Especially the youtube video of Daniel Kisch and his friend Juan Ruiz is very impressive.
Basically, it seems like they reckon a form of edge location is more often used than trying to locate the body of an object.
Stay well Jacob Kruger Blind Biker Skype: BlindZA '...fate had broken his body, but not his spirit...'----- Original Message -----
"Zen" Bats Hit Their Target by Not Aiming at It! Paper in the Journal Science Reveals fundamental 'Targeting' Tradeoff.COLLEGE PARK, Md. - New research conducted at the University of Maryland's bat lab shows Egyptian fruit bats find a target by NOT aiming their guiding sonar directly at it. Instead, they alternately point the sound beam to either side of the target. The new findings by researchers from Maryland and the Weizmann Institute of Science in Israel suggest that this strategy optimizes the bats' ability to pinpoint the location of a target, but also makes it harder for them
to detect a target in the first place. "We think that this tradeoff between detecting a object and determining itslocation is fundamental to any process that involves tracking an object whether done by a bat, a dog or a human, and whether accomplished through hearing, smell
or sight," said coauthor Cynthia Moss, a University of Maryland professor of psychology, who directs interdisciplinary bat echolocation research in the university's Auditory Neuroethology Lab, better known as the bat lab.Moss, colleagues Nachum Ulanovsky and Yossi Yovel of the Weizmann Institute, and Ben Falk, a graduate student of Moss's in Maryland's Neuroscience and Cognitive Science Program, published their findings in this week's edition of the journal
Science. Ulanovsky, the paper's corresponding author, was a Maryland postdoctoral student under Moss. Youtube video at the URL http://www.youtube.com/watch?v=KLvjTXax8acFor this research, Ulanovsky and Yossi trained fruit bats to land on a spherical
target while relying exclusively on their sonar. Trained in Israel, the bats were then brought to Maryland to be studied in Moss's specialized lab. Highspeed infrared cameras recorded the bats movement in flight while the shape and direction of their sonar beam patterns was measured with a sensitive arrangement
of 20 microphones positioned around the large room. These bats emit pairedclicking sounds and the researchers found that the sonar beam created by each
click alternated to the left and right of a target. This alternating patterneffectively directed the inside edge, or maximum slope, of each sonar beam onto the target. As a result, any change in the relative position of the target to the bat reflected that large sonar edge back at the bat, delivering the largest
possible change in echo intensity.However, as the researchers note, there is a cost to this approach: less sound is reflected back to the bat from the object than if the sound beam were aimed
more directly toward the object. Thus the fruit bat's strategy of using the steepest edge of a sonar beam (which intuitively follows a mathematicaloptimization formula) sacrifices a little target-detection for pinpoint accuracy
in tracking. Detecting vs. Tracking.By changing the conditions of their experiments in the bat lab the researchers were able to show that the fruit bats will sometimes change their echolocation strategy based on the situation. To do this, a reflecting board was positioned
behind the target, creating "noise" echoes that competed with those from the target, potentially making detection of the target more difficult. In trialsunder these conditions, some bats altered their sound beam directional strategy.
These bats started off with the wide side to side pointing that maximizesdetermining location, but once they got closer, switched to point the beams from
both clicks almost directly at the target.Moss, who has been researching bat echolocation for 20 years, notes that even among different bat species there are different approaches to tracking objects.
Much of the research she and her students have conducted in the bat lab haslooked at big brown bats, which are common in the United States. Big brown bars generate sound with their vocal cords and aim the resulting sound beam directly
at their targets, an approach that maximizes their ability to detect the mosquitoes and other small, fast moving insects that serve as food."The difference in sonar beam directing strategies between the Egyptian Fruit bats and Big Brown bats may be related to the differences between their sound
production mechanisms (tongue clicks vs. vocalizations), echo processingsystems, behavioral requirements in nature, or other species differences," Moss
said. The researchers suggest other animals reflect similar approaches to thedetection versus tracking tradeoff. Their paper gives the example of a hound dog following an odor trail using a similar localization approach to that used by
the tongue clicking Egyptian fruit bats."People without sight use echolocation, in some cases also generating sound by
tongue clicking," said Moss. One such person, she noted, is Daniel Kish,Executive Director of World Access for the Blind. Totally blind from birth, Kish
uses tongue clicking for sonar that allows him to "see" his environment at avery high level, even allowing him to safely ride a bike in a city street. Kish
is "the first totally blind, national certified Orientation & MobilitySpecialist," according to the website for World Access for the Blind. Check out this YouTube video about Kish and his work educating others to use echolocation.
http://www.youtube.com/watch?v=uobuBc2GO0o "There are no measurements of the directionality of the sound beams used byblind echolocators like Kish," Moss said. "But looking at head movements in echo locating blind individuals, it seems that some may show a similar strategy [to
that of fruit bats]." Source URL: http://www.newsdesk.umd.edu/scitech/release.cfm?ArticleID=2078 __________ Information from ESET NOD32 Antivirus, version of virus signature database 4836 (20100204) __________ The message was checked by ESET NOD32 Antivirus. http://www.eset.com ---------- To send a message to the list, send any message to blindza@xxxxxxxxxxxxx ---------- To unsubscribe from this list, send a message to blindza-request@xxxxxxxxxxxxx with 'unsubscribe' in the subject line --- The 'homepage' for this list is at http://www.blindza.co.za
