How to tell if someone is lying… maybe.

February 28, 2011 at 5:28 pm 4 comments

Jeremy Kyle. Jerry Springer. Trisha. What do they have in common?

All of those daytime talk show hosts use something that fascinates all human beings. A lie detector.

We find it almost shocking to think that a machine may actually see through our deception. Is it that obvious that you’re telling a lie? Can a bunch of wires and a polygraph really see through even the most cunning liars?

Well, in honesty, there is probably no such thing as a 100% correct lie detector – even the talk shows say they’re only 98% likely to be correct. Is that figure even remotely close to it’s accuracy? I’m very skeptical. Many critics disregard the lie detector as rubbish, it’s simply not a scientific procedure. There’s certainly no conclusive evidence that they DO work.

But what about humans?
We all lie at some point, so surely we’d be better at detecting lies than a machine that doesn’t know what it’s doing?

Lie detectors test for physiological changes in skin temperature and sweat, amongst other things. They're often disregarded as inaccurate and lacking scientific methodology.

Well, there is no lack of literature on the different body signs and gestures that supposedly capture lying behaviour. Firstly, I will write about the basic signs that someone might be lying, which are usually included in most body language literature. Then we will come to a conclusion about how accurate it really is…

What are the signs someone might be lying?

Evasion of eye contact.
It’s very hard for most people to feel totally fine when they tell a lie.  Things just become awkward and tense, especially during lies that might have bigger consequences. It is deemed “average” for someone to keep eye contact for over 50% of a natural conversation, so if someone spends most of their time looking away, things are looking a little suspicious… On the flip-side, those of us who are well read on lying body language might attempt a double bluff. In other words, they will make every effort to keep eye contact to look like they’re not lying. Remember, about 50% of a conversation is natural eye contact. Too much or too little might indicate some porkies going on.

Unusual body language.
All of us act differently in social situations. Some are more relaxed than others, some find speaking difficult and awkward. But, if you know someone quite well and they’re acting a little “off”, there’s usually something not right. During lying, the body usually stiffens, the liar will cross their arms defensively, and they take up less space by moving their limbs close to their body. They tend to fidget (tap their foot, click their fingers, twiddle their thumbs), blink more often and sometimes cover their mouth or touch their face.

Inconsistent emotional behaviour.
It’s much harder to fake emotion than it might first seem. Like when you get that birthday present that makes you cringe, but you need to act like you love it. The liar will often mess up the timing and duration of emotional reactions; so emotion may be delayed, last too long/not enough or just end abruptly. The mix of emotional gestures and words can also become inconsistent. Someone might, for example, say “it’s beautiful!” before smiling a few seconds after. Usually, you’d do both simultaneously. Look for muscles in the face as well. When you fake a smile, you use only the muscles in your mouth; real smiles use many more in the eyes, cheeks, jaw etc.

As can be seen by my stunning modelling above, it is probably quite easy for most of you to see which is the real smile (you really don’t want to know how long I sat there pulling ridiculous faces to myself until I smiled…) The answer can be seen by left clicking and highlighting over the space between the arrows:

>>  B is the real smile <<

In the real smile picture, my eyes squint more, my mouth opens wider and my cheeks ‘ripple’ slightly (definitely a big hint if you haven’t worked out the real one already…) In older people, wrinkles may become more defined on their forehead for a real smile.

Guilty people get defensive, innocent people go on the offensive.
Pretty self explanatory. Suppose some chicken nuggets of yours have gone missing, and you ask a suspect “did you eat my chicken nuggets earlier?”. The guilty party will likely respond “What? No, I didn’t eat them, what do you mean? How could it have been me, I was… erm, out at a lecture all today. It definitely wasn’t me! Why are you picking on me?”. They may also simply refuse to answer, or accuse you of being the real liar.

Someone innocent might respond more offensively: “What? Of course not! I wouldn’t trust John though, I saw him snooping in the kitchen at around the time you were gone, and he did have breath like chicken nuggets just before!”

Their language use and conversational style is different.
Liars will often speak slower and in a different pitch or tone than usual. There will be many er’s and umm’s whilst making the story up as they go. Truthful people will have little trouble remembering recent events and will speak without much thought. Liars will often add useless details to a story to make it seem more “real”, like the colour of a car they drove or the length of someone’s hair (unless of course the lie involves the car colour or hair length).

Contracted sentences are usually TRUTH – so using words like “didn’t” rather than “did not” and “wasn’t” instead of “was not”. They will often use more humour or sarcasm than normal to make a joke of things, and will be VERY eager to change the subject.

If you want to trick them, change the subject randomly. If they seem more at ease, they’re probably lying. If they get confused, irritated or draw the conversation back to the original, they’re probably innocent.

Liars stories will change a lot over short periods of time.
Our short term memory is amazing, but not perfect. When liars make up a lot of false information in a short conversation, not all of it will be remembered in the long term. Ask them a couple of days later to recall their exact story; they will probably struggle to recall all of those small details that they so eagerly included before. You wouldn’t be nasty and put someone on the spot like that though… would you?

So does this actually work?

Well, I’d love to tell you that you’ll never be deceived again. I’d love to say that every person that stammers, forgets their stories and doesn’t look at you exactly 50% of your conversation length is, without-a-doubt, a liar.

Unfortunately, humans are just not simple enough. We don’t fit into neat, clean categories and all behave exactly the same. This is why some people are so excellent at lying. Their social skills are so advanced, they can just “keep their cool” all the time and don’t worry about lies. Telling if strangers are lying is virtually impossible, as you don’t know how they act in normal situations.

However, this is a useful guide to see if things are a bit suspicious. If someone you know well acts differently according to the guide above, the chances are they at least have something to hide. Unfortunately though, we will probably never be able to completely tell, with total accuracy, what is really going on in someone’s mind.

Thanks for reading,


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4 Comments Add your own

  • 1. steve  |  April 12, 2011 at 6:54 am

    I found better ways to tell if they’re lying

    • 2. Sam Eddy  |  April 12, 2011 at 2:02 pm

      Hello Steve,
      Thanks for your link. I would ask though, don’t you think that post is very low on elaboration and clarification?
      It seems the points are made without much attention to detail or any form of explanation.

      I appreciate your contribution though; thanks for reading.

    • 3. 胡健辉  |  November 16, 2011 at 9:14 am

      @Steve, I don’t think that the link you gave is better than this one, I think this one is more useful. By the way, thanks, Sam.

      • 4. Sam Eddy  |  November 16, 2011 at 10:44 am

        Hi there,

        Thanks very much for your support, that’s very kind!

        Enjoy the rest of your day,

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