Not to be contentious, but there is something to be said about the negatives of nonverbal communication. For one thing, one can “lie” with nonverbal communication – it is done at every hand-shaking occasion, for example, plus experts can both disguise and send false signals with their “body language.” Secondly, nonverbal communication is vague and inaccurate, nowhere near as accurate or finely nuanced as verbal communication – there is no “thesaurus” for body language. Nor can nonverbal language replace a legal document. Thirdly, body language has little or no “syntax” or even taxonomy. Fourthly, nonverbal language is difficult to store or record or prescribe. Finally, “body language” is only one kind of “nonverbal communication”; what about visual rhetoric, or Jungian symbolism, or color theory, or interpersonal communication based on shared experiences (personalized metonymy), etc.?
This is a great question. Nonverbal communication is important when we realize that people communicate with each other in many different ways. In other words, the sum of our words is not the sum of communication. In many ways, the nonverbal signs are much more powerful. Let me give you a few examples.
First, people realize that words can be exaggerated, broken, and insincere. This is especially so in a business transaction, where people just want to make the deal. So, at times people view words with suspicion and pay close attention to nonverbal things.
Second, in light of the above point, people are able to read the sincerity, integrity and other important characteristics from body language. Is a person comfortable in speaking? Does a person look at you straight in the eyes. Does a person have a firm and confident handshake. Does the person's body posture suggest affability. All of these question immediately are observed. And these communicate something about the person that you are interacting with.
Third, truth be told, sometimes it is the non-verbal communication that forges relationships and gets the job done.