Fw: Re: direct/indirect perception

[Al Bregman <bregman@xxxxxxxxxxxxxxxxxxxx>]

Hi Peter,

 Let me respond to some of your comments (with a copy to the
 list):

 You wrote:
"As I understand it, Gibson's formulation of direct perception
actually came
out of his desire to circumvent the 'ghost in the machine' - is
that about
right? Nevertheless, his idea that scientific reductionism can
actually
result in impoverished experimental circumstances that exclude
the very elements of perception requiring examination, has been
useful.
The 'embedded-ness' of perception in 'proper' environments might
not be best represented in some laboratory environments.
Doesn't some of your own work come from a similarly ecological
(no capitalised 'E') motivation?"

My work came about by accident, but early on, I realized that I
was looking at a process that had a function in a natural
environment.  As time passed, I guided my research increasingly
by this idea.  I agree with Gibson's idea that it is important to
look at the stimulation offered by the stimulus input before
concluding that memory and inference are playing a role.  I take
this merely as good advice without going along with his more
radical ideas.

 You also wrote:
"That said, I agree with the synthetic component of
perception,though not
necessarily  going as far as R.L Gregory, who claims up to 90%
synthetic."

Such numbers are meaningless.  My approach to perception through
synthesis is this:  The world is populated by distinct entities
and causes, each of which is going about its business.
However, because our senses receive information about all of them
at once, our brain develops bets about which entities may be
present
in the scene, and sees whether a composition of such entities
will
account for the incoming data.  Furthermore the brain "knows
about" common transformations in the world, such as rotation,
occlusion, deletion of parts, color of light source, reflections,
shadowing, changes in the perceiver's viewpoint, and so on.  So
it tests whether the application of a set of proposed
transformations to a set of proposed schemas would yield the data
that reaches  the sense organs.  If it accounts for part of the
data well but leaves over some unexplained sense data, some
additional hypotheses may be introduced that fit the "shape" of
the unexplained data.  A process similar to this was called
assimilation by Jean Piaget.

This is the same strategy that a scientist uses.  The data are
interpreted as having been shaped by a number of causes in
tandem.  The data set is viewed as a composite, shaped by many
causal factors.  The more you know about the other factors that
have shaped the data, the more easy it is to see the effects of
the particular one you are interested in.  Piaget had a name for
the human mind's ability to represent the simultaneous influence
of two causal factors (each represented by a schema).  He
called it "one schema assimilating another".

I believe that all understanding, whether perceptual or
cognitive, works by this process of composing hypotheses about
underlying factors to account for the data.  That's why I can't
be a Gibsonian.  The analysis by synthesis approach doesn't deny
that simple bottom-up processes are important.  Without them, how
would one know which underlying schemas should be entered into
the composition?

Gibsonians (such as Michael Turvey and his colleagues) have had
their greatest successes in managing without representation by
accounting for sensorimotor loops where the human is controlling
some external process.  No representation is needed.  But I
would argue that this is because no "understanding" is involved.

 You also wrote:
"In respect of Bruno's point as to whether anything would be
altered by the assertion that perception is direct , the point
is that experimental
circumstances could never *completely* represent real ones; but
surely we know that already?"

In reply to Bruno, I would say that if perception were indeed
direct, i.e., occurred without representations, then the process
of "imagination", which obviously requires a representation,
would have nothing to do with perception.  Indeed, it would be a
complete mystery as to where the representation used by
imagination had come from, if not from sensory perception. From
extra-sensory perception?  Apparently not so, because the parts
of the brain that light up in a brain image when somebody is
asked to imagine something are intimately related to those that
light up when the subject is perceiving the thing itself (sorry;
I don't have the reference).  I think the Gibsonian view can only
be maintained by ignoring the functions of the mind that take
place in reference to an object, but not in the immediate
presence of the object itself (e.g., imagination, dreaming,
judgement, and so on, which we can call "offline phenomena"),

Another theoretical position that rejected representation, the
Behaviorism of J.B. Watson and B.F. Skinner, was ultimately
discarded because of its banishing of the offline phenomena from
its account of behavior.  Similarly, an account of perception
that does not connect it with the offline phenomena may have to
be discarded, no matter how successful it is in dealing with a
narrow range of phenomena.

Best,

 Al
------------------------------------------------
Albert S. Bregman, Emeritus Professor
Dept of Psychology, McGill University
1205 Docteur Penfield Avenue
Montreal, QC, Canada H3A 1B1
Office:
     Phone:  +1 (514) 398-6103
     Fax: +1 (514) 398-4896
Home phone & Fax: +1 (514) 484-2592
Email:   al.bregman@mcgill.ca
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