E.C.
when my daughter was training she was into money so we had a piggy bank and she got a coin everytime she went and 2 for poop. Maybe where your son is alittle older he would like to get money and fill a jar to buy something of his own. Also we had a timer and she had to stop playing and go in and try everytime it rang. I think alot of times kids just dont want to stop playing and go in and go. Good luck!