Scientists in Haifa, Israel suggest that a fool-proof method to spot a liar would be checking their handwriting.
According to psychologists, handwriting changes when someone lies, and this is so because the brain has to work harder to invent facts, which then in turn interfere with the normal writing process.
To reach the conclusion, researchers at the University of Haifa, Israel, asked 34 volunteers to write two short paragraphs, where in one they recalled a real memory while in the other a fictitious event, reports The Telegraph.
The volunteers used a wireless electronic pen with a tip that was pressure-sensitive in order to write their memories and lies.
Later the paper was placed on a computer tablet, which monitored and analysed their writing style.
The scientists then found those who wrote lies pressed harder on the paper, had longer pen strokes and produced taller letters than those telling the truth.
"In the false writing condition, the average pressure, stroke length and height were significantly higher than in the true writing condition," the researchers said.
Professor Richard Wiseman, psychologist at the University of Hertfordshire, told the Daily Mail the technique was promising.
"We know that people hesitate more when they lie and some companies already use this fact to see how long it takes people to tick boxes when filling in surveys online," he said.
The study has been published in the Journal of Applied Cognitive Psychology.