Of Course It's Biological

Every few months, a new MRI study finding differences between male and female brains is published, which invariably leads people to comment that it disproves the “blank slate” theory of sex differences in psychology. If men’s brains are wired differently than women’s brains, so the argument goes, it shows that despite what feminists claim sex differences in psychology are not environmental but biological. If men and women are psychologically different, it’s not because boys and girls are socialized differently, it’s because they’re different to begin with. To be clear, I completely agree that sex differences in psychology are not just environmental and this post is not intended as a defense of the “blank slate” theory of sex differences in psychology, but the environmental/biological dichotomy on which that argument rests betrays a profound and widespread conceptual confusion. Indeed, every psychological difference is biological, so merely pointing out that men and women have different brains doesn’t tell you anything about why men and women are psychologically different.

The reason is that humans are biological creatures and their psychology therefore has to be rooted in biology somehow. More precisely, if people differ psychologically, it has to be because something in their brain is different.¹ Thus, even if psychological differences between men and women were entirely the product of culture, they would surely manifest themselves in the brain somehow, because how could there be psychological differences between them unless their brains were different? Ultimately people’s psychology depends on the electro-chemical reactions in their brain. Even in a world where sex differences in psychology are completely environmental, if people looked at male and female brains with MRI, they would still find differences between them, otherwise there wouldn’t be psychological differences between men and women. This is true for psychological differences between men and women, but it’s also true for psychological differences between other kinds of groups and for differences between individuals.² If there are psychological differences between people, it can in principle be traced back to biological differences between them and more precisely between their brains.

At the end of the day, we are sacks of meat, so e. g. the cognitive differences between Einstein and you have to come down to the fact that your “meat” is somehow different from his. But this doesn’t tell you anything about why it’s different and how this explains the fact that Einstein was a genius and you’re not.³ In general, we know that both genes and the environment affect our psychology, but we don’t know much about how exactly. For instance, no matter where you stand in the debate on nature vs. nurture, there is no doubt that how people are raised affects their psychology, but the mechanisms are generally not known, at least not at the biological level. What is certain, however, is that to the extent that people’s education affects their psychology it has to do so ultimately by affecting their biology and more specifically their brain. As most trivial claims, this is not particularly interesting, but it’s nevertheless important to understand it to avoid the kind of mistakes people make when e. g. they use MRI studies to refute the “blank slate” theory of sex differences in psychology.

ADDENDUM: Based on some of the initial reactions to this post, I thought it would be useful to make a clarification. I'm obviously not saying that environmental and genetic explanations for neurological differences between people or groups are equally plausible, otherwise I wouldn’t be so convinced that the “blank slate” theory of sex differences in psychology is false and more generally that socialization doesn’t fully explain psychological differences between people (which I am), but to say that requires making the case that some brain differences cannot plausibly be explained by socialization. Now, this is different from merely pointing out that neurological differences exist, but usually that’s what people do. In general, I think they don’t give much or any thought to what extra assumptions they have to make to conclude that psychological differences don’t result from socialization and, if pressed on it, they would be incapable of explaining why they think neurological differences can't plausibly be explained by socialization.

1. This doesn’t mean that psychological differences between people can’t ultimately be due to differences in other parts of their body or even in their environment, cf. the extended mind thesis, but the causal effect of such differences would presumably be mediated at least in part by differences in the brain.

2. When they engage in that kind of debates, the dichotomy people are really getting at is not the biological/environmental dichotomy, but the genetic/environmental dichotomy or the innate/acquired dichotomy. Incidentally, the last two also shouldn’t be confused, since for instance differences in intra-uterine environment could result in innate psychological differences between people who are genetically identical, but that’s a story for another time.

3. I’m assuming that you’re not a genius, at least not of the Einstein caliber, but apologies if you are.