How to tell if someone is lying, according to experts

When it comes to the art of deception, there are a few tell-tale signs that your friend, family member or foe isn't being entirely truthful. But how do you know if your friend is fibbing, if your teenager is being a little too flexible with the truth, or your colleague is feeding you a cock-and-bull yarn? 

According to experts, it is possible to train the brain to spot a lie - if you know the warning signs. On average, humans are only able to catch a fib in the act about 50 percent of the time, while people with honed lie-detectors can typically tell tall stories from the truth 90 percent of the time. 

And while we all know lying is wrong, it's something we do from a very young age.

"Around the age of about three or four we start to understand that other people have minds that are different to ourselves… and that means we can actually trick other people by giving them the wrong information," Penny van Bergen, an associate professor of psychology at Macquarie University, told The Project.

Not all lies are created equal, either, with Prof van Bergen adding: "Very often we might think the truth might hurt somebody."

A UK survey found around two-thirds of us think lying to spare someone's feelings is fine: 61 percent of men and 60 percent of women. However, fewer think it's okay to lie to cover up a mistake: just 25 percent of men and 22 percent of women.

The research also found that 69 percent of people think it's unacceptable to lie about your age or appearance on a dating app, while 39 percent of men and 40 percent of women think it's okay to lie to take time off work.

Sometimes, little white lies are inevitable - and they can seem pretty harmless. If someone asks you if they look good in the dress, it often feels easier to say, 'Yes!' when your brain is saying, 'No!'.

"There's a sort of a balance here, we want to be talking to people about the value of telling the truth... particularly when it's legal systems, exams, those sorts of things," van Bergen said. 

Big deceptions are a bit more concerning: extensive lies can cost billions of dollars, and even destroy lives. For example, Bernie Maddoff's ponzi scheme started as a series of little lies that went on to help spark the 2008 recession. Last year, crypto-count Sam Bankman-Fried lied about how much money he had, destroying the dreams of credulous investors. And of course, every few years someone makes headlines for lying on their CV.

"I think when it's a big lie these are the sorts of things that extend on from the things we might tell ourselves when we're younger, and often those are for personal gain," van Bergen said. 

In the end, the world's built on bullpucky - but what are these ways to bust liars in the act?

How to spot a lie

According to body language expert Steph Holloway, it is possible to detect a lie through a person's body language. 

"Common things that come up when you talk about deception are that the blink rate changes: the average human blinks about 16-20 times a minute, that goes up when people are stressed, when they're in the process of lying. However, if it's a big lie, people can also neutralise: they slow everything down," she told The Project. 

"The average human doesn't have the mental capacity to formulate, remember, and tell the lie and control their body language at the same time."

The face can also be a dead giveaway: according to Holloway, a key thing to look out for is "squelched expressions", or in other words, indicators that the person is trying very, very hard to control their facial expressions and remain deadpan. 

"The face does lots of things called 'squelched expressions' where you don't want to form the full micro expression, so you just squelch it. For example, if you felt disgust at something, instead of screwing up the nose, they would just twitch the nose," she explained.

If you're a naturally nervy or anxious individual, sometimes your body language may have sleuths think you're telling a trumped-up story: but there are some key differences.

"I feel sorry for these people: a lot of the signs of deception are already there anyway. There's a couple of major differences though. One of them is that people self-soothe when they're out of their comfort zone: they give themselves little pats or rubs on their hands or arms. They're saying to themselves, 'you've got this, you're okay'. Or they'll play with objects, maybe something around their neck or their earrings. That's the main difference I'd look for in nervousness as opposed to deception."

People telling a porkie also tend to touch their face, Holloway noted, and their demeanour and body language may not match up with their dialogue.

So if you want to lie smoothly and successfully, "make sure you don't touch your face too much", and "try and make the inner monologue match what people see [on the outside], because this is what trips a lot of people up", Holloway said. 

Watch the video above.