Jan 19, 2022

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Until now, the best – but far from being foolproof – method for finding out whether a person is lying is with a polygraph – popularly referred to as a lie detector test – a device that measures and records several physiological indicators such as blood pressurepulserespiration and skin conductivity while a person is asked and answers a series of questions.  


Even though the polygraph test relies on objective physiological responses, the collection and interpretation of its data are highly subjective – the questions are not similar across all tests, and different investigators use different values to indicate a lie. In addition, some people are skillful at lying without being detected.


Dynamic facial expressions are a central component of emotional expression upon which we rely to convey our feelings and intentions and infer those of others. It was the 19th century English naturalist, geologist and biologist best known for his contributions to the science of evolution, Charles Darwin, who first noted that some emotions are too great to be fully feigned or concealed, and that some facial expressions might “leak,” revealing true feelings.


Now, researchers at Tel Aviv University (TAU) have found a better way. They caught “liars” with the unprecedented accuracy of 73% by measuring the movements of facial muscles – a higher rate of detection than any known method.


The new technology, they said, could serve as a basis for the development of cameras and software able to detect deception in many real-life scenarios such as security and crime. The researchers identified two different groups of ‘liars’ – those who activate their cheek muscles when they lie, and those who activate their eyebrows. 


The study was conducted by a TAU team headed by Prof. Yael Hanein of the Center of Nanoscience and Nanotechnology and School of Electrical Engineering in the Fleischman Faculty of Engineering, and Prof. Dino Levy from the Coller School of Management. The team included Dr. Anastasia Shuster, Dr. Lilach Inzelberg, Dr. Uri Ossmy and doctoral candidate Liz Izakon. The paper was published in the leading journal Brain and Behavior under the title “Lie to my face: An electromyography approach to the study of deceptive behavior.” 


The new study was founded upon a groundbreaking innovation from Hanein’s laboratory – stickers printed on soft surfaces containing electrodes that monitor and measure the activity of muscles and nerves. The technology, already commercialized by X-trodes Ltd., has many applications, such as monitoring sleep at home and early diagnosis of neurological diseases. This time the researchers chose to explore its effectiveness in a different arena – lie detection.


“Many studies have shown that it’s almost impossible for us to tell when someone is lying to us,” noted Levy.” Even experts such as police interrogators do only a little better than the rest of us. Existing lie detectors are so unreliable that their results are not admissible as evidence in courts of law because just about anyone can learn how to control their pulse and deceive the machine. Consequently, there is a great need for a more accurate deception-identifying technology. Our study is based on the assumption that facial muscles contort when we lie, and that so far no electrodes have been sensitive enough to measure these contortions.”


The researchers attached the novel stickers with their special electrodes to two groups of facial muscles – the cheek muscles close to the lips and the muscles over the eyebrows. Participants were asked to sit in pairs facing one another, with one wearing headphones through which the words “line’ or “tree” were transmitted. 


When the wearer heard “line” but said “tree” or vice versa, he was obviously lying, and his partner’s task was to try and detect the lie. Then the two subjects switched roles. 

As expected, participants were unable to detect their partners’ lies with any statistical significance. However, the electrical signals delivered by the electrodes attached to their face identified the lies at an unprecedented success rate of 73%.


“Since this was an initial study, the lie itself was very simple. Usually when we lie in real life, we tell a longer tale which includes both deceptive and truthful components,” Levy explained. “In our study, we had the advantage of knowing what the participants heard through the headsets and therefore also knowing when they were lying. Using advanced machine learning techniques, we trained our program to identify lies based on EMG (electromyography) signals coming from the electrodes. Applying this method, we achieved an accuracy of 73% —

 not perfect, but much better than any existing technology. Another interesting discovery was that people lie through different facial muscles; some lie with their cheek muscles and others with their eyebrows.”


The researchers believe that their results can have dramatic implications in many spheres of our lives. In the future, the electrodes could become redundant, with video software trained to identify lies based on the actual movements of facial muscles. “In the bank, in police interrogations, at the airport or in online job interviews,” predicted Levy, “high-resolution cameras trained to identify movements of facial muscles will be able to tell truthful statements from lies. Right now, our team’s task is to complete the experimental stage, train our algorithms and do away with the electrodes. Once the technology has been perfected, we expect it to have numerous, highly diverse applications.”


Some libertarians may oppose the use of cameras to detect when people are dishonest on the premise that “people are entitled to lie,” and some politicians may not like the idea. But since deception is present in all walks of life, from social interactions to matters of homeland security, knowing who is truthful and who is lying could be a matter of life and death.