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The Newest Way to Tell When Someone Is Lying to You

New research on deception suggests how you can detect a liar just by listening.

Source: bbernard/Shutterstock

The subject of lying is receiving renewed attention with the recent public scrutiny of Michael Cohen’s testimony to Congress. He’s lied once before, but is he lying now when he says he didn’t ask President Trump for a pardon? The answer people give to this question falls along typical partisan lines, but is there an objective way to know? The recent college admissions scandal, in which wealthy people cheated the system to ensure their children were accepted by some of the country's top universities, also involves the act of deception. Admissions officers reading the applications of these high school seniors believed that their test scores, bios, and even photos were honest rather than the product of elaborate fabrications.

In your own life, the question of who’s lying can also have vital importance. A very close friend agrees to go out to dinner with you, but at the last minute bows out due to a sudden “illness.” Was it really an illness, or did your friend bail on you for another reason? Was it something you did, or did a better invitation come along than the one you were offering? Perhaps someone is doing some repair work on your home and promises to come first thing on Tuesday. However, Tuesday comes and goes, and the repair person never makes it. When you call to ask why this happened, you receive a vague answer full of excuses and another promise to come on Thursday. Is this also a lie?

The topic of deception continues to receive widespread attention in psychology, particularly in the intersection of psychology and the law. In a newly published study, University of Bergamo (Italy)’s Letizia Caso and colleagues (2019) sought to determine whether liars can be exposed by comparing their lies to other statements that they make in conversation. The Italian authors note that the cues to deception as tested in experimental methods by psychologists are “faint and unreliable,” and that “truth tellers and liars do not differ much” (pp. 1-2). Indeed, even police officers interrogating suspects aren’t all that good at digging for the truth, they claim. It is typical for forensic investigators to rely on the “small talk baseline” in which they ask nonthreatening questions followed by questions directly aimed at uncovering the truth about the crime. With these two samples of behavior in front of them, the officers then compare the suspect’s behavior during small talk with the behavior the suspect shows during the investigative portion of the interview.

As Caso and her colleagues note, the small talk baseline technique suffers from several problems, making it an unreliable method. One of its greatest limitations is that the investigation portion of an interview has far higher stakes than the small talk portion, and suspects know this. They can easily cover up a lie during the investigation because they know that they’re being asked about the crime itself rather than some incidental information that doesn’t matter. A seasoned criminal will glide through the investigation because the questions are so obvious. On the other hand, an innocent person telling the truth may be nervous throughout or become nervous when the questions take a serious turn. Returning to your own situation, that dinner partner who’s trying to cover up a lie can keep up the guise without blinking an eyelash when you change the subject to make it clear that you’re trying to expose the deceptive excuse. In other words, the small talk technique does not produce information that you could trust if you were to apply it to the liars you suspect in your own life.

The alternative, according to the Italian researchers, involves a “comparable truth baseline” in which the interviewer talks about similar topics within the same portion of the interview rather than switching from casual to interrogative questions. Mixing it up allows the context of the questioning to remain stable and is more likely to catch the liar off-guard. As the authors point out in an earlier paper (Palena et al., 2018, p. 125), “Comparable means that the baseline the investigator uses must be similar in content, stakes, and cognitive and emotional involvement to investigative questions.” Unlike the baseline method, you can’t seem to be asking casual questions and then get serious when you’re using the comparable truth method,

To test the ability of observers to detect deception in the two interview-type situations, the experimental team devised a complex scenario in which participants in a prior study were instructed either to lie or tell the truth about a set of actions they performed in a treasure-hunt type of task that contained a series of very specific instructions. Each step was dictated to the participant by the prior step, such as finding a key to a safe deposit box, opening the box, and following further instructions written on a piece of paper in the box. This provided the basis for participants to tell enough lies, or the truth, under the interview condition to which they were assigned. This interview, which was videotaped, took place in the comparable truth or small talk condition. Videotapes of 10 of these sessions were shown to 74 participants in the Caso et al. 2019 study. The participants watching the videotapes attempted to determine whether the individual was lying or telling the truth. For the comparable truth condition, the interviewer asked an open-ended question about the tasks themselves, and in the baseline small talk condition, participants were asked about school or work and then separately asked to describe what they did in the treasure hunt-like task.

In the prior experiment, raters coded the liars vs. truth-tellers along the nonverbal scales of hand/finger movements, one-arm movements, two-arm movements, spatial details, temporal details, visual details, audio details, and action details. Liars and truth-tellers behaved identically in the small talk condition of this experiment. By contrast, in the comparable truth condition, liars did a poorer job of describing information about the place and/or the arrangement of people and objects in the room. In other words, when asked to switch gears during the small talk method, liars were able to do so with relative ease. Raters who viewed those 10 sample interviews similarly were better able to detect liars in the comparable truth vs. small talk tasks.

It is possible that lying in the small talk method is easier because it gives the liar a chance to regroup and get his or her thoughts together while answering a set of innocuous questions. Keeping up with the small details in a focused set of questions about a particular incident also is more cognitively draining. Working memory involves keeping one set of facts in mind while you retrieve another; it’s only possible to hold so much in mind at a time. The liar therefore is forced to keep a running tab of what details were revealed, and so is more likely to make a mistake. When the observers in the Caso et al. study had to decide whether the people in the videotape were lying or telling the truth, they not only did a better job in the comparable truth vs. small talk situation, but they also performed at better than chance levels in identifying the liars.

To sum up, if you want to know who’s telling the truth, don’t bother trying to make inferences from hand gestures; other nonverbal cues have similarly not proven to improve people's lie-detecting radar. Because participants in the Italian studies who lied had the most difficulty getting the details right about the situations in which they found themselves, your best bet is to ask open-ended questions in which you obtain those all-important specific pieces of information. As the authors conclude, “Verbal content is more diagnostic than nonverbal behavior” (p. 7). When you get into the questioning itself, you can up the ante further by draining those all-important cognitive resources that the liar needs to try to hide the truth. You might start, if you want to be chatty about it, with informal non-event-related questions, but then get right into those details and don't let up. On the other hand, because it will be clear that you’re trying to get to the truth, you might decide it’s not worth it and wait to see if this happens again. At that point, you can pull out the stops with your “interrogation.”

Fulfilling relationships depend on partners being honest with each other. Knowing how to get at the truth can help you decide which relationships are the ones worth keeping.


Caso, L., Palena, N., Vrij, A., & Gnisci, A. (2019). Observers’ performance at evaluating truthfulness when provided with comparable truth or small talk baselines. Psychiatry, Psychology and Law. doi:10.1080/13218719.2018.1553471

Palena, N., Caso, L., Vrij, A., & Orthey, R. (2018). Detecting deception through small talk and comparable truth baselines. Journal of Investigative Psychology and Offender Profiling. doi:10.1002/jip.1495

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