Week Seven/Eight - Detecting Deception

Question 1

Defining deception key components?

Answer 1

• intent
• no forewarning
• success is not relevant

Question 2

Types of deception?

Answer 2

• falsifications
• distortions / exaggerations
• omissions

Question 3

3 ways to (try to) catch a liar?

Answer 3

1. Physiological / formal techniques
   • polygraph etc.
   • thermal imagining
   • brain fingerprinting
2. Nonverbal / body language cues
   • believed & actual
3. Verbal cues
   • “content” of the lie
   • active interviewing

Question 4

The Polygraph

Answer 4

Measures:
– Heart rate
– Blood pressure
– Breathing (rate & depth)
– Galvanic Skin Response

Detects physiological changes
– assumes that reactions are linked to lying

• Expected changes include:
– Increased skin conductance
– Increased blood pressure
– Decreased respiratory activity
– Decreased blood flow to fingers
due to emotional response to lying (guilt, fear) which leads to the above

Question 5

Polygraph techniques?

Answer 5

1. Control (comparison) Questions Technique (CQT)

2. Guilty Knowledge Test (GKT)

Question 6

1. Control (comparison) Questions Technique (CQT)

Answer 6

• Compare responses for:
– Neutral questions
• establish baseline
– Relevant questions
• related to the specific crime under investigation
– Control questions
• related to the crime / “naughtiness” in general
• intended to embarrass and evoke arousal

Question 7

Problems with CQT?

Answer 7

• Assumes control > relevant for innocent suspect (not convincing)
• Role of examiner
– can’t scare suspect too much or too little
• Ethical question of deceiving suspects
– Inadmissible evidence!

Question 8

2. Guilty Knowledge Test (GKT)

Answer 8

– Based on recognition response (not emotion)
– Responses triggered by personally relevant stimuli
• e.g., hearing own name at role call or party
– Increased EDA; decreased heart rate

• Questions are details that only guilty P would know
– e.g., ‘Where was the body found?’
• Several plausible alternatives for each question
– e.g., ‘in the kitchen’, ‘in the bedroom’ etc.
• Suspect gives same response to each
– e.g., ‘No’.
• If guilty, larger reaction to correct (recognised) alternative

Question 9

Advantages of GKT?

Answer 9

• Better ethics, theory, validity than the CQT

Question 10

Disadvantages of GKT?

Answer 10

Limited to cases where:
• Guilty suspect has the relevant knowledge
• Innocent suspect doesn’t

Question 11

The Polygraph: Does it work?

Answer 11

Claims of up to 99% accuracy
– Dodgy stats: Manipulate ‘accuracy’ result via
comparison structure

need to look at guilty & innocent separately

Question 12

CQT and GKT (false positives and negatives)

Answer 12

CQT = prone to false positives (saying innocent person is lying)

GKT = prone to false negatives (say telling truth when they aren’t)

Question 13

Countermeasures to the Polygraph?

Answer 13

Increase response to baseline/control items
– Physical (e.g., bite tongue)
– Mental (e.g., imagine being slapped)

Decrease response to relevant items
– Mental (count sheep, count backwards)

Overall, very effective
– 50% beat CQT after 30 mins training
– Only 12% of P detected (physical countermeasures)

• Less effective for some techniques (“target” items)

Question 14

Countermeasures with target items

Answer 14

– Used with GKT
– Administrator gives a list of items to memorize
– These appear as alternatives on the GKT
• An innocent person will recognize the target
items but not the guilty items
• Non-recognition of target items = possibly using
countermeasures

Question 15

Summary of Polygraph testing?

Answer 15

– CQT (false positives)
– GKT (better, but false negatives)
– Countermeasures
– Less effective for some techniques (“target” items)

Question 16

Thermal Imaging?

Answer 16

Based on instantaneous anxiety response
- increases in heat

Accuracy rate: 83% (Comparable to polygraph)

Quick, little training required
- May be suitable for mass-screening (e.g., airports)

Prone to false positives

Question 17

“Brain-fingerprinting”: ERP analysis

Answer 17

• Event-related potentials (ERPs)
– Measures changes in P300 waveform
– Reaction to relevant item in series of irrelevant items
– e.g., own name in random series of names

• Orienting technique
– Use with GKT
– Increased P300 reaction to recognised item?

Question 18

Brain-fingerprinting: ERP analysis pros and cons?

Answer 18

Pros:
– Accuracy rate: 82-88%
– High face validity

Cons:
– Same problems as other orienting techniques
(Applicability; culprit’s knowledge of answer;
recognition ≠ guilt)
– Validity in naturalistic settings

Question 19

“Brain-fingerprinting”: fMRI scanning

Answer 19

• Functional magnetic resonance imaging
(fMRI)
– Measures changes in blood flow
– Neural activity in brain and spinal cord

Changes in:
Prefrontal cortex activity
• Monitor & control/inhibit own responses
• Monitor reactions of listener

Anterior cingulate cortex activity
• Risk/reward assessment
• Anticipation of consequences

Question 20

“Brain-fingerprinting”: fMRI scanning pros and cons

Answer 20

Pros:
– Accuracy rate: 78-93%
– Measures central cf. peripheral nervous system
– Taps into complexity- and control-related markers

Cons:
– Lack of replication of results
• Different patterns for different P & types of lies
(spontaneous vs. rehearsed)
– Cost
– Ethical and legal guidelines

Question 21

What do people think are signs of deception?

Answer 21

Non-verbal:
• Signs of nervousness
• Gaze aversion (i.e., looking away)
• Increased body movements, fidgeting

Verbal:
• Reduced detail in speech content
• Errors in speech content

Question 22

How good are people at detecting deception?

Answer 22

Ordinary: 57%
Police: 56%
Secret Service: 64%
CIA Agents: 74%

Question 23

Why detecting deception is no better for professionals?

Answer 23

Relying on the wrong cues
• e.g., increased gaze aversion and fidgeting are NOT signs of lying

Giving incorrect explanations for behaviours
• Acting nervous = lying or worried about proving
innocence
• Avoiding eye contact = guilty? shy? cultural reasons?

Question 24

Emotional markers of lying?

Answer 24

• Higher voice pitch

* Micro-expressions

Question 25

Cognitive markers of lying?

Answer 25

Mentally harder to lie so:
• More errors
• Less detail
• More structure

Question 26

Behavioural markers of lying?

Answer 26

• More rigid

* Less expression

Question 27

Can lie detection be improved?

Answer 27

Train people to look for specific markers
• Ignore gaze aversion; monitor pauses & errors; look
for foot & leg movement; etc

Active Interviewing Techniques

Question 28

Active Interviewing Technique?

Answer 28

• Increase cognitive load
• Unanticipated questions
• Strategic use of information

Question 29

Increasing cognitive load (AIT)

Answer 29

• Reverse order
• Maintain eye contact
• Increase amount of information generated
  • Example of “evidence” from another witness in unrelated
  case (Leal et al., 2013)
• Different reporting modes

Question 30

Potential drawbacks of increasing cognitive load?

Answer 30

May increase amount of inaccurate information generated by truth tellers during interview
• Especially when memory for event is poor

Effectiveness might depend on working memory capacity
(WMC) of person being interviewed
• Ineffective for high-WMC liars?
• Problematic for low-WMC truth tellers?

Question 31

Unanticipated questions (AIT)

Answer 31

• Liars prepare well for interviews
• Benefit reduced for unanticipated Qs
• Cognitively easier for truth tellers than liars

• People anticipate some Qs
“Tell me what happened?” “What topics were discussed?”
…but not others (e.g., spatial and temporal details)
• “In relation to the front door, where was the nearest table?”
• “What order were the topics discussed in?”
• “Who finished their meal first?”

Increases errors and lie detection (up to 80% accuracy)