I do not think it is because he is full, as 1/2 after lunch, he is constantly asking for snacks. And then shortly after snack, it is home time and the first thing that he says to his father at the door is "Dad, when I go home can I have a snack".

My only rule is that you need to try a bit of everything on your plate. But he tries to eat everything because he mom tells him to. On a side note, I do not give them much, I give them less then I do my 2 year old.