I do this to. In my case, I do it after I have heard or seen something surprising or puzzling. I do it while I am processing the information. It's a way to s

I do this to. In my case, I do it after I have heard or seen something surprising or puzzling. I do it while I am processing the information. It's a way to signal to the person or people I am with that I am offline i.e. not receiving further input through my eyed and ears whilst I am processing the data.