I observed an almost surreal form of nonverbal communication when I was a business student. At the front of the classroom, an entrepreneur was practicing a pitch he would make later to venture capital firms. Specifically, he was talking about a technology his firm had developed: a new type of respirator which could save many new-born children.

When he talked about the potentially great financial returns, the audience, made up of M.B.A. students, sat back passively. But when he talked about getting babies through critical moments with his respirators, every single person in the classroom sat up, alert and fully focused.

As he went back and forth between stories of saving babies and talking about financial results, almost every student in the classroom moved with him. And what's more, it was almost as if the students' movements had been choreographed to the content of the presentation.

They sat up together when the entrepreneur talked about saving babies, and they sat back in unison when he discussed the numbers. And, by the way, I did it too until I become aware of how we were responding as a group.

I've believed firmly in body language since then, body language being a form of nonverbal communication in which people consciously, but more often unconsciously, show what moods or emotions through body movements.

As you likely know, interpreting body language is part science and part art. Still, some basic gestures will give us insight into the emotions or moods of others. A few examples of this form of nonverbal communication follow.

As most salespeople know, when the person across the table crosses their arms, it's an indication of defensiveness, or a lack of receptiveness. On the other hand, if that person leans forward and keeps his or her eyes on you, then you do have a receptive listener.

Novice speakers, for instance, often show a lack of confidence by keeping their arms in tight to their bodies. Their arms will move away from their bodies as they get more public speaking practice, and they'll begin to consciously use their arms to send or reinforce their messages.

Arms wide open indicates trust and openness, as do open hands, while arms held high above the head show a sense of victory, and hands clenched indicate anger.

Curiously, one of the most difficult interpretations of body language involves lying. Researchers have probably spent more time on this aspect of body language than any other. And we're still not entirely sure what body language to trust when it comes to truth and trust.

If you haven't yet spent much time studying body language, I recommend that you add it to your to-do list for communication development. It's invaluable not only for speaking and listening, but also for negotiating and leading.

Summing up, body language, a form of nonverbal communication, gives us insight into emotions or moods, and helps us send and receive messages more effectively.