Answer: Because so often what is really being said is not coming from the sound of the voice but rather from the movement of the body. It is a basic form of communication yet a major message used to either confirm or contradict what someone is saying. 90% of communication is non verbal. Only 10% is verbal, 30% includes tone of voice, speed and volume and the remaining 60% is body language. It is the most truthful and reliable source of information.
Point: Learn and observe body language to determine what is really being said.