Human Echolocation

Teng et al.'s auditory Vernier task

Participants in Teng et al.’s experiment were asked to determine if the top disk was to the left or right of the bottom disk by making tongue clicks.

In 1939, Harvard graduate students Robert Galambos and Donald Griffin demonstrated that bats perceive the location of objects in their environment by emitting high-frequency sounds and analyzing their echoes, a sensory faculty known as echolocation. Although the possibility of bat echolocation had been discussed for years, Galambos and Griffin’s experiments were the first to prove it was true and the results shocked some of their colleagues. A week ago, at this year’s meeting of the Cognitive Neuroscience Society I was perhaps just as shocked to learn that humans can echolocate as well. This was demonstrated in a series of experiments by Santani Teng, Amrita Puri, and David Whitney (2011) who tested the echolocation acuity of six blind expert echolocators who use the skill in daily life and 11 sighted, blindfolded novice echolocators (Teng & Whitney, 2010). The experimental participants stood in front of an apparatus on which two disks were mounted, one above the other (Figure 1). The top disk was placed either to the left or the right of the lower disk by a variable distance and the participants had to determine whether or not the top disk lay to the right or left of the bottom disk by emitting series of tongue clicks (for an example see this CBS news clip about a human echolocator ). The blind expert echolocators performed well above chance on the task with a degree of accuracy comparable to that of the ability of sighted humans to locate objects in the periphery of their visual fields. In contrast, the blindfolded participants with normal vision could only perform slightly above chance, even when the disks were quite far apart (more than 12 degrees of visual angle). To ensure that participants were relying upon echolocation to perform the task (and not due to other cues such as the sounds of the experimenters adjusting the location of the disk), Tang et al. repeated the experiment but prohibited the participants from clicking. When not allowed to click, participant performance fell to chance levels.

-David Groppe

REFERENCES:

ResearchBlogging.org

Teng, S., Puri, A., Whitney, D. (2011) Fine spatial grain of human echolocation rivals peripheral vision. Poster at the Annual Meeting of the Cognitive Neuroscience Society.

Teng, S., & Whitney, D. (2010). The acuity of echolocation: Spatial resolution in sighted persons compared to the performance of an expert who is blind. Journal of Visual Impairment & Blindness, 105, 20-32. , 20-32

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~ by eeging on April 11, 2011.

3 Responses to “Human Echolocation”

  1. I had a chance to chat with Teng at this poster. He himself has tried to perform his echolocation experiment and says it’s very difficult for him (he’s sighted by the way). However, he says that it was possible for him to learn to judge the size of objects by making tongue clicks without considerable difficulty.

  2. to infer the size of object from echo is straight forward
    but to infer position is difficult
    i can only think that maybe the expert echolocator orient his head while clicking at different angles vis a vis the object to build a better sense of it’s general direction
    or maybe they use interferometry in their brain
    or something akin to a SAR algorithm (Synthetic Aperture Radar) in their Brain

  3. Hello! Thanks for the mention of our echolocation project. For anyone interested, the paper based on this poster has now been published:

    Teng, S., Puri, A. & Whitney, D. (2011). Ultrafine spatial acuity of blind expert human echolocators. Experimental Brain Research: DOI 10.1007/s00221-011-2951-1

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