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

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.

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

  • 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.

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

  • 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

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

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

Ecological Validity:

  • High level of ecological validity.