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

2002

Samantha Mann, Aldert Vrij, and Ray Bull

How can you tell if someone is lying?

http://www.youtube.com/watch?v=E3PAW7zjgPw&feature=fvst

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

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

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

http://www.youtube.com/watch?v=NkH25r9P1dc

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 recordedgaze aversionblinkinghead movementsspeech disturbancespauseshand & 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 loadsingle blind studyquasi-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.