In this era of polarized politics and red state vs. blue, we can all agree on one thing, can't we? The strawberries in this photo are red.
True, the berries would appear red in real life. But in this viral Internet photo, the red color has been "desaturated" — essentially, removed — by Akiyoshi Kitaoka, an experimental psychologist in Kyoto, Japan.
Don't believe us? Try playing with the saturation levels in Photoshop. Or, for a more low-tech test, cut a small hole in a piece of paper and hold it over the photo so you can see only one berry, and none of the surrounding image. The fruit will have a grayish hue.
The berry baffler comes two years after another optical illusion that broke the Internet, the celebrated blue-and-black dress that millions swore was actually white and gold.
A similar phenomenon is going on here, said Thomas F. Shipley, an associate professor of psychology at Temple University.
Strawberries appear to be reddish, though the pixels are not. pic.twitter.com/Ginyhf61F7
— Akiyoshi Kitaoka (@AkiyoshiKitaoka) February 28, 2017
Our perception of an object's color is a combination of its surface properties and the wavelengths of light shining on it. The brain is constantly making adjustments depending on the light source, said Shipley, who has researched object recognition and other elements of the visual system.
If someone wearing white shirt is bathed in purplish shadow, for example, we still see the shirt as white. Ditto for the berries, which appear in the photo to be bathed in cyan, or bluish-green, light, he said.
"Because they're in a scene where everything is sort of bluish, the visual system sort of discounts the blue," Shipley said.
Mitchell S. Fineman, a retinal specialist at Wills Eye Hospital, agreed.
He said Kitaoka may have chosen to emphasize cyan in the photo because it is the "opposite" of red — meaning it lies more or less opposite the color red on that color wheel you may have seen in art class.
"He's basically put an overlay of cyan over the entire photograph," Fineman said. "What your brain does is, it almost subtracts it. It replaces it with its complement. It auto-corrects, if you will, by filtering out the cyan."
To a lesser extent, Fineman said the berries might appear red because we know they are supposed to be that color. But he and Shipley speculated that the effect would still work even if Kitaoka had used red balls instead of berries.
Another wrinkle: the phenomenon might not work for people with certain kinds of color-blindness, Fineman said.
So why do humans perceive color? One possible explanation is the fact that fruits made up a significant part of the diet for our ancestors. Bright fruit colors and the ability to perceive them could have co-evolved in a way that was mutually beneficial, Shipley said.
"Color is helpful in finding ripe fruit," Shipley said. "Plants want their fruit found because they want their seeds spread around."
See more of Kitaoka's mind-bending illusions here.