Abstract
Visual stimulus which occupies a large area of an observer's visual field and moves uniformly can induce illusory motion perception of the observer's self-body in the direction opposite to its motion (vection). Psychophysical experiment with 11 observers was executed in order to examine whether two and four stroke apparent motions can induce vection or not. It has been known that two frames of visual pattern which are slightly shifted with each other can create an impression of continuous motion toward designated direction, using luminance reversal pattern (Four stroke motion) or introducing brief blank inter-stimulus interval (Two stroke motion). Vection strengths measured by magnitude estimation were compared between conditions of the two and the four stroke motion, conventional apparent motion, and original motion sequence with 60 Hz refresh rate (real motion). Experiments revealed that both the two and the four stroke motions can induce self-motion perception with considerable strength. The four stroke motion and the conventional apparent motion can induce self-motion perception as strong as the one induced by the real motion. The two stroke motion induced weaker vection than the four stroke motion or real motion, with least smoothness of motion among the conditions. The results suggested that an observer's perception of smoothness of the visual motion would affect strength of self-motion perception.