Subject: Re: Gibson From: Christian Kaernbach <chris(at)PSYCHOLOGIE.UNI-LEIPZIG.DE> Date: Mon, 5 Mar 2001 09:52:46 +0100Dear 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. =D6ffnet er ihre Vorh=E4nge, die Lider, so "ist" da drau=DFen die sichtbare Welt der Dinge und der anderen Wesen. Nichts k=F6nnte den Verdacht erwecken, da=DF 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=B0 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) =3D 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) =3D X (14, 201) > Y(1,2) =3D X (3113, 21) =2E.. -- = 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/