Limits of subjective and objective vection for ultra-high frame rate visual displays

Abstract

Large-field optic flow generates the illusory percept of self-motion, termed vection. Smoother visual motion displays generate a more compelling subjective sense of vection and objective postural responses, as well as a greater sense of immersiveness for the user observing the visual display. Research suggests that the function linking frame rate and vection asymptotes at 60 frames per second (FPS), but previous studies have used only moderate frame rates that do not approach the limits of human perception. Here, we measure vection using subjective and objective (mean frequency and path length of postural centre-of-pressure (COP) excursions) responses following the presentation of high-contrast optic flow stimuli at slow and fast speeds and low and ultra-high frame rates. We achieve this using a novel rendering method implemented with a projector capable of sub-millisecond temporal resolution in order to simulate refresh rates ranging from very low (15 FPS) to ultra-high frame rates (480 FPS). The results suggest that subjective vection was experienced most strongly at 60 FPS. Below and above 60 FPS, subjective vection is generally weaker, shorter, and starts later, although this pattern varied slightly according to the speed of stimuli. For objective measures, while the frequency of postural sway was unaffected by frame rate, COP path length was greatest for 480 FPS stimuli. Together, our results support diminishing returns for vection above 60 FPS and provide insight into the use of high frame rate for enhancing the user experience in visual displays.