UV light might color tribes' languages

Research

December 17, 2004|By Dennis O'Brien | Dennis O'Brien,Sun Staff

Dozens of tropical cultures have no word for the color we know as blue, and two researchers say they've discovered why: The people who live in those areas can't see it.

Scientists have known for years that ultraviolet light can cloud our vision and increase the risk of eye diseases. An estimated 20 million people in the United States have cataracts.

But a psychologist at Ohio State College of Optometry says that among indigenous tribes in equatorial areas, ultraviolet light has another effect. The damage occurs early in life, goes untreated and leaves people with tinted, "yellowed" lenses that leave them unable to perceive the color blue.

That explains why so many of them have no word to describe the brilliant shade of the sky above them, she says. "To an eye damaged by sunlight, even a clear sky will not look blue," said Angela M. Brown, who developed the theory with her husband, Delwin T. Lindsey, an Ohio State psychologist.

Brown and Lindsey have examined 203 languages for their color terminology over the past 35 years, including common languages such as English, French and Spanish. They've also reviewed tongues in some of the world's most remote areas: Mixtec in Mexico, Kwerba in Indonesia and Chichewa in the Malawi region of Africa

They mapped out where the speakers lived and then used NASA satellite imagery to determine levels of ultraviolet radiation in those areas. They concluded that people whose cultures lack a word for blue are generally closer to the equator and receive the highest exposure to a type of ultraviolet light believed to accelerate aging of the eye -- known as ultraviolet B.

Ultraviolet B can damage the eye lens and retina. Whether it's damaging retinas or lenses in these areas remains an open question, Brown said. But she thinks it affects how people see color.

This is an entirely different phenomenon than colorblindness, a genetically inherited trait that usually makes it hard to distinguish reds from greens and is caused by alterations in the color-deciphering cells in the eye.

"We believe there's a physiological component to what's going on," Brown says.

She cited British researchers who found in 1997 that Africans in rural areas whose languages have no word for the color blue also are often unable to distinguish the color from greens and grays.

Many linguists and psychologists say they respect Lindsey and Brown and their methods. But most sharply disagree with their conclusions.

People adapt to the damages from ultraviolet light and continue to see blue as they age -- no matter where they live -- because the visual system compensates for the degraded signals, said Joseph Hardy, a psychologist formerly on the faculty at the University of California, Davis, Medical Center.

"That's why someone in their 70s can still tell the difference between blue and green," said Hardy, now science director of a San Francisco consulting firm.

That's true up to a point, said Brown. But in tropical areas, she argued, people are exposed to three or four times as much ultraviolet light as most Europeans and North Americans. And with their outdoor lifestyles, visual degradation occurs faster than it does in most industrial societies.

"In the tropics, you have this happening at a much younger age," Brown said. And, though children in the tropics may see blue, their languages are largely created by adults.

To test their hypothesis, the researchers asked 15 English-speaking volunteers to identify colors among 40 standardized samples displayed on a computer that simulated the effects of ultraviolet B exposure. The volunteers consistently had difficulty recognizing blue when looking through lenses with higher ultraviolet B exposure levels, they said.

The results were published in a 2002 edition of the journal Psychological Science. The researchers say they are working on a follow-up study.

Other experts argue that there are too many other factors involved in color naming -- including environmental and lifestyle differences -- to attribute the lack of a name for one color to changes in eyesight.

"It can't be as simple as this one physiological feature. Other cognitive factors can and do shape color naming, such as what's important to a culture," said Kimberly A. Jameson, a psychologist and associate project scientist at the Center for Research in Language based at the University of California, San Diego.

Dr. Francisco de Monasterio, an ophthalmologist and clinical researcher at the National Eye Institute, said that just because people haven't named a color, doesn't mean they can't see it.

"If you took all of the hues within the range of the color blue, you wouldn't be able to name each and every one of them," he said. "There's a big leap being made here between whether a language can identify a particular color that's out there and whether people can actually see it."

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