This article originally appeared on RealSimple.com.
We know, we know: You’re tired of hearing about “the dress,” the viral photograph that dominated the Internet back in February 2015, with so many burning questions: Is it white and gold or black and blue? Is it over- or underexposed? And, seriously, why can’t we agree?
More than two years later, an NYU neuroscientist has one possible explanation for why the world was so divided on the optical illusion. And we have to admit, his new study—published today in the Journal of Vision—is pretty fascinating. It may even be worth giving the notorious mother-of-the-bride dress another 15 minutes of fame.
According to an online survey of more than 13,000 people from around the world, the colors people saw had a lot to do with whether they considered the dress to be in bright light or in a shadow. Of the survey respondents who thought it was in a shadow, four out of five saw it as white and gold. Only about half of those who did not consider the frock to be in shadow agreed.
(For the record, the dress was actually black and blue, and the colors in the photograph were overexposed and washed out.)
This explanation is nothing new; it’s been around since not long after the initial hubbub occurred: Shadows have a blue tint, so we mentally subtract blue light (seeing white as the underlying color) when we assume something is in shadow, while we mentally subtract yellow (the tint of most artificial lighting) when we assume it’s illuminated.
But Pascal Wallisch, Ph.D., a clinical assistant professor in NYU’s department of psychology, wanted to know why, exactly, people make these assumptions. So he also asked study participants other questions that might influence their thinking—their age, gender, ethnicity, and even what their daily schedules were like, for example.
“One of my focuses is on sleep research, so naturally I was wondering about light exposure,” says Wallisch. “People who get up early in the morning and those who stay up late at night are exposed to different types of light. And when a light source is unclear, you might expect these people to make different assumptions based on what they’re most used to.”
His hypothesis turned out to be right: People who said they tended to go to bed early and feel best in the morning—whom he calls morning larks—were significantly more likely to see the dress as white and gold, compared to night owls who stay up late and sleep later into the morning.
That could be because, Wallisch explains, morning people spend more of their waking hours in natural daylight and spend more time under a blue sky, whereas night owls spend more time in artificial light.
Of course, many people today—regardless of their chronotype—tend to spend most of their waking hours under artificial light in office buildings and in front of digital screens. Wallisch asked survey participants about these things, too, but saw no real patterns between their responses and their beliefs about the dress. (Nearly everyone in the study spent significant time around artificial light, he says, so it was difficult to draw solid conclusions.)
Demographic factors such as gender and age had comparatively small effects on the perception of the dress image, as well, with one exception: Around age 65, the percentage of people who saw the dress as white and gold dropped sharply. This may be because of age-related changes to the eye or the brain, the researchers speculate, or it may even be because older adults have had different life experiences—like, perhaps, spending more time outdoors in their younger years.
Wallish says that overall, his findings help broaden science’s understanding of how people perceive color, and why we don’t always see the same thing. “What I see as red and what you see as red may not be the same thing after all,” he says. “Your life history, your experience, affects how your brain factors in important things like light.”
He even goes out on a limb to say that this revelation could have societal and political implications in today’s current climate.
“Right now, most people assume if you don’t agree with them on something it’s because you’re malicious, you’re ignorant, you’re trying to mess with them,” he says. “We might need to start coming to an understanding and respect the fact that different people sincerely see the world differently—and they might not be able to change that.”