Tuesday, November 27, 2012

Human Use of Echolocation

Daniel Kish wears prosthetic eyeballs. Legally blind, he produces short, sharp clicks with his tongue in order to navigate. He can describe the architecture of buildings one thousand feet away, and describe the distance, size, shape and texture of objects without touching them by using echolocatio . He can dance, ride a bike and even roller blade.

By having two ears, we are able to have the same sort of depth perception that we have with vision. We also hear better than we see. This is why it is so easy to have certain three dimensional illusions. For example we can see a shape in three dimensions on a computer screen, but we will always know it is an image. Meanwhile you will never see a shape that is behind you, but you will hear it.

The processing of these clicks takes place partially in the visual cortex. It is typical that regions essential for visual processing take on new roles in the brains of blind subjects. After all a piece of folk psychology that we are all familiar with is that blind people have exceptional hearing. And while I want to write this off as an example of the marvelous plasticitic brain, the truth is also that blind people must practice this skill, because they rely on it so much more.

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