# Stop the Lies! **URL:** \ **Category:** Great Debates\ **Created:** [May 29, 2000, 5:12am UTC](https://boards.straightdope.com/t/stop-the-lies/20783 "2000-05-29T05:12:42Z")\ **Posts on this page:** 5\ **Page:** 4
**Author:** ![JonF](https://avatars.discourse-cdn.com/v4/letter/j/cab0a1/32.png) [@JonF](https://boards.straightdope.com/u/JonF)\ **Post date:** [June 7, 2000, 9:14pm UTC](https://boards.straightdope.com/t/stop-the-lies/20783/61 "2000-06-07T21:14:54Z")
> [@](#): > > The purpose of my examples was to show that “data” and “evidence” are two very different things. I agree that they _can_ be different things. I don’t see how they difer _in this particular situation._ You have several times claimed that no evidence has been posted, and my quotes refuted your assertion. OK, data and evidence are different. What is the relevance to your claims that no evidence has been provided? > [@](#): > > How you can look at a survey of scientists of what they think on a particular subject and not consider it hearsay is beyond me. Seeing as how not a single person quoted mentioned anything that they personally had done, it is safe to say that, as it currently stands, all of the “evidence” was hearsay. Sigh. I’m beginning to think that many things are beyond you. The survey is not hearsay, unless you have a different definition of hearsay than the American Heritage Dictionary {“Information heard from another”). The survey is a **direct** measurement of _what those scientists think_. It is certainly _different_ from evidence collected by testing subjects in a lab with a polygraph, and we should **not** conclude that the survey proves the inefficacy of the polygraph _because a bunch of prominent scientists think so_. The survey does prove that _a bunch of prominent scientists that are not obviously out of their field think the polygraph is useless_ and it is reasonable to conclude that these scientists _may_ know whereof they speak, even that a large portion of them _probably_ know whereof they speak, and the survey is _indicative_ evidence relative to the efficacy of the polygraph. If someone posted “JonF told me that there was a survey of scientists …” then _that_ would be hearsay. > [@](#): > > I have already pointed out that if the links truly do contain evidence, it would be more convincing if that evidence were actually quoted, rather than simply declared to exist. And I have already responded that there is too much evidence to reasonably quote in this forum. And that some of the evidence has been quoted. I’ll stop going over the same ground when you stop making the same ludicrous and whining claims. > [@](#): > > What is at issue is not whether the polygraph has acceptable effectiveness, but whether it has any at all. No. From the OP: "1. Am I missing something?! Is there any scientific evidence to support using a polygraph as a device to ascertain truthfulness? 1. Should a business and/or the government be allowed to use the polygraph to screen potential employees or investigate existing employees?" There are two issues. You have chosen to focus on one. > [@](#): > > I do not understand why your disagreement on one issue has led you to oppose me on the other. Actually, I don’t necessarily disagree with you on the other. I believe I disagree with you, but I’m willing to change my mind. My recent posts have been dedicated to correcting your misinformation and misunderstandings about the nature of evidence and data, and what has or has not beeen provided. Please _quit whining_ and _post some freakin’ evidence in favor of your argument_. ---
**Author:** ![The\_Ryan](https://avatars.discourse-cdn.com/v4/letter/t/7feea3/32.png) [@The\_Ryan](https://boards.straightdope.com/u/The_Ryan)\ **Post date:** [June 8, 2000, 12:46am UTC](https://boards.straightdope.com/t/stop-the-lies/20783/62 "2000-06-08T00:46:35Z")
> [@](#): > > I agree that they _can_ be different things. I don’t see how they difer _in this particular situation._ Data is information. Evidence is information that supports a claim. > [@](#): > > OK, data and evidence are different. What is the relevance to your claims that no evidence has been provided? The relevance is that although data has been provided, no evidence has been provided. > [@](#): > > we should **not** conclude that the survey proves the inefficacy of the polygraph _because a bunch of prominent scientists think so_. The survey does prove that _a bunch of prominent scientists that are not obviously out of their field think the polygraph is useless_ The survey _is_ valid evidence for the claim “scientists don’t trust the polygraph”. However, it was not presented in that context. It was presented **as evidence that the polygraph is ineffective**. In this context, it **is** hearsay. Come on. How about actaully thinking about this. Suppose you were trying to prove that someone had commited a bank robbery. Do really think that a survey of people as to whether they think the defendent did or not would be admissable as evidence that he had committed the robbery? Of course not. Be reasonable. > [@](#): > > And I have already responded that there is too much evidence to reasonably quote in this forum. Well then, quote at least _some_ of it. ] > [@](#): > > And that some of the evidence has been quoted. No, it hasn’t. > [@](#): > > I’ll stop going over the same ground when you stop making the same ludicrous and whining claims. Let’s see: You’ve said that I didn’t answer one of your questions, when I clearly did. You have mischarecterized my position. You’ve said that evidence has been quoted when none has been. You have said that what clearly is hearsay isn’t hearsay. etc., etc. And yet you accuse me of making ludicrous claims. My claims are not ludicrous, and the only reason that I have repeated them is because you refuse to see the truth in them. If you are going to claim that evidence has been posted, I don’t think that it’s too much to ask that you give at least one example. Come on. Just one. What’s so hard about that? A survey is not evidence. Half of a study is not evidence. > [@](#): > > > [@](#): > > > > What is at issue is not whether the polygraph has acceptable effectiveness, but whether it has any at all. > > No. From the OP: > > “1. Am I missing something?! Is there any scientific evidence to support using a polygraph as a device to ascertain truthfulness? > 2. Should a business and/or the government be allowed to use the polygraph to screen potential employees or investigate existing employees?” Would you mind paying attention? You presented the data on false positives **as evidence against my claim regarding the first question**. You claimed that it was evidence regarding **the first question**. Therefore, the second question was not at issue. Your claiming that it supported your view with regard to the the second question is a complete non sequitor. I agree that you have presented evidence supporting your view on the second question. I do not agree that you have presented regarding the first question. ---
**Author:** ![JonF](https://avatars.discourse-cdn.com/v4/letter/j/cab0a1/32.png) [@JonF](https://boards.straightdope.com/u/JonF)\ **Post date:** [June 8, 2000, 11:36am UTC](https://boards.straightdope.com/t/stop-the-lies/20783/63 "2000-06-08T11:36:41Z")
Ok, finally I get it … and I should have gotten it earlier. You’re ignoring question 1 and focusing on question 2, while the majority of the posters are ignoring question 2 and focusing on question 1. I apologize for missing this point. However, I can’t resist pointing out that, if you had _posted some evidence to support your assertion_ as was requested many times, I think I would have gotten it much sooner. It is certainly interesting and relevant whether there is a positive correlation between lying and polygraph measurments. I think that the question of whether the polygraph is a valid tool is much broader and more important. I do not dispute that average polygraph scores are consistently better than chance. Contrary to your assertion, there is evidence regarding this in the posted links. It took me about three minutes to find it. Some of that time was spent finding the links in the thread. It took me about two minutes to edit out the line breaks so it looks reasonable in a quote. You probably could have found it in 2-3 minutes from the original post, had you invested the effort; and you would have has the links to the tables right in front of you. From [Scientific Validity of Polygraph Testing: A Research Review and Evaluation - Review and Analysis of Polygraph Field Studies](http://www.fas.org/sgp/othergov/polygraph/ota/field.html): "… data from the available field studies were analyzed to ascertain whether polygraph examination accurately differentiate deceptive suspects from nondeceptive subjects. For this analysis, the outcome frequencies for each category were converted to percentages, and average percentages within each category were calculated. A measure of predictive association (lambda, see 64,73) was also calculated, although the use of a single measure is very limited due to the wide variability in study design. The lambda(b) index shows the proportional reduction in the probability of error in predicting one category (in this case, deception) when a second category (in this case, polygraph examination results) is known. If the information about the second category does not reduce the probability of error in predicting the first category at all, the index is zero, and one can say that there is no predictive association. On the other hand, if the index is 1.00, no error is made in predicting one category from another, and there is complete predictive association. Essentially, lambda provides an index that translates to the percent improvement over the base rate and indicates the percent improvement in prediction when the polygraph examinations are considered versus no further information. There is almost no direct research on the percent improvement of the polygraph over other forms of investigation (cf. 207). The results of this analysis of predictive association are shown in tables 4 and 5. The average lambda~ across studies is 0.65, which means that, on the average in these field studies, the polygraph diagnosis reduced 65 percent of the error of chance prediction. The lambda(b) for individual studies ranged from 0.13 to 0.90. To summarize, the analysis of the 10 field studies included in the analysis indicates that while polygraph examinations using CQT in criminal investigations detect deceptiveness and nondeceptiveness better than chance, there is also what in some cases might be considered a high error rate, particularly for nondeceptive subjects. The one study which tested the validity of the relevant/ irrelevant question technique (the general question test (GQT) portion of the Bersh study) also detected deceptiveness and nondeceptiveness better than chance. Variation Among Studies As implied in the introduction to this section, the use of a single statistic or summary number to describe the results of field tests of validity may be misleading. As shown in table 3, although the field studies of polygraph validity are similar in that almost all of them tested control question techniques in criminal investigations, they differ in operationalizations of ground truth and type of examiner decision. The result is that there is a great deal of variability in the results of studies. Correct guilty detections range from 70.6 percent in one condition of the Bersh study to 98.6 percent in a condition of the Wicklander and Hunter study. Correct innocent detections are even more variable, ranging from a low of 12.5 percent in the Barland and Raskin judicial outcome study to a high of 94.1 percent in one condition of the Bersh study. Table 5 also indicates the range of incorrect judgments and inconclusive among studies. False negatives range from 29.4 percent of the Bersh study to zero percent. False positives range from 75 percent in Barland and Raskin (22) to zero percent in two studies. Inconclusive range from zero to 25 percent. This section compares studies that used comparable operationalizations of construct and criterion validity in an attempt to discover reasons for the range of results. However, even using this method results in considerable variability." I hoipe you realize that, although the tables are online, it’s against board rules to link directly to them OK, question 2 is put to bed. Let’s move on to what interests me and, I suspect, interests any others who may still be reading this thread. Care to discuss whether the polygraph is accurate enough to be useful as a tool in _any_ employment decsisions? ---
**Author:** ![douglips](https://avatars.discourse-cdn.com/v4/letter/d/e68b1a/32.png) [@douglips](https://boards.straightdope.com/u/douglips)\ **Post date:** [June 8, 2000, 9:19pm UTC](https://boards.straightdope.com/t/stop-the-lies/20783/64 "2000-06-08T21:19:18Z")
It is important to note that the standard for the polygraph is not a coin flip, thus a ‘barely over 50%’ rating cannot necessarily be compared to the 50% a coin would give. The true standard is how much better is a polygraph than a non-polygraph method such as an experienced investigator - “Your eyes are shifty. You are lying. Tell me what really happened.” “You just said movie - a while ago you said a baseball game. Which is it?” A polygraph is administered by a human who is watching the subject’s reaction and noting it, if mentally or even subconsciously, so it is entirely conceivable that this is the equivalent of dowsing or cold reading. I’d be interested if there was a test of polygraphs in which the analyst is not present but merely has after the test access to a typed transcript overlayed on the polygraph tape - could he say “Here is a lie” just based on the squiggles, or is he using psychology to figure out the lie when he is present during the test? All things considered, I do not see a reason to suspect that polygraphs work other than as a placebo, such as a dowser or that ‘people finder’ weirdo thing that came out a while back. ---
**Author:** ![Stratocaster](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/stratocaster/32/16393_2.png) [@Stratocaster](https://boards.straightdope.com/u/Stratocaster)\ **Post date:** [June 10, 2000, 12:26am UTC](https://boards.straightdope.com/t/stop-the-lies/20783/65 "2000-06-10T00:26:10Z")
I am greatly disappointed if this is the end of this and JonF and The Ryan are not going to resort to pistols at sunrise. [Previous page](https://boards.straightdope.com/t/stop-the-lies/20783.md?page=3)