Vection with Degraded Real-World Stimuli

Psychophysical studies have revealed that the retinal periphery plays a dominant role in inducing vection, ie the visually induced sensation of self-motion. This suggests that the quality of the visual stimulus is not an important factor for vection. However, since abstract stimuli were used in these studies, it is not clear whether the quality of real-world visual stimuli could still play a critical role in inducing vection. We investigated how vection induced by real-world visual stimuli was affected when the stimuli were spatially or temporally degraded. Stereoscopic video clips were taken through the windshield of a car driven on a sharply curved and hilly road. These clips were degraded spatially by using a mosaic effect, or temporally by using a strobe effect on a video editing system. The perceived direction and strength of vection were measured while subjects were viewing these visual stimuli presented on a 63 deg wide and 38 deg high video projection monitor. Degradation of the visual stimuli was found to have little effect on the assessment of direction in horizontal vection. Assessment of the direction of vertical vection, however, was significantly disturbed by both spatial and temporal degradation of the stimuli. Temporal degradation reduced the strength of vection significantly for both horizontal and vertical motion. In contrast, although spatial degradation of visual stimuli reduced the strength of vection in both dimensions slightly, the effect was not statistically significant. We conclude that the spatial quality of real-world visual stimuli does not play a significant role in inducing vection.