The science of lying: Why the truth really can hurt

How do you know if someone is lying to you? What, exactly, are you supposed to look for?

A suddenly distended nose, possibly – if your name is Geppetto and your son a wooden puppet with a taste for hyperbole. Shifty eyes, more commonly. A wavering gaze. An inability to meet the stare of the inquisitor when asked to "look at me straight and tell me you mean it". Or, perhaps, a sudden divergence from the graphic norm when the speaker's vitals are being tracked by polygraph.

Whichever option you go for, whatever result it happens to yield, it wouldn't, ultimately, matter. The odds are that it was wrong. In fact, statistically speaking, it was even more likely to be wrong than if you had simply guessed at random, or had flipped a coin.

Even using the most advanced in lie-detecting technology, identifying specific falsehoods can be a stretch. The past decade has seen a number of truth-telling innovations. Electroencephalograms monitor the electric activity of the brain. Thermal imaging records one's eye temperature (people's eyes, it has been suggested, heat up when they lie). MRI scans measure blood flow to the brain. But science has yet to offer a method of specifically isolating deceptive (as opposed to, say, nervous, cagey, or intensely focused) brain activity. Humans, when it comes to separating fact from fiction, are fairly hopeless.

"This is what makes it so easy for people to be successful in their lies," says Robert Feldman, Professor of Psychology at the University of Massachusetts. "Some people are good liars and some are bad, but they all use different signals. Unless you have known them for a long time, it's very difficult to tell if they are lying." Feldman has spent some 25 years studying the science of deception. A fellow of both the American Psychological Association and the Association for Psychological Science, he has authored Liar: The Truth About Lying. In it, he argues that we all lie a lot of the time. He introduces a number of psychological principles to explain this, the most important of which is 'Liar's Advantage', a tactical leg-up made possible partly by the difficulty of lie detection and partly by our own inherent gullibility.

"We don't expect to be lied to," he explains. "And often, people are telling us what we want to hear: that we are doing a good job, or that we've been successful. The liar is trying to lie successfully and we want to believe them, so we do. There are no obstacles."

The instances of deception examined in Liar range from the mundane (claiming to know the location of a town anecdotally, so as to keep conversation moving) to the extraordinary (the financially adept student setting up a Ponzi scheme before trying to donate millions to his university). They are dotted across virtually every aspect of modern life: from our relationship with ourselves, to our interpersonal dealings, to the workplace, media and government.

Lying, says Feldman, is a basic skill that we learn early on in life. Studies of secretly observed children left alone in a room and forbidden to peek at a toy repeatedly show a widespread ability, not to say willingness, to lie, from as young as three years old. "It's very surprising. They're not particularly good at two or three, but they still use it as a social tactic. By the time they are five or six they actually become very good."

Not only do we learn deception early, and then hone our skill over time, but we use it as a means of achieving success: social, professional, sexual. Indeed, in this respect, lying has come to represent an important evolutionary tactic – one frequently replicated in the world around us. "If you can fool a member of another species and it allows you evade detection, or it allows you to evade being eaten, then that gives you an advantage," argues Feldman. He highlights the case of the Portia spider, whose deception is not only instinctive, but highly sophisticated.

Portias are unusual for two reasons: their taste for other spiders and their excellent vision, an advantage of which they appear only too aware. When hunting their fellow arachnids, they embark on a complicated bluffing game. So as to approach undetected, they wait until another vibration exists to disguise their own (a breeze, for instance). They also, more pertinently, are able to mimic the vibrations of other species. Frequently, then, their lunch is fooled into approaching them in the belief that they have found a mate. It's less survival of the fittest, more like survival of the dishonest.

With deception so significant a part of the natural world, it's little wonder we resort to it almost reflexively. Indeed, who's not to say that lying isn't an in-built part of human nature?

On this point Feldman is hesitant, not quite believing that we lie instinctively. Still, once we do develop deceptive skills there's no shortage of stimuli. Much of our environment is conditioned by falsehoods. "To advertisers, it has become acceptable to make claims that aren't entirely accurate," points out Feldman. "We'll talk about integrity and its importance, but a lot of business decisions are based on deception. We've just seen it: mortgages being inflated; the creation of a climate in which it's easier to justify certain actions."

Curiously, for all their ubiquity, we appear to be largely unaware of the mass of untruths that surrounds us – even when they spring from our own mouths. The bulk of Feldman's studies involve secretly filming volunteers as they engage in some form of interaction. "Afterwards, people are surprised to find out that they haven't been entirely honest. I'll ask them if they were being accurate and they'll say they were, but when we show them the footage they can identify all kinds of deception."

The irony of this method is its own dishonesty: the camera is hidden and volunteers are rarely told of the nature of the study, so as not to set them on guard. So Feldman lies to his guinea pigs in order to catch them lying. "One of the most common things used to be to do diary studies, where people are responsible for recording how many lies they tell," he explains. "But we faced two big problems: firstly that people may not remember exactly what they have said each day; and, secondly, that they know the study is for honesty, so they may be on their best behaviour."

Despite his methods, Feldman is part of a growing school which argues against our culture of dishonesty – not just the deliberate, targeted, dishonesty of conmen and criminals, but the day-to-day white lies that ease our social existence.

The New Statesman recently carried a piece by Australian psychologist Dorothy Rowe warning of the "network of unforeseen consequences" that we create for ourselves. It isn't just a moral, philosophical standpoint: scientific evidence increasingly backs up their views. Feldman refers to studies identifying a psychological "twinge of distress" suffered by the tellers of lies. "In the end, it makes our relationships less real. People have been found to express regret for pulling something over on another person – even when they think they are doing it to make something better."

Quite how we might pursue a more honest society is unclear. Attempts have been made to live entirely without lies – so-called 'Radical Honesty' – but this may, for anyone who has ever been asked if they like their best friend's unflattering new haircut, sound like a step too far. Certainly, for the time being the task looks like something of an uphill struggle.

Feldman's next study will focus on our behaviour on the internet. Early research indicates that our online existence only enhances dishonesty. Anyone who has spent time polishing their Facebook profile, or who has assumed an alias to comment via a newspaper website, could tell you that (though of course whether or not they would tell you remains to be seen).

Liar: The Truth About Lying is published by Virgin Books and available for £7.99

Truth-Testing Technology

Sam Muston

Polygraphs: Invented at the turn of the 20th Century, they detect physiological signs of anxiety (elevated pulse, heavy breathing). Critics, though, say these responses are not always connected to lying.

Electroencephalograms: Using EEGs to determine truthfulness began in the 1980s. Researchers identified the P300 brain-wave, which occurs just after exposure to a stimulus. Now it is believed merely to indicate recognition – rather than a lie.

Thermal imaging: In 2002 the journal Nature carried news of a revolutionary lie detector which measured thermal changes around the eyes, said to be symptomatic of deception. Or, perhaps, just nerves.

MRI scanning: According to its inventors, oxygenated blood increases in certain cortex of the brain when we lie, which shows up on MRI scans. Although widely used in the Indian court system, there is much scepticism by British scientists.