Some people use echolocation to get around
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Blind people cannot see, but that comes in varying degrees. Only about 18% of people who are legally blind see nothing at all, only darkness. To get around, most use a cane pointed and waved in front of them to detect objects, steps, and holes. Only about 2-5% of blind people have guide dogs, mostly because of their cost (food, veterinary care, and supplies), need to care for the dog, and lack of actual need to move around.
Various technologies exist to help blind (or sight-impaired, if you wish to be accurate) people to navigate in their daily lives. They can range from tens to thousands of dollars.
- Smartphone apps like BlindSquare cost $40-60.
- A new strap around your arm called the WayBand costs $179.
- Handheld or wearable computer devices like StellarTrek, Glidance, and the Biped Vest can run from $1,000 to $1,500 to $2,000-3,000, respectively.
- Smart glasses and visors are the most expensive at $4,000 for OrCam MyEye Pro and $7,000 for eSight 4.
Some blind people rely on echoes from taps of their cane or stomping feet to get a relative position of objects. But other than the standard white cane, some people rely on themselves using sound that they make with their mouths in a process called echolocation. Basically, like a bat or dolphin, echolocation involves sending out a clicking sound and interpreting the echo it makes. It helps judge size, position, shape, and even texture of objects in front or to the sides.
Here is a video showing Daniel Kish (President of the
World Access for the Blind) demonstrating this and explaining aspects of human echolocation.
The first report of blind people with higher level abilities in hearing was published in 1749 by
Denis Diderot, who was a philosopher, art critic, and writer. He also co-created a general encyclopedia in France in 1751. Some of his writing was on science topics, and he compiled them in a collection called
Memoires sur differents sujets de mathematique (1748). In it, he wrote about mathematics, physics, and natural philosophy, and he was very interested in acoustics, the branch of physics that studies sound. Some of his essays in the 1748 work dealt with original ideas on acoustics, tension, and air resistance. He had a blind friend who could sense objects in front of him as well as the distance from him. Diderot thought this was due to what he called "facial vision" or "obstacle sense", caused by increased sensitivity of the facial nerves and end-organs to pressure on the face.
From 1808 to 1874, various researchers experimented with blind people and came up with many ideas about how they could tell objects were near. An Austrian psychologist Theodor Heller concluded from his tests that his subjects could perceive objects by sound at about 3-4 meters and by air pressure on the forehead at about 60-70 cm.
Researchers at the Smith-Kettlewell Eye Research Institute in San Francisco recently conducted a study to learn more about how this works. They worked with 4 male blind people who were already experts in practicing echolocation, and with 21 people who could see (12 male, 9 female) and were not trained in echolocation.
They were placed in a dark booth and wore a special cap with 64 sensors to detect their brain activity. They also wore earphones to hear computer-generated fake clicks like the human mouth would make from experts in echolocation.
A type of sensor cap like the one used in the study (BioSemi) The first simulated click was fed into their earphones as if they had made the sound themselves and projected it in front of them. A second click was computer generated to sound like it had reflected off something at different angles (5°, 10°, 15°, 20°, or 25°) to their left or right. The clicks were produced in different numbers, a set of 2 clicks, or 5, 8, or 11.
It should be no surprise to learn that the expert echolocators in this study performed better. From the brain activity sensors, the researchers determined that because of their experience in the past, their brains could process the clicks better than brains of sighted people doing this for the first time. Their processing was more sophisticated:
- they put together multiple clicks into a direction
- sighted people took each click/echo separately to make individual judgments of the location
People who use echolocation can also judge the size of objects, and sighted people can learn to tell the difference. California researchers Teng and Whitney set up 2 circular plates of different sizes in front of people in a dark room. The larger plate was sometimes on top, sometimes on the bottom. The angle of the top disk (θ) was also changed from 4º to 37º by raising the top disk. The test subjects made clicks with their mouths and reported on the location of the larger disk.
Setup: left shows what the test subjects faced in the dark, right shows a side view (Teng & Whitney, 2011)
These sighted people began to learn how to judge the location in 1-2 hours of testing, and by 3-6 hours they had reached their maximum ability. Some of them were almost the same ability as expert blind people who had experience using echolocation.
In another test, the 2 disks were the same size, and the object was to tell whether the top disk was to the left or right. That left-right angle from the test subject's head varied from 1.1°, 2.2°, 4.4°, 6.6°, and 13.2°. This was more difficult, and the average score was 63.5% correct even at the largest left-right angle of 13.2°. But some people were 95% correct at that angle. Two out of 11 people were able to judge as small an angle as 4.1° and 6.7°.
In 2021, researchers tested sighted volunteers against blind echolocation experts and novices. They faced a rectangular plate which was rotated to 4 positions. So, they could get 25% correct just by random guessing. The idea was to see how well they could judge the "shape" (by a different angle).
Sighted people and blind novices were trained in echolocation 2-3 hours a day, twice a week, for 10 weeks. The rate of learning of sighted and blind novices was the same, and their accuracy was also not different statistically. They got 38% to 69% correct from training period 1 to 20. If you separate the data, the sighted subjects got 76% by session 20, while the blind novices scored an average of 62%. By week 10, both novice groups were as good as the expert blind echolocators who were being tested at a further distance!
Researchers in the UK created virtual mazes for people to navigate in 2020. First, they made a real maze in different configurations but on a smaller scale than for people. Next, they put a mannequin head at different places and angles inside the mazes and generated a click from its mouth. That sound was recorded and used in the virtual maze when people heard the sounds on their earphones. Third, the participants listened to the sounds and imagined they were in a maze; they then used a keyboard to "move" themselves through the mazes based on the different sounds they heard. The final target sound had a different sound than the rest of the maze, so they knew when they had reached the end.
Three configurations of virtual mazes. Each square represents a computer key move
This study was done in 2020 using blindfolded sighted people, and in 2021 using blindfolded sighted people, blind novices, and expert blind echolocators. In 2020, the test subjects learned how to use the virtual echolocation to navigate through the mazes faster and with fewer "virtual collisions" with the "virtual walls" of the mazes. They had a 98% success rate after 14 training sessions. And, after 19 and 20 sessions, they were given mirror images of the mazes and succeeded at a similar rate.
In the 2021 study, blind and sighted novices became as good as expert echolocators after 14 sessions, and the sighted people ran the mazes faster than the experts (40.87 seconds, compared with 67.49 seconds). Some say that's because they weren't as afraid to bump into walls, even virtual ones, as the real blind people.
When people perform echolocation, what is being activated in the brain? Obviously, they hear the echoes of clicks, but many factors are involved in processing the information. It could be direction, size, even texture of what they hear. Mapping the brain can be done to see where it is active during different stimuli. This image shows generally where certain feelings are sensed. Vision is interpreted in the rear of the brain, while hearing is interpreted on the left and right sides. In the lower picture, you can see that there is some crossover (purple area) between the two senses.
A group of scientists compared 2 blind patients with sighted controls. They first allowed them to hear environmental noises (like wind, leaves rustling on trees) when the blind people made echolocation sounds. Both could detect objects, but the one that had been blind since 13 months old had more brain activity than one who had been blind since 14 years old. A sighted control showed no activity when they tried to identify objects that the blind people were echolocating.
When they removed all background noise and let them hear only the echolocation clicks and echoes, the blind people's brain activity was focused almost completely on the visual part of the brain as they tried to determine what the objects were. Controls again showed nothing.
So, anyone can learn to echolocate, and science is learning more about how it works. Here is another video with Daniel Kish not only explaining more about his use of echolocation, but demonstrating how it allows him to ride a bicycle and even travel.
