Yes this is what I experienced with the dcg I mentioned before. It got to the point where if she wanted a toy or anything, she HAD to ask and until she did she did not get what she wanted. It's weird, I know...a part of me thought that sometimes this was her way of controlling her environment...sort of a manipulative behavior. Hard to explain but after seeing how manipulative she was with her parents by not answering etc. I realized this was a controlling behavior which is why I began demanding that she ask for things properly etc. I don't think you should rule out medical/ behavioral issues but I wouldn't jump the gun and say anything just yet to the parents and if you don't see any improvement in a few weeks try being a bit more demanding in terms of getting her to articulate herself. Clearly as you have mentioned her vocabulary is fine so that is not the problem...the question is WHY is she choosing not to answer...does she just need more time, is she being manipulative or could she be somewhere on the spectrum? All you can do is watch and wait.

