How to Detect Lies Like a Pro

If you’re planning a career in the criminal justice sector, or security, or personnel selection, you’ll find it useful to polish up your skills of lie detecting.

The ancient Chinese knew a thing or two about lie detection. People suspected of lying would be required to chew dry rice under questioning. If grains of rice stuck to their tongue after they spat out the rice, they were deemed to be not innocent. What the ancient Chinese had observed was that stress influences the autonomic nervous system which controls the salivation process, leading to a dry mouth in the guilty party (source, Ancient Origins).

You’ll be pleased to learn that things have moved on since then. Although polygraph machines are generally accepted as being poor detectors of lies, there are other, research-backed ways of getting to the truth. Some of these are described below.


Cognitive load

The key to finding out whether someone is lying can be found in a concept known as ‘cognitive load’.  This refers to the mental effort that someone has to exert to lie. (Lying well, according to experts, is hard work. A deceiver not only has to work hard to keep his or her facts straight, they also have to concoct a credible story and withstand the most intense scrutiny, for example.) The ‘cognitive load’ approach to lie detection has two strands to it: the first is the observation part, which determines that the act of lying generates visible signs of cognitive load, and the second is the detection aspect, which suggests that by introducing “mentally taxing” interventions, you can “impose” cognitive load (source: A cognitive approach to lie detection, Vrij et al; via Wiley Online Library).


Indicators of deception


  • Liars tend to look at you in the eye – ie, their gaze is fixed. This, it seems, reduces the likelihood that they will be distracted and helps them to focus on fabricating their story.  Studies have shown that, contrary to popular belief, honest people have more eye movements than liars.
  •  Liars will engage in comfort-inducing gestures when faced with tricky questions - they may put their hands over their mouth, touch their face or play with their hair.
  •  Liars are uncomfortable when asked to provide specifics.  They often use ‘text-bridges’ to avoid specifics, words such as “later on” or “afterwards”.
  •  Liars will employ delaying tactics, such as repeating a question or asking their own questions.
  •  Liars usually take longer to answer questions than truth-tellers.
  •  Liars are uncomfortable with silences and will talk to fill pauses if they feel their version of the truth has not been accepted.
  •  People who are not telling the truth tend to avoid first person (eg, ‘I’) statements, as if to separate themselves from their lie. They also lean towards using third person pronouns and abstract communication.
  •  Studies have found that liars generally don’t use contractions, for example, instead of ‘I wasn’t at the party”, they would opt for “I was not there” – as if to emphasise their innocence.
  •  Liars will overcompensate to hide their deception by using more words than honest people. This is called “The Pinocchio Effect” (source, Working Knowledge)



Techniques used to impose a ‘cognitive load’ and determine the truth

To impose a cognitive load on suspects, techniques may include any of the following:

  •  Asking a suspect to tell their story in reverse
  •  Asking open questions (questions that do not result in a ‘yes’ or a ‘no’ answer) in order to elicit as much information as possible

If you are interested in pursuing a career where you will be required to ascertain the truth from a person, you may well be offered formal training in lie detection. And you may well find that although the indicators described above may give valuable insights, no behavioural cue or indicator is a guarantee that a suspect is lying – only corroborated facts will do that.


Main image source

Information sources/Further reading


CV Writing Services
CV Writing Services

Detecting deception

(Social Science Space).

Science Daily

Working Knowledge





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