Peter Reuell in PhysOrg:
What do you think of when you think of a rainbow? If you’re sighted, you’re probably imagining colors arcing through the sky just after the rain. But what about someone who can’t see a rainbow? How does a congenitally blind person’s knowledge of a rainbow—or even something as seemingly simple as the color red—differ from that of the sighted? The answer, Alfonso Caramazza said, is complicated: There are similarities but also important differences.
The Daniel and Amy Starch Professor of Psychology, Caramazza is the co-author, with postdoctoral fellow Ella Striem-Amit and Xiaoying Wang and Yanchao Bi from Beijing Normal University, of a new study that suggests that, although they experience them differently, the sighted and the blind are still able to share a common understanding of abstract visual phenomena like rainbows and color. The study is described in a December paper published in Nature Communications. “The question here is how do we represent things that don’t have an external physical reality—something we can’t touch or smell?” Caramazza said. “If you think about it, this is not just a problem for the blind; it’s a problem anyone has when they hear a word like ‘ion’ or ‘quark,’ for example. Most of us have only a very vague understanding of what those things actually are. If you talk to physicists they can give you theoretical, mathematically precise descriptions, but none of the things they associate with those things have a concrete, physical correspondence.”
With no way to directly experience what something like quarks actually are, Caramazza said, people lean heavily on language to understand or describe them—using words like “strange” and “charm” to describe quarks’ “flavors.” And the same, he said, is true for blind people seeking to understand color.
“You can use language to describe things that are physical,” he explained. “If you were blind and I wanted to describe a cup to you, I could say it’s a hard object that’s concave and it’s nonporous, so you can put liquids in it. Those descriptions are things you have some physical experience of, so you can piggyback on that experience. But there are some concepts for which you cannot do that. Color is a surface property of an object, but there’s no way for me to tell a blind person what that sensory experience is, because it’s a purely visual experience. So the way they learn about red is the way you and I learn about quarks, or about concepts like justice or virtue—through a verbal description or use in verbal contexts.”