It is true that the polygraph machine can detect psychological responses to a series of questions. The test basically focuses on three indicators of what is known as autonomic arousal. Respiration, skin conductivity, blood pressure/heart rate are the three indicators that the lie detector test is designed around. How these indicators are measured will be described more in depth below. It is important to note that examiners cannot measure psychophysiological changes just by monitoring the individual’s behavior. However, it is possible to suspect deception, if the individual attempts to alter the test by refusing to sit still throughout the exam.

Pretest Interview

Everyone who agrees to undergo a lie detector test will be required to attend a pretest interview. During the interview, the examiner will explain what the lie detector test is, how it works and its purposes. Also, the examiner will go over the type of questions utilized for the testing. The questions will always have a “yes” or “no” answer. It is also not unusual for the examiner to go over the questions that will be utilized for the scheduled test.


The process of air moving in and out of the lungs is breathing. This process is controlled by the autonomic nervous system. While breathing is done unconsciously, the individual can also control it. Breathing is a necessity to sustain life and it can react differently to certain situations. For instance, if someone is in fear of something, the respirations will increase drastically.

It is also true that when someone is trying to be deceptive that his or her respirations will increase. This is why the lie detector test utilizes this particular indicator to determine if someone is being truthful or deceptive. The test utilizes what is known as a pneumograph to measure the depth and rate of respiration. If you are not familiar with this component, you want to conduct a brief search on the topic. It is crucial to learn as much about the machine and test as possible to improve your chances of achieving an accurate and favorable result.

The examiner will wrap the pneumograph about the individual’s chest, before the exam begins. The respiration responses will appear on the lie detector machine, along with the heart rate, and skin conductivity.

Blood Pressure

The blood pressure is measured through a sphygmomanometer or better known as a blood pressure meter. This device attaches to the individual’s arm through an adjustable and inflatable cuff. The meter will continuously measure the individual’s blood pressure constantly throughout the testing process. The examiner will note any variations in the blood pressure level. In most cases, when an individual is trying to be deceptive, their blood pressure level will increase.

During the preview interview, the examiner will collect a blood pressure level, so he will have something to base his results on. The accuracy of the test results will depend on each step of the process being completed properly and the individual being tested knowing how to react to each question.

Skin Conductivity

When it comes down to it, the lie detector test is capable of analyzing numerous indices. Nevertheless, there are some that tend to be more important than others. For most participants, the skin conductivity tends to be one of the most important attributes of all. This specific statistic is designed to determine the patient’s electrodermal activity. This is sometimes referred to as EDA. The electrodermal activity is a specific attribute that causes variations in the electrical makeup of the skin.

The EDA tends to vary based on the participant’s sweat glands and their current behavior. Simultaneously, sweating is impacted greatly by the sympathetic nervous system. By taking this into consideration, the lie detector test is capable of determining whether or not someone is being deceptive based on their skin conductivity. It is believed that EDA is capable of measuring the activity of the autonomic nervous system. When this system is more active, there is a good possibility that the individual in question is nervous or anxious.

This could be a good sign that they’re lying about something. This is why skin conductivity is so vital to the modern lie detector test.

Patient’s Pulse

The polygraph test is capable of analyzing the patient’s psychological profile in numerous ways. The participant’s pulse undeniably makes up a large portion of their profile. As you probably already realize, the pulse is capable of telling you how hard your heat is beating at any given time. It is possible to acquire an accurate pulse reading through numerous manners. The patient’s neck, wrist, and even the elbow can be a good way to determine what their pulse is at any given time. However, when it comes to the polygraph test, a blood pressure cuff is used.

Believe it or not, specific pulse patterns can tell you a great deal about a person and their current status. If the pulse is erratic, there is a possibility that the patient is suffering from heart failure or even aortic valve diseases. On the other hand, the pulse can be utilized by polygraph administrators. When they detect abnormal fluctuations in the pulse, they’re able to determine that the participant may very well be lying.

This is why the pulse is so vital to the polygraph test. Without it, the test itself would not be accurate and psychological profiling would be impossible. When combined with the other psychological profiling factors, it is possible for the polygraph test to determine whether or not the participant is being truthful or deceptive at any point in time.

Unique Psychological Reaction

Each person in the world is unique. This is why polygraph testing needs to be precise and it must be carried out by someone with the skills necessary to get the right results. If the administrator is not skilled, there is a possibility that they’ll acquire results that are neither reliable or truthful. Why is this so vital? Just recently, a psychologist and polygraph researcher explained that there was no unique physiological reaction to deception. What does this mean exactly? Well, each participant can have a different reaction to deception.

Some people will experience an elevated pulse and more respiration. Other people may not when they’re lying. This is why it is vital for the administrator to be experience. They must be able to establish a psychological profile for each individualistic patient. Once they’ve found a base to start with, they’ll have a much easier time trying to determine whether or not someone is lying.

Before the questions are asked, the administrator should take note of the participant’s vital signs. Then, they’ll be able to use this information to determine when the participant experiences anxiousness and nervousness. In return, this can help to identify deception.