The Blue-Strawberry Problem

In his 40s, a Dutch man researchers call MAH suffered a stroke that fortunately left no lingering consequences. Still, he balked whenever doctors giving him the standard battery of cognitive tests asked about colors. It was nothing to do with the stroke, he told them. For his entire life, he had lived without a sense of color.

What did he mean? He had no problem seeing color, his doctors concluded. He easily passed the test for red-green color blindness, finding the numbers hidden in colored dots. He could put very similar hues in the right order. But he could not sort tokens into distinct colors such as red, green, blue, yellow, and orange. He could not identify the colors of the tokens. He could not imagine the color of his car. He could not even understand, when presented with a drawing of garishly blue strawberries, that the picture was odd at all.

MAH has a rare and perplexing condition called color agnosia. “It’s not a perception problem. It’s not color blindness,” says J. Peter Burbach, a neuroscientist at the University Medical Center Utrecht. What’s missing for MAH is an “understanding of color.” Color agnosia can occur after damage to visual areas in the brain, usually caused by stroke. MAH didn’t have any obvious brain damage, though, and he had been this way long before the stroke. His mother and eldest daughter, he reported, were exactly the same. Theirs is the first documented case of color agnosia that runs in a family.

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Burbach and his colleagues have spent the past several years trying to find other families with what they call developmental color agnosia—as opposed to the kind acquired via injury. It has been, he told me recently, “almost an impossible task.” (Researchers have heard of one other man with the condition, in Belgium, who didn’t want to be studied.) More people like MAH are probably out there, Burbach says, but most who have had color agnosia since birth probably don’t experience it as a problem, at least not one that requires medical attention. Only when, say, a very persistent doctor testing you after a stroke insists on asking about color over and over again might you realize that your brain is notably different.

MAH had figured out ways to compensate for his lack of color recognition. He had learned, for example, that his cellphone had a red button and a green button, which he would then compare to the red (urgent) and green (nonurgent) folders in his work email, according to Tanja C. W. Nijboer, an experimental psychologist at Utrecht University who worked with MAH. He also got very good at discriminating between different brightnesses; he tested even better, in fact, than the average person. But when faced with colors of similar brightness, he would still get confused. He would identify any light colors as yellow or pink, and dark colors as blue or red.

Color agnosia is also subtly but crucially distinct from other conditions in which people have trouble with color. It is not classic red-green color blindness, where people have faulty color-sensitive cells in their eyes. It is also not cerebral achromatopsia, a form of color blindness in which the world appears gray because an area in the brain is unable to process color, even though the eyes are working. (Oliver Sacks famously wrote about a man with this condition in “The Case of the Colorblind Painter.”) It is also not color anomia, a problem with language in which people are unable to name colors although they are able to point to one that is named by someone else. Color agnosia seems, specifically, to be a problem of connecting visual input to a concept of “red” or “green” in the brain. So people with color agnosia have no problem perceiving red and green, but “they’ve sort of lost the concept of color,” says Marlene Behrmann, a vision scientist at the University of Pittsburgh.

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Seeing a banana and saying “yellow” feels automatic and unconscious for most of us. But translating light in the eye into signals in the brain into spoken words actually takes several steps—disruptions to which can manifest as separate instances of color blindness or color agnosia or color anomia. These conditions are all unusual but also all different from one another. “Studying these rare patients really helps us tease apart how visual processing is done in the normal brain,” says Jennifer Steeves, a cognitive neuroscientist at York University, in Canada.

The Dutch researchers hope that finding other affected families will help them pinpoint a common gene in which mutations cause developmental color agnosia. Such a gene is unlikely to affect only color recognition, he says. Rather, it may influence brain development in a way that impedes the development of color recognition while having other cognitive effects, which the team is also interested in studying.

Seeing color agnosia run in families is not surprising, says Daniel Bub, a psychologist at the University of Victoria, in Canada. Prosopagnosia or face blindness—the inability to recognize faces—can be inherited. So why not color agnosia too? “They’re actually quite close in the brain, the areas responsible,” he says. And people born face-blind aren’t necessarily confused only by faces; they often have trouble recognizing objects too.

Burbach and his colleagues are still interested in finding more families affected by color agnosia. Did the strawberry at the top of this article look funny to you? If not, the team might like to hear from you.