But this theory didn’t hold up when it was tested by a team of British and North American psychologists. They found no pattern in the upward eye movements of liars and truth tellers, whether they were observed in the laboratory or during real-life news conferences. The researchers also found that people who were trained to look for these eye movements did not do any better than a control group at detecting liars.

“There is no Pinocchio’s nose — no one cue that will always accompany deception,” says an author of the eye-movement study, Leanne ten Brinke, a psychologist at the University of California, Berkeley.

She and some researchers argue that it may nonetheless be possible to detect certain kinds of “high stakes” lies by training experts to look for a constellation of body cues. Stephen Porter of the University of British Columbia says the poor success rate in studies is caused partly by the limitations of laboratory experiments in which subjects are often asked to lie about things that don’t really matter to them. Liars may show more stress in a real-life situation when much depends on being believed.

In a study last year, psychologists at the University of British Columbia trained professionals in forensics to look for an array of facial expressions and other signs of stress or inconsistency in someone telling a story. Then these professionals looked at news footage of people pleading for the return of a missing relative. Some of the pleaders were sincere, but others were lying (as eventually revealed by evidence that they had already murdered the relative). The trained professionals were able to identify the liars with an 80 percent accuracy rate.

That’s an impressive record, but it’s only one experiment, and many researchers question how reliably these techniques can be applied in the real world. Other studies, including ones involving police interrogations, have found that people are not always better at detecting high-stakes lies than lesser ones. The fear of being charged with a crime can make an innocent person look suspiciously nervous, too.