When your child with ASD is doing his/her stimmy thing (and I mean in particular playing with the same toy, reading the same book, watching the same video, singing the same song, etc.), do you just let him/her be, or do you try to 'intrude' on it by joining in, or do you positively try to make him/her stop by saying 'five minutes of this, then something else'? I ask because different approaches to ASD will suggest different strategies.