From: ziert@beloit.edu (Tom Zier)
Newsgroups: sci.virtual-worlds
Subject: Re: SCI: VR and Psychology
Date: 22 Nov 92 18:25:02 GMT
Article-I.D.: u.1992Nov22.212041.1936
Organization: University of Washington
Originator: hlab@stein.u.washington.edu



> From: cdshaw@cs.ualberta.ca (Chris Shaw)
>
> >>The experiment to which you are referring is JJ Gibson's "Visual Cliff"
> >>experiments, in which very young animals are put on a plexiglass table in
> >>which one side has a checkerboard pattern that looks close (located at the
> >>table, top), while the other side has a two foot deep hole in it.
> >>shows fairly convincingly that animals have 3D visual perception at birth.
> 
> >I'm convinced that animals *and* children have 3D visual perception at 
> >birth.
> 
> Yes, sorry, I messed up the description. Human infants were also put on
> the table with the visual cliff, and human infants also markedly preferred
> the visually safe side of the table.
> 
> >I'm not sure that 3D visual perception is the reason that the child and
> >the very young animals behaved differently.
> 
> They behaved the same.

The discussion here has bumped up against what is called the
correlation problem, and brought to bear one of the test-cases that
has never been resolved by cognitivists in perceptual psychology (or
the ecological gang either). Can the infant know what the cliff
represents? No. Yet the child does not venture into the visually
UNSAFE area.

The cognitive group appeals to a mentalese language, and makes the
assumption that something must have been learned apriori, or that all
survival knowledge of this type is genetically encoded and available
from birth. There are logical extensions of this position that make
this a doubtful hypothesis though, such as; If we cannot conceive of
something without first having a mental language construct for it, and
we provide no avenue for interaction with the environment to modify
that language construct, then, Prof. Bohrs must have been born with
Quantum Mechanics already present within his mental language.

See "Determining the primary problem of visual perception:a Gibsonian
response to the 'correlation' objection" by Philip A. Glotzbach;
Philosophical Psychology, Vol. 5, No.1, 1992 for a brief discussion of
these arguments.

Two critical points of interest, though, which have not been properly
considered:

First; The assumption is made that perception of three dimensional
spaces must be responsible for the infants response. (damn Euclid,
sorry John) This is not the case.

Second; The critical presence of that grid-work under the plexiglass
in this experiment.

Just as color perception has come to be considered a prelinguistic
abillity

         See Thompson, E., Palacios, A. & Varela FJ (1992). "Ways of
             coloring: Comparative color vision as a case study for
             cognitive science" Behavioral and Brain Sciences. 15, 1-74

by some, ie we see bananas as distinctly yellow before we know either
of the words for banana or yellow, so there are apparently some
spacial understandings long before we understand the word 'cliff' or
'fall'.

Is there necessarilly a knowledge of 3 dimensional space involved when
the infant fails to tumble over the edge? No.

The distal knowledge of our visual environment seems to be based on
properties of stereoscopy and movement by other things through our
visual field,to which letter and number are well suited for the
descriptive task; but the perception of fine detail (which is the
checkerboard pattern noted above) appears to be supported by quite a
different neural network, one which is not well suited to either
letter or number.

The 'parvo-interblob-palestripe' network (Livingstone) promotes the
perception of 'formal' changes, fine detail, vertical elements, and it
happens also to be color blind. These cues, and their proper
applications, can easily explain the infant's response; given that
there is some prelinguistic abillity in spacial reckonings similar to
that prelinguistic abillity found in color perception pathways.

This is just one more of the long running arguments which a
prelinguistic, and pre Euclidean, analysis of visual forms helps to
resolve. Surely the infant cannot have been born with an understanding
of spacial theorems which it took the human race well over 15,000
years to invoke.

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t. zier                         ziert@beloit.edu
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Newsgroups: sci.virtual-worlds