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PSYO 3224 (13)

Detecting deception.docx

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PSYO 3224

History The idea that there are physiological tells for lying dates back centuries (dry mouth, nervous tremors) Cesare Lombroso - 1885 William Marston - pneumograph Polygraph users Investigation Interrogation Insurance Employee testing Screening Polygraphs Relevant/irrelevant test Polygraph disclosure test: Polygraph tests that are used to uncover information about the offender's past behaviour CQT CIT CQT (The Comparison Question Test) Most commonly used test to investigate criminal acts pretest interview, followed by a series of questions administered while the suspect's physiological responses are measure, finally a post-test Pretest is more important --- Convince the suspect of the accuracy of the polygraph Then asks 10 questions: Irrelevant: Unrelated to the crime Relevant: Concerns the crime being investigated Comparison: Concerning the person's honesty and past history prior to the event being investigated Irrelevant: Do you understand that I will only be asking questions we have discussed before? Irrelevant: Do you live in Canada? Comparison: Between the ages of 18 and 28 did you ever deliberately plan to physically hurt someone? Relevant: Did you stab Jane Doe on the night of March 10? Irrelevant: Is your first name John? Comparison: Prior to 2009 did you ever verbally threaten to hurt anyone? Quite accurate at detecting guilt but not very good at determining a suspect's innocence (has a high false positive rate) CIT (The concealed information test) Designed to determine if the person knows details about the crimea Developed by Lykken (1960) Series of questions in multiple-choice format. Each question has only 1 right answer (the critical option) The guilty subject is assumed to display a larger physiological response to the correct option If you were ever the one who robbed the bank then you will know what was used as a weapon. The weapon was a) a knife b) an axe c) a shotgun d) a revolver e) a rifle The most common physiological response measured is palmar sweating Quite accurate at detecting innocence but not very good at determining a suspect's guilt (high false-negative rate) Polygraph validation Laboratory studies Field studies "ground truth" CQT countermeasures Physical - biting tongue, pressing toes to the floor Mental - counting backwards by 7 Honts, Raskin & Kirchner (1994) showed success with both measures CIT lab studies Typical false positive rate of 5% with a false negative rate of 15-24% Ben-Shakhar & Elaas (2003) meta analysis of 80 lab studies - accuracy improved with motivation, 5 or more questions, and verbal response CIT countermeasures Anti-anxiety drugs (e.g. Diazepam) Iacono, Cerri, Patrick & Flemming (1992) found anti-anxiety medication to be ineffective Other measures not well studied CQT and psychopath Raskin & Hare (1978) Patrick & Iacono (1989) - "group contingency threat" NO DIFFERENCE between psychopaths and non (APD) NRC 2003 14 scientists and 4 staff members reviewed polygraph evidence "The physiological responses measured by the polygraph are not uniquely related to deception" Theoretical rationale for CQT is weak Lab studies overestimate accuracy No field studies found that satisfy minimum criteria for a quality study “What is remarkable, given the large body of relevant research, is that claims about the accuracy of the polygraph made today parallel those made throughout the history of the polygraph: practitioners have always claimed extremely high levels of accuracy, and their claims have rarely been reflected in empirical research.” (p. 107) Polygraph Admissibility R.v. Beland (1987) Conspiracy to commit a crime -- robbing a truck -- one of the conspirators turned and went to the police. Evidence is the discussions they had (no recording) -- only have the co-conspirator Established rules against oath helping (bolstering credibility) When you are going to testif
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