An Illusory Contour Can Facilitate Visually Induced Self-Motion Perception: Supplementary Material

Uniform motion of a visual stimulus induces an illusory perception of the observer’s self-body moving in the opposite direction (vection). The present study investigated whether vertical illusory contours can affect horizontal translational vection using abutting-line stimulus. The stimulus consisted of a number of horizontal line segments that moved horizontally at a constant speed. A group of vertically aligned segments created a ‘striped column,’ while line segments in adjoining columns were shifted vertically to make a slight gap between them. In the illusory contour condition, the end points of the segments within the column were horizontally aligned to generate vertical illusory contours. In the condition with no illusory contour, these end points were not aligned within the column so that the illusory contour was not perceived. In the current study, 11 participants performed this experiment, and it was revealed that stronger vection was induced in the illusory contour condition than in the condition with no illusory contour. The results of the current experiment provide novel evidence suggesting that non-luminance defined visual features have a facilitative effect on visual self-motion perception.