What is the Polygraph Test Like?

What is the polygraph? This is the key question a lot of people want to know. One way of describing it is by saying:

A Polygraph is more commonly known as a Lie Detector and is a psycho-physiological detection of deception technique.

In other words – the reactions of a persons body are measured when asked certain questions about an issue that they may have reason to be untruthful about.

It usually takes between 2-3 hours and consists of three phases: the pre-test interview, the data acquisition phase (in-test) and the data analysis phase (post-test).

Pre-test interview

2 pieces of lego doing an interview

A polygraph test is like an interview

During the pre-test interview the examiner will explain how the polygraph works, comprehensively explore the issue under investigation, explain the examinees keys for success, check the subjects suitability to be examined and develop the questions to be used during the in-test phase.

The questions will be discussed in detail with you to make sure they are understood and you are happy with them.

Only those questions reviewed with the subject will be used for the in-test phase of the examination. Test question sets will be run a number of times.

What Questions can be Asked?

Understandably people want to know as much as possible about the issue under examination so will want to ask as many questions as possible.

The questions will be discussed with the all parties but it is always in the mind of the examiner to keep the questions as simple and accurate as possible.

Questions can only be asked about a physical action or event that has already occurred.

If you want to know more about how the questions are formulated, email us now for free.

In-test phase

This is the phase in which the examinee is attached to the computerised polygraph instrument. At this stage the examiner will ask those questions developed during the pre-test interview.

Questions only require a yes or no answer.

Post-test phase

Once the examiner has collected the data he will analyse the results of the entire polygraph procedure before discussing this with the examinee.

All tests and results are conducted with the strictest confidentiality. The results will only be disclosed to those people who have been approved by the paying client.

For more information on this at no cost, do not hesitate to contact us.


The Polygraph, or Lie Detector, instrument itself is a computerised system and during the procedure components are placed on the subject which measure physiological responses (associated with lying) to verbal questions.

These responses are recorded by the computer program and are then interpreted by the examiner.

What does the Polygraph Measure?

The polygraph measures your body’s responses during questioning through being attached to various components.

Pneumograph – This component is made up of two tubes, one that is placed on your upper chest and the other just on your abdomen and measures your breathing.

E.D.A – This stands for electrodermal activity. This components consists of either 2 metal plates that will be placed on your fingertips, or 2 sticky pads on your palm. These measure and record changes in your electrodermal or sweat gland activity.

Cardio Cuff – This is a simple arm cuff that is found in any doctor’s surgery and measures your relative blood pressure and pulse rate.

What if I am Nervous?

Many people worry that nerves will affect their polygraph test and that it may cause them to sweat more and their breathing to be unnatural.

Well trained polygraph examiners understand that nerves are common and part of their job is to explain to you the procedure and get to know you. Once you understand more about the test and feel comfortable with the examiner this should hopefully ease those nerves.

Will Sweat Affect me?

A man throwing water on his face for sweating

Sweating does not effect the results.

This is a very common question and the answer is no. This quote from M.I.T (Massachusetts Institute of Technology) about a device they have developed which measures the same thing sums up the point perfectly:

“highly sensitive to emotional and other significant stimuli, with a measurable response that precedes the appearance of sweat.” (talking about a Galvactivator developed at M.I.T).

Polygraph Accuracy

There are many different techniques of Polygraph examination; however, the polygraph technique we use is considered one of the most accurate at 93.9% accuracy.

This is not just a random number plucked from the sky, the American Polygraph Association conducted an in-depth review of all previous polygraph studies to establish an average accuracy for polygraph testing.

The results can be seen in APA Meta-Analysis here.

Read our blog that breaks down the complications surrounding polygraph research and accuracy here.