I clearly need to read this Delusions of Gender... a lot of stuff like "men are better at visual/spacial" rings hollow for female-bodied me, who is possibly the best at visual/spatial stuff in the house, and the idea that men are less emotionally vulnerable and cry less seems silly too when I think of the number of guys I know that openly cry during movies! Maybe it's part of me being androgyne that I have traits of both but I'm still curious about the *actual* science--of what is more "hard-wired" and what is more cultural.
I think you can only say, in a scientific way I mean, that there are tendencies towards something. For instance, males have better upper body strength than females. BUT you have females who have awesome upper body strength that is probably higher than an average male. But that female (and I am thinking of one) is probably on the 95%+ of the range of upper body muscle strength for females. 3D visual skills are most likely a tendency as well. I have no problem whatsoever with this part, but I do still wonder re: socialization and so forth.
One thign that would be build 3D visual skills would be manipulation of toys and so on. Since boys tend to be socialized to play more actively they would have more opportunities to engage their brains in this way. Meanwhile girls will play more with toys that require language (dress up, dolls, etc.), so girls would tend to engage their brains more in this way. I think you could take each area that they have found difference in tendencies and pull it apart that way. Including upper body muscle strength-- active toys, being engaged with physically as children, etc.
I think there are now enough parents that raise their children in more androgynous ways that you could actually start trying to tease this apart a bit. I played equally with stuff like trucks, blocks, and dolls (actually since my dolls acted out adventure themes, I had action figures. :-))
I feel my 3D visual skills are only poor because I have a learning disability, but again we can't make generalizations on one person.