed, 2017); in other primates sex differences in physical and social development, play, grooming, nursing, foraging and the manipulation of objects (Lonsdorf, 2017); brain-derived neurotropic factor (Chan & Ye, 2017; Wei, Wang & Xu, 2017); hippocampal structure and function—especially important in memory (Koss & Frick, 2017); neuro-immune modulation of memory (Tronson, & Collette, 2017); attentional bias towards negative stimuli—important in predicting mood disorders (Victor, Drevets, Misaki, Bodurka, & Savitz, 2017); social brain differences and how their complex interactions with gendered expectations (Pavlova, 2017); the interaction of hormones on psychiatric diseases across the range of behavior (Gobinath, Choleris, and Galea, 2017); specifically epigenetic processes underlying depression (Hodes, Walker, Labonte, Nestler, and Russo, 2017); rumination differences in depression (Shors, Millon, Chang, Olson, & Alderman, 2017); the visual and auditory processing of data when mediated by fearful or peaceful moods (Yang & Lin, 2017); the processing of visual information at all levels (Vanston & Strother, 2017); the mediation of voluntary physical activity—conserved mechanisms across humans and rodents (Rosenfeld, 2017); differences in Broca’s region—specifically the local grey-matter regions of Brodmann areas 44 and 45, important in verbal processing (Kurth, Jancke, & Luders, 2017); migraine—which is significantly more common in women than men (Pavlovic, Akcali, Bolay, Bernstein, & Maleki, 2017); psychiatric disorders which are significant sex-linked, such as autism with males and depression with females ( Jahanshad, & Thompson, 2017); even where there are atypical sufferers the underlying neural structures can be different (Lai, Lerch Floris, Ruigrok, Pohl, Lombardo, & Baron-Cohen, 2017); how each sex forgets words (Kerschbaum, Hofbauer, Gfollner, Ebner, Bresgen, & Bauml, 2017).
Sex is a biological variable — in the brain too Rhonda Voskuhl (April 2019) https://www.nature.com/articles/d415Neurosexism: the myth that men and women have different brains86-019-01141-6?fbclid=IwAR21UnJF2R3FAR4N2abT5zDGPbC0k51bM9zN2tNL6BjEwQXILcPZCnV1e7Y
Fine, C. (2017). Testosterone Rex: unmaking the myths of our gendered minds. Icon Books.
The Gendered Brain: The New Neuroscience That Shatters The Myth Of The Female Brain Gina Rippon The Bodley Head (2019)