Why do we see #TheDress differently?

In 2015, an image of a certain dress immediately became a viral sensation. The internet was collectively amazed that people could look at the same stimulus and see it differently. Some people swear it is blue and black and others say white and gold.

To explain why this happens, let's start with some bananas.

What color do the bananas appear? Yellow, yes? They appear to have a blue light source shining on them, but the bananas clearly look yellow.

However, if we focus on a small region and can’t see anything about the overall lighting, the stimulus that LOOKS yellow turns out to actually be grey (feel free to use the eyedropper tool to check my work).

There is no spot on this screen that you would call a good example of yellow if you viewed it on its own. That means your eyes are sending  signals consistent with gray up to your brain. So why do we perceive yellow?

We’re combining those signals from the eye with the context the object is in. We know that blue light makes things look bluer than they are. So we combine the signals from the eye with our knowledge of the overall light.

We’re not seeing it as it is, we’re seeing it as we would predict it would look under normal lighting.

And your visual system is correct that if you could pull away that blue light, the bananas underneath would indeed be yellow.

We make these calculations all the time without realizing it. What reaches our eye from an object changes dramatically based on the lighting conditions. The visual system has to be able to see past the lighting conditions and make guesses about the nature of the objects underneath. 

It would be a very confusing world if we thought objects themselves were spontaneously changing color whenever the ambient light changed. The job of our visual system is not to be a light meter, it is to help us predict what is out there in the world. Our ability to predict what an object is depends on the conditions we think it is appearing in.

With these grey bananas, we all agree that the ambient light is blueish. With #TheDress, we don't agree.

Although people perceive the dress to be white and gold or black and blue, if we look at each region in isolation, neither description seems quite right.

The light coming off the screen would best be described as brown and cornflower blueish gray. So if we agree about the colors in isolation, why do we come to different conclusions about the object of the dress itself?

The debate comes in part from disagreement about the nature of the ambient light in the photograph. Take another look and think about whether the light in the top right corner is sunlight or artificial light inside a store. People disagree about this in ways that affect what they perceive. 

Let’s focus on this white/blue region and unpack two different ways of interpreting it. The slight blue tint from the cornflower section is reaching all of our eyes, and our eyes are sending signals consistent with cornflower blue to our brains. What seems to be up for debate is whether that greyish blue is caused by the fabric of the dress or the nature of the ambient lighting.

One path to getting that cornflower blue grey is for a white object to be bathed in slightly blueish light, similar to natural sunlight coming through a store window and putting the dress into shadow.

Another way to get the cornflower blue grey is for a dark blue object under bright, white artificial light, like you would see inside a store.

That is, if you assume blue tinted daylight, the only way to achieve cornflower is for the dress to be white. If you assume white light, the dress must be blue.

The photograph is relatively low-quality and the nature of the light source is indeed ambiguous. Both explanations are possible, and could lead to the same light coming off the screen.

Here’s another demonstration. Assuming blue light leads the dress to look white. Assuming white light leads the dress to look blue. But what is reaching your eyes is the same.

How you interpret the signals from your eye depends on what you assume about the light.

It’s not entirely clear why we differ on the nature of the light. It might have to do with how much natural daylight we see—people who tend to see more artificial light may assume the dress is in artificial light—but that can’t entirely explain the effect. So when we look at the dress, our minds are combining the information we’re getting from our eyes with our inferences about lighting. We are attempting to reverse engineer what is out in the world based on the limited and often ambiguous input that reaches our eyes. 

Examples like the dress are exciting because they remind us that color lives in our minds, not in external objects.

We each walk in our own perceptual worlds and we see things differently.

It’s impossible to inhabit someone else’s perceptual world and see it as they do, the best we can do is tell each other about our experiences. It’s like sending postcards from places you’ve never been. Variability doesn’t need to be a source of contention!

Perceiving things differently from one another isn’t something to argue about, it’s something to marvel about!