The Toddler's Creed, composed by T. Berry Brazelton:
* If I want it, it's mine.
* If I give it to you and change my mind later, it's mine.
* If I can take it away from you, it's mine.
* If I had it a little while ago, it's mine.
* If it's mine, it will never belong to anybody else, no matter what.
* If we are building something together, all the pieces are mine.
* If it looks just like mine, it is mine.
Three-year-olds are inconsistent about sharing at best. Sometimes they manage; more often they don't. It's largely a matter of development of certain parts of the brain. Telling them they're selfish is not a good idea, because they tend to believe those assessments and 'live down' to that expectation.
Just keep coaching him on sharing. Empathize with his frustration and you may be able to head off many tantrums. Here's how Dr. Harvey Karp, author of Happiest Toddler on the Block, speaks to younglings when they are starting to melt down over things they want. I've found this approach to be surprisingly effective:
http://www.youtube.com/watch?v=fJ1428uYs2g&NR=1&a.... .
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