April 3, 2012 at 8:35 AM ET
We know our faces may give away our fibs -- whether it's shifty eyes, a sweaty upper lip, a slight smirk, or Pinocchio's fictitious lengthening nose.
Now a new study reveals that muscles in the upper face may divulge when people are not telling the truth. Researchers found four different facial muscles that a trained eye can use to separate genuine expressions of emotion from deceptive ones.
"Facial cues are an important, but often ignored, aspect of credibiity assessments where an emotional issue is in question," says study author Dr. Leanne ten Brinke.
"Cues to emotional deception are likely to occur when the underlying emotion a liar is attempting to mask is relatively strong," suggests ten Brinke of the Centre for the Advancement of Psychological Science and Law at the University of British Columbia - Okanagan.
For the study, published in the journal Evolution and Human Behavior, researchers watched the videotaped facial actions of 52 people who made televised pleas for the safe return of a missing relative. As it turns out, half of the pleas were from deceptive individuals who were later convicted of murdering their loved one.
Coders analyzed more than 23,000 frames of video from real-life cases in the US, Canada, Australia, and the UK. They compared the facial actions of 26 genuine pleaders to those of 26 liars.
By looking closely, researchers found some facial muscles "leak" signs of our true feelings during these intensely emotional and pressurized pleas to the public.
Genuine pleaders showed more contraction of two facial muscles related to grief and sadness: corrugator supercilii, one of the three muscles of the eyelid that helps wrinkle the forehead, and depressor anguli oris, a mouth muscle that is associated with frowning. In liars, they detected subtle contractions of the zygomatic major, a facial muscle linked with masking a smile, and full contraction of the frontalis muscle suggestive of a failed attempt to seem sad.
"What was surprising was just how strong these facial failures were able to predict which pleaders were the deceptive murderers compared to the genuinely distressed relatives," points out ten Brinke. She says muscles in the upper face "leak" signs of true emotion because they are under less of our conscious and voluntary control.
Can you use these facial muscles to tell when your teenager or a cheating spouse is lying to you? Some clues may be revealed by asking emotional questions and looking for seemingly out of place emotional expressions particularly in the upper face, suggests ten Brinke.
But it's not a silver bullet.
"Facial analysis does not provide us with a Pinocchio's nose," admits ten Brinke. "Not everyone will leak their true emotions, and some people are better than others at adopting a false face -- like psychopaths," she adds.