Source: Big Idea Club

1. The secret to lie detection is making the other person think hard.

College students lie in about a third of conversations. For adults, it’s one in five. Whom do you lie to most frequently? That’s mom. You lie to your spouse the least, but you tell them the biggest lies, and you’re on the receiving end of about 200 a day. (This is not one of them, I promise.) Now there are a lot of myths around lie detection. A lot of people believe liars won’t look you in the eye, but that’s not true. Research says gaze aversion has never been shown to be a reliable indicator. In fact, a 1978 study of incarcerated psychopaths found they look people in the eyes more often than non-psychopaths when lying.

The biggest myth we deal with is that stress is an indicator of lying, but that’s never been shown to be true. Stress is what the polygraph detects, and one of the people who invented the polygraph was William Moulton Marston, who also created the DC Comics character Wonder Woman. Well, he probably should have stuck to that character’s lasso of truth, because it worked—and the polygraph doesn’t, according to research. The thing is, stress isn’t going to tell us who’s lying or not. People can get stressed for many different reasons, and we can’t be sure that a lie they may be telling is causing it. What does detect lies consistently is what’s called “cognitive load.” Basically, that means thinking hard.

Telling lies takes more cognitive horsepower than you might imagine. You need to think about the truth. You need to think about the lie you’re going to tell. You need to update the lie in real time. You need to make sure the other person’s not catching on. Lying takes a lot of thinking. So instead of asking yourself, “Is this person lying?” ask yourself, “Do they have to think hard?” A study by Aldert Vrij showed getting police officers to focus on the second question markedly improved their lie detection skills. So how could we do this most effectively? One tip is to use unanticipated questions that make someone think. A liar can’t prepare for every question that you might ask them. Research shows that airport security usually detect less than 5 percent of lying passengers, but when screeners used unanticipated questions, that number shot up to 66 percent.

How do we do this? Imagine you were a bartender, and someone comes into the bar who’s clearly underage. You might ask them how old they are, but they’re just going to say, “I’m 21.” What if you used an unanticipated question? Instead of asking their age, ask “What year were you born?” That’s a really easy question for someone telling the truth to answer, but it’s harder for a liar. They’re going to have to think for a second, and probably do some math. They’re going to slow down. That’s going to be obvious, and it’s going to be much easier to detect their lies. So when you think someone’s lying, ask an unanticipated question.

You can also try asking a question that could be verified. If someone says, “I was at that meeting yesterday,” you could say, “Was Carol wearing that scarf she always wears?” A liar knows this is dangerous. This is something that could be verified. This is something you can check on. Asking unanticipated questions that make liars think hard is a great way to get closer to the truth.

“Instead of asking yourself, ‘Is this person lying?’ ask yourself, ‘Do they have to think hard?’”

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