A former FBI agent reveals 7 ways your body betrays you when you're nervous

The problem with trying to conceal your anxiety during a job interview or an important presentation is that we've evolved to do exactly the opposite.

Back in our caveman days, when you saw a wild animal, you wouldn't have to stop and shout, "Lion!" Everyone in your tribe would know from your bug eyes and frozen posture that you'd just witnessed something scary and they should take action.

In other words, we're basically hardwired to display anxiety - and to recognize it in others.

That's according to Joe Navarro, a former FBI agent and the author of "What Every BODY is saying."

Navarro says there are certain universal, nonverbal expressions of nervousness that are pretty hard to control. Here are some of the most common:

1. You blink more frequently.

Researchers have found that eye blink rate increases when you're under stress, like when you're nervous or when you're lying about something.

It's an automatic physiological response, so you might not even realize when it's happening.

2. You compress your lips.

Navarro says people testifying before Congress often display compressed lips, which is generally an indicator of psychological distress. Sometimes it's an indicator that someone is lying - other times it just means they're under pressure.

For example, David Givens, an expert in nonverbal communication, writes that President Clinton's lips "visibly pressed together, tightened, and rolled into a thin line each time he talked with reporters about the Lewinsky affair."

According to Givens, we instinctively tighten our lips to protect ourselves from danger - real or imagined.

3. You play with your hair.

Hair-twirling is an example of a repetitive behavior that Navarro describes as "pacifying." Essentially, doing the same thing over and over again is a way to alleviate some of the anxiety you're feeling.

Under extreme stress, Navarro says this behavior can become pathological, and people can end up pulling out their own hair.

4. You yawn excessively.

This one might seem counterintuitive - who could be tired when they're freaking out?

But Navarro says that stretching the jaw is really a way to stimulate the TMJ nerve and reduce feelings of stress. In fact, nervous animals exhibit the same behavior.

Other research has found that yawning helps regulate our body temperature, bringing cool air into the nose and mouth. (Stress and anxiety cause the brain to get hotter.)

5. You touch your face.

When you video tape someone who's nervous and speed up the recording, Navarro says "it's hilarious how often we touch ourselves under stress."

For example, when some people are nervous, Navarro says they squeeze their face, push on their cheek, or rub their forehead. Again, it's a means of pacifying. "They put pressure on their nerves to help soothe their brain."

6. You contort your hands.

This behavior can take a number of forms. Some people interlace their fingers and squeeze them together; some people interlace them and rotate their hands back and forth in an awkward way; some people crack their knuckles.

These repetitive habits are ways of soothing our nerves, although we can be completely unaware that we're doing them.

7. You rub the skin on your hands back and forth.

Some people under tremendous stress end up rubbing their hands until they bleed, Navarro says. While it starts out as a way to relieve anxiety, it ends up causing more problems in the long run.

"The downside of stress is that you can find pathological ways of dealing with it, but they will hurt you," he says.

One way to control these behaviors is simply to slow them down. You'll probably get the same soothing benefit - but your anxiety won't be so visible, and you won't have to worry about hurting yourself (as in the case of hair-pulling and hand-rubbing).

Another strategy is to do some simple physical exercises before you head to the conference room for your presentation or interview. Stretching from side to side or doing a push-up against the wall should work to relieve some of the stress, Navarro says.

Of course, perhaps the best way to manage anxiety is simply to come to terms with it. Acknowledge within yourself that you're nervous because something important is happening, and tell your listeners how you're feeling. You'll likely be surprised by the relief you feel.