week 5 Flashcards
what does the polygraph test assume
that lying is accompanied by physiological activity within liars body
what does the polygraph try to detect
displays a direct representation of various types of bodily activity such as
sweating of fingers (GSR)
blood pressure
respiration
what are problems with polygraphs
potentially low base rates of deception
some people may react wrong eg. innocent reacts strongly or person who committed crime doesn’t react
polygraphers have to convince the suspect that the polygraph is a flawless detector of lies (this may involve lying which is not allowed in many jurisdictions )
lack of standardisation
countermeasures may be used by suspect
difficult to test the accuracy
what is meant by a Lack of standardisation in polygraphs
Scoring is subjective
Questions differ from test to test
types of Countermeasures may be used by suspect when getting a polygraph
tongue biting
pressing toes on floor
counting backwards from 100
imaging either a calming scene or an arousing scene
what percentage of Guilty suspects correctly classified as guilty
84 – 92%
what percentage of Innocent suspects correctly classified as innocent
69.7%
what percentage of Guilty suspects incorrectly classified as innocent
9.7%
what percentage Innocent suspects incorrectly classified as guilty
9 – 24%
what percentage of Guilty suspects that cannot be classified
11.8%
what percentage of Innocent suspects that cannot be classified
14.8%
When verbal and nonverbal messages do not match:
nonverbal behaviour the ‘better’ indicator of the truth (harder to control)
why is it hard to control nonverbal communication
Automatic links between emotions and nonverbal behaviours
eg. fear and automatic facial expression and body movement
People are unaware of what normal nonverbal behaviour is
People are not practised in controlling nonverbal behaviour
what is the Micro Expression Training Tool (METT)
Trained to identify micro expressions, feedback, photos of faces with emotions,
large increases in accuracy with one-hour training
how many people are charged per year solely based on eyewitness evidence
77,000
in the UK what percentage of cases where only evidence was eyewitness led to a conviction
74%
Where can the memory go wrong?
Acquisition or encoding stage
Retention or storage stage
Retrieval or recall stage
how can memory go wrong in the Retrieval or recall stage
forgetting, failure to communicate important items
how can memory go wrong in the Retention or storage stage
decay, forgetting, post-event feedback
how can memory go wrong in the Acquisition or encoding stage
not paying enough attention
in 36 of the first 40 cases the innocence projects examined what was the primary evidence
eyewitness identification
how many DNA exornerations have happened
356
how many of the dna exonerations did they find the true suspect
150