That's his best trick: making the audience think it's all about his mastery of human psychology. I don't doubt that he has a good sense human body language, or even that he may use certain cues in his act, but at the end of the day all he is is a magician with a gimmick. I'll give him this though: it was a stroke of genius to come up with the idea in the first place.
Magicians are only successful if they capture the public imagination. In the 18 and 1900's it was easy because people were gullible. Then the paranormalists had there time in the spotlight, while of late illusionists have sold themselves on performing what seems like the logically impossible. Each generation of magician has known that what made their audiences tick was appealing to just beyond what the average person could explain.
Brown deserves a lot of credit for his act. He knows that audiences are jaded with the old school of magic so he's come up with the genius idea to appeal to the current public fascination with/misunderstanding of science and psychology. He may be entertaining, but that doesn't change the fact it's just a magic act.