While writing this article, I am lying in the grass, which is as green as the caipirinha I am drinking under the blue sky. This sounds great, doesn’t it? I’m guessing you just imagined the scene. But to be honest: I am just sitting on my desk – without any caipirinha but at least with a brown coffee. Anyways, using these colorful descriptions I was able to somehow draw an image of the scene in your head, right?
Colors have a very strong meaning for all living beings. We humans use different colors as attributes to describe things more vividly, and more importantly, we have emotional connections to them. So we seem to agree on the definition of colors as we would describe objects of similar color the same way. Blue is rather calm whereas red is energetic and impulsive. But there is a chance that we perceive colors totally different: my green could be your red. It sounds like a philosophical question at first, however, it is a neuroscientific question at its core.
“[…] color has an objective, external component, namely the wavelength, and a subjective, internal component – the perception in the brain, which is still a mystery to researchers.”
To stay in a scientific point of view: what if I tell you that the green grass is not really green but contains chlorophyll as a pigment, which reflects a part of the light with a specific wavelength to activate light-sensitive cells (photoreceptors) in your eye. As long as there is no color blindness, we all have the same three color receptors, named S-, M- and L-cones, being sensitive to short, medium, and long wavelengths of light, respectively. What we describe as green is just a part of the light spectrum with a wavelength of about 540 nm, activating mainly M-cones in the retina. However, the further processing and final perception of green is happening in the visual cortex, in the brain. Thus, color has an objective, external component, namely the wavelength, and a subjective, internal component – the perception in the brain, which is still a mystery to researchers.
“[…] colors that we would describe as more similar actually have a more similar pattern of activity in the brain.”
But is it really so mysterious? Can we measure if we perceive colors in a similar or a totally different way? A recent study by Rosenthal et al. just showed that different colors elicit a different spatial pattern of neural response, suggesting a topographic representation of colors in the brain. In this experiment, the brain activity of subjects was measured by magnetoencephalography, which is using magnetic sensors to detect the electrical activity of neurons. During this measurement, subjects were shown cards with a spiral of different colors and had to name the color that they saw. For such a classical decoding experiment, tons of data are produced, which are needed to identify patterns of neural activity. Thus, one can see if a specific pattern of activity correlates with the subject perceiving a specific color. And indeed, the study showed that our brain encodes colors with a specific spatial pattern of activity. But all the more impressive, the activity pattern was more similar for colors of the same hue but different luminance (e.g. dark blue and light blue), than for different hues (e.g. blue and green). Thus, colors that we would describe as more similar actually have a more similar pattern of activity in the brain. This is further proven by the fact that the activity patterns between light and dark blue were also more similar than between light and dark yellow. The researchers suspect that language plays a major role here: participants more often chose a different term for the different shades of yellow, e.g. “brown” for dark yellow, whereas light and dark blue were consistently described by the term “blue”.
Language seems to shape our perception. But does that mean that our native language influences our color perception? Do Russians see the blue sky in a different color than English people do? Well, they do not really see it in a totally different color, but at least they have a faster recognition of different shades of blue. The Russian language describes light and dark blue with two different categorical terms, namely “goluboy” for light and “siniy” for dark blue. This difference in the semantic categories leads to a better recognition of various shades of blue for a Russian speaker in comparison to an English speaker.
Another intriguing study proves that categorical color terms influence our color perception primarily in the left hemisphere of the brain. The visual fields project contralaterally to the brain. This means the right visual field is processed in the left hemisphere, whereas the left visual field is processed in the right hemisphere. However, the left hemisphere is dominant for language tasks, which causes the visual processing of the right visual field to pass through a kind of linguistic filter. Participants of this study had to look at a central fixation cross with a ring of colored squares arrayed around it. All squares had the same color, except one target square which appeared at the right or left half of the display. The task was to identify whether the target square appears on the right or left half by pressing a button with the corresponding hand. If the color of the target square has a different categorical color term (e.g. all squares are green and the target square is blue), the target square is identified much faster than if the target color has the same categorical color term (e.g. the target square is just a different shade of green). The faster discrimination between green and blue is not surprising, but the exciting fact is that this faster color discrimination only applies to the right visual field, which is processed by the left language-dominant hemisphere. Interestingly, this linguistic filter can be switched off. If the participants were given a concurrent task requiring verbal resources, the effect of faster color discrimination of the right visual field disappeared.
“Perhaps our color perception would not be influenced so much by our language, if we humans had decided to designate colors according to their wavelengths instead of categorical color terms.”
All these experiments demonstrate once again how fascinating our brain is. Although language is affecting color recognition, the question of whether we perceive colors differently is still not resolved. Having a spatial patterning of neural activity for different colors in our brain is definitely a huge finding. Nevertheless, from this finding we cannot tell if we perceive colors in the same way.
To put it simply, humans have merely agreed to define a particular receptor activation pattern in the retina with a categorical term, e.g. green. Perhaps our color perception would not be influenced so much by our language, if we humans had decided to designate colors according to their wavelengths instead of categorical color terms. Instead of green grass and a blue sky, there would be grass of wavelength 540 nm and a sky of 450 nm. But isn’t it a wonderful idea that we somehow see the world through our very own filter? Our brains, and therefore, our thoughts and perception, are shaped by our environment and our experience. This makes color perception an incredibly exciting but also individual topic, as each of us has their very own perception of the world. So, let’s drink a green caipirinha (or you might prefer now the description of a caipirinha of 540 nm) to that. Cheers on our brains, those colorful minds!
Written by Carolin Fischer. Illustrated by Lisa Vial.
Edited by Desislava Nesheva and Sean Noah.
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Conway, B. R., Chatterjee, S., Field, G. D., Horwitz, G. D., Johnson, E. N., Koida, K., & Mancuso, K. (2010). Advances in color science: From retina to behavior. Journal of Neuroscience, 30(45), 14955–14963. https://doi.org/10.1523/JNEUROSCI.4348-10.2010
Gilbert, A. L., Regier, T., Kay, P., & Ivry, R. B. (2006). Whorf hypothesis is supported in the right visual field but not the left. Proceedings of the National Academy of Sciences of the United States of America, 103(2), 489–494. https://doi.org/10.1073/pnas.0509868103
Regier, T., & Kay, P. (2009). Language, thought, and color: Whorf was half right. Trends in Cognitive Sciences, 13(10), 439–446. https://doi.org/10.1016/j.tics.2009.07.001
Rosenthal, I. A., Singh, S. R., Hermann, K. L., Pantazis, D., & Conway, B. R. (2021). Color Space Geometry Uncovered with Magnetoencephalography. Current Biology, 31(3), 515-526.e5. https://doi.org/10.1016/j.cub.2020.10.062
Winawer, J., Witthoft, N., Frank, M. C., Wu, L., Wade, A. R., & Boroditsky, L. (2007). Russian blues reveal effects of language on color discrimination. Proceedings of the National Academy of Sciences of the United States of America, 104(19), 7780–7785. https://doi.org/10.1073/pnas.0701644104