Effects of deceptive behavior on biomechanical measures of standing posture

Abstract

The accurate detection of deception has potential applications in many fields including credibility assessment, security screening, homeland security, and counter-terrorism. Techniques currently used for deception detection typically capitalize on deception-related physiological changes, and include polygraph testing, voice stress analysis, brain activity analysis, and thermal scanners. However, the use of these techniques in natural environments is limited as they often require intrusive sensors to be attached to the body. These limitations may be addressed with posturography, which involves studying the ground reactions associated with standing balance without the need for intrusive sensors. Therefore, the objective of the current study was to examine deception-related effects on measures of standing posture using a mock security screening interview. We hypothesized that deceptive participants, compared to truthful would demonstrate significant differences in ground reactions during the interview. Participants were required to pack a backpack with various items. One group of participants had items that were "prohibited", whereas the other group had equivalent, non-prohibited control items. Both groups were questioned about the contents of the backpack. The group with "prohibited" items was instructed not to reveal that they were carrying any prohibited items. Results of the study indicated that there was a significant deception-related decrease in center of pressure movement. The deception related decrease in both center of pressure pathlength and mean velocity suggests that people "freeze" when they are being deceptive. This notion was supported by increased oscillations in the anterior-posterior direction.