I know this post is old but in general would like to add my viewpoint. I'm glad I found this, I've wondered why my aunt in law does this since I've met her, and today my mother. I've just noticed my mother doing it, and it's been after a strain in our relationship after my sister passed. I think it would make sense she is trying to build a stronger connection, it's telling that a lot of older females and mothers do it. My mother is hard of hearing, and i do talk fast and mumble sometimes. It is distracting and made me feel a little self conscious and confused, that they needed to repeat the movements of my mouth. The words are silent, it really is just mimicking at the same, like they are trying to figure out what words I am saying, I've noticed the aunt usually nods a little to herself when she understands. It must have something to do with them really caring and trying to be good listeners. Oh for the first time my mom has started kissing me on the mouth goodbyes, instead of cheek. I figure she must really need that mother daughter connection and wonder if the mimicking has a connection to some form of nurturing instinct.