Could Echolocation Become a “Complete Sensory Replacement” for Sight? New Research Says Yes

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New research from the United Kingdom and Canada has examined the influence of echolocation (explained below), a method that many blind persons use to perceive the location and structure of objects in the environment.

The researchers determined, via controlled experimentation, that “echolocation is not just a functional tool to help visually impaired individuals navigate their environment; rather, it has the potential to be an actual sensory replacement for vision.”

Psychological Science

The research, entitled The Size-Weight Illusion Induced Through Human Echolocation, has been published online ahead of print in the December 19, 2014 issue of Psychological Science. Psychological Science is a peer-reviewed monthly journal that publishes the latest findings in cognitive, social, developmental, and health psychology, as well as behavioral neuroscience and biopsychology.

The authors are Gavin Buckingham, Jennifer L. Milne, Caitlin M. Byrne, and Melvyn A. Goodale, who represent the following institutions: School of Life Sciences, Heriot-Watt University, Edinburgh, United Kingdom; and the Brain and Mind Institute, University of Western Ontario, Canada.

What Is Echolocation?

Echolocation is the ability of humans to detect objects in their environments by sensing reflected sound waves from those objects. Human echolocation is similar in principle to active sonar and to the echolocation employed by some animal species, including bats and dolphins.

This ability is also used by some blind persons to navigate independently within a variety of environments by actively creating sounds (snapping the fingers, making clicking sounds with the mouth and tongue) and then interpreting the sound waves as they are reflected from nearby objects. A person trained to navigate by echolocation can accurately identify the location – and sometimes size – of nearby objects and use this information to travel independently in a variety of indoor and outdoor environments.

Here’s an interesting fact: Echolocation used to be called “facial vision” because it was believed that blind persons were somehow able to “see” and perceive objects by absorbing information through a special “mystical” facial sense. Now, of course, professionals realize that such perception is a function of hearing and, by extension, echolocation.

Echolocation is also a key component of learning to maximize input from the senses and function independently with vision loss:

If you concentrate on what you are hearing, and where sounds are coming from, you will be able to gain more information about your surroundings and begin to feel safer and more comfortable. For example, try this exercise to help you locate an open doorway in your home:

  • Walk slowly down any hallway in your home.
  • As you walk, you will sense a “closed-in” feeling until you reach an open doorway.
  • At that point, you will probably experience a sense of “openness” on your left or right side, depending on which side has the open doorway.

Also, rooms that are varying sizes will sound different from one other. A bathroom, for example, is usually small and contains hard surfaces, such as tiles and porcelain that can cause sounds to bounce and “echo.” A living room is larger, with rugs and soft furniture that can absorb and muffle sounds.

As you approach your entry door, especially if it is located in a foyer, you may experience a “closed in” feeling or sensation. This occurs because sounds are reflected from three very close walls. In a living room or larger space, you’ll notice that sounds suddenly “fall away,” since they take longer to reflect from wall to wall. The area around you will now feel more spacious and open.

The Size-Weight Illusion

The size-weight illusion, also called the Charpentier illusion, is the name given to the phenomenon that causes people to underestimate the weight of the larger of two objects (in the present experiment, the objects are boxes) that weigh the same.

One explanation for the illusion is that people judge the weight of an object from its appearance and then lift it with a predetermined force. The expectation is that a larger object will be heavier; therefore, it is lifted with greater force.

When that expectation is undermined, the brain is tricked into perceiving the object’s weight to be less than it actually is. The larger object, therefore, is lifted more easily than the smaller one, causing it to be perceived as lighter.

In other words, according to the size-weight illusion, when presented with two objects of the same weight but different sizes, the smaller object will always be perceived as heavier.

About the Echolocation Research: the Basics

Three groups participated in the experiment: (1) blind non-echolocators, (2) blind echolocators, and (3) control subjects with no visual impairment. All three groups were asked to judge the weight of three cubes/boxes that were identical in weight but differed in size.

Study participants never touched the boxes directly but lifted each one by pulling on a string-and-pulley construction attached to the top of each box. The results were as follows:

  • The blind non-echolocators did not experience the size-weight illusion. They correctly judged all of the boxes as weighing the same because they had no indication of the size of each box before they lifted it with the string and pulley.
  • The sighted control subjects, who were able to see the size of each box, experienced the size-weight illusion. They described the smallest box as being heavier than the largest one when they lifted each box with the string and pulley.
  • The blind echolocators, who detected the size of each box only through echolocation, also experienced the size-weight illusion. They described the smallest box as being heavier than the largest one when they lifted each box with the string and pulley.

The researchers concluded that using echolocation to determine the size of each box also influenced the blind echolocators’ perception of the weight of each box – much like the sighted control subjects.

More about the Research from Psychological Science

Excerpted from Echolocation acts as substitute sense for blind people, via EurekAlert! Science News:

Human echolocation operates as a viable “sense,” working in tandem with other senses to deliver information to people with visual impairment, according to new research published in Psychological Science.

Ironically, the proof for the vision-like qualities of echolocation came from blind echolocators wrongly judging how heavy objects of different sizes felt.

The experiment, conducted by psychological scientist Gavin Buckingham of Heriot-Watt University in Scotland and his colleagues at the Brain and Mind Institute at Western University in Canada, demonstrated that echolocators experience a “size-weight illusion” when they use their echolocation to get a sense of how big objects are, in just the same way as sighted people do when using … vision.

“We were interested to discover that echolocators, who only experienced the size of the box through echolocation, also experienced this illusion,” Buckingham added. “This showed that echolocation was able to influence their sense of how heavy something felt. This resembles how visual assessment influenced how heavy the boxes felt in the sighted group.”

The findings are consistent with earlier work showing that blind echolocators use “visual” regions of their brain when listening to their own echoes. This new work shows that echolocation is not just a functional tool to help visually impaired individuals navigate their environment, but actually has the potential to be a … sensory replacement for vision.

Blind Persons Have Been Using Echolocation for Many Years

Although I am interested in this new research, it’s important to note that many blind persons have been using echolocation, with great skill, for many years.

Ben Underwood

In 2007, Ben Underwood was featured in a People magazine profile that described his echolocation abilities. Ben was totally blind after retinal cancer claimed both of his eyes at age three.

When he was five years old, Ben discovered echolocation and learned to perceive and locate objects by making a steady stream of sounds with his tongue, then listening for echoes as they bounced off the surfaces around him. He used this skill to participate in running, rollerblading, skateboarding, basketball, and foosball. Ben died on January 19, 2009 at age 16, from the same cancer that claimed his vision.

Daniel Kish

Photo of Daniel Kish, President of World Access for the Blind, leading a group of blind hikers along a steep mountain trail. Photo credit: Volker Correll for World Access for the Blind

To learn more about echolocation, I recommend contacting Daniel Kish (pictured at left, leading a group of blind hikers), the founder and president of World Access for the Blind, an organization that provides instruction in FlashSonar (echolocation), mobility, and life skills to blind youth and adults.

Daniel, who also lost his vision from retinal cancer when he was 13 months old, has developed a wide array of echolocation techniques and uses those techniques to lead “no-holds-barred” hiking, mountain biking, and wilderness expeditions. World Access for the Blind believes that recreational activities are valuable ways for blind persons to build confidence, improve their navigation skills, and fully participate in society.

VisionAware will continue to report ongoing developments in echolocation research as they become available.

Additional Information

Daniel Kish photo credit: Volker Correll for World Access for the Blind