'Non-Invasive Polygraph' Uses Infrared Light 77
opticsorg writes "Infrared laser pulses could soon be used to determine whether someone is telling the truth or is under stress. In patent application WO 03/057003, US firm Defense Group describes a non-invasive polygraph machine that fires infrared pulses at the subject. The reflected and scattered pulses are gathered and analysed by a receiver. 'The receiver is connected to an information processing device capable of determining various physiological characteristics exhibited by the human subject,' say the authors." Whether "various physiological characteristics" are reliable signs of truth-telling is another issue, though.
Since when were standard polygraphs invasive? (Score:4, Informative)
adj.
Polygraphs have consisted of blood-pressure monitors, pulse/respiration monitors/graphing, temperature, relative humidity/condensation on the epidermis, and as of late, retinal imaging. These are usually accomplised by a series of patches attached to the EXTERIOR of the patient's skin. No where, no how, is anything poked, prodded, or inserted.
If my invasive, you mean, less cumbersome, then sure, maybe. The patient would still have to breathe normally, and hold perfectly still (as to not alter the readings taken by the IR), which is really the only cumbersome thing about it.
Re:Since when were standard polygraphs invasive? (Score:3, Informative)
the poly i was given (it was for a gov't security clearance, and part of a larger background investigation for that clearance) consisted of a pair of sensors on two of my fingers (IIRC, index and middle; detects sweating), a pair of cords across my chest and stomach (monitors breathing), and a blood pressure wrap reader on my upper arm (blood pressure (duh) and heart rate). and you get a nice leather reclining chair to sit in. no patches slapped to my skin anywhere.
not sure how much retinal imaging would do, i was allowed to close my eyes as long as i didnt fall asleep.
they say "breathe normal," knowing full well the subject being interviewed is going to be nervous as hell, even when they are telling the truth. my breathing was more of a forced deep rhythm.
Re:Polygraph story (Score:1, Informative)
Here's how a polygraph works. You measure certain things--not one thing, but many--and watch them over time. You look for deviations, not from some presupposed idea of "normal" but rather from the subject's baseline at that given instant.
Now, we're not talking about things like heart rate and respiration here, although those are observed. We're talking about things like galvanic skin response, which basically measures how sweaty you are at a very fine level of detail. These are not things you can change with rhythmic breathing or whatever. They are beyond your conscious and autonomic nervous systems and into the realm of physiological response.
That's why a polygraph session starts with as much as a half an hour of fairly inane questions: to relax the subject and let the operator establish a baseline.
So if your world-class athlete woman came in all sweaty, nobody would care. If she took deep breaths to lower her heart rate, nobody would care.
This anecdote is, in other words, a crock of shit.
Polygraphs are a Fraud (Score:2, Informative)
Re:Polygraph story (Score:3, Informative)
How about you stop right there and go and read up a bit more. Galvanic skin responses can be ellicited by *a lot* of conciously controlled actions. If you take a sudden, strong sniff of air, for example, you'll see a really big GSR. That's an easy one. Also, btw, GSR *is* an autonomic response. If you doubt me on either of these two points, go ahead and read the recently published report on the scientific basis for the polygraphby the National Academies of Science. You can find it online [nap.edu] and read it for free.
Re:Still subjective measurements (Score:4, Informative)
Not quite. Polygraphs can be valid under the right circumstances. They are reasonably accurate when used to ask questions about specific instances. Less so when they are used in hiring decision contexts. See this recent report from the National Academy of Science [nap.edu]. There are many effective countermeasures to "fool" a polygraph. I wouldn't want my future (guilt or innocence) to depend on one, but they are pretty good at recognizing when people have unusual reactions to stimuli. How they are interpreted (e.g., is that a 'lie' or just nervousness?) is another matter.
Anyone know when this concept was first used?
The use of the polygraph as lie detector was pioneered by psychologist Dr. William Moulton Marston. He may be more familiar to Slashdotters under his pseudonym Charles Moulton. That's the name he used when he created the comic book "Wonder Woman."
Seriously!
Re:If it really worked (Score:3, Informative)
This is a new application whether or not you approve.
-j
Re:Still subjective measurements (Score:3, Informative)
First, you are on the right track in pushing for a double-blind, methodologically sound study. However, the value of analyzing "a number of older experiments performed by a variety of organizations" should not be underestimated. In many ways a meta-analysis (evaluation of existing analyses) is actually more reliable than a single well designed study. No matter how well it is designed, any single study will have weaknesses -- they have a small number of subjects, the truths/lies are limited to a single domain, the time and location of the study has some unexpected influence on the results, etc.
By combining these studies, organizing them by potentially meaningful variables (question type, subject pool, etc.), and weighting their influence by the number of subjects (bigger studies are more important than small ones), you essentially cancel out a lot of the noise (e.g., experimenter bias, weird questions or instructions, etc.)
Second point: The polygraph is reasonably valid as a lie detector. I'd characterize their accuracy as "better than most people, but not good enough to execute someone." Unaided humans in studies similar to the one you outline above perform in the 55-65% range. Significantly better than chance, but not particularly awe inspiring. Moreover, police officers, judges, customs agents, FBI agents, and college students all tend to perform about the same. Some Prisoners, Secret Service Agents, Psychologists interested in deception, and some people who have grown up in abusive environments have been shown to perform even better. But accuracy tends to be pretty domain specific.
The polygraph can arguably be characterized as having an accuracy as a lie detector in the 60-80% range. There are people (and organizations) that will claim accuracies in the 95-100% ranges, as well as those who would argue that the accuracy of the polygraph is 55% or lower. In both cases, you're probably dealing with people who have hidden (or not so hidden) agendas.
Again, the polygraph is a decent tool to determine if someone reacts unusually to some stimulus. Any assumptions beyond that may be unfounded.