A guest post by Matt Heard

Earlier this week, a photo of a dress was posted on Tumblr and made many viewers feel crazy and angry. To many, the dress was clearly coloured blue and black. But to their coworkers, friends, and spouses, the dress was obviously coloured white and gold. Both tribes were convinced that they were right and could not even understand how anybody could think otherwise. Some felt like someone was playing a coordinated prank on them, others thought that website operators were swapping out the photos so that some saw one photo and others saw another. But actually, people just saw it differently.

Experts on vision explained this illusion as being caused by the colour constancy effect. If you shine a red light on a white object, it looks red. But if you shine a red light on a red object, that also looks red. Your brain sees the red object in the red light and makes an automatic assumption that the redness is from the light and not the object itself. So, even though you’re looking at a red object, your brain subtracts the red light and concludes that the object is white. With the photo of the dress, there are ambiguous indications about the colour of the light. Some think it’s blue light (or shade), subtract the blue, and see white and gold. Others think it’s bright white light, subtract the overexposure in the photo, and see blue and black. Many tried and failed to see it the other way. Once their brains had performed the pre-processing, it was nearly impossible for viewers to convince themselves that it could be seen differently.

In a recent episode of This American Life, producer Robyn Semien met up with a friend who worked with the NYPD and watched a video of a 160kg man named Eric Garner being restrained and arrested. They each saw something different. Last year in Staten Island in New York, Garner was approached by plainclothes officers and he loudly accused them of harassing him. One of the officers reached out for Garner’s arm and Garner batted the officer’s arm away. Another officer came from behind Garner and placed him in a choke-hold, restricting him. With other officers assisting, Garner was brought to the ground and forcibly held down as the officers arrested him. While held down, Garner repeatedly gasped “I can’t breathe.”

Semien and her friend both watched the same video, multiple times, but came away from it with completely different interpretations. “We watched it over and over. She only saw it as him not complying, … wrestling and refusing to be arrested. And I can only ever see it … as the opposite. I can only ever see it as … a person who seems thoroughly detained. … I’m thinking at this point, it’s under control… And she’s like, it’s clearly not under control and there is more force to be applied.” She discusses it with This American Life host Ira Glass:

Ira Glass: And does she understand why you see it the way you do?

Robyn Semien: No.

Glass: She thinks that when you look at it, you should see it the way she sees it.

Semien: Yeah.

Glass: And did it make her mad that you couldn’t see it?

Semien: Yeah. Yeah, it did.

Glass: Because to her it’s obvious.

There are plenty of optical illusions that have multiple, reasonable interpretations: outlines that look like both vases and faces, paintings that can either be of landscapes or people, silhouetted animations of ballet dancers spinning both clockwise and counter-clockwise. Ludwig Wittgenstein made the rabbit–duck illusion famous when he included it in his analysis of perception in Philosophical Investigations. These illusions are each interesting in their own right but it is important to distinguish here that these were designed to be illusions. They are purposefully ambiguous and do not have a “true” answer. The rabbit–duck illusion is not a picture of a rabbit or a picture of a duck as much as it is a picture intended to make some people see rabbits and some people see ducks.

The photo of the dress is not designed to be an illusion. Someone took a photo of a real dress which was made to be worn. Because the photo was taken in poor lighting with wildly incorrect white-balancing, the photo was distorted in an unintended way to trigger the colour constancy effect to trick everyone into seeing the dress in different ways. Unlike with the rabbit–duck illusion, when we ask what colour the dress is, there is a “true” answer: the dress is blue and black, not white and gold. When we ask ourselves what happened to Eric Garner, there is also a “true” answer: Eric Garner was killed by a police officer with an unreasonable amount of force. The New York City medical examiner who investigated Garner’s death concluded that it was primarily the choke-hold and the force of pressing him against the ground that caused his death. Former chief medical examiner Michael Baden commented that “obese people especially, lying face down, prone, are unable to breathe when enough pressure is put on their back.”

Police officers spend a lot of time dealing with perfectly healthy suspects trying to avoid or delay arrest by claiming they cannot breathe. Any reasonable, caring person exposed to this would harden their responses and become cynical. Experience hasn’t changed just how police officers react to situations, but how they literally see those situations. This American Life described it succinctly when they titled the show episode “Cops See It Differently”. Even after everybody found out that Eric Garner actually could not breathe, Robyn Semien found it odd that her friend from the NYPD could not quite admit that Garner had even experienced breathing difficulties. When a reasonable police officer and a reasonable journalist see something so differently, it casts a terrifying doubt over whether it is even possible to determine how a “reasonable” person would interpret something.

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This above image is:

“Twelve Birds”, by M. C. Escher (1948).



Matt Heard is a software developer and philosopher from Wellington, New Zealand. You can read his blog here or follow him on Twitter @mattheard.