Body language is an unaware process of movements triggered by the mind. The body does not lie and is, contrary to consciously adjusted behavior. Reading body language is a natural gift for most of us. In our childhood we rely and respond to body language like facial expressions, sounds, tenderness, warmth, etc. However growing up we increasingly focus on words. Why does it make us feel uncomfortable when we hear a person talk while looking at him?
Being a well gifted speaker does not mean we can hide the (subliminal) emotion (read: movement) behind the words. The body expresses our thoughts even if we say the opposite. Our eyes are capable to perceive (contradictory) movements within a split second analyzed by the brain immediately.
Opposing tension of the hands showing negative emotional display without correlation with the face or other members will give confusion. If true and correlated, they tend to strongly mirror each other. The reverse is also true. If the face is relaxed – the hands tend to be tranquil as well. This nonverbal tell is particularly valuable during negotiations, sales and in similar contexts.