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Re: Implicit human echolocation
On 31 May 2007 at 9:33, Bob Masta wrote:
> On 30 May 2007 at 9:31, Bruno L. Giordano wrote:
> > An improbable single-trial experiment could address this question:
> > blindfolded participants are asked to walk along a path, as long as
> > wish. They wouldn't be informed that a wall is obstructing the path.
> Harry Erwin has mentioned Griffin's "Listening in the Dark".
> As I recall, this book discusses an experiement almost
> identical to the one you propose. I believe Griffin used a
> moveable barrier in a straight hallway, set to a random
> distance down the hall without the knowledge of the
> blindfolded subject. The subject knew he would encounter
> the barrier, but not where/when.
> I think the experiment was repeated with a microphone
> on a trolley in place of the subject, and the subject would
> then listen through headphones as the trolley was moved
> down the hall.
That experiment is indeed described by Griffin (at least in "Echoes of
Bats and Men"), but was done by Supa, Cotzin & Dallenbach (1944):
"Facial vision", the perception of obstacles by the blind. Am.J.Psych.
Blind subjects were able to detect the barrier equally well by means of
the recordings or when their faces were covered with a felt veil, thus
disproving the "facial" part.
Ewan Macpherson, Ph.D. <emacpher@xxxxxxxxx>
Research Investigator, Central Systems Laboratory
Kresge Hearing Research Institute, U. Mich.