I have a pupil in my class with autism. There are times when he is laughing so much that he is hysterical. But within seconds he can be inconsolably upset. However i have also seen this behaviour at more inapproprite times. for example someone falls and hurts themselves and the person with ASD laughs. This may be part of their diminished social understanding. They may be trying to interact with the world and know that a fall requires a reaction. They just haven't got the right one. Do you see what I mean