One thing that I've noticed about little children (age two to five) is that they don't know how to share -- that's the obvious part. The other part is that they are

learning to hoard before learning to share

Up to this point, kids are not greedy (they don't know anything about greed). They'll simply be interested by anything. But at this point, they change a bit. They start having "my {whatever}!"

I don't know how to explain that, but you notice when it happens. Even if they're not interested in something, they'll hold onto it for dear life and bawl if it is removed. It's just a strange thing -- going from complacency to greed, before being able to learn to share and give.

Or maybe, I'm just imagining this developmental stage. Heh.