Lie Detector Tests: Physiology and Ethics

Have you ever watched Love Island? It’s truly a horrible reality TV show based from the UK but it makes for a quality binge-watch. I recently watched an episode where the people on this show undergo a lie detector test in their relationships and wondered, what exactly is the mechanism to detect deception? This led me on my journey to find some interesting literature about established neural connections linked to deception, meaning that there might be some credibility to these lie detector tests.

The most common lie detection test we can think of is the polygraph which is actually utilized in security screenings and interrogation by the US Department of Defense (Cook & Mitschow, 2019). It detects deception-induced stress in the autonomic nervous system (ANS) like heart rate, blood pressure, respirations, and even perspiration (Cook & Mitschow, 2019). However, it is up to the individual jurisdictions to allow polygraph evidence into the court and Colorado is one of the few states that actually allows it.

However, there are other physiological tests for lie detection. Ofen et al. conducted a study using fMRI to scan brain activity while participants lied or told the truth about their own personal experiences or beliefs. They found that both the frontal and parietal cortex showed higher activation when participants lied, demonstrating that there is some detectable connection when they are conjuring up a lie (Ofen et al., 2017). The frontal and parietal cortexes, as we know, are involved in cognitive thinking and decision making, which makes sense when we have to think up something other than the truth on the fly. However, they also found that different areas of the brain were activated based on the content of the lie, either personal experience or an opinion (Ofen et al., 2017). This shows that although there are correlations to the brain during deception, those connections could be blurred by the kind of lie the person is telling which introduces a myriad of conflicting factors if we want to actually implement this.

Let’s discuss the implications of this. Asking about personal experiences and beliefs is useful in court cases for witness testimonies but does that mean we need a fMRI machine in every courtroom? Let’s also consider that these findings do not really prove anything. These findings are variable and based on the context of the lie and these regions of the brain may just be activated because of the individual’s own logical thinking independent of the lie (Ofen et al., 2017). This does provide more insight in mapping the human brain, but even that has not been achieved in its entirety. There's still so much we don't know about our brain so are lie detection tests a means of closing that knowledge gap? Are they even relevant today?

Cook, L. G., & Mitschow, L. C. (2019). Beyond the Polygraph: Deception Detection and the Autonomic Nervous System. Federal practitioner : for the health care professionals of the VA, DoD, and PHS, 36(7), 316–321.

Ofen, N., Whitfield-Gabrieli, S., Chai, X. J., Schwarzlose, R. F., & Gabrieli, J. D. (2017). Neural correlates of deception: lying about past events and personal beliefs. Social cognitive and affective neuroscience, 12(1), 116–127. doi:10.1093/scan/nsw151