Suspects, Lies, and Videotape : An Analysis of Authentic High-Stake Liars 2002

Samantha Mann, Aldert Vrij, and Ray Bull

Objectives

To identify certain body movements, those are present when a person is lying.

Differentiate between a novel liar and authentic liars.

How did they conduct the study and what did they find out.

Keywords High Stakes Authentic Forensic Content Analysis Cognitive Load Single Blind Study Quasi-experiment Pearson Correlation Statistical Test (R Value)

Introduction

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Are you a liar? You would probably answer "no". Let's ask it another way. How many times did you say something that was not completely true last week? For many reasons, the answer is probably quite a lot! We're all liars some of the time, but for some people lying may be extremely important. How do people act when lying is the only think they can do to keep themselves out of jail? Do they blink a lot? Sweat? Let's find out.

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? 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

AIM1. To determine if there are systematic behavioral

indicators to distinguish between those who are telling lies and those who are telling the truth.

2. 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

SamplePolice 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 truthOnce cases meeting this criterion were found the case files were gathered up.

SampleAn 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 – Natural experiment/quasi experiment • The independent variable was not directly manipulated by the experimenter1) What was the independent variable? Whether they decided to tell the truth or lies.

2) What was the dependent variable? The accompanying body language.

Design: Repeated measures designThe participants had a video recording of their body language both when they lied and later told the truth.

Procedure1. Total of 65 video clips (27 truth / 38 lies)2. Length of clip & length of response varied but

not significant in terms of analysis of behavior.

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? deception What is it used to control? Demand

characteristics.

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 recorded1. Gaze Aversion2. Blinking3. Head Movements4. Speech Disturbances5. Pauses6. Hand & Arm Movements (These Were Originally

Coded Individually) 7. Self-manipulations 8. Illustrators 9. Hand-finger Movements

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

Controls1. Two observers told to independently code

behavior were compared for on a sample of the videos (not all of them) 2. What is this called? Observer triangulation to check inter rater reliabilty 3. What is it used to control? Participant bias4.A Pearson correlation statistical test • A measure of the strength of a linear association between two variables 5. Strong consistency between the two coders, in other words there was no significant difference between the two coders.

Results1. Behavioral results for the 6 categories were not

significantly different2. Noticeable differences were found between the

hand and arm movements (truthful 15.31; lying 10.80) and pauses (truthful 3.73, lying 5.31)

3. The deceptive group paused longer and blinked less but there were many individual differences

4. http://www.youtube.com/watch?feature=player_embedded&v=P_6vDLq64gE

ExplanationsGive some support for the cognitive load process in explaining deceptive behavior, as both fewer blinking and longer pauses are possible indicators of cognitive loadHowever, because they did not measure nor manipulate cognitive load and nervousness in this study, all conclusions are speculative

Summary The body language of authentic liars is different from

people who lie in normal situations.The best indicators are pauses and blinking.

Alternative study Mann et al conducted a quasi experiment. An alternative study

method might have been to conduct a true lab experiment.

1. Describe a laboratory experiment as an experimental method. (5)

2. How could they have conducted an experiment with a similar aim, but as a true lab experiment?

Write a description of the study, including the who, what, where and how.(10)

2. What would the advantages and disadvantages of such an experiment be, compared to the original?

 Evaluate this new study in practical and methodological terms. (10)

Guide http://psychtutor.weebly.com/mann-vrij-and-bull---

high-stakes-liars.html

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