Tracking Lies: The Role of Eye Movements in Forensic Psychology

Aakanksha Pathania, B.Optom

Editorial Assistant, Vision Science Academy

Lying has always intrigued researchers from various fields because it is a complex part of how people interact with each other. ⁽¹⁾ Detecting lies can be challenging for untrained individuals because the indicators of deception are subtle. Deceivers try to conceal their lies by suppressing behavioural cues. ⁽²⁾ In criminal investigations, witnesses who are hesitant to cooperate may choose not to disclose information about a perpetrator, the location of a murder scene, or any knowledge about a weapon. ⁽³⁾

It is currently widely accepted that directly measuring a lie is not possible due to its ambiguous nature. Human reactions and collected behavioural data cannot definitively be classified as deception or truth-telling. However, given the quantitative evaluation of unmeasurable phenomena in various scientific disciplines, there is potential for scientific methods to detect lies and assess credibility accurately. ⁽²⁾

Currently, there are two main theories about lying and its related behaviours. These theories suggest that lying can cause physical or behavioural reactions that may show deception. Another way to detect lies is by using the cognitive load framework. ⁽¹⁾

The polygraph test is commonly used to detect lies. There are two main types: the Concealed Information Test (CIT) and the Comparison Question Test (CQT). However, both types may not be completely exact. ⁽²⁾ Eye-tracking technology can measure cognitive load by analysing fixation durations and saccade amplitudes, offering valuable insights into cognitive processes. ⁽¹⁾ Eye tracking is often seen as a reliable way to detect lies because eye movements are automatic physiological responses that cannot be consciously controlled. It’s a useful tool for detecting deception in surveys because it doesn’t require physical contact, is easy to use, gathers diverse information, and can be used in automated screening systems. ⁽⁴⁾

Figure 1: Tracking Eye Movements
https://insideyourmind.com/nlp-eye-accessing-how-to-make-out-what-people-really-think/.

Eye movements can serve as indicators of cognitive load, emotions, attention, and information processing. High cognitive load is associated with pupil dilation, decreased blink rate, increased saccade velocity, and longer fixation duration. Arousal changes can affect blinks, saccades, and fixations, while vigilance and fatigue can be detected through saccades. Additionally, eye movements can be used to predict information processing. ⁽⁴⁾ When people lie, their pupils dilate due to increased cognitive effort, memory retrieval, vigilance, and anxiety. Research also suggests that lying leads to quicker eye movements, increased blinking frequency, and longer blink durations. ⁽⁴⁾ In Forensic Psychology, deception detection uses various assessment tools. One such tool is the Eye Detect System (EDS), which focuses on involuntary eye movements to detect deception. It employs an infrared system and a complex algorithm. Test results categorise individuals as credible or not credible based on their honesty during the test. ⁽⁵⁾

In EDS, three types of tests are used: Relevant Comparison Test (RCT), Multi-issue Comparison Test (MCT), and Direct Lie Comparison Test (CLDT). The questions given to the examinee can be divided into three categories: comparison questions, relevant questions, and neutral or irrelevant questions.

EDS is a modern tool for detecting deception. It requires a certain level of education for the test. The researcher has chosen to study white-collar crime, specifically cybercrime, which usually involves educated people. The tool considers that most people today have basic computer knowledge and education. ⁽⁵⁾ Eye tracking has enormous potential for detecting recognition in real-life situations. It can reveal intentional efforts to conceal knowledge about familiar faces, scenes, and objects. ^(3,4)

References:

1. Lim, K. K., Friedrich, M., Radun, J., & Jokinen, K. (2013, December). Lying through the eyes: detecting lies through eye movements. In Proceedings of the 6th workshop on Eye gaze in intelligent human machine interaction: gaze in multimodal interaction(pp. 51-56).
2. Celniak, W., Słapczyńska, D., Pająk, A., Przybyło, J., & Augustyniak, P. (2023). Intelligent Eye-Tracker-Based Methods for Detection of Deception: A Survey. Electronics, 12(22), 4627.
3. Millen, A. E., Hope, L., & Hillstrom, A. P. (2020). Eye spy a liar: assessing the utility of eye fixations and confidence judgments for detecting concealed recognition of faces, scenes and objects. Cognitive research: principles and implications, 5, 1-18.
4. Fang, X., Sun, Y., Zheng, X., Wang, X., Deng, X., & Wang, M. (2021). Assessing deception in questionnaire surveys with eye-tracking. Frontiers in psychology, 12, 774961.
5. Ghosh, M. M., Mahajan, P. B., & Ramesh, P. P. (2023). Detection of Deception through Eye Detect System (EDS). International Journal of Indian Psychology, 11.