Lie detectors
By Mark Steer
Lie detectors to detect the physiological changes that lying can produce have been used for centuries. A suspect in ancient China had to listen to a prosecutor’s speech with their mouth full of dry rice. The idea was that people don’t salivate when anxious; therefore, if the rice was dry at the end of the speech the person was guilty.Modern lie detectors, or polygraphs, which measure a range of physiological responses such as pulse rate, blood pressure and skin conductivity, were invented in the earlier part of twentieth century.
In most of us, our heart rates and blood pressure will increase when we lie, and on top of that we’ll also sweat a bit. Increased moisture on the skin increases with ease with which electrical currents can pass across it, which is why skin conductivity is measured.
While some people will claim that polygraph tests are 90-95% accurate, there is little scientific evidence to back this up. One study estimated that the average accuracy is about 61%, which is that much better than chance. Furthermore, a number of known spies have passed polygraph tests with flying colours; double-agent Aldrich Ames twice took the test and neither time were his lies detected. The key, he later said was to be well rested, remain calm and be friendly to the interrogator.Effectiveness
Works really well on some people – the nervous ones – but performs pretty miserably on the rest on the population. 2/5
Ethics
There’s nothing too bad about a polygraph test, the electrodes are kept on the outside of the body after all. 5/5
How to get out of it
You can take the spy’s advice and remain cool, calm and collected, however, if you don’t feel you can do that, bite your tongue or dig your fingernails into your palms before you ask each question. The pain will cause bigger physiological responses than lying will, so you’ll swamp any reading. Crafty!
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