David Novick's Color Illusion Page: How the Munker Illusion Works

This page presents my investigation of how and why the Munker illusion works. This explanation uses the term central circle to refer to circles in my examples that show the apparent color change of the Munker illusion. The terms foreground and background framing colors to refer respectively to the colored stripes that are in front of and behind the central circles. There are two main insights:

• The illusion is a function of the foreground framing color, which tends to tint the central circle.
• The apparent color of the central circle is a mix of the foreground framing color and the circle's color

Illusion is function of foreground framing color

 The Munker illusion appears to be a function of the framing colors rather than central color. Reducing the saturation of the framing colors (left side of figure) reduces the strength of the illusion. Reducing saturation of the central color leaves the illusion intact, with minor color shifts. Amazingly, this means that the Munker illusion persists even if the central color goes to 0% saturation, i.e., white! The Munker illusion with 0% saturation of the central color appears to work across a variety of colors. Note that the illusory colors (i.e., not the actual white) reflects the foreground framing colors. The illusory central color (the circles are actually white) appears to take on some of the color of the foreground framing color rather than the background framing color. Indeed, the illusion works with changing foreground color alone. In this example, the background framing colors are the same gray, while the foreground framing colors make the central (white circle) appear tinted with the colors rust or blue. This means that the illusion has the same strength whether the background foreground color is an opposite color or just gray.

Illusion color is mix of foreground framing color and central circle color

 Because the Munker illusion is solely a function of foreground framing color, opposite framing colors produce the greatest illusion effect. So with a red central circle, yellow and blue framing leads to a bigger effect than yellow and orange framing. This can be seen most clearly with 0% saturation (white) central circles. But the lack of interesting color change rather gives the game away, showing the bare mechanics of the Munker illusion. Because the Munker illusion is a function of foreground framing color, the illusion colors are a blend of the foreground framing and the central circle. So blue foreground framing + red circle --> purple illusion color, yellow foreground framing + red circle --> orange illusion color, and violet foreground framing + yellow circle --> salmon illusion color, green foreground framing + yellow circle --> lemon illusion color.