Guest post by George Felis

As usual, the journalists and even the scientists themselves are either confused or simply deluded about what this research actually demonstrates. There is exactly NOTHING in this research that offers the slightest evidence that might differentiate between learned and innate differences, but the journos and even the researchers (who damned well ought to know better) just assume that this represents innate differences between the sexes. Human brains are shaped by an entire lifetime of experiences: all of our learning and interactions and socialization create and reinforce neural pathways. Given all the differences in how boys and girls are treated even from infancy — the very different worlds they live in and navigate — it would be utterly astonishing if we didn’t see these differences with technology that allows us to examine details of how brains are wired. That does not mean those differences in wiring are inborn or fixed in any way.

In fact, when I looked at the paper itself, I found the biased assumption and willful misinterpretation of data in favor of innate differences right there in the abstract: “The developmental trajectories of males and females separate at a young age, demonstrating wide differences during adolescence and adulthood. The observations suggest that male 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.”

That description — although it’s subtly de-emphasized by the phrasing, it’s clear that the things they were measuring in brains are more alike in younger children and grow more different between the sexes as the children grow older — sounds EXACTLY like what one would expect if the differences were a response to the experiences of humans growing up male vs. humans growing up female. If the differences were actually innate in the brains based on sex, why would they be more similar in younger children and grow more different over time? It’s possible that these brain changes are tied to differences in sexual development, perhaps tied to adolescence, but it’s not obviously true. Nor is it a sensible default assumption at all; it’s just as likely and probably much more likely that the differences are the result of learning to adapt and respond to an environment where boys and girls are treated very differently and encouraged to behave in very different ways. But the researchers instead leap to the completely unwarranted conclusion that male and female brains are separately somehow “designed” (genetically, by evolution) for the things they are much more likely to be learning to do differently with time and experience.

Here’s the plain truth, stated simply: The default hypothesis to explain ALL brain differences between non-infant humans should be learning and experience shaping the developing brain, because we know for a fact that the brain is astonishingly plastic and is overwhelmingly shaped by experience. Assuming the exact opposite from the start — especially when faced with evidence that clearly suggests learning over time — is transparently unscientific, and says much more about the biases of the researchers than it does about differences between sexes.

Nor does their data examine and emphasize variation as a primary phenomenon, which anyone engaged in any kind of biological research should always do. I don’t have the time or inclination to dig into this paper’s data and crunch numbers, but even without looking at it I’m willing to bet good money that individual variation largely swamps the differences between sexes in this data set. That is, if you laid out the degrees of between-hemisphere connectivity numerically from least to most connected and divided it into two groups at the median, there would be slightly more females than males on one side and vice versa on the other — but the ratios of females:males on the two sides of the median would be much closer to 20:19 and 19:20 than 2:1 and 1:2. In other words, it would still be the case that lots of females have fewer between-hemisphere connections than lots of males, even though females have slightly more such connections on average as a group. That’s what individual variation swamping group differences looks like when you look for it — and that’s what almost all sex difference data looks like when you examine it without the explicit goal of seeking out and emphasizing between-sex differences. But sex-difference researchers never do that, because of the agenda they (unconsciously or consciously) buy into when they set out to look for sex differences in the first place.