Are you taking a polygraph exam in the next few days? If so, you’re probably wondering how it works. The lie detector test involves two primary elements – the device and the examiner. Understanding how they operate and what they’re looking for during the test gives you an idea of what to expect, removing the pre-exam fear you have and making you feel overly nervous.

Having a better understanding of the processes involved lowers the stress you feel surrounding the test and its outcome. With this post, we aim to help you understand the behavior the examiner looks for during the lie detector test.


What are the Components of the Polygraph Machine?

The polygraph machine is a sophisticated device with many components governing its action. However, for the purpose of this post, we’re going to keep it as short as possible and focus on the primary elements driving its operation – without getting overly technical in the process.



Pneumograph – These rubber tubes strap top your chest and belly, recording changes in your breathing during the exam.

Cardiosphygmograph – The examiner attaches a blood pressure cuff to your upper right arm to monitor changes in your heart rate and blood pressure during the test.

Galvanograph – This apparatus clips to your index and ring finger, or sometimes the palms of your hands, to record changes in sweat glands and skin electrical activity.



The older polygraph models relied on a Kymograph to draw chart paper across the surface of the polygraph, with pens drawing lines representing the changes in your physiological activity. However, the introduction of software did away with the reliance on these components in the polygraph device.

Today, polygraph examiners attach the abovementioned instrumentation to a control box that hooks into their laptop or PC. The control box feeds information to a software program that interprets it, converting it to charts on the computer screen instead of drawing it on paper.

The examiner watches the charts during the test while recording the session on a video recording apparatus. They’ll review the recording at their office after the exam and compare the visual data with the charts to determine if the examinee is acting deceptively during the test.


Other Readings Captured by the Polygraph

The innovations in polygraph science keep coming. The polygraph initially started with monitoring heart rate and blood pressure before including skin electrical activity into the mix in the 1930s. However, further innovations are added to polygraph science after introducing these components.

Sweat Gland Activity

The polygraph also records sweat gland activity during the test. When we get nervous and activate the “fight-or-flight” (FoF) response, our body secretes a thin film of sweat on our skin. This sweat makes us slippery to hold on to, allowing us to escape a person or animal’s grasp.


In recent decades, polygraph manufacturers added a mat on which the examinee sits during the test. This mat records movements, such as clenching the leg muscles or the sphincter when answering questions, allowing them to see if the examinee intentionally uses countermeasures to deceive them.


Understanding Deceptive Behavior in Polygraph Sessions

So, what does the examiner look for during the polygraph exam? To understand this, we need to look at the human nervous system. Most people know the Central Nervous System (CNS) consists of the brain and spinal cord. However, we’re not interested in this part of the nervous system for the purpose of the polygraph.

When conducting the lie detector test, the polygraph examiner is only interested in activating the Fight-or-Flight (FoF) response. They monitor your physiological feedback through the instrumentation and software to assess when the body launches it.


The Fight-or-Flight Response

We’re more interested in the Peripheral Nervous System (PNS), specifically, the Autonomic Nervous System (ANS) and the Sympathetic Nervous System (SNS). The SNS drives the “Fight-or-Flight” (FoF) response when we feel fear.

It’s an autonomous process, meaning we can’t control it. For instance, you don’t have to think about moving blood through your kidneys; the body does it without your conscious input. The SNS primes the FoF reaction when we feel stressed due to being hooked up to a chair in the exam room, with the examiner asking us questions.

As soon as the examiner asks a question where you know you have to lie, it launches the FoF response out of fear. Essentially, it’s your body telling you that you need to run away from the threat presented by the examiner discovering you’re lying.

However, you can’t run away. Instead, you have to sit with a poker face, hoping the machine didn’t pick up the FoF. The problem is it’s impossible to control your physiological action. While you might be able to keep a straight face, the computer screen tells a different story.

The examiner’s charts run wild, showing a huge spike in your blood pressure, heart rate, respiration, skin electrical activity, and sweat production. They’ll interpret this data as a sign of deception and repeat the question.

If you answer and they receive a similar reading – you’re immediately under suspicion. However, the examiner won’t call you a liar; they’ll tell you the data they see on their screen and ask why you’re displaying this reaction.

In some cases, you might be overly nervous or hiding something from your past that you’re afraid to tell the examiner. For instance, you might have had a drinking problem ten years ago. While you’ve been sober for the last decade, you feel guilty about it. When the examiner asked if you have any addictions, your FoF activated out of fear, guilt, and shame relating to revealing this part about yourself.

If that’s the case, the examiner will rephrase the question. They’ll probably say something like, “do you have any addictions other than what you revealed to me now?” You’ll notice that the feeling of anxiety doesn’t appear in your answer this time, and the examiner will proceed with the lie detector test.

You see. The examiner isn’t looking to judge your behavior. They don’t care what problems you have as long as you admit it to them before or during the test. However, suppose you continue to deny that you’re hiding something. In that case, they can tell you’re doing so and register that as “deceptive.”


Body Language & Gestures

If the examiner believes you answered anything deceptively, they’ll review your exam at their offices later that day. They’ll pull up the recording of your exam and check it alongside your chart data. When we lie, it’s not only our physiological feedback that gives away our underlying thought; our body language and gestures also present our deceptive behavior to the examiner.

You might not realize it, but we leave visual clues in our behavior when we lie. A trained eye notices and analyzes this behavior, using it to point out deception. For instance, have you ever heard someone say, “look into my eyes when you tell me that?”

They say that because we tend to break eye contact and look away from a person when we lie to them. Other body language and gestures we make when lying include raising the corners of our mouths, dropping a shoulder, or fidgeting.

Suppose the examiner thinks you’re acting deceptively during the lie detector test. In that case, they examine your recording during the parts of the test where they believe you’re lying. A famous example was when the baseball player Alex Rodriguez (A-Rod) was questioned about his alleged steroid abuse.

A-Rod denied the claims, but he dropped his shoulder and turned up the corners of his mouth when making the reply. The examiner will notice this activity during their review, and they register it as you acting deceptively.


Why Don’t I Get My Results Right After Finishing the Polygraph Exam?

When you finish the exam, the examiner will thank you for attending the session and escort you out of the room. You can expect the examiner to act professionally at all times, even if they think you’re being deceptive. They understand how people behave and feel, and they don’t judge you, regardless of how you act.

The examiner always adheres to their code of ethics, and they won’t break it. Under no circumstances will they act as authority figures. If you feel you want to leave the exam room during the test, there is nothing they can do to stop you from doing so.

Don’t ask the examiner if you passed the test; they can’t give you that information, even if they know the answer. They only divulge the test results to the client that hired them, likely your boss. Suppose they need to further review your exam session. In that case, they’ll take two to three days to finalize their findings before delivering them to your boss in a report.

Your boss will notify you about your test results. They can’t disclose the information to anyone else at the company. So, your colleagues won’t know how you did, and you won’t know anything about their test results, either.


Is the Examiner’s Interpretation of Polygraph Results Accurate?

Despite the polygraph’s accuracy being up to 97% effective at uncovering deception, there’s a chance it could produce a false positive. People are naturally nervous when they enter the exam room, and heightened anxiety levels may cause the polygraph to flag you for deceptive activity when you’re only feeling anxious.

However, the examiner will likely pick up on the fact that your nerves cause the issue. They have extensive training and can determine between deceptive behavior and someone just feeling overly nervous.


Examiner Education & Training

In the overwhelming majority of cases involving failed exams, the examiner’s interpretation of results is accurate. They go through six to seven years of study and training before they can conduct a polygraph exam themselves.

They earn a four-year university degree, majoring in criminal psychology before graduating and moving on to polygraph school. The polygraph training program teaches them to use lie detector equipment and software.

After graduating, many examiners take specialist certification courses allowing them to work in specific fields of polygraph science, such as law enforcement, sexual predation, or other areas. They’ll continue their training throughout their careers, attending workshops and conferences to home their skillset and keep them up to date on the latest industry innovations.


Examiner Experience

The examiner conducts thousands of polygraph tests during their career. Suppose you’re dealing with an examiner in their mid-40s. In that case, you can bet they have extensive experience administering polygraph exams and coming to accurate conclusions. The more experience the examiner has, the harder it is to deceive them.


Mentorship & Assistance

Even if you have a younger polygraph examiner conduct your test, that doesn’t mean you have a chance of deceiving them. In most cases, inexperienced polygraph examiners receive guidance and assistance from experienced examiners during the review process at their offices.

If they need more clarification about your behavior, they’ll rely on their colleagues to assist them in reviewing your test data and the session recording. So, if you receive a failed result, you can be assured that the examiner didn’t take their decision to fail you lightly.


What Do I Do If I Think the Examiner Made a Mistake?

If you think the examiner made a mistake, there’s little you can do to appeal the process. However, if you feel that the examiner treated you unfairly, you can hire an attorney and get them to lodge a complaint with the US Labor Department. The Labor Department will appoint someone to assess your case and examine your claims’ validity.

If the investigation reveals you were treated unfairly, you have legal recourse against the polygraph examiner and our employer. Violating the EPPA comes with severe penalties, and the examiner could lose their job, and your company will have to pay a substantial financial fine.

There’s a significant difference in polygraph policies in the private and public sectors. In the private sector, your boss can’t fire or reprimand you for a failed polygraph test. However, public-sector organizations, such as the FBI or CIA, can deny your employment contract or fire you for a failed polygraph result.


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