From the "gold or blue dress" to “laurel or yanny”, we love a good illusion. It’s a great reminder of how easily our senses can be tricked. Now, a new optical illusion has become popular on Twitter this week. Designed by Professor David Novick from the University of Texas at El Paso, it asks a simple question of the viewer: What’s the color of the spheres in the image?
They appear to be red, green, and blue, although a more delicate hue compared to the red, blue, and green lines around them. However, the spheres are actually all the same color: a light-brown (specifically RGB 255,188,144). It is the lines that cross them that give them the illusion of being different colors.
The effect is amplified when the image is smaller, essentially a perfect optical illusion in the age of smartphones. On a larger screen, you can see that the confetti, as Novick calls them, are not the color one sees at first, although they remain a bit tinted. As Phil Plait explains in his article about the illusion on SyFy, we are deceived by this illusion because our brains not only process colors individually but also within the context of nearby colors.
This kind of optical illusion is known as a Munker-White Illusion. When tricks like this are done in greyscale, they are known as a White’s Illusion.
A particularly stunning example of a Munker’s Illusion was created a few years ago by Akiyoshi Kitaoka, a professor of Psychology at Ritsumeikan University in Japan. It’s a three-color spiral and yet everyone sees four: magenta, cyan, orange, and green. The truth is that there is no cyan. When the green spiral is between the magenta line, the green appears bluish.
If you want to see an even trippier illusion, check out “The Rabbit Illusion” below.