Facial muscles can now reveal liars, says study

Quite often we hear people say, "Seeing your face I know you are lying." That was pure instinct. But now, researchers at Tel Aviv University have studied facial muscles to catch out lies.

Researchers were able to detect 73 per cent of the lies told by trial participants based on the contraction of their facial muscles. This is a higher rate of detection than what has been achieved by any known method.

The study identified two different groups of 'liars': those who activate their cheek muscles when they lie, and those who activate their eyebrows. According to the researchers, the technology has great potential in detecting deception in real-life contexts, such as crime detection and containment of threats to security.

The study was conducted by a team of experts from Tel Aviv University led by Prof. Yael Hanein of the Centre of Nanoscience and Nanotechnology, School of Electrical Engineering, and the Aladar Fleischman Faculty of Engineering, and Prof. Dino Levy from the Coller School of Management.

Prof. Levy explains: "Many studies have shown that it's almost impossible for us to tell when someone is lying to us. 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.

The study was conducted by a team of experts from Tel Aviv University led by Prof. Yael Hanein of the Centre of Nanoscience and Nanotechnology, School of Electrical Engineering

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 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%.

Said Prof. Levy: "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 bank, in police interrogations, at the airport, or in online job interviews, 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," said Prof Levy.

The new study was founded upon an innovation from Prof. 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.