Presentation on theme: "Is it Science?. The beginning The father of the US polygraph machine was Doctor William Marston He designed the first device that measured blood pressure."— Presentation transcript:
The Polygraph From Skepdic.com: A polygraph is an instrument that simultaneously records changes in physiological processes such as heartbeat, blood pressure, respiration and electrical resistance.
Screening Polygraph is used by some employers to screen job applicants (CIA) Extremely hard to come up with empirical results because no-wrongdoing is expected They ask questions they feel may be important in the future. i.e. past stealing and respect for authority Because they use the CQT –often fails
Two myths about the polygraph The polygraph provides an objective answer to truth or deception. The polygraph is infallible Both are wrong!
Two different types of Polygraph tests There are two different types of Polygraph tests that can be given They are: The Controlled Question Test (CQT) The Guilty Knowledge Test (GKT)
The Controlled Question Test This type of polygraph exam is the most widely used Does it have any basis in science? NO! What happens? Pretest Test Posttest ~4 hours Countermeasures – college students 70% grounded in theory – – standard procedure – contamination – objectification –not blinded
The Guilty Knowledge Test This test is used the least often Does it have a basis in Science? YES! How does it work? – doesn’t test lie detection Controls, grounded in theory – orienting responses – standard procedure – less contamination Countermeasures hard to come by If it is scientific why is it not used more? Hard to implement: Silence/ large number of questions Shenanigans – test was designed by scientists – non scientists who developed the CQT Don’t want to recognize that
Empirical Findings of CQT First, extremely hard to get data – examiners like to claim perfection, and it is hard to get exact data. Out of 250 studies – only 10 were considered to be up to research standard – and they didn’t even have to do with testing at a grand scale – just individual instances Results of the ten: Correct guilty: 70.6%-98.6% Correct innocent: 12.5- 94% False negatives 0-28% False positives 0-75%
Empirical Findings of GKT Testing is still in infancy- but because GKT stands to a scientific standard – results are highly superior to the CQT results Accuracy rate for guilty – 81% Accuracy rate of innocent – 96%
The Polygraph vs the courts Frye v. United States 1923 Frye v. United States Established Frye Standard – expert testimony can only be accepted when the majority of the scientific community accepts the science. Daubert v. Merrell Dow Pharmaceuticals 1993 Established the Daubert standard Judge decides Testing – falsifiable, known error rate, peer reviewed, accepted by the scientific community United States v. Scheffer
Bringing GDT to the courtroom the Daubert standard falsifiable, known error rate, peer reviewed, accepted by the scientific community
What can we conclude CQT is broken – Stop using it! There is no way to revive this dead horse GKT looks incredibly valid – still need some more research – but it rests on solid ground However, in this class we are called to be skeptics and have an open mind, but not too open that our brains fall out. Because the evidence supports GDT, I believe there is something valid about it This means the polygraph may not have been a completely worthless device after all
So you all don’t forget – laundry list of problems with the CQT No objectification – Also, can’t compare results Only 15 minutes with actual device Easy to beat – agree to questions beforehand Because of post-test interview – no legitimate amount of records Baseless theory – changes in physiological >>> deception Technology has stayed put
Dr. Travis Patterson “Numerous scientific papers by knowledgeable individuals have been presented in affirmation and rejection as to the absolute reliability regarding any and all of these procedures” (Patterson). : “various procedures – finger prints, blood analysis, psychological approaches, psychometer procedures, psychiatry, etc – have been adopted, and accepted, by the courts in determining an expedient conclusion” (Patterson).