Detect, Confirm, Reveal: Confessions of a Human Lie Detector

human lie detector

Polygraph machines and their recent software-based incarnations measure pulse, perspiration, vocal frequency and pupil dilation in order to reveal whether someone is telling the truth or not. In short, when we lie we get a little flustered. By remembering the “base rate” benchmark of the individual, the software estimates whether the subject experiences stress during a particular line of questioning. They are fallible purely because they are designed to detect subtle signs of stress – not the deception itself. They only detect physiological arousal. Despite the day time chat shows’ preoccupation with them, they are largely useless for the purpose of criminal investigation.

[showmyads]Everybody has ‘tells’. The more sensitive you are to your own, and the more skilled you are sensing others’; the better you will be at poker. Understanding how tells work; despite being a cool thing to be able to do, is an invaluable life skill and has afforded me real success that I would not otherwise have enjoyed. Lie detection is not as simple as looking for a specific set of behaviours. Shiftiness, avoiding eye contact or touching of the mouth are examples of what was traditionally thought of as ‘tells’. (The latter is a passive NLP manifestation of literally concealing the truth.)  These tells are so easily controlled if the deceiver is aware enough or actively concealing the lie.

In other words, you don’t have to be spectacularly good at lying to act away a simple tell. Moreover, some people are shifty characters at the best of times and touching of a lip when thinking is also common body language to signal deep thought or confusion.

This approach runs into many false negatives because there are no universal signs of deception (Bond, Omar, Mahmoud, & Bonser, 1990). A false negative is a term used to refer to when one has determined the subject is lying, when they are telling the truth. A false positive is when a lie goes undetected.)

 Some maintain that there are certain verbal clues which might give the game away. Some basic examples of verbal tells are the copying of words:

“Did you speak to Steve in accounting?”

“No. I did not speak to Steve in accounting.”

Here’s the most famous example of the use of un-contracted words:

Instead of replying simply:  “No, I didn’t.” Bill stated almost for the record,” I did not have sexual relations with that woman.” While this is interesting, a Human Lie Detector largely ignores this when isolation and only be gives meaning to them when accompanied by several other signs of deception.

  Be sensitive to anything out of the ordinary

A real tell is a change in behaviour and not the behaviour itself. Human lie detection works in the same way as a polygraph.  It is a comparison between a “base” behaviour and something that is not a “base” behaviour (Navarro & Karlins, 2008). If someone is normally very cool and collected but starts shifting around in their chair upon questioning, then there is a good chance something is amiss. If someone always makes good eye contact with you only to break away suddenly when the topic of conversation changes, then equally one has good reason to be suspicious.

 Tip: Most good liars are able to control their body language very well, but watch their feet. Feet have so many evolutionary connotations. They are out of sight and so unnoticed despite being so communicative.

 Detecting Leakage

After much study into lie detection, the most reliable approach is to identify a disharmony between verbal and nonverbal language. This is termed leakage. It is almost always going to be that which sparked your suspicion. Now is the time to analyze.

This leakage may be flashes of emotions such as distress, contempt or disgust. (You’re still watching their feet, right? Good work.) Leakages are momentary, and in order to qualify as such they must contradict what the subject is saying (Frank, 2009).

Several discrepancies sum to a big fat lie.

For example your best friend’s eyes or mouth might ever so briefly tense up when saying: “I really had a good time yesterday and your new girlfriend is great.” A Human Lie Detector is sensitive to these micro expressions which are the tell-tale signs of deception and so relied upon heavily by experienced criminal interrogators.

Keeping Cool

Joe Navarro, the seasoned FBI man, worked in an interrogation room. Fortunately, you do not and so your subject does not realize he or she is now subject to interrogation and it’s best kept that way for a little while longer. Keeping your subject blissfully unaware is the easiest way to confirm potential deception.

So to reach your ‘true positive’, you can’t let on. (This would be your tell.) This is extremely difficult to do, as your subject is fully aware deception is in the air and heightened to any sign that you noticed. For the Human Lie Detector, noticing changes in base rate behaviour is a natural skill. Remaining perfectly cool and detached in light of deception, especially when malicious and emotionally charged, is a very unnatural skill and must be learnt and practiced.

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Although bitterly unnatural, this is so critical because the goal of the Human Lie Detector is not only to confirm deception, but to reveal it – bring it into the light – so action can be taken openly and honestly.

So be observant of your own emotions at this time. If the lie is personal or sensitive not even the best lie detector can explore any further, for fear of scaring off the subject and arriving at a false negative. Knowing the boundaries of their talents, if cool and fit to continue, a Human Lie Detector places the subject in an uncomfortable situation and continues to observe unnoticed.

Subtle testing and observation

If someone is lying, their main priority is to end the conversation or change the subject as quickly as possible. The key concept here is the avoidance of the topic in whatever format. The Human Lie Detector knows to allow for this to happen, changing the topic as often as possible, to provide more opportunity for study. The Human Lie Detector will find a distraction nearby and take the spotlight off the subject.  Being “let off the hook” is just as telling; the deceiver will launch at this opportunity returning once again to base rate behaviour. An innocent person may be confused and may want to finish the line of conversation, perhaps asking for your opinion on the matter. Moving naturally back and forth between the topics will usually undo even the most detached of poker players. If not, it is then time for testing: The key is to keep it very simple.

For example, your colleague at work may have manipulated the figures. Perhaps Jake concealed that he had failed to pay due attention to your project or ignored your budget request.

When Jake says: “I’ve already spoken to Steve – we both checked and we can’t find the file you’re looking for. The form was not filled in!”

A normal reaction would be: “That can’t be true – it must be there. I’m calling Steve.” It’s a poor reaction because it places Jake into defensive and heightened state of awareness, which could introduce more elements into play, complicate the original lie and its likely Jake will get away with it.

You are far likely to put a liar into a guilty frame of mind with:

“Really? Okay, that’s a pity. Speaking of Steve, I really need to go talk to him about another idea I had for next week’s meeting.”

In short, when someone is lying and now aware that you may be fast on the trail of said deception, the usual reaction is to end the conversation abruptly/awkwardly (flight) or overcompensate for the lie, by trying very hard to act naturally, and perhaps offering unnecessary detailed answers than would be normally shared (fight).

The Human Lie Detector

Being a Human Lie Detector takes practice. It is a study of the subtleties of verbal and nonverbal behaviour in relative terms and within context. It is extremely counterproductive to attempt to turn oneself into a Human Lie Detector overnight. It means the conscious mind is in a never ending search for inconsistent behaviours.

  • It is exhausting work to be on heightened alert all day long
  • It will influence your own natural behaviour and the whole thing will just backfire
  • It will make you paranoid
  • People will feel uncomfortable around you and not know why

The polygraph is not sophisticated enough for the job; however the primed unconscious human brain is… Once rehearsed, the Human Lie Detector need not distinguish leakages on a conscious level.

Skilling yourself in lie detection is something which you’ll need to start out slowly with. Your aim is for this new skill to be a natural part of you. Priming yourself to pay attention to changes in base behaviour is best practiced first on those who you know best. You may already be spectacularly proficient at knowing when your partner, child or best friend is lying to you. Be observant of them but more importantly be observant of yourself. Reflect: How do you know?

It’s a bit difficult to explain well, but the best way to describe your natural and unconscious lie detection skills is to pretend your perception is like tentacles of an octopus. They reach out, constantly testing your environment and the people around you. They do not sleep; they are automatic. When one of your tentacles touches on something odd, it triggers what you may think of as “a gut feeling.” To a Human Lie Detector, this innate alarm bell is nurtured, amplified and always listened to.


Ryan writes about the changing world of Psychology. He is also the owner of Subliminal Today, a company which provides subliminal mp3s to inspire uplift and develop human potential. You can find out more by visiting the site or following @subliminaltoday or joining in the discussion on


Bond, C.F., Omar, A., Mahmoud, A &., Bonser, R. N. (1990). Lie Detection Across Cultures. Journal of Nonverbal Behavior 14,189-204.

Frank, M (2009). Deception: Methods, Motives, Context, and Consequences. Stanford University Press: California.

Navarro, J. & Karlins, M (2008). What Every Body Is Saying: An Ex-FBI Agent’s Guide to Speed-Reading People. Harper Collins.

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