You’ve probably heard the term “nonverbal communication” many times. And perhaps you’ve wondered what it refers to in terms of presentation skills.

Nonverbal communication means everything you communicate to your audience apart from the words you say. Your content (words) is a critical part of your message, of course. But studies have shown that what you look and sound like as you’re delivering information plays a central role in the message that’s received by your listeners.

In research conducted at U.C.L.A. and published in 1981, communications expert Albert Mehrabian found that 93 percent of message reception comes from nonverbal communication over verbal content. Mehrabian was specifically focused on messages with a high emotional content. But the kernel of his findings remains: A huge proportion of your effectiveness as a presenter depends upon your appearance, movement, and vocal presentation.

A classic example of this dynamic in action is the opening debate in the Kennedy-Nixon presidential contest of 1960 — the first televised presidential debate in history. Nixon at that point in the campaign was ahead in the polls. But how he appeared on television in that critically important first debate hurt his candidacy considerably.

Viewers had no idea that the Vice President actually had the flu that day. What they saw was a man with a hastily applied make-up job who was sweating profusely in the harsh studio lights, and generally looking ill at ease in the new medium of television.

Across from Nixon was the tanned, athletic-looking Jack Kennedy, who not only gave the impression of youthful vigor, but intuitively seemed to understand how to use the cameras to advantage.

Interestingly, post-debate polls showed that among voters who listened to the debate on radio, Nixon was judged the winner. But the nonverbal message that millions of television viewers received was that Nixon was not up to the sheer physical demands of the American presidency.

You’re probably not running for office — but what your body and vocal instrument are telling audiences is no less critical to your success. Unfortunately, there’s no magic pill I can give you to make you a more effective nonverbal communicator. But I can offer what I think is a valuable suggestion:

Spend less time on the content of your presentation, and more time on how you hold yourself, move, and sound as you speak. Some excellent tools to help you in this pursuit are a) a mirror, b) friends and colleagues, and most important, c) a camcorder. Together or separately, they’ll help you have an “out-of-body-experience” that you will learn from!

With their help, that is, you’ll begin to see and hear yourself as others do. That’s a crucial step in knowing how to marshal nonverbal communication to your success and profit.

(This article originally appeared in Dr. Gary Genard’s book How to Give a Speech, which is available at http://www.publicspeakinginternational.com/how-to-give-a-speech.html.)