Ultra Petita: Where The Evidence Lies

Reading time: ~4 minutes

TLDR: Most people are so bad at detecting a lie, they may as well flip a coin. Unless you are a U.S. Secret Service agent, training and experience do not improve your ability to detect lies.

Cross my heart

Imagine that you are sitting in a hearing room during the cross-examination of a witness. The lawyer conducting the cross-examination reaches a hotly disputed issue. People focus and lean in. The tension in the room increases. The witness changes his posture, once, twice. He starts fidgeting with the pen on the table. As the lawyer coolly fires question after question, her confidence palpable, the witness’ shifts his gaze, seemingly looking for an escape. He blushes, and the rhythm of his voice varies as he stumbles over a few words here and there. His apparent ordeal ends after ten long minutes of this performance, when the arbitrators call for a break.

Now imagine that you could get the participants in that hearing room to vote, individually, on whether they believed the witness was telling the truth or lying. What would you vote? What would the majority vote? It’s likely that most of the room got the same impression, whatever that impression was. Studies show that people tend to agree on whether a person comes across as truthful or deceitful. Is the majority correct? That is an entirely different matter. After decades of research, it is now well accepted that virtually all individuals are barely able to detect lies.[1] In numbers, people average 54% correct judgments. Compare that with a monkey flipping a coin, who would get 50% correct judgments.

Why does this happen? Is there anything we can do about it? This is what I investigate in this issue.

Liar liar

If you’d asked me two months ago whether I could tell somebody was lying, I would have said something like “yes, probably”. Instinctively, I would have described a liar as someone giving away clues of their deceit. I would have said that liars tend not to look you in the eyes, but rather shift their gaze away. I would have added that liars betray themselves by their body language, fidgeting and changing their posture more regularly than an honest person. If you had pushed me further, I may have remembered that liars are described as pausing their speech or stumbling over some of their words. Admittedly, none of my views had any scientific or practical basis. I think my idea of a liar is a result of reading novels and watching films.

Scientific studies show that I am not alone. Researchers surveyed people in 58 countries and found that participants listed these behaviours as signs that someone was lying.[2] In fact, people in 51 of those countries reported pattern of eye movements (i.e., gaze behaviour) more frequently than any other behavioural clue indicating deception. The common conception of how a liar should act is therefore somewhat universal. Researchers have suggested that we list these behaviours, which convey nervousness and discomfort, because we expect liars to feel that way when lying.[3]

Considering this, detecting a lie seems straightforward. Is the would-be liar shifting his gaze? Fidgeting? Changing his posture? Stumbling over words? If so, he must be lying! And yet…

Here lies an honest man

Most behaviours that we describe as betraying a lie bear little or no relation to deception. As two of the leading researchers on the topic put it:

A meta-analysis covering 120 studies and 158 cues to deception showed that most behaviors are only weakly related to deception, if at all. Gaze aversion is not a valid indicator of deception. The simple heuristic that liars are more nervous is not supported by the meta-analysis because many indicators of nervousness, such as fidgeting, blushing or speech disturbances, are not systematically linked to deception.[4] (citations omitted)

So, this seems easy, we are just looking for the wrong clues when trying to detect a lie. Give us the right clues to look for and we will improve our lie-catching skills. But wait, not so fast. If you like irony, you will like what comes next.

When you ask people to list signs of deception, they will describe the characteristics discussed above (gaze, fidgeting, etc.). So, when you ask people to detect a lie, they should base their decision on those characteristics - BUT THEY DON’T! People do not really look out for gaze shifting, fidgeting, etc., even though they report that they do. Research suggests that people actually rely on different behaviours. In fact, people find speakers to be deceptive when they give an impression of incompetence or ambivalence, and when they provide implausible statements and lack spontaneity.[4] Moreover, the speakers’ physical appearance also plays a key role in whether they are judged as honest or deceitful.

Whatever people pay attention to when trying to detect a lie, there is a lot of evidence to support the conclusion that virtually everyone is barely able to detect a lie. As mentioned above, people average 54% correct judgments, when you could achieve 50% by flipping a coin. Put differently, human liars are better than human lie detectors. This finding apparently holds true across cultures.[5]

To summarise this mess: (i) people tell you they can catch a liar by looking for certain behaviours; (ii) those behaviours are not indicative of lying; (iii) which is irrelevant anyway since people don’t actually look for them when trying to catch a liar; (iv) and none of foregoing matters because it’s established that people suck at catching liars.

Catch me if you can

Researchers have investigated whether some groups of people are better than others at detecting lies. More than a few studies focus on police officers. Others involve polygraphers, judges, psychologists, investigators, etc. The only group that seems better than average at detecting lies was composed of U.S. Secret Service agents, none of which scored below chance and more than half of which scored above 70% accuracy (in the only study I found that included them).[6] (I am tempted to insert some joke about catching presidential lies here, but instead I will mind my own business.)

Aside from this anomaly, the occupation of the lie-detecting participant does not have any impact on their accuracy at detecting lies. Most professions do not better than college students. Strangely, no amount of training or experience in the field of lie-detection seems to improve accuracy much. It improves the participants confidence in their own ability to catch lies, but not their accuracy. They are just as wrong as anybody else, only more confident that they are right.

Basically, nobody should put any weight on their ability to detect a lie and there doesn’t seem to be much we can do about it.


This issue of Ultra Petita skims over a topic that warrants a deeper dive. While some are taking an interest in the memory process of witnesses in international arbitration (see this episode of the Arbitration Station), I have yet to see any literature on an arbitrator’s ability to detect deceit by a witness (or by counsel, should the need arise). The research indicates that we should approach any intuition regarding veracity or deceit – based on the impression speakers give when they deliver a possibly suspicious message – with a huge dose of caution. Arbitrators and lawyers are in the same boat as everybody else save possibly for the U.S. Secret Service: we may as well flip a coin when it comes to detecting deceit based on behaviour.

To end on an oversimplification, where a claim rests on equally probable competing witness testimonies only, the chance the arbitrators have of making the correct assessment of the truth (i.e., catching the liar) is not far from pure chance.


[1] C.F. Bond & B.M. DePaulo, Individual Differences in Judging deception: Accuracy and Bias, Psychological Bulletin (2008) Vol 134(4), pp 477-492.

[2] Global Deception Research Team, A World of Lies, Journal of Cross-Cultural Psychology (2006) Vol 37 pp 60-74.

[3] A. Vrij & G.R. Semin, Lie Experts Beliefs about nonverbal indicators of deception, Journal of Nonverbal Behavior (1996) Vol 20, pp 65-80.

[4] M. Hartwig & C.F. Bond, Why do lie catchers fail? A Lens Model Meta-Analysis of Human Lie Judgments, Psychological Bulletin (2011) Vol 137(4), pp 643-659.

[5] C.F. Bond, A. Omar, A. Mahmoud & R.N. Bonser, Lie Detection Across Cultures, Journal of Nonverbal Behavior (1990) Vol 14(3) pp 189-204.

[6] P. Ekman & M. O’Sullivan, Who Can Catch A Liar?, American Psychologist (1991) Vol 46(9), pp 913-920.