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When the Blind Can See Like Bats

When the Blind Can See Like Bats
Bat biologist George Pollak discusses human echolocation and the ways in which bats and people are surprisingly similar. Biologist George Pollak has spent more than 35 years studying the auditory system in bats, and over that time one of the more surprising conclusions he’s drawn, about bats, is that for all the wondrousness of their echolocating abilities, the underlying neural circuitry that allows them to echolocate isn’t fundamentally different than the circuitry that humans and other mammals rely on to hear.

“That’s not where I started,” Pollak told me last year, when I interviewed him for a feature I later called “George Pollak’s Big Idea.”
When I came here and started working on the brain, I had every intention of understanding the super-specialized nature of the bat auditory system. I realized that the more things you find that correlate with, or explain, echolocation, the more papers you’re going to get in Science (and articles in Science do wonders for the advancement of one’s career). I tried, really tried, to find special adaptations, but I could not find them. What I found, every time I looked in the bat’s auditory system, is that what I was seeing were the same things, the same structures and neuronal response features, that my colleagues see who study the auditory systems of cats, rats and other animals.

I thought of Pollak’s big idea recently when I came across an article about Daniel Kish, one of the relatively few blind people in the world who has mastered the ability to echolocate. He does so by producing clicks with his tongue and then listening for the sounds that come back to him after his clicks bounce off of nearby (and not so nearby) objects. As the article explains:
Kish does not go around clicking like a madman. He uses his click sparingly and, depending on his location, varies the volume. When he’s outside, he’ll throw a loud click. In good conditions, he can hear a building 1,000 feet away, a tree from 30 feet, a person from six feet. Up close, he can echolocate a one-inch diameter pole. He can tell the difference between a pickup truck, a passenger car, and an SUV. He can locate trail signs in the forest, then run his finger across the engraved letters and determine which path to take. Every house, he explains, has its own acoustic signature.

...Kish has given a name to what he does — he calls it “FlashSonar” — but it’s more commonly known by its scientific term, echolocation. Bats, of course, use echolocation. Beluga whales too. Dolphins. And Daniel Kish. He is so accomplished at echolocation that he’s able to pedal his mountain bike through streets heavy with traffic and on precipitous dirt trails. He climbs trees. He camps out, by himself, deep in the wilderness. He’s lived for weeks at a time in a tiny cabin a two-mile hike from the nearest road. He travels around the globe. He’s a skilled cook, an avid swimmer, a fluid dance partner. Essentially, though in a way that is unfamiliar to nearly any other human being, Kish can see.

I emailed Pollak after reading the article on Kish to ask him if such human echolocation counts as evidence towards his argument that bats aren’t so special. He wrote:
The answer to your question as to whether I consider these cases to confirm my ideas about the conserved features of the auditory systems of bats, the answer is emphatically yes. I do not see how these people, and there are lots of them, could do this without the underlying neural circuitry.  Every animal that hears has to deal with echoes, and we are no exception. Due to selective advantages, some animals simply enhanced that pre-existing ability and used it extensively.  Incidentally, that happened several times during the course of evolution.  There are several species of birds, as well as mammals that can echolocate. It is, simply put, not that difficult or that extraordinary; it only appears to be.

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Pollak sent me the link to this video of a CBS news report about a California kid who can echolocate.

And, just as a bonus, here’s a kind of kitschy video about Kish, produced by the Discovery Channel.

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Thursday, 12 December 2019

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