The term echolocation was first coined by Donald Griffin, who, in1938, discovered that bats navigate with the aid of high frequencysounds bouncing off obstacles in their environment (Uy, 1994). Whenyou say echolocation to most people, they immediately think of batsand dolphins as the only creatures with this talent. Echolocation hasalso been observed in some forms of rodents and nocturnal cave birds.It is surprising to most people that blind humans have been using aprimitive form of echolocation for quite some time. "To be sure,human echolocation is severely limited compared to that of bats anddolphins with respect to the types of targets that can be detectedand discriminated from each other, and especially with respect to theability to distinguish relevant echoes from competing sounds. But thefact remains that despite enormous differences in resolution andpractical usefulness many blind people, and also well-practicedblindfolded subjects, do make good use of echolocation..." (Griffin,p1, 2001). There have been many attempts to aid in mobility for blindhumans. From 1944 to 1947 the committee on Sensory Devices of theNational Academy of Sciences developed eighteen different portabledevices to aid the mobility of blind humans, none of which was verysuccessful (Uy, 1994). More recently it was discovered that peopleusing echolocation were more accurate in determining distances ofstationary objects if they, the echolocator, were moving rather thanstationary. This was discovered to be independent of the method ofsound production. (Rosenblum, Gordon, Jarquin, 2000)
Humans, as well as other organisms, can differentiate betweenechoes and true sounds. This is more difficult than one might firstthink. The process begins in the inferior colliculus of the humanbrain. The neurons in our brain act as cross-correlators, receivingimput from both ears. (Hoshino, Kuroiwa, 2001) The human brain usesdifferences in pitch, volume, and loss or change of certain pitchesimbedded in complex sounds. This ability to distinguish sounds iswhat makes it possible for people to use echolocation to assist themwith mobility. Some scientists will even go so far as to propose thatwe use echolocation to help enhance our depth perception frombinocular vision. (Stoffegen, Pittenger, 1995) There have beenextensive studies into finding a way to "hardwire" an echolocation orlight detection type device to blind individual's brains. (Duen,1996) Several problems come up when trying to do this. One suchproblem is that its extremely difficult to accurately map wires, orelectrodes, to specific neurons in our brains. Another problem isthat it would be pretty hard to explain the perceptions of sight tothe born blind people because they have never seen before. Theinterpretation of the nerve impulses sent to their brains by theprosthetic device would be difficult if not impossible to interpretfor the born blind. This is why it is crucial, at least with ourtechnologies at the current time, to find a way to teach echolocationto our blind population.
Peoples' attitudes differ greatly on the subject of echolocation.The sighted population in general doesn't know much about it. Thosewho have come across a blind individual who uses echolocationprobably didn't even know what on earth the blind person was doing.These kinds of attitudes and lack of understanding keep the generalpublic form knowing, much less doing, anything to help furtherecholocation research. The blind population that doesn't useecholocation generally have a negative attitude towards it. They feelthat those who use echolocation are drawing unwanted attention tothemselves. Echolocators are making people notice their blindnesseven more, which makes their lives harder. Even mobility instructorshave these predjudaces. Robert Feinstein, a born-blind echolocator,writes: "Mobility instructors discourage echolocation, especiallyclicking. While training with my first dog, I forgot myself andclicked to determine if I was near a pole. The instructor told methat my dog would be taken from me if I continued to make "thosesounds," that they served no purpose, that they made blind peopleobjects of ridicule. And furthermore, I'd confuse the dog. I stoppedclicking--until I returned home!" (Feinstein, 2001). These kinds ofattitudes by the sighted, as well as the blind, greatly affect theteaching of echolocation to the blind.
I hope to find a better way to teach echolocation in the blind. Inan effort to do this one must find the least complicated and mosteffective method of sound production. Due to the ease of obtainingenough blind subjects in my area, I will use born blind individuals.I predict that sounds made by the subjects themselves will greatlyimprove their echolocating abilities over that of artificiallyproduced sounds. This assumption is arrived at due to the fact thatthe echolocators, consciously or unconsciously, will change theirecholocating sounds slightly to fit their environment and will beable to gather more information from their surrounding than those whouse the artificial devices. Also sound duration has been tested withsighted, blindfolded subjects in other research (Uy, 1994). Thus,this experiment will manipulate sound duration. These data will helpdetermine what direction I should go to find the most effective soundduration for echolocation.
The participants will be blind individuals. It should be statedthat numerous tests have determined that blind persons are muchbetter echolocators than are blindfolded sighted individuals. (Boehm,1986) Participants will be randomly assigned to one of the 6 groupsat the time they sign up. There will be 90 males and 90 femalessolicited and randomly assigned for a total of 180 participants, or15 per group condition. The only requirement is that they have noprior experience with echolocating. Potential subjects should nothave had prior experience with actual echolocation, but they my haveprior knowledge of it. The subjects will be Stephen F. Austinstudents. Their ages will range from 18-24 years old. Subjects willbe solicited from undergraduate psychology classes at SFA. They willreceive blue cards from the experimenter to be used for courserequirements or as extra credit.
The experiment will require blindfolds for the participants,artificial sound production devices, and a course. The course will bea maze type track with turns and obstacles for the participants. Theblindfolds will be 24-inch-long strips of black cotton material twoinches in diameter. There will also be required an artificial soundproduction device for the three conditions. The hand held audiodevice will emit a sharp beep, a 0.75-second ping, or a sustainedhumming, for the immediate, short and continuous groups respectively.The device proposed was developed by Dr. Hughes and is the product ofseveral 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 artificialsounds will be electronically generated. The biological sounds willbe created by the subjects. The other variable is sound duration. Thethree types of sound duration are immediate, short, and continuous.The immediate sound will either be a click or beep for thecorresponding group. The short sound will be a ping or a whistle forthe correct group. Finally the continuous sound will be a hum,generated either electronically or biologically for the correctgroup. There were initially only going to be two types of soundvariable, short and immediate in this experiment. After furtherresearch it was discovered that some echolocation experiments usedcontinuous ambient sounds, so the third category was included, thecontinuous hums. (Ashmead et al, 1998) The immediate type will be analmost instantaneous sound. The short type will be a brieflysustained sound for approximately .5 seconds. The final type,continuous, will be a constant, or at least long duration, sound. Theduration of this sound will be constant for the artificial group andwill last as long as the participant can wistle for the biologicalgroup. This experiment will be a 2x3 between subjects groupdesign.
There will also be a novel course set up for the participants.There will be several corners and obstacles such as desks andbenches. The course will be contained within a large enclosed spaceto reduce outside noises.The participants will be given severaltrials to familiarize themselves with their task and so that thebiological sounds group can get used to making their sounds forecholocation. The trial course will be similar but not identical tothe test course. After that the participants will return thefollowing day to navigate the novel course. Their time to completethe course and the number of collisions they make will be recorded,combined, and plotted. The novel course was run by ten sightedindividuals and ten blind individuals. Neither of these two groupsused echolocation. These two groups served as a high and low rangeestimators to establish the composite score formula. Thenon-blindfolded individuals ran the course in an average 59 secondswith zero collisions. The blindfolded individuals in this group ranon average five minutes and 2 seconds, with ten collisions. Usingthese data a formula for finding a composite score was developed. Sothat the time run and number of collisions had equal weight it wasdetermined 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 andbiological groups. The t-observed value was 2.13 and the t-criticalvalue was 1.66 for p=.05. Thus we have a significant difference inthe artificial and biological groups. The artificial groups scoredsignificantly higher than the biological groups. Therefore thehypothesis is supported because the biological group scoredsignificantly lower than the artificial group. Further research willbe needed to determine the effectiveness of sound duration forbiologically produced sounds. Since the biological sound groupsscored statistically lower there is no need for further research onthe artificial groups.
The fact that you will notice a general trend in the figures,although not significant, of the shorter sounds being more effectivesuggest further research in the area of sound duration onecholocation using a between subjects ANOVA.. Further research to becarried out should try to find the differences, if there in fact areany, between the different sound duration on echolocation. Myproposed research to follow up this one would be that the clicksgroup would score lower on the composite score than either thewhistles group or the hums group. The idea being that the shorter thesound's duration the less combination of echoed sounds and truesounds and therefor it should be easier to echolocate. Futureresearch should also include differences in pitch and/or volume, aswell as which types of sounds are more effective inside vs. outside,or close up vs. far away. The differences between the blind and thesighted as far as echolocation might affect which method, orparticular pitch, volume, etc., might be most effective. The goal ofthis research, and any future research, should be to help generalizeand simplify the act of echolocation. If we can find an easy, andefficient way to teach echolocation to the blind then we can improvetheir mobility and help them to partially overcome their loss ofsight.
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