Why do they exist in the first place? Communication? Maybe. A need to move. Also maybe. Do you know the medical history of that particular child? Do you know if they have seizures? Do you know a running list of all of the medications that they are currently taking? Do you know the lists of all of the main side effects and then the low frequency side effects of EACH of the medications that they are taking? Read them. Use a map of the entire body and write out the list of side effects of the medications. But first. Write down the lists of sensory repetitive behaviours and locate them for each body part.