Teaching a young child to share, as in 'requiring' or 'guilt-tripping' him or her to share, usually interferes with their willingness to share. Here are three things to think about:
1 - Young children are keen observers of adult behavior, and in the adult world, they likely, by even age 3, have perceived that adults are not as willing to share their own personally valuable and meaningful items with strangers or even acquaintances as they are in being sure they (their own children) do.
2 - They are in the middle or at the end of learning what "mine" means - from how their parents and siblings (if any) use the word. Again, in the adult world, "mine" means "I get to say (control) what happens to it, including who gets to use it."
3 - Finally, and critical to your understanding: force causes resistance. Our attempts to "get our child to" do anything always results in resistance (at some level, in some way). [aka The Parents' Dilemma in Beyond Good Parenting]
Imagine for a minute that your parent was visiting, and a neighbor came by and asked to use your car, and you feel very uncertain about it at best, and maybe your first thought is'no way!' Then your parent steps in and says to you, "Let your neighbor use it! Come on, give him the keys. Be nice!" And imagine your parent has the power to make you give the keys to your neighbor, either through force or by withholding something from you that you depend upon (maybe that's why, by adulthood, we try to have as few dependencies on our parent as possible!).
What is the alternative? Give and support your child having control over his or her own belongings. This also means giving up trying to get your child to be nice. (It is okay to be nice, but being nice only works under certain circumstances. As or if you read more posts, you'll see that being respectful and honest trumps being nice.
Then, role model appropriate sharing at every opportunity. For me, this meant bringing my own toys, balls, etc., to the playground or to my classroom. I did this for two reasons: it gave me something to play with (!) and gave me an opportunity to role model sharing with others. My own child or students could see the impact of sharing, as well as see how sometimes I wouldn't share, such as when the child who wanted to use what I brought seemed likely to break it (whether just to see what happens or by accident)
Summary: Giving your child complete control over their own belongings facilitates their willingness to share, and also facilitates them learning to be responsible for their own things.
Enjoy! Marty Comments? Please share!