An optical illusion on par with The Dress is making the rounds online: a photograph of strawberries that appears red without a single red pixel in the image.
Akiyoshi Kitaoka, a Professor of Psychology at Ritsumeikan University in Japan, specializes in optical illusions and has been making them for over a decade. It might be hard to swallow the truth, but there is no red in this photo at all, only pixels of color that appear red relative to the other colours.
Kitaoka's picture uses something called colour constancy. To understand the concept, it's helpful to consider the brain's purpose and how it functions. The goal of your brain is not to memorise and record every piece of data it receives—that would be impossible—but to generate a complete picture of the world that we can recognise and understand.
In the case of colour, specialised neurons in the primary visual cortex compute ratios within the eye's cone cells, which are responsible for colour vision. A breakthrough in understanding the concept came in 1967 by studying goldfish. "If the cell is excited by red light in the center," wrote Nigel Daw in '67, "then it will also be excited by green light in the periphery, and inhibited by green light in the center or red light in the periphery."
In other words, your eyes will send colour signals to your brain partially based on other colours it sees and the relative difference between those colours. This is why you can look at an entirely green-gray photo and see red.
h/t Motherboard
