and more on the candy theme
Just to clarify, and in response to a few emails and comments:
I started out moving the candy from their bags into a little pile for me, but they decided that I was really just interested in acquiring their candy for personal gain, so I rerouted it into the bag of the sibling.
Prior to the candy incentive, Juliana would 'help' by reminding him, which really didn't help, as it was just another external monitor. Under the new deal, she has a selfish reason to not help him, which, in the long run, actually helps him. He has so radically upped his ability to self-monitor, that he actually loses very few pieces to his sis. She has lost about the same number to him (fingers-in-plate is her pet foible), so it evens out.
I do appreciate your cautions about setting them against each other and I move very carefully in this regard.