Here's a situation, you are talking with co-workers on a lunch break. One of them said he is planning to apply for a promotion because he thinks he deserve it. You did a half-smile, pulled your eyeglasses down to your nose bridge and peered over him, as a reaction. He then looked at you angrily and walked away. Pretending to be confused, you're like, "what did I do?" He was obviously insulted. Your gesture delivered the notion of him being unworthy to get a promotion. You said nothing, but he got your message anyway.
Action speaks louder than words. So true when we literally talk of body language. The human body speaks volumes. By just observing a person's posture, eye and finger movements, verbal contexts and tone, breathing, skin color, etc.; you can gain access to ones thoughts and feelings. In this discussion, we will focus more on body movements and postures.
In an event where u are the speaker of a conference, you know that you have the person's full attention when he keeps his palms down with the left hand over the right and his head tilted sideways which is a sign of interest. However, if you see the right hand covering the left and there is a quick flick of his head upwards, it means otherwise. This person is sending u a signal that he has doubts, probably not agreeing with what is being said, and is just waiting for his chance to interrupt. He may also pull his earlobe at the time when he is about to butt in.
Meanwhile, if you observe someone looking straight at you, not blinking, body tense but upright, don't be fooled. His gesture shows inattentiveness and that person is just giving you a false impression that he is listening. Some other unwilling listeners show postures like, sitting with both arms and legs crossed displaying mental withdrawal and opposition to what is being discussed. When you see one with head resting on his hand and eyes looking down, or head raised to look at the ceiling with fingers slightly tapping the armchair, or maybe legs crossed with foot slightly kicking, these are all signs of extreme boredom. Well, aside from yawning, of course.
To stir up discussions, try to ask questions or make your listeners ask something to get their full attention and for them to be alert. Observe when you try to ask questions that involve weighing of answers: A person tells you that he is not sure of what to say when he rubs around the surface of his ear (usually followed with "well, I don't know"). Rubbing the eye or touching the nose gently with the index finger, indicates doubt or inability to answer the question. Stroking of the chin may indicate thinking but if his index finger stretches a bit to touch his puckered lips, it signifies uncertainty of his answer.
In situations where you are the one answering questions, a person nods his head when he implies that he agree with you or realizes what you mean and is encouraging you to go on. But if he is rapidly nodding his head, it may mean that he wants you to stop talking and that he can't handle listening to you anymore. The same with a person rubbing his hands together, a sign of anticipation- not for more lectures but for you to finish and call it a day.
Nonverbal communication, in its deeper sense, gives out signs that are clear enough for you to realize. People unknowingly make others see more of them by how their body speaks. Amazing how physical movements convey a clear idea of what's in ones mind huh? There's no need of words; just that simple drumming of your boss' fingers on the table tells you what you need to know.
More about Body Language here ...