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- People’s qualia structure for color can differ a lot even when they use the same language.
- New research uses brain models to compare how different people see colors inside their heads.
- People who are colorblind arrange how they see colors with their own mental patterns. These patterns are special to them but also share some parts with others.
- Making computer brains and systems that connect to the brain could get better by copying how each person sees colors in their own way.
- Knowing what people feel inside helps us feel more for others and makes design, teaching, and tech work better for everyone.
Color seeing is something most of us don’t think much about. But if you wonder if the red you see looks like the green someone else sees, you start asking big questions about what it means to be aware, how we sense things, and what we feel inside. Scientists who study the brain are starting to show how we all see differently. They are also learning how we can map and understand these differences by looking at something called qualia structure.
The Science of Seeing Color
Seeing color starts with physics. It’s about how light hits parts of the eye. But really seeing color, feeling it, is a process in the brain and mind. When light goes into your eyes, it hits the retina. Small parts there called cone photoreceptors soak it up. There are three types of these cones. Each type reacts to a certain range of light waves. These match red (long waves), green (medium waves), and blue (short waves). This part of the eye is why most people can see three main colors.
But the retina is just the start. After light activates the cones, the signals — a mix from the different cones — travel down the optic nerve. They go to different brain areas, like the main part for seeing and a place called V4 that deals with color. What’s amazing is that the brain doesn’t just take these signals straight. It works with them based on other things. The brain thinks about the light, the surroundings, and even what color an object should be. This creates the color you finally see, which can be quite unlike the first light signal.
Our brain doing this reinterpreting is why color tricks work. It’s also why one person sees a dress as white and gold, and someone else sees it as blue and black. This shows that what we become aware of is an image the brain has worked on and understood. It’s not just like looking through a camera at the real world.
The Mystery of Qualia
“Qualia” means the feelings and senses we have inside, that are personal to us. Red isn’t only a light wave of about 700 nanometers. It’s a feeling, a sense, or sometimes even makes us feel something. In the field of studying consciousness and philosophy, qualia are the pure feelings of what things are like. Think of how coffee tastes bitter or how jealousy feels.
Color is a really good example of qualia. It’s everywhere and it’s also personal. Everyone says “red.” But what does it really feel like inside your head when you look at a red apple? Could it ever feel exactly the same as it does for someone else? Or do you and your friend use the same word but have completely different pictures in your minds? This is the main point of the old discussion in philosophy about qualia structure and if we can ever truly share or check what someone feels inside.
This is a very hard problem in studying consciousness. You cannot pass qualia from one person to another. You can try to describe them by comparing them to other things. But their main feeling cannot be fully given to someone else or looked at through another person’s view. That was true until recently.
The Inverted Spectrum Thought Experiment Revisited
Philosophers often use a thought experiment called the “inverted spectrum” to try and understand qualia. People like John Locke first suggested it, and others added to it later. This idea is about two people. They both call ripe tomatoes “red.” But maybe one person sees what the other person would call “green” inside their head. Neither person would ever find out because they use the same words and act the same way.
This brings up questions about whether what we see is fixed or changes for each person. Is red truly red for everyone if different brains organize it in different ways? Could a very smart alien or a computer program understand what red “feels” like to a person? Or does that feeling only exist inside your own head?
The inverted spectrum shows a basic difference between how we act and what we feel inside. It reminds us that we might use the same words, but our inner worlds are not always the same.
A Breakthrough Study: Mapping Personal Color Worlds
In new, important research printed in Nature Communications, Güçlü and van Gerven (2025) tested a way to compare how people see colors inside their minds. They wanted to make a factual model of something people thought was only personal.
The researchers built a computer system that acts like people’s brains processing color. They made models based on how groups of nerve cells react. These models were made to fit people who see three main colors normally, and also people who have trouble seeing colors, like red-green colorblindness.
The study looked at how people put colors into groups or saw them as different when shown different colors. This showed them a type of “map” of how colors connect. It wasn’t a map of the exact colors, but how colors relate to each other in a person’s mind. This map is called the person’s qualia structure.
“Our approach offers a novel way to perceive the similarity in color structures even among individuals with different capacities for color vision.”
— Güçlü & van Gerven, 2025
Key Findings: Unique Perceptions Anchored in Shared Structure
The main interesting point from the study was about how much people see colors differently, but also how they see some things the same way.
- People who had trouble seeing red and green colors grouped colors very differently in their brains.
- But even with these differences, there was a solid basic pattern in how the brain sorted visual information. This pattern, like a skeleton of color connections, seemed to stay the same even if what the person saw changed.
- This means the brain keeps an inner map of how colors relate. This map seems steady from one person to another, even if the light signals coming in are different.
This is a really big deal. It points to this: The feeling of red might be different for different people. But where red fits into a map of colors in the mind (like how different it is from green, or how much like orange it is) might be the same. Finding this is a big step in measuring what people feel inside.
Moving Beyond Correction: Reframing Colorblindness
For a long time, help for people who have trouble seeing colors has been about fixing it. This means using glasses, filters, or lenses to make problem colors easier to tell apart. These fixes are based on the idea that seeing three main colors normally is the best way.
But maybe the real chance is to understand things, not just fix them? Instead of asking how we can make people with colorblindness see like most people, maybe we should ask what their experience is like. And how it is different but also similar to others. The goal changes from fixing what is seen as wrong to valuing other ways of seeing.
School books, computer screens, and websites could be made in new ways. Not just so everyone can use them, but to show we value the different ways people see things.
The Emergence of a Science of Subjectivity
What’s new about this research is not just how it looks at color seeing. It’s also the method: making models of how people feel inside by looking at how things are put together. This changes brain science. Instead of only looking at what people do or what makes them act, it starts looking at how inner feelings are built. This has been a main goal in the study of the mind.
For a long time, science did not study qualia because they are hard to put into words. But now, with models like the brain and newer computer networks, we are getting close to showing the shape of things we cannot fully describe. We can do this even if we cannot touch the main feeling itself.
This is a big change in thinking. Comparing qualia structures is like making a map of the world without going to the countries. You cannot talk about the culture there. But you can write down how places connect, the paths between them, and where the borders are.
Implications for AI, Brain Interfaces, and Future Tech
Figuring out qualia structures has strong effects beyond just thinking about philosophy or simple science.
In artificial intelligence
- Computer programs trying to understand things like humans might do better if they copy how humans put together what they sense inside.
- A computer could work with an inner map instead of just naming a color. It could get close to what “redness” feels like, based on how it connects to other feelings and senses.
In brain-computer interfaces
- Knowing about qualia structures can improve ways for users to talk with computers, fitting the system to each person. This is extra helpful for people with disabilities.
- Screens or fake computer worlds that change with your brain might be set up to match how a user’s senses are mapped inside their head.
For computer brains and brain tech, making models of what sensing feels like inside — not just how much of it there is — will be a key new area for making things think like humans.
Neuroscientific Empathy: Seeing Through Someone Else’s Qualia
A useful and feeling-based good thing about knowing what people feel inside is that it helps us feel more for others.
If we all live in a slightly different reality inside our heads, seeing this can help us be kinder to each other.
For clinicians, teachers, designers, and caregivers, this understanding
- Shows that different ways of sensing things (like being sensitive to touch or sound, or having different brain setups) are real.
- Points out that trying to make everyone sense things the same way doesn’t work.
- Makes clear how important it is to try and see things from another person’s point of view based on their feelings and senses.
When we accept and respect that everyone senses things in their own way, we don’t just make room for them. We honor what they feel and sense inside.
Reality as a Shared Construct
What does all this mean for how we understand what is real?
If “green” or “red” is not a set thing, but a spot in a person’s own network of sensing, then what is real is just where our inner worlds meet. It’s like a shared picture we agree on, based on how we use words and get along with others.
Two people can stand in front of the same field. They can talk about it using similar words. But they might be feeling and sensing it in very different ways.
This brings up big questions for how we think
- Is what is real for everyone just the average of what each person feels and senses?
- Can we really compare how beauty or feelings feel to different people?
- Would creatures from another planet even see the world using colors?
This research doesn’t give final answers to these questions. But it brings us much closer to looking at them using science.
Real-World Applications and Design Considerations
For jobs and businesses like teaching, making tech, selling things, and making sure everyone can use things, knowing about qualia structure shows new good ways to do things
- Things used for teaching might need to show other ways of seeing things, especially in science and art.
- Computer screens and programs can be made with adjustable ways of showing things, so they work for different kinds of vision.
- Ways of selling things and building company looks, which now focus a lot on color plans, can get better by using design that considers everyone, based on how people see things differently.
Color seeing isn’t the same for everyone. And design shouldn’t be either.
The Road Ahead: Extending to Other Qualia
Now we can make models of how people see colors inside by looking at how it’s put together. We could use tools like this for other inner feelings and senses
- How food tastes to people who are more or less sensitive.
- The inner feelings of emotions in people with mood problems or who have gone through bad times.
- How much pain people feel, in different parts of the world or with different brain setups.
In the future, we might have “maps” of sadness, great happiness, hunger, or feeling warm. This could help us understand the mind better and lead to ways to help people or for computers to interact with them that fit each person more.
If we keep using this method, brain science could become the next big way to help us feel more for others.
Final Thoughts: A New Way of Seeing Each Other
By figuring out how brains turn light into what we see, and what we see into how we feel inside, we are opening a totally new look into the mind. This isn’t just about color — it’s about consciousness itself.
So next time you ask, “Is my red your green?” know that the answer might never be just a yes or no. But because of new steps in brain science about qualia, we are starting to see the shape of that mystery. And that work is as important as finding any final answer.
