This thread has reminded me of the Dar Williams song "When I Was a Boy" (think that's the title). I too have observed what seem like gender differences in very young children, but as a kid, I was much more boyish than some of the neighbor boys, and some of them were more girlish than I. But even that statement assumes a certain pre-existing "boyishness" and "girlishness" that I don't know are completely justified. I don't have a clue about this, really--but I do like the song.

I won't forget when Peter Pan
Came to my house took my hand
I said I was a boy
I'm glad he didn't check

I learned to fly, I learned to fight
I lived a whole life in one night
We saved each other's lives out on the pirate deck

And I remember that night when
I'm leaving a late night with some friends
And I hear somebody tell me its not safe, someone should help me
I need to find a nice man to walk me home.

When I was a boy, I scared the pants off of my mom,
Climbed what I could climb upon
And I don't know how I survived,
I guess I knew the tricks that all boys knew.
And you can walk me home, but I was a boy, too.