Recently you had a parent open question meeting in Corpus Christi, TX. I was there with my 8 month old baby. You were talking to a woman who's 5ish son with Down syndrome was repeatedly hitting his chin and you mentioned he was satisfying a feeling that was in his jaw by that action. I have noticed my baby has started doing that with her left hand. What do you recommend to help correct/redirect this behavior now?
The sight of stability and calming for an infant is in the temporomandibular joint. This joint is where the upper and lower jaw meet right below the ear. There are more nerve endings going through that joint than any other location in the human body. When a baby sucks his/her thumb, sucks from a bottle, sucks on a pacifier, etc. the nerves in that joint are stimulated and the baby calms or even falls a sleep. If your child is doing other behaviors to stimulate the jaw like hitting the chin or for older children it may be teeth grinding, then it is probably time to introduce the Bite-Tube Hierarchy. You can learn more about this and other activities to increase jaw skills for both feeding and speech clarity in my book, "Assessment and Treatment of the Jaw: Putting it all together, Sensory Feeding and Speech."
If you do decide to purchase that book please read the chapter on Sensory first as it will explain to you in more detail the reason why babies and children with muscle-based deficits develop "habits" to compensate for the jaw weaknesses. I would also encourage you to share this information with your SLP as she may have additional suggestions.
I hope this has answered your question.