Is your body language costing you a promotion? Fidgeting, chewing nails and playing with hair or clothes can signal discomfort or anxiety. By Jenna Goudreau, Forbes.com "Half or more of all communication is nonverbal," says Todd Dewett, a management professor at Wright State University. Professionals are stressed. They are multitasking. They face many competing demands. Consequently, while they might sometimes be focused on using words correctly, they never give a second thought to what their body is saying. Evolutionary psychologists contend that nonverbal communication is largely driven by the limbic system, so body movement and facial expressions are usually unconscious reactions - evolutionary artifacts of behaviors that developed thousands of years ago. However, many of the mechanisms that once ensured survival - an unfamiliar face provoked a fight or flight response - are no longer productive today and may even derail your success. "Communication, including body language, becomes significantly more important when considering who's promotion material," says Dewett. As soon as you step into a supervisor role, it all comes down to communication skills. Forbes.com slideshow: See the 10 worst body language mistakes Do you know what your body's saying? Communication and management experts detail the silent signals you may be sending. You're not confident From their vocal intonation to the tilt of their heads, successful professionals should convey confidence and authority. However, common body language mistakes may make them look uncertain and indecisive. Poor posture can be detrimental. "When you slouch you do not have a dynamic presence," says career coach Sarah Hathorn. In the business world it sends a strong signal that you lack confidence and have poor self esteem, which can undermine your actual abilities. Similarly, your handshake is a strong indicator of who you are as a leader. Hathorn says it's important to strike the right balance, as a weak handshake (something women are often guilty of) shows a lack of authority and a bone-crunching handshake (more often in the realm of men) can come across as overly aggressive. "Most people do not how to do it properly," says Hathorn. You want be firm and match the strength of the person's hand you're shaking. You're disinterested People at work fall into day-to-day routines and show far too much of their internal life, says Dewett. Showing signs of disinterest and disengagement is particularly destructive. Dewett warns against common ticks like looking at the clock or your watch while speaking with someone, as they will assume you are arrogant or don't buy into what they're saying. Also, angling your body away from a person, not leaning into a conversation or looking past them signals that you want to distance yourself from them or their ideas. It's also very important to control your facial expressions. "Be aware of it," says Hathorn. Are you looking down, frowning or scowling with the forehead? She says even a blank face may come off as negative, and suggests holding a very slight smile so that you look like you have energy and are paying attention. Furthermore, avoid fidgeting in meetings - adjusting clothing, pulling the lint off your sweater or playing with your phone - which will come off as distracted and indifferent. You're disrespectful Invading others" space is a major no-no, because it signals that you don't respect them or their boundaries. Hathorn says every person has a radius of 1.5 feet that they consider intimate space. In business, you wouldn't want to come any closer than arm's length, she says, or you run the risk of making someone feel uncomfortable. The same respect should be given to others" office spaces and personal items. Picking up items on their book shelf, putting your feet on their desk or otherwise making yourself too at home will communicate disrespect for the person and their work. Facial expressions like eye rolling and frowning are clear signs of disagreement that need to be kept in check. More subtle movements may also portray negativity. If you squint or narrow your eyes because you're thinking, you might inadvertently appear as if you are questioning what your coworker is saying, says Karen Friedman, author of "Shut Up and Say Something: Business Communication Strategies to Overcome Challenges and Influence Listeners." Meanwhile, multitasking - even having a Smartphone out on the table - will be perceived as disrespectful because you're not offering your full attention. You're uncomfortable "People tend to use very closed body gestures," says Hathorn. Folding your arms over your chest or crossing your legs appears protective and as if you're not open to receiving the message. Open up your body language so others feel like they can approach you. Feelings of discomfort are especially evident when you're making a presentation - the one time everyone's looking at you. "Most people can't stand presenting," says Dewett. They'd rather die. Usually that's apparent. You either shut down emotionally, using a monotone voice, no facial expression and look at the floor, or have an excess of movement, seen in shuffling feet, playing with hair, scratching or rapid blinking. "Get yourself on video," he advises. It will open your eyes very fast. You're lying Your body should communicate your credibility, so the last thing you want to do is fake it. "There is nothing worse than a phony smile," says Friedman. If you are smiling because you are trying to be polite or ingratiate the boss, then that smile should truly light up your face to the crinkles at the corners of your eyes. Fake smiles typically involve just the mouth. Dewett adds that eye aversion and incongruity between words and gestures also suggest deception. "The funniest to me is when there's a mismatch: You'll say "sure I don't mind doing this" but your face is repulsed, or you'll say "yes" while nodding no," he explains. Dewett recommends becoming more aware of your body and asking for honest feedback from trusted coworkers to better align your words with your body language.