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3 rules to catch a liar

In a world where we assume people tell the truth, liars prosper. To stop them from exploiting others, here are three rules to catch a liar.
catch a liar
Credit: Elnur / Adobe Stock
Key Takeaways
  • It is estimated that the average person lies 30 times a day. It comes easily and naturally to most people.
  • Lying has obvious advantages, in that it exploits others and helps get you ahead of the game. But if you want to prevent being exploited, you need to learn to detect lies.
  • There are three rules to catch a liar: Keep them talking; listen to their feelings; keep them busy.

You will have lied at some point in the last week. Perhaps even today. But how big was it? Was it one of those small phatic lies, like, “Oh, I’m fine,” when you are actually sleep deprived, suffering from a throbbing headache, and bobbing in a choppy sea of anxiety? Is it a white, relationship-saving lie, such as, “You’re the only person I find attractive”? Or is it something much bigger — a crime, an infidelity, a betrayal, or a sordid secret?

Lying is a hard trick to get right. Lie too much, and no one trusts you. Lie too little, and you get laughed at, called “blunt,” and shunned as socially inappropriate. We are a “truth-default” species, meaning that our default position is to believe what others say. We assume people are telling the truth. So, lying has to be deployed carefully and sparingly.

The liar’s advantage

If life is a computer game, then lying is the cheat code. In a world governed by truth-default theory, the deceiver is king. We lie to get ahead in life and to get an advantage over others. For instance, lying about an infidelity keeps the family together and avoids that messy, expensive divorce. “Exaggerating” your qualifications gets you a much better paid job. Saying that you’ve read War and Peace when you’ve only watched the TV adaptation makes you sound intelligent, educated, and determined.

With such benefits, it’s no wonder that lying comes easily and naturally to us. Children as young as two years old will lie, and by eight years old, 80 percent of children will lie if they can get away with it. One study suggests that most of us lie at least once in a ten-minute conversation. That means most of us are throwing out around 30 fibs a day.

If lying is the way we get to the top and take advantage of each other, it pays to be able to spot a liar. When Simon is cheating at the game, we need to call him out. When Suzie is exploiting everyone else, we need to make sure she gets her comeuppance.

3 rules to catch a liar

A few years ago, a research paper came out that examined the various techniques used in “high-value detainee interrogation” — basically, how to interrogate the sort of bad guys you might see in a movie. Based on this research, we can summarize three rules to catch a liar.

Rule #1. Keep them talking

Outside of lawyered-up police interrogation chambers, most people will answer your questions. Rarely do we tend to answer friends or family with, “No comment.” While truth-tellers do tend to speak and reveal more, liars are often hesitant or unable to do so because “they cannot draw on real memories, lack the imagination to fabricate a detailed, plausible story, or fear that they will give themselves away.” What the study found is that letting someone talk reveals them as a liar far better than “accusatorial methods” (of the “I know you did it!” style).

So, if you want to spot a liar, be a good listener. Ask questions. Keep them talking. But, if you really want to spot a liar, you need to ask “unanticipated questions.” A liar, especially a practiced one, will have a script ready. They have a pre-fabricated yarn, and they’re going to spin it. To prevent this, you should ask about less pertinent aspects of a situation. If they were at a restaurant, what color were the chairs? If they were staying with friends, in which bedroom did they sleep? What did it look like?

Rule #2. Listen to their feelings (or lack thereof)

In the interrogation literature, there’s an idea called “reality monitoring.” This concerns the “process by which an individual attributes a memory to a real experience or to imagination.” Essentially, it asks us to consider how we store memories compared with how we store fictions. One key insight is that when we recollect a true memory, we reference sensory details (how things looked, smelled, etc.), as well as how we felt about a specific event. On the other hand, when we’re rattling off a made-up narrative, we often use “cognitive operations,” which are much more logical and matter-of-fact.

For instance, let’s suppose you’re talking about walking home from the cinema. If it is a true memory, your recollection likely will focus on the sound of the bus splashing a puddle or your grumpiness at being wet. If it’s a falsehood, your story more likely will be of the form, “It was raining, so I must have had my umbrella.” Truth-tellers tend to include sensory descriptions; liars do not.

Rule #3. Get them busy

The “cognitive load model” of deception holds that “lying is multi-tasking and for that reason difficult. Liars must plan what they say, remember to play a role, and suppress the truth.” The idea is that if you want to spot a liar, you need to make their lying harder. To do this, give them other tasks to do as they are telling their story. If their brain is too busy doing other things, they won’t have enough mental resources left over to lie — or, at least, lie convincingly.

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So, if you suspect your partner of cheating, ask them questions while they’re driving. If you think someone is inventing an alibi, get them to retell the story backwards (which is much harder, cognitively).

Liar, liar

It is true that humans are good at lying, and the corollary is that many people are good at telling if someone’s lying. There’s a small army of micro-gestures, pauses, turns of phrase, and so on that we’re all attuned to, and these three rules can improve your lie-detecting ability.


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