I simply gave reasons why it is plausible based upon a widely accepted difference in spatial ability between boys and girls. And the response I have gotten back is that you think the studies are invalid. Possible, but wouldn't there be numerous recent studies pointing the other way by now?
No, for the simple reason that it's just not possible to control for all the cultural factors, so you can't do a study using a control group that does not exist.
However, we DO know that cultural attitudes about gender stereotypes have been changing over time, and we've seen that the performance gap changes over the same time period. We also know that cultural attitudes about gender stereotypes are different from culture to culture... and sure enough, we find that the performance gaps reflect those different attitudes as well.
So basically, we've proven beyond reasonable doubt that stereotypes play a significant role in gender differences in math, and in chess. We know that as attitudes skew closer to equality, the performance also skews closer to equality. That's a closed case.
All that's left now is to hypothesize about an imaginary culture in which no gender stereotypes exist, would some biological factor pre-select males for dominance at the very highest echelons of math and chess?
My hunch is: no.
