You have to watch this video of Marc Salem. It is simply amazing what this guy can do in terms of reading peoples’ behavior. I am certain that he would make a phenomenal poker player, always knowing what other players are holding.
There is a philosophical view called behaviorism. According to an unsophisticated version of the view, mental terms, such as “thinking that I went to Bermuda for vacation” or “feeling a pain in my toe” can be analyzed in behavioral terms. The view is not taken seriously anymore. One of the objections to it is that people can think things or feel things without exhibiting any behavior. After seeing Marc Salem perform, I am not so sure that this objection has any merit.