Can polygraph results be quantified?

Polygraph results, at least as of the last time I took one, are wiggle traces described by galvanic skin response (i.e., conductivity as modulated by sweat), heart rate and whatever else their e-meters can measure.

What would it take to scientifically quantify these results?

I’m a geophysicist and I spend much of my time looking at, and interpreting, wiggle trace data. That’s all earth data, and subsequent drilling confirms or condemns my interpretations. I’m not at all convinced that polygraph operators can return meaningful results related to whether or not a tested individual is being truthful based on polygraph results.

We spend much time on comparing our geophysically based wiggle trace data to real world results, and I have some feel for that. I don’t feel that polygraphs have been really tested, and I’m asking now if there might be some manner in which they might.

Good, because you shouldn’t be.

They certainly can “quantify” the results, but Astrologers can also “quantify” their “results”. :dubious:

IMHO a “good” polygraph operator decides whether or not you are lying based upon mostly various intangibles he observes, adding his “squiggles” then telling you that the “machine says you are lying”. Then since experienced investigators are quite good at determining truth (with or without a polygraph), many dudes collapse and confess, since “the machine can’t be wrong”. :rolleyes:

However, many dudes who claim they are alien abductees can and do “pass” polygraph exams, and since I hope we all know that they have NOT been “abducted by aliens”- “the machine” is hardly infallible.

Let me go on to say that Polygraph operators (and any expereinced investigator) are pretty good at noting the rather clear “signs of guilt” most of humankind show. Where the problems lies are:

  1. Some few dudes truely believe something that isn’t really true. Thus, they will appear to be truthful

  2. Some even rarer dudes are sociopaths and have no guilt for their crimes. Thus, again, they won’t show signs of guilt even if guilty.

  3. The signs are rather “in the eyes of the beholder” and even a great investigator can convince himself he is seeing signs of guilt where there are none, especially when said investigator is personally convinced of your guilt to start out with.

  4. The most common is where you didn’t really commit the crime, but “feel guilty about it”. A Parent may be questioned about their child’s death- that parent will often feel “it’s their fault” (for letting the child go unsupervised, or the parent may thing they weren’t “being a good mother”), and thus will exhibit signs of guilt, even those not guilty of the crime. This is why polygraphs are a BAD thing, as you can get a dude who have convinced himself he is responsible (even though he commited no crime) and then the Polygraph operator sez “the machine says you are lying- confess, you’ll feel better” and then yes, the dudes will confess, and yes he’ll feel better. Then he’ll be convicted for a crime he never commited.

Perhaps one day lie-detectors will pass the junk-science-detector test. At the moment they’re failing miserably.

I appreciate the comments, and I’ll note that I’m hardly a fan of polygraphs. I’d previously read the skepdic entry that duality72 linked, as well as many other reports on polygraphs.

What I was wondering was whether or not any serious emperical studies had been done to establish the validity of polygraph tests.

I’m wondering if it will ever be possible to conclusively detect deceit in a person, as in James Halperin’s fascinating novel The Truth Machine. There should be a recognizable brain pattern associated with deceit, wouldn’t you think?

Rocks are rocks and people are people. No one vigorously interrogates rocks. Rocks don’t get nervous. The Washington Post is hardly a scientific journal, but it notes that even the CIA and NSA cannot agree what the basic ground rules are. You’re hardly likely to get any meningful raw data, let alone any sort of conclusions.

Apparently not, at least nothing that’s been found. There’s just no particular pattern that can be found in pet scans and the like that’s associated with lying.

(No cite to hand; I believe I picked this up in one of the textbooks in my intro to cognitive science class.)

Maybe we’ll find something as resolution gets better, perhaps?

Which reminds me of something else … what about all those supposed tricks that people talk about, like watching if your eyes move left or right while you speak, where one indicates creative thought, i.e. lying, and the other indicates accessing memory, i.e. truthfulness? Is there any validity to that sort of thing?

And how about that relatively new “brain fingerprinting” thing where they show you something and can supposedly tell if you’ve actually experienced it before?

I know you’re looking for more empirical responses, Ringo, but I’ve got a personal anecdote that’s relevant. I work for a government agency (via contract) and underwent a polygraph. In the post-polygraph interview (aka, the “I Know You’re Lying, Now Confess” phase), I was told that I demonstrated deception in regard to my account of drug use and handling of Classified materials. Thing is, I’ve never, nor would I ever, mishandle Classified or Sensitive material. Furthermore, my drug history is absolutely clean.

The polygrapher at one point said, “you see this spike? That’s like a finger pointing to God telling me that you’re lying.” My response (which didn’t include the fact that I’m an agnostic and am further skeptical that line graphs have fingers with any desire to point at a deity) was “you’re the one who knows how to read that. I see spike all over the place. But if it’s calling me a liar, I’m calling it a liar.”

As to the drug question, I pretty much ended the conversation with “Listen, you’re not gonna’ beat a confession out of me here.” For the Classified materials thing, I said, “First off, any information that comes in could endanger my coworkers if it got out, so I wouldn’t do that.” He came back with, “Come on, maybe you were out at a bar and wanted to impress a girl or something?” At that point I laughed and pointed out that if I were trying to impress a girl, the last thing I’d want to do would be to tell her that I work where I do and then bore her with mostly technical data.

The interview ended with him saying, “I’ve got to send the data to HQ. There’s a good chance that they’re going to want you to come in for another polygraph.” Then, as he was escorting me out of the building through the elevator, he half-mumbled, “you know you passed, right?”

It probably helped that we both knew that we shared a mutual friend. . .

At the end of the day, the polygraph is useful for forcing confessions when the polygrapher already knows the answers.