I've never baby-talked to our son, but I do coach him to say things that are within (or almost) within his speaking capabilities. So for instance, this evening

I've never baby-talked to our son, but I do coach him to say things that are within (or almost) within his speaking capabilities. So for instance, this evening we were reading The Gruffalo, and he pointed to the fox and said, "Fox eat!" I said, "The fox wants to eat the mouse?" He said, "Yeah!" So I tried to coach him to say "Fox eat mouse". He got as far as "Fox eat there"; maybe he'll get to "Fox eat mouse" in a week or two.