Lie to me: the science of lie detection


By Steve Elliott our Science and Health correspondent

Most people will be familiar with the TV series Lie to Me. Tim Roth plays Cal Lightman, a scientist whose expertise is detecting and interpreting micro-expressions – involuntary facial expressions that last just a moment, flashing across the face before most people can get hold of them – a useful skill if you want to want to figure out whether someone’s lying or not.

The Cal Lightman character is based on clinical psychologist Dr. Paul Ekman who acts as a scientific advisor on Lie to Me.

Dr Ekman’s research indicates that our facial expressions reveal emotions which are innate, universal and nearly impossible to conceal.  From the U.S. to Japan, Africa and New Guinea, happiness, anger, surprise and despair trigger the same facial muscles: provided that the liar is not a psychopath who does not experience a typical human emotional response.

Dr Ekman: “The science that he [Lightman] does, and the applications, are exactly what I’ve been doing, particularly in the past five years, in applying this with law enforcement and national security.”

According to Dr Ekman, less than 1% of people are ‘naturals’ – able to detect those unintentional give away micro-expressions – but you can be trained and that’s where Ekman’s consultancy comes in.  Dr Ekman advises everyone from the Secret Service to Pixar on the science of reading facial expressions.

Dr Ekman – micro-expressions

Not all tell-tale signs of humans lying require one to be a specialist in recognising micro-expressions.  There are more obvious human reactions for those who are not ‘naturals’ – certain visible eye movements can easily be spotted in people telling lies.  Eyes unconsciously move to 6 different quadrants when people access certain memories relating to image, sound and feelings which they either genuinely remember or which they disingenuously create:

i) VISUALLY REMEMBERED: a real memory of an image where the eyes look upwards and to the left when someone is remembering something they actually saw (the truth). 
ii) VISUALLY CONSTRUCTED: an invented image where the eyes look upwards and to the right when creating an image not actually seen (a lie).
iii) AUDITORY MEMORY: a real memory of a sound where the eyes look to the left when someone remembers something they actually heard (the truth).
iv) AUDITORY CONSTRUCTED: an invented sound where the eyes look right when creating a sound not actually heard (a lie). 
v) KINAESTHETIC: an invented feeling where someone is imagining feelings they never actually felt (a lie).
vi) AUDITORY DIGITAL: a real sound memory of a number sequence remembering a number sequence they actually heard (the truth).

[N.B. all these movements will be in the opposite direction if the person is left-handed i.e. left is right and vice-versa]

The 6 quadrants

Micro and macro expressions aside, lie detection technology has moved on in leaps and bounds since the invention of the sweat detecting 20th century polygraph.  The traditional polygraph is limited as a bona fide lie detector in the 21st century – truth tellers can fail a polygraph test and good liars can pass one.  The polygraph picks up on the physiological sweat reaction when people lie but its underlying weakness is people telling the truth also sweat when they are stressed – false positives.

MRI brain scans, on the other hand, can look into people’s skulls and see the brain activity of people telling lies and of those telling the truth.  MRI scans reveal that areas in the prefrontal cortex ‘light up’ when people tell lies and when they are questioned specifically on those lies twice as many areas of the brain become active (including parts involved in memory) as people compare their present answers to their previous lies.  Put another way, the brain has to work harder to make sure that each part of the story corresponds to the original lie – you have to keep track of what you just said so that every single time you speak or answer a question you don’t get caught out on your lie.  That’s why interrogators ask questions requiring detailed answers – a detail such as a time, a place, a colour, a sound, a number etc. can open up large holes in an otherwise well prepared story.

Not everybody is willing to be tied onto an MRI scanner.  A more practical method of lie detection is the recent science of voice frequency stress detection.  When people lie, certain vocal frequencies that people won’t pick up on can be detected by a microphone, a laptop and some clever software using the next generation of lie detector – Layered Voice Analysis (LVA) i.e. a laptop lie detector. 

The CIA has been employing this kind of technology for years and now it’s perfected, readily available and coming to a future employer near you – certain employers already do telephone pre-interviews for job candidates using this technology.  The lie detector boasts of being able to detect a false statement with just two words spoken by a respondent.  The spoken language itself (English, Spanish etc.) is irrelevant, it’s the answers that demand an emotional response from the respondent which produce human voice stress frequencies.  Once the LVA lie detector picks up on a false statement the interviewer will then ask some probing questions relating to the suspected lie to verify that a lie has been told.   This LVA lie detector doesn’t require that suspected liars be hooked up to anything – only the vocal responses are required and it can work just as well with an audio recording as a face to face interview.

If you don’t have access to such technology (and a smartphone app is no doubt available), you can learn to watch out for tell-tale physical signs of someone telling a lie – a liar will appear ‘uncomfortable’.  The question really is, why is that person uncomfortable?

Tell-tale signs.
Look for a person:
a) touching their face excessively, or who fidgets or fusses for no reason may be hiding the truth (a random physical action that seems unnecessary).
b) having a demeanour or voice that radically changes (going from calm to agitated or lively to mellow — chances are he’s not telling the truth).
c) having an answer for everything (most people have to think about an answer, a liar already has it prepared).
d) proclaiming his honesty repeatedly (liars often use phrases emphasizing the validity of their statements, like “to tell the truth” and “to be perfectly honest”).
e) placing an object between you and them or crosses their arms (a form of protective wall).
f) performing too much eye contact or looks away a lot.
g) avoiding grammatical speech contractions, I did not instead of I didn’t.
h) lying, only smiles with their mouth and not their eyes.
i) providing more information than necessary.
j) displaying relief when you change the subject.

‘Would I lie to you honey?’

A 2010 survey of three thousand people commissioned by the Science Museum of London revealed men lie more than women.  On average men tell three lies every day or roughly 1,092 per year; women told two lies a day, or 728 lies a year.

The top lies?

I didn’t have that much to drink                                   
Nothing’s wrong, I’m fine
I had no signal (mobile phone)
It wasn’t that expensive
I’m on the way
I’m stuck in traffic
No, your bum doesn’t look big in that
Sorry, I missed your call
You’ve lost weight
It’s just what I’ve always wanted

Nothing’s wrong, I’m fine
I don’t know where it is, I haven’t touched it
It wasn’t that expensive
I didn’t have that much to drink
I’ve got a headache
It was in the sale
I’m on my way
Oh, I’ve had this ages
No, I didn’t throw it away
It’s just what I’ve always wanted

In the words of Fleetwood Mac, ‘Tell me lies, tell me sweet Little Lies’.