This is an after-the-fact thing, but I try to relate what they've done (how they've hurt someone's feelings) to a situation they've been in recently in which they were counting on someone's favorable reaction. "How would you like it if Daddy said the picture you drew wasn't very pretty? What if he didn't even want to look at it? How would you feel then? Well, that's how you made X feel when you did X." It's not original, but it's the technique I fall back on, hoping some of what I'm saying will stick & they'll think before opening their mouths the next time.
Luckily, I've found people who have young children of their own usually don't blink an eye when other kids do this. We've all been in this situation, and can really empathize with other parents!
What I did with my daughter (and what my mother did with me) was practice other possible comments—or simply saying "thank you" and nothing else—when receiving a repeat gift. If the giver discovers it's a repeat gift, you might practice having the child say something like:
But my old one is worn out or
Now a friend can have one to play with too! or
Maybe I can leave this one at my babysitters!
I found that the best approach is just saying "thank you"—which takes practice, but in time, will work.
Teach your child to be gracious for everything! Teach them to say, "Thank you!" Maybe we could teach the adults not to be offended by a child's response, or such an innocent remark.
Teach them to say, "How did you know I liked this so much!" Or, regarding the "not the one I asked for ... " how about, "Thank you for the _____. It's like the one I asked for."
Bettye M. Caldwell, Ph.D.
Get together with your children ahead of the gift exchange time and do a little role-playing. Say something like, "I'm Grandmother, and I've given you a Barbie just like one you already own. What might you say?" Work toward things that aren't outright lies but that would not hurt grandmother's feelings. Work toward something like, "Oh, Grandma, you remembered how much I like Barbie dolls." After you get a response that doesn't sound too selfish and unfeeling, have the child rehearse it several times. And hope for the best."
Our parenting advice is given as suggestions only. We recommend you also consult your healthcare provider, and urge you to contact them immediately if your question is urgent or about a medical condition.