What is a polygraph test? Who are Supreme Court nominee's accusers? How are they carried out? Image source, Science Photo Library. Polygraphs measure blood pressure, changes in a person's breathing, and sweating. The curious history of the lie detector. Can you cheat? Yes, according to the experts. This video can not be played To play this video you need to enable JavaScript in your browser. So do they work? Some experts say the fundamental premise is flawed.
Washington officials experimenting with an early polygraph in Related Topics. Published 5 October Published 21 May Published 12 September When you engage in a false narrative or a lie , your respiratory and heart rate will increase and you may even start to sweat.
While people may vary in the ability to tell a lie, most of the time your body will react in this same way. Exceptions to this rule are, for example, psychopaths, who lack empathy and therefore do not exhibit the typical physiological stress responses when telling a lie.
Brain imaging studies have shown what really happens in the brain when you tell a lie. Lying generally involves more effort than telling the truth, and because of this, it involves the prefrontal cortex. Participants answered questions about their daily routine by pressing a yes or no button on a screen. Depending on the color of the writing, they were to answer either truthfully or with a lie. The results showed participants needed more time to formulate a dishonest answer than an honest one, and certain parts of the prefrontal cortex were more active when they were lying.
Further research explains that three main areas of the brain are stimulated during deception — the frontal lobe works to suppress the truth, the limbic system activates due to the anxiety that comes from lying, and the temporal lobe activates in response to retrieving memories and creating mental imagery fabricating a believable lie.
In a study , Duke psychologist Dan Ariely and his colleagues showed how dishonesty can alter your brain, making it easier to tell lies in the future. When people told lies, the scientists noticed a burst of activity in the amygdala, the part of the brain involved in fear, anxiety, and emotional responses.
When the scientists had their subject play a game in which they won money by deceiving their partner, they noticed the negative signals from the amygdala begin to decrease.
Then the real questions being tested by the polygraph are asked. Throughout questioning, all of the person's signals are recorded on the moving paper.
Both during and after the test, a polygraph examiner can look at the graphs and can see whether the vital signs changed significantly on any of the questions.
In general, a significant change such as a faster heart rate, higher blood pressure, increased perspiration indicates that the person is lying.
When a well-trained examiner uses a polygraph, he or she can detect lying with high accuracy. However, because the examiner's interpretation is subjective and because different people react differently to lying, a polygraph test is not perfect and can be fooled. Sign up for our Newsletter! Mobile Newsletter banner close. Mobile Newsletter chat close. Mobile Newsletter chat dots. Mobile Newsletter chat avatar.
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