Investigating the impact of sopite syndrome on physiological responses during an immersive Augmented Reality (AR) game in a moving vehicle.

Motion sickness remains a major barrier to passenger comfort and, in particular, to the acceptance of autonomous vehicles. Indeed, prolonged exposure to low-frequency vehicle motion places passengers at a higher risk of developing sopite syndrome. Sopite syndrome refers to a lesser-known form of motion sickness characterized by a state of hypo-arousal akin to fatigue and drowsiness, which can, in turn, impair alertness and cognitive performance. Therefore, these adverse effects highlight the need to develop sopite countermeasures for car passengers. This on-road study examined whether an immersive augmented reality (AR) game with visual content synchronized to vehicle motion could mitigate sopite syndrome compared to a non-synchronized version, by enhancing sensorimotor congruence. Twenty-five participants experienced two AR conditions, both presented on a headrest-mounted screen: a synchronized AR game where virtual motion matched vehicle dynamics, and a desynchronized AR game where this motion was intentionally delayed. Sopite syndrome was assessed using the Motion Sickness Assessment Questionnaire (MSAQ), and the physiological profile was determined based on Heart Rate Variability (HRV), respiration, skin temperature and blink frequency. The main results indicate that (1) sopite syndrome has a parasympathetic-dominant physiological profile and (2) an AR game synchronized with the vehicle's motion mitigates the sopite syndrome by reducing sensory conflict, compared to a desynchronized version. As a result, engaging passengers in an AR game where the visual content is synchronized to the vehicle's motion seems to be a promising strategy to alleviate sopite syndrome, thereby enhancing their comfort and maintaining arousal during Non-Driving Related Activities (NDRAs).