Deception Flashcards
2 reasons for poor performance in detecting deception
Truth Bias:
Generally believe that what we’re being told is the truth
Incorrect Cues:
Types of changes in detecting deception
Physiological: polygraph readings
Behavioural: Verbal & nonverbal cues evaluated using various strategies
-Observation
-Statement analysis
Polygraph test
Based on the assumption that lying causes physiological changes
- Heart Beat
- Blood Pressure
- Respiratory rate
- Electro-dermal activity (finger sweatiness)- Galvanic skin response
Uses of polygraph
- Ensure crime happened(victim)
- Helps criminal investigations(suspects)
- Monitoring sexual offenders on probation
- Pre employment screening
Polygraph laboratory studies
Volunteers randomly assigned to commit or not to commit a mock crime
Advantage:
Ground truth known
Experimenter knows who is guilty or innocent
Disadvantage:
Generalizability/ecological validity limited
Lack of motivation
Lack of emotion
Polygraph Field studies
Compare accuracy of original examiners to blind evaluators
Original examiners conduct evaluation of suspect
Blind evaluators only see examiner’s charts
Given no information about suspect or case
Advantage:
‘real world’
Disadvantage:
ground truth???
3 main types of polygraph tests:
Relevant/Irrelevant Test
Comparison/Control Question Test (CQT)
Concealed Information Test (CIT)/ Guilty Knowledge Test (GKT)
Relevant/Irrelevant Test
2 types of questions: Relevant E.g., “Did you steal the rare gold coin?” Irrelevant E.g., “Is today Monday?” Assumption: -Larger physiological responses to relevant questions deception No longer used in law enforcement Why? Used for employee screening
Comparison/Control Question Test (CQT)
3 types of questions: Irrelevant: Refer to identity or background Used to establish baseline E.g., “Do you live in Canada?”
Relevant:
Details about crime being investigated
E.g., “Did you assault Joe on November 11th?”
Control:
Designed to be emotionally arousing for anyone
Establish honesty
Deal with prior behaviour (before event in question);
E.g., “Between the ages of 18 and 22, did you ever deliberately physically hurt someone?”
Procedure:
Pre-test interview:
Control questions developed
Examiner convinces suspect of polygraph accuracy
Interview:
All 3 types (mostly 1 and 2)
Analysis:
Compare arousal levels
Assumption
Guilty suspects react more to relevant than control
Innocent suspects react more to control than relevant
Concealed Information Test (CIT)/ Guilty Knowledge Test (GKT)
Assesses if suspect has info that only perpetrator would know M/C questions, one option is correct E.g., “If you were person who robbed the bank, then you would know what weapon was used. Was the weapon: a knife a shotgun a revolver a rifle an axe Assumption Physiological response to info you recognize Not used in Canada or United States Used in Israel, Japan
Physiological Measures in Deception detection
Thermal imaging:
Detects facial warming due to blood flow
Brain-based measures:
Event-related brain potentials (ERP):
Electrical activity in the cerebral cortex
Functional magnetic resonance imaging (fMRI):
Measures brain activity (areas of activation)
Behavioural Cues
Vocal cues: Examples Higher voice pitch Increased speech disturbance ah, umm Slower speech Pattern may depend on complexity of lie
Verbal cues: Indicators of honesty: Make corrections in account Admit to lack of memory Indicators of deception: Little detail Less compelling accounts More nervous and tense Fewer details
Non Verbal Cues: Gaze aversion Smiling Blinking Fidgeting Illustrators
Deception detection in children
Statement Validity Analysis (SVA):
Developed by Undeutsch (1989)
Assess credibility of child witnesses in cases of alleged sexual abuse
Based on Undeutsch Hypothesis:
Statements that are product of experience contain characteristics that are absent from statements that are product of imagination
3 elements of Statement Validity Analysis
Semi-structured interview:
Child provides account of allegation
Child must tell his/her story without any influence from interviewer
-“Narrative free recall”
May include follow-up prompts or questions
E.g., “What happened next?”
E.g., “You just mentioned a man. What did he look like?”
Interview is recorded & transcribed
Transcripts analysed with CBCA
Criteria-Based Content Analysis (CBCA)
- General Characteristics- cognitive criteria(too difficult to make up)
- Specific Contents- Cognitive criteria(too difficult to make up)
- Motivational Content- Truth tellers are not as concerned with impression management
- Offense Specific-Details of typical offence
Evaluation of CBCA outcomes Consider: Appropriateness of- Language and knowledge/affect shown by interviewee Susecptibility to sugestion Overall adequacy of interview Motives to report Consistency
Validity and Reliability in the SVA
Most consistent criteria:
Coherence (logical structure)
Quantity of detail
Contextual embedding
Not admissible in court
