Elongation Illusion of Line Segment by Alternate Display of Two Images

Abstract

We discovered a new illusion in which line segments on a single-color background are perceived as if they are continuously extended when alternately displayed with their tonally inverted images for about 120 ms each. For example, image A has a white background and black line segments, and image B is the tonally inverted version of image A. Image A and image B are displayed alternately. Although a single line segment is acceptable, multiple line segments are placed in parallel to each other to increase the illusion. The background color can be red, blue, green, etc. instead of white to create the illusion. In addition, there are cases in which the line segments appear to contract rather than to extend. The mechanism of this illusion is unknown at present.