Harry Emerson Fosdick

It is only when you watch the dense mass of thousands of ants, crowded together around the Hill, blackening the ground, that you begin to see the whole beast, and now you observe it thinking, planning, calculating. It is an intelligence, a kind of live computer, with crawling bits for its wits.

Listening and hearing are two different things, and acting is comprehending what the person is saying, thinking how it makes you feel and responding. That's the key to really honest, truthful, compelling performance.