My understanding is that spatial ability is a reason why the strongest boys still do better in math than the strongest girls, even though girls are generally doing better in school than boys these days.
Re girls and math, I believe we've been through this before--but as a refresher course, and from memory (so I may be off slightly), girls now outperform boys, on average, on standardized math tests in elementary schools. There has also been a MASSIVE improvement in their performance on the SAT and on other measures with higher ceilings over the last 30 years--truly massive. The number of women majoring in math has skyrocketed as well.
On measures that assess the really high ends of math performance, I believe boys used to outscore girls 20 to 1, but now it is 4 to 1, and in some countries and populations, 2 to 1. International studies show that the # of girls who compete in extremely elite math competitions varies wildly by country and in fact, appears to correlate somewhat with the situation for women in that country.
I've said it before and I'll say it again: I don't completely reject the possibility that boys and girls (men and women) have some innate differences in verbal and spatial abilities, but we have NO ABILITY to know what those differences are yet due to entrenched sexism. There is NO REASON to assume that we have suddenly, just NOW, reached the point where sexism doesn't matter and all of that has fallen away to show us true natural abilities. People thought that in the '80s, when boys were outscoring girls 20 to 1. Please.
Anyway...regarding chess. As aquinas has eloquently stated, the differences in the tails in no way explain the gross inequities in mass representation at chess clubs and competitions.
And for an example in my own life, my father taught both of my brothers to play chess, but not me. Now, maybe he suspected I would be bad at it (I am). But while one of my brothers likes the game, the other is just as incompetent and uninterested as I am (he's a words person, like me).
