Pupil Dilation May Signal Deception

The eyes are the windows to deception.

Posted Jan 30, 2019

Peter Lamb/123RF
Source: Peter Lamb/123RF

Pupil dilation may signal deception. The autonomic nervous system regulates pupil size. Pupil dilation normally indicates an increase in cognitive demand. Liars usually experience an increase in cognitive demand. The interviewer must form a baseline to detect deception when the person being interviewed has no reason to lie. Any disparity from the baseline may signal deception. Therefore, pupil dilation may signal deception.

Creating a Baseline

The interviewer must form a baseline to detect deception (Ewens, Vrij, Jang, & Jo, 2014). When the interviewee possesses no reason to lie, the interviewer must ask questions to determine a baseline (Ewens et al., 2014). The interviewer must observe verbal and non-verbal patterns throughout the baseline questions (Ewens et al., 2014). Any disparities from the baseline may signal deception (Ewens et al., 2014).

Autonomic Nervous System

The sphincter and dilator muscles regulate pupil size (Kupcová, 2017). The autonomic nervous system (ANS) controls the sphincter and dilator (Kupcová, 2017). Sympathetic activities, a part of the ANS, increase in stressful situations (Kupcová, 2017). The increase in sympathetic activities causes pupil dilation (Kupcová, 2017). ANS activities, including pupil dilation, transpire automatically (Kupcová, 2017). Therefore, pupil dilation may signal deception.

Cognitive Demand

Pupil dilation normally indicates an increase in cognitive demand (Szulewski, Fernando, Baylis, & Howes, 2014). Lying causes an increase in cognitive demand (Vrij, Granhag, & Porter, 2010). Liars attempt to formulate a truthful and logical story (Vrij et al., 2010). Liars check their behaviors and manners to appear truthful to the interviewer (Vrij et al., 2010). To determine if the lies worked, liars observe the responses of the interviewer (Vrij et al., 2010). Liars suppress the truth throughout the story, which requires more cognitive demand (Vrij et al., 2010). Therefore, pupil dilation may signal deception.

Motivation to Lie

In a research environment, the researcher directs the subjects to lie (Matsumoto, Sung Hwang, Skinner, & Frank, 2011). Subjects often lack a strong motivation to lie because no consequences are associated with lying (Matsumoto et al., 2011). Subjects face no punishments if they are caught lying (Matsumoto et al., 2011). In reality, liars are motivated to lie (Matsumoto et al., 2011). In reality, liars face harsh punishments if caught (Matsumoto et al., 2011). In reality, liars expose their lies through verbal and non-verbal cues, including pupil dilation (Matsumoto et al., 2011). Therefore, pupil dilation may signal deception.

Conclusion

Pupil dilation may signal deception. The autonomic nervous system regulates pupil size. Pupil dilation normally indicates an increase in cognitive demand. Liars usually experience an increase in cognitive demand. The interviewer must form a baseline to determine deception. Any disparity from the baseline may signal deception. Therefore, pupil dilation may signal deception.

By Gunner Fletcher. Gunner was a student in my Fall 2018 Police Report Writing class at Western Illinois University. The post was edited for content and formatting.

References

Ewens, S., Vrij, A., Jang, M., & Jo, E. (2014). Drop the small talk when establishing baseline behaviour in interviews. Journal of Investigative Psychology and Offender Profiling, 11(3), 244–252. Retrieved from https://doi.org/10.1002/jip.1414.

Kupcová, M. (2017). Ocular-Motor Methods for Detecting Deception: Effect of Countermeasures. Retrieved from https:// is.muni. cz/th/fqvxb/DP_Ocular-Motor_Methods_for_Detecting_Deception_Kupcova.pdf.

Matsumoto, D., Sung Hwang, H., Skinner, L., & Frank, M.G. (2011). Evaluating Truthfulness and Detecting Deception. FBI Law Enforcement Bulletin. Retrieved from http://davidmatsumoto.com/content/Evaluating% 20Truthfulness%20and%20Detecting% 20Deception.pdf.

Szulewski, A., Fernando, S.M., Baylis, J., & Howes, D. (2014) Increasing Pupil Size Is Associated with Increasing Cognitive Processing Demands: A Pilot Study Using a Mobile Eye-Tracking Device. Open Journal of Emergency Medicine, 2, 8-11. Retrieved from http://dx .doi.org/10.4236/ojem.2014.21002.

Vrij, A., Granhag, P.A., & Porter, S. (2010). Pitfalls and Opportunities in Nonverbal and Verbal Lie Detection. Psychological Science in the Public Interest, 11(3), 89-121. Retrieved from http://www.jstor.org/stable/41038740.