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ATTEMPTS at detecting whether someone is telling the truth is as old as humanity itself. Indeed, one theory about the origins of human intelligence is that man’s relatively large brain evolved out of the need to recognise deception in other individuals living within the same social group. Finding out the truth from unwilling interviewees came centrestage from two unrelated quarters and highlighted the difficulty of detecting deception in skilled, well-trained inveterate liars. The sole surviving gunman of the Mumbai attacks is undergoing interrogation in India that will include the injection of a so-called "truth serum" in the hope of eliciting information about his past and his associates. Meanwhile, it emerged in the Queen’s Speech recently that the government is considering the introduction of lie-detector tests to expose untruthful benefit claimants. Lie detectors, or polygraphs, do not detect lies. They monitor the physiological changes to the body — such as heartbeat and skin conductivity, or sweating — that may, or may not, be associated with failing to tell the truth. The idea behind the device is that there are involuntary actions not under conscious control of the brain that occur when someone experiences the stress of telling a lie. Those changes may go unnoticed by the human eye but can be detected by sophisticated machinery. Polygraphs are widely used in the US but have been rejected in Britain in the past because of their unreliability. Apart from whether they actually do pick up on hidden signals of lying, their accuracy is predicated on the skill of the person interpreting the machine’s signals. In extreme situations, torture and fear are one of the oldest means of extracting the truth from someone who has a motive to hide it. But that has the major disadvantage of leading people to say things under duress that they know the torturer wants to hear — as well as being an obvious breach of human rights. Another method is to ply someone with alcohol, a technique immortalised in the ancient Latin phrase "in vino veritas" — in wine there is truth — which is ascribed to the Roman scholar Pliny the Elder. The concept was perhaps most cunningly used by Josef Stalin who is said to have feigned getting drunk with comrades in order to hear what they really thought under the influence of vodka. The earliest attempts at putting lie-detection on a scientific footing go back to the start of the 20th Century and probably began with Robert House, an American obstetrician, who had noticed the remarkable effects of an anaesthetic drug called scopolamine, which was derived from the herb henbane. One of his pregnant female patients was in a state of "twilight sleep" after being given scopolamine to deal with her labour pains. Dr House had asked her husband to find a weighing scale for the newborn but he returned to the bedside empty handed, whereupon his wife told him exactly where it was while still apparently asleep. Dr House soon recognised the potential importance of scopolamine in getting people to answer questions without lying. American police forces from the 1920s onwards began to use drugs as part of their general interrogation. They experimented with the psychoactive barbiturates sodium pentothal and sodium amytal. However, it soon emerged that the drugs were being misused on interrogation suspects in order to incriminate them. It became clear that these drugs had the same problem as torture — they made people say things that they thought the interrogators wanted to hear. Interestingly, during the Second World War the first intravenous anaesthetics — the same class of barbiturates — were used on traumatised soldiers who had lost their memories to get them to remember what had happened to them. After the war, some American doctors continued to use sodium amytal and sodium pentothal on psychiatric patients as part of their therapy to get them to talk about hidden memories. However, some of these doctors also took their expertise in this area to the police and the US Government. Scientists have produced fairly convincing evidence over the decades that drugs such as sodium pentothal do not extract truthful memories from people. Instead, they tend to make interviewees more talkative in a way that makes them suggestible to cues elicited by interviewers for what they would like to hear. By arrangement with The Independent
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