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Are your patients truthful?

Dr Raj Persaud  
Consultant Psychiatrist
Maudsley Hospital,
London

How good are you at spotting a liar? We tend to think of nursing as a collaborative, supportive and consensual profession where you are not trying to catch out your patients telling untruths.
In fact, in most careers that interact with the public an provide some kind of gatekeeping role to further resources, "deception detection" plays an important role. Social workers, nurses and doctors often make decisions based on whether their clients are really reporting the truth about symptoms or problems.
Professionals who are supposed to spot lies as a central part of their jobs and who are meant to have a lot of specific experience in this area, such as police officers and customs officials, actually perform no better than at the level of chance when trying to detect a lie.
In one famous recent experiment of precisely the kind of high-stakes situation the police regularly face, officers were exposed to videotaped press conferences of people who were asking the general public for help in finding their relatives, or the murderers of their relatives. In fact, all those people lied during the press conferences, and they were all subsequently found guilty of killing their own relatives. The police officers, who didn't know this background to the tapes, were asked whether they could spot any deceit. They did not perform better than could be expected by chance.
Psychologist Professor Aldert Vrij from the University of  Portsmouth, who conducted the experiment, has found in his experience that the only professionals who have been shown by formal psychological testing to be better than the general public are officers who work for the US Secret Service and the FBI. But this could be partly because these agents seem to adopt a powerful but simple strategy - they don't appear to trust anyone!
Research has shown that observers can improve their skills in detecting deceit if they are taught what really are reliable indicators of deception. The key to remember is that liars are having to manufacture reality, and that usually requires a lot more intellectual effort than simply reporting the truth! Plus, liars need to monitor closely how their story is being received so as to know whether to modify their strategy or not. Truth-tellers are not so involved in monitoring the listener, because disbelief is less of an issue for them - after all, they know they are telling the truth!
As a result, liars usually watch the listener closely rather than look away - so gaze avoidance is not something to look for - rather, someone who maintains more eye contact than usual is the person to be concerned about as a liar. Also, deceivers take longer to answer questions, pause more, are not as fluent in the flow of their answers and, if they are very good liars, tend to make fewer gestures, to try to ensure they don't "leak" body language clues as to their lying.
Another useful tip to remember from the scientific psychological research into deceit is that liars experience three main emotions when lying: fear of being caught, excitement at the opportunity of fooling someone ("duping delight") and guilt. If you are vigilant for those particular emotions you are more likely to spot them in the form of "micro" expressions - facial movements that appear for short periods of time and betray those emotions before they are rapidly covered up.
Using tips such as these from what is scientifically known about the psychology of deception, it is clear that with enough practice anyone can learn to dramatically improve their rate of reliably detecting deceit in others. But the puzzle remains as to how so many professional "lie detectors" such as police officers and customs ­officials remain so lamentably bad at spotting liars.
Perhaps their overconfidence as to their ability comes from not realising how many people they let go who successfully duped them. After all, as you successfully clear Customs despite the 10 bumper packs of cigarettes in your luggage, you are hardly likely to crow about it behind the backs of the officers, are you?