A forensic psychology lab in Canada has conducted research on how liars can be detected by observing changes in their facial expression.

Lying, of course, is something everyone does on a daily basis, often to ease social tension. But in the world of business, politics and especially law enforcement, deception plays a much higher stakes game.

Police and other law enforcement workers commonly rely on non-standardized interviewing techniques to detect deception in their suspects, but such methods are seen as more of an art than a science. Recently, a research team led by Dr. Porter from Dalhousie University have analyzed thousands of frames of video footage to systematically nail down the tell tail signs of a liar.

Enlisting a group of adult participants, the research team decided to test if the four universal emotions – fear, happiness, sadness and disgust – could be faked. For instance, if the participants were shown a photo of puppies playing, they might be asked to act fearful instead of happy.

After almost 700 video clips were analyzed frame-by-frame, the researchers concluded that not one participant could falsify emotions perfectly. When asked to be deceptive, participants exhibited a higher rate of non-corresponding expressions, with fear and disgust being hardest to fake.

Microexpressions, or true expressions that would only appear for a fraction of a second when participants were lying, allowed researchers to guess if participants were being dishonest. The researchers describe this phenomenon as a true expression ‘cracking’ a deceptive one; however, such flashes of honesty were often contained to just the upper or lower portions of the face making detection difficult. The researchers concluded that a series of tests, such as a scripted flow of questions during a police interview, would be needed to accurately detect lying in suspects.

The mechanism behind microexpressions lies in the complexity of the human face and the motor neurons that control its muscular expressions. Unlike muscles in the limbs and torso, facial muscles are not always under conscious control when we want them to be, thus making it impossible to fake an expression 100% of the time.

The researchers of this study are now pouring over highly publicized cases of lying to observe microexpressions in real life situations. Such research could help fine tune detection methods used by law enforcement and forensic science professionals.