Effectiveness of Pupil Diameter in a Probable-Lie Comparison Question Test for Deception

• NCJ Number: 229348
• Journal: Legal and Criminological Psychology Volume: 14 Issue: 2 Dated: September 2009 Pages: 279-292
• Author(s): Andrea K. Webb; Charles R. Honts; John C. Kircher; Paul Bernhardt; Anne E. Cook
• Date Published: September 2009
• Length: 14 pages
• Sponsoring Agency: US Dept of Defense Polygraph Institute
• Publication Format: Article
• Publication Type: Report (Study/Research)
• Language: English
• Country: United Kingdom

Annotation

This study's three objectives were to assess the feasibility of using eye pupil diameter as an index of deception in a comparison-question polygraph test, to determine whether pupil diameter could contribute significantly to an optimal multivariate classification equation in combination with the usual predictor variables for field polygraphs, and to examine the feasibility of replacing one or more of the traditional predictor variables with pupil diameter.

Abstract

The study found that pupil diameter was as highly correlated with deception as skin conductance, which is invariably the best traditional indicator of deception in laboratory and field research on polygraph techniques (Kircher and Raskin, 2002). In addition, adding pupil diameter to a regression equation that contained skin conductance, cardiograph, and respiration measures appreciably, but not significantly, increased the proportion of variance explained. Further, the study findings suggest that it might be possible to replace the relative blood pressure with pupil diameter without sacrificing polygraph accuracy. A replacement for the relative blood pressure would be useful, because the cuff becomes uncomfortable for some subjects if it is inflated for more than a few minutes. Moreover, the use of an inflated cuff limits the number of questions that may be asked before it is deflated. Before this change is recommended, however, the results should be replicated in other laboratories and in field settings. Half of the 24 participants in this laboratory mock crime experiment had "stolen" $20 from a secretary's purse. All participants were tested with a comparison-question test modeled after standard field practice. Physiological measures were taken with laboratory quality instrumentation. Features were extracted from the physiological measures; and the features were subjected to a number of different types of statistical analyses. 3 tables, 2 figures, and 35 references