We've been working with Gavin on sharing. We tell him that taking things from people makes them sad. It appears the message is sinking in, based on this conversation between Jason and Gavin at the restaurant where we ate dinner tonight(Steak n Shake, nothing fancy). The server came by and picked up Jason's empty plate and took his glass back for a soda refill. Gavin saw this and was really concerned. He said
G: Oh no! plate!
J: Yep, she took my plate and cup.
G: Sad.
J: I'm not sad. The plate was empty so she took it to the kitchen... but she'll bring back my cup
G: Happy!
J: Yeah, then I'll be happy.
Which appeared to satisfy Gavin for a few minutes. He reiterated the story to us a few times throughout the evening, as if unable to comprehend still why the server had taken the plate.