can a lie detector actually tell when someone's lying or is a lie detector full of lies hey everyone I'm Lacy Green welcome back to D news for as long as people have been able to lie to each other we've been coming up with ways to catch the liar one of our more glamorous attempts is a polygraph test or a lie detector it's the machine you sometimes see in movies with the little needles scribbling the little lines the original lie detector was invented in 1921 by a police officer in none other than my hometown of Berkeley
California at the time information was sought out by using something called third degree interrogation it was apparently legal I don't know how to deprive people of food and water to isolate them beat them with hoses and otherwise hurt them to get information so long as the interrogation didn't leave marks on their body the officer wanted an alternative to the widespread brutality and he also wanted a way to make the cops obey the law themselves and so the so-called lie detector was born in 1921 it detected changes in blood pressure and in 2013 it measures blood
pressure breathing heart rate and whether or not you're sweating but from the day it was born these machines have been hotly debated in law politics and of course science over 80 peer-reviewed studies of the light detector tests have been done and most of them have found that well yes hate to break it to you but with a 30 % error rate it doesn't exactly detect lies blood pressure heart rate sweating these are physiological responses that can be triggered by things like fear embarrassment or anger three emotions that may come up when someone is in high
stress situation of being interrogated the measures do sometimes correlate with actual lies but it depends on who's in the hot seat and who's doing the interrogating from a scientific standpoint it's an interrogation technique not a science that's why famous serial killers like Gary Bridgeway can pass a polygraph test while another innocent suspect who was also tested failed it ouch George moshki a Former Intelligence officer for the Army says that the polygraph tests can easily be beaten and not just by crazy serial killers or sociopaths but by any old person the secret is an understanding how
the test works so you can identify the control questions and thusly augment your reactions to them people also use anything from sedatives to tongue biting to antiperspirant on their fingertips to fool the machine now if you're a chronic liar don't worry you probably won't be taking one of these anyway for the most part lie detectors are considered insufficient evidence in court but they're still used by intelligence agencies prosecutors and law enforcement agencies at least for now thanks for joining me guys don't forget to subscribe to catch more D news twice a day every day and
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