Why Julianne Moore and Taylor Swift See That Dress Differently

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As a visual neuroscientist I think a lot about how we see the world around us. And so I’ve found the scientific and celebrity controversy to be especially fun and exciting. Most of the scientific pundits have concluded that the dress is black-and-blue, and they have offered up an illusions-in-the-brain explanation of why some people see the dress instead as white-and-gold. Yet after thinking thoroughly about this photo, looking at it on a number of different screens, and speaking with some of my lab partners, I’d like to offer my point of view. Yes, there is an illusion at play here that effects our brains, but no, it is not that illusion that causes it to look differently to different people: that difference is caused by a mundane photographic effect.

First, the illusory explanation (it’s black-and-blue but only appears white-and-gold) arises from what we scientists call “color constancy.” It’s the process by which we can recognize the same object under different light sources. My favorite example of this effect is from , and is shown in the image of the Rubik’s Cube. You see the brown central chip on the top and the orange central chip on the front-face? In fact they are identical in color and only different because of their context: the brain does a computation of the lighting on each surface and calculates the surface properties of each chip based on those lighting properties. This illusory process helps you determine the color of things irrespective of the light source. So I agree that my colleagues are not wrong that the brain can do amazing tricks in your brain that make objects look surprisingly different under different lighting conditions.

Courtesy of Beau Lotto and Dale Purves

But that doesn’t mean that’s what’s happening with the dress. It’s a poor image to work from, but perhaps if we analyze the photo more closely with an eye to determine the nature of the lighting sources, it will inform our decision.

The best analysis of the image I’ve seen so far was done by photo editor Neil Harris, in . The team did a Photoshop analysis in which they analyzed the colors from different parts of the image and, most importantly, varied the white balance of the image. They showed that the dress looks different depending on the white balance. You can also prove this to yourself by simply squinting while viewing the original image on Tumblr… it turns from a white-and-gold image to black-and-blue.

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So this explains why different people see it differently: they are looking at it on different screens set to different brightnesses (or white balances). It has nothing to do with your brain—it’s just an optical issue of light transmission. This also means that we may not need to invoke an illusory process in the brain at all, and that we could potentially identify the nature of the dress through a photographic analysis.

Note that changing the white balance is not changing the colors. Why would black lace look golden, and not green or red, when you crank up the luminosity? Shouldn’t it be gray? Given all the speculating everyone’s been doing, I’m surprised that nobody’s mentioned specularities. These are the mirror-like reflections on the shiniest part of any the object. They provide the best clue of the light source shining on an object, because they are literally reflecting the purest available sample of photons that came from the source. So by analyzing the specularities, we can see what color the lighting is. And when we see what color the lighting is, we can then determine what color the cloth of the dress might be. This matters when you think about the brain because, as you saw with Purves and Lotto’s Rubik’s cube, how we see light dictates how we interpret the world around us, whether it’s outside, inside a store, or on your smart phone screen. It’s an imperfect analysis of course, because the specularities are not perfect mirrors—they are also affected by the cloth’s color itself—but let’s take a look and see what we can determine.

In this case, let’s look at the jacket part of the dress in the top right of the picture. See how shiny it is? That’s where the specularities are the strongest, and there we therefore have the strongest clues to the source of light shining on an object. If you keep your eye on the shiny part of the jacket, you’ll see that its white color changes when the white saturation of the photo changes, but not otherwise.

It would be best if we could analyze specularities made from sunlight. The light that comes from direct sunlight, at midday, is more-or-less exactly known. So if we knew that the dress was bathed in sunlight, we could analyze the specularities. This would help us determine the true color of the cloth, account for different ways that different cameras might operate, or different settings on our display screens, etc. But the original photo wasn’t taken under sunlight, it was taken inside a mall, presumably by a smartphone camera. The camera in the phone likely corrected for color and brightness on its own, reacting to the bright light shining in the background, not the dress in the foreground. Yet even with the bright background, and the color correction, the specularities don’t change.

So what do we see here? Well, the specularities in the original image are bluish. This suggests the light source is either blue, or the cloth is absorbing the non-blue photons (from the lights shining in the mall), and only reflecting the blue photons. Since they aren’t, it’s possible that we are seeing a white-and-gold dress under a blue light source. So how do we know which effect is at play? Is it an illusion or is it photographic? Well, we know that the white balance effect is at play: the WIRED analysis makes that clear. So it’s photographic at least in part. But is there an illusion at play too?

I think there is. This morning I interviewed with and told her I thought that the difference between viewers must be photographic and not illusory. And that’s true. But in investigating this issue, my assistant Max Dorfman saw something interesting in the magnifying tool on the dress manufacturer’s website. The white transparent rectangle that magnifies the dress made it look white and gold, despite there being no issue of light sources. This means that the illusion of gold lace can happen with black fabric when it is surrounded by blue fabric, when a white transparent film is placed in front. From a neuroscience perspective, this means our brain is indeed applying a golden color where none exists, as a color constancy effect. So that’s it then: there is both a light balance effect (as WIRED’s demo shows), to explain why different people see different things on their different screens, and an illusory color constancy effect that contributes to why we see gold instead of gray when its surrounded by blue.

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Either way, I don’t think that the reason people see the dress is an interesting brain process. Rather, it is a mundane differences in how people have viewed the image on their electronic display screens (phones, tablets, laptops, etc). So now we know that Taylor Swift and Ellen Degeneres set their phone screens to different brightness levels than Justin Bieber and Julianne Moore. You’re welcome.