Humans Behave Surprisingly Bat-Like in Echolocation Study
Bats aren't the only creatures that can navigate without their eyes.
Bats and dolphins aren’t the only animals that can use echolocation to detect objects in their environments. Humans can use echolocation too, and it’s a game-changer for people who are blind. On Wednesday, scientists provided further proof that this ability isn’t just reserved for superheroes in a new study, arguing that humans are more bat-like than we might think.
Human echolocation reached the world stage in 2015, after Daniel Kish, an expert in human echolocation who has been blind since he was an infant, discussed the technique in a TED talk that went viral (it has over 1.2 million views). The new paper, published Wednesday in the Proceedings of the Royal Society B, builds on Kish’s talk, providing evidence that he isn’t alone in his capabilities.
“Our results are, to our knowledge, the first to show that human echolocation experts adjust their emissions to improve sensory sampling,” the team of international researchers, led by Durham University psychology professor Lore Thaler, Ph.D., writes in the paper. “Just as in certain species of bats or mammals, people can echolocate by making their own sound emission.”
In the study, the scientists asked eight blind echolocators to spot a 17.5-centimeter disc one meter away from them in a foam-lined room. When the disc was directly in front of them, 100 percent of the participants were able to spot it. A person’s relative position to the object was the biggest factor in determining their success: When the disc was moved slightly behind them, their overall success rate dropped to 80 percent, and when it was placed directly behind them, the success rate was 50 percent.
The scientists noted that when the target was in front of them, the participants only needed to click one or two times before finding it. Their number of clicks, and the loudness of those clicks, increased as the target moved: Between 10 to 12 clicks were used to identify the disc when it was slightly behind them.
The principle behind echolocation is the same in both humans and bats, but there are some differences in the way it aids navigation. When bats (which are not blind) use echolocation, they send out quick clicks indiscernible to the human ear into their environment. Then they swivel their ears to listen for the echoes that result from the sound waves bouncing off nearby objects, which build up to create a sonic map. The frequency of the echoing sound waves — whether high or low — tells the bat how far away the objects around them are.
Like bats, human echolocators create sounds and then interpret the resulting sound waves to sense objects around them. Humans can’t swivel their ears to pick up on the sound waves, though, so the process for human echolocation is less accurate: this is what accounts for the decreasing success of echolocators in the study when the position of the disc was moved.
Human echolocation isn’t perfect, but it’s still incredibly useful to those who can’t see. Thaler has described it as an “acoustic flashlight,” explaining that it might not let people “see” per se but does allow them to orient themselves relative to objects in their vicinity. Brain scans conducted in other studies have revealed that the brain’s visual system is ignited during human echolocation, indicating that the process is “seeing” in some way.
“It is clear that echolocation may enable some blind people to do things that are otherwise thought to be impossible without vision, potentially providing them with a high degree of independence in their daily lives and demonstrating that echolocation can serve as an effective mobility strategy in the blind,” wrote Thaler in a 2016 paper in Wiley Interdisciplinary Reviews: Cognitive Science.
On Wednesday, she told the Guardian that human echolocation is a very “learnable skill” and asserts that, when paired with a cane or guide dog, it can become an invaluable tool for exploring new places. Like any skill, though, practice makes perfect. Kish, who as a child instinctively began using his tongue to click and send out bursts of sound to better understand the physical space around him, has been doing this for years — which is why he can use his echolocation to successfully ride a bike: