vocabulary of a child

The tv was on, and a commercial for Children's Claritin aired. I wasn't really paying attention to it, but RW (the oldest) heard it. He was standing at the fridge getting his lunch, and looked at me and said "I love that. Because 6 year olds would say 'drowsy'. " and he made a face of incredulity. He went on to say that every other 6 year old he's ever known says "sleepy", ending with a huffy "duuuh"