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Re: Gibson

Dear Al,

> I agree that there is a pattern of flow in the light that reaches
> the eyes as we walk forward.  However, until the  brain makes
> sense of this pattern, it is not "about" the world.  It is merely
> "caused by" the world.  These ideas "about" and "caused by" are
> not synonymous.  Everything is caused by something, but if
> everything is information, the word loses its unique meaning.

I wholeheartedly agree with your criticism of the Gibsonian hypothesis.
Let me add a didactical aspect. I start my lecture on perception with a
citation by the famous Gestalt psychologist Wolfgang Metzger, in his
book "Gesetze des Sehens" (i.e. "Laws of Vision", 1st ed. 1936, I think
it is the beginning of his book):
   Dem Menschen, der unbefangen um sich schaut, kommen seine eigenen
   Augen dabei wie eine Art Fenster vor. Öffnet er ihre Vorhänge,
   die Lider, so "ist" da draußen die sichtbare Welt der Dinge
   und der anderen Wesen. Nichts könnte den Verdacht erwecken,
   daß irgendeine der daran erkennbaren Eigenschaften
   ihren Ursprung im Betrachter habe...
now let me try(!) a translation:
   For man, looking around him ingenuously, his own eyes appear
   to be a kind of windows. Opening their blinds, the lids, the
   visible world of things and other beings "is" outside. Nothing
   could raise suspicion, that anyone of the discernible properties
   of the world would have their origin in the viewer...
I cite this because I want students to overcome the naive concept of
perception ("What does cause your perception that this shoe is red?"
"Why, it is red, isn't it?"). The Gibsonian use of the word "meaning"
would make it incredibly hard to avoid having my students fall back to
this naive view. I am sure the Gibsonian view can be stated such that
the difference could finally be understood. I am not sure whether this
would hold for all of my students. I don't teach Gibson.

Your movie example deserves further consideration. If the pixel
permutation were done in a retina-stable way, the brain would probably
be able to adapt to this permutation after some days or weeks. Consider
the famous experiments by Helmholtz with prism glasses and follow-up
studies with 180° turn-around glasses which showed the enormous
flexibility of the brain to adapt to optical transformations. The
ability to make sense of the permuted movie proves that something _is_
in the outside world. I would call it physics, not meaning...

- Christian

> Another example: Suppose there were a device that took a
> pixelized photo, A, and mapped each point in it onto an output
> photo, B.  If the mapping were:
> Y (i,j) = X (i,j)
> then the output photo would be a copy of the input.  Suppose,
> instead, that we used a random, but fixed, function to do the
> mapping such that, for example,
> Y (1,1) = X (14, 201)
> Y(1,2) = X (3113, 21)

Dr. Christian Kaernbach
Institut fuer Allgemeine Psychologie
Universitaet Leipzig  
Seeburgstr. 14-20     Tel.: +49 341 97-35968
04 103 Leipzig        Fax:  +49 341 97-35969
Germany               http://www.kaernbach.de/