Nausea reshapes visual exploration and pupillary responses to affective images
Perception is a continuous, active, and dynamic process of inference shaped by current goals, past experience, and hard biological constraints. The physiological state of the body is arguably the most fundamental one. Continuous inference about interoceptive states colors perception with emotions, which in turn affect basic perceptual and attentional processes. How, then, do we really look at the world when experiencing malaise? Here we leverage Galvanic Vestibular Stimulation (GVS) - a non-invasive brain stimulation technique that induces mild dizziness, motion sickness, and nausea - in conjunction with high-resolution eye tracking, pupillometry, and computational modelling. We demonstrate that mild vestibular perturbations disrupt the coupling between gaze and informative low-level visual features. Crucially, however, this effect depends on individual susceptibility and on stimulus valence. Particularly susceptible participants experiencing stronger nausea increase their reliance on visually salient features, and particularly so for threatening (negatively valenced) images. Pupillometry reveals larger tonic pupil size in these participants, consistent with heightened arousal, as well as disrupted phasic responses to affective pictures. Altogether, these results unveil the continuous and dynamic interplay between interoceptive and exteroceptive processes, showing that how we perceive the environment fundamentally resonates with how we feel.