The Simplest Way to Spot a Liar

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The ability to separate a liar from a truth-teller is one that most people feel they need, but few people actually have. You’re talking to someone you just met, who claims to know your best friend from years ago, but this doesn’t quite ring true for you. Is it possible that this person wants something out of you, such as personal information that could be used against you or your family in some way? You’re reluctant to divulge anything, but on the other hand, what if this person really does know your long-lost pal?

In general, people are just not that good at detecting deception. As Tilburg University’s Mariëlle Stel and Leiden University’s Eric van Dijk (2018) note, “People have inaccurate beliefs about cues to deception” (p. 2). The average person relies, they observe, on such signs of a liar as nervous behaviors, but liars actually show fewer nonverbal cues that would signify they don’t mean what they say. It’s also possible, the Dutch researchers suggest, that people may not be wrong in their assumptions about liars, but that instead, the behavioral cues suggesting someone is lying are just not that strong. Stel and van Dijk tested the hypothesis that facial expressions signifying emotions might provide a more reliable set of cues than the liar’s behaviors.

The literature on detecting deceptive emotions, as Stel and van Dijk point out, is complicated by the fact that judging true versus posed smiles is not the same as determining whether a person who’s smiling is lying or not. When a salesperson waits on you and offers to help with a broad smile, you probably don’t consider whether this smile is genuine. You expect to be treated in a friendly way, and even if the person is acting, it doesn’t really matter to you. However, if you’re being smiled to by the person asking about your childhood friend, you’ll try to use the information from the smile to help figure out whether to divulge or demur.

Negative emotional expressions present a different challenge, because liars are actually not that good at intentionally seeming angry, unhappy, or afraid. As the Dutch authors point out, “although deceivers are less successful in faking negative emotions, naive observers do not seem to notice” (p. 3).

Despite these difficulties, Stel and van Dijk believe that observers could prove to be accurate when distinguishing between the emotional expressions of liars and truth-tellers if given the right instructions. Rather than ask people to state whether someone is lying or not, it would be better, they propose, to ask them to rate the extent to which that person is feeling the emotion purportedly shown on their face. Their study compared these two approaches to detection deception, believing that the indirect measure in which participants rate the extent of an emotion would provide greater accuracy than just asking participants to state whether the person they’re rating is lying or not.

In the first of two studies, undergraduate participants viewed videos of the faces of people who were lying or telling the truth, watching these without any audio. The videos were created by asking the “actors” to either lie or tell the truth about the way they were feeling after having watched a film fragment of either The Jungle Book (positive emotions) or Sophie’s Choice (negative emotions). The participants watching the videos then provided direct ratings of lying versus truth-telling and indirect ratings of the extent to which the person felt the depicted emotion. As predicted, participants were unable to provide accurate categorical judgments. When it came to rating the extent of the portrayed emotion, participants were more accurate in rating negative than positive emotional faces. This finding supports the idea that it is harder for people to fake a negative emotion.

The second study involved a larger number of participants, more video fragments, and a broader set of emotional ratings from the videotaped faces. The negative emotions scale included items that the authors believed would be relevant to deception, such as penitence, regret, guilt, sadness, anger, and worry. These findings confirmed those of the first study, showing that participants couldn’t tell whether the people in the videos were lying or not, but could rate whether the people in the videos were feeling badly or not.

In accounting for this effect, the authors return to the idea that perhaps people are just not that good at transmitting a lie when it involves a negative emotion. It is also possible, though, that observers change their approach when they’re rating the emotions of someone who seems sad, angry, hurt, or remorseful. It’s well known that people are better at making cognitive judgments when they’re in a bad mood. You remember more details, for example, of an important sports match when your team loses than when they win. When seeing someone who seems sad, emotional contagion sets in, and you feel bad as well. At that point, you’ll be better able to judge the nuances of what someone seems to be feeling. Good moods make you more global and, hence, less accurate in your judgments.

How can you use this study’s findings to your advantage when you’re in a situation of trying to infer whether someone is telling the truth? Start by not asking yourself whether the person is lying or not. Chances are, you’ll reach the wrong conclusion with this direct approach. Instead, take a step back, and see if you can gather which emotions the person you’re judging is actually experiencing. Although in the Dutch study, the videos did not include verbal narratives, in reality you are making judgments of people based on vocal as well as visual cues. Compare the emotion you think the person is feeling with the person’s words. When the person who hurts you expresses remorse, is that the emotion that comes to your mind too?

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Returning to the case of the supposed friend of your childhood friend, before you dismiss the person as a liar, see what emotions you're experiencing as you listen to the person’s narrative. If the emotions being expressed are positive, chances are you won’t be able to come up with an accurate judgment anyway, and it’s best to be cautious before revealing anything about your own past. Instead, turn the conversation to more negative experiences, and then see whether you believe the person to be sincere.

To sum up, it's hard to become an expert at detecting deception. However, by asking yourself a different set of questions than whether the person is lying or not, your judgments may come surprisingly close to the truth.