The brunt of Schaffer's argument seems to be that since men and women have roughly similar outcomes for any given mental task, therefore we must be using roughly similar processes to achieve those outcomes. But there's no reason to believe that's true.

She needs to better define the question she's addressing. Is it whether or not sex can be a predictor of one's capability to perform a certain task (I'd agree that it isn't) or the larger question of whether or not men and women think differently, even if we are equally competent at the end of the day?

--s