A Sneaky New Way to Recognize a Chronic Liar

It’s a truism in psychology that everybody lies. Whether the odds are 70%—a typical estimate—or even higher, depends on the exact method used to detect deception. However, there’s “lying” and there are “liars.” You might slide into a little lie to preserve a relationship (“I love that shirt,” though you don’t), or to get out of an obligation you’d prefer not to make (“So sorry, I’m busy that night”). This innocent enough type of lying isn’t the same as the outpouring of untruths produced by the chronic liar. To such an individual, lying comes so naturally and so frequently that the truth is less likely to emerge than a fabrication.

The act of lying, when it occurs occasionally, may reflect an insignificant blip in the life of an otherwise upstanding individual. Your radar probably won’t be attuned to detecting a lie from this person because you’ve come to expect mostly truths. With the chronic liar, though, you doubt whether anything at all has even a kernel of truth. You might also wonder what it is about this individual’s personality that makes them so allergic to honesty.

The Devil’s Advocate and Detecting Deception

According to a new study by the University of Portsmouth’s Sharon Leel et al. (2025), an interesting variant of deception occurs when people express their opinions. In an extremely polarized society, this type of sliding off the truth can be particularly frequent, no matter how honest someone usually is. You can relate to this situation if you think back on a conversation with a person you didn’t know very well as the topic shifts (maybe painfully) to politics. Rather than come out with your actual opinions, you tiptoe into things, ready to jump back out should it be clear this person has a set of beliefs opposite to yours. But would you go so far as to agree with the person, disguising your true sentiments? The answer might depend on whether you lie for the sake of lying, or whether it’s a high-stakes situation in which you can’t afford to lie (such as meeting your new romantic partner’s parents).

The Portsmouth research team decided that lies about opinions could provide a ripe area to explore in the field of detection of deception. They invented what they called a “Devil’s Advocate Approach,” an interview-based technique in which people are asked to explain the basis for their opinions about a matter, and then to argue for the opposite opinion (hence, “devil’s advocate"). Because the paradigm only asks for hypotheticals, it doesn’t fit what would be a deceptive task. Normal deception experiments ask people to either tell the truth or not, such as reporting on how much they're entitled to in a gambling experiment. The Devil's Advocate task forces people to tell the truth by lying.

Testing Liars in the Devil’s Advocate Task

Because chronic liars so easily say the opposite of what they think, it shouldn’t be a great stretch for them to play devil’s advocate—in contrast to truth-tellers, for whom this could be a painful ordeal. In their experimental (and pre-registered) study, Leel and her colleagues asked their online (and Zoom-based) sample of 170 participants (average age 28) first to complete an interview based on an opinion they previously expressed in a questionnaire. Some of the opinions participants were told to argue for or against included being able to trust the government and regarding closed-circuit television monitoring as an invasion of privacy. For the interview, they were randomly assigned to a truth- or lie-teller condition. Within these conditions, they also received prompts to express their opinion either just by listing all relevant reasons, or by providing those opinions in a way consistent with a “model statement,” forcing them to provide extensive detail to back up their opinions.

The research team used the video and audio recordings to rate the responses on the qualities of number of supporting arguments (a reason either for or against the opinion), along with plausibility (reasonable and genuine), immediacy (personal vs. distant), clarity, originality, and passion (enthusiasm). Plausibility, immediacy, and clarity became coded into a variable called eloquence, leaving the final tests between liars and truth-tellers to comparisons on eloquence, originality, and passion. Following the interview, participants rated themselves on an 11-point scale (0 to 100%) to indicate how much of the time they lied as well as whether they thought the interviewer believed them.

The findings showed not only that the devil’s advocate paradigm provided distinctions between liars and truth-tellers, but that the model statement condition accentuated the effect. Participants instructed to lie didn't differ much in their ability to concoct supporting arguments in terms of eloquence and enthusiasm, but those in the truth-telling condition struggled in all three measures. The liars did show one key subtle "tell": When arguing for the devil's advocate position, their communication lacked passion compared to their delivery of the truth. As the authors concluded, "When people express an opinion they strongly believe in, they may do so with passion. Lie tellers, who do not believe what they are saying, may show less passion." Things only got worse for the liars when they had to elaborate on their opinions. The model statement condition, forcing them to provide extensive detail, resulted in even greater exposure for the liar in terms of originality, eloquence, and passion.

Using Your Own Devil’s Advocate Detectors

The British study, by forcing liars to tell the truth (i.e. the opposite of their beliefs), provides an intriguing inroad into the verbiage and tone of falsehoods. Although prior researchers often focus on nonverbal cues and/or verbal inconsistencies, that rating of “passion” can be the true tip-off. Liars will tell a lie with about as much enthusiasm and eloquence as the truth. People telling the truth will light up when saying how they feel, but struggle when they have to pretend to feel the opposite. As soon as you sense the heating up of an individual's inner fire, chances are they're on a clear pathway toward the truth.

One of the helpful features of the Leal et al. study is that it doesn't force you to study eye gaze, fidgeting, or the almost indiscernible category of microexpressions. Just listen, and preferably allow the other person to speak long enough to run out of supporting fabrications. This study can also steer you toward finding out the people you want to get to know by figuring out what they really think about issues that are important to you,

Deception Essential Reads

What I Learned From Being Catfished

The Best Way to Spot, and Stop, a Liar

To sum up, deception doesn’t only involve lying about events. To the extent that you can trap a liar by forcing them to tell the truth, you may find an unexpected tip off not just in what they say, but how they say it.

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