Suspects, Lies, and Videotape:
An Analysis of Authentic High-Stake Liars
Samantha Mann, Aldert Vrij, and Ray Bull
How to Spot a Liar
Fidgeting?
Decreased eye contact?
Actually most people move less
and to date there has been no
credible study done to show any
connection between eye contact
and truthfulness
Background
The behavior of liars has traditionally
been studied experimentally, in the
laboratory
• Can you see a problem with this?
Background
Vrij and Mann (2001) Differences
between lying in ‘real life settings’ &
lying in an ‘experimental situation’ led
to examining videotape of a murder in
police custody
This study extends the findings of that
study with a larger sample
AIM
To determine if there are
systematic behavioral indicators
to distinguish between those who
are telling lies and those who are
telling the truth.
To determine if cognitive load
causes changes in behavior
related to lying or telling the truth
Cognitive Load
Hypothetical construct used to
describe the load related to the
executive control of working memory.
• Cognitive psychologists argue that during
complex mental activities the amount of
information & interactions that must be
processed simultaneously can either
under-load, or overload the finite amount
of working memory one possesses
Sample
 An opportunity sample of 16 police’ suspects
• 13 males & 3 females
• 4 juveniles (three-13 y.o. & one-15y.o.) & 12 adults (under
65).
• 15 were Caucasian (English as a 1st language) & 1 Asian
(Punjabi was his 1st but was fluent English)
 All interviews were conducted in English.
 Crimes for which participants were being interviewed
•
•
•
•
Theft (9)
Arson (2)
Attempted rape
murder (4)
 Most participants (10), were known to the police &
had been interviewed about other crimes
Sample
Police detectives at Kent County
Constabulary (U.K) were asked if they
could recall videotaped interviews in
which they had participated, where the
suspect had initially lied and later told
the truth
Once cases meeting this criterion were
found the case files
were gathered up
Sample
An hour-long videotape consisting of clips
from 16 suspects.
The truths that were selected were chosen
so they could be as comparable as possible
in nature to the lies
• Truthful response to an easy question such as
giving a name and address is not comparable to
a deceitful response regarding whether or not the
suspect has committed a murder.
Method
A quasi experiment
• The independent variable was not directly
manipulated by the experimenter
What was the independent variable?
• What was believed to effect the measured
variable?
 What was the dependent variable?
• What was being measured?
Procedure
Total of 65 video clips
(27 truth / 38 lies)
Length of clip & length of
response varied but not
significant in terms of analysis
of behavior
Procedure
Observers were instructed to
‘code the video footage’ – Content
analysis
• Not informed about the hypothesis or
nature of the video clips
• What do we call this? What is it
used to control?
Content Analysis
A methodology used in the social sciences
for objectively studying the content of a
communication (written work, speech, film)
It is a quantitative method producing data
that is often percentages or numerical,
serving two important purposes:
• to remove much of the subjectivity from
summaries
• to simplify the detection of trends
Behaviors recorded
gaze aversion
blinking
head movements
speech disturbances
pauses
hand & arm movements (these were
originally coded individually)
• self-manipulations
• illustrators
• hand-finger movements
Procedure
Each of the coded behaviors was
transformed into a format, so that the
truths and lies could be directly
compared
The result was one truth-telling score,
and one lie telling score for each
behavior for each participant
More Control
Two observers told to independently code
behavior
• Were compared for on a sample of the videos
(not all of them)
• What is this called? What is it used to
control?
 A Pearson correlation statistical test
• A measure of the strength of a linear association between
two variables
• Strong consistency between the two coders, in other words
there was no significant difference between the two coders.
Results
Behavioral results for the 6 categories
were not significantly different
Noticeable differences were found
between the hand and arm movements
(truthful 15.31; lying 10.80) and pauses
(truthful 3.73, lying 5.31)
The deceptive group paused longer and
blinked less but there were many
individual differences
Explanations
Give some support for the cognitive
load process in explaining
deceptive behavior, as both fewer
blinking and longer pauses are
possible indicators of cognitive load
However, because they did not
measure nor manipulate cognitive
load and nervousness in this study,
all conclusions are speculative
VOCABULARY
content analysis
cognitive load
single blind study
quasi-experiment
Pearson correlation statistical test (r value)
Resources
BANYARD, P. AND GRAYSON, A. (2000)
Introducing Psychological Research;
Seventy Studies that Shape Psychology, 2nd
Edition. London: Macmillan
GROSS, R. (1999) Key Studies in
Psychology, 3rd Edition. London: Hodder
and Stoughton
HILL, G. (2001). As level psychology through
diagrams. Oxford: Oxford University Press.