Just in time for Halloween: Human Echo-location Allows Ears to "see" in the Dark
How many times have you stubbed your toe on that stupid table fumbling for the light switch in the middle of the night? (And it’s always the same toe!) Well, the days of stubbed digits and fumbling for the light switch may be over thanks to echo-location – a way of “seeing” with your ears and hearing capabilities.
Bats are a little creepy which explains why they are a staple for Halloween costumes and decorations. And despite being a little creepy, they serve us humans very well in the summer months thanks to their appetite for mosquitoes. Although they have very poor eyesight, they are able to devour a bunch of mosquitoes by employing a form of sonar – echo-location – to snatch those skeeters right out of the sky – in total darkness. You couldn’t do that, but then, you’re not a bat.
Lots of animals use echo-location to navigate on land, sea and in the air. In addition to bats, dolphins send out sonic signals and use the echoes produced by these signals to help them through the day without getting eaten by a whale, making it a good day, indeed.
Move Over Batman
Human echo-location essentially involves “seeing” with your ears. We may utilize echo-location on to some degree without realizing it, but when trained to use echo-location to locate objects that can’t be picked up visually, people with vision problems can improve their ability to get around without assistance.
A team of researchers at the University of Alcala de Henares (UAH), a well-respected school in Spain, have conducted research on human subjects who employ echo-location to help them, not only avoid objects, but to help identify them. According to the study’s author, people with vision impairment can learn to distinguish a tree from pavement using nothing more than echo-location. Hey, if a bat can snag a gnat at 50 feet while flying in the dark, humans can learn to distinguish a tree from the sidewalk.
The difference, of course, is that animals like bats and dolphins are constructed to use echo-location. A bat can send out 50 signals a second and read the echoes to catch that unfortunate bug floating nearby. Humans, who organically use echolocation, can only send out a few signals per second but enough to help them identify objects and their location relative to the individual.
Echo-location on helps us identify the location of a sound, almost instantaneously thanks in part to our sophisticated auditory system and localization abilities. Because the sound reaches the right and left ear a split second apart, the human brain is programmed to identify the source of a sound often before we see the object creating the sound. No doubt, this came in real handy for our early ancestors who could hear and “localize” the saber-tooth tiger before the tiger saw its breakfast.
In addition to protecting us from potential danger, echo-location in places us in the environment, as part of a cheering crowd or as a quiet, solo hiker out for an afternoon stroll.
“In certain circumstances, we humans could rival bats in our echo-location or bisonar capacity,” explained Juan Antonio Martenez, the study’s lead author. Martenez points out human echo-location skills are underutilized and he proposes humans employ a special clicking sound to create echoes to help us better utilize the skill.
|Dolphins use echo-location to "see" danger|
The study’s authors conclude, “The ideal sound is the ‘palate click’, a click made by placing the tip of the tongue on the palate, just behind the teeth, and moving it backwards, although it is often done downwards, which is wrong,” Martenez explains.
According to the study, no special skills are required and it doesn’t take years to tune your echo-location skills. Simply by heightening awareness of the role hearing plays in “seeing” the world is a big step toward more effective use of this device.
Practice making that clicking sound. Listen carefully for the echoes produced when the sound waves you produce return to your ears. Based on objects in the environment, differences will be heard in the echoes “dull” or “sharp” are often used to describe the differences.
In as little as two weeks, test subjects with varying degrees of site loss were able to identify pavement from trees and, more importantly, where objects were in relation to themselves.
And while not a solution to vision impairment, the study authors put forth a compelling argument that echo-location is (1) under-utilized as a tool by humans and (2) can be learned in a relatively short time – a benefit to those with total loss of sight who, with a little practice, can use sound to move down a busy sidewalk.
Martinez, in an interview on Spanish television explained that his team of specialists is now moving on to working with people with hearing and vision loss to use echo-location on as another tool in maintaining independence.
However, the team is also looking at other ways humans hear. According to Martenez, echo-location vibrations are also picked up by the tongue and bones of the body – certainly an experience we’ve all had. When the earth starts to rumble, you feel it before you hear or see the source of the rumble – a semi passing you on the interstate.
The conclusions of the Spanish study shed new light for those with vision and hearing loss by the discovery of a new, under-used tool to help us through the day.
Bats use it to capture dinner. Dolphins use it to communicate and to detect danger in their underwater environment. And, with a little practice, humans can use echo-location to guide them through the mazes that make up the day.
Try it the next time you’re fumbling in the dark. Make clicking sounds and listen for the echoes that return. These echoes are processed by the brain to help you identify where objects are and even what they are.
So, use your ears to see more clearly. Echo-location is your best tool, and you can learn to detect the world around you in just two weeks.
Click. Click. Click. Yep, I’m over here.