The secret of the blue-and-black or white-and-gold dress

We can all agree that it’s a dress. But what color is the dress? The answer may depend on three things: how your eyes are built, the context in which you view the dress, and how your brain perceives color.

Do you see a blue and black dress? Or is it white and gold? Perhaps you are in the ultra-minority of seeing a blue and gold frock.

Either way, the dress that broke the internet is one of the best optical illusions that neuro-opthalmologist Lisa Lystad, MD, has seen in a long time.

“It’s a really good color optical illusion,” Dr. Lystad says.

The eye works very much like a camera, Dr. Lystad says. Light comes in through the cornea in the front of the eye, goes through the lens and then hits the retina. Structures called rods and cones in the retina turn light waves into neurochemical energy, which is sent to the brain.

It’s the six million to seven million cones in the retina that perceive color, while rods help us see in the dark. But everyone’s cones are distributed differently, which can account – at least in part – for differences in each person’s color perception of the dress, Dr. Lystad says.

“It turns out that not everybody’s cone density is the same, even if they have normal color vision,” she says. “When you look at the retinas of people with normal color vision, the density of the cones versus the rods is not identical in everyone.”

Also affecting how people perceive the dress is what background people are viewing the color against and how bright the background is. Dr. Lystad says she notices that the background on the right side of the photo is overexposed, while the left side of picture is very dark. The side you use as a visual reference can influence how you perceive the dress’s color, she says.

“Color is relative to what’s next to it,” Dr. Lystad says. “You can take a little square of gray and put it on different color backgrounds, and it will look like a change of color. It depends on what color the square is sitting next to.”

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