In a polygraph test, examiners record physiological responses (blood pressure, heart rate and skin conductivity) as you answer questions. They then compare these recordings to your response to control questions that are not related to the case at hand.

Experts say liars show increased arousal when answering relevant questions, while truth tellers do not. This is why liars use countermeasures to reduce their arousal and trick the polygraph.

Lie Detectors

The lie detector test is a cultural icon, appearing in everything from crime dramas to ads. But can it really detect lying?

A polygraph examiner will place sensors on your body, including a blood pressure cuff, two pneumographs that measure your breathing, and electrodes that attach to your fingers to record your skin’s electrical conductance. He will then ask you a series of questions, some of which are designed to trigger the stress response that occurs when you tell a lie.

The machine records the responses, and a computer algorithm determines whether you are telling the truth or not. According to the American Polygraph Association, which is made up of polygraph examiners, the accuracy rate of a polygraph is around 87%. Unfortunately, it’s not foolproof – liars can use a variety of countermeasures to evade detection. And false positives can have serious consequences, including lost job opportunities and damaged reputations. Even so, the tests are still used by both agencies and individuals.


A polygraph consists of a series of sensors connected to your body, including a blood pressure cuff, two pneumographs that measure breathing and electrodes on your fingers to measure skin conductivity. A trained examiner then conducts a baseline test with neutral questions and then intersperses relevant and control questions.

The premise behind polygraphs is that you produce different physiological responses when lying than telling the truth. For example, lying typically makes your heart race and causes you to pant, while you might not experience such a response when speaking the truth. A physiology reader supposedly picks up these changes and then compares them to your response to the relevant questions, determining whether you were lying or not.

The problem is that these responses can also be triggered by things like hypoglycemia, fear, anxiety, PTSD, psychosis or alcohol withdrawal. Luckily, there are a few ways to beat the test. One trick is to conceal your knowledge of polygraph testing, so that the examiner thinks you have no idea what’s going on.For more info I’ll suggest you visit the website Lie Detector Test Price.

Line Graphs

Using rubber tubes on the chest and abdomen, metal plates on the fingers, and a blood pressure cuff around the arm, polygraph machines monitor heart rate, perspiration, and blood pressure as you answer questions. The examiner looks for changes in these readings to identify whether you are telling the truth or lying. The examiner asks you both relevant questions about a specific event and broader so-called control questions to establish a baseline. If you lie about the specific incident, your reaction should be significantly larger to the relevant questions than to the control ones.

Wired cites records of polygraph use by police departments and lawsuits to show that not only do “failure” rates vary widely from one examiner to the next, but that black people are disproportionately falsely “failed.” Drugs, including many antihypertensives and anxiety medications, as well as caffeine, nicotine, cough remedies, and some foods, can interfere with a polygraph test’s accuracy. Also, diagnosed sociopaths and psychopaths may not be able to control their responses to the questions.


Scientists and law enforcement believe that a person can beat a lie detector test by changing their physiological response during relevant and control questions. They look for unusual peaks and dips in heart rate, breathing, sweat level and blood pressure when answering a question. The examiner then compares the peaks and dips to a database of known truthful responses. If the peaks and dips match the true answers, the examiner can determine that the subject is lying.

Spontaneous countermeasures include acting distraught or imagining upsetting circumstances to alter one’s emotional state and physiological responses. Other techniques involve controlled breathing or focusing on calming mental imagery to suppress one’s reactions. Some individuals have even gone so far as to put a thumbtack in their shoe, as seen in the movie “Ocean’s Eleven.” Whether or not you can successfully beat a lie detector test depends on countless variables, including the examiner and the type of test. A successful result, called “Deception Not Indicated,” means that the examiner did not find any deception in your answers to relevant and control questions.