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    The Pseudoscience Of Lie Detectors
    By Gerhard Adam | October 30th 2012 04:00 PM | 18 comments | Print | E-mail | Track Comments
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    It seems that one continuously hears about individuals passing or failing the lie detector, and despite many questions regarding its veracity, people still assume that there is a scientific basis for its use.

    However, lie detection, or polygraphy is not based on science.  In fact it isn't based on much of anything, except psychological manipulation of the subject under the guise that taking the lie detector may cause them to confess, because they believe it is based on science.

    In short ... it's voodoo psychology.

    The first problem is in what the polygraph, or lie detector actually measures.  The lie detector measures blood pressure, heart rate, respiration, and galvanic skin response or skin conductivity.  Therefore the first scientific problem that must be addressed is what the correlation with these physiological measurements has to do with deception.  It seems clear that the objective is to measure anxiety, but this presupposes that individuals become anxious for the same reasons and under the same circumstances.  Since there is no context for these measurements by themselves, the thinking is that by asking some control questions, a kind of baseline can be established against which deception can be measured.

    However, the problem with that, is that it presumes that individuals react in a predictable manner with specific traits associated with deception.  In other words, the underlying "theory" is that physiological reactions will occur because of "guilty knowledge" in whatever is being investigated.

    This brings us to another problem with the polygraph and that's the definition of deception.  In this case we are looking at a specific psychological condition in which the subject must keep two entirely separate but plausible scenarios in their mind during the interrogation.  One must reflect the "truth" while the other is the "lie" or the story that is intended to deceive the interrogator.  Of course, this renders the polygraph totally inappropriate in those situations where an individual believes what they are saying.  So, in instances of UFO witnesses or witnesses to paranormal phenomenon, the use of the polygraph is completely irrelevant unless the sole purpose is to establish whether the subject is simply making up the story.  Truth is entirely subjective and the subject that believes what they are saying is not being deceptive regardless of how wrong their information may be.

    Despite some of the obvious difficulties with such assumptions, there has been no scientific testing that establishes that such a correlation exists, let alone exists consistently enough to be interpreted as being deceptive.  People may be anxious because they are lying, but they may also become anxious because they are afraid the examiner thinks they are lying.  Instead of "guilty knowledge", they may experience a guilty reaction over an unrelated event.  More importantly, it fails to consider the issue of a psychopath that may not have any anxiety over their crimes and therefore escape detection.  Essentially the entire premise on which lie detection is built consists of a variety of assumptions which have never been demonstrated to be valid.

    Presumably some of these difficulties can be overcome because of the expertise of the examiner.  Not really.

    Here is a link to a checklist for finding a qualified examiner.  

    Apparently the requirements to become a polygraph examiner are somewhat vague.  Despite the claim that such an examination is a psychology test, there is no requirement that one be a psychologist, or even have a psychology degree.
    "Polygraph examiners often have experience in law enforcement or investigations, but a background in psychology or behavioral science is also beneficial. Polygraphists work in the public and private sector, and many are employed by local, state and Federal government agencies."
    http://education-portal.com/articles/Become_a_Polygraph_Examiner_Education_and_Career_Roadmap.html
    It would appear that the actual training for becoming a polygraph examiner involves approximately 380 hours (about 9.5 weeks) of training at an accredited Polygraph school.

    Claims of accuracy abound, but generally this is promoted by polygraph examiners, so it is a bit of a biased perspective.  Even if we were to accept an accuracy rating of 92% to 98%, this means that of 100 suspects, 2 to 8 would return bogus results.  While the actual guilty party might be in this group, it doesn't bode well for the innocent individuals that will have been accused as well. 

    Equally well-known is the case of Gary Ridgway [aka, the Green River Killer] who took and passed a polygraph test in 1984.  As a direct result of this "passing", the DNA results taken from him in 1987 were not analyzed until years later, ultimately leading to his arrest in 2001.  The polygraph had allowed a serial killer to go free for an additional 17 years because of an improper result.
    "What this research tells us is that if a polygraph exam is done properly, by a skilled and experienced examiner, using the best methodologies, techniques and equipment, accuracy can be as high as 96%."
    http://polygraphreality.wordpress.com/category/research/
    "OTA concluded that the available research evidence does not establish the scientific validity of the polygraph test for personnel security screening. OTA was able to identify only four studies directly relevant to personnel security screening use (one by DOD). None of these studies specifically assessed validity of polygraph testing for the purposes proposed by DOD or the administration, and all had serious limitations in study design."
    http://www.fas.org/sgp/othergov/polygraph/ota/summary.html
    Psychologists have repeatedly told U.S. courts that polygraph tests--popularly thought to reveal a person's truthfulness through assessment of physiological states--are theoretically unsound and not valid in assessing honesty.
    http://www.apa.org/monitor/julaug04/polygraph.aspx
    Yet, what is the basis for assessing such a high degree of accuracy?  Interestingly, it is based almost exclusively on the "confession criteria".  In other words, an individual that fails the polygraph is further interrogated, ultimately leading to a confession.  This is used as one of the primary basis for establishing that the lie detector was accurate.
    "Because polygraphers seldom discover ground truth except as a consequence of post-test confessions, and because diagnoses evaluated in this way are almost invariably verified as correct, the typical experienced examiner will accumulate a personal record of almost unblemished accuracy (p. 202)."
    http://www.fbi.gov/about-us/lab/forensic-science-communications/fsc/july2002/index.htm/krapohl.htm
    Under these circumstances, the criterion (the confession) and the test outcome (deception indicated) are not independent. The method thus virtually guarantees that the two will match, ensuring 100% “accuracy.”
    http://www.sciencedirect.com/science/article/pii/S0031938408001947
    " It is noted that the validity of polygraph testing has yet to be established. The present review suggests serious problems with both the theoretical rationale underlying use of polygraph tests and the quality of available evidence supporting the validity of such tests."
    http://psycnet.apa.org/journals/amp/40/3/355/

    "Most of the respondents believed that polygraphic lie detection is not theoretically sound, claims of high validity for these procedures cannot be sustained, the lie test can be beaten by easily learned countermeasures, and polygraph test results should not be admitted into evidence in courts of law."
    http://psycnet.apa.org/journals/apl/82/3/426/
    Polygraph is fundamentally an abuse of science, because it is based, at least in part, on the ignorance of the populace in eliciting a confession because they believe it has scientific merit.  This is not a game, but a technology that has the potential to destroy an innocent person's life, while letting the guilty go free.  The notion that some degree of accuracy is all that is necessary to achieve an objective is essentially an argument that it is valid to destroy people's lives in an effort to apprehend the guilty.  Yet, we see that the guilty may just as readily escape such detection, so even this rationalization fails.

    Whether anyone likes it or not, the human mind is complex and the simplistic notions that truth and deception are simply binary is the height of psychological naivete.  An individual may be lying, but we can't determine about what.  We can't determine the motivation, nor even whether the lie is relevant.  We may also have the response of individuals that feel guilty at the mere mentioning of various acts, so that they fail the polygraph despite being innocent.

    This is an area that law enforcement, security personnel, and many businesses would love to have a crystal ball to manage, but using faulty science to achieve such an objective is not the vehicle.  For those under scrutiny, while it may be tempting to volunteer for a polygraph to establish one's innocence, it is equally important to remember what the consequences could be from a wrongful accusation.  The problem is that the innocent invariably believe that they will prevail.  This is also a lie.
    -------------------------------------------------------------------------------------
    Additional references:
    http://www.psychologytoday.com/blog/the-skeptical-psychologist/200907/the-polygraph-test-strikes-and-strikes-out-again

    http://www.bps.org.uk/sites/default/files/documents/polygraphic_deception_detection_-_a_review_of_the_current_scientific_status_and_fields_of_application.pdf

    For an alternative view of deception detection, the work of Paul Ekman provides some interesting reading.
    http://face-and-emotion.com/dataface/facets/deception.jsp

    Comments

    lumidek
    Penn and Teller dedicated one episode of their excellent Bullshit show - season 7 episode 5 or so - to the bullshit of lie detectors. Unfortunately I can't find the full show now on YouTube but most of it is here:
    http://www.youtube.com/watch?v=TD6ecO5UOR0


    It also says how to fool the lie detector etc.
    Gerhard Adam
    Thanks for adding the link [this is the full episode].  This is definitely a technology we need to put behind us and move on.
    Mundus vult decipi
    Thor Russell
    I must watch more of that show. Someone definitely needed to bring up lie detectors on a science site, well done to Gerhard. 
    Thor Russell
    Gerhard Adam
    Thanks for the good words.
    Mundus vult decipi
    Generally I agree with your statements about polygraphs. Many years ago I was used as a test subject in a school where they taught polygraph examination. The student examiner, who was close to graduation, and the instructor both had a hard time reading my results. Eventually, they got a fairly accurate reading of the straight lies I was instructed to tell. Afterward, the instructor told me to never take a lie detector test, that almost all examiners would misread many of my true statements as lies, or at best as being deceptive. In over 20 years of investigations I have used a combination of verbal analysis and body language quite successfully as indicators of deception.  Primarily I use verbal analysis. This same method is now being taught to FBI agents. Recent scientific research indicates that the use of the two methods together can provide reliable results approximately 80% of the time. 
    UvaE
    From the checklist link you provided:
    Scientific research has shown that the UZCT is the most accurate of all testing techniques. 
    "Scientific research" has shown...as opposed to "unscientific research" has shown? Sounds too much like a commercial! I was skeptical of lie detectors even in high school, but maybe I was biased by the fact that in our science fair, the project that was getting a lot more attention than mine was a lie detector. :)
    Bravo! Polygraphy is the kind of thing I tend to be wary of just by my nature, but if your assessment is sound then it's a travesty on a level I wasn't aware of. (Sorry I don't have the time to investigate right now) but considering the prevelence of it's use (especially in the public sector) and (as you mentioned) the magnitude of consequences involved here, I find it flabergasting that these practices still want for exaustive study and validation.

    On the same wavelength, I've always had seroius, serious concerns about law enforcement's use of drug sniffing canines. Even IF an individual dog, much less EVERY one, could be satisfactorily shown to be a reliable indicator for said substance, (which I'm miles from taking on faith), the ambiguity surrounding the signalling and the chasm of opportunities for undue influence, expection bias, and outright abuse is significant (to say the least). At least polygraph testing produces SOME hard data in the form of the phsiological measurements along with audio/video recording of the proceedings. A lot of times drug-sniffing doesn't leave a record that could be independently analyzed, even in principle!

    It might not be quite as bad as if the IRS audited people using that famous "Number-Adding Horse," but there is a little bit of a smilar feel in some cases I've heard about. =) This topic came to mind immediately when I read the above because, just this morning, NPR had a segment highlighting the concerns and controversy surrounding the use of these tools vis-a-vis the 4th Ammendent, and reported that the Supreme Court has agreed to hear a case involving the issue.

    I have anxiety problems and my heart rate tends to go up under questioning just because I'm being questioned. In one case I became very anxious under oath (in front of a judge) because I knew that when I get anxious, I look like an idiot. I was especially nervous this time because this was really important to me - I wanted very much to be believed. Here's the funny part: in this particular case, I had proof in my hand - documentation that proved I wasn't lying.

    I know my anxiety was mindless and groundless. After years of working on it, I am better at controlling it. But the point is this: anxiety is not evenly distributed, and it's certainly not distributed according to guilt. If anything, it's the other way around, as people with higher anxiety levels are more afraid of breaking rules than smooth liars are.

    Gerhard Adam
    Yes, that's exactly the point. 

    This is something that is specifically raised in Paul Ekman's work on detecting deception through micro-expressions, etc.  The point he continuously makes is that until we establish what is normal behavior for a person, we can't possibly know what represents an exception.  Even once all that criteria has been satisfied, we may conclude that the individual is being deceptive, but we can't possibly know what they're being deceptive about, whether it is relevant to our query, or whether our questioning triggered other unrelated responses.

    Mundus vult decipi
    Gerhard, you say:
    "Polygraph is fundamentally an abuse of science, because it is based, at least in part, on the ignorance of the populace in eliciting a confession because they believe it has scientific merit".

    But isn't that exactly the strength of the polygraph? And isn't that why we could use it (ie, eliciting a confession)?
    Is that an abuse of science, or is it simply a sneaky trick that exploits a scientifically illiterate population?
    There are moral questions here, sure, but an abuse of science?

    Also, why call it voodoo psychology? Why not voodoo physiology, or voodoo criminology, or voodoo forensics, or voodoo justice? Very few psychologists actually think polygraph tests have merit as a 'lie detector'. They can be useful for other things though.

    By the way, are results from polygraph admissible in US courts?

    Gerhard Adam
    By the way, are results from polygraph admissible in US courts?
    No, they are not.
    Also, why call it voodoo psychology?
    Because the premise is to psychologically manipulate the individual.
    But isn't that exactly the strength of the polygraph? And isn't that why we could use it (ie, eliciting a confession)?  Is that an abuse of science, or is it simply a sneaky trick that exploits a scientifically illiterate population?
    Would you still consider it a "sneaky trick" if that scientifically illiterate population were jurors deciding on a conviction?  Moreover, how much of a trick is it when passing such a pseudoscientific polygraph may be a condition of employment?  How many people is it permissible to taint and have lose their jobs just to maintain the illusion?  It is rubbish and it needs to be recognized as such.

    Since the Innocence Project has used DNA evidence to exonerate 300 individuals since it started, the data compiled has suggested that 27% of those serving sentences were due to false confessions.  So, while one can argue about why someone would confess to a crime they didn't commit, the reality is that using a tool like the polygraph to force a confession is coercive no matter how you choose to rationalize it.

    As I stated, it is easy for people to presume that they would never confess, and yet if confronted with law enforcement officers and other "evidence", it isn't difficult to see how an individual [especially if they don't have money for a good attorney] may be effectively coerced into a plea bargain simply to avoid a harsher sentence if convicted in open court.
    Mundus vult decipi
    Gerhard Adam
    BTW, let me also be clear that I'm not talking about the specific behavior of individuals during an interrogation.  If they can convince someone to confess because they've wrapped Wonder Woman's golden lasso around him, then I don't have a problem with that.

    However, it is totally improper to present a non-scientific technology as if it were scientifically credible for the sole purpose of maintaining an illusion. 

    NOTE:  This isn't the only technology in forensics and law enforcement that this occurs with, so the polygraph is only one of the more blatant violations of such public trust.
    Mundus vult decipi
    But you have already admitted that polygraphs are not admissible in court, so much of your argument about sending innocent people to jail, and scientifically illiterate jurors is irrelevant. I should add here that I am also deeply opposed to lay juries for exactly that reason, but that is a whole different discussion. As a lawyer once told me, if you are innocent, you don't want a jury trial. If you are guilty, request one.

    As I said, I do think there are moral questions when using the polygraph as a way of eliciting a confession, and yes, your coercion issue is one. However, is deception necessarily an evil thing when trying to get to the truth? The 'justice' system (or rather the legal system) has a very tough time - it has to work within the judicial boundaries that are spelled out in writing. Those who commit crimes are much freer (practically, if not legally) to interpreter and circumnavigate those boundaries. As such, the perpetrator of a crime has a huge advantage.

    That said, I was unaware of the 27% due to false confessions, and if true, then that is a worry. How many of those were due to the use of polygraphs?

    The psychology behind false confessions is no doubt complex and I wonder if polygraphs add to the false confession rate, or if false confessions happen irrespective of polygraphs? That is, will an innocent person who would not confess under normal circumstances, confess under the weight of the polygraph?

    Gerhard Adam
    But you have already admitted that polygraphs are not admissible in court, so much of your argument about sending innocent people to jail, and scientifically illiterate jurors is irrelevant.
    Only within the context of the courtroom.  If there is media attention to someone taking a polygraph and failing then that can taint the jury pool.  Similarly, if failure of a polygraph causes the police and district attorney's to file charges and focus on that individual, then they may well be convicted regardless of their innocence or not, especially in circumstantial cases.

    However, as I also pointed out, there are numerous instances of where lie detectors are a condition of employment, and there's simply no getting around that particular injustice.
    However, is deception necessarily an evil thing when trying to get to the truth?
    Not necessarily, presuming that the parties initiating it recognize it as deception.  The biggest problem with this argument is that law enforcement doesn't see it as deception.  They view it as a legitimate scientific tool and therein lies the problem.

    More specifically, as outlined in the article, the case of Gary Ridgway is a classic case in point and is clear evidence that law enforcement didn't view the polygraph as a deception, but instead relied on it to the detriment of their case and to all Gary's future victims.
    That said, I was unaware of the 27% due to false confessions, and if true, then that is a worry. How many of those were due to the use of polygraphs?
    You might want to review these links:

    http://wrongfulconvictionsblog.org/2012/02/23/the-polygraph-and-false-confessions/


    http://abcnews.go.com/Primetime/story?id=1777518&page=1#.UJMdR4bIWSo
    Mundus vult decipi
    sorry, some cross-posting here, so some has already been addressed.

    Dear Gerhard Adam,

    I am a retired polygraph examiner and clinical psychologist who has run more than ten thousand polygraph examinations beginning in 1972.

    I respect anyone's opinion and doubt that my comments will change your mind in the slightest. However, I feel a need to express a few things regarding your comments about polygraph.

    First, polygraph is certainly admissible in any court if it is so stipulated by both sides. I have testified in court on many cases that used polygraph results during my career as an examiner/psychologist.

    For anyone who has no training in the polygraph technique nor any experience in administering even one test to render an opinion on the accuracy of polygraph is ludicrous. It is tantamount to giving an opinion about brain surgery without any credentials, medical training or experience at all!

    I have saved hundred of people from prosecution for crimes that they did not commit as well as help to incarcerate thousands of murderers, molesters, thieves and other criminals as well.

    I am proud of my record as a professional and I wish that people who render opinions based on psychological theories from others who are not experienced would stop, take polygraph training - get a few thousand tests under their belt and then render their opinion - then it may have some credibility

    Your opinion is nothing more than an opinion about the Bible, Gone With the Wind or anything else that you haven't read or had any experience in.

    Thanks,

    Larry M. McDaniel - A polygraph examiner with 40 years experience.

    Gerhard Adam
    Perhaps you might provide some data that demonstrates the scientific linkage between what the polygraph measures and how that relates to deception.

    Regardless of your personal record, the facts remain, that guilty parties have evaded detection and innocent people have been prosecuted.  So, while you may argue that no one is entitled to consider the science behind polygraphy unless they've personally devoted their careers to it, I beg to differ and would ask that you provide some of the scientific data you claim has been validated.

    Perhaps you'd care to comment on what the error rate was for polygraph in your experience?
    For anyone who has no training in the polygraph technique nor any experience in administering even one test to render an opinion on the accuracy of polygraph is ludicrous.
    Personally I find the arrogance of this comment beyond reckoning.  The mere fact that the polygraph can be, and has been, implicated in destroying people's careers and lives, yet you would suggest that it is beyond questioning except by other polygraphers?  I see exactly where the problem is.
    Mundus vult decipi
    Gerhard Adam
    First, polygraph is certainly admissible in any court if it is so stipulated by both sides. I have testified in court on many cases that used polygraph results during my career as an examiner/psychologist.
    "Contrary to popular belief, polygraph is not per-se inadmissible in court proceedings. Admissibility standards are different in each jurisdiction. Some jurisdictions allow polygraph evidence, either stipulated or un-stipulated, some prohibit polygraph evidence altogether, and many others allow the judge to decide admissibility on a case-by-case basis. The Daubert case is presently the standard for the admission of scientific evidence, which includes polygraph."
    http://www.capitalpolygraph.com/
    Mundus vult decipi