Deep down, you probably believe you can sniff out lies like a bad smell. Perhaps inspired by Poirot or Sherlock Holmes, you may have confidence in your strong gut instinct and powers of deduction.
It’s okay if you do – you’re not alone. Most of us think we’re pretty great at lie detection. That was the conclusion of a 2023 study, in which 75 per cent of its 500 participants said they could spot lies well.
The problem is they were wrong – and so are you (probably). Most of us are actually rubbish at sorting fact from fiction. In scientific studies, members of the public who are asked to detect lies tend to have success rates of around 54 per cent.
“Empirically, people are bad at spotting deception,” says Prof Sander van der Linden, director of the University of Cambridge’s Social Decision-Making Lab. “If you look at meta-analyses, people do marginally better than chance. That’s pretty bad. We’re basically just guessing.”
If you’re a fan of the BBC’s The Traitors, you might already know this. Time and time again, contestants fail to recognise barefaced liars and vote out the wrong people instead, sometimes with surprising confidence.
But why? What do we miss when we’re looking for deception? It turns out, an awful lot – all while liars hone their craft.
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1. We're looking in all the wrong places
When trying to find fibbers, most people’s go-to strategy is flawed, says Prof Geoff Beattie, a psychologist at Edge Hill University.
“If you ask people, ‘How can you tell if someone’s lying?’, they always say the same thing: ‘people look away when they lie,’” he says. “Across a whole range of different countries and cultures, people believe that it’s the universal sign. But eye contact is a really poor signal of deception.”
Scientists have now known this for decades. Back in 2010, researchers from the City University of New York found that people tend to avert their gaze when remembering real memories, as well as falsehoods.
“Liars know that people look out for eye contact, so they use that to their advantage,” explains Beattie. “They can plan in advance what they’re going to say and maintain eye contact, whereas a truthful person might look away because they’re thinking.”
But eye contact isn’t the only behaviour that we mistakenly rely on. Many of us search for signs of emotion that we assume should coincide with lying – such as nervousness, anxiety or guilt.
“Some people get away with lying because they come across as really confident,” says Dr Sharon Leal, a forensic psychologist at the University of Portsmouth. “Most people don’t look nervous when they lie.
“A two-year-old child will look you straight in the eye and say that they didn’t eat chocolate, when they did. We learn very, very quickly to hide nonverbal behaviours.”
In fact, Leal continues, liars tend to be hyperaware of behaviours that might give them away – such as nervous fidgeting – and they cover them up.
“As soon as you think you might be doing these things, you monitor them,” she says. “So, a truthteller can look far more guilty than a liar.”
And, Leal adds, some people may not feel anxious or guilty when lying, particularly if they have certain dark traits – but more on that later.
But despite all this, many of us continue to search for subtle movements and micro-expressions that we believe might give away what someone is truly feeling.
We’re not totally misguided. Scientists have identified dozens of potential micro-expressions – brief, involuntary facial movements that might betray a lie – with Van der Linden estimating there are around 90.
Yet this abundance of cues actually makes detection harder. With so many fleeting expressions, you may scan for the wrong one – or fail to catch it before it disappears.
“A human can’t hold 50 or 90 cues in their own minds,” Van der Linden says.
Leal adds: “Unless it’s absolutely, really badly obvious, you’re very unlikely to detect deception from nonverbal behaviour.”
This is where technology can be helpful. In 2021, computer scientists trained an AI system to monitor 36 human micro-expressions and use them to detect deception. The result? An accuracy rate of 72–78 per cent – far from perfect, but significantly better than most humans manage.
2. We're distracted by our own biases
Ignore eye contact and micro-expressions – that’s easy enough. However, other potential pitfalls might be more difficult to correct: our own internal biases.
For starters, there’s the truth bias. First described in 2014, the truth-default theory posits that most of us simply don’t expect to be lied to in our day-to-day lives.
“In normal interactions, we don’t expect to be lied to, especially by people we think are nice and friendly,” says Leal. “We want to believe them, because that’s good for our self-esteem.”
It makes sense. Say you get a questionable haircut, give a lacklustre gift, or wear an unusual outfit. You’ll want to believe the friends who tell you they like it – no matter how unconvincingly – because those lies reassure your ego and strengthen your bonds with your support network.
But, while we’re more likely to assume that a person is telling the truth than fibbing, the strength of that assumption varies. Beattie says: “One of the first judgements we make about people is trustworthiness.”
How do we make that judgement? Leal explains that it has a lot to do with attractiveness; we tend to assume more beautiful people are more trustworthy.
But it can also be influenced by societal prejudices and stereotypes – for example, what we’ve been taught about different genders and ethnic groups.
We can see this play out in the microcosm that is The Traitors. As many viewers have noticed, people of colour are more likely to be accused of lying and eliminated from the show in earlier rounds.
Across all five series, The Times reported that 32 per cent of contestants have been non-white. But, out of the first 30 people to be voted out of those series, 14 – nearly half – were people of colour.
Those stereotypes aren’t insurmountable. In 2017, researchers at Miami University, US, found that white study participants were more inclined to believe a black person was telling the truth than deceiving them, even when underlying racial biases were present.
A follow-up experiment used eye-tracking software to confirm that white participants were quicker to look at the ‘lie’ response button when judging the truthfulness of a black person, compared to a white person. But the participants corrected that instinct.
“White people have this unconscious bias, so they might assume that black people or ethnic minorities are more likely to lie,” explains Van der Linden.
“But I guess the positive side of the story is that, in this particular study, people were able to consciously control it. Despite having this bias, they were less likely to say that black people were lying.”
There’s a lot that contributes to our assessment of a person’s truthfulness – and after that, confirmation bias comes into play.
“We make quick judgements about people and then we let those judgements guide our process of looking for information from them,” explains Beattie. “Once you assume that someone is trustworthy, you’re not looking for indicators of deception, and vice versa.”
That’s how we might convince ourselves that so-and-so is totally guilty, while ignoring evidence to the contrary and believing actual liars.
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3. We're missing key clues
While we’re being thrown off course by micro-expressions and biases, Leal says we’re likely to miss what really gives liars away: what they say.
“Whilst you’re concentrating on nonverbal clues, you’re going to miss verbal cues and contradictions,” she explains. “You’re far more likely to pick up on genuine cues if you’re listening to what they say.”
Liars often make mistakes when they’re talking, because all that yarn-spinning takes a toll on their mental resources.
In fact, brain-scan research shows that when we tell lies, we first think of the truth, then repress it, and finally formulate a lie – all of which takes more effort than simply telling the truth. And that’s not where that effort ends.
“In high-stake situations, a liar typically plans their lies,” explains Leal. “Then they have to concentrate on keeping their story straight, trying not to contradict themselves, keeping their own behaviour under check and watching your behaviour – all while suppressing the truth on a physiological level.”
That’s why, says Van der Linden, liars tend to try to keep their lies simple, so their stories are easier to remember and keep consistent.
He explains that ‘lack of richness in detail’ is one of the most reliable indicators that someone is telling a fib. That was the conclusion of a Dutch study from 2023, in which researchers instructed participants to use ‘detailedness’ – and nothing else – to help them sort lies from truths. This way, their accuracy rate improved from around chance-level to up to 70 per cent correct.
You can use that rule of thumb too. If you notice that someone is saying suspiciously simple statements, you can ask further questions and listen out for things that don’t make sense.
“One way to trip liars up is to probe them for detail,” explains Van der Linden. “They might give contradictory statements if they haven’t thought through their lie in advance.
“Then you can go back and say, ‘Hey, didn’t you say this before?’ It’s often what police investigators do. They write down what you say, and then if you say something different, they’ll probe that further, to get a sense of reliability.”
4. Liars learn but we don't
By ignoring the visuals and paying close attention to what your suspect is saying, you might get better at spotting deception. However, don’t be disheartened if you don’t instantly turn into Benoit Blanc, southern drawl and all. Some liars are really good at what they do.
Back in 1996, researchers discovered that adults lie more than you might assume – on average, once or twice per day. But further research has shown that we don’t all lie little and often.
In 2010, scientists at Michigan State University asked 1,000 US adults whether they’d told a lie in the previous 24 hours. They found that almost half the total lies were told by 5.3 per cent of respondents, while nearly 60 per cent said they hadn’t lied that day at all.
Of course, it may be that the 5.3 per cent were only the participants willing to admit how often they lie. But if the study actually reflects reality, it points to a small group who account for a disproportionate share of everyday deception.
Prolific liars, further research has discovered, are likely to possess personality traits associated with the ‘dark triad’ of narcissism, psychopathy and Machiavellianism.
“Everyone tells a few white lies every now and again,” says Van der Linden. “But most of the serious lying comes from a small group of people who do this on a regular basis.
“The reason why these people lie so often is for interpersonal exploitation; it serves a strategic goal to lie. They’re socially motivated to become good at it, because they want to exploit other people. That motivation can lead to practice.”
And a little practice goes a long way. That was the conclusion of a 2012 study, which found that participants could quickly learn to tell better lies – with less mental effort – after they tried it out a few times.
“People who lie often learn to do it better,” continues Van der Linden. “Sometimes they’ll get away with it and sometimes they won’t. But they get feedback on the efficacy of their lying, and they learn to adapt.”
But while liars perfect their craft, it’s very difficult to practice spotting lies.
“Feedback is very important,” says Van der Linden. “But you don’t get feedback when you’re trying to spot lies in real life. People don’t say, ‘oh, yeah, I was lying’. But feedback is crucial for learning.”
People are not Pinocchio
The cards might feel stacked against us; liars are just too clever, while we’re bogged down by bias. But there are ways we can tip the odds of lie detection in our favour: forget the visuals, pay attention to your prejudices, and listen carefully.
Even then, you might not sniff out falsehoods every time – but Beattie says it’s still worth trying.
“I think it is important we spot lies, because if we don’t we lose trust in people,” he says. “If politicians feel they can lie to us and get away with it, we lose trust in them and the political process. And lies are very personal, with all kinds of implications for families, for relationships, for how you live your life. That is a powerful thing.”
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