Visual perception begins with our retinas locating the edges of objects in the world. Downstream neural mechanisms analyze those borders and use that information to fill in the insides of objects, constructing our perception of surfaces. What happens when those borders—the fundamental fabric of our visual reality—are tweaked? Our internal representation of objects fails, and our brain's ability to accurately represent reality no longer functions. Seemingly small mistakes lead to the very distorted perceptions of an illusory world.

Further Reading

Brightness Induction and the Café Wall Illusion. M. E. McCourt in Perception, Vol. 12, No. 2, pages 131–142; 1983.

Shifts of Edges and Deformations of Patterns. B. Pinna and R. L. Gregory in Perception, Vol. 31, No. 12, pages 1503–1508; 2002.