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The Polygraph machine

The Polygraph machine. 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 to determine if someone was being deceptive. The Doctor Himself. The Polygraph.

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The Polygraph machine

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  1. The Polygraph machine Is it Science?

  2. The beginning • The father of the US polygraph machine was Doctor William Marston • He designed the first device that measured blood pressure to determine if someone was being deceptive.

  3. The Doctor Himself

  4. 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.

  5. 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

  6. Two myths about the polygraph • The polygraph provides an objective answer to truth or deception. • The polygraph is infallible • Both are wrong!

  7. 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)

  8. 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

  9. 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

  10. 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%

  11. 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%

  12. The Polygraph vs the courts • Frye v. United States 1923 • 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

  13. Bringing GDT to the courtroom • the Daubert standard • falsifiable, known error rate, peer reviewed, accepted by the scientific community

  14. 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

  15. 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

  16. 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).

  17. Questions • Questions?

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