Do People See the Same Colours, or Is My "Blue" Your "Green"?
The question of whether we all perceive colours in the same way has fascinated scientists, philosophers, and psychologists for centuries. When you look at the sky and call it "blue," how can you be certain that someone else isn't seeing what you would describe as "green" but still calling it "blue" due to shared language conventions? This article explores the science behind colour perception, individual differences in visual processing, and the role of language in shaping how we experience colours.
The Science of Colour Perception
Colour perception begins in the retina, where specialized cells called cone photoreceptors detect different wavelengths of light. Humans typically have three types of cone cells, each sensitive to different ranges of wavelengths:
Short-wavelength cones (S-cones): Peak sensitivity to blue light (~420 nm)
Medium-wavelength cones (M-cones): Peak sensitivity to green light (~530 nm)
Long-wavelength cones (L-cones): Peak sensitivity to red light (~560 nm)
These cones send signals to the brain via the optic nerve, and the visual cortex processes these signals to produce our experience of colour. However, just because the physiological mechanism is similar for most people doesn’t mean our subjective experience of colour is identical.
Variability in Colour Perception
Several factors influence how individuals perceive colour, making it possible that my "blue" is indeed different from your "blue."
1. Genetic Differences in Cone Cells
Genetic variations influence how cones respond to light. A well-documented example is colour blindness (or colour vision deficiency), where individuals may lack one type of cone or have cones that respond abnormally to certain wavelengths. For example:
Protanomaly (red-weak) and Deuteranomaly (green-weak) shift how red and green hues are perceived.
Tritanomaly (blue-weak) affects blue and yellow perception, though it's much rarer.
Even in individuals with normal colour vision, slight genetic variations in cone function can lead to subtle differences in how colours appear.
2. The Role of the Brain
Even if two people have identical cones, their brains may process colour information differently. Studies suggest that perception is shaped by previous experiences and neural activity patterns, meaning colour experience can vary subtly between individuals.
For example, synesthesia is a condition in which some people experience cross-wiring of senses, leading to unique colour perceptions for certain numbers, words, or even emotions.
3. Language Shapes Colour Perception
Our language influences how we categorize and perceive colours. In some languages, there are fewer words for colours, leading to different ways of grouping them. For instance:
The Himba tribe of Namibia has multiple words for different shades of green but lacks a distinct word for blue, making it harder for them to distinguish blue from green in psychological tests.
The Russian language distinguishes between light blue (голубой) and dark blue (синий), affecting how Russian speakers perceive the colour spectrum.
These linguistic differences suggest that colour perception is not purely biological but also shaped by cognitive and cultural factors.
Experimental Evidence
Several studies provide evidence that colour perception is subjective and variable:
"The Dress" Phenomenon (2015): A viral image of a dress divided people into two camps—those who saw it as blue and black and those who saw it as white and gold. This was due to differences in colour constancy—how the brain adjusts for lighting conditions.
Land’s Retinex Theory (1977): This theory suggests that the brain doesn’t just process raw wavelength data but actively interprets colours based on the surrounding context.
Colour Adaptation Experiments: When people are exposed to a colour for a long time (e.g., red), they may perceive a different colour (e.g., cyan) afterward due to neural adaptation, showing how colour perception is dynamic.
Could My "Blue" Be Your "Green"?
Although we share a common biological basis for colour vision, our subjective experiences of colour may differ due to genetic, neurological, and linguistic influences. While we use the same labels (e.g., "blue"), it’s impossible to verify whether two individuals experience colour in an identical way.
If you were to swap brains with someone else for a day, you might find that their perception of colour differs significantly from yours—even if you'd never known it before.
Simply Put
Colour perception is not just a matter of light hitting the retina; it's a complex interaction between biology, cognition, and culture. While the exact subjective experience of colour may remain unknowable, research suggests that variations in perception are real and measurable.
Whether or not my "blue" is your "green," one thing is certain—colour is far more than just a physical property of light. It is a uniquely human experience, shaped by our minds and the world around us.
