Why are we so quick to limit oursel

Why are we so quick to limit ourselves? I’m not denying that most little girls love dolls and most little boys love videogames, and it may be true that some people favor the right side of their brain, and others that left. But how relevant is that to me , or to anyone , as an individual? Instead of translating our differences into hard and fast conclusions about the human brain, why can’t we focus instead on how incredibly flexible we are? Instead of using what we know as a reason why women can’t learn physics , may be we should consider the possibility that our brains are more powerful than we imagine.