Feburary 2002 Stephen F. Austin State University
The term echolocation was first coined by Donald Griffin, who, in 1938, discovered that bats navigate with the aid of high frequency sounds bouncing off obstacles in their environment (Uy, 1994). When you say echolocation to most people, they immediately think of bats and dolphins as the only creatures with this talent. It was surprising to me, as well as others, that blind humans have been using a form of echolocation for quite a long time. There have been many attempts to aid in mobility for the blind. From 1944 to 1947 the Committee on Sensory Devices of the National Academy of Sciences developed eighteen different portable devices to aid the blind in avoiding obstacles (Uy, 1994) none of which were very successful. Echolocation also has been observed in some forms of rodents, and some nocturnal cave birds. The first recorded instance of a blind human using echolocation was in 1749 by Diderot, who observed the ability of a blind person to determine the presence and even the distance of some objects (Uy, 1994).
Some theories on how the blind "see" have to do with a phenomenon called facial vision. Some thought that the skin of the subjects, especially of the outer ear, could sense pressure changes in the environment due to obstacles. Others believed that the Subjects were simply listening to the changes in the sound's echo, such as pitch, loudness, and even direction. Still others believed that the changes in pitch along with pressure sensitivity were needed in tandem to explain facial vision. A study in was conducted in 1947 by Worchel and Dallenbach to determine the validity of these theories. Some findings include: (1) the dermal surfaces of the external ears are not sufficient for the perception of obstacles. (2) The pressure theory of the "obstacle sense" is untenable. (3) Auditory stimulation is both a necessary and a sufficient condition for the perception of obstacles by the blind. (4) The aural mechanism involved is audition. (5) The auditory theory should be regarded as an established fact (Worchel and Dallenbach, 1947). This tells us that echolocation is totally dependant on sound and not pressures on the skin. Echolocation is definitely the way by which these blind Subjects "see".
Another study, done by Cotzin and Dallenbach in 1950, was designed to determine if the changes in pitch or in loudness were both required to echolocate. The study concluded that the changes in pitch a necessary and sufficient condition in echolocation. There is no evidence to suggest that loudness is a factor as long as the echoes are audible to the Subjects hearing (Cotzin and Dallenbach, 1950). Another study done some years later was designed to find if different spectra of canes' tapping sounds made any difference in the Subjects ability to navigate. The 10 different cane types used were all found to have identical effectiveness in echolocation, supporting the previous research that pitch changes are used by Subjects and not the initial pitches (Schenkman and Jansson, 1986). This partially explains why different blind Subjects have different sound methods such as, cane tapping, hissing, lip smacking, and clicking.
In 1962 Dr. Kellogg determined in a laboratory setting that blind, and blindfolded sighted Subjects could determine with great accuracy the distance and size of objects(Uy, 1994). He found that the farther away the objects were or the closer in relative size they were, the harder it was for the subjects to distinguish between the two. In 1965 Dr. Rice showed that percent correct detection of an object was a function of the distance and size of the object from the observer (Uy, 1994). So, at a greater distance, objects needed to be larger in diameter to be detected by Subjects. As the object was placed farther from a subject, the sound intensity of the echo became lower, and object detection became more difficult. As object size increased, the Subjects ability to detect the object drastically improved. The types of sounds preferred by human Subjects were also studied in Rice's 1965 experiment. Subjects used a variety of self-produced sounds, including tongue clicks, hisses, and lip-smacks. (Uy, 1994). This study determined that whichever method the subjects preferred was most effective for that individual. This suggests that the method of sound production is irrelevant but that it must have something to do with the changes that occur to the sounds when they are reflected.
Echolocation is used by the blind to help them navigate through their homes, along city streets, and even to help locate objects in their environment. One of the major hindrances of the blind population is their inability to "reach out" into their environment. Their inability to gather information at a distance and instead having to tactilely navigate through their world. Echolocation provides at least a rough way for the blind to "reach out" into their environment and somewhat help make up for their loss or absence of sight. Any method to improve on this visual compensation technique or to help teach it to others is well in need of future study. As I lack the technical background needed to help improve on the methods of echolocation in the blind, I have decided to focus on methods whereby competent blind echolocators could help teach these methods to others in the blind community.
There are many obstacles in the blind learning echolocation from other echolocators. "Mobility instructors discourage echolocation, especially clicking. While training with my first dog, I forgot myself and clicked to determine if I was near a pole. The instructor told me that my dog would be taken from me if I continued to make "those sounds," that they served no purpose, they made blind people objects of ridicule. And furthermore, I'd confuse the dog. I stopped clicking&emdash;until I returned home!" (Feinstein, 2001, p. 1) These are the types of problems the blind who try to utilize echolocation are up against in their adaptation to their environment. Many who are born blind are told in their young school lives not to click, tap their canes loudly, or stomp slightly. These are all echolocation methods and are all looked down upon as making the blind seem more helpless or ungainly. The view of these instructors is that the blind need to sort of hide themselves in the seeing community to try to "fit in" without causing too many waves. Until these sorts of obstacles are removed many in the blind community may never be able to use echolocation, or even be aware of it.
This area has not been it the spotlight of study recently. I was unable to find any research articles in the last five years. The most recent article published was in 1995. The authors argue that echolocation may be a basic ability of humans. They reviewed studies that suggest both blind and sighted humans are capable of precision in the perception of properties of some objects, such as distance, size, and shape. Relations were analyzed between sound pulse and echo that may provide information to support these arguments (Stoffregen and Pittenger, 1995). I was unable to find any articles, or even web based material, about teaching echolocation to the blind. I suggest a study to attempt to figure out what exact methods are used by echolocators. Then find out how to translate those methods so that a blind subject, that has no prior knowledge or experience with the phenomenon, might be able to learn. These studies would have to be done over a broad range of established echolocators to try to find the easiest or most teachable method for use in a school or program for the blind. After these methods are refined, if in fact they can be at all, then a school or program for the blind in our society could be instituted to help aid in their navigation through our world. Any attempt to help blind individuals better cope with their disability is well worth the efforts that we might put into researching the topic.
One problem that might arise in teaching echolocation is the difficulties that new blind Subjects run into. An experiment conducted in 1986 concluded that Subjects born blind had a much greater ability to identify obstacles correctly than did Subjects that were sighted and blindfolded (Boehm, 1986). This poses a problem when you attempt to teach echolocation to newly blind individuals. When you lose a sense you become more sensitive to your remaining senses to help compensate for that loss. During the period between loss of sight and this heightening of the senses, namely hearing, echolocation might be hard to teach to a newly blind subject. We would need to find out about this time of adjustment in newly blind subjects and determine when they would be sensitive enough to start to use echolocation effectively. The fact that even blindfolded, sighted, subjects can learn to use echolocation, while difficult and not as effective, is still a good sign that possibly all blind individuals will be able to learn to echolocate.
In conclusion, I would like to say that reading some of the accounts by echolocators, and how effective their "sight" is, is very astonishing. The detail that they report and how much easier it is for them to navigate in the world makes me wonder why there is no sort of formal educative process by which individuals could learn this skill. This is definitely an area that needs further attention for the aid of the blind community. The fact that young children born blind are discouraged from different echolocation methods must first be addressed before any sort of formal schooling be implemented for the blind community.
Rerences
Boehm, Richard. (1986). The use of echolocation as a mobility aid for blind persons. Journal of Visual Impairment & Blindness, Vol 80(9): 953-954.
Cotzin, Milton., Dallenbach, Karl M. (1950). "Facial vision:" the role that pitch and loudness play in the perception of obstacles by the blind. American Journal of Psychology, 63: 485-515.
Feinstein, Robert. (2001). Feinstein_click.html. www.bentvocies.org/bentvocies/
Schenkman, Bo N., Jansson, Gunnar. (1986). The detection and localization of objects by the blind with the aid of long cane tapping sounds. Human Factors, Vol 28(5): 607-618.
Stoffegen, Thomas A., Pittenger, John B. (1995). Human echolocation as a basic form of perception and action. Ecological Psychology, Vol 7(3): 181-216.
Cotzin, Milton., Dallenbach, Karl M. (1950). "Facial vision:" the role that pitch and loudness play in the perception of obstacles by the blind. American Journal of Psychology, 63: 485-515.
Uy, C., (1994). "Seeing" Sounds: Echolocation by Blind Humans. http://hcs.harvard.edu/~husn/BRIAN/vol1/echo.html
Worchel, Philip., Dallenbach, Karl M. (1947). "Facial vision," perception of obstacles by the deaf-blind. American Journal of Psychology, 60: 502-553.