Mann, Vrij and Bull's Study of High Stakes Liars

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Background Information:
  • Vrij and Mann wanted to know of a difference between lying in a "real life setting" and in an "experimental situation".
  • Cognitive load (Said to play a role in actions caused by lying): *Cognitive load: When the mind is working on complex things where information and interaction are being pressed simultaneously the brain can either under or overload. This would cause different behaviors.

Aims:**
  • Are there certain behaviors that differentiate a liar from a truth teller?
  • Determine if cognitive load increases lie behaviors.

Participants:
  • Police video tapes from 16 suspect. 13 males, 3 females. 4 children (13,13,13 &15) and 12 adults (younger than 65).
  • 15 Caucasian, 1 Asian. Most participants had previously been known previously to the police.
  • Most crimes committed were theft, arson, attempted rape and murder.

Research Method:
  • This was a quasi experiment. Quasi experiment: independent variable was not directly manipulated by the experimenter.


How Was the Data Collected?:
  • Data was collected by two independent observers, coding footage from previously recorded police tapes. They were unaware of any hypothesis of the study.
  • ~*Pearson Correlation Statistical Test: Measuring the strengths of differences between two variables.



Type of Data Collected:
  • Data collected was quantitative, meaning percents and numbers.


Procedure:
Two observers were asked to "Code data", weren't told much about the experiment previously. For every behavior of the participants it was coded with 1 truth telling score and one lie telling score.
~Some of the behaviors recorded:
  1. Gaze Aversion
  2. Blinking
  3. Head movements
  4. Speech disturbances (stuttering)
  5. Pausing between words, and or sentences.
  6. Hand and arm movements
  7. Self manipulations
  8. hand/finger movements



Special Equipment and Materials:
  • Police video recording.
  • Independent observers



Results:
  • Behaviors were not significantly different.
  • Noticeable differences were found between the hand, arm movements and pauses.
  • Gave some support to the cognitive load process. Behaviors leading to cognitive load would be blinking and pausing.



Conclusions - Based off of Results:
  • Because they did not measure

Strengths:
  • High levels of control
  • Participants had no idea they were participating in a study (mainly because they were old tapes)

Weaknesses:
  • Conclusions are speculative.
  • Small participant group.
  • Possible (slight) gender/ age bias.

Ecological Validity:

  • High level of ecological validity.


Ethics:


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