Well data needs to be conveyed, as in there has to actually be a message. If one person yawns and that causes you to yawn, that is not evidence of communication

Well data needs to be conveyed, as in there has to actually be a message. If one person yawns and that causes you to yawn, that is not evidence of communication - the first person was almost certainly not trying to send any information and you received none. Mimicking another's arm movement could be just as meaningless.