The Science of #DressGate: An Exploration of Optical Illusions, Part 1

It will be inscribed in the history books as the infamous #DressGate of 2015: The Outfit That Broke the Internet and Divided the World. All melodrama aside, over the past several days there has been a seemingly ubiquitous fixation with a photo of a dress disseminated on various social media channels.

Some people see the dress as white and gold, while others are convinced it’s black and blue. How could something as basic as an object’s color be so incredibly divisive? As always, the answer lies in the brain.

Before we get into the science of color perception, we must first begin with a rudimentary explanation of the human visual system. Light rays enter first into the cornea, which “bends or refracts the rays that pass through a round hole called the pupil.” The pupil is similar to a camera’s aperture: it automatically adjusts to let more or less light in. It simultaneously passes through the iris, which functions like a “shutter in a camera. It has the ability to enlarge and shrink, depending on how much light is entering the eye.” Next, the rays travel through the lens, which parallels the “lens in a camera, shortening and lengthening its width in order to focus light rays properly.” The rays are focused onto a portion of tissue in the back of the eye called the retina. To cement the camera analogy, the retina is similar to “the film in a camera. It is responsible for capturing all of the light rays, processing them into light impulses through millions of tiny nerve endings, then sending these light impulses through over a million nerve fibers to the optic nerve.”

Incidentally, the image that is displayed on the retina is inverted. It is your brain’s responsibility to flip the image right side up, so we see the world with more accuracy.

The parts of the eye most strongly implicated in the black-and-blue/white-and-gold dress debate are the cells that make up the retina, known as rods and cones. Cones are relied upon when we are in the presence of bright light; they “provide clear, sharp central vision and detect colors and fine details.” On the other hand, rods are used for darker light conditions, as well as for “peripheral or side vision… and [motion detection].”

Experts aren’t completely sure why there is such disparity in perceptions of the dress’s color, but many suspect it has to do with the lighting in which the picture was taken. Dr. Jay Neitz proposed a theory: “Humans are equipped with something called ‘color constancy,’ which basically means that the color red still looks red whether you’re in bright lighting or dim lighting. But something weird starts to happen if the lighting is colored.” If you look at a green object in a room illuminated by green light, your brain will perceive the object as white. “That’s likely what’s going on with the photo here: The photo was probably taken in blueish lighting, which makes your brain think that the dress is actually white.” However, this theory fails to explain why many people see the dress as blue.

David Williams, a researcher at the University of Rochester, suggests a different theory related to whether we perceive the lighting as dim or bright. He explains, “I think the brain has just made a different assumption about how the dress is being illuminated.” If you think the image was captured in dark lighting, the dress will appear reflective (white and gold). “But if your brain assumes the opposite (that the lighting is very bright), it then makes the judgment that the dress itself must be darker, hence blue and black.” He goes on to explain that these occurrences rarely happen because we almost always have access to a larger field of reference that provides context for our perceptions.

So there you have it, folks: let’s put the pitchforks down and silence the rallying cries. Our visual system is highly adaptive, but our brains will always be occasionally fallible.

This is Part 1 of a series about anomalies in visual perception. Join us next week when we investigate the science of other optical illusions.

-By Betty Vine


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