PSYCH 3CC3 Chapter 4: Deception (pg. 93-116)
19 Jun 2018
School
Department
Course
Professor
The Polygraph Technique
Physiological measures have been used in an attempt to detect deception.
E.g., Chinese forced suspects to chew dry rice powder and spit it out and if
the powder was dry, they would be accused of lying.
○
-
Premise for polygraph: deception is associated with physiological change.
-
Origins of modern polygraphy - 1917
William Marston, Harvard Psychologist/Lawyer
○
Developed systolic blood pressure test and attempted to use this
response as evidence for a person's innocence.
○
Testimony was rejected by courts in Frye v. United States because they
felt the test had not gained acceptance by the scientific community.
○
-
Polygraph: a device for recording an individual's autonomic nervous system
response.
Measurement devices are attached to the upper cheat and abdomen to
measure breathing.
○
Amount of sweat is measured by attaching electrodes to the fingertips.
Sweat changes the conductance of the skin.
○
HR is measured by a partially inflated blood pressure cuff attached to an
arm.
○
-
Polygraph training is provided by the Canadian Police College - 12-week
intensive course that covres the various techniques, interviewing practice and
scoring for police officers.
-
Applications of the Polygraph
Police use the to help in criminal investigations.
-
May ask a suspect to take a polygraph test as a means to resolve the case -- if
the suspect fails the test, that person may be pressured to confess.
-
May ask alleged victims to take a polygraph test to verify the claims of the
insured (rare).
-
Recently, polygraphs have been used in the US to asses and monitor sexual
offenders on probation.
-
Polygraph disclosure tests: polygraph tests that are used to uncover
information about an offender's past behaviour.
Some sexual offender treatment programs require sexual offenders to
take a polygraph to help uncover undetected offences.
○
Bourke et al (2015): Polygraphed 127 sexual offenders with no official
history of hands-on offending.
Prior to polygraph, 5% admitted to sexual abusing a child.
§
During the polygraph, 53% disclosed about hands-on sexual abuse.
§
○
Used to determine whether the offender is violating the conditions of
probation or test for evidence of risky behaviour.
○
-
Used to be used for periodic testing of employees - trying to identify those
engaging in theft or using drugs at work.
Also used for screening purposes.
○
Employee Polygraph Protection Act of 1988 stopped this.
○
-
But some governmental agencies in the US and Canada still use it as a general
screening tool.
E.g., some police departments and CSIS require applicants to take
polygraph tests
○
-
Types of Polygraph Tests
Comparison Question Test:
Comparison Question Test: A type of polygraph test that includes irrelevant
questions that are unrelated to the crime, relevant questions concerning the
crime being investigated, and comparison questions concerning the person's
honest and past history prior the event being investigated.
-
Basic Outline:
(1) Examiner becomes familiar with the case.
○
(2) Examiner meets with the suspect and conducts a pretest interview in
which the suspect is asked about the offense.
Examiner uses this info to develop a series of yes/no questions.
§
○
(3) Examiner connects the suspect to the polygraph and measures the
suspect's physiological response to the questions which are repeated 3-5
times in different order.
Examiner scores the physiological responses and ends the CQT with
a post-test interview in which the test results are discussed.
§
○
-
Pre-test is critical -- allows the examiner to develop the comparison questions,
learn about the background of the suspect and attempts to convince the
suspect of the accuracy of the polygraph.
E.g., deck of cards trick
○
-
Types of questions:
Irrelevant Questions -- referring to the respondent's identity or personal
background; used as a baseline.
○
Relevant questions -- deal with the crime being investigated.
○
Comparison questions -- aka control questions; designed to be
emotionally arousing for all respondents and typically focus on the
person's honest and past history prior to the event being investigated.
○
-
Relevant and comparison questions are designed to establish guilt or innocence.
Examiners try to detect deception by comparing reactions to the relevant
and comparisons questions.
○
Guilty = react more to relevant questions
○
Innocent = react more to comparison questions
Innocent people know they are telling the truth about the relevant
question, so they will react more strongly to general questions
about their honesty and past history.
§
○
-
Examiners in the past used global scoring - incorporating all available
information - to make decisions about guilt.
-
Most examiners now numerically score the charts to ensure that decisions are
based solely on the physiological responses.
-
Possible outcomes: truthful, deceptive or inconclusive
During post-test, examiner tells the suspect the outcome and if the
outcome is deceptive, the examiner attempts to obtain a confession.
○
-
Psychologists have questioned the underlying rationale of the CQT.
Guilty people might respond more to comparison questions because they
are novel or they have other crimes to hide.
○
Innocent people might respond more to relevant questions because they
are upset about being falsely accused.
○
-
Concealed Information Test
Concealed Information Test: a type of polygraph test designed to determine if
the person knows details about a crime.
-
Developed by Lykken (1960)
-
Originally called the Guilty Knowledge Test.
-
Does not assess deception, but instead seeks to determine whether the suspect
knows details about a crime that only the person who committed the crime
would know.
-
Multiple choice questions -- each has one correct option (often called the
critical option) and four options that are foils.
-
Guilty person is assumed to display a larger physiological response to the
correct option than to the incorrect options.
-
Innocent person will show the same physiological response to all options.
-
Logic -- people will respond more strongly to information they recognize as
distinctive or important than to unimportant information.
-
Only works if the suspect actually remembers the details of the crime.
-
Most common physiological response measured when administering the CIT is
palmar sweating.
-
Used regularly in Israel and Japan.
-
Reasons for lack of acceptance:
Examiners believe in the accuracy of the CQT which is simpler.
○
Crime details can't be released in media.
○
-
Validity of Polygraph Techniques
Types of Studies: How is the accuracy of polygraph tests assessed?
Accuracy is determined under the ideal circumstances by presenting
information known to be true and false to individuals and measuring their
physiological responses.
-
Laboratory studies:
Volunteers stimulate criminal behaviour -- mock crimes.
○
Advantages:
The experimenter knows ground truth.
§
Ground truth: as applied to polygraph research, the knowledge of
whether the person is actually guilty or innocent.
§
They can also compare the merits of different types of the
polygraph exams and control for variables.
§
○
Disadvantages:
Large motivational and emotional differences between volunteers
in lab studies and actual suspects in real-life situations.
§
Limited application to real life.
§
Guilt participant can't be ethically given strong incentives to "beat"
the polygraph - both parties have little fear of "failing"
§
○
-
Field studies
Involve real-life situations and actual criminal suspects with actual
polygraph examinations.
○
Compare the accuracy of original examiners to blind evaluators.
Originals - conduct the actual evaluation.
§
Blind - provided with only the original charts and given no info
about the suspect or the case.
§
○
Patrick and Iacono (1991):
Although polygraph examiners are taught to ignore the cues from
case and suspect, this study found that they're still significantly
influenced by them.
§
○
Disadvantage:
Cannot establish ground truth (even with judicial outcomes and
confessions which are both problematic).
§
○
-
Polygraph Tests: Accurate or Not?
Accuracy of the polygraph for detecting lies is debatable.
-
Problems with relying on mock-crime scenarios to estimate real-life accuracy.
-
CQT Accuracy:
Most studies have used confessions to classify suspects of guilty or
innocent -- problematic because confessions are problematic.
Even more problematic for innocent suspects (accuracy rates
ranging from 55-78%)
§
9-24% of innocent suspects were falsely identified as guilty.
§
Suggests that the premise underlying CQT doesn't apply to all
suspects.
§
○
-
CIT Accuracy:
Mock-crime studies indicate it's effect at identifying innocent participants
(hit rate 95%) and slight less effective at identifying innocent participants
(hit rate 76-85%)
○
Correct outcomes better in studies that included motives to succeed,
verbal response to alternatives, five or more questions.
○
Field studies:
Elaad (1990): found tht 98% of innocent suspects were correctly
classified, but only 42% of guilty suspects were correctly classified.
§
Elaad, Ginton and Jungman (1992): measured respitation and skin
conductance and found that 94% of innocent and 76% of guilty
suspects were correctly classified.
§
○
-
CIT vulnerable to false-negative errors.
-
CQT is vulnerable to false-positive errors.
-
Can the Guilty Learn to Beat the Polygraph?
Countermeasures: as applied to polygraph research, techniques used to try to
conceal guilt.
-
Can people use countermeasures?
-
Honts, Raskin, and Kircher (1994):
Showed that 30 mins of instruction on the rationale underlying CQT was
sufficient for people to learn to escape detection in a mock-crime study.
○
Physical and mental countermeasures work -- 50% of guilty people beat
the test.
○
Examiners couldn't accurately detect which participants had used the
countermeasures.
○
-
Iacono, Cerri, Patrick and Fleming (1992):
Investigated whether anti-anxiety drugs would allow guilty subjects to
appear innocent on the CIT.
○
None of the drugs had an effect on CIT.
○
Polygraph examiner was able to identify 90% of the participants receiving
drugs.
○
-
Scientific Opinion
Most scientists are skeptical about the rationale underlying the CQT and its
accuracy.
-
Public isn't very supportive of the polygraph and its use in the courts.
-
But the public is more positive about the accuracy of the polygraph.
-
US NRC panel of scientists to review the validity of the polygraph.
"The theoretical rationale for the polygraph is quite weak, especially in
terms of differential fear, arousal, or other emotional states that are
triggered in response to relevant and comparison questions."
○
-
Despite scientists' negative view of it, the CQT is still used by law enforcement
as an investigative tool.
-
Admissibility of Polygraph Evidence
Polygraph results first submitted as evidence in court in the United States in
Frye v. United States (1923).
James Frye was denied the opportunity to have the results of a polygraph
test conducted by William Marston admitted as evidence.
○
-
A technique must obtain "general acceptance" by the relevant scientific
community before it can be admitted as evidence.
-
Not admissible in Canadian Courts as ruled in R. v. Beland (1987).
Referred to the polygraph as being falsely imbued with the "mystique of
science"
○
-
Brain-Based Deception Research
Event-related brain potentials (ERPs): brain activity measured by placing
electrodes on the scalp and by recording electrical patterns related to
presentation of a stimulus.
-
ERP's reflect underlying electrical activity in the cerebral cortex.
-
P300: type of ERP that occurs in response to stimuli that occur infrequently.
-
When using CIT, guilty suspects should respond to crime-relevant events with a
large P300 response compared to non-crime-relevant events.
-
Resistant to manipulation.
-
Farwell and Donchin (1991): studied the use of the P300 to detect the presence
of guilty knowledge.
Experiment 1: 18/20 guilty people correctly identified, 17/20 innocent
people correctly identified.
○
Experiment 2: 4/4 guilty people were correctly classified, 3/4 innocent
people correctly identified.
○
Limitations:
Guilty people reviewed case details right before test.
§
No aversive consequences linked to performance in the study.
§
Sample size too small.
§
○
-
Abootalebi et al (2006):
Lower detection rates than previously reported - 74-80% correct
identification.
○
-
Farwel (2012): P300-MERMER
Longer ERP wave form.
○
Claims this brainwave response is a more accurate measure of concealed
knowledge in complex tasks.
○
-
fMRI: measures the cerebral blood flow (a marker of neurological activity) in
different areas of the brain.
-
Used to determine which areas of the brain are associated with deception in
different paradigms.
-
Lie conditions produce greater activation in the prefrontal and anterior
cingulate regions as compared to truth conditions.
-
Responses can be detected at accuracies around 90%.
-
Ganis et al (2011): whether a simple cover movement would impact accuracy of
the fMRI in the concealing information paradigm.
Without countermeasure - 100% accuracy
○
With countermeasure - 33%
○
-
Limitations - how well this applies to real-life needs to be investigated.
-
Most scientists feel that it is premature to use fMRI to detect deception and the
results should not be admissible to court.
-
Concern that brain-imaging evidence may have a powerful influence on juror
decision making.
-
Simply seeing brain images makes people believe that scientific results are more
valid compared to when other images are presented.
-
McCabe, Castel and Rhodes (2011): examined the influence of evidence from
the polygraph, fMRI detection, or thermal imaging on the verdicts in a mock
juror trial.
But if expert testimony questioned the validity of fMRI lie detection, the
number of guilty verdicts was reduced to a similar level as in other
conditions.
○
-
Harrington v. State (2003):
Terry Harrington, a man convicted of murder, attempted to use the
results of brain-based deception testing to prove his innocence.
○
Lack of P300 response to crime-relevant details.
○
Prominent P300 response to alibi-relevant details.
○
Entered as evidence, but the judge relied on other evidence to overturn
the murder conviction.
○
-
Verbal and Nonverbal Behaviour Cues to Lying
North Americans tell ~ 1-2 lies per day.
-
Small number of people are prolific liars.
-
Most common method of deception detection.
-
Underlying assumption: the act of deception produces a physiological change
compared with telling the truth.
-
It is more difficult for people to control aspects of their nonverbal behaviour
than their verbal behaviour.
-
Typical experiment:
One group of participants - message source - told to provide either true
or deceptive messages.
○
Another group tasked with determining if the message source is truthful
or deceptive.
People who were told to focus on the message source's tone of
voice were more successful than those given no instruction.
§
○
-
Ekman and Friesen (1974):
Showed student nurses a film of an ocean scene and videotaped them
describing what they were seeing and how they felt.
○
They also watched gruesome medical training film and were videotaped
while pretending the film they were watching was pleasant.
Motivation -- told that in order to be successful in nursing, they had
to be able to mask their feelings.
§
○
Results
Nurses focused on controlling their facial expressions when trying
to lie.
§
Observers were better able to detect lying when shown a video
tape of the nurses bodies than of their faces.
§
○
-
Nonverbal behaviours (gaze aversion, smiling and self-manipulation) are not
reliable indicators of deception.
-
If is a liar is not feeling excited, scared or guilty or when the lie is easy to
fabricate, behavioural cues will not be present.
-
DePaulo, Kashy, Kirkendol, Wyer and Epstein (1996):
College students and community members practice deception daily.
○
Most deception not serious - participants reported they were not worried
about getting caught.
○
Lies about opinions, feelings, achievements, reasons for doing things, and
possessions.
○
Most lies for psychological reasons (e.g., protecting them from
embarrassment).
○
-
Ekman (1992):
Hypothesized that when people are attempting to conceal an emotion,
the true emotion may be manifest as a microfacial expression.
○
Microfacial expression: brief facial expressions reflecting true emotions
the person is experiencing.
○
US has been training security officers at airports to use this technique.
○
-
Matsumoto, Hwang, Skinner, and Frank (2011):
Recommend that investigators pay attention to a suspect's facial
expressions when doing interrogations.
○
-
Strömwall, Hartwig, and Granhag (2006):
Explore the role of stress.
○
Created realistic deception scenarios that used experienced police
officers, long interrogations and suspects who were motive driven and
had adequate time to prepare their deception.
○
Liars felt more anxious and stressed compared to truth-tellers.
○
No differences in non-verbal cues.
○
Verbal strategies - truth tellers claimed to "keep it real" while liars would
"keep it simple."
○
-
Potential Verbal and Nonverbal Characteristics of Deception
Verbal Characteristics
Speech fillers ("ah" or "um")
○
Speech errors
○
Pitch of voice (pitch changes)
○
Rate of speech
○
Speech pauses
○
-
Nonverbal characteristics
Gaze aversion
○
Smiling
○
Blinking
○
Fidgeting
○
Illustrators
○
Hand or finger movements
○
Leg or foot movements
○
Body movements
○
Shrugs
○
Head movements
○
Shifting positions
○
-
Not all of these are valid indicators of deception.
-
Verb characteristic mostly strongly associated with deception = pitch
Liars speak in a higher-pitched voice.
○
-
Increased use of speech disturbances and a slower rate of speech found during
deception.
-
Verbal Cues to Lying
DePaulo et al (2003):
Most cues did not discriminate between liars and truth-tellers.
○
Liars provided fewer details than truth-tellers.
○
Liars told less compelling accounts.
Less likely to make sense, less engaging, less fluent.
§
○
Liars less cooperative and more nervous/tense.
○
Truth-tellers were more likely to spontaneously correct their stories and
more likely to admit a lack of memory.
○
Deception cues were easier to detect when liars were motivated to lie or
attempting to cover up a personal failing/transgression.
○
-
Adams and Harpster (2008): Can you detect a killer from a 911 call?
Innocent callers were more likely to make requests for help for the victim,
to correct misperceptions, to be rude and demanding of immediate
assistance and to cooperate with the 911 operator.
Considerable emotion in voices and spoke quickly.
§
○
Guilty callers were more likely to provide irrelevant details, blame or
insult the victim, state that the victim was dead, be polite and patient,
with little emotion in their voices.
○
-
Are Some People Better at Detecting Deception?
Ability to detect deception is only slightly better than chance.
-
Aamodt and Custer (2006):
Accuracy rate for detecting deception for "professional lie catchers" was
55.5%.
○
Accuracy rate for students and citizens 54.2%.
○
Basically as good as guessing.
○
-
Bond and DePaulo (2006):
Found no differences in the abilities of experts and non-experts when it
came to lie detection.
○
-
Poor performance explained …
(1) People tend to rely on behaviours that lack predictive validity (e.g., eye
gaze and fidgeting)
○
(2) Most people have a truth bias.
Truth bias: the tendency of people to judge more messages as
truthful than deceptive.
§
○
(3) There are only small differences between liars and truth-tellers.
○
-
O'Sullivan and Ekman (2004):
Identified "wizards" of deception detection.
○
29/12000 professionals were extremely accurate (90% accuracy of
detecting lies about opinions, 80% accurate at detecting lies about a mock
crime and emotions)
○
This method was critiqued and people think that there still are no such
wizards.
○
-
O'Sullivan and Ekman (1991):
Only US Secret Service agents were better than chance at lie detection.
○
1/2 were 80% accurate or greater.
○
The most accurate were those who relied on multiple cues to assess
credibility rather than on any one cue.
○
-
Vrji (2000):
67% accuracy for detecting truths
○
44% accuracy for detecting lies
○
-
POINT: I most studies, truthful messages were identified with more accuracy
than deceptive messages.
Truthfulness bias
○
Not good at detecting lies because they rely on the wrong cues.
○
Police better at detecting high-stakes lies (but still make many errors).
○
-
DePaulo and Pfeifer (1986):
Deception detection of university students, new police offices and
experienced police officers.
○
None of the groups were better than the others.
○
Experienced police officers were more confident in their decisions.
○
-
POINT: Neither level of experience nor confidence in deception-detection ability
is associated with accuracy rates.
-
Bond and DePaulo (2008):
No specific traits related to detecting deception in others.
○
"deception judgments depend more on the liar than the judge"
○
-
Is It Possible to Improve Professionals' Deception-Detection Abilities?
Few studies
-
Looks like you can improve abilities with training.
-
Porter, Woodworth and Birt (2000):
Two-day workshop focusing on myth dissolution, knowledge of
behavioural cues to deception, and performance feedback increased
accuracy to 76.7%
○
-
Porter, Juodis, ten Brinke, Klein, and Wilson (2010):
Three-hour training session increased the detection accuracy of health
care professionals to 60.7%
○
-
Masip, Alonso, Garrido,and Herreror (2008):
Recommended that training programs should focus on teaching deception
cues and truthfulness cues to counteract the tendency for professionals
to judge people as deceptive.
○
-
Chapter 4: Deception (pg. 93-116)
Saturday, February 3, 2018
5:23 PM
The Polygraph Technique
Physiological measures have been used in an attempt to detect deception.
E.g., Chinese forced suspects to chew dry rice powder and spit it out and if
the powder was dry, they would be accused of lying.
○
-
Premise for polygraph: deception is associated with physiological change.
-
Origins of modern polygraphy - 1917
William Marston, Harvard Psychologist/Lawyer
○
Developed systolic blood pressure test and attempted to use this
response as evidence for a person's innocence.
○
Testimony was rejected by courts in Frye v. United States because they
felt the test had not gained acceptance by the scientific community.
○
-
Polygraph: a device for recording an individual's autonomic nervous system
response.
Measurement devices are attached to the upper cheat and abdomen to
measure breathing.
○
Amount of sweat is measured by attaching electrodes to the fingertips.
Sweat changes the conductance of the skin.
○
HR is measured by a partially inflated blood pressure cuff attached to an
arm.
○
-
Polygraph training is provided by the Canadian Police College - 12-week
intensive course that covres the various techniques, interviewing practice and
scoring for police officers.
-
Applications of the Polygraph
Police use the to help in criminal investigations.
-
May ask a suspect to take a polygraph test as a means to resolve the case -- if
the suspect fails the test, that person may be pressured to confess.
-
May ask alleged victims to take a polygraph test to verify the claims of the
insured (rare).
-
Recently, polygraphs have been used in the US to asses and monitor sexual
offenders on probation.
-
Polygraph disclosure tests: polygraph tests that are used to uncover
information about an offender's past behaviour.
Some sexual offender treatment programs require sexual offenders to
take a polygraph to help uncover undetected offences.
○
Bourke et al (2015): Polygraphed 127 sexual offenders with no official
history of hands-on offending.
Prior to polygraph, 5% admitted to sexual abusing a child.
§
During the polygraph, 53% disclosed about hands-on sexual abuse.
§
○
Used to determine whether the offender is violating the conditions of
probation or test for evidence of risky behaviour.
○
-
Used to be used for periodic testing of employees - trying to identify those
engaging in theft or using drugs at work.
Also used for screening purposes.
○
Employee Polygraph Protection Act of 1988 stopped this.
○
-
But some governmental agencies in the US and Canada still use it as a general
screening tool.
E.g., some police departments and CSIS require applicants to take
polygraph tests
○
-
Types of Polygraph Tests
Comparison Question Test:
Comparison Question Test: A type of polygraph test that includes irrelevant
questions that are unrelated to the crime, relevant questions concerning the
crime being investigated, and comparison questions concerning the person's
honest and past history prior the event being investigated.
-
Basic Outline:
(1) Examiner becomes familiar with the case.
○
(2) Examiner meets with the suspect and conducts a pretest interview in
which the suspect is asked about the offense.
Examiner uses this info to develop a series of yes/no questions.
§
○
(3) Examiner connects the suspect to the polygraph and measures the
suspect's physiological response to the questions which are repeated 3-5
times in different order.
Examiner scores the physiological responses and ends the CQT with
a post-test interview in which the test results are discussed.
§
○
-
Pre-test is critical -- allows the examiner to develop the comparison questions,
learn about the background of the suspect and attempts to convince the
suspect of the accuracy of the polygraph.
E.g., deck of cards trick
○
-
Types of questions:
Irrelevant Questions -- referring to the respondent's identity or personal
background; used as a baseline.
○
Relevant questions -- deal with the crime being investigated.
○
Comparison questions -- aka control questions; designed to be
emotionally arousing for all respondents and typically focus on the
person's honest and past history prior to the event being investigated.
○
-
Relevant and comparison questions are designed to establish guilt or innocence.
Examiners try to detect deception by comparing reactions to the relevant
and comparisons questions.
○
Guilty = react more to relevant questions
○
Innocent = react more to comparison questions
Innocent people know they are telling the truth about the relevant
question, so they will react more strongly to general questions
about their honesty and past history.
§
○
-
Examiners in the past used global scoring - incorporating all available
information - to make decisions about guilt.
-
Most examiners now numerically score the charts to ensure that decisions are
based solely on the physiological responses.
-
Possible outcomes: truthful, deceptive or inconclusive
During post-test, examiner tells the suspect the outcome and if the
outcome is deceptive, the examiner attempts to obtain a confession.
○
-
Psychologists have questioned the underlying rationale of the CQT.
Guilty people might respond more to comparison questions because they
are novel or they have other crimes to hide.
○
Innocent people might respond more to relevant questions because they
are upset about being falsely accused.
○
-
Concealed Information Test
Concealed Information Test: a type of polygraph test designed to determine if
the person knows details about a crime.
-
Developed by Lykken (1960)
-
Originally called the Guilty Knowledge Test.
-
Does not assess deception, but instead seeks to determine whether the suspect
knows details about a crime that only the person who committed the crime
would know.
-
Multiple choice questions -- each has one correct option (often called the
critical option) and four options that are foils.
-
Guilty person is assumed to display a larger physiological response to the
correct option than to the incorrect options.
-
Innocent person will show the same physiological response to all options.
-
Logic -- people will respond more strongly to information they recognize as
distinctive or important than to unimportant information.
-
Only works if the suspect actually remembers the details of the crime.
-
Most common physiological response measured when administering the CIT is
palmar sweating.
-
Used regularly in Israel and Japan.
-
Reasons for lack of acceptance:
Examiners believe in the accuracy of the CQT which is simpler.
○
Crime details can't be released in media.
○
-
Validity of Polygraph Techniques
Types of Studies: How is the accuracy of polygraph tests assessed?
Accuracy is determined under the ideal circumstances by presenting
information known to be true and false to individuals and measuring their
physiological responses.
-
Laboratory studies:
Volunteers stimulate criminal behaviour -- mock crimes.
○
Advantages:
The experimenter knows ground truth.
§
Ground truth: as applied to polygraph research, the knowledge of
whether the person is actually guilty or innocent.
§
They can also compare the merits of different types of the
polygraph exams and control for variables.
§
○
Disadvantages:
Large motivational and emotional differences between volunteers
in lab studies and actual suspects in real-life situations.
§
Limited application to real life.
§
Guilt participant can't be ethically given strong incentives to "beat"
the polygraph - both parties have little fear of "failing"
§
○
-
Field studies
Involve real-life situations and actual criminal suspects with actual
polygraph examinations.
○
Compare the accuracy of original examiners to blind evaluators.
Originals - conduct the actual evaluation.
§
Blind - provided with only the original charts and given no info
about the suspect or the case.
§
○
Patrick and Iacono (1991):
Although polygraph examiners are taught to ignore the cues from
case and suspect, this study found that they're still significantly
influenced by them.
§
○
Disadvantage:
Cannot establish ground truth (even with judicial outcomes and
confessions which are both problematic).
§
○
-
Polygraph Tests: Accurate or Not?
Accuracy of the polygraph for detecting lies is debatable.
-
Problems with relying on mock-crime scenarios to estimate real-life accuracy.
-
CQT Accuracy:
Most studies have used confessions to classify suspects of guilty or
innocent -- problematic because confessions are problematic.
Even more problematic for innocent suspects (accuracy rates
ranging from 55-78%)
§
9-24% of innocent suspects were falsely identified as guilty.
§
Suggests that the premise underlying CQT doesn't apply to all
suspects.
§
○
-
CIT Accuracy:
Mock-crime studies indicate it's effect at identifying innocent participants
(hit rate 95%) and slight less effective at identifying innocent participants
(hit rate 76-85%)
○
Correct outcomes better in studies that included motives to succeed,
verbal response to alternatives, five or more questions.
○
Field studies:
Elaad (1990): found tht 98% of innocent suspects were correctly
classified, but only 42% of guilty suspects were correctly classified.
§
Elaad, Ginton and Jungman (1992): measured respitation and skin
conductance and found that 94% of innocent and 76% of guilty
suspects were correctly classified.
§
○
-
CIT vulnerable to false-negative errors.
-
CQT is vulnerable to false-positive errors.
-
Can the Guilty Learn to Beat the Polygraph?
Countermeasures: as applied to polygraph research, techniques used to try to
conceal guilt.
-
Can people use countermeasures?
-
Honts, Raskin, and Kircher (1994):
Showed that 30 mins of instruction on the rationale underlying CQT was
sufficient for people to learn to escape detection in a mock-crime study.
○
Physical and mental countermeasures work -- 50% of guilty people beat
the test.
○
Examiners couldn't accurately detect which participants had used the
countermeasures.
○
-
Iacono, Cerri, Patrick and Fleming (1992):
Investigated whether anti-anxiety drugs would allow guilty subjects to
appear innocent on the CIT.
○
None of the drugs had an effect on CIT.
○
Polygraph examiner was able to identify 90% of the participants receiving
drugs.
○
-
Scientific Opinion
Most scientists are skeptical about the rationale underlying the CQT and its
accuracy.
-
Public isn't very supportive of the polygraph and its use in the courts.
-
But the public is more positive about the accuracy of the polygraph.
-
US NRC panel of scientists to review the validity of the polygraph.
"The theoretical rationale for the polygraph is quite weak, especially in
terms of differential fear, arousal, or other emotional states that are
triggered in response to relevant and comparison questions."
○
-
Despite scientists' negative view of it, the CQT is still used by law enforcement
as an investigative tool.
-
Admissibility of Polygraph Evidence
Polygraph results first submitted as evidence in court in the United States in
Frye v. United States (1923).
James Frye was denied the opportunity to have the results of a polygraph
test conducted by William Marston admitted as evidence.
○
-
A technique must obtain "general acceptance" by the relevant scientific
community before it can be admitted as evidence.
-
Not admissible in Canadian Courts as ruled in R. v. Beland (1987).
Referred to the polygraph as being falsely imbued with the "mystique of
science"
○
-
Brain-Based Deception Research
Event-related brain potentials (ERPs): brain activity measured by placing
electrodes on the scalp and by recording electrical patterns related to
presentation of a stimulus.
-
ERP's reflect underlying electrical activity in the cerebral cortex.
-
P300: type of ERP that occurs in response to stimuli that occur infrequently.
-
When using CIT, guilty suspects should respond to crime-relevant events with a
large P300 response compared to non-crime-relevant events.
-
Resistant to manipulation.
-
Farwell and Donchin (1991): studied the use of the P300 to detect the presence
of guilty knowledge.
Experiment 1: 18/20 guilty people correctly identified, 17/20 innocent
people correctly identified.
○
Experiment 2: 4/4 guilty people were correctly classified, 3/4 innocent
people correctly identified.
○
Limitations:
Guilty people reviewed case details right before test.
§
No aversive consequences linked to performance in the study.
§
Sample size too small.
§
○
-
Abootalebi et al (2006):
Lower detection rates than previously reported - 74-80% correct
identification.
○
-
Farwel (2012): P300-MERMER
Longer ERP wave form.
○
Claims this brainwave response is a more accurate measure of concealed
knowledge in complex tasks.
○
-
fMRI: measures the cerebral blood flow (a marker of neurological activity) in
different areas of the brain.
-
Used to determine which areas of the brain are associated with deception in
different paradigms.
-
Lie conditions produce greater activation in the prefrontal and anterior
cingulate regions as compared to truth conditions.
-
Responses can be detected at accuracies around 90%.
-
Ganis et al (2011): whether a simple cover movement would impact accuracy of
the fMRI in the concealing information paradigm.
Without countermeasure - 100% accuracy
○
With countermeasure - 33%
○
-
Limitations - how well this applies to real-life needs to be investigated.
-
Most scientists feel that it is premature to use fMRI to detect deception and the
results should not be admissible to court.
-
Concern that brain-imaging evidence may have a powerful influence on juror
decision making.
-
Simply seeing brain images makes people believe that scientific results are more
valid compared to when other images are presented.
-
McCabe, Castel and Rhodes (2011): examined the influence of evidence from
the polygraph, fMRI detection, or thermal imaging on the verdicts in a mock
juror trial.
But if expert testimony questioned the validity of fMRI lie detection, the
number of guilty verdicts was reduced to a similar level as in other
conditions.
○
-
Harrington v. State (2003):
Terry Harrington, a man convicted of murder, attempted to use the
results of brain-based deception testing to prove his innocence.
○
Lack of P300 response to crime-relevant details.
○
Prominent P300 response to alibi-relevant details.
○
Entered as evidence, but the judge relied on other evidence to overturn
the murder conviction.
○
-
Verbal and Nonverbal Behaviour Cues to Lying
North Americans tell ~ 1-2 lies per day.
-
Small number of people are prolific liars.
-
Most common method of deception detection.
-
Underlying assumption: the act of deception produces a physiological change
compared with telling the truth.
-
It is more difficult for people to control aspects of their nonverbal behaviour
than their verbal behaviour.
-
Typical experiment:
One group of participants - message source - told to provide either true
or deceptive messages.
○
Another group tasked with determining if the message source is truthful
or deceptive.
People who were told to focus on the message source's tone of
voice were more successful than those given no instruction.
§
○
-
Ekman and Friesen (1974):
Showed student nurses a film of an ocean scene and videotaped them
describing what they were seeing and how they felt.
○
They also watched gruesome medical training film and were videotaped
while pretending the film they were watching was pleasant.
Motivation -- told that in order to be successful in nursing, they had
to be able to mask their feelings.
§
○
Results
Nurses focused on controlling their facial expressions when trying
to lie.
§
Observers were better able to detect lying when shown a video
tape of the nurses bodies than of their faces.
§
○
-
Nonverbal behaviours (gaze aversion, smiling and self-manipulation) are not
reliable indicators of deception.
-
If is a liar is not feeling excited, scared or guilty or when the lie is easy to
fabricate, behavioural cues will not be present.
-
DePaulo, Kashy, Kirkendol, Wyer and Epstein (1996):
College students and community members practice deception daily.
○
Most deception not serious - participants reported they were not worried
about getting caught.
○
Lies about opinions, feelings, achievements, reasons for doing things, and
possessions.
○
Most lies for psychological reasons (e.g., protecting them from
embarrassment).
○
-
Ekman (1992):
Hypothesized that when people are attempting to conceal an emotion,
the true emotion may be manifest as a microfacial expression.
○
Microfacial expression: brief facial expressions reflecting true emotions
the person is experiencing.
○
US has been training security officers at airports to use this technique.
○
-
Matsumoto, Hwang, Skinner, and Frank (2011):
Recommend that investigators pay attention to a suspect's facial
expressions when doing interrogations.
○
-
Strömwall, Hartwig, and Granhag (2006):
Explore the role of stress.
○
Created realistic deception scenarios that used experienced police
officers, long interrogations and suspects who were motive driven and
had adequate time to prepare their deception.
○
Liars felt more anxious and stressed compared to truth-tellers.
○
No differences in non-verbal cues.
○
Verbal strategies - truth tellers claimed to "keep it real" while liars would
"keep it simple."
○
-
Potential Verbal and Nonverbal Characteristics of Deception
Verbal Characteristics
Speech fillers ("ah" or "um")
○
Speech errors
○
Pitch of voice (pitch changes)
○
Rate of speech
○
Speech pauses
○
-
Nonverbal characteristics
Gaze aversion
○
Smiling
○
Blinking
○
Fidgeting
○
Illustrators
○
Hand or finger movements
○
Leg or foot movements
○
Body movements
○
Shrugs
○
Head movements
○
Shifting positions
○
-
Not all of these are valid indicators of deception.
-
Verb characteristic mostly strongly associated with deception = pitch
Liars speak in a higher-pitched voice.
○
-
Increased use of speech disturbances and a slower rate of speech found during
deception.
-
Verbal Cues to Lying
DePaulo et al (2003):
Most cues did not discriminate between liars and truth-tellers.
○
Liars provided fewer details than truth-tellers.
○
Liars told less compelling accounts.
Less likely to make sense, less engaging, less fluent.
§
○
Liars less cooperative and more nervous/tense.
○
Truth-tellers were more likely to spontaneously correct their stories and
more likely to admit a lack of memory.
○
Deception cues were easier to detect when liars were motivated to lie or
attempting to cover up a personal failing/transgression.
○
-
Adams and Harpster (2008): Can you detect a killer from a 911 call?
Innocent callers were more likely to make requests for help for the victim,
to correct misperceptions, to be rude and demanding of immediate
assistance and to cooperate with the 911 operator.
Considerable emotion in voices and spoke quickly.
§
○
Guilty callers were more likely to provide irrelevant details, blame or
insult the victim, state that the victim was dead, be polite and patient,
with little emotion in their voices.
○
-
Are Some People Better at Detecting Deception?
Ability to detect deception is only slightly better than chance.
-
Aamodt and Custer (2006):
Accuracy rate for detecting deception for "professional lie catchers" was
55.5%.
○
Accuracy rate for students and citizens 54.2%.
○
Basically as good as guessing.
○
-
Bond and DePaulo (2006):
Found no differences in the abilities of experts and non-experts when it
came to lie detection.
○
-
Poor performance explained …
(1) People tend to rely on behaviours that lack predictive validity (e.g., eye
gaze and fidgeting)
○
(2) Most people have a truth bias.
Truth bias: the tendency of people to judge more messages as
truthful than deceptive.
§
○
(3) There are only small differences between liars and truth-tellers.
○
-
O'Sullivan and Ekman (2004):
Identified "wizards" of deception detection.
○
29/12000 professionals were extremely accurate (90% accuracy of
detecting lies about opinions, 80% accurate at detecting lies about a mock
crime and emotions)
○
This method was critiqued and people think that there still are no such
wizards.
○
-
O'Sullivan and Ekman (1991):
Only US Secret Service agents were better than chance at lie detection.
○
1/2 were 80% accurate or greater.
○
The most accurate were those who relied on multiple cues to assess
credibility rather than on any one cue.
○
-
Vrji (2000):
67% accuracy for detecting truths
○
44% accuracy for detecting lies
○
-
POINT: I most studies, truthful messages were identified with more accuracy
than deceptive messages.
Truthfulness bias
○
Not good at detecting lies because they rely on the wrong cues.
○
Police better at detecting high-stakes lies (but still make many errors).
○
-
DePaulo and Pfeifer (1986):
Deception detection of university students, new police offices and
experienced police officers.
○
None of the groups were better than the others.
○
Experienced police officers were more confident in their decisions.
○
-
POINT: Neither level of experience nor confidence in deception-detection ability
is associated with accuracy rates.
-
Bond and DePaulo (2008):
No specific traits related to detecting deception in others.
○
"deception judgments depend more on the liar than the judge"
○
-
Is It Possible to Improve Professionals' Deception-Detection Abilities?
Few studies
-
Looks like you can improve abilities with training.
-
Porter, Woodworth and Birt (2000):
Two-day workshop focusing on myth dissolution, knowledge of
behavioural cues to deception, and performance feedback increased
accuracy to 76.7%
○
-
Porter, Juodis, ten Brinke, Klein, and Wilson (2010):
Three-hour training session increased the detection accuracy of health
care professionals to 60.7%
○
-
Masip, Alonso, Garrido,and Herreror (2008):
Recommended that training programs should focus on teaching deception
cues and truthfulness cues to counteract the tendency for professionals
to judge people as deceptive.
○
-
Chapter 4: Deception (pg. 93-116)
Saturday, February 3, 2018 5:23 PM
The Polygraph Technique
Physiological measures have been used in an attempt to detect deception.
E.g., Chinese forced suspects to chew dry rice powder and spit it out and if
the powder was dry, they would be accused of lying.
○
-
Premise for polygraph: deception is associated with physiological change.
-
Origins of modern polygraphy - 1917
William Marston, Harvard Psychologist/Lawyer
○
Developed systolic blood pressure test and attempted to use this
response as evidence for a person's innocence.
○
Testimony was rejected by courts in Frye v. United States because they
felt the test had not gained acceptance by the scientific community.
○
-
Polygraph: a device for recording an individual's autonomic nervous system
response.
Measurement devices are attached to the upper cheat and abdomen to
measure breathing.
○
Amount of sweat is measured by attaching electrodes to the fingertips.
Sweat changes the conductance of the skin.
○
HR is measured by a partially inflated blood pressure cuff attached to an
arm.
○
-
Polygraph training is provided by the Canadian Police College - 12-week
intensive course that covres the various techniques, interviewing practice and
scoring for police officers.
-
Applications of the Polygraph
Police use the to help in criminal investigations.
-
May ask a suspect to take a polygraph test as a means to resolve the case -- if
the suspect fails the test, that person may be pressured to confess.
-
May ask alleged victims to take a polygraph test to verify the claims of the
insured (rare).
-
Recently, polygraphs have been used in the US to asses and monitor sexual
offenders on probation.
-
Polygraph disclosure tests: polygraph tests that are used to uncover
information about an offender's past behaviour.
Some sexual offender treatment programs require sexual offenders to
take a polygraph to help uncover undetected offences.
○
Bourke et al (2015): Polygraphed 127 sexual offenders with no official
history of hands-on offending.
Prior to polygraph, 5% admitted to sexual abusing a child.
§
During the polygraph, 53% disclosed about hands-on sexual abuse.
§
○
Used to determine whether the offender is violating the conditions of
probation or test for evidence of risky behaviour.
○
-
Used to be used for periodic testing of employees - trying to identify those
engaging in theft or using drugs at work.
Also used for screening purposes.
○
Employee Polygraph Protection Act of 1988 stopped this.
○
-
But some governmental agencies in the US and Canada still use it as a general
screening tool.
E.g., some police departments and CSIS require applicants to take
polygraph tests
○
-
Types of Polygraph Tests
Comparison Question Test:
Comparison Question Test: A type of polygraph test that includes irrelevant
questions that are unrelated to the crime, relevant questions concerning the
crime being investigated, and comparison questions concerning the person's
honest and past history prior the event being investigated.
-
Basic Outline:
(1) Examiner becomes familiar with the case.
○
(2) Examiner meets with the suspect and conducts a pretest interview in
which the suspect is asked about the offense.
Examiner uses this info to develop a series of yes/no questions.
§
○
(3) Examiner connects the suspect to the polygraph and measures the
suspect's physiological response to the questions which are repeated 3-5
times in different order.
Examiner scores the physiological responses and ends the CQT with
a post-test interview in which the test results are discussed.
§
○
-
Pre-test is critical -- allows the examiner to develop the comparison questions,
learn about the background of the suspect and attempts to convince the
suspect of the accuracy of the polygraph.
E.g., deck of cards trick
○
-
Types of questions:
Irrelevant Questions -- referring to the respondent's identity or personal
background; used as a baseline.
○
Relevant questions -- deal with the crime being investigated.
○
Comparison questions -- aka control questions; designed to be
emotionally arousing for all respondents and typically focus on the
person's honest and past history prior to the event being investigated.
○
-
Relevant and comparison questions are designed to establish guilt or innocence.
Examiners try to detect deception by comparing reactions to the relevant
and comparisons questions.
○
Guilty = react more to relevant questions
○
Innocent = react more to comparison questions
Innocent people know they are telling the truth about the relevant
question, so they will react more strongly to general questions
about their honesty and past history.
§
○
-
Examiners in the past used global scoring - incorporating all available
information - to make decisions about guilt.
-
Most examiners now numerically score the charts to ensure that decisions are
based solely on the physiological responses.
-
Possible outcomes: truthful, deceptive or inconclusive
During post-test, examiner tells the suspect the outcome and if the
outcome is deceptive, the examiner attempts to obtain a confession.
○
-
Psychologists have questioned the underlying rationale of the CQT.
Guilty people might respond more to comparison questions because they
are novel or they have other crimes to hide.
○
Innocent people might respond more to relevant questions because they
are upset about being falsely accused.
○
-
Concealed Information Test
Concealed Information Test: a type of polygraph test designed to determine if
the person knows details about a crime.
-
Developed by Lykken (1960)
-
Originally called the Guilty Knowledge Test.
-
Does not assess deception, but instead seeks to determine whether the suspect
knows details about a crime that only the person who committed the crime
would know.
-
Multiple choice questions -- each has one correct option (often called the
critical option) and four options that are foils.
-
Guilty person is assumed to display a larger physiological response to the
correct option than to the incorrect options.
-
Innocent person will show the same physiological response to all options.
-
Logic -- people will respond more strongly to information they recognize as
distinctive or important than to unimportant information.
-
Only works if the suspect actually remembers the details of the crime.
-
Most common physiological response measured when administering the CIT is
palmar sweating.
-
Used regularly in Israel and Japan.
-
Reasons for lack of acceptance:
Examiners believe in the accuracy of the CQT which is simpler.
○
Crime details can't be released in media.
○
-
Validity of Polygraph Techniques
Types of Studies: How is the accuracy of polygraph tests assessed?
Accuracy is determined under the ideal circumstances by presenting
information known to be true and false to individuals and measuring their
physiological responses.
-
Laboratory studies:
Volunteers stimulate criminal behaviour -- mock crimes.
○
Advantages:
The experimenter knows ground truth.
§
Ground truth: as applied to polygraph research, the knowledge of
whether the person is actually guilty or innocent.
§
They can also compare the merits of different types of the
polygraph exams and control for variables.
§
○
Disadvantages:
Large motivational and emotional differences between volunteers
in lab studies and actual suspects in real-life situations.
§
Limited application to real life.
§
Guilt participant can't be ethically given strong incentives to "beat"
the polygraph - both parties have little fear of "failing"
§
○
-
Field studies
Involve real-life situations and actual criminal suspects with actual
polygraph examinations.
○
Compare the accuracy of original examiners to blind evaluators.
Originals - conduct the actual evaluation.
§
Blind - provided with only the original charts and given no info
about the suspect or the case.
§
○
Patrick and Iacono (1991):
Although polygraph examiners are taught to ignore the cues from
case and suspect, this study found that they're still significantly
influenced by them.
§
○
Disadvantage:
Cannot establish ground truth (even with judicial outcomes and
confessions which are both problematic).
§
○
-
Polygraph Tests: Accurate or Not?
Accuracy of the polygraph for detecting lies is debatable.
-
Problems with relying on mock-crime scenarios to estimate real-life accuracy.
-
CQT Accuracy:
Most studies have used confessions to classify suspects of guilty or
innocent -- problematic because confessions are problematic.
Even more problematic for innocent suspects (accuracy rates
ranging from 55-78%)
§
9-24% of innocent suspects were falsely identified as guilty.
§
Suggests that the premise underlying CQT doesn't apply to all
suspects.
§
○
-
CIT Accuracy:
Mock-crime studies indicate it's effect at identifying innocent participants
(hit rate 95%) and slight less effective at identifying innocent participants
(hit rate 76-85%)
○
Correct outcomes better in studies that included motives to succeed,
verbal response to alternatives, five or more questions.
○
Field studies:
Elaad (1990): found tht 98% of innocent suspects were correctly
classified, but only 42% of guilty suspects were correctly classified.
§
Elaad, Ginton and Jungman (1992): measured respitation and skin
conductance and found that 94% of innocent and 76% of guilty
suspects were correctly classified.
§
○
-
CIT vulnerable to false-negative errors.
-
CQT is vulnerable to false-positive errors.
-
Can the Guilty Learn to Beat the Polygraph?
Countermeasures: as applied to polygraph research, techniques used to try to
conceal guilt.
-
Can people use countermeasures?
-
Honts, Raskin, and Kircher (1994):
Showed that 30 mins of instruction on the rationale underlying CQT was
sufficient for people to learn to escape detection in a mock-crime study.
○
Physical and mental countermeasures work -- 50% of guilty people beat
the test.
○
Examiners couldn't accurately detect which participants had used the
countermeasures.
○
-
Iacono, Cerri, Patrick and Fleming (1992):
Investigated whether anti-anxiety drugs would allow guilty subjects to
appear innocent on the CIT.
○
None of the drugs had an effect on CIT.
○
Polygraph examiner was able to identify 90% of the participants receiving
drugs.
○
-
Scientific Opinion
Most scientists are skeptical about the rationale underlying the CQT and its
accuracy.
-
Public isn't very supportive of the polygraph and its use in the courts.
-
But the public is more positive about the accuracy of the polygraph.
-
US NRC panel of scientists to review the validity of the polygraph.
"The theoretical rationale for the polygraph is quite weak, especially in
terms of differential fear, arousal, or other emotional states that are
triggered in response to relevant and comparison questions."
○
-
Despite scientists' negative view of it, the CQT is still used by law enforcement
as an investigative tool.
-
Admissibility of Polygraph Evidence
Polygraph results first submitted as evidence in court in the United States in
Frye v. United States (1923).
James Frye was denied the opportunity to have the results of a polygraph
test conducted by William Marston admitted as evidence.
○
-
A technique must obtain "general acceptance" by the relevant scientific
community before it can be admitted as evidence.
-
Not admissible in Canadian Courts as ruled in R. v. Beland (1987).
Referred to the polygraph as being falsely imbued with the "mystique of
science"
○
-
Brain-Based Deception Research
Event-related brain potentials (ERPs): brain activity measured by placing
electrodes on the scalp and by recording electrical patterns related to
presentation of a stimulus.
-
ERP's reflect underlying electrical activity in the cerebral cortex.
-
P300: type of ERP that occurs in response to stimuli that occur infrequently.
-
When using CIT, guilty suspects should respond to crime-relevant events with a
large P300 response compared to non-crime-relevant events.
-
Resistant to manipulation.
-
Farwell and Donchin (1991): studied the use of the P300 to detect the presence
of guilty knowledge.
Experiment 1: 18/20 guilty people correctly identified, 17/20 innocent
people correctly identified.
○
Experiment 2: 4/4 guilty people were correctly classified, 3/4 innocent
people correctly identified.
○
Limitations:
Guilty people reviewed case details right before test.
§
No aversive consequences linked to performance in the study.
§
Sample size too small.
§
○
-
Abootalebi et al (2006):
Lower detection rates than previously reported - 74-80% correct
identification.
○
-
Farwel (2012): P300-MERMER
Longer ERP wave form.
○
Claims this brainwave response is a more accurate measure of concealed
knowledge in complex tasks.
○
-
fMRI: measures the cerebral blood flow (a marker of neurological activity) in
different areas of the brain.
-
Used to determine which areas of the brain are associated with deception in
different paradigms.
-
Lie conditions produce greater activation in the prefrontal and anterior
cingulate regions as compared to truth conditions.
-
Responses can be detected at accuracies around 90%.
-
Ganis et al (2011): whether a simple cover movement would impact accuracy of
the fMRI in the concealing information paradigm.
Without countermeasure - 100% accuracy
○
With countermeasure - 33%
○
-
Limitations - how well this applies to real-life needs to be investigated.
-
Most scientists feel that it is premature to use fMRI to detect deception and the
results should not be admissible to court.
-
Concern that brain-imaging evidence may have a powerful influence on juror
decision making.
-
Simply seeing brain images makes people believe that scientific results are more
valid compared to when other images are presented.
-
McCabe, Castel and Rhodes (2011): examined the influence of evidence from
the polygraph, fMRI detection, or thermal imaging on the verdicts in a mock
juror trial.
But if expert testimony questioned the validity of fMRI lie detection, the
number of guilty verdicts was reduced to a similar level as in other
conditions.
○
-
Harrington v. State (2003):
Terry Harrington, a man convicted of murder, attempted to use the
results of brain-based deception testing to prove his innocence.
○
Lack of P300 response to crime-relevant details.
○
Prominent P300 response to alibi-relevant details.
○
Entered as evidence, but the judge relied on other evidence to overturn
the murder conviction.
○
-
Verbal and Nonverbal Behaviour Cues to Lying
North Americans tell ~ 1-2 lies per day.
-
Small number of people are prolific liars.
-
Most common method of deception detection.
-
Underlying assumption: the act of deception produces a physiological change
compared with telling the truth.
-
It is more difficult for people to control aspects of their nonverbal behaviour
than their verbal behaviour.
-
Typical experiment:
One group of participants - message source - told to provide either true
or deceptive messages.
○
Another group tasked with determining if the message source is truthful
or deceptive.
People who were told to focus on the message source's tone of
voice were more successful than those given no instruction.
§
○
-
Ekman and Friesen (1974):
Showed student nurses a film of an ocean scene and videotaped them
describing what they were seeing and how they felt.
○
They also watched gruesome medical training film and were videotaped
while pretending the film they were watching was pleasant.
Motivation -- told that in order to be successful in nursing, they had
to be able to mask their feelings.
§
○
Results
Nurses focused on controlling their facial expressions when trying
to lie.
§
Observers were better able to detect lying when shown a video
tape of the nurses bodies than of their faces.
§
○
-
Nonverbal behaviours (gaze aversion, smiling and self-manipulation) are not
reliable indicators of deception.
-
If is a liar is not feeling excited, scared or guilty or when the lie is easy to
fabricate, behavioural cues will not be present.
-
DePaulo, Kashy, Kirkendol, Wyer and Epstein (1996):
College students and community members practice deception daily.
○
Most deception not serious - participants reported they were not worried
about getting caught.
○
Lies about opinions, feelings, achievements, reasons for doing things, and
possessions.
○
Most lies for psychological reasons (e.g., protecting them from
embarrassment).
○
-
Ekman (1992):
Hypothesized that when people are attempting to conceal an emotion,
the true emotion may be manifest as a microfacial expression.
○
Microfacial expression: brief facial expressions reflecting true emotions
the person is experiencing.
○
US has been training security officers at airports to use this technique.
○
-
Matsumoto, Hwang, Skinner, and Frank (2011):
Recommend that investigators pay attention to a suspect's facial
expressions when doing interrogations.
○
-
Strömwall, Hartwig, and Granhag (2006):
Explore the role of stress.
○
Created realistic deception scenarios that used experienced police
officers, long interrogations and suspects who were motive driven and
had adequate time to prepare their deception.
○
Liars felt more anxious and stressed compared to truth-tellers.
○
No differences in non-verbal cues.
○
Verbal strategies - truth tellers claimed to "keep it real" while liars would
"keep it simple."
○
-
Potential Verbal and Nonverbal Characteristics of Deception
Verbal Characteristics
Speech fillers ("ah" or "um")
○
Speech errors
○
Pitch of voice (pitch changes)
○
Rate of speech
○
Speech pauses
○
-
Nonverbal characteristics
Gaze aversion
○
Smiling
○
Blinking
○
Fidgeting
○
Illustrators
○
Hand or finger movements
○
Leg or foot movements
○
Body movements
○
Shrugs
○
Head movements
○
Shifting positions
○
-
Not all of these are valid indicators of deception.
-
Verb characteristic mostly strongly associated with deception = pitch
Liars speak in a higher-pitched voice.
○
-
Increased use of speech disturbances and a slower rate of speech found during
deception.
-
Verbal Cues to Lying
DePaulo et al (2003):
Most cues did not discriminate between liars and truth-tellers.
○
Liars provided fewer details than truth-tellers.
○
Liars told less compelling accounts.
Less likely to make sense, less engaging, less fluent.
§
○
Liars less cooperative and more nervous/tense.
○
Truth-tellers were more likely to spontaneously correct their stories and
more likely to admit a lack of memory.
○
Deception cues were easier to detect when liars were motivated to lie or
attempting to cover up a personal failing/transgression.
○
-
Adams and Harpster (2008): Can you detect a killer from a 911 call?
Innocent callers were more likely to make requests for help for the victim,
to correct misperceptions, to be rude and demanding of immediate
assistance and to cooperate with the 911 operator.
Considerable emotion in voices and spoke quickly.
§
○
Guilty callers were more likely to provide irrelevant details, blame or
insult the victim, state that the victim was dead, be polite and patient,
with little emotion in their voices.
○
-
Are Some People Better at Detecting Deception?
Ability to detect deception is only slightly better than chance.
-
Aamodt and Custer (2006):
Accuracy rate for detecting deception for "professional lie catchers" was
55.5%.
○
Accuracy rate for students and citizens 54.2%.
○
Basically as good as guessing.
○
-
Bond and DePaulo (2006):
Found no differences in the abilities of experts and non-experts when it
came to lie detection.
○
-
Poor performance explained …
(1) People tend to rely on behaviours that lack predictive validity (e.g., eye
gaze and fidgeting)
○
(2) Most people have a truth bias.
Truth bias: the tendency of people to judge more messages as
truthful than deceptive.
§
○
(3) There are only small differences between liars and truth-tellers.
○
-
O'Sullivan and Ekman (2004):
Identified "wizards" of deception detection.
○
29/12000 professionals were extremely accurate (90% accuracy of
detecting lies about opinions, 80% accurate at detecting lies about a mock
crime and emotions)
○
This method was critiqued and people think that there still are no such
wizards.
○
-
O'Sullivan and Ekman (1991):
Only US Secret Service agents were better than chance at lie detection.
○
1/2 were 80% accurate or greater.
○
The most accurate were those who relied on multiple cues to assess
credibility rather than on any one cue.
○
-
Vrji (2000):
67% accuracy for detecting truths
○
44% accuracy for detecting lies
○
-
POINT: I most studies, truthful messages were identified with more accuracy
than deceptive messages.
Truthfulness bias
○
Not good at detecting lies because they rely on the wrong cues.
○
Police better at detecting high-stakes lies (but still make many errors).
○
-
DePaulo and Pfeifer (1986):
Deception detection of university students, new police offices and
experienced police officers.
○
None of the groups were better than the others.
○
Experienced police officers were more confident in their decisions.
○
-
POINT: Neither level of experience nor confidence in deception-detection ability
is associated with accuracy rates.
-
Bond and DePaulo (2008):
No specific traits related to detecting deception in others.
○
"deception judgments depend more on the liar than the judge"
○
-
Is It Possible to Improve Professionals' Deception-Detection Abilities?
Few studies
-
Looks like you can improve abilities with training.
-
Porter, Woodworth and Birt (2000):
Two-day workshop focusing on myth dissolution, knowledge of
behavioural cues to deception, and performance feedback increased
accuracy to 76.7%
○
-
Porter, Juodis, ten Brinke, Klein, and Wilson (2010):
Three-hour training session increased the detection accuracy of health
care professionals to 60.7%
○
-
Masip, Alonso, Garrido,and Herreror (2008):
Recommended that training programs should focus on teaching deception
cues and truthfulness cues to counteract the tendency for professionals
to judge people as deceptive.
○
-
Chapter 4: Deception (pg. 93-116)
Saturday, February 3, 2018 5:23 PM
Document Summary
Physiological measures have been used in an attempt to detect deception. E. g. , chinese forced suspects to chew dry rice powder and spit it out and if the powder was dry, they would be accused of lying. Premise for polygraph: deception is associated with physiological change. Developed systolic blood pressure test and attempted to use this response as evidence for a person"s innocence. Testimony was rejected by courts in frye v. united states because they felt the test had not gained acceptance by the scientific community. Polygraph: a device for recording an individual"s autonomic nervous system response. Measurement devices are attached to the upper cheat and abdomen to measure breathing. Amount of sweat is measured by attaching electrodes to the fingertips. Hr is measured by a partially inflated blood pressure cuff attached to an arm. Polygraph training is provided by the canadian police college - 12-week intensive course that covres the various techniques, interviewing practice and scoring for police officers.
