Author Topic: Are polygraph tests ever double blinded?  (Read 506 times)

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Offline God Bomb

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Are polygraph tests ever double blinded?
« on: May 16, 2017, 10:41:09 PM »
Lie detectors tests are junk science or semi junk depending on who you ask, but they still seem to be widely used.

 Has anyone ever done any experiments where the polygrapher is blinded after the control questions and must interpret the results from the graph without hearing the questions or responses?
It seems like this would be an easy way to determine the accuracy of tests. 
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Offline Drunken Idaho

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Re: Are polygraph tests ever double blinded?
« Reply #1 on: May 17, 2017, 12:18:30 AM »
Lie detectors tests are junk science or semi junk depending on who you ask, but they still seem to be widely used.

 Has anyone ever done any experiments where the polygrapher is blinded after the control questions and must interpret the results from the graph without hearing the questions or responses?
It seems like this would be an easy way to determine the accuracy of tests.

I dunno about that, but I got polygraphed at a job interview, and they decided that "although [they] thought I was lying about having never been a drug dealer, they were going to let me pass."

No, I've never dealt drugs, for the record.
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Offline arthwollipot

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Re: Are polygraph tests ever double blinded?
« Reply #2 on: May 17, 2017, 03:18:21 AM »
Lie detectors tests are junk science or semi junk depending on who you ask, but they still seem to be widely used.

 Has anyone ever done any experiments where the polygrapher is blinded after the control questions and must interpret the results from the graph without hearing the questions or responses?
It seems like this would be an easy way to determine the accuracy of tests.

I'm pretty sure that it would be utterly impossible to do a test under these circumstances. A wiggly line on a piece of paper is just a wiggly line on a piece of paper without the context.

Offline God Bomb

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Re: Are polygraph tests ever double blinded?
« Reply #3 on: May 17, 2017, 03:47:36 AM »
Lie detectors tests are junk science or semi junk depending on who you ask, but they still seem to be widely used.

 Has anyone ever done any experiments where the polygrapher is blinded after the control questions and must interpret the results from the graph without hearing the questions or responses?
It seems like this would be an easy way to determine the accuracy of tests.

I'm pretty sure that it would be utterly impossible to do a test under these circumstances. A wiggly line on a piece of paper is just a wiggly line on a piece of paper without the context.

Of course double blinding is difficult and in studies it's often a big challenge to figure out a way of doing it, and there are many ingenious methods researchers come up with for all kinds of tests.

One way I can imagine is if there is a transcript of the interview alongside the graph, with timestamps, and the polygrapher reviews it alone, and obviously the answers or part of the questions could be redacted, he doesn't need to know if the answer was 'yes' or 'no', he/she shouldn't even really know the question; something like "Did you murder XYZ" would probably be answered "no" so it's not truly blind.  They should only need to know the timestamp of the questions and answers to cross reference to the data.  I can't see how being in the room with the subject can do anything other than introduce massive bias and/or lead to the polygrapher using behavioural cues to determine his verdict.



I dunno about that, but I got polygraphed at a job interview, and they decided that "although [they] thought I was lying about having never been a drug dealer, they were going to let me pass."

No, I've never dealt drugs, for the record.

Did you object to the test in any way?  I'd be inclined to point out the unreliability and seek out some evidence.  Is that even an ethical business practice?
« Last Edit: May 17, 2017, 03:49:51 AM by God Bomb »
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Offline Drunken Idaho

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Re: Are polygraph tests ever double blinded?
« Reply #4 on: May 17, 2017, 04:02:11 AM »
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I dunno about that, but I got polygraphed at a job interview, and they decided that "although [they] thought I was lying about having never been a drug dealer, they were going to let me pass."

No, I've never dealt drugs, for the record.

Did you object to the test in any way?  I'd be inclined to point out the unreliability and seek out some evidence.  Is that even an ethical business practice?

I was well aware of the inaccuracy of polygraphs going into it, but I've also been such a goody-two-shoes for most of my life that I wasn't worried about it. During the test, though, I definitely got nervous. If I had to guess why, it would be due to the austerity of the exam and questioning, and the weight of the exam's outcome in proportion to the changes I'd made in my life to apply for the job.
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Offline 2397

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Re: Are polygraph tests ever double blinded?
« Reply #5 on: May 17, 2017, 05:11:45 AM »
I quit a gym over being made to sign a contract about being subject to drug tests. I don't even drink alcohol.

Which is a little a different, it's not entirely based in pseudoscience, but fuck being treated as guilty until proven innocent.

Online Harry Black

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Re: Are polygraph tests ever double blinded?
« Reply #6 on: May 17, 2017, 06:05:50 AM »
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I dunno about that, but I got polygraphed at a job interview, and they decided that "although [they] thought I was lying about having never been a drug dealer, they were going to let me pass."

No, I've never dealt drugs, for the record.

Did you object to the test in any way?  I'd be inclined to point out the unreliability and seek out some evidence.  Is that even an ethical business practice?

I was well aware of the inaccuracy of polygraphs going into it, but I've also been such a goody-two-shoes for most of my life that I wasn't worried about it. During the test, though, I definitely got nervous. If I had to guess why, it would be due to the austerity of the exam and questioning, and the weight of the exam's outcome in proportion to the changes I'd made in my life to apply for the job.
Not to mention that even IF you manage to convince the test administrator of the pointlessness of their job, you wont change the policy and so all thats likely to happen is that you will make a test prone to bias, even more biased against you.

Offline Noisy Rhysling

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Re: Are polygraph tests ever double blinded?
« Reply #7 on: May 17, 2017, 07:14:39 AM »
I convinced the polygraph operator that my version of events was the correct one. He wasn't even looking at the graph during the last  half of the "test", just looking at me and nodding.

BTW, I was guilty as hell, but I walked. Go figure.
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Online superdave

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Re: Are polygraph tests ever double blinded?
« Reply #8 on: May 17, 2017, 08:44:57 AM »
I've played with the pieces that make up a polygraph.  They simply measure how nervous you are, nothing more or less.
The Penn and Teller Bullshit episode on polygraphs is pretty devastating to the whole field.  It's basically a cold reading with the polygraph machine used as a prop.

Offline God Bomb

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Re: Are polygraph tests ever double blinded?
« Reply #9 on: May 21, 2017, 12:43:05 AM »
I've played with the pieces that make up a polygraph.  They simply measure how nervous you are, nothing more or less.
The Penn and Teller Bullshit episode on polygraphs is pretty devastating to the whole field.  It's basically a cold reading with the polygraph machine used as a prop.

Yes it seems to be fairly well known that scientifically as a tool they do not detect lies and the data they do collect is massively subject to interpretation, but from what I have heard, it's still admissible evidence in some states and some circumstances.  And I've never seen any double blind tests ever being done.  I think that would really kill the trade, so I doubt any polygraphers would agree to participate.
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Offline daniel1948

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Re: Are polygraph tests ever double blinded?
« Reply #10 on: May 21, 2017, 10:32:38 AM »
Of course the big problem is that if you are innocent you're scared as hell about being accused. If you are a career criminal you're not nervous at all because you've been through it all before. A double-blind test would have to be done using people actually accused of a crime, because volunteer test subjects know that there are no real consequences.

I think you could do a double-blind test by taking the output from real polygraph exams, then just marking where on each print-out a question was asked and where an answer was given. Then ask a number of polygraphers to rate how likely each answer was to be true. Perhaps you could tell them which were the test questions and whether the answer to each was true or false.

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Online Harry Black

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Re: Are polygraph tests ever double blinded?
« Reply #11 on: May 21, 2017, 11:31:00 AM »
If the subjects of the test have no stakes then the baseline should still be usable. I would think it only makes a difference if you mixed stakes/ no stakes samples although it could be comfounding that we dont know the effect of maybe getting punished for something you did vs the effect of maybe getting punished for something you didnt do.

A friend from my old unit offered to help me get an interview with the Vancouver PD, I declined because of the polygraph as I didnt feel like paying for a transatlantic flight and leaving the result up to chance, especially with how much the travel would probably add to the pressure.
He did note that our other former colleague did pass the polygraph despite having lied explicitly about having not committed various crimes.

Offline 2397

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Re: Are polygraph tests ever double blinded?
« Reply #12 on: May 21, 2017, 12:07:01 PM »
The Mythbusters had the basic setup for testing the validity, give the subjects rewards/punishments based on whether they can beat the machine. Throw in a bunch of controls, double blind it, etc.

Online Desert Fox

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Re: Are polygraph tests ever double blinded?
« Reply #13 on: May 21, 2017, 12:33:29 PM »
If the subjects of the test have no stakes then the baseline should still be usable. I would think it only makes a difference if you mixed stakes/ no stakes samples although it could be comfounding that we dont know the effect of maybe getting punished for something you did vs the effect of maybe getting punished for something you didnt do.

A friend from my old unit offered to help me get an interview with the Vancouver PD, I declined because of the polygraph as I didnt feel like paying for a transatlantic flight and leaving the result up to chance, especially with how much the travel would probably add to the pressure.
He did note that our other former colleague did pass the polygraph despite having lied explicitly about having not committed various crimes.

I am involved in wrongful conviction cases and often those who argue for innocence argue that the person passed a lie detector. Even if I consider the person probably innocent, I have to tell them that the polygraph has no value.
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Online Harry Black

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Re: Are polygraph tests ever double blinded?
« Reply #14 on: May 21, 2017, 01:45:24 PM »
The issue seems like a place where skeptical advocacy could actually be helpful to society.
What would have to happen for it to be disallowed for any official purposes?