The Square in This Optical Illusion Isn’t Actually Changing Color

This optical illusion reveals how a person’s brain can change the color of the objects that they see.

Experimental psychologist and artist, Akiyoshi Kitaoka, from Kyoto, Japan, posted a clip of the optical illusion on Twitter to show how moving objects can trick the human brain into guessing their color rather than observing it accurately.

In the image, created by Kitaoka, a small square can be seen traveling across a rectangle that’s half pink and half blue, with a blended combo of the colors in between.

The quadrilateral appears gray while moving in the pink space, then seemingly adopts a pink hue when in the blue.

However, as Kitaoka explains in the caption, while the “moving square appears to change in color,” the color of the moving square “is constant.”

The human mind thinks that the square changes from a greyish color to a pink hue. However, in reality, the square remains the same color, which is pink.

This is because the movement of the square and the colors it’s traveling through trick our brain into thinking this.

The human brain makes an assumption about the color of the moving object based on the objects surrounding it. This, in turn, proves that a human’s perception of color is subjective.

This chameleon-esque effect is explained further in a 2016 study authored by Sang-Wook Hong and Min-Suk Kang in the journal Nature.

In the study entitled “Motion Alters Color Appearance,” Hong and Kang explain how this optical illusion is caused by a principle called the chromatic induction effect — a perceived color shift that occurs “when one colored object moves around an identical stationary object.”

“The perceived saturation of the stationary object decreases dramatically whereas the saturation of the moving object increases,” the authors write. “These color appearance shifts in the opposite directions suggest that normalization induced by the object’s motion may mediate the shift in color appearance.”

Therefore, humans’ perception of color is not absolute. This can lead to divisive optical illusions where people see different colors in an image — such as “The Dress”, which became a viral sensation in 2015. Viewers of the image disagreed on whether the dress depicted was colored black and blue, or white and gold.

Kitaoka originally posted this clip in 2018 but it is currently recirculating on Twitter with social media users left astounded by the optical illusion.

This is not the first Kitaoka has broken the internet with an optical illusion. In 2018, Kitaoka posted a photo featuring a medley of strawberries, which had viewers racking their brains trying to decide what color they were.