After decades of brain research, scientists still aren’t sure whether most people see the same way, more or less — especially with colors.
Is what I call red also red for you? Or could my red be your blue? Or maybe neon pink? If it were possible to project what I see directly into your mind, would the view be the same, or would it instead resemble a crazy-hued Andy Warhol painting?
“That’s an age-old question, isn’t it?” said Andreas Bartels, a professor of visual neuroscience at the University of Tübingen in Germany.
But scientists do have a good understanding of which parts of the brain handle vision. They have even figured out where various vision-processing tasks are performed, like recognizing what is moving, identifying colors and adjusting to different lighting conditions.
Amazingly, it is even possible to deduce what you’re seeing by looking at an M.R.I. scan showing which parts of your brain are lighting up.
“That comes out of the world of science fiction, or one would think, right?” Dr. Bartels said. “It’s amazing that this is possible, but this always has happened in individual brains.”
That is, researchers pulled off this sleight of science with individuals. They would first show a subject lying in the M.R.I. machine a series of images, mapping out how that person’s brain responded. After that initial training, the researchers could randomly show one of the images and, based on just the brain activity, make a good guess at what the image was.
In new research, Dr. Bartels and Michael Bannert, a postdoctoral researcher in Dr. Bartels’ laboratory, used that technique to provide a partial answer to the question of whether most of us have a shared sense of colors. They put 15 people, all with standard color vision, in an M.R.I. machine. The volunteers viewed expanding concentric rings that were red, green or yellow.
They used data from 45 subjects to calculate an average color-induced response in different parts of the brain. This average brain response was then used to reliably predict the color and brightness of what the 15th person was looking at.
The data suggests that if I were looking at something red, and the nerve signals from my optic nerves were diverted to your brain, you would probably say the color was recognizably red. (Unless you are colorblind and see red as a dark green.)
Your perception of red could still be different from mine. No scientific tool “can address the question of how similar a subjective experience really is,” Dr. Bartels said.
“But I think we can inch closer to answering that through scientific methods,” he added. “And this approach was one where we tried to figure out if and how the red in your brain resembles maybe the red in other people’s brains.”
The researchers reported their findings in a paper published Monday in The Journal of Neuroscience.
”The Bartels paper is super cool,” said Bevil Conway, a researcher at the National Eye Institute who was not involved with the research. The findings indicate that color experience is very similar for different people, at least for those with normal color vision.
“Interestingly, very similar results have just been obtained in macaque monkeys,” Dr. Conway said, and that suggests that monkeys also perceive color similarly.
“The work has broad implications, suggesting that evolutionary selective pressures very strongly favor high-fidelity color perception,” he said. “Which is just a fancy way of saying that from an evolutionary point of view, color is really important.”
And yet people definitely do not always see color the same way.
Remember “The Dress?”
A decade ago, millions of people around the world experienced the vagaries of human vision when looking at a photograph of a dress.
The neurons in everyone’s retinas would have sent roughly similar visual signals of the photograph to the brain, but people’s brains interpreted the signals very differently.
Some people saw a blue and black dress. But others, with equal certainty, saw gold and white. And for the truly befuddled, the color of the dress switched back and forth, sometimes blue and black, sometimes gold and white.
“Colors are not just a physical property,” Dr. Bartels said. “Color perception always includes a calculation by the brain about the illumination.”
At sunset, a white piece of paper looks reddish. On a rainy day, the same sheet looks more bluish-gray. “But every time, you see the white piece of paper is white, right?” Dr. Bartels said.
With the dress, the brain’s color correction algorithm broke.
The dress went viral because it was a rare instance of people disagreeing over colors, Dr. Conway said.
“If people disagreed about colors regularly, social knowledge of colors would register the disagreement,” he added.
Kenneth Chang, a science reporter at The Times, covers NASA and the solar system, and research closer to Earth.
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