It was the dress that divided the world, with some people certain that it was black and blue, while others only saw it as white and gold.

Now, scientists believe they’ve solved #TheDress debate: The optical illusion is linked to specific brain activation patterns, according to a new German study published in the neuroscience journal Cortex.

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The reason the dress caused so much confusion (and possibly cost a few friendships) is because color is a complex processing cue for the brain, which can lead each person to a different conclusion of what they’re seeing.

Experts solved the riddle by placing participants in an MRI scanner and asking them to look at the image of the Roman Originals dress.

The scans revealed that the brains of people who saw the dress as white and gold had extra activity, mainly in the frontal and parietal areas, which are key to selective attention, decision-making and processing visual information.

Their brains were simply working extra hard to understand the image, and came to the conclusion that there was a shadow being cast over the dress, and therefore their eyes saw it as white.

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Those who saw black simply acknowledged what was right in front of them without taking the extra mental leap.

"These results expand our knowledge of illusion processing in the brain,” says study leader Prof Schmidt-Wilcke, of the University Clinic Bergmannsheil in Bochum, Germany. “We have laid a foundation for further research in the field of visual processing."