PSY 3173 Lecture Notes - Lecture 3: Malingering, Lie Detection, Dont
28 Apr 2018
School
Department
Course
Professor
January 18, 2017
Deception
Learning Objectives
Describe the two types of polygraph tests
Describe the most common errors made by the Comparison Question Test (CQT) and by the Concealed Information
Test (CIT)
Describe physiologically based alternatives to the polygraph
Outline the verbal and non-verbal cues of deception
Define malingering
List the three explanatory models of malingering
Differentiate between the types of studies used to examine malingering
Polygraph Method
Based on the belief that deception is related to physiological change
-Not a lie detector, detects physiological changes
Measures: respiration, heart rate, sweating
-Examiner will determine whether or not someone is lying based on the physiological changes in conjunction with
the questions asked
Othello error: just because you’re reacting and exhibiting signs that you’re lying doesn’t mean that you’re lying
-Ex. You’re heart rate can increase because you’re scared or nervous
Broca hazard: just because you appear to be telling the truth doesn’t mean that you are telling the truth
Uses:
-Helps in criminal investigations: suspect is asked to take a polygraph test
•Can try to coerce a confession - can’t be used in court, but can be informative
-Verify a crime has occurred: victim is asked to take a polygraph test
•Very rare: don’t want to victimize a true victim
-Monitoring sexual offenders on probation (United States)
-Pre-employment screening for security agencies and police
Two main types:
-Comparison Question Test (CQT)
-Concealed Information Test (CIT)
1
January 18, 2017
Comparison Question Test (CQT)
Aka Control Question Test
Includes three types of questions:
-Irrelevant: used to obtain a baseline
•Individual’s identity, background, or personal information
•Ex. Are you left handed?
-Relevant: deal with the crime
•Directly related to the crime
•Ex. Did you assault Sam Smith on March 11th?
-Comparison: deal with prior antisocial behaviour
•Look at a person’s honesty
•Designed to be emotionally arousing
•Ex. Before age 25, did you ever threaten to hurt anyone?
Deception is assessed by comparing physiological responses between relevant and comparison questions
-Guilty suspects are assumed to react more to relevant questions than comparison questions
-Innocent suspects are assumed to react more to comparison questions than relevant questions
Phases:
-Pre-test interview: interview with suspect to develop the comparison questions
•Must establish credibility
-Polygraph exam: questions are asked while suspect’s physiological responses are measured
-Scoring: polygraph examiner scores the physiological responses to determine if the suspect is truthful, deceptive,
or inconclusive
•*DON’T WORRY ABOUT SCORING: just know that it’s scored
•Will pressure the individual to confess if it is judged that they are deceptive
-Post-test interview: if a suspect is judged deceptive they are pressured to confess
Assumptions:
-Assumes guilty people react more to relevant questions and innocent people react more to comparison questions
-Suspect falsely accused of a crime might react more strongly to questions about the crime than to vague questions
concerning past behaviour
Accuracy:
-Majority of guilty suspects correctly identified: 84-92% correctly identified
2
January 18, 2017
-Relatively large number of innocent suspects falsely identified as guilty: 9-24% falsely identified
-Accuracy of original examiners is higher than blind scorers
•Blind scorers can’t take things like body language into effect
Countermeasures: physical and mental countermeasures dramatically reduce the effectiveness of the CQT
-Ex. Trying to control breathing, using pain to increase baseline, focusing on something other than the questions
being asked
-Psychopaths have lower arousal levels, but differences can still be detected
•Psychopaths also don’t have the ability to fake their results
-Physical countermeasures can be effective if you don’t get caught, but police are more aware of these measures
so they’re more likely to be detected
Concealed Information Test
Assesses if suspect has information that only the criminal would know
Asks suspects multiple-choice questions where one option is correct
Assumptions
-Guilty people will react more strongly to correct information
-Innocent people will react equally strong to all options
Rarely used in Canada or United States
-People believe more in the Comparison Question Test, so it is preferred - it is also easier to construct
Criticisms
-The subject may have learned information in the media, so this test may not be an accurate assessment
-The subject may not remember all the details of the crime or may confuse details with past crimes they have
committed
Accuracy:
-No field studies have been conducted in North America
-Very accurate at identifying innocent participants: 95% correctly identified
-Less accurate at identifying guilty participants: only 85% correctly identified
Countermeasures: does not appear to be effected by anti-anxiety drugs
Types of Polygraph Studies
Laboratory studies
-Ground truth is known
3
Document Summary
Describe the most common errors made by the comparison question test (cqt) and by the concealed information. Outline the verbal and non-verbal cues of deception. Differentiate between the types of studies used to examine malingering. Based on the belief that deception is related to physiological change. Not a lie detector, detects physiological changes. Examiner will determine whether or not someone is lying based on the physiological changes in conjunction with the questions asked. Othello error: just because you"re reacting and exhibiting signs that you"re lying doesn"t mean that you"re lying. You"re heart rate can increase because you"re scared or nervous. Broca hazard: just because you appear to be telling the truth doesn"t mean that you are telling the truth. Helps in criminal investigations: suspect is asked to take a polygraph test: can try to coerce a confession - can"t be used in court, but can be informative.
