Infrared thermal imaging and eye-tracking for deception detection: a laboratory study

Despite significant advances in deception detection in forensic psychology using polygraphy, there is a lack of empirical evidence for the potential of deception detection in ordinary situations of simple conversation where contact and invasive measurement methods are not appropriate. To address this issue, we used two strategies: 1) a non-invasive observation of facial thermal changes and gaze behaviour under deceptive and truthful conditions and 2) combination of prepared and unprepared questions during an interview. We used a within-person experimental design where responses from 16 participants were recorded, using infrared thermal imaging (fITI) and eye-tracking to measure the dependent variables (i.e., thermal changes of the nose, cheeks and forehead and gaze fixations of the interviewer's eyes). The independent variables were veracity (truth vs. lie) and type of scenarios (prepared vs. spontaneous). Mixed-effects regression models were used to analyse the effect of lying and effect of preparation. Veracity did not significantly modulate any physiological marker, but forehead and cheek temperature were significantly modulated by the different scenario conditions in the expected direction. Multiple comparisons revealed a significant modulation of eye fixations by both the lying and scenario conditions, with eye fixations being lower in the spontaneous scenarios and higher in the prepared deceptive conditions. The results underline the significant influence of arousal and cognitive load on individual variability in all dependent variables and provide essential insights for future research into the physiological and behavioural aspects of deception detection. This study lays the foundation for the use of fITI and eye-tracking under certain experimental conditions of an ordinary conversation in content and emphasises the role of (un)preparation for the accuracy of deception detection.