Effectiveness of pupil diameter in a probable-lie comparison question test for deception
Article first published online: 24 DEC 2010
2009 The British Psychological Society
Legal and Criminological Psychology
Volume 14, Issue 2, pages 279–292, September 2009
How to Cite
Webb, A. K., Honts, C. R., Kircher, J. C., Bernhardt, P. and Cook, A. E. (2009), Effectiveness of pupil diameter in a probable-lie comparison question test for deception. Legal and Criminological Psychology, 14: 279–292. doi: 10.1348/135532508X398602
- Issue published online: 24 DEC 2010
- Article first published online: 24 DEC 2010
- Received 16 March 2008; revised version received 7 November 2008
Purpose. There were three objectives of this study: (1) To assess the possibility of using pupil diameter as an index of deception in the context of a comparison question polygraph test. (2) To determine if pupil diameter would make a significant contribution to an optimal multivariate classification equation in combination with the traditional predictor variables used in field polygraph practice. (3) We explored the possibility of replacing one or more of the traditional predictor variables with pupil diameter.
Methods. We used a laboratory mock crime experiment with 24 participants, half of whom stole $20 (US) from a secretary's purse. Participants were tested with a comparison question test modelled after standard field practice. Physiological measures were taken with laboratory quality instrumentation. Features were extracted from the physiological measures. Those features were subjected to a number of different statistical analyses.
Results. Innocent participants showed larger increases in pupil diameter in response to probable-lie questions than to relevant questions. Guilty participants did not show differential responding to the question types. The additional of pupil diameter to a multivariate classification model approached, but did not reach significance. Subsequent analyses suggest that pupil diameter might be used to replace the traditional relative blood pressure measure.
Conclusions. Pupil diameter was found to be a significant predictor variable for deception. Pupil diameter may be a possible replacement for the traditional relative blood pressure measure. Additional research to explore that possibility would seem to be warranted.