However, I don't think that a child that young could possibly have a 'grass is greener' concept when it comes to gender- how could they possibly have the life experiences or perception to make that kind of connection?
You've never seen a young child throw his or her toy down because they suddenly notice another child's toy, and decided that's what they wanted to play with? It's human nature. Just because we've assigned complex names and concepts to it doesn't mean that they can't perceive of it in very simple terms, especially if somehow the message that gender is a choice, not an absolute, is somehow taught to them (through television, certain toys, etc.) One factor I've been noticing a lot lately is that the overall body language and non-verbal communication styles of men and women are becoming identical. After seeing that exampled by so many adults, it's easy for a child to not see that the distinction is one of much importance.
Something as simple as observing members of the opposite sex engage in something their own gender doesn't could trigger the kind of interest that would then make the child want to be able to be able to do that. The kinds of things we all take for granted, but may inadvertently be presented in a one-sided way to a small child. Mommy spends part of her day playing with the child, while Daddy is away "at work" and always comes home in a bad mood. Heck, that'd make me want to be a woman if that's what I saw every day. If Mommy is always frustrated while Daddy seems to be in control, then why wouldn't they want to be more like Daddy? If they see kids of the opposite sex doing fun things, but never kids of their own gender....
Another thing to remember is that it's not what toys the kids play with, but HOW they play with them. Ginny tended to gravitate to cars and trucks instead of dolls, but as she played with them, the cars and trucks talked to each other. When boys play, the toys make noises "RRRRRRRRRRRRRRRRR", "KPOW!", "VRRRM, VRRRM". When girls play the toys almost always talk to each other.
The reason is the male mind is object oriented (and human count as objects), while the female mind is relationship oriented (and to a small child car and trucks can have relationships, too).
If your little girl is playing with trucks, ask her what the trucks are talking about. If she launches into an imaginary conversation the toys are having, then you know she's being a little girl, even if she is playing with cars and trucks.
