Week 7&8: Lie detection Flashcards
What are the key components of deception?
- Intent: needs to be an intentional attempt to deceive someone
- No forewarning: Person doesn’t tell they’re attempting to
- Success is not relevant: it is just the attempt
Types of deception?
- Falsifications: making stuff up
- Distortions/exaggerations: changing the story in some way
- Omissions: leaving things out of the story
What are the 3 ways to catch a liar?
- Physiological/formal techniques - normally using technology to measure physiological changes e.g. polygraph
- Non-verbal/body language cues: some of these are things that people BELIEVE are associated with lying and things that ACTUALLY are
- Verbal cues: content of the lie - active interviewing techniques
What is a polygraph?
Technology that has a lot of sensors that measure physiological senses when you interview
What kinds of things does a polygraph measure?
- Heart rate
- Blood pressure
- Breathing (rate & depth)
- Skin response
Certain patterns in these indicate if the person is telling the truth or lying due to a change in emotion when lying
What are the 2 polygraphing techniques?
- Control Questions Technique (CQT)
2. Guilty Knowledge Test (GKT)
What is the Control (comparison) Questions Technique (CQT) of polygraphing?
Comparing responses of (3):
Neutral questions: to establish a baseline (e.g. whats your name)
Relevant questions: related to the specific crime under investigation
Control questions: unrelated to the crime in question - ask questions that most people would find it difficult to say no to - a person who is being honest should say yes. A person who is telling the truth is assumed to fear control questions more than relevant questions.
What is the idea of control and relevant questions (CQT)?
Crime relevant questions should provoke more anxiety than control questions if guilty
If innocent - asking about actual crime shouldn’t produce too much anxiety or stress
What are some problems for the CQT?
Assumes that control questions are going to be more anxiety provoking for innocent suspects - basis for entire question techniques
Role of examiner - shouldn’t scare the suspect too much or too little with control Q’s - will change gap between two types of questions and have implications for either innocent or guilty suspects
Ethical issues
What is the polygraph Guilty Knowledge Test (GKT)?
Based on recognition response (not emotion) - physiological responses indicate
Responses triggered by personally relevant stimuli - when we recognise something
Questions that only a guilty person would know and several plausible explanations given for answer
- Suspect gives same response to each one ‘no’
If they’re guilty they will have a greater reaction to the correct (recognised) alternative
What is the advantage to the GKT?
Better ethics
Problems of GKT?
It is limited to cases where the guilty person has the relevant knowledge and the innocent suspect doesn’t
Knowledge doesn’t = guilt
Does the polygraph work?
Claims of 99% accuracy
- Dodgy way of obtaining statistics
What do proper data show on effectiveness of polygraphs?
Can get accuracy rates between 65-85% generally, does vary from study to study
No where near accurate enough to be treated as evidence in court
What are some methodological issues with polygraph data?
In lab studies: the stakes might not be high enough
In field studies: no way of knowing if the person is actually guilty
What are polygraph countermeasures?
Attempts to ‘beat’ a polygraph
1. increase physiological response to baseline/control measures - physical approach (bite tongue) or mental approach (imagine being slapped)
- Decrease response to relevant items - dampen down response
- mental distraction techniques - takes attention away (count sheep, backwards etc)
Can you really beat a polygraph?
- 50% of participants beat CQT in 30 min of training
- only 12% of physical countermeasures detected - no mental countermeasures were detected
- less effective for some techniques (target items)
