(Agencies)
Updated: 2008-04-28 15:48

Liars might think they are good at covering up their deceit but a new Canadian study shows there's one thing they can't control that will give them away - flashes of emotion in their faces.

Researchers at Dalhousie University's Forensic Psychology Lab in Halifax conducted the first detailed study on the secrets revealed when people put on a false face or inhibit various emotions, and found their faces told the truth.

But instead of clues like shifty eyes or sweaty brows, their expression would crack briefly, allowing displays of true emotions such as happiness, sadness, disgust and fear to come through.

"Unlike body language, you can't monitor or completely control what's going on your face," Stephen Porter, who worked on the research, said in a statement.

The researchers, who reported their findings in journal Psychological Science, examined the case of Canadian Michael White who sobbed as he made a public appeal for the return of his missing pregnant wife Liana White in July 2005.

But three days later, flashes of anger broke through his sadness and he said he was so frustrated with the police that he was going to find his wife himself, leading volunteer searchers directly to her body in a ditch on the outskirts of Edmonton.

He was charged and convicted of second-degree murder.

When Porter and his team analyzed White's plea frame by frame, they found hints of anger and disgust in his face, not noticed by most of the public.

The researchers also studied adult who were asked to view images that ranged from happy (puppies playing) to fearful (a close-up of open-mouthed rabid dog) and disgusting (a severed hand).

They were told to respond with genuine or deceptive expressions and their reactions recorded.

Porter said no one was able to falsify emotions perfectly. Some emotions were harder to fake than others. Happiness was easier to fake than disgust or fear.