suspects , lies and videotape: an analysis of authentic high-stake liars

SUSPECTS, LIES AND VIDEOTAPE: AN

ANALYSIS OF AUTHENTIC HIGH-STAKE LIARS

Mann, Vrij & Bull

When people are lying… What behaviours do you expect

them to have?

Background and context Most people think that, when lying,

people: Avoid eye contact Increase fidgeting nervous movements Nervous movements

Previous research most people decrease in non functional movements and become unnaturally still.

There is no relationship between eye contact and deception

Background and context Until now lab experiments

have required participants to tell a lie or the truth about beliefs and opinions.

But some of these settings differ from real life settings not generalizable

Background and contextWhy do these kind of

experiments are not representative?

1. Participant is asked to lie- Some experimenters have allowed participants to choose if lying or telling the truth but the lie is told “for the sake of the experiment”.

Background and context2. Participants will usually be

videotaped and they know their lying/truth behaviour will be later analysed by someone

3. Telling lies of negligible consequence unethical to offer punishment for lying.

*So there is still a possibility that high-stake liars are more nervous and perform nervous behaviours.

Background and context So, to address all

these points, another study was designed to analyse behaviours of spontaneous liars.

Where? Police department high-stake situations with suspects.

Background and context Very difficult to catch non-verbal

behaviour in people who lie. Vrij & Mann (2001) analysed video

tapes of murderers– lots of insight into the topic.

Liars may not display nervous behaviours because they are probably experiencing other processes simultaneously increased cognitive load or attempted behavioural control.

These, could negate nervous behaviours

Background and contextOther points to be considered:

1. Liars in this study will probably have to think hard to make their lies convincing or otherwise sentence

Background and context*People involved in complex cognitive tasks

make fewer movements:- Fewer illustrators: arm and hand movements are designed to supplement speech- Self-manipulations (scratching, etc)- Other subtle hand movements.

*Increase in cognitive load results in:- A neglect of body language, reducing overall movements.- Increased speech disturbances- Longer pauses before an answer- Eye-blink suppression

Background and context2. Liars often try to control their

behaviour in order to give a credible impression to the interviewer.

“Motivational impairment”: (DePaulo&Kirkendol): the higher the motivation to succeed in the lie, the greater the likelihood that liars will try to control their behaviour.

There is a strong belief that liars usually move away their gaze and make nervous movements, so liars will try to mantain eye contact and avoid movements. cultural stereotype of liars.

Background and contextHow does this happen?

Cultural belief

Excesive control

Not aware of body

language

Overzealous control

Deliberate movements and

rigidity

Background and context Summary: no single

pattern of behaviour is related to deception.

Pinocchio’s growing nose doesn’t exist

We also need to consider individual differences.

METHOD: Participants 16 police suspects (13 males, 3 females= 4 juveniles: 3 aged 13, 1 aged 15 15 caucasian (english), 1 asian All interviews were done in english Crimes:

Theft (9)Arson (2)Attempted rape (1)Murder (4)

PROCEDURE Police detectives Kent

County, UK Recollection of videotaped

interviews where suspect had lied at some point and told the truth at another (serious cases)

Experimented investigated files to confirm if subjects were lying or telling the truth

PROCEDURE Suspects deny evidence is

shown to them they confess.

Results: 16 clips of subjects

Truths and lies had to be of the same nature (about events, not personal details for ex)

PROCEDURE Number of clips per

participant varied For each participant,

min 2 clips: 1 truth, 1 lie

Vrij & Winkel: differences between lying and truth-telling behaviour are independent of length of the clip

Dependent variables 2 observers independently coded

8 behaviours

Recorders where (single) blind to truth/lie variable and aim/hypothesis

Interrater reliability inter observer

Ideally 2 observers coded everything, but ethically, the least possible people to code.

Dependent variables Behaviours observed:

Gaze aversion (seconds participant looked away)

Blinking (frequency)Head movements (frequency of head nods)Self-manipulations (frequency)Illustrators (freq of arm/hand movement)Hand/finger movements (frequency)Speech disturbancesPauses (seconds)

*Strong consistency between 2 coders

Dependent variable The total length per

minute of footage for each behaviour was calculated.

Result: 1 truth-telling score, 1 lie-telling score for each behaviour, for each participant.

RESULTS Lying was accompanied by a

decrease in blinking and an increase in pauses.

As expected, individual differences did occur and there was no behaviour that all liars exhibited

50% showed increased head movements and 50% a decrease.

56% showed more gaze aversion and 44% showed less gaze aversion

RESULTS 69% showed a decrease in

hand and arm movement during deception

33% showed an increase.

Most reliable indicator of deception: blinking and pauses:81% paused longer81% blinked less

DISCUSSION This study has the most extensive which

has examined deceptive behaviour in real-life, in high-stakes setting.

2 significant differences occured:Suspects blinked less and paused longer

while lying.

DISCUSSION Some support for the

cognitive load process less blinking and longer pauses possible indicators of cognitive load

Blinking strongest indication that cognitive load affects more suspects’ behaviour than nervousness

DISCUSSION Nixon effect: increase in

blinking (he blinked more than 50 times/min during resignation)

However, increased cognitive load results in a decrease in blinking, but conclusions are speculative (no methodology)

DISCUSSION Large individual

differences were shown probably no typical lying behaviour exists.

Probably the most reliable indicator of deception change in the individual’s normal behaviour

DISCUSSION: Limitations 1. Different interviewers were

used for different participants 2. Sometomes more than one

interviewer was present 3. The total number of people

present, varied depending on the number of interviewers, attorney, etc.

In this study, experimenters managed to control this factors.

DISCUSSION Researchers can’t be

sure that the clips that they compared were comparable

They didn’t compare high-stake liars to people who are trying to plead their innocence when falsely accused.

The experimenters couldn’t obtain such footage.

DISCUSSION Both liars and truth

tellers might experience similar behaviour

16 participants is not a large sample

Difference between this sample and the whole population limitation for generalizability.