Can you really tell if someone is lying? Here's what the experts say.

As a betrayal of lying, Pinocchio’s elongating nose could not have been more obvious. At one point in the original novel by Carlo Collodi, it grows so long that the puppet boy is unable to turn around inside the room of a house. 

It’s the ultimate giveaway—but, of course, entirely unrelated to reality. But while real-life physical betrayals of lying are rarely this dramatic, they’re not unknown. 

Back in 1993 there was a medical case of a 51-year-old man who, when he told lies, suffered far more debilitating effects than Pinocchio ever did. In a letter published in the Journal of Neurology, Neurosurgery, and Psychiatry, medics from the university hospitals of Strasbourg, in France described an unfortunate patient who regularly lost consciousness and suffered convulsions. “More than a third of the attacks occurred while the patient was lying,” the medics added.

On examination, it turned out the unfortunate fellow had a 30mm tumor in his brain. His doctors suggested the emotions he felt while telling lies were agitating the limbic lobe in his brain and, in turn, triggering a rare form of epilepsy.

A history of deception

The average human tells up to two lies a day, according to a 1990s study in the Journal of Personality and Social Psychology. There’s even evidence that primates can use tactical deception. 

Most of our lies are white lies or fairly harmless fibs. However, in fields such as law enforcement, espionage and insurance, distinguishing truth from falsehood is a vital requirement; sometimes even a matter of life and death. 

But how to tell the difference? For much of human existence, identifying lies relied on religious, superstitious—and sometimes barbaric—rituals: trial by combat, trial by ordeal, or trial by torture. 

In ancient China, suspects were forced to chew a handful of raw rice and, if afterwards, they spat it out dry, they were deemed guilty—probably a ritual based on the idea that fear dries up the saliva in one’s mouth. In ancient India, suspects were required to stand in a dark tent and pull on the sooty tail of a sacred ass which, they were told, would bray out loud for the guilty. On exiting the tent, those with clean hands were considered criminals since guilt had prevented them from having the confidence to pull the tail.   

By the late 19th Century, methods were fortunately becoming more scientific, first analyzing changes in people’s blood pressure, and later in their breathing patterns. By the 1930s, American inventor Leonarde Keeler had added galvanic skin response as a third metric, in order to measure perspiration levels. The resulting machine became famous as a ‘soft’ interrogation’ device—and even today, the modern polygraph still uses those three factors to determine untruths.

But the machines are by no means infallible. According to the American Psychological Association, “most psychologists agree that there is little evidence that polygraph tests can accurately detect lies.” The vast majority of jurisdictions around the world reject polygraph results as inadmissible in courts of law.

Non-verbal signs

Are there perhaps physical and facial gestures that liars typically make, however? Joe Navarro is a former interrogator with the FBI, who worked in counter-intelligence and counter-terrorism. He even once coached poker players in spotting and masking body language. If anyone can spot signs of a liar, it ought to be him.

“There is no Pinocchio effect,” he tells National Geographic (U.K.) with total conviction. “People have long thought and taught erroneously that if somebody touches their mouth, for example, or covers their nose, or looks in a certain direction with their eyes, that these are behaviors indicative of deception. But there is ample research to show that there is no single behavior indicative of deception.”

These gestures suggest emotion, however. “We need to stop associating behaviors indicative of psychological discomfort with deception, and acknowledge them purely for what they are: signs of stress, anxiety, apprehension, despair, suspicion, tension, concern, nervousness, etc. But not deception.”

During his 25 years working for the FBI, Navarro says he conducted more than 10,000 interviews with various witnesses and suspects. He points out how both the innocent and the guilty can display signs of psychological discomfort and what is known as “pacifying behavior”: hands shaking, perspiration, blushing, shifting eye movements, touching one’s face, biting one’s lips, blinking profusely, or speaking with an uneven voice, for example.

“It’s often really nothing more than our bodies reflecting how we feel about the situation we’re in,” he adds. Indeed, under police questioning, even the most innocent tend to become nervous.

Navarro remembers one occasion when he was questioning a woman suspected of white-collar crime. He was trying his utmost to keep her calm but, before he had even started discussing the crime, she was biting her lip, flicking up the back of her hair, and touching the area of her throat, just below her trachea—known as the suprasternal notch. This latter gesture, Navarro says, is a form of nervous self-protection that dates back to prehistoric times when early humans would protect their jugular from attack by predators.

Given the women’s physical reactions, Navarro was convinced of her guilt. In reality, she was very nervous, but not guilty. She had simply parked her car nearby and was aware the parking meter was soon to run out. “She had nothing to do with the crime,” Navarro concludes.

Verbal signs

Is it perhaps better to analyse suspects’ words rather than their gestures? Dr. Abbie Maroño is a British university lecturer in psychology with a PHD in behavioral analysis. She also works as director of education at security consultants Social-Engineer, LLC. She says there are certain verbal clues we can look for when trying to identify a liar.

Factual inconsistencies are a key indicator. Police detectives often require their suspects to repeat recollections or alibis multiple times in an attempt to pick out discrepancies in the story.

Maroño says liars also tend to use what she calls “self-handicapping techniques”. “They use phrases such as ‘I can’t remember’ or ‘It was a while ago and I think I’ve forgotten’,” she explains. “This is more likely to occur with people who are lying.” She points out how certain politicians are masterful at this form of deceit.

Truthful people often supply more details under questioning. “People who are lying tend to simplify their stories, giving you stereotypical information which is easily accessible to them,” Maroño says. “Because if they have to recall [that information] later, they can easily get caught out. Whereas truth-tellers are more likely to report complicated details.”

Then there are unconscious trip-ups. During his time at the FBI, Navarro interrogated plenty of murder suspects. He recalls one incident where a mother alleged that someone had kidnapped her baby. Navarro was asked to interview her on behalf of the Sheriff’s office, and noted that she referred several times to her infant son in the past tense. “Sure enough: she had killed the baby herself,” Navarro recalls.

But even verbal slips are not sure-fire indicators of mendacity. Aldert Vrij is a psychology professor at the U.K.'s University of Portsmouth. In his book, Detecting Lies and Deceit: Pitfalls and Opportunities, he stresses that experienced interrogators often fail to recognise untruthfulness.

“Research has indicated that even professional lie catchers, such as customs officers and police officers, often make incorrect decisions, and that their ability to separate truths from lies typically does not exceed that of laypersons,” he writes. “One [reason] why even motivated people fail to catch liars is because lie detection is difficult. Perhaps the main difficulty is that not a single non-verbal, verbal or physiological response is uniquely associated with deception. In other words, the equivalent of Pinocchio’s growing nose does not exist.” Vrij goes on to explain there is no single response that can be relied upon by any person or machine looking for lies. He writes: “Another difficulty is that liars who are motivated to avoid being caught may attempt to exhibit non-verbal, verbal or physiological responses that they believe make an honest impression on lie detectors. Liars who employ such so-called countermeasures can indeed often fool professional lie detectors.”

All of which cannot be any comfort to that 51-year-old tumor patient from Strasbourg, who used to convulse and pass out when he lied. Fortunately, his doctors eventually prescribed an anti-convulsive medication called Carbamazepine, which did the trick.

No such cure for poor Pinocchio.