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How to know when someone is lying?
Transcript of How to know when someone is lying?
How the ancient chinese did it?
They used rice. They made the supposed lier two questions. 1st one. “Your name is Chang?” (They already knew his name). “Yes,” was the answer. The interrogators gave him a handful of rice and he had to put it in his mouth and hold it for 3 seconds, then he had to spit it out. Then they made him another question: “Did you steal the chicken?”, “No”.
He had to do the same with another handful of rice. Interrogators knew the exact rice grains that came in and came out. They knew if he was lying if the number of rice grains that came out was more than the ones that came in, because when we are stressed the mouth is drier so fewer grains stick, so more come out. Mr. Chang stole the chicken.
Cheaper and faster than a polygraph, the VSA (voice stress analyser) is based on the idea that our voice changes when we are under stress-when we are lying for example. It works also on a phone, a tape or a microphone; now you can even buy the “Truth Phone” to know if someone who rings is “working late” at the office or not.
The period of time between the last word of the investigator’s question and the 1st word of the subject’s response is known as “response latency”. The avarage response latency for who is telling truth is 0,5 seconds. So if someone takes 1,5 seconds to answer is probably laying or highly suspicious.
According to researchers in the USA, when someone lies you get an inmediate warming around the eyes, known as blushing.
Why? Because blood goes to the eyes so that the lier can find out an “escape route”. A heat-sensing camera can detect such blushness, the new technology could offer a a new tool for security screening at places like airports, office buildings and hospitals, for instance.
Modern lie detectors
Modern lie detectors, know as polygraphs, rely on the same basic principle: that lying causes body changes, which can be detected and measured. The suspect is connected to 3 devices, that measure blood pressure, breathing rate and electrodermal response (when lying blood preassure increases, our breath is faster and we sweat). Increased activity suggests stress which means the subject may be lying.
So if we know how to control our body changes, when we are lying, we won’t be caught!