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Detecting Deception.docx

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McMaster University
Richard B Day

September 17 , 2013 Psych 3CC3: Forensic Psychology Detecting Deception Facial/Body Cues to Deception - Avoiding eye contact - More smiling and laughter - Higher rate of eye blinking - Nervous fidgeting - More illustrative gestures - More movement of legs, feet, hands - More body, head movements - More shrugging - None of these are good indicators of lying - These cues are more often associated with truth telling - Criticism of the Reid model - Yet in general, we are not that bad at detecting lies - “The meta-analytic (combining the data from many studies and reanalyzing as a group) literature fails to identify any pattern of facial or body movement that generally signals deception. However, some studies designed to develop indicators based on these movements show some ability to discriminate lying from truth-telling… These studies suggest that the right measures of facial and motion features can offer accuracy better than chance for the detection of deception from demeanor in somewhat realistic situations” - Introductory psychology students and police officers were equally accurate; furthermore, were more accurate when they could not see the suspects - If we want to maximize accuracy we should not see them as cues are misleading Working Cues to Deception - Looked at 105 different potential indicators of lying - Focus on the content of the story - Associated with deception at a greater than chance level 1. Liars less forthcoming  Provide fewer details  Less information  Some studies oppose this cue 2. Liars tell less compelling stories 3. Liars = more negative impression  Left an overall more negative impression with the viewer or listener; yet, the listeners could not pinpoint exactly what aspect about the individual left this impression 4. Liars more tense 5. Fewer imperfections, unusual content  Strange or unusual details The Language of Deception - Verbal immediacy: present tense, active voice  Telling a story that puts the teller right in the middle of the story  The story is more immediate  Lying is associated with lower levels of verbal immediacy: past tense, distance from the events  Not an extraordinarily strong relationship - Fewer details in story - Impressions of verbal uncertainty  Truth-tellers provide a greater sense of certainty - Impressions of nervousness - Lack of logical structure to story - Lack of plausibility to story - Raised pitch of speech  Slight tendency  Not very strong - More correlated but cannot actually be used to determine deception Detection Easiest When - Lies have high personal relevance  Above personal characteristics of behaviour  High levels of consequences  In the real forensic context compared with artificial tests, it should be easier to detect lies - Stakes of deception are high - Liar knows he’s lying - Liar has little chance to rehearse  Earlier questioning gives less time for rehearsal Ekman, O’ Sullivan and Frank (1999) - Detecting falsehood based on viewing a videotape of true or false statements - Comparing: federal officers, sheriffs, federal judges, deception/clinical psychologists, regular clinical psychologist and academic psychologist - Overall accuracy:  Federal officers scored the best  Second clinical/deception psychologist  Federal judges and academic psychologist are the least accurate (70%) - Lie accuracy:  Federal judges due the worst  Probability of detecting lies is higher than overall accuracy - Truth accuracy:  Much lower at detecting truth  ¼ of the time we are making mistakes at truth-telling - Most mistakes are biased towards seeing lies when there aren’t any - Seeing lies when the truth is being told - We are more likely to see someone as guilty when they are innocent than seeing someone as innocent when they are guilty Polygraph vs. Lie Detector - Polygraph: machine to record voltages  Neutral machine which has no special ability to detect lie  Can be used to measure a number of different physiological aspects - Lie detector: application of polygraph Polygraph Record - Polygraph examiner uses the data to make a judgement about deception or honesty - Blood pressure - Heart rate - Respiration (breathing) - Galvanic skin response (conductance or resistance) - Not designed to detect lies - Designed to detect anxiety or other negative emotions - Liars are more likely to be anxious – this is an assumption behind the polygraph test that is not always true Control Question Test (CQT) - Involves asking several different kinds of questions - Yes/no questions to reduce the variability - Relevant questions: about crime  “Did you shoot Sam Smith?” - Irrelevant questions: about nothing  “Do you live in Toronto?”  Typically questions about the individual  Assumption that the individual will be nervous - Control questions:  “Have you ever injured anyone?”  About general immoral or unethical behaviour  Not very nervous about these questions - Relevant and control questions are the most important Control vs. Relevant - Truth:  Control questions should be more anxiety producing than relevant questions - Lie:  Control questions are designed as to elicit people to lie  Liars are more anxious in the relevant questions than in the control questions - Opposite pattern of arousal from liars vs. truth tellers CQT Procedure - Pre-test  Attach the equipment and talk to the individual  Designed to relax the individual and to draw the individual irrelevant questions  Convince subject of test accuracy – make sure the individual is aware that he will be detected if he tells a lie, make him anxious about telling lies  Learn personal details  Develop irrelevant questions  Takes more time than the actual test - Test  10 sets of questions with 3 pairs of control and relevant questions  Ask and score questions  5 different measures  Compare each of the measures on each pair of control and relevant questions  Score depending on how much different the response is  If the control arousal than the relevant questions it is an indication of truth telling and is scored as +1 to +3 (positive numbers indicate truth telling)  If arousal to relevant question is higher than control questions it is an indication of deception it is scored as a negative number  For each pair of questions you have 5 comparisons from each of the measures  15 different scores  Maximum scores: -45 to +45  How low does the score have to be to determine lying is a subjective judgement from the examiner - Post-test  Sum scores,
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