How to spot a liar

By Thomas Davis

Professor Thomas Davis In anticipation of the new degree in criminal psychology at Nichols College, Professor Thomas Davis, PhD, examines the more extreme methods of lie detection throughout ages, its modern predecessors, and some tell-tale signs of lying. He is the author of Forensic Psychology: Fact and Fiction (2021).

Los Angeles County Superior Court Judge Patrick Couwenberg had impeccable qualifications and impressive achievements. His education included an undergraduate degree in physics, a master’s degree in psychology, and a law degree from Loyola University. He earned a Purple Heart in the Vietnam War and secretly served as a CIA operative in Laos in the 1960s. Before serving as a judge, he worked for one of the most prestigious law firms in Los Angeles, Gibson Dunn & Crutcher.

As impressive as his achievements were, none of them were real. When confronted, Judge Couwenberg blamed a condition called pseudologia fantastica, a compulsion to tell stories containing facts interwoven with fantasy often called pathological lying. His excuse did not save him from being removed from the bench. His story raises the question, how can we be so effective at deception, yet so easily deceived?

Honesty is among the top five characteristics people want in a leader, friend, or lover. From social media to online dating, identifying and coping with lying is a common topic of most conversations. Yet, although we are skilled at producing lies, we are terrible at detecting them because we’re looking for the wrong signs.

Before you read further, ask yourself, “How do I know when someone is lying?”

Check to see if your answer matches the Global Deception Research Team’s survey findings. They asked this same question and found the most common belief about deception is that liars avoid eye contact. Also mentioned was the idea that liars are nervous, and this causes excessive movements of the liar’s body. As obvious indicators of deception, these signals of lying could be useful. However, neither of these common beliefs have research support for detecting deception.

Ancient methods: From burned tongues to beating hearts

For as long as there have been lies, there have been methods of lie detection. Over time, our talents for practicing deception have outpaced our detection ability. The origins of our current approaches for lie detection began as early as 300 B.C. with the notion that lying produces physical side effects. Past methods of detection used rituals that invoked supernatural aid through sacred signs and totems. However, these techniques relied more on the belief in their effectiveness to condemn the deceitful rather than their ability to separate liars from truth tellers.

The Bedouins of Arabia required the tellers of conflicting statements to lick a hot iron. The teller whose tongue was not burned was considered truthful. In China, around 1000 B.C., subjects put dry rice powder in their mouths and then spit it out. If the powder was dry, the individual was lying. The reasoning behind these methods was that the anxious and nervous person (the one lying) has less saliva (a dry mouth and tongue). Today we know that this reaction is the fight-or-flight response, where experiencing fear and anxiety causes decreased salivation and a dry mouth.

Ancient Sparta used ruthless methods of detecting the truth. To qualify for admittance to certain schools, Spartan men were required to pass the selection criteria. The young men were ordered to stand on the edge of a cliff and were asked if they were afraid. The required answer was always “no,” but the men’s complexion determined their truthfulness. It was assumed that the men with the pale complexions lied, and they were pushed off the cliff. In Ancient Rome, bodyguard screening was conducted using a similar method where candidates were asked provocative questions. Those who blushed were selected for the job. It was believed that if a person blushed in response to provocative questions, they wouldn’t take part in plots against authority.

Another method exploited the power of superstitious beliefs. Suspected thieves were led into dark tents with donkeys whose tails were coated in black lamp soot. The suspects were told that the donkeys would bray if touched by thieves, and that the suspects should now pull the animals’ tails.

Those who left the tent with clean hands (indicating that they had not dared to touch the animals for fear of being found out as thieves by the donkeys’ braying) were considered guilty.

During the middle ages, a suspect’s pulse rate was used to expose unfaithful wives and their lovers. The testing technique was quite simple. A trained individual placed a finger on a wrist of a woman suspected of infidelity, while mentioning names of men, who could have had an intimate relationship with her. When the examinee’s pulse accelerated, it was obvious that she was reacting to the name of her lover. The modern-day version of these techniques is the notorious polygraph which relies more on the belief in its effectiveness than its actual ability to detect lies. It’s sometimes described as a “lie detector,” “fear detector” or even as an “emotion detector.” In fact, no reliable signs of deception have ever been identified. Even worse, there is no evidence whatsoever that what the polygraph actually measures — heart rate, blood pressure, sweating, and breathing — are linked to whether or not you are telling the truth.

Evidence over behavior

We have all been on the receiving end of a lie. Try to remember a lie that you detected in the past. Recall as much as you can about the situation in which the person lied to you. Describe the event where you were lied to: Where did it happen? What was the lie about? Can you remember what the person said to you? Now think about how you found out you were lied to. What evidence revealed the lie? Finally, how much time passed between the time when the lie was told and when you knew that the person had lied?

Consider your evidence again; was it based on behavior or information? If your experience matches forensic research, you probably used evidence like third-party information (i.e., a friend told you about the lie), physical evidence (i.e., a text message or photo), or the liar’s confession. Unlike what’s shown in the entertainment media, discovering the lie takes time. On average 4.1 percent of lies are detected in less than an hour, 20.6 percent in less than a day, 20.6 percent in less than a week, 20.6 percent in less than a month, 15.5 percent in less than a year, and 1.5 percent more than a year after they were told! Do these results match your experience? If so, you now understand the advantages of using evidence over behaviors to detect deception.

Revealing language

Unlike telling the truth, telling false stories requires more imagination to describe events that didn’t happen in a style that appears sincere. As a result, stories based on imagined experiences are different from stories based on real experiences. One way to capture the differences between true and false stories is to examine the language people use to tell them. The specific word choices and grammar often reveal more than the surface content of their story. Take for example, the case of Susan Smith appearing on television claiming that her two young children were kidnapped at gunpoint. She tearfully pleaded for her children to be returned, telling reporters, “My children wanted me. They needed me. And now I can’t help them.” Her choice of past tense was strange because, normally, relatives will speak of a missing person in the present tense. The fact that Smith used the past tense in this context suggested that she already viewed her missing children as dead.

But it was a small yet significant contradiction in her story that led to her confession. Smith told police about stopping at a red light on Monarch Mills Road. She said that she saw no other cars on the road. Yet the light turned red, contradicting the fact that the light on Monarch Mills Road was always green and only turned red if it was triggered by a car on the cross street. Since she said there were no other cars on the road, there was no reason for her to come up to a red light. This subtle verbal contradiction eventually led to Smith confessing that she drowned her children by pushing her car into the lake with them buckled securely in the back seat.

So, the best way to spot a liar? Look less and listen more.

Forensic Psychology: Fact and Fiction is a research-led textbook written by Thomas Davis Ph.D. professor of psychology at Nichols College, that offers students the tools they need to engage critically with the psychological dimension of the criminal justice system. It is published by Red Globe Press, an imprint of MacMillan International Higher Education.