What colour is that dress - white and gold, or blue and black?

IS IT white and gold, or blue and black? Visual experts are as confused as the punters by “the dress” illusion that has gone viral.

What colour is this dress? It's gold and white

VISUAL experts are as confused as the punters by “the dress” illusion that has gone viral on social media, attracting thousands of tweets and Facebook likes.

A Scottish singer posted a picture of a dress on image-sharing site Tumblr, together with a plea for help: “Guys please help me — is this dress white and gold, or blue and black? Me and my friends can’t agree and we are freaking the f**k out.”

The social media world proved equally split. A poll by website BuzzFeed revealed that 75 per cent saw white and gold, while 25 per cent saw blue and black.

“A smaller percentage saw periwinkle and olive green, or black and yellow,” reported Sydney pop culture site TheVine. “Yet another percentage saw this all as a massive waste of time.”

TheVine said its colour-picking machine had pegged the dress as “light blue with browny-gold lace”.

University of Melbourne visual scientist Andrew Metha said the phenomenon had also stumped his department. “I’ve polled about seven of my colleagues now — the blues are winning (but) it’s got us puzzled.

“This is a great illusion, and I’m not surprised to learn it is going viral.”

Dr Metha said the confusion highlighted the “unconscious” assumptions people made when they were processing visual information.

“The first thing to assume is the nature of the illuminant under which the photograph was taken — was (it) in full sun, under clouds or indoors lit by incandescent lights?”

He said each of these conditions involved very different light wavelengths. “This issue is something our brains have to deal with all the time as we move through different environments.

“Vision scientists and psychologists have coined the phrase ‘colour constancy’ to describe the phenomenon by which an apple, for instance, retains its colour under such widely different lighting conditions, even though the actual distribution of photon energies raining onto our retinas in each case can be very different.”

Dr Metha said exactly how humans managed had long been a hot issue at vision science conferences, with some theories going back over 150 years.

He said people also made assumptions about the nature of the reflection from the material. Materials like satin or taffeta silk were “naturally very shiny” while matte felt and T-shirt cotton were “diffusely reflective”.

“How we ultimately perceive the dress photo, particularly the darker parts, will depend on what type of material we assume this part of the dress is made of,” he said.

“There is not enough information in the photo to be sure.”