Effects of tilt of the visual stimuli on the perception of gravitational vertical under normal- and hyper-gravity conditions

It is important to understand the mechanism to integrate visual and other information for the perception of gravitational vertical under different conditions of gravity, although most of the experiments to investigate the topic reported so far has been carried out under normal-gravity (1 G) and under micro-gravity produced in short duration of parabolic flight. The purpose of this research is to investigate human perception of gravitational vertical under hyper-gravity (1.5G and 2G) to compare that under normal-gravity (1 G). We measured perceived gravitational vertical using a visual probe presented at the center while manipulating the orientation of visual stimuli (scenery picture) presented in the surround and the magnitude of gravitational acceleration. The environment of hyper-gravity was produced by centrifugal force of a rotating flight simulator. The results show that the accuracy of perceived gravitational vertical increased and the precision of it decreased under hyper-gravity condition relative to those under the normal-gravity condition when no visual stimulus was presented. However, the effect of the tilt of visual stimuli did not change under different gravity conditions.