Technic

How does a lie detector work?

The lie detector or polygraph was developed in the US in 1921 by a police officer and a medical student. The device measures the small, unconscious stress reactions that would indicate that you are lying.

During the interrogation, the interrogator asks a suspect questions. He already knows the answer to some of them, such as the name and social status of the suspect, so that he can see how he responds when he speaks the truth.

In other cases, the interrogator does not know the answers, but will, for example, ask what the suspect did at the crime scene.

If he then responds in the same way as before, he probably tells the truth. But if he exhibits very different behavior - for example, if his wrist rises sharply - it is an indication that the suspect is telling a lie.

Lie detector sometimes lies

The use of a lie detector is controversial because the body reactions can have a cause other than lying. For example, an innocent may feel threatened when asked at the man: "Have you shot your girlfriend?" Then the lie detector turns out, even if, according to the truth, the suspect says "No!" says.

That is why the interrogator often asks more neutral questions to find out if the suspect knew about the crime, such as: "Was the victim shot with a 9mm gun?" But the test is not very reliable.

In the US, police, security and intelligence services often use the lie detector during investigations, but few states allow it to be used during the trial itself. The detector may not be used by the government in Europe.

If you tell a lie, your body is in sharp focus, causing various involuntary responses. By measuring the reactions of a suspect during an interrogation, the police can get an impression of whether they are lying or telling the truth.

Your body doesn't lie

Heart

The pulse and blood pressure rise when you lie.

Lungs

Someone who is lying breathes faster and more superficially.

Skin

Your palms and fingertips are sweaty when you lie knowingly.

Legs

When you lie, your arms and legs start to shake slightly due to small, involuntary muscle movements.

Brain scanners become lie detectors

Various scientific studies show that the activity in the frontal lobe and the parietal lobe changes when someone consciously tells a lie.

By measuring brain activity during an interrogation you can use an fMRI brain scanner to find out whether the suspect is lying or not.

Video: The Science Behind Lie Detector Tests. How Do They Do It? (April 2020).

Popular Posts

Category Technic, Next Article

When do poland exchange places again?
Earth

When do poland exchange places again?

The earth's magnetic field regularly changes direction, but we never know when. We do know that the magnetic poles are walking. Compass measurements from the magnetic field over the past 400 years show that the magnetic Arctic in the Arctic Ocean north of Canada is shifting to 10 kilometers per year; around 1990 the pole accelerated and headed north with as much as 60 kilometers per year.
Read More
Reflected space dust creates spectacular glow in the sky
Earth

Reflected space dust creates spectacular glow in the sky

Although zodiacal light looks like a sunset, the spectacular phenomenon only comes about two hours after sunset, around 10 pm, when the twilight has disappeared. Then you see a conical haze, which is crooked on the horizon on the west. The light comes from an enormous disk of dust from, among other things, comets around the sun, which reflect sunlight back to the earth.
Read More
Due to disappearing water, geological calculations are no longer correct
Earth

Due to disappearing water, geological calculations are no longer correct

After new geological research, the water figure on earth seems to be incorrect. The water on our planet is part of various cycles, the most famous of which is between the oceans and the atmosphere. However, there is also a cycle in which water from the oceans is drawn deep into the earth's crust and mantle when the tectonic plates dive below each other.
Read More
What if the earth doesn't turn?
Earth

What if the earth doesn't turn?

The earth revolves around its own axis once every 24 hours, and that is a good thing. Because if it rotated a lot slower, it would have very unpleasant consequences for the weather, the oceans and the climate. With a slower rotation there would be a greater difference between day and night temperatures. It is difficult to say at what time the earth would become uninhabitable, but a day of about a week would certainly yield very hot days and ice-cold nights, and the tropics would then be uninhabitable.
Read More