After covering sensation and perception, take students back to 2015.
In case you missed it, this was the image that blew up social media in February of that year. Viewers were divided into two camps. Some saw the dress as blue/black while others saw it as gold/white. These discussions were not about whether a color was more blue or more purple. People were talking about very different perceptions. Friends and family got into arguments because each camp thought they were being gaslighted by the other. [Side note. The term gaslight, in this context, comes to us from a 1938 play which became a 1944 movie.]
What color is the real dress? Blue/black. But before the blue/black perceivers cheer for being right, the image of The Dress that falls on our retinas is more complicated than that. It turns out that both the blue/black and gold/white perceivers are right, that is, in terms of which light waves our eyes pick up. Oh. And if you perceive it as blue/brown, you’re not alone, but there aren’t that many of you.
But first, why such different perceptions? Our sensation and perception colleagues identified an assumption that our brains had to make. Some of us assumed that The Dress was lit by artificial, yellow light, the kind of light we get indoors. Others of us assumed that The Dress was lit by natural, blue light, the kind of light we get outdoors.
When we assume yellow light, our brains subtract yellow from the light wave data our eyes send to our brains. With the yellow removed, The Dress is perceived as blue/black.
When we assume blue light, our brains subtract blue from the light wave data. With blue removed, The Dress is perceived as gold/white.
Where does blue/brown come from? Those perceivers are splitting the difference. They’re subtracting a little yellow and a little blue.
ASAP Science did a nice 2-minute video on how this – color constancy – works.
A closer look at The Dress
You can show students exactly what their eyes are seeing, before the brain subtracts a color.
On your classroom computer, right-click on the photo of this dress, and select “Copy image address.” Visit the LunaPic website. In the “Open from URL” box, paste the image address. On the far left side of the page you will see a toolbar. Click anywhere over there to enter editing mode. From that toolbar, choose the eyedropper; it’s the ninth icon from the top. Click anywhere on The Dress to see the color of that spot displayed at the top of the page. Click the eyedropper again and choose another spot. When you click on a blue/white band, the color is actually a slate gray. If our brains subtract yellow, we perceive the color as bluer than it is. If our brains subtract blue, we perceive the color as whiter than it is. Use the eyedropper to sample from the black/gold bands. They are a goldish brown. If our brains subtract yellow, we perceive the color as black. If our brains subtract blue, we perceive the color as yellow-gold.
Who is more likely to perceive it one way and not another way and why?
But none of that answers the question of why some people are more likely to assume yellow light while others are more likely to assume natural light. One hypothesis is that those who spend more of their day inside under artificial lights are more likely to subtract yellow and see a blue/black dress. Those who spend more of their day outside or inside spaces with a lot of natural light – think skylights and large windows – are more likely to subtract blue and see a gold/white dress.
Survey research has found that “[o]lder people and women were more likely to report seeing ‘The Dress’ as white and gold, while younger people were more likely to say that it was black and blue” (Cell Press, 2015). Ask your students to work in pairs or small groups to generate some hypotheses as to why this is the case. Ask volunteers to report their hypotheses. For example, is it a cohort effect for age? Did older people spend more of their childhoods outdoors than today’s youth and therefore more likely to assume blue light? Teenagers are also more likely to be “owls.”
Psychological scientist Pascal Wallisch reasoned that “owls” – people who get up late and go to bed late – would experience more yellow light and, thus, would be more likely to perceive The Dress as blue/black. Conversely, he expected “larks” – people who get up early and go to bed early – would experience more blue light and, thus, would be more likely to perceive The Dress as gold/white. He found a statistically significant difference between the owls and larks in their perceptions of The Dress, but the differences weren’t huge. In other words, it appears that this is one factor, but not the only factor, that influences our assumptions about the lighting (Wallisch, 2017).
Remind students that color does not exist outside of our brains. Outside, it’s light waves. Our eyes convert those light waves into neural signals. Our brain takes those neural signals and uses them in combination with other factors, like the surrounding colors and assumptions about the environment, to create the color that we see.