You’ve seen it in crime shows — the lie detector test, also called a polygraph, and it probably stirred some curiosity in you. Can it really catch people in a lie?
A lie detector test is often portrayed as a truth extractor because of its ability to make someone reveal the much-needed truth. A typical scene of a lie detector usually features someone sitting in a room with wires connected through their chest and a machine that hums. The person is then asked a series of questions.
But how does it work? Is it foolproof as it has always been depicted?
In this article, we will unravel the mystery of how this system works. From its working mechanism, you will understand why it is loved in the quest for truth.
What is a Polygraph?
A lie detector is a device designed to measure physiological responses like heart rate, blood pressure, breathing patterns, and sweat production. Data on these responses are recorded while the person is answering various questions.
The idea with a lie detector test is simple: the body doesn’t know how to lie. When someone is deceptive, involuntary stress responses can give them away. However, accurately interpreting these signals takes a skilled examiner, and that’s why you should always work with an experienced lie detector test professional for reliable results.
The history of the lie detector test dates back to 1921 when it was invented by John Augustus Larson, a medical student and police officer. The name “polygraph “ was derived from two Greek words: “poly,” which means many, and “graph,” which means writing. It tracks several parameters simultaneously, and the results are produced in the form of wavy lines which examiners are able to interpret.
How Does a Lie Detector Work?
The working mechanism of a lie detector encompasses various stages: the system setup, the questioning stage, and the analysis.
Let’s look at what happens in each of these stages:
1. Pretest Phase
The pretest interview is an important stage in the polygraph. Its main role is to get the examiner and the person being tested on the same page.
During this stage, the examiner uses this chance to elaborate on the test and the nature of questions that will be asked and gives them their options for answering (rights).
The whole idea is to make sure they understand the process and cooperate.
To succeed, the examiner must make the interviewee comfortable, increasing the chances of getting honest answers, which means accurate results.
It’s also the right time to collect valuable information on the subject matter and to gauge the impact of the questions being asked. During the interview, the examiner observes key indicators like behavior, body language, and facial expressions that affect results.
Finally, it helps the examiner develop the right questions for the polygraph: neutral (baseline), control, and relevant questions about the subject.
2. Sensor Set Up
The polygraph has to be set up before the actual test starts. That includes connecting the subject to the device using different sensors to collect data to be analyzed. Some of the key components that have to be hooked up to the subject include;
- Cardiograph Cuffs: These are blood pressure sensors that monitor blood pressure and heart rate changes.
- Pneumographs: These sensors are connected around the chest and abdomen sections of the body so that they can measure breathing rates.
- Galvanic skin response (GSR) electrodes: A galvanic skin response refers to a change in the electrical resistance of the skin due to emotional stress. It is measured using electrodes that are placed directly on the skin.
All these components are designed to work together in a coordinated way to monitor the nervous system.
3. Questioning Phase
This is the crucial part of a lie detector test system and entails asking the subject various relevant questions. It is usually done by qualified and experienced examiners who ask a series of structured questions. The most common types of questions include:
- Neutral questions: These are designed to create a baseline for normal responses. For example, “Is it raining?”
- Control questions: These are questions designed to trigger some low levels of stress response. For example,” Have you ever lied to your partner?”
- Relevant questions: These are more relevant to the subject at hand. For example, “Did you cheat on your partner?”
So, what is the essence of these questions?
Theoretically, an honest person will show signs of being strong and straight when responding to control questions. On the other hand, someone lying tends to show signs of being uneasy when responding to relevant questions that specifically touch on their lies.
4. Post Test Analysis
The analysis is the last phase of a lie detector test system’s functionality. As the subject responds to each question, the system records their physiological data. For example, heavy breathing and profuse sweating could be interpreted as discomfort. This can easily point out possible signs of deception or lies.
At this phase, the experience of examiners matters. They compare the responses to the patterns. From there, they can analyze and make conclusive interpretations. Modern lie detectors have advanced software that makes reading and interpreting data easy.
Are Lie Detectors Accurate?
You are probably wondering whether you should trust the polygraph results. Studies reveal that the accuracy of these systems ranges between 80% and 90%. The accuracy of these devices depends on several factors, and at the top of the list is the ability of the examiners to ask the right questions and make correct data analyses.
Conclusion
The polygraph is a perfect blend of psychology and physiology. It has the full power to capture every aspect of your body, especially when your mind is trying to hide something.
But a lie detector isn’t magic — it’s just a tool with strengths and limitations.
While it can’t peer into your soul, it can pick up on stress and flag potential signs of deception. Just keep in mind the results aren’t always 100% accurate.
As science and technology improve, we should expect advancements in lie detector systems. For now, though, be sure to work with seasoned examiners for more reliable results from polygraph tests.
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