Perception of Self-Motion Induced by Moving-Dot Patterns: The Interaction of the Stimulating Area and the Speed of the Pattern

A linear moving-dot pattern was presented to observers to induce self-motion. A stimulating circular area of more than 28.1 deg diameter induced self-motion perfectly, and even areas ranging from 5.7 deg to 11.4 deg diameter were able to elicit self-motion (Kano, 1995 Perception24 Supplement, 108). In the present study the interactive effects of the size of the stimulating area and the speed of the moving pattern on the perception of self-motion were examined. Random-dot patterns were moved downward in a circular area on a screen in a dark room. The diameters of the circular area were 5.7, 11.4, 22.6, and 43.6 deg. The speeds of the dot pattern were 9.49, 18.85, 28.07, 36.73, and 45.08 deg s−1. Observers were twenty-six students of Keio University. When the size of the area became larger and the dot pattern moved faster, self-motion was generally induced with shorter latencies. However, a significant interaction was found between size and speed; for the smallest area (5.7 deg diameter circle) latency was shorter at the lower speeds (9.49 to 28.07 deg s−1) than at the higher speeds (36.73 and 45.08 deg s −1). For the 11.4 deg diameter circle speed had no effect on latency. For the 22.6 deg diameter circle, however, latency decreased with increasing speed. For the 43.6 deg diameter circle latency was very short and constant under the four higher speeds, but remained considerably longer at the lowest speed. The results show that the effect of speed depends on the size of the stimulating area. When the size was large enough, speed had little effect on the latency of self-motion.