Thanks for the clarification, Marty. I had mistakenly inferred from your earlier post (reply #4) that you were suggesting that a good polygrapher does something differently with truthful examinees during the pre-test phase than with deceptive examinees, which I now see was not the case.

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I thought it was clear in my reply. This is the whole rationale behind stressing the scientific nature of the polygraph. Assuming the examinee can be con'ed into believing that the polygraph actually responds to some lie specific physiological reaction the instrument measures then he will be more nervous if he intends to lie on the relevant and less nervous if he doesn't as he will trust in the "infallibility" of the polygraph.

The real guesswork is in the selection of controls. And if the examiner guesses wrong, God help the examinee.

We've covered elsewhere the case of informed examinees.

[added]
As for MD's administering placebos, I wasn't comparing the ethical similarities so much as pointing out the similar psychology. There is no serious dispute that the CQT is more reliable (I said more, not highly) if the examinee is uninformed as to it's purpose. I also am inclined to believe the majority of polygraphers try to do the best they can but to openly discuss the polygraphs limitations would diminish what effectiveness it has, much the same would apply to discussing placebos in front of terminal patients.

-Marty

Marty,

A "good" polygrapher may well do what you've described, but that doesn't really answer the question I asked, which was, "How does the good polygrapher know whether the examinee is deceptive or not before trying to alleviate stress to the relevant and maximizing the response to the control questions?"

There is also an important distinction to be made between the doctor administering a placebo to a patient with an otherwise untreatable ailment and a polygrapher attempting to psychologically "condition" a polygraph subject during the pre-test phase. The doctor is a medical expert working for the benefit of the patient, and his placebo will at least do no harm. The polygrapher, by contrast, is a quack working for the benefit of whoever is paying him, and his ministrations may be "lethal" (figuratively speaking).

As for polygraphers polygraphing other polygraphers, it's little more than a charade necessary for perpetuating the myth of the polygraph.

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A "good" polygrapher emphasizes that the polygraph is "scientific" and detects "lies", rather than stress. She also emphasizes that people who did (control Q subject) are the kind of people that the agency doesn't want to hire (for screenings).

This is not too removed from effective prescribing of placebos. A good bedside manner and projecting confidence in the "treatment" can be quite effective. Fully informing the patient on the true nature of the sugar pills would likely produce less effective results.

This is the problem. If people really deeply understand what the polygraph actually does, it is likely the guilty will respond less while the innocent examinee will respond more to the relevants.  Which brings up the perennial question, how does a polgrapher polygraph another polygrapher? I suspect a wink and a nod

-Marty

Marty,

You write:

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But how does the good polygrapher know whether the examinee is deceptive or not before trying to alleviate stress to the relevant and maximizing the response to the control questions?

However "good" the polygrapher may be, and however scrupulously he may follow the procedures he has been taught, he cannot make up for CQT polygraphy's lack of scientifc underpinnings.

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Agreed, and that is why polygraphers try their damnedest to create or re-inforce the belief that the there is some sort of special response to lying per se. A good polygrapher (and I believe there are variations amongst them) will try to allevieate stress relative to the relevant (assuming the examinee is not deceptive) while maximizing the response to the controls much like you described in "NE"'s case.

[sorry about the typo's but I don't have my glasses and my typing sucks]

-Marty

Marty,

The probable-lie CQT is biased not only against those who are completely truthful, but also against just about everyone to the extent that the "control" questions do not provide adequate control. Typically, it is fairly obvious that the consquences of not being believed with regard to the relevant questions (which are often about go-to-jail crimes) are more serious than the consequences of not being believed with regard to the "control" questions (which are typically about common human failings).

"Control" questions are indeed "rated" in the sense that they reactions to them are given a numerical score. But the key to passing is to show larger reactions to the "control" questions than to the relevant questions. For a much fuller explanation of how polygraph tests are administered and scored, see Chapter 3 of The Lie Behind the Lie Detector.

Minor admissions to the "control" questions shouldn't hurt, for example, calling in sick once when you might have been well enough to come to work. Major admissions, however, (for example, falsifying a travel voucher) might well be disqualifying.

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Part of the "art" of polygraphy is the selection of "control" questions. This is a major portion of the pretest interview.  Good polygraphers will attempt to select control questions that you will lie on and feel quilty and fear discovery about more than on the relevant questions. If they select bad controls that you do not lie about, then you are likely to respond more to the relevant ones simply out of fear and become one of the false positive statistics.

In some cases, for instance the Westerfield murder case, BI provided control question information (physical abuse) that gave a definitive known lie comparison. In most cases screening exams can only provide probable lie controls. Hence it is fact that the PLCQT is biased against those rare persons who are completely truthful.

-Marty

Are control questions rated?  For example,  have you ever lied to your supervisor...  If a person  say yes or no.  Do it hurt the outcome of the test??