What color is this dress? -- And why do some see it as white and gold and others see it as black and blue? Here's the dress (and keep reading, this is actually a serious question):



This question about this image has apparently become quite a rapidly spreading meme on the internet. And after conducting my own little home experiment I can see why! My brother an law looked at this image on the same screen as I did and said matter-of-factly that the dress is black and blue. I, on the other hand can't see this as anything but gold and white. I tried this question with a few others with similar results.

So the question is... what is going on here? What is causing this to either appear strongly as black and blue or gold and white?
My hypothesis: The world accidentally stumbled upon the first (to my knowledge) bi-stable color illusion

Here is an example of bistable illusion:



This bistable illusion involves the perception of motion. Is the dancer spinning clockwise or counterclockwise? The deal is that the image is actually ambiguous. But you can't possible perceive both clockwise or counterclockwise motion at once, so you are automatically drawn to one and it's hard to switch off to the other.

And here is an example of a color illusion:



Amazingly the "blue" in the left cube and the "yellow" squares in the right cube are both the same color - grey! (Go ahead and take out your RGB color meter and see for yourself.) And the effect here is caused by the "context" of the color placed over the images of the cubes.

I'm thinking that somehow an ambiguous background to that dress image and the possibility for a fabric that has a sheen, is leading us quickly come to the subconscious conclusion that this is either a black/blue dress under bright yellow-tinted light or a gold/white dress that is in a bluish shadow. And whatever conclusion we start with is so strong that we can't break from it or see it any other way.