On February 26, 2015, the internet broke.

A woman posted a photograph of a dress on social media and asked what color the dress was, as she and her friends were unable to agree and were “freaking out.”

This kind of disagreement happens all the time. I had a years-long argument with a friend of mine whether a particular shirt I owned was blue or green.  I saw it as green, she saw it as blue.  I have the same argument now with a different friend about the color of my couch. But as blue and green are on the same spectrum and the shirt could arguably have been said to have been blue-green (or was it green-blue?), that argument was simply about where an individual drew the line between the two colors.  The dress was different.

People saw the dress either as blue with black stripes or as white with gold stripes. That is not a difference between two people who simply draw the border between two neighboring colors in different places. This was a fundamental difference in the perceived nature of the dress.

Is this dress blue and black or white and gold?

Is this dress blue and black or white and gold?

And that difference caused a crisis around the globe as people took to shouting at each other that the dress was one version or another.⁠1 It upset a lot of people who could not understand how it was that other people could possibly see such divergent versions of the same reality.

Of course, the neuroscientists explained that the problem was not in our eyes, it was in our brains. We see with our brains not with our eyes. Our brain interprets visual signals received in the retina and tries to make sense of them. In this case, the difference in which colors you saw all seemed to depend on whether you perceived the dress as being in low light (as a result of which your brain interpreted the darker colors as being in shadow and saw the dress as white and gold) or whether you perceived the dress as being in bright light (as a result of which your brain interpreted the darker colors as being the true colors of the dress). The brain frequently “normalizes” signals from the retina that do not correspond with what the brain expects to see, expectations that are based on the brain’s general experience of the world, especially stored memories and habits.⁠2

This normalization of sensory input is not limited to sight alone. A well documented phenomenon known as the McGurk Effect demonstrates the way in which the brain’s interpretation of visual signals overrides the interpretation of an auditory signal.⁠3 In documenting the effect, researchers ask subjects to watch a video of someone repeating a syllable a number of times. Here is the video: watch it once and then replay it and listen to it with your eyes closed:

Those who watch the video will report the speaker as saying: da da da da da da or even ga ga ga ga ga ga. When the video is replayed and subjects are only able to listen to the audio they clearly hear ba ba ba ba ba ba. The audio has remained unchanged, what is different is the lack of visual interference. Because the speaker’s lips are not coming together, the viewer’s brain interprets the sound being made as anything other than a /b/ sound. Once again, the brain’s expectation of the event is key in determining how that event will be perceived, whatever the objective reality is. Our cognitive paradigms—the mental patterns and expectations that our brains have—influence the interpretation of the data that our brains receive.

It is jarring to so many people to discover that our brains should interpret the physical world in such starkly different ways.  How then was any claim on objective reality ever to be trusted? If one listener can hear da da da and another ba ba ba, or if one rational person could look at a dress and see it as white and gold and another equally rational person could see it as blue and black, then how could we know at any given moment whether our eyes and ears were truly relaying objective reality? Could our senses really be unreliable?

In 2008, advocates for bicycle safety produced a video they entitled “An Awareness Test.” In the video, two teams of four—one team in white, the other in black—run around passing a basketball back and forth among teammates. The voiceover asks you, “How many passes does the team in white make?” The teams begin to run in and among one another, passing their ball to their team members wearing the same shirt. Take a look:

If you’re attentive, you’ll count 13 times that the white team passed the ball. The voiceover confirms this: “The answer is 13.” And then continues, somewhat jarringly: “But, did you see the moonwalking bear?” The what? Sure enough, the video rewinds and as you watch again, no longer focusing on the moving, weaving, ball-passing basketball players, you see a man in a bear costume walk nonchalantly to the very center of the screen and start moonwalking. The advertisement concludes with the statement: “It’s easy to miss something you’re not looking for. Look out for cyclists.”⁠4

It’s an attention getting advertisement, but at the same time, it’s jarring because when you watch the rewind of the video, you can’t believe you ever didn’t see that guy moonwalking in a ridiculous bear costume. It makes you think that perhaps Chico Marx’s question, “Who are you going to believe, me or your own eyes?” isn’t so absurd after all. Perhaps our senses aren’t as trustworthy as we like to think.

Of course, that’s nothing new. Magicians and illusionists have been utilizing these little defects in our senses for centuries, taking advantage of misdirection and what psychologists refer to as “inattentional blindness.”⁠5 Another popular internet video shows a man performing a card trick in which he asks a woman to pick a card:

At the end of the trick he reveals that the backs of all the other cards have changed color from blue to red. It seems like a nice little trick, but nothing terribly remarkable until you realize the entire video is misdirection. Because what you didn’t notice while the trick was taking place was that the color of the man’s shirt, the woman’s shirt, the background, and even the table covering all had changed over the course of the short trick.⁠6 With our attention focused on trying to keep track of the card and look for any trickery by the magician, our brains simply failed to pay attention to any other detail. When the video rewinds and shows you the trick from a wide angle, you’re astounded at how much is going on that you never even noticed the first time around.

So. Can we even trust our senses to give us accurate information about the world we live in? On balance, of course we can. Our species would hardly have survived this long were we not able to rely on the information our senses provide for us. But that does not mean that we can rely on that information with absolute certainty. Uncertainty is built into the way we perceive the world around us.


1 By “shouting,” of course, I mean TYPING IN ALL CAPS.

Guy Deutscher, Through the Language Glass : Why the World Looks Different in Other Languages. 1st ed.  New York: Metropolitan Books/Henry Holt and Co., 2010, 248.

Rosenblum, Lawrence D. “The Mcgurk Effect.”  http://www.faculty.ucr.edu/~rosenblu/VSMcGurk.html.

dothetest. “Test Your Awareness: Do the Test.”  https://www.youtube.com/watch?v=Ahg6qcgoay4.

5 Robert Alan Burton, On Being Certain : Believing You Are Right Even When You’re Not. 1st ed.  New York: St. Martin’s Press, 2008.

Wiseman, Richard. “Colour Changing Card Trick.”  https://www.youtube.com/watch?v=v3iPrBrGSJM.