the times i've asked him about it, he said he was reminded of something from his own past. that is a lot of what they are doing as they are "just sitting" there - they are noting what feelings and associations our words and body language are bringing forth in themselves - that is how they get to the unconscious motivations and reactions behind our behavior - it's really not just what we are literally saying to them. We might not SAY we're afraid, for example, but they pick up on the sense of fear.