Week 7 - Deception Flashcards
What are the 3 key components in deception?
- intent
- no forewarning
- success is not relevant
What are the 3 types of deception?
- falsifications
- distortions/exaggerations
- omissions
What are 3 ways to (try to) catch a liar?
- physiological/formal techniques
- nonverbal/body language cues (believed and actual)
- verbal cues (content of the lie, active interviewing)
Who invented the polygraph?
invented by William Marston
What does the polygraph measure?
- heart rate
- blood pressure
- breathing (rate and depth)
- galvanic skin response
The polygraph detects physiological changes. This assumes that reactions are linked to:
lying
Expected changes in polygraphs include:
- increased skin conductance
- increased blood pressure
- decreased respiratory activity
- decreased blood flow to fingers
What are common emotional responses to lying?
guilt, fear, excitement.
In polygraphs, we look for behaviours linked to:
change in emotion
What is the control (comparison) questions technique? We are comparing responses for:
- neutral questions (establish baseline)
- relevant questions
- control questions
Does lying trigger a behaviour?
No - but it might trigger an underlying emotional process, which we will see in a polygraph.
What are some problems with the control question technique?
- assumes control (more reaction ) > relevant for innocent suspect
- assumes relevant (more reaction to these) > control for guilty suspect
- role of examiner (can’t scare suspect too much or too little)
- ethical question of deceiving suspects
What is the guilty knowledge test?
- questions re details that only guilty P would know
- several plausible alternatives for each question
- suspect gives same response to each
- if guilty, larger reaction to correct (recognised) alternative
What is one advantage to the guilty knowledge test, over the control question test?
better ethics than the control question technique.
The polygraph can be administered to a suspect using the control question technique. At the end, the police might say it looks bad at the end, even if they’re innocent they might confess. What is the main problem with this?
Even if the polygraph shows they’re innocent, they cannot use it in court. “They deceived me into confessing”, doesn’t cut it.
The guilty knowledge test is based on ___ not ____
recognition response, emotion
Responses in the guilty knowledge test are triggered by:
Personally relevant stimuli (e.g., hearing own name).
What happens in the guilty knowledge polygraph test when personally relevant stimuli is triggered?
increase EDA, decreased heart rate
The guilty knowledge test is limited to cases where:
- guilty suspect has the relevant knowledge
- innocent suspect doesn’t
Claims of polygraph accuracy is up to:
But these are:
99%, dodgy stats (if 1 person is lying out of 100, you still got it 99% accuracy).
Control question technique (when it makes a mistake) tends to:
Classify an innocent person as guilty. (prone to false positives)
The guilty knowledge technique (when it makes a mistake) tends to:
Classify a person as innocent when they’re not. (prone to false negatives)
What are the methodological issues with polygraph studies in the lab?
stakes may not be high enough
What are the methodological issues with polygraph studies in field studies?
No way of knowing if really guilty
What are some countermeasures to the polygraph?
- Increase response to baseline/control items.
- physical (bite tongue)
- mental (imagine being slapped) - decrease response to relevant items
Overall, how effective are countermeasures?
50% beat control question technique polygraph after 30 minutes of training.
What percentage of physical countermeasures were detected in polygraphs?
Only 12%
What percentage of mental countermeasures were detected in polygraphs?
none
What are target items in polygraphs, as a way to detect countermeasures?
-Used with guilty knowledge test
-administrator gives a list of items to memorise
-these appear as alternatives on the GKT
(an innocent person will recognise the target items but not the guilty items, non-recognition of target items = possibly using countermeasures)
What can thermal imaging have to do with detecting deception?
If someone is lying there will be more heat (around eyes etc) based on instantaneous anxiety response.
What is the accuracy rate of thermal imaging?
83% (comparable to polygraph).
What is one benefit for thermal imaging?
It’s quick, little training required.
What are some problems with using thermal imagin?
Lower accuracy rates in other studies (67%).
Prone to false positives.
What is a problem with using thermal imaging in airports?
With the huge amount of people going through the airport each day, what are you going to do if many people get picked up? Can’t search through all their bags?
What is Brain fingerprinting?
measuring event related potentials. Measures changes in P300 waveform. Reaction to relevant item in series of irrelevant items.
What are the pros of brain fingerprinting?
Accuracy rate is 82-88%
High face validity
What are the cons of brain fingerprinting?
Same problems as other techniques.
Recognition doesn’t necessarily equal guilt
What does fMRI be used for?
- measures changes in blood flow
- neural activity in brain and spinal cord
What might we might find in fMRI scanning in lying?
- activity in the prefrontal cortex activity
- anterior cingulate cortex activity (risk/reward assessment, anticipation of consequences)
What is the accuracy rate of fMRI scanning in lie detection?
78-93%
What are some cons of fMRI scanning in lie detection
- lack of replication of results
- cost
- ethical and legal guideline
