Most lies are of the white kind, that do nobody harm and generally make life far easier than it would be if we all knew what was going on. Other lies are more important, actually having a distinct purpose. Criminals, adulterers and spies all need to lie regularly if they are to stay out of trouble, and people are paid vast amount of money to work out exactly who is telling the truth.

Lies are tricky things. They are difficult to pin down, having no odour, image or any kind of emmisions. The usual way to uncover a lie is to collect evidence that points to the contrary. The police have to spend many long hours searching for clues, to piece together the real story in the face of six different versions from six different people. Private investigators make a very comfortable living sitting in cars outside houses which have their blinds mysteriousely pulled down in the middle of the day. Life would be far easier for some people if there were a foolproof method for spotting lies.

Lie Detectors

But does such a method exist? No. Contrary to popular beliefs, the famous lie detector is a myth. No machine yet invented can spot a lie. Very few people, either. Study after study has shown that humam lie detectors are a myth- people who think they can spot a lie do no better than people who don't think so, who in turn do no better than chance dictates they should¹. The only humans who do show lie detecting abilites are people with a type of aphasia which prevents them from understanding speech. This is thought to be because there are subtle changes in people faces betweens when they are sincerly expressing an emotion, and attempting to replicate an emotion, which aren't noticed by most people because they are concentrating too hard on the spoken words. The only other group who are better than average at detecting lies are secret agents, which is unsuprising considering their lifestyle.

That is not to say that there is no way to detect lies. There are pointers, which can be picked up if the observer knows what to look for. However, often these signs are misinterpreted to mean something they do not.

The signs change with the individual liar of course, and the lie itself. The motive behind the lie will affect how comfortable the teller is, and the more comfortable they are, the less likely they are to be caught out.

Lies can be divided different catergories in many ways, but a widely held view is that there are four types of lie;

• Pro-social; Lying to help someone else
• Self-enhancement; Lying to make yourself look better while not hurting another.
• Selfish; Lying to benifit the self at the expense of another.
• Anti-social; Lying to deliberately damage another.

The type of lie, and whether it is in keeping with the liars character, dictates how apparent the signs are. Occasionally they are extremely obvious, especially when the liar is feeling guilty.

Obvious signs include;

• Over denial- repeating protests of innocence
• Stuttering
• Inability to keep the hands still- picking at a napkin or twisting a button
• Unwillingness to make eye contact, or never breaking eye contact,

but the majority of people, if they are intending to tell the proverbial whopper, fabricate their story long beforehand, and so rarely get caught out so easily. There are, of course more subtle signs, which most people miss, and which can affect even word-perfect liars. They include;

• Over formal speech- using long words, correct grammer and the full forms of words or phrases that would normally be shortened, neglecting don't, wouldn't and any slang words for more correct terms.
• Very few gestures, and no pointing.
• Attempting to justify every detail with lengthy explanations
• Mismatch between tone of voice and expression.

People who are used to detecting lies develop an instinct towards the more obscure signs, perhaps without even consciousely noticing them. The rest of the people on the planet have a great deal of difficulty working out when someone is telling the truth. Which is why there are so many attempts to make a foolproof machine for catching lies. The industry name for a lie detecting machine is a polygraph. Poly means lots, and so the machine name means lots of graphs. Which is exactly what a polygraph is- it meansures several different things and the readings can be used together to work out how comfortable a person is at that particular time.

The Principles

Polygraphs work on the assumption that people telling lies are uncomfortable. Maybe not very much, but nevertheless they feel differently to when they're telling the truth. This alone means that patholigical liars often fool lie detector tests because they show no change when they tell a lie. A polygraph assumes that there are involuntary changes to your body when you lie. Often measured are heart rate, blood pressure, sweat (by placing galvanometers over the fingertips and measuring resistance) and breathing rate, with some machines measuring tremors in the voice or rate of movement of particular muscles. Taken together, there is often a change in the reading between true and false answers.

Cheat!

This reading is, however, not solid evidence for anything. The very act of having to defend their character may agitate a perfectly innocent person to the extent where the machine records that they are lying. There are also various ways to cheat the polygraph;

• The examinee may bite their tongue, or press their toe onto a pin stowed in their shoe, just before they answer every question. The pain would prompt a greater physiological response than a lie would, so it would drown out the response to the lie, and would mean that the response to the test would be the same every time.
• The examinee may use deodorant on their fingertips if they know they will be measured for sweatiness. This absorbs the sweat and so fixes the results.
• The subject may use a sedative, to dull their body's response to the point where the difference between the reactions to truth and lies is so small as to make the test too uncertain.

There are two types of wrong polygraph readings. False positive is when a subject has tested positive for a lie, although they are in fact telling the truth and is the commonest type of error. False negative is when a subject has been aquitted of lying, even though they are guilty.

A polygraph interview will usually take several hours, and takes place in a room where only the interviewers, who like to be called forensic psychophysiologists², and the subject are present, although others can be watching from behind one way mirrors. First the examiner and the subject have a basic chat, where the examiner calibrates the equipment, and tries to put the subject at ease. The actual test comes later when the examiner asks several relevent questions and also some control questions to check that the responses are still the same. Analysis of the questions takes place afterwards.

Legality

Polygraph tests are an ambigious area of the law. Depending on where you are, there are laws regulating their use. Many courts will not accept evidence from a polygraph test, because there is too big an area of uncertainty- although lawyers are allowed to mention them in defence of their client if they wish. Some places consider them an infringement of civil rights and ban people from making others take them. If they are to be used by companies, there are laws relating to the questions that can be asked, and no employee can be forced to take one- although the company is welcome to draw whatever conclusions they wish from that refusal. Polygraphs are very widely used in the United States, with the federal government being the largest user of them, and the police using them to assist in their investigations, even though they are not always used as actual evidence.

Many people are opposed to polygraph tests, and there are many organisations which oppose them, such as AntiPolygraph.org. They do this because they claim they are inaccurate- figures range form 70% to 90% accuracy depending on who delivers the statistics and whether they count 'inconclusive' results as wrong results, or merely discard them since they gave no evidence on way or the other. There are scientists who point out that they do not detect lies, merely the physical state of the subject at the time, and there are those in the legal industry who object to the fact that polygraphs can be used as evidence by a defendant, but not the prosecution. There are also people who claim that polygraph tests are immoral and a violation of human rights, and campaign against them.

Defenders of polygraphs, like the American Polygraph Association argue that people with nothing to hide wouldn't be so opposed to them, and point out that they are very rarely used on their own- they are usually presented in conjunction with other evidence. There is also the fact that they are improving all the time- computer programmes exist which analyse the voice for tremors, which is far less intimidating than being attached to wires, and new research is sugesting that brainwaves change when lies are told, paving the way for supreme lie detectors of the future.

Chemicals?

Truth inducing drugs are a staple part in the plot of many Hollywood films, and holds its' own as an incredibly convenient idea which can help the plot of a book along nicely. But is there any credibilty behind the romantic ideal?

Well, there's the unsophisticated but highly effective method of torture, inducing nasty symptoms and generally weakening the subjects until they crack. These drugs are not what the majority of people mean when they talk about a truth inducing drug, but nevertheless that is probably the most common kind.

There also exists a form of truth serum, thiopental sodium, which is trademarked under the name Sodium Pentothal by Abbott Laboratories. This is an anaesthetic, but allegedly, when a small enough dose is administered the patient does not lose consciouseness; instead they enter a very relaxed state. They are then far more open to suggestion and lose many of their inhibitions. This in turn makes them more likely to voice what they are thinking- but they keep their self-control, and would not do or say anything against their nature. This would make it a poor tool in detecting deliberate lies, since if the subject is unwilling to tell the truth they will not be forced to do so.