What Color is This Dress?

I suspected that's what it was from my experience, and that's what the neuroscientists who've talked about the dress believe.

So kind of like if you _know_ what it's supposed to look like, then your brain will fill in the correct color?

The secret is to look at different pictures of the same dress. once you have a reference point, you'll start to see the blue and black.

I'm with you, Ladybugs! I can only see white and gold, regardless of what I try to do (stare into the monitor, squint a bit, squint a lot and so on). Now I feel left out!

There are actually a lot of determinations (not just assumptions) regarding white balance you can make from the highlights and shadows of the image (color casts are different at the extremes depending on lighting, especially when using cheap digital sensors), the adjacent objects (the cloth right behind it), and even the flaring from the dirty lens (you can actually see the color blend from the background lighting to the material in the top right). The lighting is too omni-directional to have a blue light be hitting the dress without it hitting anything behind it. That's enough to at least confirm that the white balance and lighting isn't so dramatic that a white/gold dress would reflect a blue wavelength to the camera (since we can measure and see that the color is distinctly blue).

That's not to say you couldn't have a situation where you could genuinely fool people (see today's XKCD), but there's definitely enough information in this image to be 99% sure that it is what it.... well, let's say what it can be measured to be. :)