Despite a range of useful hints and tips, there is no foolproof way to spot a liar. But research has shown that professionals (in this case federal agents) who spend a lot of time trying to tell if people are lying to them are consistently better at spotting lies than us ordinary individuals. They use a wide range of techniques but most involve comparing how someone behaves when they are lying, with their behaviour when they are known to be telling the truth.
Just looking at someone’s eye movement, body language or stress levels in isolation is not enough to give them away as a liar. However, if you can ask enough questions you already know the answer to, you can try to calibrate these two types of behaviour and identify when someone is behaving as if they are lying.
Polygraph lie detectors act in a similar way the stress level of the subject is not the point. How the stress levels change between different types of questions and answers is what the operator is looking at. But even here, these machines cannot prove that someone is lying. Law enforcement and intelligence agencies tend to use polygraphs more as a way of pressurising suspects to admit what they know rather than identifying specific lies.
Recently reality TV has helped to move the science of lie detection on, with the identification of micro-gestures. When you lie, you momentarily give away your true feelings on your face. So, as you say ‘of course I like you,’ to someone you actually hate, your face makes a quick grimace before being replaced by a happy smile. These micro-gestures are so quick that we can’t normally see them. Psychologists who have replayed and paused videotape from the British reality TV show Big Brother, have however been able to identify them. Of course, this isn’t something you or I would do to our friends, but perhaps police in future could videotape interrogation interviews to look for these passing grimaces.
In the future we may be able to use brain scans to identify liars. Functional magnetic resonance imagers (fMRI) measure blood flow in the brain to see which parts are active. Researchers have already used them to identify when someone has seen a specific image before, by monitoring blood flow in the part of the brain used for recognition. So, without even speaking, you might give away the fact that you have been in a specific location, or seen a specific thing.
This technology is also dependent on calibration. We each use slightly different parts of our brain when we recognise something so we cannot look in isolation at the location of blood flow when an image is shown. Instead, we must compare how the blood flow changes between different known’ and unknown’ images.
Even with the most technological solutions, the innermost workings of our brains, and our own little white lies, remain difficult to categorically identify.
