It was the dress which sparked a global debate.
Now scientists have finally explained why people couldn’t agree on the color of “that dress.”
When the dress went viral in 2015, millions of people – including fashionistas Taylor Swift and Gigi Hadid – were divided whether its true colors were gold and white or black and blue.
Now, in a new study, neuroscientist Pascal Wallisch concludes that the differences in perception are down to our assumptions about how the dress was illuminated.
Those who thought that the dress, worn by the mother of a bride at a wedding in Scotland, was photographed in a shadow most likely saw the garment as gold and white.
But those who thought it was illuminated by artificial light were more likely to see it as black and blue.
He suggested these differing perceptions could be linked to a person’s exposure to daylight.
People who get up and go to bed early, and spend many of their waking hours in sunlight are more likely to see the dress as white and gold than night owls, whose world is illuminated not by the sun, but artificial light.
Wallisch, clinical assistant professor in New York University’s Department of Psychology, said: “The original image was overexposed, rendering the illumination source uncertain.
“As a result, we make assumptions about how the dress was illuminated, which affects the colors we see.
“Shadows are blue, so we mentally subtract the blue light in order to view the image, which then appears in bright colors – gold and white.
“However, artificial light tends to be yellowish, so if we see it brightened in this fashion, we factor out this color, leaving us with a dress that we see as black and blue.
“This is a basic cognitive function: to appreciate the color on an object, the illumination source has to be taken into account, which the brain does continuously.”
The findings, based on an online study involving more than 13,000 participants, was published in the Journal of Vision.
The study’s participants, who had previously seen the dress, were asked whether or not they believed it was in a shadow.
These beliefs – about whether or not the dress was in a shadow – strongly affected the “perceptual experience” of the dress.
Among those who saw it in a shadow, four out of five participants believed it to be white and gold; by contrast, only about half of the participants who didn’t see it in a shadow saw the garment bearing these colors.
Wallisch then considered what could explain the findings.
To test his night owl/morning lark hypothesis, he asked participants if they go to bed early and feel best in the morning or if they like to sleep in and feel best at night, then matched this self-identified circadian type with how they saw the dress.
Consistent with the hypothesis, early risers were significantly more likely to see the dress as white and gold – relative to night owls.
Wallisch said: “This suggests that whatever kind of light one is typically exposed to influences how one perceives color.”
He said demographic factors, such as gender and age, had comparatively little effect on the perception of the dress image.
Wallisch said the findings broaden our understanding of how a ‘bistable stimulus’ – one fundamentally ambiguous and open to subjective interpretation – works in color perception.
And he said the findings offer new insights into a long-standing question about color perception: Is the color you see the same color as someone else sees?
Wallisch added: “The answer – based on this research – is ‘not necessarily.’
“If illumination conditions are unclear, your assumptions about the illumination source will matter, and those might depend on lifestyle choices, such as when you go to sleep.”
Want to find out if you care creative, kind or imaginative? Take our color test for the answer.
If you want to keep on frying your brain, check out ten of the best ten optical illusions.
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