Kijun Times

A polygraph or "lie detector" measures a variety of physiological changes such as blood pressure, pulse, respiration, and skin conductivity while the subject of the test is asked a series of questions. The polygraph was invented in 1921 by a medical student at the University of California, Berkeley and a local police officer.

Polygraph tests remain an entertaining part of popular culture, but most psychologists would agree that it's basically impossible to tell if someone is telling the truth using a lie detector. For decades, the general consensus among psychologists has been that the best way to detect if someone is lying is to pay attention to body language and implicit, or unconscious cues.

However, two new studies have found that the most reliable way to detect a liar may, in fact, be to identify his or her ability to juggle explicit information using verbal working memory, and to identify if the person appears to be thinking too hard. As it turns out, overthinking is probably the single most reliable cue for detecting a liar.

Good Liars Have Better Verbal Working Memory

When was the last time you told a lie? Do you consider yourself to be a good liar or a bad liar? According to Elena Hoicka (link is external), PhD, a professor of psychology at the University of Sheffield, people tell some type of lie in approximately one-fifth of their social exchanges lasting 10 or more minutes.

In a recent study, Hoicka and colleagues at the University of Florida investigated the role that working memory plays in verbal deception and lie-telling in children. The June 2015 study, “Liar, Liar, Working Memory on Fire: Investigating the Role of Working Memory in Childhood Verbal Deception (link is external),” was published in the Journal of Experimental Child Psychology. For this experiment, the researchers presented 6- and 7-year-olds with a temptation resistance paradigm and discovered that good liars had higher verbal working memory (WM) scores compared to bad liars.

Working memory is the system responsible for holding and processing new and already-stored knowledge. Verbal working memory is important when telling a lie because the liar needs to juggle multiple pieces of information while remaining cognizant of the perspective and knowledge of the person being told the lie.  

The children in this study played a trivia game and were then given an opportunity to secretly peek at the final answers on the back of the card when left alone in the room... unbeknownst to them, their cheating was being captured on hidden camera. 

Children with lower verbal working memory answered the entrapment questions correctly, thus revealing that they had secretly peeked. Those with better verbal memory were more sly, and didn't fall into the trap. This is the first time a study has shown specifically that verbal working memory has particularly strong links to someone's ability to be a good liar.

Overthinking Can Give Away a Bad Liar

Source: Piotr Marcinski/Shutterstock

In another recent study on lying, investigative psychologists from the University of Huddersfield and University College London found that the most reliable way to identify if someone is telling a lie is based on whether or not he or she appears to be thinking too hard. These findings dovetail perfectly with Hoicka's findings about verbal working memory and lying. Clearly, people with superior verbal working memory are more adept at being "silver tongued" and won't appear to be overthinking when telling a lie.

Typically, participants in studies about lying aren’t told that the experiment is about deception. Instead, they are usually asked to judge whether the person speaking has awkward body language or appears to be anxious and tense. A common explanation of this type of lie detection is that we all have an implicit awareness or "gut instinct" of what appears to be guilty behavior. Even when you aren’t able to explicitly articulate an intuitive feeling or hunch that someone is lying, body language often conveys shadiness.

For their new experiment, the UK researchers instructed people to focus solely on whether or not someone seemed to be overthinking while recalling a story about travel experiences. The researchers discovered that if a person telling a lie appeared to be thinking too hard (indicating deception) that it offered the most reliable lie detection results. The October 2015 article, "The Focal Account: Indirect Lie Detection Need Not Access Unconscious, Implicit Knowledge (link is external)," was published in the Journal of Experimental Psychology: Applied.

For this study, Chris N.H. Street (link is external), PhD, and Daniel Richardson (link is external) devised a sneaky test of deception that involved hiring a film studio in London and persuading passers-by to be interviewed for a so-called "documentary" on tourism. People walking past the studio were asked to quickly describe genuine travel experiences and then to describe places they had never been as if they had actually visited these locations. Later, each person was interviewed by someone who they assumed did not know they had agreed to lie on film about places they had never been. In a press release, Street described the study,

"The idea was that they were lying to someone that they could potentially deceive. They were lying on behalf of another person, but the lie was spontaneous and told with an intention to mislead. People are asked to rate some behavior that is indirectly related to deception. For example, does the speaker appear to be thinking hard or not? The researcher then converts all thinking-hard judgments into lie judgments and all not-thinking-hard judgments into truth judgments.”

Street and his co-researcher Daniel Richardson concluded, "Indirect lie detection does not access implicit knowledge, but simply focuses the perceiver on more useful cues." These findings could have real-world significance, especially in the training of professional interrogators. 

Conclusion: Developing Failproof Lie Detection Requires More Research

Street and Richardson are quick to concede that developing 100% failproof human lie detection will require a great deal more research and is a long way from being infallable. 

According to Street, the British Psychological Society has completely dismissed the polygraph as a tool that will ever be useful for detecting lies. There is no way that the polygraph machines will ever be able to detect lies accurately. Polygraph tests can really only detect anxiety. This causes the polygraph to fail on two levels. First, many liars, especially sociopaths, are able to stay physiologically calm when telling a lie. Secondly, often the reason someone tells a lie is that to tell the truth can be more anxiety-provoking than telling a lie. 

The field of lie detection needs to develop more ways to identify the universal explicit and implicit clues of deception and dishonesty. Based on these new findings, it appears that people with superior verbal working memory and grace under pressure are likely to be the best liars. Although it isn't failproof, overthinking remains the single most reliable cue for identifiying if someone is being untruthful. 

If you'd like to read more on this topic, check out my Psychology Today blog posts,

• "Gut Feelings Can Predict Marital Bliss"
• "How Does the Vagus Nerve Convey Gut Instincts to the Brain?"
• "The Neuroscience of Grace Under Pressure"
• "12 Ways that Eye Movements Give Away Your Secrets"
• "Neuroscientists Decrypt the Mystery of Rapid Eye Movements"
• "New Clues on the Inner Workings of the Unconscious Mind"
• "Why Does Overthinking Sabotage the Creative Process?"
• "The Neuroscience of Knowing Without Knowing"
• "Why Does Overthinking Cause Athletes to Choke?"
• "Superfluidity: Decoding the Enigma of Cognitive Flexibility"
• "Want to Improve Your Working Memory? Go Climb a Tree!"