I think the article is specifically making a point about girls playing BOYS, though. It's not that girls are not competitive--it's that when they play boys, they get it into their heads that they are going to lose (because "boys are better at chess"). So they do, even when favored to win.

I don't know exactly what makes someone good at chess, but judging by my own spectacular ineptitude, I'm pretty sure that spatial skills, and specifically spatial planning and rotation skills, are very important. This is an area where I am significantly below average and probably even LD. I actually think my DD is stronger in math than my DS, at least judging by comparing their math progress and interest at the age of 5/6, but DS is definitely the more gifted chess player.