Over the last few years a lot of "scientific" literature (or, at least, science-based literature) has claimed that boys are girls are different because their brains are different. As it turns out, that's not true. Caryl Rivers and Rosalind C. Barnett write in the Boston Globe:
In the past decade, such claims have coalesced into an almost unshakable conventional wisdom: Boys and girls are different because their brains are different. This idea has driven bestsellers, parenting articles, and even - increasingly - American education.
The problem is, a hard look at the real data behind these claims suggests they are simply untrue. Some of them are baseless, using the language of science to cloak an absence of serious research; others are built on tenuous studies, with methodological flaws and narrow margins of significance. More and more, they are simply coating old-fashioned stereotypes with a veneer of scientific credibility.
It's a long-ish article but it makes a good read. The two authors are currently working on a book called "The Truth About Boys and Girls: How Gender Stereotypes Harm Our Children". That should also be good to read.