Polygraph tests accurate or not o cit rarely used in

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POLYGRAPH TESTS: ACCURATE OR NOT? o CIT rarely used in North America o CTQ used for >30 Years, yet accuracy is controversial o Very high false-positive rate indicates that innocent people respond more to relevant than comparison questions— underlying premise is not universal o CIT vulnerable to false-negative errors (falsely calssifying gulty susepcts as innocent, where CQT is vulnterably to false positive (falsely classifying innocent suspects as guilty) Can the Guilty Learn to Beat the Polygraph? BOX: Seeing Through the Face of Deception - HD thermal face imaging to detect deceit o Measures amount of facial warming—linked to region blood flow - Use of thermal imagining 75% accuracy on guilty participats, and 92% on innocent partiicpants - Unlikely to be used in airports - Officers were better at recognizing
- countermeasures: as applied to polygraph research, tehcniques used to try to conceal guilt - 30 min video showing CQt premise was enough to beat it - 50% of guilty suspects beat the test—examiners couldn’t tell the use of countermeasures Scientific Opinion: What do the experts say? - negative view - still used as an investigative tool - whatever its actual validity, causes many suspects to confess, resolving the crime Admissibility of Polygraph Evidence - First submitted as evidence in court in 1923 - Not admissible in Canadian courts of law Brain-Based Deception Research - event-related brain potentials (ERPs): brain activity measured by placing electrodes on the scalp and by recording electrical patterns related to presentation of a stimulus - One type—P300 o When using CIT, guilty suspects response to crime-relevant events with a large P300 response o No difference in P300 response with innocent subjects o Resistant to manipulation - fMRI measures the cerebral blood flow in different areas of the brain o determining which areas of the brain are associated with deception in a variety of deception paradigms, like forced- choice lies, spontaneous lies, rehearsed lies, faking memory impairment, and concealed information tests o lie conditions produce greater activation in prefrontal and anterior cingulate regions, compared to truth conditions - brain-imaging techniques can differentiate which parts of the brain are involved in lying, and the different types - general trends vs. individual participants - participants are usually healthy, with no neurological or psychiatric disorders
- general consensus: premature to use fMRI to detect deception, and it hsouldn’t be admissible in court - people believe science (validity) more than other images o Evidence from fMRI lie detection=more guilty verdicts o If questioned about validity of fMRI, guilty verdicts reduced Verbal and Nonverbal Behaviour cues to lying - common method od deception detection: analysis of verbal cahracteristics and nonverbal behaviours o act of deception produced a physciologal change compared with telling the truth - harder for people to control aspects of their nonverbal behavior than their verbal behavior - people who focused on tones of voice better at detecting

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