Are the colors I see the same as yours? Science examines how color is perceived through the eye's photoreceptors and processed in the brain's visual cortex, while philosophy raises the limits of understanding others and the issue of subjective perception, which holds that one can never fully know another person's experience. Artificial intelligence (AI) has settled the long-running debate. The brain activity for seeing the same color was the same for everyone. The red apple I saw is also seen as red by the other person.
A research team led by Andreas Bartels, a cognitive neuroscientist at the University of Tübingen in Germany, said on the 8th (local time) in the international journal the Journal of Neuroscience that it "used AI to analyze patterns of brain activity that appear during color perception and found that colors are represented and processed in the same way in other people's brains."
◇The same process of color perception in the brain, confirmed by AI
The team sought to find out how various colors are perceived in the brain's visual cortex and whether the perceptual process is the same for everyone. For example, because people's brains differ, the pattern of neurons that respond when seeing red could be as unique as snowflakes. Or, when seeing red, anyone could show a standard and predictable pattern of brain activity.
To determine which of the two is correct, they recorded healthy people's brain activity with functional magnetic resonance imaging (fMRI). When a particular area of the brain is active, blood rushes there. fMRI shows that area as if a light has turned on. The team first showed various colors to 45 people and created a brain activity map of how they are processed in the brain. It was akin to identifying where in the brain and in what order the lights turn on when seeing red.
AI learned this data and independently grasped the brain's color perception patterns. In the same way for a second experiment, they showed specific colors to 15 people and recorded brain activity. AI could predict the color a participant was seeing just by looking at the pattern of brain activity.
The team also confirmed that different colors are processed in slightly different parts of the visual cortex, and that there are brain cells that respond more strongly to specific colors. These differences appeared consistently across participants. Michael Banner, a co-author of the paper, explained, "These results mean there are commonalities in how different people's brains interpret color."
Scientists obtained similar results in monkeys earlier this year. Bevil Conway of the National Eye Institute in the United States told the New York Times that "monkeys perceive color similarly to humans," and said, "This study implies that the ability to recognize color was strongly selected for in the course of evolution."
Of course, this study examined only people without problems in color perception. By contrast, some people might see the red apple I saw as yellow. Color is detected by cone cells in the retina that sense red, green, and blue light. If one or more of these have a problem, color vision deficiency occurs, which prevents proper color recognition.
An interesting fact is that even people with color vision deficiency will say a ripe apple is red. Everyone learns from childhood that apples are red. So even if it looks yellow to the eye, they will say the color of an apple is red. This is because of so-called memory color, which is entrenched as a stereotype in the human mind. It is like saying a banana is yellow.
◇The dress color debate that split the world 10 years ago
Even without color vision deficiency, people do not always see colors the same way. A decade ago, the world split into two over a photo of a dress posted online by a British singer. One side said it was "a white dress with gold stripes," while the other saw "a blue background with black stripes." This is the so-called "white-gold" versus "blue-black" controversy.
At the time, Bevil Conway of the Massachusetts Institute of Technology (MIT) published in the international journal Current Biology that the brain perceived different colors because it assumed different locations where the dress was seen. Gender bias—men and women seeing different colors—was explained in the same vein.
An analysis of the photo's pixels found that the dress was actually blue with brown stripes. In a survey of 1,401 people, 57% said they saw the dress photo as blue-black. Thirty percent said white-gold, and 11% said blue with brown stripes.
Conway explained that this was "the result of the brain performing color correction that discounts the effects of illumination." According to the team, people who saw white-gold assumed the dress was viewed outdoors in daylight. Daylight at noon has many short wavelengths in the blue range. If you subtract blue from the original "blue-brown," it becomes white-gold.
By the same principle, the blue-black side assumed the dress was seen indoors. If you subtract the long-wavelength red light abundant in indoor lighting from "blue-brown," it becomes blue-black. Those who saw the original colors assumed lighting between indoor lights and daylight.
In the survey, younger and male respondents were more likely to answer blue-black. Women and older people more often answered white-gold. The team explained, "Young men spend more time active at night than women or older people and are more accustomed to indoor lighting," and "when they look at the dress, they naturally assume indoor lighting and discount red."
References
Journal of Neuroscience (2025), DOI: https://doi.org/10.1523/JNEUROSCI.2717-20.2025
Journal of Neuroscience (2025), DOI: https://doi.org/10.1523/JNEUROSCI.1673-23.2024
Current Biology (2015). DOI: https://doi.org/10.1016/j.cub.2015.04.053