In continuation of our topic with you about This lying lie detector or the myth of the polygraph, I want to give you some examples of how you can deceive a polygraph.
The principle of operation of a lie detector is based on changes in physiological parameters such as respiratory rate, pulse, blood pressure and galvanic skin response (that is, the skin's resistance to electric current). Other methods may include observing changes in pupil width or brain activity using MRI.
Polygraph test results are not accepted by the criminal courts in the United States and most European countries. However, the authorities found other uses for this invention. In Britain, probation inspectors use a detector to track serious sex offenders, resulting in dozens of people going back to jail. In the United States, polygraphs are used in recruiting personnel for the CIA and other important government departments.
But do they have a vulnerability?
Walt Hudson, president of the American Association of Polygraph Operators, served with the Texas Police for 25 years. He insists on the usefulness of this device in the investigation of crimes. “It helps narrow the circle of suspects. This is a quick and easy way to test a person and decide whether it is worth working in this direction further or whether it is necessary to switch to other versions."
Typically, the operators' job is to alternate between important (have you robbed a bank?) And irrelevant (have you ever taken someone else's?) Questions. Since it is impossible to answer "no" to the last type of questions without twisting one's heart at all, the indicators of the instruments when answering them can be considered initial data.
The idea is to get an idea of how a person responds to a lie without being under stress. Thus, the operator can decipher the test results more accurately than if he compared them only with the obvious truth (for example, when answering the question "Are you a man?")
George Maschke, who runs the antipolygraph.org website since 2000, argues that in order to outwit the polygraph, you need to figure out a security question and amplify your reaction to it.
“When you are asked a security question like 'Have you ever had to lie to get out of trouble?' you can try to solve a math problem in your head very quickly so that mental activity leads to increased sweating, increased breathing, etc. If you can improve your reaction to the security question, then in theory you can safely pass the test."
According to Hudson, this technique can actually fool novice operators, but an experienced person is much more difficult to trick:
“It's not that hard to deliberately change the parameters of the human body, and there are many anti-polygraph sites that teach this. What these sites fail to teach is how to change the natural response to an operator's question. When the subject tries to change or control the normal responses of his body, the machine records abnormal data that the operator can easily recognize. They are specially trained to recognize unnatural physiological responses.
Nevertheless, the results of polygraph tests are found to be wrong about 10-15 percent of the time. At the same time, a number of researchers are especially concerned that most often the polygraph gives erroneous positive results (that is, innocent people are mistaken for guilty), compared to erroneous negative (that is, it considers guilty people innocent).
Hudson believes that some people give true answers but fail the test by trying too hard to control their body responses. “When an honest person unwittingly changes their physiological parameters, trying their best to pass the test safely, their answers can be mistaken for a lie,” he says.
Many researchers consider the very principle of the polygraph to be erroneous, since the physiological response of the body is not always an indicator of a lie. In 2011, experts from the American Association of Polygraph Operators conducted their own research and concluded that test results are incorrect 15 percent of the time.