Examination of the Effect of the Real-life Meaning of the Stimulus on Self Motion Illusion

Vection refers to illusory self-motion perception mainly induced by the motion of a visual stimulus. This phenomenon concerns presence and immersion in the illusion of self-motion, especially in virtual reality. In the present study, we investigated how the real-life meaning of stimuli contributes to vection by using animations of objects that can move by themselves. In two psychophysical experiments, we first employed animated cars presented with or without wheel rotation as the visual inducer, which had various motion directions and postures; then we added the road scenery, which was either moving (in the same or opposite direction to the cars) or still, as a contextual background in the visual stimulus. The results of Experiment 1 showed that in conditions with forward- and backward-moving cars, vection was stronger than in conditions with upward-moving and inverted cars. The results of Experiment 2 showed that vection was weakest in the still road scenery condition and that the cars' wheel rotation could facilitate vection. This suggests that the more natural the stimulus meanings were, the stronger the vection was. It is a feasible and effective application prospect to enhance the vection experience by changing the naturalness of the stimulus to further increase the sense of presence and immersion. Therefore, the perceived naturalness and the assumed staticity of the visual inducer are two important cognitive factors in visual selfmotion perception and presence in the virtual world.