Do you ever talk to someone and there's no response? (... yes, I'm referring to my kids here ...) So what do you do? You repeat yourself (several times) until eventually you hear a mumbling sound like: 'yeah yeah'. Well, at least you got some response, right?

In the above case, I KNOW that my children hear and understand me perfectly well. But what about your child learning a language? When you want to practise German with her and she gives you that blank look: I haven't got a clue what you just said.'