Research shows that we’re about as good at detecting lies as we are at guessing heads or tails in a coin flip. And even if our gut feeling is correct, the harder part is getting the liar to admit to any wrongdoing — especially when they could just double-down and make us doubt our perception of reality.
Getting a gaslighter to own up may seem like the most infuriating fool’s errand, but a new study suggests a much simpler way to expose a liar: Force them to remember and recall a seven-digit car registration number.
That might sound oddly specific, but hear the researchers out. Although some people might appear to lie with great ease, there’s ample evidence that deception takes up more mental energy than telling the truth. That’s what prompted social scientists at the University of Portsmouth to ask: What if these liars lost that mental energy elsewhere?
To test their theory, psychology professor Aldert Vrij and his team interviewed 164 people about their levels of support or opposition about certain topics in the news. Then they were randomly assigned to either tell the truth or lie about three of the topics they were most passionate about. All of the liars were told that they’d be entered to win a prize if they were particularly convincing.
Of the 82 participants who were instructed to lie, 29 of them were told to do nothing other than be deceptive, whereas the remaining people were told to memorize a seven-digit car registration number. Of those, half were notified that if they didn’t remember the number, they’d have to write out their opinions on the current events.
Overall, liars were less believable when given a secondary task, especially when that task was supposed to be important. “Our research has shown that truths and lies can sound equally plausible as long as lie tellers are given a good opportunity to think what to say,” Vrij said in a press release. But by giving a gaslighter something else to think about, it decreases this opportunity. “The pattern of results suggests that the introduction of secondary tasks in an interview could facilitate lie detection but such tasks need to be introduced carefully.”
So before you start asking your significant other to memorize a series of numbers, the hard part isn’t going to be explaining to them why you’re asking them to perform such a seemingly pointless mental exercise. The challenge is that in order for it to be an effective lie-detection strategy, they have to care about the task, and care with a sense of immediacy. Because as Vrij explained, “Secondary tasks that do not fulfill these criteria are unlikely to facilitate lie detection.”
This obviously cuts both ways, too. So the next time your partner starts grilling you while you’re doing something you really love, be ready to give them your full attention immediately or to tell the truth, the whole truth and nothing but the truth.