Saturday 22 October 2016

Dressgate: If you saw THAT dress as white your brain was working overtime

People who saw the dressgate illusion as white were making an extra mental leap, say scientists

Sarah Knapton

Published 15/10/2015 | 08:33

The dress
The dress

It was the dress that nearly broke the internet, with millions of people claiming they could only see white and gold lace while the rest of the world was convinced it was black and blue.

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Now scientists think they have solved the problem of why so many people, literally, swore black was white.

After placing volunteers in an MRI scanner and asking them to look at the image they noticed subtle changes in how the brain was functioning.

People who saw the dress as white and gold had extra activity in the front and parietal areas of the brain which is particularly important in visual perception, mental reasoning and selective attention.

Their brains, in other words, were working extra hard to make sense of the image, which led them to take an extra mental step and believe that the blue colour was actually a shadow on a white dress.

"These results expand our knowledge of illusion processing in the brain,” said Prof Tobias Schmidt-Wilcke of the University Clinic Bergmannsheil in Bochum, Germany.

“Based on the research findings, we were able to quantify the brain areas involved in the process, thus we have laid a foundation for further research in the field of visual processing," said Prof Tobias Schmidt-Wilcke of the University Clinic Bergmannsheil in Bochum.

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The bodycon Roman Originals dress illusion baffled the world when it was posted on Twitter in February and retweeted by Taylor Swift, the singer.

The dress was blue with black lace but because colour is simply a perception made by the brain when light hits the retina it can look different to other people.

Wavelengths get longer as they move through violet, blue, green, yellow, orange and red. However when the brain interprets these wavelengths as colour it is also doing something very clever. It is also working out how illuminated the colour is by the light around it and subtracting that from the ‘real’ colour.

It is how it is possible to distinguish between colours in bright sunshine or twilight.

Usually that system works well. But sometimes, as in the case of the Roman Originals dress, the brain gets confused.

The picture showed the dress in shadow but there is a bright white light source behind. So the picture is confusing the brain about how much correction it needs to make for the amount of light and shadow present.

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Those that saw white and gold had perceived the dress as if hidden by shadow, and therefore white. Those who saw black did not make that extra jump, and saw what was right in front of them.

Andrew Hanson, past chairman of the Colour Group of Great Britain and scientists at the National Physical Laboratory said humans are evolutionary programmed to think that objects in shadow are blue, as the light bounced back off them is coming from the sky, rather than directly from the Sun.

 "When you look at things on a sunny day, things in shadow are lit by the sky and clouds and have a more bluey tinge. It's why snow in the sunshine looks blue in shadow. So when you see the dress you could be forgiven that you are seeing something on a sunny day in shadow, and interpret it as white.

"We all have memory colours. We know that bananas are yellow for example. Similarly we know that shadow should be blue. It's nothing to do with colour blindness, it's all do to with colour perception. Essentially it is an illusion but people who see white, are actually seeing white, even though it is not really there."

The new research was published in the journal Cortex.

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