What Does a Polygraph Machine Look for in a Liar?


Polygraph machines are sophisticated devices. This technology has come a long way since the invention of the first modern lie detector by John Larson in the 1920s. Today’s machines feature advanced software programs governed by algorithms and computerized systems.

However, the lie detector machine is just a device. It’s not like it has the ability of a human to discern if someone is lying. The polygraph relies on physiological feedback from the examinee, interpreting those signals into charts presented in front of a trained and skilled examiner.

The examiner with the training and ability to read the charts determines if the readout from the software indicates deceptive behavior. Understanding what the lie detector device and the examiner look for in dishonest behavior requires us to understand the types of lies, the differences between them, and other factors involved.


What are the Different Types of Lies & Liars?

There are different types of lies. Some are worse than others, and the behavior surrounding them impacts the liar’s environment and the people they engage with daily. Let’s look at the difference between lies and liars.

White Lies & Severe Lies

A white lie is innocent, and we all make them occasionally. It’s as simple as telling your partner they don’t look fat when you think they gained a couple of pounds in the last week or bluffing in a poker game.

Severe lies have a very different intent. In this case, we’re lying mostly for self-preservation. Some of our lies can end up getting other people in trouble or have serious consequences. For instance, you could lie about stealing $10,000 in inventory from your boss.

Compulsive Lying

There are different types of liars. You have those who occasionally choose to lie when it serves them and compulsive liars. Compulsive liars lie a lot. They do so to make themselves feel and appear more important. They may also lie several times in one engagement.

Pathological Liars

Pathological liars believe their own lies. It’s a mental health disorder affecting the brain and its development. These individuals will lie to manipulate people and avoid their implication in crimes or injustices to others. It’s a form of psychopathy, and studies prove pathological liars lack development in an area of the brain responsible for empathy and compassion.


How the Polygraph Machine Works

The polygraph machine is an expensive and advanced technology with several components.


The Equipment

The polygraph instrumentation attaches to the body of the examinee. It consists of the following components.

Corrugated Rubber Tubes – These attach to the examinee’s chest and abdomen.

Blood Pressure Cuff – Placed on the upper right or left arm.

Finger Sensors – Attaching to the three middle fingers.

Motion Pads – The examinee sits on this pad while in the chair.

The purpose of this equipment is to detect the examinee’s blood pressure, heart rate, respiration, sweat gland activity, and skin electrical activity. The instrumentation provides feedback on these physiological changes to the control box feeding to the examiner’s laptop.


The Software

A software program analyzes the feedback from the instrumentation, presenting it to the examiner in chart format. Several software manufacturing companies are involved in the research, development, and distribution of these programs to examiners worldwide. The examiner has specialized training to interpret the feedback in the software program, allowing them to accurately identify when an examinee is lying.


The Role of the Examiner

The examiner’s role in the polygraph policy is to assist the employer with creating the questionnaire for the examinee and to ensure the employer complies with “The Employee Polygraph Protection Act of 1988.”

They also have the role of assisting the examinee before and during the exam. The examiner must ensure the examinee feels comfortable around them and answer any questions they have on the polygraph process.


The Human Nervous System and the Fight-or-Flight Response

So, what does a polygraph machine look for in a liar? As mentioned, the instrumentation and software track physiological feedback produced by the examinee during the test. However, what feedback constitutes lying or deceptive behavior by the examinee?

To understand this answer, we’ll have to look at the human nervous system and what happens you our mind and body when we decide to lie.


What Is the Autonomic Nervous System?

The human body comprises the central nervous system (CNS) and the Peripheral Nervous System (PNS). The PNS is the nervous system outside your skull and spinal cord. The Autonomic Nervous System (ANS) is a component of the PNS and consists of the Parasympathetic Nervous System (PSNS) and Sympathetic Nervous System (SNS).

It regulates bodily functions like blood pressure, heart rate, digestion, respiration, and sexual arousal. These functions are autonomous, meaning you don’t have to consider them. For instance, if you don’t breathe or blink consciously, the body does that for you without any need for command, as opposed to lifting your legs or nodding your head.


What Is the Sympathetic Nervous System?

With the polygraph exam, we’re most interested in the Sympathetic nervous system (SNS). To get a bit technical, the SNS is an interconnected web of preganglionic neurons and fibers, postganglionic fibers, and the sympathetic ganglia.

The purpose of the SNS is to regulate the “Fight-or-Flight” (FoF) response in the body. When we experience a threat to our safety, the SNS primes the FoF by signaling to the brain to get the hypothalamus to produce adrenaline and cortisol, otherwise known as “the stress hormone.”

When these biochemicals enter the bloodstream, they ramp up the SNS, causing it to activate the FoF. A practical example would be when you’re walking alone at night and feel like someone’s watching or following you.

As the FoF kicks in, your pupils dilate, allowing you to bring more light to your eyes and see better in the dark. You notice your hair stands up on the back of your neck, you get goosebumps, and you seem a little sweaty. Your heart rate goes through the roof, along with your blood pressure, and you feel more alert.

That’s the FoF in action, and it’s preparing you to either run away from the threat or stand and face it – hence the name, “fight-or-Flight.” This action is autonomous, and we can’t control it. It’s a deep part of our evolution, developed by our ancestors hundreds of thousands of years ago when we were still “hunter-gatherers.”

During these times, we had little community, and small groups would go off to hunt for the tribe. We weren’t at the top of the food chain back then, and big cats would stalk us as prey. So, we evolved the FoF as a means to help us escape these life-threatening encounters with predators.

Over the millennia, we transitioned from hunter-gatherers to a civilized society, and the base need for the FoF fell away. However, as a hardwired part of our evolution, it remains intact, even today. Today, the threats we experience come mainly from other humans and some environmental factors, such as being caught in an avalanche – or taking a lie detector test.


The Lie Detector Machine and the Fight-or-Flight Response

The polygraph machine assesses the FoF response to environmental stimuli – specifically the examiner’s questions. When we’re told we have to take a polygraph, it’s a shocking experience because we don’t know what to expect from the situation – it’s the fear of the unknown.

When we don’t understand something or how it works, we will likely fear it. For instance, if you’ve never been skydiving, it might seem thrilling but scary. The first time you jump out of a plane attached to an instructor, you’ll feel terrified – that’s normal; everyone does.

The mind has a fear of the unknown, and it starts ramping up the FoF long before you leave the ground, peaking as you jump out of the aircraft. It’s the same with the lie detector test. You have a fear of the unknown and its consequences in your life. If you fail the test, you might lose your job and reputation.

So, your mind starts ramping up the SNS, and when you enter the exam room, it’s like you’re sitting on the edge of the door opening on the plane, waiting to jump. Fear is at its height, and all it takes is the examiner asking you a question where you have to lie to activate the FoF.

If this occurs, the polygraph notices these changes, sending the feedback to the software on the examiner’s laptop, and they see your response in a change on their charts. Just like that, you’re caught in a lie. Since we can’t control the SNS or FoF, it’s next to impossible to fool the polygraph or the examiner.


The Examiner & Deception Detection

The examiner spends around six to seven years in their studies and internship on the path to becoming a qualified, licensed polygraph examiner. They have extensive experience in detecting deception in others. Not only do they know how to detect deception by analyzing the polygraph software, but they can also see it in your body language.

This combination of an experienced examiner and polygraph technology effectively detects deception by analyzing the body’s reaction to the FoF response. However, it also leaves room for error. For instance, the examiner may be inexperienced and innocent, but a nervous examinee causes an FoF reaction misinterpreted as deception.

However, in most cases, the examiner can determine the difference between lying and someone just feeling nervous. This brings us to the next section on countermeasures used in the polygraph exam.


The Use of Countermeasures

Countermeasures are strategies used by the examinee to escape deception detection during the polygraph exam. Most countermeasures come from a time before the use of polygraph software, in the “Keeler” era of polygraph technology.

Keeler polygraphs, while effective, were not infallible. Some people figured out that you could interrupt the electrical impulses detected by the lie detector machine using information-based or physical countermeasures.


Information-Based Countermeasures

An information-based countermeasure describes a strategy where the examinee researches countermeasures before the lie detector test to actively discover methods to beat the lie detector exam.

For instance, they might learn that by thinking they’re telling the truth and convincing themselves that they did nothing wrong, they will likely be able to control the FoF response. OR they might research other physical or drug-based countermeasures to prepare themselves for the exam.


Physical Countermeasures

Physical countermeasures. These strategies involve tactics like curling your toes when answering questions or biting your cheek before answering. These countermeasures interrupt the FoF and lessen its impact on the body. For example, think how many people say, “I need to pinch myself so I wake up from this nightmare.”

Or they might use drugs to relax the SNS and reduce the FoF response. For instance, Xanax, the common anti-anxiety medication, lowers the stress response in the SNS. The same applies to other drugs working on similar pathways, such as beta-blockers.


What Happens If You Get Caught Using a Countermeasure?

The reality is these countermeasures don’t work. Maybe they had some success in the Keeler era of polygraph tech, but today’s modern software solutions see right through them. The examiner has extensive training in how to identify when an examinee is using a countermeasure, and they’ll ask you if you’re adopting this strategy.

If you lie, they’ll notice the effect it has on your SNS and realize what you’re up to. If you get caught using a countermeasure, it’s an instant fail on your polygraph exam. Just the act or reading up about countermeasures with the intention of using them in the test is enough to qualify you for a failed result.


Can I Beat the Polygraph Machine?

So, can you lie and beat the polygraph machine? Some individuals, like pathological liars, claim they can achieve this feat. Their mind doesn’t connect their past actions with feelings of guilt or wrongdoing. So, they don’t feel like they’re lying when they aren’t answering the examiner’s questions untruthfully.

However, less than 0.2% of the American adult population are classified as pathological liars. If you don’t fall into that category, you’ll have to control the ANS or the FoF, which requires complete mastery of your emotions. While that may be possible, it’s highly unlikely, and the chances are the polygraph and examiner will catch you being deceptive.


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