Two years ago an image of a dress broke the internet, inspiring memes and raising arguments until a scientific explanation gave the optical illusion merit.
This year a photo of strawberries has sparked a debate over colour and how our brains perceive it.
Riddle: How many people do you see in this photo?
The image was created by the Professor of Psychology at Ritsumeikan University in Japan, Akiyoshi Kitaoka, who specialises in optical illusions and shared by Neuroscientist Matt Lieberman on Twitter:
This picture has NO red pixels. Great demo of color constancy (ht Akiyoshi Kitaoka) pic.twitter.com/pZHvbB6QHE— Matt Lieberman (@social_brains) February 27, 2017
Seems like a normal image of strawberries on a plate, right? Wrong. The photo has no red pixels in it, according to Lieberman’s tweet.
Unlike the dress, this image appears the same to each eye – grey scale with a hint of green and red – yet both the photos share the same colour constancy phenomenon.
Basically our brain colour corrects according to filters inflicted through different light.
According to a visual perception expert at the National Eye Institute, Bevil Conway: "If you imagine walking around outside under a blue sky, that blueness is, in some sense, colour-contaminating everything you see."
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"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,” he explains.
"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," Conway told Motherboard. "Your 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."
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Defining how our brain corrects the world around us based on our perception of it, Conway said that “this illusion is also helped out by the fact that we recognise the objects as strawberries, which we very strongly associate with the colour red, so our brain is already wired to be looking for those pigments.”
This article originally appeared on the Motherboard.com.
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