Black and blue or white and gold? That is the question that took the world by storm back in February after two friends from Scotland posted a picture of a dress online seeking an answer because they disagreed on its color. But it seems no one else can agree either; some of us see "The Dress" as black and blue, while others see it as white and gold. Now, three new studies published in the journal Current Biology attempt to explain why.
Most of us are familiar with optical illusions. There are pictures in which two different shapes may emerge - the famous face and vase picture, for example - or ones that appear to move when you stare at them long enough.
But why has the picture of The Dress attracted so much attention?
According to Bevil Conway, of the Massachusetts Institute of Technology and Wellesley College, MA, The Dress represents the first time that a single image could be seen as completely different colors by so many different people.
"It caught fire because it was a case in which color wasn't doing what we expect," she adds.
Conway and colleagues decided to conduct a study to demonstrate just how differently we perceive the colors of "The Dress" to be.
The team surveyed 1,401 individuals, of whom 300 had never before seen the picture of The Dress. Upon being shown the picture, each participant was asked to identify the colors they saw.
From their survey, the researchers identified wide disparities in the colors reported by the participants, finding that most people fell into one of three groups that corresponded with people's color perceptions of The Dress on social media:
- 57% described The Dress as black and blue
- 30% described it as white and gold
- 11% described it as blue and brown
- 2% described it as other colors.
The team also found that people's color perceptions of the dress varied by age and gender. Women and older individuals were more likely to see the dress as white and gold, while younger people were more likely to see the dress as black and blue.
Explaining the potential reasons behind the differences in color perception, Conway says it may be down to the brain's expectations of light in a certain environment.
She notes, for example, that people who see the dress as white and gold may spend more time exposed to natural daylight, while those who see the dress as black and blue may have greater exposure to artificial light. People who perceive the dress to be brown and blue may be used to both environments.
"One framework for understanding why you get these variations is to consider how light is contaminated by outside illumination, such as a blue sky or incandescent light," Conway explains. "Your visual system has to decide whether it gets rid of shorter, bluer wavelengths of light or the longer, redder wavelengths, and that decision may change how you see 'The Dress.'"
Light blue or dark blue?
Another study conducted by Karl Gegenfurtner, of Giessen University in Germany, and colleagues took place just days after the picture of The Dress was posted on social media.
On a computer screen, 15 participants were shown the picture of The Dress to 15 on what they describe as a "well-calibrated color display under controlled lighting conditions."
The participants were also shown a disc on the same computer screen and asked to adjust its color to match that of what they perceived The Dress to be.
The team found that, rather than reporting seeing white or blue - the two colors that people say they see the most - many participants reported seeing a number of shades ranging from light blue to dark blue.
"The question should thus not be whether the dress is blue or white, but whether it is light blue or dark blue," say the researchers. "Despite the continuous choice of matching colors, observers are consistent in calling the dress 'white' when their match lies above a certain brightness and 'blue' when it lies below."
Previously, researchers have hypothesized that The Dress debate was triggered by people's interpretation of natural daylight, and Gegenfurtner and colleagues say their findings support this theory.
"It seems to be the covariation of luminance and color that is required to elicit ambiguity about the dress," they note. "The popular image of this dress has shown impressively that our perception of the world is not just a result of physical properties recorded by our senses. Rather, we make assumptions about the world that guide the interpretation of sensory data, and these assumptions can be quite different for different individuals."
Is the human eye confused by blue objects?
In a third study, Michael Webster, of the University of Nevada-Reno, and colleagues claim that The Dress debate supports increasing evidence that the human eye confuses blue objects with blue lighting.
The researchers explain that if a person stares at a gray object and the object is enhanced to become either more yellow or more blue, then they are more likely to perceive the object as yellow than blue in both conditions.
The team provides support for this theory with their research, in which they asked 87 college students what color they perceived the blue stripes of the dress to be. Around half of the participants saw the blue stripes as blue, while the other half saw the blue stripes as white.
Next, the researchers enhanced the image to make the black stripes appear blue and the blue stripes appear gold. They found that almost 95% of participants reported seeing all stripes as yellow and gold.
"The blue-yellow asymmetry has striking effects on the appearance of images when their colors are reversed," note the authors, who add that this "helps account for the variation among observers in the colors experienced in 'The Dress' image that recently consumed the Internet."
The team says the blue-yellow theory may be explained by the way the human eye has evolved through exposure to natural lighting from the sun and sky, which varies from yellow to blue.
Whatever the explanation behind our different color perceptions of The Dress, it seems that one thing is clear - we just have to agree to disagree.