Liar liar: the science behind why we fib

EDGAR investigates how to tell if someone’s lying to you, and the trick to beating a polygraph.

Peter Iantorno December 8, 2014

From the harmless white lies we all tell from time to time, to the larger malicious untruths people use to cover their own backs, lying comes in many different shapes and forms.

But what's the best way to spot a liar? Many people think that a lie detector is the most accurate. However, apart from the fact that hooking someone up to a polygraph is far from appropriate behaviour for anywhere outside of a police questioning room, if someone is a well-practised fibber, the machine might not catch them out anyway.

The scientific approach

When a person tells a lie it sets off a complicated reaction inside the brain. Firstly, the frontal lobe - associated with suppressing the truth - becomes activated, then the limbic system, which controls the anxiety a person has when lying, also starts working. Meet the Parents polygraph scene With someone who is telling the truth, there will be much less brain activity, with the main work coming from the temporal lobe, which is associated with memory retrieval. However, pathological liars are so well versed in bending the truth that their brains have adjusted so that even when they're lying, the limbic system does not activate, they don't get stressed and a polygraph won't be able to detect anything.

Body language

While machines are easily tricked, if you know the right body language to look for, it is possible to increase your chances of spotting a liar. For example, if a person begins to fidget - moving their feet around and subconsciously touching their face - that shows that they're uncomfortable and therefore may well be lying.

Looking closer, if their eyes move to the left, or upwards and left, that could indicate that they're trying to construct an image or sound that never actually existed, whereas if a person's eyes move to the right, or up and right, that could show that they're trying to recall events that really happened. If a person's pupils dilate, that could also indicate a possible lie.

Verbal Sometimes a liar will trip themselves up and reveal the truth with a slip of the tongue or even in the way they say something. A higher tone than normal is a classic sign of lying, and liars are also noted to use fewer contractions - a certain former US President's "I did not have sexual relations with that woman," springs to mind...

Sometimes a liar will even get so mixed up that their words will not match their actions, and they end up subconsciously shaking their head while insisting that you've got their full support at work, or frowning when claiming to be happy with the review you've just given them. Bill Clinton Behavioural changes

As we've mentioned above, there are a whole host of possible signs that someone is lying, but even the most finely tuned human lie detector can still easily get it wrong relying on those methods. The only real way of spotting a liar relies first on getting to know their usual behaviour.

If there are any big changes - making lots of eye contact when usually the person makes very little, or talking slowly and precisely when usually the person is a fast and animated talker - then it's likely they are lying.

Of course, the big problem with this is that you need to know the person pretty well before you can make an accurate assessment. If you've not got this luxury, a quick way to find out their usual behaviour is to ask them questions you know they won't be lying about - 'what are you up to this weekend?' or 'have you tried that new restaurant?' - then hit them with the question you really want to know the truth about and see if their demeanour changes. Hugh Lawrie House. If you catch someone out...

The natural reaction might well be to confront them immediately or shop them in so everyone hears about their deceit, but in most cases that's not going to help either of you. A confrontation is only going to create conflict, and without evidence it may be their word against yours; even if you do have evidence of a lie, do you really want to be the person known for snitching on every little indiscretion?

Unless you know that the issue can only be solved with the liar being outed, a much smarter way to play it is to keep your concerns to yourself, but just give the person a wide berth in future and know that they can't be trusted or relied upon to help you out.

While all of the above methods have been proven to work on some level, and certainly come in handy when trying to find out who the snakes in the grass are, we have to say that the best tactic will always be to follow your gut. If you don't like the sound of what someone's saying and you reckon they're feeding you lies, they probably are.