Benham's Top

Benham's Top is a circular design, meant to be represented on the upper part of a spinning top, completely designed in black and white. When the spinning top rotates above a certain velocity, it is possible to see arcs of colors inside the rotating circle (even though the design does not contain any colors at all).

This illusion, also called Benham's disk, was invented and commercialized in 1895 by toymaker Charles Benham, who sold spinning tops with this drawing.

Every person can see different colors, although some of them (e.g. green) are more common than others. They are typically Fechner colors (also known as PIFC, or Pattern Induced Flicker Colors).

The phenomenon is not yet fully understood, but it appears to be controlled by the primary visual cortex (pattern recognition) and the blue-yellow opponent process. Researchers are also studying whether this illusion can be used as a diagnostic tool for certain visual diseases, and it appears most promising for the diagnosis of optic neuritis.

Design of a Benham's Top, you can print it on a rotating object, or spin it with software to experience the illusion