(CNN)What were you doing between 10 and 11am yesterday morning?
Once you recall this, could you describe it in reverse order starting midway through that hour?
How you’d go on to provide this information would reveal a lot about you. The details would not only describe your life, or your morning routine, but the person listening to your response could use them to decipher how much of it is true.
Your response could easily let slip if you’re lying.
“[It’s about] outsmarting the liars,” said Aldert Vrij, Professor of applied social psychology at the University of Portsmouth. “[We] ask questions, or give instructions, that are more difficult to answer or address by liars than truth tellers.”
This includes setting challenges in addition to the questions, such as having someone tell their story backwards while instructing them to be as detailed as they can.
“Increase the cognitive load to push them over the edge,” said Geiselman.
This is thought to leave people having to think heavily while sticking to their story and simultaneously watching you for your reaction, but this is just one part of the approach. Following swiftly is the need to encourage interviewees to say more and ask unexpected questions, according to Vrij.
“I like encouraging interviewees to say more as it addresses two important issues at the same time: it makes interviewees provide more information… and results in cues to deceit,” said Vrij.
Another tactic is asking someone to describe an event that police can verify, to then obtain evidence for it occurring, such as asking their whereabouts and tracking down CCTV footage. “Truth-tellers give more verifiable detail than liars,” said Vrij. “[In addition] it focuses on evidence to demonstrate whether someone is telling the truth or lying.”
No truth in sweat and machines
When most people think of someone lying they envisage sweating, lack of eye contact and rapid heart rate, all detected by hooking the person up to a polygraph machine.
But Vrij and Geiselmen steer clear of these strategies.
“[They] are based on arousal and anxiety and the idea that liars are anxious,” said Vrij. “The problem is that truth-tellers can also be very anxious in interview settings due to the fear of not being believed.”
Vrij adds that there are also many myths around behavior and deception that are not diagnostic and are also not supported by evidence for their accuracy. He argues this communicative approach, looking for verbal cues of deceit, is more reliable.
It has now been adopted by police, military and intelligence agencies worldwide, according to the Economic and Social Research Council (ESRC) who funded Vrij to conduct his research.
“[Cognitive interviews] are pretty much all that works reliably,” added Gieselman. “All else you find out there is simply snake oil by folks trying to earn a living teaching something about detecting deception for a buck.”
If you find yourself caught in a lie — be it to a police officer or your partner — prepare for your brain to be tested more than you could ever expect.