What a polygraph is and how it works — in simple terms
A polygraph is a computerised hardware system that measures a person’s physiological reactions while they answer questions. It is also called a lie detector, although it would be more accurate to say: a device that records changes in the body when a person tells the truth or lies.
A polygraph does not “read minds” and does not “see the truth directly”. It records the body’s reactions, which change at moments of psychological tension.
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🔍 Which reactions a polygraph measures
During testing, the polygraph records several key indicators:
• Breathing
Two sensors on the chest and abdomen record the depth, rate and rhythm of breathing.
• Cardiovascular activity
A cuff on the arm measures changes in pulse and blood pressure.
• Galvanic skin response (sweating)
Two sensors on the fingers record the slightest changes in sweating.
• Motor reactions
A special sensor pad detects micro-movements of the body.
The greater the psychological tension, the clearer the reactions.
🧠 Why the body reacts to lying
When a person tells a lie, several processes are triggered automatically:
tension in the nervous system
a faster pulse
a change in breathing rhythm
activation of the sweat glands
micro-movements of the body
Even if a person looks calm on the outside, their body gives off micro-signals that cannot be controlled consciously.
These are exactly the changes a polygraph records.
📝 How a polygraph test is carried out
The test consists of several stages:
1. Preliminary consultation
The specialist clarifies the situation, prepares the questions and explains every stage.
2. Briefing
The person is told how the equipment works and is asked some practice questions.
3. Running the test
The questions are asked in a set order, and the device records the reactions.
4. Software analysis
Special software analyses the charts and compares the reactions to different types of questions.
5. Conclusion
The polygraph examiner explains the results and answers all your questions.
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Andriy Maryniak, polygraph examiner since 2012 · 6,000+ tests
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🎯 Can you beat a polygraph?
There is no reliable way.
People do try, but an experienced polygraph examiner usually sees it.
The reasons:
all reactions are assessed together, as a whole
it is impossible to control breathing, pulse and sweating at the same time
the software analyses all channels at once
attempts to influence the result usually show up on the charts
A professional polygraph examiner usually notices when a person:
holds their breath
tries to tense their muscles
diverts their attention
changes the rhythm of their answers
The modern polygraph is a precise scientific method.
⚖️ How accurate is a polygraph?
Modern techniques and software analysis deliver an accuracy of:
85–89%
These are the figures of the American Polygraph Association meta-analysis (2011): 89% for a single specific incident, 85% for multi-issue screening.
That is why the polygraph is widely used:
in business
in family matters
in staff screening
in internal investigations
when theft is suspected
in cases of infidelity
in legal disputes
🧩 The difference between a polygraph and EyeDetect / StimulTest
The polygraph is about physiology.
EyeDetect is neurotechnology (analysis of eye movements).
StimulTest is the brain’s cognitive response to a stimulus, captured through motor activity.
Each method provides valuable information, and combined they give maximum accuracy.
🟦 Conclusion
The polygraph is a modern tool that makes it possible to establish the truth objectively where words no longer work.
It does not “read minds”, but it accurately records the body’s reactions.
In the hands of a professional, it is one of the most reliable ways to resolve a conflict situation.
👉 More about the author: Andriy Maryniak — polygraph examiner in Lviv
👉 Professional polygraph tests in Lviv: lie detector test in Lviv
👉 Innovative EyeDetect technology: EyeDetect in Ukraine
This article was written by Andriy Maryniak, a polygraph examiner certified since 2012.
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