For example we know that when someone's flight response kicks bloods down into a person's legs in order to assist them in case they have to make a quick get away. Quite often what this does has cause the person's hand to cool because it no longer has the same about of blood warming them. Joe Navarro is an expert in reading nonverbal communication he did this for years for the FBI and has documented some examples of when this ability has assisted him in closing cases and solving crimes in his very good book, What Everybody is Saying. I would recommend that everyone interested in tracking patterns of communication to pick up a copy of his book.