L13 - Detection of Deception Flashcards
Define deception
“A successful or unsuccessful deliberate attempt, without forewarning, to create in another a belief which the communicator considers to be untrue”
What are the 3 types of lies?
- Outright lies - lies and then tells the police they didn’t do it
- Exaggerations - facts are overstated, or information is expressed in a way that exceeds the truth
- Subtle lies - literal truths that are designed to mislead (may admit relevant details)
What are the 5 reasons to lie?
- to gain personal advantage
- to avoid punishment
- to make a positive impression on others
- to protect themselves from embarrassment/disapproval
- for the sake of social relationships (self-oriented vs. other-oriented)
What is the frequency of lying?
Lying frequency depends on what 3 things?
American diary study: college students told 2 lies/day and community members told 1 lie/day
o Most lies were self-serving
Frequency of lying depends on:
1. The personality and gender of the liar
Extroverts lie more than introverts
Frequency of lies similar between men and women
Women tell more social lies
• Both men and women prefer conversations with women - probably because they engage in more social lies, more engaging
When dating, women lie to improve physical appearance, men lie to exaggerate earning potential
- The situation in which the lie is told
90% lie to prospective date
83% lie to get a job - People to whom the lie is told
Lowest rate of lying with spouses (1/10 interactions – mostly subtle)
• When we do lie they tend to be the most serious lies – for example infidelity
Highest rate of lying with strangers
College students lie frequently to their mothers (almost 50% of conversations)
What are behavioural indicators of deception?
What are some verbal and nonverbal cues?
- Emotion
Paul Ekman’s emotional approach:
• Deception results in different emotions: guilt, fear, excitement
• Strength of emotion depends on personality of liar and circumstances of lie
• Emotions may influence a liar’s Nonverbal Behaviour (NVB)
• NVB during deception should show signs of stress compared to baseline of typical NVB
• HOWEVER we can also show these signs of arousal when we are really excited and telling the truth
o But the people telling the truth will be more relaxed - Content complexity: lying can be difficult to do
People engaged in cognitively complex tasks exhibit different nonverbal behaviours
• Can ask people to tell things in reverse order, may be able to indicate who is lying - Attempted behavioural control
Liars may attempt to control their behaviour in order to avoid getting caught
When liars do this, they sometimes over control themselves, resulting in rehearsed and rigid behaviour (therefore they will make eye contact, and they won’t stutter their words and they won’t fidget)
Nonverbal behaviour is more difficult to control than verbal behaviour
Verbal cues: o Higher pitch of voice o Increased response latency o Increased errors in speech o Shorter length of description
Nonverbal cues:
o Decreased nodding
o Decreased foot and leg movements
o Decreased hand movements
What are content indicators of deception?
Statement Validity Assessment
o Developed in Germany to determine the credibility of child witnesses’ testimonies in trials for sexual offences
o Extended to adults and other types of cases
o SVA accepted in other European courts, but not UK courts. Opinion in US is divided
o Has been presented in expert testimony in US, but main role in guiding police investigations and decisions of prosecutors
o Consists of three major elements:
1. Semi-structured interview
2. Criteria-based content analysis (CBCA) of transcribed version of statement given during the interview
3. Evaluation of the CBCA outcome via a set of questions (validity check-list)
Does SVA work?
Vrij (2005) reviewed first 37 experimental and field studies on CBCA
- Field studies:
o Statements made by persons in actual cases of alleged sexual abuses
o Clear forensic relevance, but difficult to establish ground truth
- Experimental studies:
o Statements of participants who lied or told the truth for the experiment
o Easy to establish veracity of statement, but differ from real-life situations
- Criterion 3 (truth tellers give more information than liars) received the most support: in 80% of studies truth tellers included more details
- Cognitive criteria (1-13) received more support than motivation criteria (14-18)
- In 92% of experimental studies, truth tellers received higher CBCA scores than liars
- Trained evaluators often achieve above chance classification
Some concerns about SVA
- No formal decision rules, profiles for truth or deception, or cut points
- Criteria should be given different weight
- Different types of lies (from subtle to outright) may yield different levels/kinds of characteristics
- SVA assessments are subjective and inter-rater reliability can be low, even after extensive training
- CBCA assessments of written statements are time-consuming and even training may not improve accuracy
Discuss reasons why it is difficult to detect deception
- Lie detection is difficult and there is no give-away cue
- Othello error: truth tellers may show similar behaviour to liars because they, too, may experience emotions, may have to think hard, or may have to control themselves
- Adequate comparisons between truth-telling and lie-telling are not made (e.g. small talk vs. interrogation)
- Observers seem to have incorrect beliefs about how liars behave and people, including police officers, are taught wrong cues
- Liars can use countermeasures (e.g. can train themselves to beat techniques)
- Deception research is often conducted in university labs and the stakes aren’t high enough. It’s hard to establish ground truth in field studies
- The Brokaw hazard: individual differences in emotional expression, vocal and body movement characteristics
- Individual differences in ability to control: some people are natural liars, or have trained themselves to be very effective liars
- Cultural differences in nonverbal behaviour
