The topic of "sharing" comes up pretty often, in conversations with other parents in real life or online, because every young child eventually has a moment when she yanks a toy away from another child or gets her own toy yanked away.  What often puzzles me about discussions of sharing and taking turns is that so many parents talk as if these are concepts that apply only to interactions between children. It seems to me that as a parent, you share things with your child and take turns using things with your child, so everyday life is full of opportunities to model and teach sharing.

I often hear claims that kids under 3 or 4 just don't comprehend sharing, so there is no point trying to teach it. Yet I started to teach (consciously) about sharing and turn-taking when Nicholas was just six months old.  When he started eating solid foods, we had a lot of interactions like this: "Oh, you want to share my applesauce? Okay, a bite for you...a bite for me...your turn...my turn...your turn...my—hey, don't grab; this is my bite. NOW it is your turn...."

Around 10 months he enjoyed a game in which he would clutch an object and look very pleased; I would say, "You are holding the book!"; he would give it to me; I would say, "I am holding the book!"; he would hold out his hands; I would give it to him and say, "You are holding the book!", etc. This soon turned into, "Please give me that book." "Iss fo oo!" "Thank you!" "Yelgum... Peeez?" "This is for you!" "Enk oo!" "You're welcome!... Can I have the book, please?" and so on. He seemed entranced by the idea of learning how to get things and when to give things. We played this game frequently until about 15 months, by which time he was using the appropriate gestures and syllables in real-life contexts as well and was often responding favorably when we asked him to give us things.

He's not quite so cooperative at two-and-a-half, when he's got a short fuse and a strong sense of what he wants...but he still is relatively good at sharing compared to many kids his age, and I think the foundations are set for a lifelong good attitude about it; he's just going through a tough stage right now. He is so STARTLED when a kid snatches away his toy without asking and won't give it back—not angry so much as blinking in surprise as if a law of physics has been violated!  After a moment, he says in a very firm voice, "Don't take mine train! That's not nice! Is not your turn!" and tries to get it back, sometimes grabbily, but all his motions are focused on getting the toy, not just bashing the kid. When he's angling for another kid's toy, he'll say, "I need turn with train, please?" or if he's very eager, "My turn for train!" and he grabs it, but if the other kid flips out he hands it back, albeit reluctantly and with another plea for it within one minute!

So I disagree that toddlers don't understand sharing and can't do it. It just looks a little different. And I hypothesize (based on my experiments with one participant!) that the earlier parents start talking about it and demonstrating appropriate behavior in their own interactions with a child, the earlier he/she will start applying the same rules to interacting with other kids.