Re: Implicit human echolocation

["Ewan A. Macpherson" <emacpher@xxxxxxxxx>]

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
> they 
> > 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. 
57:133-183.

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.
http://www-personal.umich.edu/~emacpher