Are you going for a polygraph exam soon? You’re probably wondering what the experience will bring. Undertaking a lie detector test can be a harrowing experience if you don’t know what to expect. When you understand the procedure of the polygraph exam, the types of questions, and the instrumentation used, it takes away a lot of the stress involved.

As humans, we fear the unknown. The unknown can make us do silly things, which is also part of why the polygraph exam is so effective at detecting deception. Despite what you may have heard, a lie detector is an advanced piece of equipment that’s effective t determining if someone is lying. Don’t let other people try to convince you otherwise.

Some people may find the experience of enduring a polygraph intimidating, and that’s understandable. We’ve all seen enough Hollywood movies involving polygraphs to get a basic understanding of what it’s about. There’s a significant difference between what you see in films and TV to what goes down in the polygraph exam room.

This post will look at the type of polygraph instrumentation used in the exam and what to expect from your first lie detector test.


What Is a Lie Detector Test?

A lie detector test is a slang term for a “polygraph exam.” Polygraphs are sophisticated technology developed over the last 150 years to detect “deception” in people. The first iteration of the lie detector machine arrived in the late 1800s, receiving improvement over the next 40 years until John Larson and Leonard Keeler perfected the device in the 1920s.

Keeler went on to advance Larson’s designs and came up with the benchmark standard for the device in the 1950s. Other people like John Reid made advancements in the questioning techniques used in the exam room, and in the 1990s, we saw the introduction of computerized systems into polygraph technology.

Software, AI, complex algorithms, and computer technology changed the game. Test results became more accurate and more widely accepted by law enforcement and businesses in the private sector.

In the 1980s, a study showed lie detectors to be inaccurate, with variability in results. According to the survey, the polygraph was only right 60% to 70% of the time. As a result of the study, the government signed the “Employee Polygraph Protection Act of 1988” into power.

The Act expressly forbids the use of polygraph exams in the private sector, except under certain exclusions. Despite the advancement in polygraph technology in the last 40 years, the Act remains in place.


How Does a Lie Detector Test Work?

The polygraph exam monitors the subject’s vital signs during the testing session. History shows that we experience physiological changes in the body when we lie. These changes become more pronounced in controlled sessions, such as criminal interrogations or private-sector inquiries.

Sitting in a high-pressure environment where we know we have to lie to cover something up affects physiological elements like blood pressure, skin electrical impulses and sweating, heart rate, and respiration. We also tend to move around because we feel uncomfortable.

The polygraph machine detects these changes in our physiological state, recording them through a software program. A trained and qualified examiner monitors these changes. If they notice your physiological state going beyond normal function, it’s a sign you’re lying.

We can’t control these changes in our bodily state. They’re “autonomic” processes like breathing and blinking. This means you don’t have to apply conscious thought to these processes. The body does them on autopilot.

Regarding the lie detector, an increase in stress in a controlled environment, such as the polygraph exam room, causes a reaction in the “Sympathetic Nervous System” (SNS). When the SNS detects you’re feeling stressed. It signals a gland in the brain called the hypothalamus to release cortisol and adrenaline into the bloodstream.

These biochemicals trigger the “fight-or-flight” response in the body. If you ever woke up in the middle of the night as a kid and thought someone was under your bed, you know what this reaction is. The fight-or-flight response causes you to feel fear. Your senses are on edge, your heart is beating out of your chest, and your breathing quickens.

Lying under a polygraph exam causes the same reaction. The SNS activates the fight-or-flight response when you lie to cover something up. The examiner picks up this response on the polygraph equipment, indicating you’re being deceptive with your answer.


What are the Instruments Used in Polygraph Exams?

When entering the polygraph exam room, the examiner will introduce themselves and run you through a quick breakdown of the equipment they use to monitor your response to their questions. You’ll sit in a high-backed chair, and the examiner will wire you up using the following equipment.


Physiological Sensors

The polygraph examiner uses a range of physiological sensors to pick up changes in the body during the exam. You can expect them to use the following equipment.


Breathing/Respiration Rate

The examiner straps two corrugated rubber tubes to your torso. One goes around the chest, and the other goes around the waist. These tubes detect your breathing rate. When we lie under stress, our respiration rate increases. These tubes notice this movement, expanding and contracting with the rise and fall in your chest and abdomen.


Blood Pressure

The examiner attaches a blood pressure cuff to your upper left arm. You’ve probably had a doctor place one of these cuffs on your arm the last time you went to them for a physical examination. The cuff measures changes in your blood pressure. When we lie under stress, we experience a rise in blood pressure.


Sweat Gland Activity

The examiner will place two sensor pads on your fingers or palms to detect changes in sweat gland activity. When we lie in stressful environments, we start to sweat. The body releases a different chemical in this sweat than you get from exercising. The pads detect moisture and the chemicals in sweat.



Some polygraph examiners require you to sit on a pad on the chair’s seat. The pad detects movement. When we lie under stress, we tend to unconsciously shift around nervously. This pad detects that movement and looks for countermeasures like clenching your sphincter when answering a question. Spoiler alert: that countermeasure doesn’t work, and the polygraph examiner will pick it up immediately.



The examiner attaches a sensor to your fingertip to measure your circulation. As we lie under stress, it changes our oxygen exchange rate and circulation.


Understanding Polygraph Software

The polygraph sensors connect to a unit that feeds into a laptop. The laptop runs sophisticated software analyzing the signals sent by the polygraph instrumentation strapped to the examinee. The first versions of polygraph software were released in the late 1990s, but they were a shadow of the current technology.

You might remember the first iterations of cellphone models in the late 1990s. Compare those phones to the modern smartphone device, and you’ll get an understanding of the advancements in computer technology and software over the last two decades.

The modern polygraph software runs AI and highly refined programs designed by masterful engineers to detect deception. The software analyzes the biofeedback created by the physiological changes in your body as you answer questions during the lie detector test.

Several companies manufacture versions of polygraph software, but all of them are highly advanced. During the exam, the polygraph examiner stares at the screen and asks you questions. You’ll be facing away from the examiner, and they’ll be looking directly at the screen and the feedback from the software while questioning you.


Recording the Session – Cameras

The examiner also records the polygraph session using an HD video camera. They’ll focus on your upper legs to your face. However, the examiner likely won’t look at you during the exam. They’ll be staring at the screen.

They use the video recorder to collect visual recordings of your body language during the questioning process. They’ll record it and review it later. The examiner has access to the footage and may only divulge the exam results to your employer or prospective employer. They may not show them the software process or video recording.


The Role of the Examiner in a Lie Detector Test

The examiner is the most important piece of equipment in the polygraph exam. The examiner is a highly trained individual and an expert in spotting deceptive behavior in people. They use a specific questioning technique to form a baseline of your physiological response under pressure.

At the start of the exam, they usually ask you two to four questions to get an idea of what your stress response looks like on the software. After they’re confident they know what to look for, they start with the proper exam questions.

The polygraph questioning technique is a byproduct of nearly a century of refinement. The master of this technique was a gentleman named John E. Reid. Reid developed an effective questioning process used in law enforcement interrogations, but there is controversy surrounding it and the results it produces.

Reid once had a man convicted for a crime he committed because he pressured him to confess during a polygraph exam. Despite this controversy, the FBI admitted to using Reid’s interrogation technique in polygraph exams as recently as 2013.

However, the Reid Technique doesn’t feature in the questioning process for private-sector polygraph exams for candidates and employees. It’s more likely that the examiner will use “The Control Question Technique.” The examiner will run through questions during the exam, with the following examples being common questions.

  • Have you ever lied to your employer?
  • Have you ever stolen from an employer?
  • Have you used illegal drugs or misused prescription medications in the last six months?  

If you answer yes to any of these questions, the examiner will ask you to expand on your answer. For instance, if you answer yes to lying to your employer, you could tell them you lied when you were late to work last month, telling your boss you had a flat tire when you really slept in late.

It’s important to note that the examiner isn’t looking for lies in most cases, especially in pre-employment screening. For instance, J Edgar Hoover, the head of the CIA in the 80s and 90s, famously admitted he sympathized with communists while taking a polygraph test. Despite admitting to this, he still found himself employed by the CIA.

The moral of that story is that the polygraph examiner is looking for deception. They understand people do all types of crazy things, but the important thing is that you admit to it, not lie about it.


Post Polygraph Exam Analysis

After completing your polygraph exam, the examiner thanks you for your time and removes the instrumentation from your body. They won’t tell you if you passed the polygraph, even if you ask them. Your employer will give you your results, typically 24 to 72 hours after completing the test.

The reason for the delay in results is due to the examiner analyzing the recorded results of your session. If there were points during your exam where they suspect deception, they’ll review the video footage and look for signs of lying in your body language, gestures, and facial microexpressions.


In Closing – Can You Beat a Polygraph Exam?

No. You can’t beat the polygraph. You would need complete control over your emotions and autonomic nervous system controlling the SNS and the fight-or-flight response. Think about when you get scared. Can you turn off the fear in an instant? Or does it take you a few minutes to calm yourself?

It’s the same thing in the polygraph exam. When you’re sitting in the exam room, the SNS automatically primes the fight-or-flight response. As soon as the examiner asks a question and you know you have to lie to conceal something, the SNS sets the fight-or-flight response into action, releasing a flood of cortisol and adrenaline into your bloodstream.

As the fight-or-flight response releases these chemicals, you feel a surge of adrenaline, like an electric shock running through your body. That’s all it takes for the examiner to note your reaction. You’re done. You fail the polygraph.

Don’t believe the hype. While some people claim they beat the polygraph, the chances are you won’t.

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