Let’s keep it simple and talk about a husband you suspect is behaving badly.

He comes home late again. You ask the usual 20 questions, which he smoothly neutralizes with a detailed and more or less plausible story.

It really seems like the excuse writes itself.

Next, try this: create a small emergency requiring him to multitask while explaining his quirkiness.

According to new research, “lie counters who have to multitask while being interviewed are easier to spot.”

In other words, if someone is trying to spin a story to support a lie, and if they can be distracted by something that really needs their attention (while simultaneously trying to keep the story in play), the plausibility must fall apart from the lie.

It’s clunky, but it just might work.

But how does it work?

Previous studies have shown that our brains are wired to tell the truth because lying takes more cognitive energy.

If there is an easier and cheaper way to do something, the body will choose that route. It’s all about saving energy.

What is the proof?

Neuroimaging has shown that our brains are more active when we tell lies, especially in the prefrontal cortex.

These brain studies have also shown that lying takes longer than telling the truth.

And that’s the liar’s weakness.

The new experiment

Psychologists at the University of Portsmouth recruited 164 participants in an experiment that went like this:

The participants were asked to give an honest ‘yes’ or ‘no’ opinion supporting or opposing various social issues in the news. These include “Women should have the right to abortion,”; “The death penalty should be a legal option in very serious criminal justice systems,”; “The smoking ban in public places is a good thing,”; and “Obese people should pay for their own health care.” The participants were then randomly assigned to a ‘truth’ or ‘lie’ group and interviewed about the three topics they thought most about. Truth tellers were instructed to give their true opinion, while lie tellers were asked to lie about their opinion. Some participants were given a secondary task: calling out a seven-digit car registration number. Half of them were told that if they couldn’t remember the rego number, they had to write down their opinion after the interview, which was considered a hindrance and therefore motivated them to get the number right.

The results

The results found that “lie tellers’ stories sounded less plausible and less clear than truth tellers’ stories, especially when lie tellers were given the secondary task and told it was important”.

The pattern of results suggests that “introducing secondary tasks in an interview might facilitate the detection of lies, but such tasks should be introduced carefully”.

Professor Aldert Vrij, a professor of psychology who designed the experiment, said: “Our research has shown that truths and lies can sound equally plausible as long as lie tellers are given a good chance to think about what to say.

“When the ability to think diminishes, truths often sound more plausible than lies.”