WEEK 5 Flashcards
what is the polygraph?
Sometimes called a “lie detector”.
It was assumed that lying is accompanied by physiological activity within liar’s body.
Polygraph tries to detect these signs by Displaying a direct representation of various types of bodily activity e.g. Sweating of fingers (GSR), blood pressure, respiration
what types of questions are used in questioning with polygraphs?
Comparison Question Test (CQT) and Guilty Knowledge Test (GKT) (aka Concealed Information Test).
what is comparison question test (aka control question test)?
The most commonly used and most disputed type of test
Compares responses to relevant questions with responses to control questions (about 10 in all)
what are the irrelevant or neural questions in the Comparison question test?
date of birth, name, address
what are the relevant questions in the comparison quesion test?
are specific questions about a crime
“On March 12, did you see Scott Fisbee?”
what are comparison questions in the comparison question test?
questions deal with acts that are related to the crime but do not refer to the crime in question
what are the characteristics of comparison questions?
General, vague, and cover long periods of time
Attempt to embarrass suspect to evoke arousal as they are given no choice but to lie
“Have you ever tried to hurt someone to get revenge?”,
”Have you ever taken anything from a workplace without permission?”
what are the assumptions of comparison question test for an innocent suspect?
Control questions generate more arousal than relevant questions because they respond deceptively to the control questions and truthfully to the relevant questions
what are the assumptions of comparison question test for a guilty suspect?
Relevant questions generate more arousal than control questions because they respond deceptively to both types of questions but the relevant questions present a more immediate threat to the suspect and so elicit a greater response
how are the differences in physiological reactions in the comparison question test rated?
subjectively by the tester (from -3 t0 +3)
what happens if a suspect fails the comparison question test?
they are pressured into a confession in the post-test interview
what is the aim the concealed information test?
Aim is to determine whether suspect has knowledge which they do not want to reveal about a particular crime
what are examples of the concealed information test?
A suspect has killed a person with a knife
They deny this during an interview
CIT examiner shows suspect a series of knives (including the one used in the killing) and asks for each one whether the suspect recognises it
Both innocent and guilty suspects will deny recognising each knife
The guilty suspect is will show a heightened physiological response when shown the correct knife
The CIT can only be used when sufficient specific details about the crime exist that have not been released to the public and that the criminal is likely to know about the crime
what are the problems with polygraphs?
Potentially low base rates of deception
Some people are emotionally nonreactive and so produce no physiological response when lying
Innocent people may still react strongly to questions about whether they committed a crime
Polygraphers have to convince the suspect that the polygraph is a flawless detector of lies
May involve lying which is not allowed in many jurisdictions
Suspect in CIT may admit having guilty knowledge but deny guilt
Lack of standardisation
Countermeasures may be used by suspect
Difficult to test the accuracy of the polygraph
why do polygraphs lack standardisation?
Scoring is subjective
Questions differ from test to test
How do countermeasures reduce the reliability of polygraphs?
the reduce the detection of lies by 50%
What are physical countermeasures used by suspects?
tongue biting
Pressing toes to floor
What are mental countermeasures used by suspects?
Counting backwards from 100
Imaging either a calming scene or an arousing scene
why is it difficult to test the accuracy of the polygraph?
Laboratory studies don’t involve the same severity of consequences
In field studies, we never know for certain who is lying
what was the polygraph’s accuracy for correctly classifying guilty suspects as guilty?
84-92%
what was the polygraph’s accuracy for correctly classifying innocent suspects as innocent?
69.7%
what was the polygraph’s inaccuracy for incorrectly classifying guilty suspects as innocent?
9.7%
what was the polygraph’s inaccuracy for incorrectly classifying innocent suspects as guilty?
9-24%
what was the polygraph’s inaccuracy for not being able to classify guilty suspects?
11.8%
what was the polygraph’s inaccuracy for not being able to classify guilty suspects?
14.8%
Why is nonverbal communication so important?
When verbal and nonverbal messages do not match, nonverbal behaviour the ‘better’ indicator of the truth (harder to control)
Why is nonverbal information harder to control?
Automatic links between emotions and nonverbal behaviours
(E.g., fear and automatic facial expression and body movement).
People unaware of what normal nonverbal behaviour is.
People are not practiced in controlling nonverbal behaviour.
what does nonverbal communication depend on?
Depends on type of lie used: fabrication ‘harder’ than concealment which leads to more disturbances
what factors influence deceptive behaviour?
stakes, motivation, planning and differences between lab and real police interviews
How do stakes influence deceptive behaviour?
high stakes result in nervous behaviour
How do motivation influence deceptive behaviour?
Highly motivated liars behave differently
Fewer movements, slower speech, higher pitch voice, more disturbances
How does planning influence deceptive behaviour?
‘Planned’ liars behave differently from spontaneous liars
Zuckerman & Driver (1985) – planning associated with fewer arm/head movements, shorter response latencies and faster speech rate
how do experimental situations influence deceptive behaviours?
Experimental situations do not involve the incredibly high stakes and cognitive load of the police interview
Who developed the concept of micro expressions?
Paul Ekman