The polygraph exam is the benchmark in detecting deception in people. According to experts, it’s up to 97% accurate at detecting people lying about something. This technology is so effective at weeding out liars that even government organizations like the CIA and FBI use polygraphs to uncover liars in interrogations.

With over a century of development, the polygraph is a highly refined and effective device, but it’s not perfect. Some circumstances and actions might contaminate the test results. This post examines five things that might cause false positives or exclusions in lie detector exams.


How the Polygraph Exam Works

You’ll receive advanced notice of your polygraph exam at least 48 hours before the test. On exam day, you enter a room with only yourself and the examiner present. The test takes anywhere from 45 to 90 minutes, depending on the circumstances surrounding its use, and you’ll be sitting in a chair for the entire test period.

When you arrive at the exam room, the examiner greets you and runs you through the test parameters and what to expect from the process. After you’re confutable, they hook you up to the instrumentation.

They’ll strap corrugated rubber tubes to your chest and abdomen and sensors to your fingertips. The instruments connect to a control box feeding into a laptop running software the examiner reads during the polygraph exam.

You won’t receive your results immediately after the lie detector test, so don’t bother asking the examiner if you passed or failed. They’ll review your test results at their office later that day and draft a report for your boss.

It takes 48 to 72 hours for the examiner to deliver their report, and you won’t hear from them again after the test. Your boss or manager is responsible for providing you with the test results and explaining the outcome of the exam and its findings.


How Does the Polygraph Machine Detect Deception?

The polygraph device detects deception in the examinee by analyzing their physiological response to the examiner’s questions. The “Fight-or-Flight” (FoF) response is a nervous system reaction to a stressful environment your brain perceives as a threat.

When the FoF activates, it increases blood pressure, pulse, respiration rate, sweat gland activity, and skin electrical response. That’s why you feel like your heart beats out of your chest when you feel scared. Your hair stands up on your neck, and you get goosebumps.

Essentially, your body is priming your physiology to either run away or stand your ground and fight, the “fight-or-flight” reaction. When we lie in a polygraph exam, the brain and nervous system activate the FoF, and that reaction shows up on the examiner’s software on their laptop.

The examiner interprets this response as “deception,” meaning that you’re trying to hide something from them with your response. They’ll repeat the question and see if it makes any difference to your response. If the examiner thinks you’re just nervous, they ask why you feel this way and why it could show that you’re acting deceptively.


5 Things that Contaminate Polygraph Exam Results

So, what causes contamination of polygraph exam results? The machine is highly accurate but not infallible. The following can cause false positives or direct failure of the lie detector test.


#1 Failure to Prepare for the Exam

When your employer notifies you of their intention to polygraph you, you have the right to prepare yourself for the exam. Many people think they can’t research the lie detector test’s specifics and how it works because it might get them in trouble. However, that’s not the case. In fact, the polygraph examiner prefers it if you take the time to research the test.

When we enter an unknown environment, such as a polygraph exam room, it affects our subconscious, conscious mind, and nervous system. As mentioned, the brain signals the Autonomic Nervous System (ANS) and Sympathetic Nervous System (SNS) to prepare the fight-or-flight (FoF) response to launch when we feel threatened.

Preparing for the exam by researching how it works and what to expect helps you deal with the event’s uncertainty. It puts your mind at ease, making it less likely that you’ll feel nervous to the extent when the FoF is primed and ready to fly into action for an irrelevant reason.

When you enter the exam room to take the lie detector test, the examiner will introduce themselves to you. It’s their job to make you feel at ease with the test. Don’t see them as your enemy. They’ll ask you if you have any concerns about taking the test and answer any questions you have relating to the process and the questions they’ll ask during the exam.

Take the opportunity to air your concerns and ask questions, no matter how silly they seem. You’ll find this exercise dramatically lowers your pre-exam stress and the tension in your body and mind. As a result, the polygraph won’t make any false recognitions of deception that contaminate the test results.


#2 Poor Sleep

Finding out you have to undergo a polygraph exam is a stressful experience. Many people struggle with sleeping the night before the lie detector test. They have thoughts about what might happen to them if they fail if the examiner asks them about stuff in their personal life they might be trying to hide or things they’ve done in the past that might come up in the test.

They toss and turn all night and don’t manage to get much sleep. Being tired at the lie detector test isn’t a good frame of mind. Our brain clears neural pathways of waste when we sleep. If you don’t get adequate sleep the night before the test, you’ll wake up feeling like you have “brain fog.”

When we’re tired, the primal part of our brain responsible for our survival assumes we’re in a disadvantaged state. In essence, it believes it has to be extra careful about our behavior because we might not be alert enough to respond to environmental threats.

As a result, it places the sympathetic nervous system on high alert, priming the fight-or-flight mechanism to respond to any assumed threat around us. So, when you enter the polygraph exam room, your mind is ready to leap into action, even though you might not realize it. If an examiner asks you a question that makes you feel uncertain, it might accidentally activate the FoF, contaminating the test results.


#3 Using Sleep Medication and Drinking too Much Caffeine

Since it’s common for people not to get a good night’s sleep, they might decide to take friends’ or parents’ sleep medication to help them get some rest. Drugs like Ambien and other “Z-drugs” designed to help you fall asleep are powerful medications, as are sleep supplements like melatonin.

If you’re not used to taking them, one of the side effects is that they’ll make you feel groggy the following day. As a result, the brain and nervous system go through the same processes as if you didn’t get enough sleep, priming the SNS and FoF.

Worse still, you’ll likely compensate by drinking more coffee or an energy drink during the morning to help clear the brain fog. Caffeine is a potent nervous system stimulant. Drinking more coffee than normal overstimulates the CNS, making you feel jittery and anxious.

As a result, it primes the SNS and the FoF. The stress of being questioned might initiate the FoF response, contaminating the test results. Suppose you use a friend’s prescribed sleep medication. Technically, you’re misusing the drug, which might affect your exam results if the examiner asks you if you misuse prescription medications, creating a false positive on the polygraph exam.


#4 Use of Countermeasures

While it’s perfectly fine to research the polygraph exam, you might be curious if you see a post online about how to beat the polygraph and read it. “Countermeasures” are strategies implemented before or during the polygraph exam to help you suppress the FoF response and “beat” the polygraph.

There are several countermeasures used by people in lie detector tests, usually by those that have something to hide. Examples would be biting your tongue, clenching your leg muscles, or thinking bad thoughts when the examiner asks a question, and you must lie to conceal something.

These tactics and many others, such as attempting to control your breathing, are blatant attempts to deceive the polygraph and examiner. The bad news is the polygraph software, and the examiner detects if you’re using countermeasures during the exam.

Most countermeasure tactics come from the era before software, and computerized systems entered polygraph technology. Modern lie detectors are so sensitive that they can detect these tactics, and the examiner will ask u if you’re using them. If they discover you’re implementing a countermeasure, you fail the test immediately.

Even the act of reading up about countermeasures is enough to contaminate the test results and cause you to fail. It’s common for polygraph examiners to ask if you researched these tactics before you take the test.


#5 Using Anti-Anxiety Medication

Anti-anxiety medication is one of the more common countermeasures used in polygraph examinations. Drugs like beta-blockers and Xanax help people with anxiety manage their condition. They have a potent effect on the nervous system, eliminating the physiological triggers responsible for initiating the onset of a panic attack in patients.

So, some individuals assume that by taking Xanax before the test, the effects of the medication suppress the SNS and its ability to launch the FoF response. As a result, they have a chance of the examiner avoiding their deception during the test.

However, while Xanax effectively suppresses the FoF, it can’t do it completely, and the examiner will still notice a mild response to their questions. Examiners have the training to detect people using these drug-based countermeasures, and they’ll figure out you’re using these medications in an attempt to fool them.

Like the other countermeasures, the examiner takes the use of these medications seriously, and they’ll fail you. Xanax is also a prescription medication and one of America’s most highly abused and misused drugs. So, if the examiner asks you a question like, “have you used illegal drugs or misused or abused prescription drugs in the last 18 months, you’ll have to lie about that too.


Pathological Lying and Polygraph Contamination

Another reason, albeit rare, that might contaminate the polygraph results is if the examinee is a pathological liar. Pathological liars view telling lies differently from other people. They lie frequently and don’t experience any shame, guilt, or remorse for their deceit.

The pathological liar’s brain has a different wiring than everybody else. They don’t experience the same interaction between the frontal lobes and the amygdala that creates sensations of guilt or shame. As a result, their nervous system doesn’t activate the fight-or-flight response when they lie.

Since the SNS doesn’t launch the FoF response, the polygraph cannot detect any change in their physiological response to the examiner’s questions. Pathological liars are different from compulsive liars. Compulsive liars know they’re lying, but pathological liars often believe the lies they tell.

So, pathological liars are possibly the only people capable of avoiding detection during a polygraph exam. However, less than 5% of the US population lies pathologically. As a result, there’s a minimal chance of a pathological liar ending up in the exam room.


Can My Employer Fire me for Failing the Polygraph Exam?

No. Your employer can’t fire you for failing a polygraph exam. Doing so would violate the “Employee Polygraph Protection Act of 1988” (EPPA). The EPPA legislation protects employees from employer abuse of polygraph policies in the workplace.

If you fail, your employer can’t fire you, they can’t force you to leave, and they may not intimidate you into leaving the company. If they make your work experience difficult or fire you anyway, you have legal recourse against them.

You can hire an attorney, and they’ll file a complaint against your employer with the US Labor Department. The Labor Department investigates the case, and they impose financial penalties on the employer if they find them violating the EPPA.


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