Have you told a lie yet today? Go on - be honest. Maybe you unfairly blamed the traffic on your late arrival in the office, or pretended you were in a meeting when the unwelcome phone call came. Perhaps you told the Big Issue vendor that you didn't have the change jangling in your pocket, added an extra receipt to your expenses claim or invented excuses to get out of the after-work drinks-do you couldn't be bothered with.
If so, you're far from alone - psychologists reckon we tell a couple of white lies every day. But with the growing development of deception detection technology, we may need to start thinking twice about it.
From voice-stress-analysis devices to high-tech brain scans, it seems everyone is interested in finding out if we're fibbing - friends, insurance companies and the government. Whether or not it will change our behaviour is another matter. According to the experts, telling untruths will be a hard habit to break.
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"Basically, the world wouldn't really function if we didn't tell some lies," says Dr Paul Seager, a specialist in the psychology of deception at University of Central Lancashire. "They keep the machinery running smoothly. White lies are essential."
Of course, most people have boundaries. The problems arise, explains Seager, when we transgress those rules to tell increasingly manipulative and damaging untruths - or, in the case of criminality, to cover misdemeanours and get off scott-free.
Yet no matter what the shade of a lie - be it black, white or grey - its detection might be harder than you think. "Most people aren't as good as spotting liars as they believe themselves to be," explains Seager. "Generally we're only about 50% accurate - the odds are not much better than chance."
To counter that failing, humans have battled through the ages to find ways of forcing the truth from their fellow man. In medieval Europe the Inquisition used thumbscrews and racks to obtain information, and "trial by ordeal" was commonplace. Suspects who could walk on hot coals uninjured were considered innocent.
It wasn't until the early twentieth century that the first machine was invented that claimed to help experts detect lies in a measurable and scientific way. First developed by an academic at the University of California, the modern polygraph measures changes in physiology suggesting high levels of anxiety and stress - such as increased heat, breathing rate and sweat production - in an attempt to indicate whether lies are being told. The investigator is trained to ask questions that will help differentiate between the inevitable stress caused by the test procedure and that caused by telling lies.
The use of such machines has always been controversial, and although the American Polygraph Association claims accuracy is more than 90%, there is little scientific evidence to support this. Test results are not permissible in UK courts.
Yet interest in lie detectors is far from waning. According to Bruce Burgess, who carries out polygraph tests on the Jeremy Kyle TV show, his services are more in demand than ever. When he set up his testing company, Distress Services, in 1999, he was seeing only one or two clients a month. Now he and his team of testers around the country deal with hundreds of private cases a year.
"Most of the time I'm asked to test people accused of company theft or fraud, marital infidelity, or even those accused of child or sex abuse," he explains.
While he is sceptical that lie-detector use is always helpful, especially in the case of martial infidelity, he is adamant about its reliability. "It could make a valuable contribution to police investigations," he insists.
It seems the UK government might even agree. The Home Office is considering plans to test all paedophiles south of the border every six months to check they are sticking to their parole conditions. The results of a pilot study, carried out by Professor Don Grubin at Newcastle University, were released in December 2006 and suggested that four in 10 lied about their behaviour since release.
Not everyone is convinced. Dr Keith Ashcroft, a leading forensic psychologist based in Edinburgh, is deeply concerned about such a development. "I've got a polygraph machine and people ask me to do tests, but I won't use it. It would be unethical," he says, claiming the notion of lie detection helps drive a climate of fear and an erosion of civil liberties.
"Most private testers offer no therapy or back-up but they come and do the test and people are left to get on with it clutching this awful bit of paper. They such testers are in and out like rogue plumbers. The government is really complicit in this sub-culture. They are giving it legitimisation. The ramifications are alarming."
He is less dismissive of the so-called Silent Talker - a lie-detection system that uses artificial intelligence to detect and analyse thousands of human "micro-gestures", under development at Manchester Metropolitan University. "We have looked at systems across the world and are convinced that this is the most sophisticated," says project director Dr Zuhair Bandar, claiming that its 80% accuracy rating is 10% higher than competitors.
The team is not the only one working on new techniques. Another, at the University of Pennsylvania, is developing the "cognosensor", which works by examining changes in blood flow to the brain, while academics at Cornell University in New York state are developing e-mail software that will apparently weed out the genuine 14-year-olds in an online chatroom from the 50-year-old impostors.
On a different tack, Maureen O'Sullivan of the University of San Francisco is carrying out studies on the "wizards" of deception detection, those who have been identified as particularly skilled at spotting liars.
It's not all about catching out the mad, bad and dangerous. Several insurance companies have already introduced voice- stress technologies on phone lines to help protect against fraudulent claims, which cost the industry about £1.5bn annually. While the science is dismissed by some, most claim it is working.
"It is in part a deterrent," explains Kelly Ostler of the Association of British Insurers. "People might think twice if they think they might get caught and risk being denied access to financial products or branded a fraudster." The Department of Work and Pensions is also considering introducing the technology to combat benefit fraud. It seems we are even increasingly suspicious of our friends: internet phone company Skype claims that hundreds of thousands of people have downloaded its free lie-detector software, launched last year.
Dr Cosmo Hallstrom, a London-based consultant psychiatrist and expert witness, is not surprised by the growing obsession. "Our entire society is built on spin, and it seems we never really expect to hear the whole truth," he says. "We accept that advertisers will present the world in a way that does not reflect reality and we get used to hearing nothing more than half-truths from politicians. It's terrifying.
"The result is that people become extremely cynical at one level - but at another they are keener than ever to find some sort of absolute truth."
However, he is doubtful that artificial detection is the way forward. "My feeling is that none of these devices really work," he says.
Brian King, author of The Lying Ape: An Honest Guide to the History of Deception, agrees. Through the course of his research he has met various experts in detection - from police officers and psychologists to illusionists such as Derren Brown - and studied the latest technology, including brain scanning and artificial-intelligence-based detectors. "If there really was a machine capable of accurately separating out the lies, don't you think everyone would be using it?" he says with a laugh.
King believes the compulsion to lie is greater then ever. "It's got to a point where people don't think twice about lying," he says. "Often we lie simply because we are under such pressure to succeed, not to fail or to be a certain type of person. And that pressure keeps on increasing."
King, at least, isn't looking to eradicate fibs. "Imagine a world where no-one could tell lies, where we were all exposed every time we didn't tell the truth," he says. There is a pause as he considers the chaos that would ensue. "Frankly, it would be horrific." Truth or scare? My own lie test
A breakthrough in communications or a mere gimmick? Skype, the online phone company that allows you to make internet phone and video calls, launched its lie-detector plug-in - supplied by software company KishKish - last year. It says it has been downloaded by hundreds of thousands of people.
Available as a free download for Windows, it uses voice-stress software to look for signs of tall tales, which it illustrates on a graph. The marketing is fun, using Bill Clinton's infamous lie about his affair with Monica Lewinsky - "I did not have sexual relations with that woman" - to show the website graph peak from a truthful green to pants-on-fire red.
But how accurate is it in real-life situations? To put it to the test, I stepped up to the mark. As I introduced myself, the graph remained fairly level - so far, so credible. But when I tried to convince it that one of my favourite movies was The Wedding Planner, the graph shot into the red.
And when I was put under pressure to name the 52 American states, my stress levels pushed the graph through the roof, suggesting it's perhaps less about what you say than how you say it.
The truth might be out there, but I'm not sure this will help you find it.