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 context Why 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 context 2. 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 context Other 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 context 2. 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 context How does this happen? Cultural belief Excesive control Not aware of body language Overzealou s 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 disturbances Pauses (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 longer 81% 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.