When Paul Kay, then an anthropology graduate student at Harvard University, arrived in Tahiti in 1959 to study island life, he expected to have a hard time learning the local words for colors. His field had long espoused a theory called linguistic relativity, which held that language shapes perception. Color was the “parade example,” Kay says. His professors and textbooks taught that people could only recognize a color as categorically distinct from others if they had a word for it. If you knew only three color words, a rainbow would have only three stripes. Blue wouldn’t stand out as blue if you couldn’t name it.

What’s more, according to the relativist view, color categories were arbitrary. The spectrum of color has no intrinsic organization. Scientists had no reason to suspect that cultures divvied it up in similar ways. To an English speaker like Kay, the category “red” might include shades ranging from deep wine to light ruby. But to Tahitians, maybe “red” also included shades that Kay would call “orange” or “purple.” Or maybe Tahitians chunked colors not by a combination of hue, lightness and saturation, as Americans do, but by material qualities, like texture or sheen.

To his surprise, however, Kay found it easy to understand colors in Tahitian. The language had fewer color terms than English. For example, only one word, ninamu, translated to both green and blue (now known as grue). But most Tahitian colors mapped astonishingly well to categories that Kay already knew intuitively, including white, black, red, and yellow. It was strange, he thought, that the groupings weren’t more random.

Almost all of the languages they examined appeared to have color words that drew from the same 11 basic categories.

A few years later, back in Boston, he was shooting the breeze with a fellow anthropologist, Brent Berlin, who had worked as a graduate student among speakers of the Mayan language Tzeltal, in Chiapas, Mexico. There, Berlin told Kay, he had encountered exactly the same color categories that Kay had observed in Tahiti, including a single word for grue. “The two languages are as unrelated to each other historically as any two languages can be,” Kay says. And yet they seemed to give rise to a common way of seeing and thinking about color. Either he and Berlin had stumbled upon a one-in-a-million coincidence. Or the relativists were wrong.

To solve the puzzle, the young scientists needed more data. In the mid-1960s, they were both hired as professors at the University of California, Berkeley, and with their students’ help, they rounded up native speakers of 20 languages, including Arabic, Hungarian, and Swahili. The researchers showed each speaker 329 standard color chips and asked him or her to name each one’s “basic color term”—the simplest, broadest word that described its shade. Drawing from previous anthropological work, they added color lexicons from 78 additional languages around the world.

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The results revealed two remarkable patterns, which Kay and Berlin laid out in their 1969 monograph, Basic Color Terms. First, almost all of the languages they examined appeared to have color words that drew from the same 11 basic categories: white, black, red, green, yellow, blue, brown, purple, pink, orange, and gray. Second, cultures seemed to build up their color vocabularies in a predictable way. Languages with only two color categories chunked the spectrum into blacks and whites. Languages with three categories also had a word for red. Green or yellow came next. Then blue. Then brown. And so on.

Kay and Berlin took these commonalities as evidence that our conception of colors is rooted, not in language, but in our shared human biology. Other experts were skeptical, questioning the researchers’ methods or accusing them of harboring an Anglocentric bias, in which 11-color languages like English sat atop the evolutionary color tree. The debate triggered a flood of new research. Over the next half-century, scientists sought to explain Kay and Berlin’s theories or debunk them once and for all. They journeyed to remote tribes, wrangled pre-linguistic babies, and peered into the brains of humans and animals, all in a quest to answer one of the most basic—and most profound—questions about human consciousness: Did color spring from our heads or our tongues? Or from somewhere in between?

Gilbert, A.L., Reiger, T., Kay, P., & Ivry, R.B. Whorf hypothesis is supported in the right visual field but not the left. Proceedings of the National Academy of Sciences 103, 489–494 (2006).





One of the first people to suspect a biological basis for color terms was William Gladstone, a British classicist and four-time Prime Minister in the 1800s. He noticed that the ancient Greek poet Homer used colors in a very strange way (for instance: “wine-dark sea”) and found that in all of The Illiad and The Odyssey, there are no explicit words for several colors, including blue and green. Gladstone concluded that the Greeks must have had poor color vision.

More than half a century later, linguistic relativity offered another interpretation: Homer saw the sea as “wine-dark” not because his vision was underdeveloped but because he didn’t have the words to comprehend it as anything else. “The world is presented in a kaleidoscopic flux of impressions which has to be organized by our minds—and this means largely by the linguistic systems in our minds,” wrote Benjamin Lee Whorf, an American linguist who championed this idea in the mid-1900s.

In the 1950s, the first generation of cognitive psychologists set out to test Whorf’s hypothesis. And they found some compelling evidence. In memory tasks, for example, Native American Zuni speakers, who use only one word for both orange and yellow, confused color chips from these two foreign categories more often than English speakers, suggesting that language indeed influences thought.1

More than a decade later, however, Kay and Berlin’s revelations got some scientists wondering if color categories could be anchored in something more innate. The wellspring, they suspected, lay deep inside the human brain. But where?

Many color categories were consistent across cultures, suggesting a strong biological link.

Our color vision system, it turns out, is terrifically complex. When light hits the human retina, it activates three classes of photoreceptor cells, called cones. Although all cones can respond to all wavelengths in the visible spectrum, each type is most sensitive to one particular slice: blue, yellow, or yellow-green. The relatively small differences between these peaks allow the brain to do some pretty sophisticated calculations, which determine the colors of the objects we look at.

This code remains something of a mystery, but neuroscientists are beginning to crack it. There is some evidence, for example, that in the visual cortex, an information processing center near the back of the skull, the brain adjusts signals relayed from the cones to account for variations in ambient light, making a banana appear yellow or an apple red whether it’s hanging in broad daylight or perched atop a dimly lit counter.

Our ability to discriminate between “banana yellow” or “apple red,” however, may arise near the bottom of the brain, in the inferior temporal cortex, a region responsible for high-level visual tasks such as recognizing faces, says Bevil Conway, a color expert at Wellesley College and the Massachusetts Institute of Technology. In macaque monkeys (whose retinas are similar to our own), he recently found tiny islands of cells in this region that seem to be tuned to specific hues, providing a sort of spatial map of the color spectrum.2 The neural networks that file colors into groups, meanwhile, seem to reside in yet another brain area, and only in humans.3,4

That we have separate hardware for differentiating colors and organizing them is telling, says Jules Davidoff, a psychologist at Goldsmiths University of London. It may explain, for example, why two English speakers can look at the same shade of maroon, and while they can both distinguish it from nearby shades, disagree on its basic color term. One person may label it red; the other brown, or purple. In fact, as Davidoff and others came to find, color categories show far more variability than Kay and Berlin’s original study picked up.

Courtesy of Sussex Baby Lab





After the publication of Basic Color Terms, critics chided Kay and Berlin for drawing sweeping conclusions from a survey of only 20 languages, many of which, such as English and Arabic, were likely influenced by global industry. So when William Merrifield, a Christian linguist working in Bible translation, offered to have missionaries around the world conduct color surveys at remote field sites, Kay and Berlin jumped at the chance. The resulting database, completed in the early 1980s and dubbed the World Color Survey, comprised basic color terms for 110 languages, all from nonindustrial societies.

In a broad sense, the World Color Survey upheld Kay and Berlin’s original assertions: Many color categories were consistent across cultures and often arose in language in similar ways, suggesting a strong biological link. But the data also revealed a surprising amount of diversity. For example, the Brazilian language Karajá, which has four basic color terms, lumps yellow, green, and blue into one category.5 Linguists point to similar divergences among other languages. Russian and modern Greek, for example, have separate terms for light blues and dark blues, giving each language a total of twelve basic colors. Korean, meanwhile, separates yeondu (yellow-green) from chorok (green), drawing a boundary between these two categories that no other language does.

Sometime between infancy and adulthood, for mysterious reasons, color categories may pack up and move hemispheres.

What could account for these differences? In the early 2000s, Davidoff and his colleagues compared color perceptions of English speakers with those of Berinmo speakers, in New Guinea, and Himba speakers, in Namibia—two groups with only five basic color terms, including one for grue.6,7 In one experiment, the researchers showed each subject a color swatch and then presented it next to a second swatch of a slightly different shade. If the first swatch was green, English speakers could easily pick out the second swatch if its color crossed over into the English category blue. But Berinmo and Himba speakers had more trouble with this task. Although they could distinguish the individual shades just as well as anyone else, Davidoff explains, they judged the two swatches as more similar because they had the same name. Other studies showed that Russian speakers similarly notice differences between their two blues more easily than English speakers,8 while Koreans had a keener eye for differences between their yellow-greens and greens.9

These findings seemed to support the relativist view: Words interfere with perception, making colors appear more similar or more different than they actually are. At the same time, researchers were also gathering evidence that our ability to categorize colors may exist as early as infancy, before we learn language. Anna Franklin, a cognitive psychologist at the University of Sussex, and her colleagues recently demonstrated that pre-linguistic human babies perceive some of the same color boundaries as English-speaking adults. When the researchers showed infants a series of colored swatches, they found that the babies tended to stare longer at colors that came from categories they hadn’t seen before. If a baby first saw a lime green swatch, for example, he or she would likely pay more attention to the next swatch if it were sea blue than if it were forest green. A lingering gaze implied that the baby recognized a color as new, and therefore more interesting to look at. Although babies can tell the difference between two different greens, Franklin explains, “in their memory, they’ll classify them as if they’re the same kind of perceptual experience,” making the color change seem less novel.

It’s unclear, though, why our infant brains chunk colors at all. In a 2011 study, a team led by researchers at Mount Sinai School of Medicine, in New York, found a mathematical formula that describes how inputs from the retina could result in the separation of colors into warm (white) and cool (black) tones, suggesting that the physical properties of our vision system may create natural “fault lines” in color space.10 Other researchers speculate that colors in our environments may cluster around certain shades, such as the bright red of blood and berries, or the solid green of fields and foliage. As babies, we may be primed to pick up on these statistical regularities.





Many experts expect that science will eventually reconcile the relativist and universalist philosophies. “As is probably the case with all nature-nurture debates, it ends up being a bit of both,” Franklin says. In a 2008 study, she and her colleagues found that infants were quicker to recognize a color from a new category if it appeared in their left visual field, which sends inputs to the right hemisphere of the brain. Adults, on the other hand, were quicker to recognize a new color category if it appeared in their right visual field, which corresponds to the left hemisphere, where the language centers reside.11 The results hint at a tantalizing possibility: “As you learn the words for color, as your categories become more linguistic, they become more left-hemisphere dominant,” Franklin says. Sometime between infancy and adulthood, for mysterious reasons, color categories may pack up and move hemispheres.

This hypothesis may help resolve the old debate that Kay and Berlin kindled. But it also raises new questions: Do the color categories we perceive as infants lay the groundwork for those we perceive as adults, thereby creating commonalities that get tweaked and refined by language? Or does language commandeer color categorization during our childhoods, imposing its own order on our perceptual worlds?

The answer may explain not only the perplexities of color but why we parcel the world in the ways that we do—why we create races and castes and genders and sexual orientations; why the Himba have only five basic color terms but many words for the various hide patterns of their livestock. Color is a “testing ground” for the human experience, Franklin says. It is much more than just the bands of a rainbow.





Chelsea Wald writes about science and the environment in Vienna, Austria. Follow her on Twitter @chelseawald.





References

1. Lenneberg, E. & Roberts, J. The denotata of language terms. Paper presented at the Linguistic Society of America, Bloomington, IN (1953).

2. Conway, B.R. & Tsao, D.Y. Color-tuned neurons are spatially clustered according to color preference within alert macaque posterior inferior temporal cortex. Proceedings of the National Academy of Sciences 106, 18034-18039 (2009).

3. Brouwer, G.J. & Heeger, D.J. Categorical clustering of the neural representation of color. The Journal of Neuroscience 33, 15454-15465 (2013).

4. Bird, C.M., Berens, S.C., Horner, A.J., & Franklin, A. Categorical encoding of color in the brain. Proceedings of the National Academy of Sciences 111, 4590-4595 (2014).

5. Kay, P. & Maffi, L. Color appearance and the emergence and evolution of basic color lexicons. American Anthropologist 101, 743-760 (1999).

6. Roberson, D., Davies, I., & Davidoff, J. Color categories are not universal: Replications and new evidence from a Stone-age culture. Journal of Experimental Psychology: General 129, 369–398 (2000).

7. Roberson, D., Davidoff, J.B., Davies, I.R.L., & Shapiro, L.R. Color categories: Evidence for the cultural relativity hypothesis. Cognitive Psychology 50, 378-411 (2005).

8. Winawer, J., et al. Russian blues reveal effects of language on color discrimination. Proceedings of the National Academy of Sciences 104, 7780-7785 (2007).

9. Roberson, D., Pak, H., & Hanley, J.R. Categorical perception of colour in the left and right visual field is verbally mediated: Evidence from Korean. Cognition 107, 752-762 (2008).

10. Xiao, Y., Kavanau, C., Bertin, L., & Kaplan, E. The biological basis of a universal constraint on color naming: Cone contrasts and the two-way categorization of colors. PLoS One (2011). Retrieved from DOI: 10.1371/journal.pone.0024994

11. Franklin, A., et al. Categorical perception of color is lateralized to the right hemisphere in infants, but to the left hemisphere in adults. Proceedings of the National Academy of Sciences 105, 3221-3225 (2008).





This article was originally published in our “Color” issue in July, 2015.