As more politicians get ready to hit the stage during the presidential nominating conventions, they should be cautious about what they say -- and what they don't. Body language can speak volumes.
Whether it's blinking too frequently (a sign of discomfort) or gesturing frenetically (a sign of dishonesty), body language analysts say that perfecting the text of a speech is only one of many hurdles good speakers must master before approaching the microphone.
One man who has become somewhat of a public speaking guru, according to Greg Hartley, a former Army interrogator and author of "I Can Read You Like a Book," is former President Clinton, who spoke Wednesday evening at the Democratic National Convention.
"Bill is a pro," Hartley said. "He uses his face and hands to draw people in to what he's saying."
Hartley, who watched the former president and the Democratic vice presidential nominee Joe Biden speak, said that Biden's authenticity was shown through something as seemingly insignificant as his lips.
"Biden was licking his lips a tremendous amount -- it shows genuine emotion," Hartley said. "It's the human side of him and the animal side of him.
"When you see someone purse their lips, that's a typical male response to choke back emotion," he said. "It was good and genuine."
For those who plan to watch speaker after speaker take the podium, Hartley and other public speaking analysts said there are several cues one can look for when trying to determine the truthfulness of politicians.
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As a general rule, Hartley encourages people who are unsure of a speaker to pay attention to the way his or her body moves, perhaps even more so than the words coming out of the speaker's mouth.
"Illustrators, or body movements, are indicators of what your brain is thinking," Hartley said. "It's your body punctuating your thoughts. A person should have synchronicity between the two."
There are few politicians, Hartley said, who are capable of keeping their pointer finger under wraps during a speaking engagement, despite the negative effect on an audience.
"Pointing makes people feel like you're accusing them of something," Hartley said. "It shows the person is trying to make you believe something."
Last night, Clinton managed to reel in his desire to point at the audience, Hartley said.
"He whipped people [in the air with his finger] at times, but then he remembered to change off and use the closed hand instead of the finger," he said.
Kevin Hogan, the author of "Psychology of Persuasion," said that people who point while they speak are often questioned by listeners.
"People who point when they're speaking -- I always put a big question mark after whatever they have just said," he said.
"Pointing has always been a cloak of true feelings -- sometimes it's lying or trying to look intense when you're really not," Hogan said. "It's never accepted well."
Patti Wood, a public speaking expert who has analyzed speakers for more than 25 years, warns viewers that political conventions are notorious for being some of the hardest-speaking engagements to analyze because of the charismatic nature of those who headline the events.
"When someone has a lot of charisma, friendliness, attractiveness and power, we tend to disregard any lying or deception," she said. "We don't even see it."
But "intoxicating" as a speaker can be, Wood said, that person can also make mistakes that will poke holes in the legitimacy of the speech.
"One of the deception factors to look for in these kinds of conventions include where the speaker is looking when he is speaking," said Wood, who is not attached to the presumed Republican presidential nominee John McCain or the Democratic nominee Barack Obama.
"Notice whether someone looks straight forward when they say the most important statement," she said, adding that she has noticed that Obama often looks off to the side during his speeches.
Blinking, said Wood, especially when a speaker begins to do so at a faster pace, is often a sign of waning confidence.
"Frequent blinking would indicate that they don't feel comfortable with their statement," Wood said. "The timing is the tell: If a person's blink rate goes up drastically during one part of their speech, that would send a certain message."
It may seem minute, but even the way speakers interact with the podium can say a lot.
"Look for where their hands go on the podium as they are saying certain messages," Wood said. "If they grip the podium tightly when they say certain things, they may be indicating that they don't feel good about what they're saying. If you feel good and honest, your hands usually come up and open."
Wood criticizes McCain's tight grip of the podium, which, she estimated, he does "to keep his anger down but still appear energetic."
Body language expert Hogan said that the speed at which someone talks can also indicate how truthful the speaker is.
"When McCain is most genuine is when he speaks slowly and thoughtfully," said Hogan, who said he's a libertarian and does not support either candidate.
"When he gets rattled, his voice raises up in pitch and he'll sort of speak in spurts," Hogan said.
Pitch in voice is an issue onetime Democratic presidential hopeful Hillary Clinton battled with quite a bit, according to Wood.
"If a person's voice goes high on certain words, listeners become skeptical," she said. "Hillary's biggest tell was her voice, but really, almost everyone when they're under stress sees their voice go up [in pitch]."
Democratic vice presidential nominee Joe Biden lowered his voice several times during his speech Wednesday night, a technique Hartley said is a sign of a great speaker.
"It's a great technique; the quieter you get, the more important the information is," Hartley said.
"We tell secrets in very low tones so it's a good communication tool," he said. "People listen more intently when people speak softly."
And as Americans get ready to watch Obama speak and officially accept the Democratic Party's presidential nomination tonight in Denver, Hartley has some advice for viewers: No matter how captivating the speech, pay attention to the way he moves.
"When in doubt, trust his body language."