Perceptual Illusion

The illusion is called the Ebbinghaus Illusion. Two center circles of equal size are surrounded by circles of the same size, but the left outer circles are bigger/smaller than the right outer circles. The effect is that people perceive the center circle with the smaller orbiting circles to be bigger than the other circle of the same size.

The illusion plays with the idea of relative perception. Because one circle is surrounded by larger circles than the other, it seems as if that circle is also larger than the other circle, but in reality, they are both of the same size. The illusion’s effectiveness obviously depends on the sizes of the surrounding objects, but the distances between each of the circles also factor into the illusion. It has been hypothesized that the illusion is related to different processing pathways for perception and action, though exactly how is under debate.