Dry Rice Test
Physiological method used by the Chinese to detect deception
- got them to suck on rice and if it came out dry the idea was that they were lying
- dry mouth = anxious = lying
What idea is polygraphy based on
That deception is associated with pysiological change
What did William Marston do?
Polygraph Test
Device for recording someones autonomic nervous system responses
LO1: What are some of the uses of a polygraph test?
What parts of the autonomic nervous system are measured by the polygraph test?
Heart rate, respiration, sweat
Who can get polygraph test trained?
Police, military, intelligence personnel
Polygraph Disclosure Tests
Uncover information about an offenders past
Why is the polygraph test not a real lie detector?
LO1: What are the two main types of polygraph tests?
1) Comparison Question Test
2) Concealed Information Test
The Comparison Question Test (CQT)
What is a comparison question
The Concealed Information Test (CIT)
(guilty knowlegde test)
Developed by Lykken (1960)
- guilty knowledge test
- not used to assess deception
- multiple choice questions
- idea that innocent people won’t react strongly to the answers (will react the same to all possible options)
- most common response: sweat
- very accurate at identifying innocent suspects
What are some problems with the CIT test?
may classify guilty as innocent
Q: In Canada, what is the most common use of the polygraph test?
Police investigations
Q: What type of test is used to uncover information about an offender’s past offending behaviour?
Polygraph Disclosure Test
Q: What does the polygraph measure?
Changes in blood pressure, respiration, and palmar sweating
Q: “During the first 20 years of your life, have you ever thought of cheating on an exam?” This is an example of what type of polygraph exam question?
A comparison question
Q: What has the comparison question test been criticized for?
Assuming that innocent suspects will show larger responses to the comparison questions as compared to the relevant questions
Innocent people can fail and guilty can pass
Relevant = about crime
Comparison = about past behaviour
How are lab studies used to test the accuracy of polygraph tests?
What type of tests do they usually use?
Ground Truth
(about a suspect)
Who is truly guilty or innocent
What are the problems with lab studies?
(mock simulations used to study polygraph tests)
How are field studies used to test the accuracy of polygraph tests?
What’s the difference between an original examiner and a blind evaluator
Original examiner: conduct evaluation of suspect
Blind evaluator: only provided with what the results and are given no info on the suspect or the case