Warring factions broke out online Thursday night, angrily waving flags of white and gold or black and blue. A bad photo of a striped dress popped up on Tumblr yesterday, and it exploded social media sites through the night, even splitting families into conflicting camps. Others swore the colors shifted back and forth in an optical illusion worthy of David Copperfield.

The black and blue supporters were vindicated when another photo of the same dress, in slightly better lighting, definitively showed its true colors. Still, knowing the colors doesn’t necessarily change how a person perceives the dress.

“Your brain perceives different colors in an image based on their context within that image and based upon our previous experiences with daylight and shadows,” said Michael Fox, a neuroscientist at the Virginia Tech Carilion Research Institute. Fox is an expert on the neural circuits underlying visual system function. “If your brain assumes the dress was photographed in a shadow, it compensates and you perceive a white and gold dress. If your brain interprets the photo as being overexposed or in extremely bright daylight, your brain compensates in the other direction and you see the black and blue colors.”

Our eyes aren’t playing tricks, then. We’re all taking in the same visual information – we all see the same colors. It’s how our brains rank the surrounding information that decides the colors we perceive.

Then why do the colors seem to shift for some people? There’s a lot of surrounding information that we’re taking in. It’s not just the apparent shadow cast on the dress, or the light flare to the right of the dress. There’s also the light from the rooms we’re sitting in, the light from the devices on which we’re viewing the dress, the tilt of the screens, the tilt of our heads, whether we’re wearing glasses. All of these little things heavily influence how our brains choose to interpret the image. The image above, from Wired, shows how the dress can appear to change colors.

Basically, we’re all right. Just some of us are more right.

For more fun and confusion, check out these color illusions from the Lottolab Studio, a perception research group.

Disclaimer: I’ve seen the other photos. I understand the optical illusion of colors and shadows. I know, empirically, the dress is blue and black. And, yet, I still see white and gold.