In Ricky Gervais's new movie, The Invention of Lying, he plays a character called Mark Bellison who lives in a parallel universe where everyone tells the truth - all the time. No one has the ability to tell a lie, even the littlest, whitest one. Even advertising executives have to tell it like it is, with catchphrases like: "Pepsi. When They Don't Have Coke." One day, Mark accidentally tells a fib and this new-found ability to be dishonest transforms his life, with predictably amusing Gervais-esque results.
One of the film's more serious premises is that a world in which no one ever lies is actually a brutal, rather unpleasant place, because most of us tell small, well-meaning lies all the time - whether to protect people's feelings or just oil the wheels of social interaction; telling your wife that she doesn't look big in that dress, for example, or your five-year-old that Santa really does live at the North Pole. The trouble is, humans also have a tendency to tell bigger, nastier and far more damaging lies.
Deception can be a terrible thing, which is why so many millions of words have been written about how to detect it. Go online right now and after an hour's research you will have hundreds of tips for spotting a liar at your disposal. Stammering, breaking eye contact, gazing up and to the right, including too much detail in your story, fidgeting, never using the word "I"- the list goes on and on. Many of these supposedly infallible techniques are from purported "experts" too, which is why so many of us believe them. Just one problem: most of these tips are absolute rubbish. For example, there's not a scrap of scientific evidence to show that stammering means that someone is being untruthful. Ditto for breaking eye contact or fidgeting. These are just myths, backed up by hearsay or poor-quality, unreliable research, told so many times that people eventually take them as the truth.
So, if most of the commonly accepted lie-detection techniques are nonsense, is it really possible to tell when someone's lying? If you suspect your colleague of surreptitiously stabbing you in the back while smiling to your face, can you learn to catch them out? Yes, says Dr Lucy Akehurst, from the University of Portsmouth, one of the UK's leading experts on the science of deceit. But before she reveals her top lie-detecting tips, let's explode some of the more common myths. "One of the worst misconceptions concerns fidgeting," she says, "like tapping your foot or moving your hands and arms around when you lie, because some people do that when they're telling the truth. That's especially true of different cultures, where some are much more animated while speaking than others."
What about the old chestnut about looking up and to the right? "That's rubbish too," insists Akehurst. "There's no scientific evidence whatsoever that people look up when they lie. It's funny, because even the police are sucked in by this one, but it's just a theory from neurolinguistic programming without a single high-quality study to back it up." Akehurst may have chosen an unusual area of scientific specialism, but she is as much of a stickler for reliable research as a physicist or biochemist. "We won't believe in any clues to deception unless there is robust evidence comparing liars and truth-tellers," she maintains.
Fair enough. But if fidgeting is one of the misconceptions, what does denote a lie? Of all the telltale signs of dishonesty, she says that pitch of voice is the most reliable. "This comes out over and over again in our research," she explains. "Liars have a slightly higher pitch of voice than truth-tellers. There's some really robust evidence proving this to be the case. And insurance companies now use technology that can measure people's pitch of voice over the phone. Because they are receiving more and more fraudulent claims, they conduct interviews over the phone and this technology detects tiny fluctuations in claimants' voices."
So, insurance scammers beware. And, if new research on handwriting, published in August in Applied Cognitive Psychology, is to be believed, those sending less-than-honest claims through the post might also be in trouble. The study claims that a computerised tool could detect deceptive sentences written by hand. How? Apparently, some physical properties of handwriting are harder to control than others, like the length, height and width of each writing stroke and pressure applied to the writing surface. The researchers found that these characteristics differed when someone is writing deceptive sentences as opposed to truthful ones.
One wonders how useful this is in the age of the typed word, but developments such as this are of great interest to law-enforcement professionals, who use ever more hi-tech means to catch liars in the act. One reason for this is that the polygraph machine, long a fixture of most interrogation rooms, often produces inconclusive results. As a result, American researchers are currently developing lie-detection technologies they hope will banish polygraphs to the history books. At the University of Houston, the computer scientist Joannis Pavlidis is trying to uncover lies by measuring heat around the eyes - a sign of increased blood flow associated with stress. And Jennifer Vendemia, a professor of psychology at the University of South Carolina, is using brainwaves to detect deception.
"When you tell a lie, it's a cognitive behaviour like any other, such as doing a challenging mathematical problem," she explains. "You must engage in a certain number of cognitive activities - you have to pull the truthful information from your memory, inhibit that information, create a deceptive response and make a decision to deliver that response. So telling a lie is a complicated process involving different parts of the brain."
Vendemia is developing ways to measure this activity in the brain, and claims that, in laboratory tests, her brainwave-tracking system detects 94 per cent of lies. Another US psychologist specialising in lie-detection is Dr Paul Ekman, a pioneering researcher who is an expert on the study of emotions and their relation to facial expressions. Ekman is such a legend in this field that the lie-detecting hero in the hit HBO drama Lie to Me, played by Tim Roth, is based on him.
Before revealing his unique approach, Ekman explains why lying shouldn't always be frowned upon. "The idea that all lies are bad is a myth," he says. "The truth can also be used crudely and cruelly - and the fundamental nature of politeness is that we aren't always truthful. For example, we thank our aunt for the hideous ties we will never wear because we don't want to hurt her feelings." Of course, not all lies are so benign. "Then there are lies that destroy trust, undermine intimate relationships and, of course, in criminal activity, there is always a decision made before committing a crime not to be truthful about it."
Ekman also has a set of myths that he is keen to dispel. "One of the more interesting myths is that you can always tell when a child is lying. That's true up to about age eight, but after that kids' lies are about as successful as those of adults. Also, the idea that X is a certain sign of lying and whenever it's present someone is being deceitful, is just not the case. We call that the 'Pinocchio's nose theory' and there are many claims about what X is, but the truth is there's no such thing."
Instead, Ekman says there are certain clues which, if present, should be explored further. One of the most reliable of these clues is the presence of "micro-expressions". These are very brief - around 1/15 or 1/25 of a second - facial expressions that occur when people deliberately try to conceal their emotions. Micro-expressions are invisible to almost everyone unless they have had specific training.
But, according to Ekman, after just an hour's training most people can achieve 90 per cent accuracy in spotting things that others miss. "A micro-expression happens so fast that you can miss them if not looking closely," he says. "Remember they are merely a sign of concealed emotion, which doesn't necessarily mean someone is lying or that they are guilty. But if you do spot one it's a good sign that you should explore further, to try and find out why that emotion is being concealed."
Those interested in finding out more should visit the website www.paulekman.com, which offers simple training that will teach you how to detect those flashes of concealment. A word of warning though: "There is one problem," says Ekman ominously. "You may not always want to know that someone's lying. For example, when your spouse tells you how much they enjoyed a meal, or how funny they found your joke, when in reality they thought it stank. It's a very powerful tool and you can't turn it off once you've learnt it."
If you are willing to take the risk, Akehurst has some more tips for amateur sleuths. "One thing we're really big on is cognitive complexity," she says. "Our studies consistently show that liars have to think harder than truth-tellers. So if you suspect someone is lying to you, anything you can do to make them think a bit harder is good. For example, if you suspect that a builder has given you an inflated quote, you could ask him to break it down for you. Ask how on earth he came up with that figure. If he's lying he'll find it hard to answer a more challenging question."
According to Akehurst, it's also worth listening for pregnant pauses. "Liars tend to pause more before they answer a question," she says. "We call that 'response latency' and it happens because they're having to think a bit harder about the response they're going to come up with. And when liars are talking they tend to include longer pauses, because they're having to think carefully about their answer or the story they are concocting."
Lie-detection is clearly a fascinating, if much misunderstood art. And whichever of these techniques you choose to apply, at least you'll know that if someone guarantees they can spot a liar by their tendency to stammer, fidget or gaze up at the ceiling, they are either misguided or being economical with the truth.