It’s that time of year again; when a photo shows us all how broken/amazing our brains are. An image has gone viral of a bowl of strawberries appearing red to the human eye when in actuality it is entirely made up of grey (and a few green) pixels.
This new visual brain teaser comes to us courtesy of Akiyosha Kitoaka, a Professor of Psychology at Ritsumeikan University in Kyoto, Japan. He posted his fruity creation to Twitter where viewers failed to believe what they were seeing.
2色法によるイチゴの錯視。この画像はすべてシアン色（青緑色）の画素でできているが、イチゴは赤く見える。
— Akiyoshi Kitaoka (@AkiyoshiKitaoka) February 28, 2017
Strawberries appear to be reddish, though the pixels are not. pic.twitter.com/Ginyhf61F7
The mechanism in your brain that is allowing you to see red when none is present is similar to a faulty white balance in your head. The phenomenon is called colour constancy. It is the same reason people lost their minds looking at “the dress” in 2015. It is in effect, your brain’s attempt at colour correction.
Generally your eyes are taking in a vast amount of visual information, including light at various wavelengths. Surrounding lighting elements can provide filters that change how that information is processed. Your mind requires these functions to put visuals in context and to simply make sense of what it seeing. Otherwise every time one of those filters changed you wouldn’t see an object’s colour the same.
Speaking with Motherboard, Bevil Conway from the National Eye Institute explained it thusly:
“If you imagine walking around outside under a blue sky, that blueness is, in some sense, color-contaminating everything you see. If you take a red apple outside under a blue sky, there are more blue wavelengths entering your eye. If you take the apple inside under a fluorescent or incandescent light without that same bias, the pigments in the apple are exactly the same but because the spectral content of the light source is different, the spectrum entering your eye that’s reflected off the object is different.”
So how is it that these strawberries still look red when all the information our brains are being sent is in grey? Well that’s because your brain has locked-in versions of those colours it uses as a reference. You (hopefully) know that a strawberry is red, so you adjust your perception of the image to work with that expectation.
Conway explained to Motherboard
“In this picture, someone has very cleverly manipulated the image so that the objects you’re looking at are reflecting what would otherwise be achromatic or grayscale, but the light source that your brain interprets to be on the scene has got this blueish component. You brain says, ‘the light source that I’m viewing these strawberries under has some blue component to it, so I’m going to subtract that automatically from every pixel.’ And when you take grey pixels and subtract out this blue bias, you end up with red.”
We apologise…but your Facebook feeds are gonna be seeing red for days to come.