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. Echolocation has also been observed in some forms of rodents and nocturnal cave birds. It is surprising to most people that blind humans have been using a primitive form of echolocation for quite some time. "To be sure, human echolocation is severely limited compared to that of bats and dolphins with respect to the types of targets that can be detected and discriminated from each other, and especially with respect to the ability to distinguish relevant echoes from competing sounds. But the fact remains that despite enormous differences in resolution and practical usefulness many blind people, and also well-practiced blindfolded subjects, do make good use of echolocation..." (Griffin, p1, 2001). There have been many attempts to aid in mobility for blind humans. From 1944 to 1947 the committee on Sensory Devices of the National Academy of Sciences developed eighteen different portable devices to aid the mobility of blind humans, none of which was very successful (Uy, 1994). More recently it was discovered that people using echolocation were more accurate in determining distances of stationary objects if they, the echolocator, were moving rather than stationary. This was discovered to be independent of the method of sound production. (Rosenblum, Gordon, Jarquin, 2000)
Humans, as well as other organisms, can differentiate between echoes and true sounds. This is more difficult than one might first think. The process begins in the inferior colliculus of the human brain. The neurons in our brain act as cross-correlators, receiving imput from both ears. (Hoshino, Kuroiwa, 2001) The human brain uses differences in pitch, volume, and loss or change of certain pitches imbedded in complex sounds. This ability to distinguish sounds is what makes it possible for people to use echolocation to assist them with mobility. Some scientists will even go so far as to propose that we use echolocation to help enhance our depth perception from binocular vision. (Stoffegen, Pittenger, 1995) There have been extensive studies into finding a way to "hardwire" an echolocation or light detection type device to blind individual's brains. (Duen, 1996) Several problems come up when trying to do this. One such problem is that its extremely difficult to accurately map wires, or electrodes, to specific neurons in our brains. Another problem is that it would be pretty hard to explain the perceptions of sight to the born blind people because they have never seen before. The interpretation of the nerve impulses sent to their brains by the prosthetic device would be difficult if not impossible to interpret for the born blind. This is why it is crucial, at least with our technologies at the current time, to find a way to teach echolocation to our blind population.
Peoples' attitudes differ greatly on the subject of echolocation. The sighted population in general doesn't know much about it. Those who have come across a blind individual who uses echolocation probably didn't even know what on earth the blind person was doing. These kinds of attitudes and lack of understanding keep the general public form knowing, much less doing, anything to help further echolocation research. The blind population that doesn't use echolocation generally have a negative attitude towards it. They feel that those who use echolocation are drawing unwanted attention to themselves. Echolocators are making people notice their blindness even more, which makes their lives harder. Even mobility instructors have these predjudaces. Robert Feinstein, a born-blind echolocator, writes: "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, that they made blind people objects of ridicule. And furthermore, I'd confuse the dog. I stopped clicking--until I returned home!" (Feinstein, 2001). These kinds of attitudes by the sighted, as well as the blind, greatly affect the teaching of echolocation to the blind.
I hope to find a better way to teach echolocation in the blind. In an effort to do this one must find the least complicated and most effective method of sound production. Due to the ease of obtaining enough blind subjects in my area, I will use born blind individuals. I predict that sounds made by the subjects themselves will greatly improve their echolocating abilities over that of artificially produced sounds. This assumption is arrived at due to the fact that the echolocators, consciously or unconsciously, will change their echolocating sounds slightly to fit their environment and will be able to gather more information from their surrounding than those who use the artificial devices. Also sound duration has been tested with sighted, blindfolded subjects in other research (Uy, 1994). Thus, this experiment will manipulate sound duration. These data will help determine what direction I should go to find the most effective sound duration for echolocation.
The participants will be blind individuals. It should be stated that numerous tests have determined that blind persons are much better echolocators than are blindfolded sighted individuals. (Boehm, 1986) Participants will be randomly assigned to one of the 6 groups at the time they sign up. There will be 90 males and 90 females solicited and randomly assigned for a total of 180 participants, or 15 per group condition. The only requirement is that they have no prior experience with echolocating. Potential subjects should not have had prior experience with actual echolocation, but they my have prior knowledge of it. The subjects will be Stephen F. Austin students. Their ages will range from 18-24 years old. Subjects will be solicited from undergraduate psychology classes at SFA. They will receive blue cards from the experimenter to be used for course requirements or as extra credit.
The experiment will require blindfolds for the participants, artificial sound production devices, and a course. The course will be a maze type track with turns and obstacles for the participants. The blindfolds will be 24-inch-long strips of black cotton material two inches in diameter. There will also be required an artificial sound production device for the three conditions. The hand held audio device will emit a sharp beep, a 0.75-second ping, or a sustained humming, for the immediate, short and continuous groups respectively. The device proposed was developed by Dr. Hughes and is the product of several years on research of echolocation sounds by computer (Hughes, B., 1999).
In my study there will be two IVs. The first will be sound type. The two sound types are artificial and biological. The artificial sounds will be electronically generated. The biological sounds will be created by the subjects. The other variable is sound duration. The three types of sound duration are immediate, short, and continuous. The immediate sound will either be a click or beep for the corresponding group. The short sound will be a ping or a whistle for the correct group. Finally the continuous sound will be a hum, generated either electronically or biologically for the correct group. There were initially only going to be two types of sound variable, short and immediate in this experiment. After further research it was discovered that some echolocation experiments used continuous ambient sounds, so the third category was included, the continuous hums. (Ashmead et al, 1998) The immediate type will be an almost instantaneous sound. The short type will be a briefly sustained sound for approximately .5 seconds. The final type, continuous, will be a constant, or at least long duration, sound. The duration of this sound will be constant for the artificial group and will last as long as the participant can wistle for the biological group. This experiment will be a 2x3 between subjects group design.
There will also be a novel course set up for the participants. There will be several corners and obstacles such as desks and benches. The course will be contained within a large enclosed space to reduce outside noises.The participants will be given several trials to familiarize themselves with their task and so that the biological sounds group can get used to making their sounds for echolocation. The trial course will be similar but not identical to the test course. After that the participants will return the following day to navigate the novel course. Their time to complete the course and the number of collisions they make will be recorded, combined, and plotted. The novel course was run by ten sighted individuals and ten blind individuals. Neither of these two groups used echolocation. These two groups served as a high and low range estimators to establish the composite score formula. The non-blindfolded individuals ran the course in an average 59 seconds with zero collisions. The blindfolded individuals in this group ran on average five minutes and 2 seconds, with ten collisions. Using these data a formula for finding a composite score was developed. So that the time run and number of collisions had equal weight it was determined that for the approximate difference in time, four minutes, the number of collisions difference, ten, would be made equal. Therefore, each collision added 24 seconds to the overall score.
The data analysis consisted of a t-test between the artificial and biological groups. The t-observed value was 2.13 and the t-critical value was 1.66 for p=.05. Thus we have a significant difference in the artificial and biological groups. The artificial groups scored significantly higher than the biological groups. Therefore the hypothesis is supported because the biological group scored significantly lower than the artificial group. Further research will be needed to determine the effectiveness of sound duration for biologically produced sounds. Since the biological sound groups scored statistically lower there is no need for further research on the artificial groups.
The fact that you will notice a general trend in the figures, although not significant, of the shorter sounds being more effective suggest further research in the area of sound duration on echolocation using a between subjects ANOVA.. Further research to be carried out should try to find the differences, if there in fact are any, between the different sound duration on echolocation. My proposed research to follow up this one would be that the clicks group would score lower on the composite score than either the whistles group or the hums group. The idea being that the shorter the sound's duration the less combination of echoed sounds and true sounds and therefor it should be easier to echolocate. Future research should also include differences in pitch and/or volume, as well as which types of sounds are more effective inside vs. outside, or close up vs. far away. The differences between the blind and the sighted as far as echolocation might affect which method, or particular pitch, volume, etc., might be most effective. The goal of this research, and any future research, should be to help generalize and simplify the act of echolocation. If we can find an easy, and efficient way to teach echolocation to the blind then we can improve their mobility and help them to partially overcome their loss of sight.
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Rosenblum, L. D., Gordon, M., Jarquin, L., (2000). Echolocation Distance by Moving and Stationary Listeners. Ecological Psychology, 12(3), 181.
Stoffegen, T. A., Pittenger, J. B., (1995). Human echolocation as a basic form of perception and action. Ecological Psychology, 7(3), 181-216.
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