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Topic: Lie Detector (Read 2211 times) previous topic - next topic

wdw0003

The three main things the group wants to measure is heart rate, skin conductivity, and breathing rate.  Heart rate will be monitored using a pulse sensor.  Skin conductivity will be measured using a GSR sensor.  And, breathing rate will be measured using a thermistor.  Using these three measurements simultaneously, we are hoping to be able to consistently detect a liar with conclusive results. 

Shpaget

Is there a question you wanted to ask?

djjoshuad

perhaps he realized that he's dealing with the junk science and tomfoolery that is polygraphy, and gave up mid-post

Grumpy_Mike

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And, breathing rate will be measured using a thermistor.

How is that going to work then?

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Using these three measurements simultaneously, we are hoping to be able to consistently detect a liar with conclusive results. 

That is never going to work.

retrolefty

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Using these three measurements simultaneously, we are hoping to be able to consistently detect a liar with conclusive results.


The problem is that lie detectors don't detect lies. They just measure certain physiological responses. And as the variation among human beings is so wide and unpredictable that it's mostly just a 'security theatre' device to try and give the appearance of a scientific instrument. The results of such tests are hopelessly at the whim of the operator giving the tests. There are very good reasons that lie detector results are not admissible in court here in the U.S. (not sure of policy in other countries) trials by either the prosecution or defence because it's a flawed concept that won't hold up to true scientific proof of the results of such testing.

So good luck with your project, but be aware you are picking a project that has been discredited for decades. Technology has yet to be able to produce a true lie detector. Maybe someday they will find a method that can be proven to work, but that day has yet to arrive.

Lefty

PeterH


Using these three measurements simultaneously, we are hoping to be able to consistently detect a liar with conclusive results. 


Good for you. Personally I don't think you have a hope in hell, but you should have fun trying.
I only provide help via the forum - please do not contact me for private consultancy.

Magician

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Technology has yet to be able to produce a true lie detector.
It does, detector based on voice stress analysis. Don't get be caught, not taking seriously phone interview next time. :)  Early version from 90's  detected  8-16 Hz speech modulation.

retrolefty

#7
Feb 02, 2013, 04:44 pm Last Edit: Feb 02, 2013, 04:45 pm by retrolefty Reason: 1

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Technology has yet to be able to produce a true lie detector.
It does, detector based on voice stress analysis. Don't get be caught, not taking seriously phone interview next time. :)  Early version from 90's  detected  8-16 Hz speech modulation.



Still not admissible in court by prosecution or defence, why is that? Stress is not a lie, it's just a measurement of stress. Humans have wide variation of how much and why they might display stress in any given situation. Some people have mental illness such that they have no normal response to such testing methods.

I have read in the past that some have been experimenting with real time Cat Scanning of the brain as a lie detector method with claims of some degree of to success in 'lie detection', but not sure that it's been blessed as a fool proof method yet? Probably not a practical solution as Cat Scans require subject to be completely immobilized as any physical movement makes the data garbage. Probably would cost a fortune also.  ;)

Lefty

djjoshuad

perhaps not admittable as evidence, but still very much used in probation and other parts of the US penal system.  I have a very good friend who has his probation revoked and is in prison right now b/c of "inconclusive" polygraph tests (not failed, inconclusive).  It's sad, but true.

Shpaget

I consider polygraph to be part of scare tactics. They want you to think it's more accurate and conclusive than it really is in hopes you freak out, spill your guts and confess everything.

retrolefty


perhaps not admittable as evidence, but still very much used in probation and other parts of the US penal system.  I have a very good friend who has his probation revoked and is in prison right now b/c of "inconclusive" polygraph tests (not failed, inconclusive).  It's sad, but true.


Not surprising at all. As I said it's just security theatre and designed to instil fear and control in others, but it is not capable of detecting lies, just electrical responses. The CIA (and other three letter govt depts) use it internal on their own people as an instrument of fear and control. Of course it failed to catch several employees that did indeed sell out to the other side.

Lefty

MaJiG

I'm not sure that this thread was very kind or welcoming to the newbie that initiated it.  Have we been as hospitable as we could to someone coming here asking for help? 

Just sayin'...

djjoshuad


I'm not sure that this thread was very kind or welcoming to the newbie that initiated it.  Have we been as hospitable as we could to someone coming here asking for help? 

Just sayin'...

Well, he never actually asked for any help.  Aside from that, I think the information here is of far more actual help to this individual than any technical answers we could have provided to questions he meant to ask.  Lie detection is impossible.  He needs to know that. 

It is possible to convince someone that you can detect a lie, then measure their physiological fear responses to the threat of being caught in that lie.  The problem with that concept is that the machine has no idea if the subject is afraid of being caught, afraid of the person administering the test, afraid of saying the wrong thing and being accused of something they didn't do, or just afraid of the big hairy spider they saw crawl across the back wall.  The flip side is that if you test someone who is perfectly aware that the "lie detector" can never actually detect a lie, the test will not work because they will not be afraid.

Shpaget


-snip


Not only that, but the lie detector doesn't even detect any emotion at all. It detects physiological changes and it is up to the examiner to interpret them.
That means that the test is very subjective and prone to operator influence, error and misinterpretation.

retrolefty

#14
Feb 03, 2013, 03:24 pm Last Edit: Feb 03, 2013, 03:38 pm by retrolefty Reason: 1


-snip


Not only that, but the lie detector doesn't even detect any emotion at all. It detects physiological changes and it is up to the examiner to interpret them.
That means that the test is very subjective and prone to operator influence, error and misinterpretation.


And outright fraud as the famous TV show 60 Minutes showed in the 80s. They set up a scam where a small private company hired several (3 or 4 in N.Y. city) private commercial 'lie detector' service companies to test their employees.

They said there had been a theft at work but none of the four employees would admit anything. They also told the service 'operators' that they did strongly suspect one specific employee of the theft but couldn't 'prove it', but hoped that by giving all the employees a lie detector test the service could help them uncover the 'guilty' employee, and of course they told the operator which employee they suspected.

Of course all the employees were really actors and were told that they would earn $100 extra if they could 'convince' the lie detector operator that they were the guilty party without directly admitting guilt. Not so funny that every 'lie detector' operator came to the same conclusion that the 'suspected employee' was indeed the 'guilty' party based on their analysis of the results of their test. Of course they explained that a lie detector doesn't actual detect lies but based on their 'analysis' he was definitely giving 'evasive' answers to the questions and was the only one to show such a response and in their opinion he/she was the guilty party.

That is also the reason that some states (Calif. is one for sure) that outlaws employers from subjecting their employees to 'lie detector' testing.

Lefty

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