So Elizabeth and I were discussing Warcraft raiding techniques this morning, and she said to me at one point, "why are boys not as smart as" - she actually used the term "dumber than" but I'm trying to be politically correct here - "girls? They don't start out that way ... it happens later.'
My first reaction was, hormones. If that were true, the gap ought to open up around puberty. However, she thought it started earlier, during elementary school, and I was inclined to agree. I suspected a social cause.
So what happens during elementary school? Boys and girls go to the same classes, after all. They're only separated during gym classes, when boys are encouraged to participate in sports. Ball games, in particular.
So now you know. As soon as a kid touches a ball, he gets dumber. Every moment of continued contact thereafter causes additional loss of intelligence. Be warned.