A Rose by Any Other Name Would Look as Red

Every person is different. Take my neighbor, for example. He has amazingly selective hearing. When his two dogs start to bark madly at 2 a.m, he is undisturbed, whereas I fall out of bed thinking that the Death-Eaters are attacking my house. Maybe his eyesight is different too. That would explain why he waters his lawn every single day, even though it looks pretty green to me. Which makes me wonder: Does he see colors differently than I do? Could our eyes be telling us different stories? 

In this lawn-watering example, the answer seems to be no. Barring color blindness, no matter how different our individual eyes may be, our brains ensure that we experience colors in the same way, according to a group of ground-breaking studies in the past decade. But those rules can change when we start mucking with vision – through colored contact lenses or even changing latitudes. But seeing as my neighbor hasn’t been on any far-fetched vacations nor does he have a fondness for red sunglasses, I can only assume that he just likes wasting water.

Human-grade color vision is a relatively recent trait, likely first appearing in the Old World monkeys. We manage our three-color vision through the use of light-sensitive cone cells in our retinas. Owing to the pigments they contain, the three types of cones – long (L), medium (M) and short (S) – detect red, green and blue wavelengths of light, respectively. If the proportions of each cone type differed among people’s retinas, they might see colors differently. Unfortunately the pigments are fragile and quickly bleach away with light from normal microscopes, so direct measurements of the distribution of each cone type are difficult.

However in 1999, Austin Roorda from the University of California, Berkeley, and David Williams from the University of Rochester used a technology called adaptive optics to directly examine the retinas of two men. (Adaptive optics was first used in telescopes to correct for the atmospheric blurring of starlight.) The pair found that although the number of S-cones was more or less constant, the ratio of L-cones to M-cones varied remarkably – by almost a factor of four. Given these results, one might expect that the man with more L-cones, which detect reds, should see the world in a more reddish light. But, as it turns out, he didn’t.

Roorda, Williams and colleagues devised a simple experiment to prove that the discrepancy in L- to M-ratios did not affect color perception. They asked the same two subjects to pick out a “unique yellow” (a yellow which looks neither greenish nor reddish). Both picked more or less the same wavelength. This finding, according to Williams, could mean only one thing: the brain had put in place a sort of auto-calibration system which somehow balanced the colors the subjects’ eyes “saw.”

Buoyed by their results, collaborator Yasuki Yamauchi from the Medical College of Wisconsin prepared another experiment. He wanted to find out how the subjects settled on practically the same wavelength of yellow. The research team started off with 32 participants and measured their L:M cone-cell ratios, which varied by a staggering 25-fold. But again, all picked about the same wavelength of unique yellow.

Next, four subjects spent two weeks wearing color-tinted contact lenses, donning tinted goggles or sitting in rooms with green or red light for 4, 8 or 12 hours a day. As the days went on, the participants’ unique yellows started to change; those in the red-hued world saw everything a bit greener and vice versa.  It took a couple of weeks for the full effects to kick in, and the effect seemed to last about a week. The authors concluded that color perception is defined by what scientists call the “average illuminant” but what we’d call the color of the background light (which is actually the same as our unique yellow). It’s a handy trick for the socially minded human, making sure everyone sees the same ripe orange fruit or red stoplight.

Which means that if I locked my neighbor up in a wee red-tinted room for two weeks then his lawn would start to appear more green and verdant and maybe he would stop watering already.

Then again, I could just send him to a different country. Some studies suggest that cultural differences in the language of color may be rooted in real differences in color perception. Debi Roberson of the University of Essex studies the way the Namibian Himba tribe classifies color.  The Himba are solitary hunters who live in African deserts, resplendent in bright yellow and red light. For the purposes of this article, that’s sort of like a desert-tinted contact lens. The Himbas have several words for the various shades of reds, yellows and oranges, while the colder colors are more or less grouped around one name. For example, both blue and green are classified under one word, “burou.” Roberson suggested that these language differences reflect a real shift in the way the Himba see color compared to how, say, a Norwegian might.

In the end, my options come down to the following: force my neighbor to wear some red-tinted sunglasses while he waters the lawn, sequester him in a red room, or banish him to some ruddy locale. Maybe it would be easier to just hide the hose. And kidnap the dogs.