Non-verbal Messages Allow People To:
Reinforce or modify what is said in words. For example, people may nod their heads vigorously when saying "Yes" to emphasise that they agree with the other person, but a shrug of the shoulders and a sad expression when saying "I'm fine thanks,” may imply that things are not really fine at all!
Convey information about their emotional state.
Define or reinforce the relationship between people.
Provide feedback to the other person.
Regulate the flow of communication, for example by signalling to others that they have finished speaking or wish to say something.