Abstract
Visual-vestibular conflict during virtual reality (VR) use is thought to cause VR sickness, but the relation between conflict-sensitivity and sickness is poorly understood. We investigated this relationship by manipulating fixation behavior (head/scene-fixed) and retinal stimulus location (RSL, central/peripheral/full) in a 2x3 design during a conflict detection task. We measured sickness via completion of Simulator Sickness Questionnaires before and after each condition and discomfort scores every 3 minutes. During each trial, subjects made yaw head movements of 15-50° over ~1.5 seconds, and fixated on either an environmentally-fixed (scene-fixed) target, or a target fixed relative to their field of view (FOV, head-fixed). We manipulated RSL by reducing FOV to ~40° using a peripheral mask (central), a ~40° scotoma (peripheral), or not at all (full). The visual scene was an optokinetic drum displayed using the HTC Vive Pro Eye. Visual scene motion was manipulated to be slower or faster than the subject’s head movement, and subjects reported the direction of conflict on each trial (as with or against, respectively). We fit a psychometric function to the data to find the visual gain (visual/head speed) perceived as stationary (PSE, accuracy) and range of gains compatible with perception of a stationary visual environment (JND, precision). Results show correlations between JND, PSE, and sickness scores. Better precision is associated with better accuracy during conflict detection, and better accuracy and precision are both associated with lower reports of VR sickness. Additionally, sensitivity to conflict (lower JND) was greatest and sickness was lowest during scene-fixed and central conditions, consistent both with the known benefits of natural fixation behavior and FOV restriction. These results are the first to our knowledge to demonstrate an association between conflict sensitivity and VR sickness.