First, face-to-face conversation is a dynamic interaction between two people. Talking is a kind of turn-taking, and turn-taking is a rhythm that organizes how and when things unfold. When people talk, they modify their postures and tempos so that they correspond. (There is fascinating research on this sort of "coordination dynamics" by, among others, J.A. Scott Kelso and colleagues.) And moreover, they tend jointly to pay attention to what is going on around them. One upshot of this is that when you are talking with someone, you actually experience that they are listening. Talking, in this sense, is like dancing. You can tell whether someone is dancing with you or whether they have detached and lost interest.