The Truth About Lie Detectors
By Christopher Wanjek, LiveScience Bad Medicine Columnistposted: 22 May 2007 08:20 am ET
Washington is a city of lies, so perhaps it is no surprise that those in the nation's capital wishing to expose the truth have been fooled by lies about a polygraph's usefulness.
According to White House spokesman Tony Snow, earlier this month, the White House will consider administering a polygraph to Clinton-era National Security Adviser Sandy Berger, who pleaded guilty to lifting documents from the National Archives in 2002 and 2003. Some say the documents, now nowhere to be found, might point to failures of the Clinton administration to uncover the 9/11 terrorist plot.
Politics aside (it was 18 Republican congressmen who wrote to Attorney General Alberto Gonzales in January requesting that Berger take a polygraph, but that was before allegations of certain falsehoods on Gonzales' part made the request a little awkward), the polygraph is no way to get to the truth.
Good liars
Good liars have little to lose and everything to gain from taking a "lie detector" test. It's the truthful people who need to worry about polygraphs.
A polygraph not a lie detector; it never was. A polygraph detects physiological expressions associated with lying in some people, such as a racing heart and sweaty fingers. The determination of truth vs. falsehood is a subjective interpretation by the polygraph examiner.
Not surprisingly, the examiner is often wrong. The anxiety associated with "oh no, they will detect that I'm lying" is rather similar to "oh no, they're going to think I'm lying when I'm not."
The polygraph is essentially a four-tier medical device that closely monitors respiratory rate, heart rate, blood pressure and electrodermal response, which is a method to detect minute changes in perspiration, usually from the fingertips. The machine is a marvel; its accuracy in detecting these physiological changes is not in question.
At the bequest of the U.S. government, the National Academy of Sciences (an organization of some of the smartest scientists in America, no lie) conducted an extensive study of the polygraph in 2002 and concluded "polygraph tests can discriminate lying from truth telling at rates well above chance, though well below perfection."
The Academy said the polygraph "rests on weak scientific underpinnings despite nearly a century of study." The high incidence of false positives-a truthful response determined erroneously to be a lie-makes the polygraph useless, the Academy said.
Just how bad?
The Academy researchers even provided a pertinent example for the Feds. Given the modern polygraph's strengths, the machine could uncover 8 out of 10 spies working at, say, a national atomic laboratory with 10,000 hypothetical employees. Sounds good, but the detection comes at the price of finding 1,600 innocent employees guilty of spying. While about 8,400 good employees would pass the test, 1,600 careers would be ruined.
Although government officials commissioned the study, they didn't like the results, so they have decided, apparently, to continue to use the polygraph in the war on terrorism. As reported by physicist Robert Park in his weekly electronic newsletter What's New, about 8,000 employees at the Los Alamos National Laboratory have been notified that they will be subjected to random polygraph tests.
Many researchers say that the standard polygraph based on blood, breathing and perspiration rates is a dead end and that the next-generation "lie detector" will involve a brain scan.
Researchers at Temple University in Philadelphia have found that certain regions of the brain seem to be implicated in lying, and these can be detected by functional magnetic resonance imaging (fMRI) scans. This research is in its very early stages, however. And such a truth-detecting device could still be flawed, for some people are so good a lying that the lies become their truths.
Christopher Wanjek is the author of the books "Bad Medicine" and "Food At Work." Got a question about Bad Medicine? Email Wanjek. If it's really bad, he just might answer it in a future column. Bad Medicine appears each Tuesday on LiveScience.
I posted a longer version of this comment on my blog WorkingatLANL.
ReplyDeleteHere is the short version.
Is a lie detector possible even in theory?
What most people seem to want a lie detector to be is an "external truth detector" which will respond when someone's statement differs from some standard of external truth.
The difficulty seems to be hidden in the words 'external truth.'
If a person is asked whether they are cheating their employer and they are taking home pens but they do not consider this cheating but a job perk, then it is not clear whether the person in answering "No, I am not cheating my employer" is lying or not.
Similarly, if a person is asked whether today is Wednesday when today is actually Tuesday but they are not thinking about the day, when they say "Yes, today is Wednesday", it would seem that from the point of view of external truth they are lying but from their own point of view they are telling the truth.
If a person is questioned about endangering national security, and they are doing someting outside the rules but, from their point of view not endangering national security, just doing what is expected of them, can they be detected as lying.
There are an endless series of related questions where the examiner and the examinee would have different views of truth and thus interpret the question and the answer differently.
So, my question is "Is an external truth detector possible, even in theory."
If it is not possible, especially for critical questions on which two different people can have different views of what is truth, then maybe security has to be maintained by other means.
Thoughts or comments?
Developing an emotional response
ReplyDeleteOne of the premises of the polygraph test is that by monitoring involuntary physiological responses to questions, the examiner can decide whether your answer is “deceptive.” One way to develop a physiological response to any question, regardless of whether it is probing or not, is to invoke your limbic system. This is the “dinosaur brain” that lives within all of us and is the source of physiological responses to events or memories.
Suppose that you could call up a memory of something terrible, fearful, or loathsome on command. It could be a memory of a horrific traffic accident, road rage, a childhood sexual abuse, or anything else that invokes the physiological response. It doesn’t even have to be a real event. You could envision (in your imagination) your polygraph examiner raping your four year old daughter and imagining the dreadful things you would do to him in revenge. The object here is to get in touch with your amygdala and trigger the physiological fight or flight response on command. No one needs to know your inner fear or your inner rage – you just need to be able to pull it up, dump the adrenalin into your bloodstream, and send your polygraph off the chart, while in no way showing any external response.
Once you can do that, you’re ready for your polygraph. Do NOT insult the examiner. Remain outwardly cool, calm, and professional. And for the innocuous questions, trigger your fight or flight response by calling up your secret memory. If he challenges your response, feign surprise: “Why I can’t imagine why your machine is acting up that way. I know I have nothing to hide.”
The anonymous post at 5/22/07 6:16 PM is describing mental countermeasures to the polygraph. A key point left out is that one should create such reactions only to the "control" questions and never to a relevant question. For more on polygraph countermeasures, see Chapter 4 of The Lie Behind the Lie Detector (1 mb PDF).
ReplyDeleteWord of warning... if your response to the control questions is unusually strong, your examiner will likely accuse you of using polygraph counter-measures. To the examiner, this will be seen as a sign that you are desperate to hide something, whether true or not.
ReplyDeleteWhat about control questions where you have no physiological response because you know that you're supposed to lie, and you're just following orders? Now your threshold is set low, and discomfort from gas will trigger a response that will be interpreted as a "lie." How is that any different from "counter measures?" Opposite effect on the machine, but both based on factors beyond the control of the examiner. Better to go with the conjured image (mine was about being raped by the examiner, which I truly felt like I was).
ReplyDelete