The Mystery of Sonar Boy
Bats use echolocation. Can people use it, too?
In early September, a 14-year-old kid with empty eye sockets strode on stage for a taping of the talk show Ellen. "I'm not blind," he told the host to wild applause, "I just can't see." The story seemed lifted from the pages of a comic book: At the age of 3, Ben Underwood lost his eyes to retinal cancer. Three years later, he discovered that he could sense objects around him by making little clicking noises with his tongue and then listening for the echoes. Now, he uses these clicks to find doorways and locate cars on the street. That's right—he navigates with sonar.
The Sonar Boy had been on the CBS Evening News a few days earlier, Rollerblading, playing Foosball, and throwing pillows at his sisters. But his big break came back in July, when People magazine ran a five-page profile that dubbed him "The Boy Who Sees With Sound." "Ben pushes the limits of human perception," one expert told People. Watch the clips of him on YouTube and it's hard to disagree—if this kid's not a prodigy, he's a brilliant fraud.
Ben Underwood's echolocation isn't a hoax, but it's not an unexplained mystery, either. Ben really can sense nearby objects with reflected sound waves. But so can you. If Sonar Boy is some kind of superhero, then we're a nation of Daredevils.
Go ahead and try out the skill you never knew you had. First, close your eyes and put on a blindfold, and then ask a friend to move a frying pan forward and backward in front of your face. Now start making noises—any noises you want. You can click your tongue like Sonar Boy, or you can whistle, or you can sing a scale. With a little bit of practice, you'll be able to tell when the pan is close to you and when it's not.
You won't even know you're hearing an echo. In general, you'll only catch your sound repeated if it bounces off something far away: First you'd hear your own voice, then a pause, and then the echo of your voice returning to your ear. When you bounce a noise off of something that's close to your face—like the frying pan—it zips back so fast that it overlaps with the original sound. The brain hears the combination of the two as something like an alteration in pitch. So, you may not hear a discrete echo when you whistle at a frying pan, but your ears can pick up the difference.
Anyone can echolocate, but blind people happen to be especially good at it. (And Ben Underwood seems to be even better than most blind people.) You don't even have to make your own clicks or whistles; some people use the echoes from ambient noise, or even from their own footsteps, to sense obstacles. With trained ears, you might be able to tell when you're passing an open door in a hallway by the way the sound "opens up" around you.
For centuries, scientists have been working on the question of how blind people compensate for their loss of vision. Diderot's "Letter on the Blind" from 1749 described an "amazing ability" to navigate in the absence of sight, which later became known as "facial vision." (Practitioners described a sensation of feeling objects or barriers on the skin of their faces.) The notion that this spatial sense arose from touch and not sound was only disproved in the 1940s.
At the time, no one knew exactly how a person might "hear" an object. Echolocation was still a new concept—the term had been coined a few years before, and its use by bats had only been documented in 1938. Research into sonar exploded in the early years of the Cold War, due to its apparent military applications. But the notion wasn't systematically applied to blind people—and "facial vision"—until a notorious psychologist named Winthrop Kellogg began his human-echolocation research program around the time of the Cuban Missile Crisis.
Kellogg was best known for a controversial, Depression-era experiment in which he raised a baby chimpanzee alongside his own infant son. (Click here for a movie he made of the two babies.) But he'd also spent years showing that porpoises, like bats, use reflected sound waves to navigate their environment. In 1962, he published his first major study showing the ability in humans. Using a setup not much different than the frying-pan test described above, Kellogg was able to prove that people—and especially blind people—can use self-generated noises to locate discs of various sizes and materials. (His subjects could even distinguish between discs covered in velvet and denim.)
Of course, the human echolocation he demonstrated wasn't nearly as sharp as that of other animals. Bats, for example, emit and hear sounds at very high frequencies, which allows them to track tiny insects in midflight. Some bats even compensate for the Doppler effect as they swoop toward their prey and cancel out the interfering sound of their own fluttering wings. People couldn't do any of this fine-scale discrimination, but Kellogg showed that they could use sound to sense a world of blobs and textures.