Sight for the Blind: The Growing Success of Seeing with Sound


Traditional German bureaucrats have a hard time figuring out how to deal with blind people who venture off into the wildnerness by themselves. They can easily dismiss people like Daniel Kish -- with his "Batman" nickname and "No limits" motto -- as a wonder boy, a strange talent bordering on the supernatural. In Germany, there has long been a friendly disinterest in flash sonar. It's a useful skill if someone can master it, they say, but what good is it to the average blind person?

Take the example of Reiner Delgado, a social worker at the German federation for the blind and visually impaired. Delgado also uses a type of spatial hearing. When he plays blind soccer, he can detect the wall surrounding the pitch from 20 meters away. When he leaves home, he snaps his fingers every so often to determine the position of the surrounding high-rises. Even so, before embracing the type of flash sonar that Kish champions, Delgado wants more proof. "We need a proper study with a larger number of test subjects," he says. "Then we'll be able to see whether everyone can really learn it."

Clicking Unpopular with Students

Still, numerous attempts have already shown that even blindfolded people without visual impediments can learn to detect objects in their surroundings after just a short period of time. In fact, lacking any instructions, some blind people have simply taught themselves the technique. Dave Janischak, a 15-year-old high school student in the western German city of Marburg, stumbled upon a type of flash sonar when he was four. At the time, he attended a day care center with a mentally disabled boy who spent the whole day clicking his tongue. In what began as childish teasing, Janischak mimicked the boy's clicking. But he quickly discovered that doing so helped him get a reading of his surroundings. "I suddenly knew where the doors were," he says, "and whether they were open or shut."

For people who can see, the sense of perception is dominated by vision. In fact, over the course of evolution, our hearing has grown to assume a subordinate role, concentrating on things that make noises themselves -- on the hungry jaguar creeping through the underbrush or the guest at the loud party calling out from across the room. But when it comes to sound-based orientation, echoes can be misleading.

"For this reason, the brains of people who can see tend to suppress the spatial echo," says Lutz Wiegrebe, a Munich-based neurobiologist. "It is automatically canceled out as mere background noise." But he adds that the information is not lost. "You can quickly learn how to make use of it," he says. "For blind people, that would definitely make sense."

Indeed, most blind people intuitively know a little about how echolocation works. Some hit the sidewalk with a cane as they walk in order to locate a doorway; others snap their fingers when they enter someone else's bathroom to locate the sink, which returns a hollow echo. But hitting a stick on various surfaces returns a different sound each time. And snaps of the finger take place at varying distances from the ear -- and the brain processes them differently each time as a result.

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