Why a Liar's Body Language Might Look Honest and Fool You

Regardless of what people think, it is exceptionally difficult to tell if someone is lying. Even the very best human lie detectors are only right slightly more than half of the time (O’Sullivan & Ekman, 2004).

Why is it so difficult to tell if someone is lying?

Decades of research give us a clue. First and foremost, there are no foolproof body language cues that are consistently associated with lying. All too often, people look for that tell-tale sign that is a dead giveaway for deception taking place – the avoidance of eye contact, that touch on the face, the nervous gesture. Unfortunately, none of these are consistently associated with lying across different people and different situations. My wife is convinced that when my tone of voice rises, I’m definitely lying. She’s wrong (but please don’t tell her).

Here are some reasons why it’s difficult to detect lies:

• Noise. Part of the difficulty in detecting lies is due to “noise.” By noise, I mean that when someone is telling the truth or lying, there is a lot of nonverbal behavior going on. Much of it is unrelated to whether the person is lying or truth-telling. Nervousness—displayed as fidgeting, stuttering, rubbing hands together—is associated with lying, which makes sense, but if a person is nervous for a reason unrelated to deception, or if the person’s nonverbal style just naturally gives off stereotypical cues of nervousness, this can create a sort of “smokescreen,” making it difficult to accurately use nonverbal cues to detect deception.
• Honest Demeanor Bias. Some people may be particularly hard to detect when lying because they tend to emit cues that are stereotypically associated with truthfulness and honesty. That is, they speak more quickly, have pleasant facial expressions, and fluid gestures and body movements. Our research found that people who “naturally” displayed these sorts of cues were judged as more honest, regardless of whether they were telling the truth or lying.
• Social Perception Biases. Many biases tend to occur when we are judging the behavior of others. One such bias is the confirmation bias. That is, if we suspect someone to be lying, we search for body language, and verbal, cues that they are lying to confirm our initial suspicions, and vice versa. Another bias is the trusting bias. In experiments when judges are told that they will watch a series of videos of people lying and telling the truth. Even when they know that half are lies and half are truths, there is still a tendency to judge well more than 50 percent as truthful. Most people are more likely to believe than disbelieve (except when the experiment is run with police officers, they have the opposite bias,– judging many more as lies than truths (which makes sense because they deal daily with people who are lying).
• The Game of Lying. When people are lying, they take care to present more stereotypically “honest” body language cues. For example, in our studies, we’ve found that liars are more likely to engage in eye contact than when telling the truth (that is, they know about the stereotype that liars can’t look you in the eye, and they over-compensate). If you are working to detect lies by observing another’s body language, they are observing you to see if you believe them or are skeptical, and they may change their behavior to look more honest. This is a major reason why it’s difficult to consistently detect lies.
• Maybe Stick to Verbal Cues. As we have seen, there are many reasons why body language cues are unreliable for lie detection. It may make more sense, however, to pay close attention to what people are saying, rather than how they are saying it. One of the best predictors of lying in our research was how plausible the lie was. Simply, did the person’s “story” seem credible?