In human conversation, we sometimes offer explicit confirmation such as "yes", or "I agree", but more often implicit feedback via a slight nod of the head, or within the enxt utterance. Explicit confirmation is usually used where there is breakdown in the conversatn, say after a point of confusion, or where the issue is particualrly critical: "do you really want to send a million dollars to this account?"
Used on Chap. 19: page 477