Read on Twitter
Ok, I'll compose a tweet thread here as I work my way through @nigelshortchess's article "A beautiful minefield" where he continues to make a strong claim about sex differences in the brain as the strongest candidate for explaining chess skill differences between men and women
The article itself is reproduced here for those who want to read it: https://www.ecforum.org.uk/viewtopic.php?f=2&t=11358&start=30 (thanks to @ChessProblem for the link).
This paragraph seems to be the basis of most/all of Nigel's claims about chess skill/ability. So let's think some more about this. Before we begin, I'd just like to point out that if this were an assignment, my students would lose marks for not citing proper references here.
Because to evaluate the very basis of his later claims (which are a huge leap from this "basis" of sex differences in the brain btw), we need to look at the source material.
Ok, now "men have roughly 6.5 times more grey matter; women have 9.5 times more white matter" is the first claim. This seems to be based on this 2005 study: https://www.sciencedaily.com/releases/2005/01/050121100142.htm#:~:text=Study%20results%20appear%20on%20the,related%20to%20intelligence%20than%20men.
Here's a pdf of the original article, you all should click on the link and at least read the abstract: http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.529.4597&rep=rep1&type=pdf So you'll understand why it is important to go to the source material.
From the abstract "...suggesting that there is no singular underlying neuroanatomical structure to general intelligence and that different types of brain designs may manifest equivalent intellectual performance."
The study was apparently done using data from men and women with equivalent performance on intelligence tests. If you go further into the methods section, you will see that there are 20 odd subjects that went into a correlation analysis. This is an extremely small sample.
I can dig deeper into the specific IQ-brain volume correlation analysis they did, but I don't think it is necessary, since we already know that the authors themselves concluded that these brain differences likely are just different ways to achieve similar intelligence.
Now, even that last bit could be debatable, but the fact is there is unlikely to be strong agreement even amongst the experts, I don't think we have any conclusive data yet on this but I could be wrong. Please share if you know of studies that have successfully made this leap.
Ok, next sentence in Nigel's article: "The latticework of synaptical connections between the two hemispheres is denser in females than males." -- hmm cool! -->
Again no citation, but even if we take this at face value, how do you make the inference that denser connections leads to worse chess skills? Count me perplexed, amazed, mystified (Nigel can probably come up with more exotic synonyms).
Ok two sentences in, this is a lot more work than I thought, have to tend to family stuff, will be back in a bit.
Ok next up: "Sexual dimorphism is noticeable in the hippocampus, the hypothalamus and the amygdala. Male brains are also 10% larger on average" -- so the idea here seems to be the bigger something is the better. ;) I know Nigel loves that sort of thing.
So first let's talk about the bigger brain = better idea. This study for instance finds that overall brain volume accounts for about 2% of the variability in fluid intelligence test scores. It is a well done study. https://journals.sagepub.com/doi/10.1177/0956797618808470
Now this might seem like a small number and it is (implies that there are potentially many other factors we aren't looking at that explains intelligence), but it cannot be ignored.
This is a robust effect, the study was pre-registered, meaning, there are fewer possibilities of confounds and data fudging and publication bias issues. In fact, the effects observed here are weaker than the ones reported by large meta-analyses for these very reasons.
Ok, so this raises the question about brain volume differences between men and women. Like I said however, something that has a tiny (albeit robust) effect is not where you'd typically look for first when trying to explain big differences in something like Chess ELO.
So when people try to make a huge leap between these things, it always comes across as laziness and a lack of willingness to consider inconvenient but potentially more powerful explanations. I'll explain more:
We know that body height and brain volume are heritable. Now, let's choose a behavior (like affinity for books). So now you introduce nurture as well into the equation. We also know that while body height, brain volume, etc are heritable, there are also environmental influences.
So over and beyond the tiny effects you observe in brain size - intelligence studies, you have all these complexities you need to think about.
Now coming to difference in size of different brain regions (Nigel talked about the hippocampus, Amygdala, etc), firstly, ascribing things like memory, emotion, etc to individual brain regions is problematic.
The brain is a distributed networks where many functions are enabled by concerted processes in different regions. That said, different regions do have some functional specializations. One of the most robust effects in neuroscience in this regard is face processing.
There are specific regions in the brain that respond very robustly to faces, and these regions tend to be larger in men, but all available evidence suggests women do better on face processing tasks -->
(at least as adults, the pattern seems to be the reverse in infants: https://journals.sagepub.com/doi/10.1177/0165025412472411).
But again, I don't have a good grasp of this literature to know how robust these findings are, but this just goes to show you how you cannot make an easy leap from even a robust and strong effect in the brain to behavior.
https://www.pnas.org/content/117/31/18788 for instance is a recent study that shows reproducible sex differences in the brain, but men have greater grey matter volume in some regions and women in others. Again, the leap to behavior is extremely problematic to make from these.
Let me also explain further why: the fMRI literature is f***ed up. While there are some groups that do good work, the majority of it is the modern equivalent of phrenology. They essentially get people to do some tasks, do statistical contrasts of fMRI images.
... look at what regions "light up". Then to make sense of these results, they turn to previous studies. Then they say things like "oh region X is found to light up in tasks 1, 2, 3..." (btw they can easily ignore other correlations in the lit that don't fit their narrative).
This has led to a proliferation of narratives about brain regions based on both voodoo and real correlations. But that is a somewhat tangential rant but one that is relevant for why it is super hard to go from structural brain differences to talking about complex cog skills.
So from the PNAS study linked above, men have higher grey matter volume in some visual regions and subcortical regions, whereas women do in prefrontal and parietal cortices.
Now if you look at the fMRI literature, you'll find literally hundreds of functions that can be ascribed to these regions. This is why you need to a lot of work (scientifically) to be able to make a leap from structural differences to functional.
The original studies Nigel seems to have used to support his favored claims themselves found no differences in actual behavioral/cognitive performance corresponding to the structural differences they reported.
Finally Nigel says: "Circumstantial evidence suggests women are inherently less interested in the game. Given how early this divergence starts, the phenomenon is unlikely to be explained wholly by nurture." -- again, citation? Really difficult to evaluate assertions.
How early? What studies are you referring to? Anecdotally, it actually seems to be the opposite based on what I've heard chess coaches say about participation rates of girls vs boys very early on, but I don't want to deal in anecdotes. Show me the papers and I'll look at them.
So I don't have anything more to add there. I'm going to stop now because no matter how hard you try to drive sense into these people, they seem to carry on as though nothing ever happened. It's as though they're hunting for anything that'll support their preconceived conclusions
I could go on forever, but this should be sufficient to explain my evaluation of his claims and claims like these. /fin
