Neuroscientists can predict what colour a person is looking at using a machine-learning tool trained on the brain activity of others

September 07, 2025 | 08:00pm

My blue is your blue: different people’s brains process colours in the same way

Neuroscientists can predict what colour a person is looking at using a machine-learning tool trained on the brain activity of others

Our brains seem to respond to specific colours in a similar way. Credit: Hispanolistic/Getty

Is the colour you see the same as what I see? It’s a question that has puzzled both philosophers and neuroscientists for decades, but has proved notoriously difficult to answer.

Now, a study that recorded patterns of brain activity in 15 participants suggests that colours are represented and processed in the same way in the brains of different people. The findings were published in the Journal of Neuroscience on 8 September¹.

“Now we know that when you see red or green or whatever colour, that it activates your brain very similarly to my brain,” says study co-author Andreas Bartels, a cognitive neuroscientist at the University of Tubingen and the Max Planck Institute, both in Tubingen, Germany. “Even at a very low level, things are represented similarly across different brains, and that is a fundamentally new discovery.”

Bartels and his colleague Michael Bannert wanted to explore how different colours are represented in parts of the brain associated with vision, and how consistent this is across different people.

The pair used functional magnetic resonance imaging (fMRI) to compare activity in the brains of a group of participants while they viewed different colours. This allowed them to create a map of brain activity that showed how each hue was represented neurologically. They then trained a machine learning model called a linear classifier on this data, and used it to predict which colours were being viewed by members of a second group of study participants, on the basis of their brain activity.