Vrij, Mann and Bull

The aim of the study was to study truth telling behaviour or deceptive behaviour in high stake liars.
It is generally believed that liars fidget more and avoid eye contact when in reality most people move less and become quite still. There is also no relationship between eye contact and lying.
There have been issues with previous studies (most of which were laboratory experiments). Most of the studies lacked ecological validity as subjects were aware of the purpose of the study and were aware of being observed and or videotaped. Since in most cases subjects had been asked to lie they also felt less less guilty. One of main problems with the past studies was that there were minimal consequences as trivial questions such as personal opinions etc were investigated
1. It was due to these points that a study was devised to examine the behaviour of liars in high-stake situations.
  1. Vrij and Mann in the study examined videotapes containing the truthful and deceptive behaviour of 16 suspects in their police interviews. The stakes were high and for 4 of the 16, getting caught meant a life sentence in prison.
    1. 16 subjects (13 male, 3 female). 4 were juveniles (three 13 year olds and a 15 year old). 15 Caucasian and 1 Punjabi. 9 Arrested for theft, 4 for murder, 2 for Arson and 1 for attempted rape
Two coders used in the study. One viewed all 65 clips (27 truths, 38 lies), other viewed only 36. Hence some form of inter-rater reliabilty
1. Minimum 2 clips (1 lie, 1 truth) and maximum 8 clips (3 truths, 5 lies) per participant
  1. Length of clips between 5 and 145 seconds.
2. They looked for eight categories: Gaze aversion, head movements, blinking, pauses, speech disturbances, illustrators, self manipulation and hand movements
  1. Results:
    1. 81% of the participants pause longer when lying. (5.31 vs 3.73)
    2. Blinking decreased by 81% when participants were lying. (18.50 vs 23.56)
    3. Behaviour however was not same for all participants and there was no typical lying behaviour. For example, 56% showed more gaze aversion and 44% less. Similarly 50% showed more head movements and 50% less.
    4. Problems with the study include:
      1. Different interviewers used for different videos. They did not compare high-stake lying behaviour with high-stake truth telling behaviour. The Sample size is also limited. Facial expressions such as microexpressions as brought up by Ekman could not be studied due to insufficient quality of videotapes.
People may not always show nervous behaviour due to increased cognitive load.
1. Increase in cognitive load results in: Neglect of body language, reduced overall animation, increased speech disturbances and longer pauses, increased cognitive load also results in eyeblink suppression
2. Liars often attempt to control their behaviour in order to give a credible impression. This is called motivational impairment effect.

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Vrij, Mann and Bull

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	Created by Mohammed Sajid 2121 almost 9 years ago