From: mmt@BEN.DCIEM.DND.CA
Newsgroups: bit.listserv.csg-l
Subject: Re: interactionism
Date: 19 Aug 92 18:50:23 GMT
Comments: Gated by NETNEWS@AUVM.AMERICAN.EDU

[Martin Taylor 920819 14:15]
(Penni Sibun 920818.1200) (sorry about the [y] earlier)


>   [Martin Taylor 920818 11:50]
>   (Penn[i] Sibun 920817)
>
>   >  there's just tons of literature on
>   >perception that suggest that perc. is a *lot* of work; in fact it
>   >involves action--perhaps to the degree that p. and a. are inseparable.
>   >(``active vision'' is a current buzzphrase.)
>
>   This was cast as a criticism of PCT, but in fact it seems to be a reasonable
>   description of how PCT says perception works.  An ECS that is trying to
>   achieve a percept can go only by its error signal.
>
>maybe someone can explain this to me.  when you say ``signal'' or
>``variable'' or ``percept'', it has connotations to me of a unified
>thing, like a tone, or a light intensity.  but when i look at the
>road, i am not perceiving something like a tone.  if you can explain
>how all the stuff my eyes take in can be a single unified thing, maybe
>i won't find it so oversimplified.

(Aside: as a student of language, you won't be surprised to know that I find
long postings without sentence capitalization hard to read.)

Maybe the subsequent postings have cleared this up for you, but in case not,
here's another attempt.

I don't know how long you have been following CSG-L, but it seems that there
is a foundational notion missing.  PCT does not deal with the human as a
single control system that controls "all the stuff my eyes take in" as "a
single unified thing."  Instead, there is a vast hierarchy of elementary
control systems that make up a hierarchic control system.  Each of the
elementary control systems (ECSs) do control one unified thing, but that
thing (percept) is a function of many inputs.  At the very lowest level,
the inputs are sensory, but above that they include the results of lower-
level perceptual functions in lower-level ECSs.  Your perception of being
in the middle of the road may be a "unified thing" but it implies the
perception of myriads of other variables, such as the intensity of light off
that patch of snow to the left, the orientation of the line projected by
the centre stripe of the road, the location of the dark corresponding to
the windshield pillar, the pressure on your buttocks... You may not be
conscious of these other percepts--in PCT the notion of percept is quite
distinct from that of consciousness--but without them your perception of
being *so far* to the left of the centre line will be less precise than it
might otherwise be.

When we say "signal" we usually mean the value of the unified thing that
has been derived from all the lower-level complex, or alternatively the
reference level with which the percept is compared.  "Variable" can be
anywhere.  I tend to use "CEV" for "Complex Envirnmental Variable" to
denote some structure in time and space that corresponds to a percept.  One
can never be sure that a CEV actually exists "out there" but if our actions
control a percept that we feel to be based on a particular CEV, then we have
some evidence that the CEV is a useful perceptual construct.  It is "real"
for us (though perhaps not for anyone else).  Internally, percepts, reference
signals, errors, output, etc. are all "variables," and there are probably
many more.  "Democracy" could be a perceptual function that has a particular
level in specific curcumstances (very low level these four days in the USA,
I'm afraid, for me), but if there is a CEV corresponding to my (unitary)
percept "democracy," I'm pretty sure it won't be exactly the same CEV that
affects your perception of "democracy."

Another word to be careful of in PCT terms is "action."  Actions are observable
but hard to interpret.  An observer sees hands and arms moving, but if those
actions were duplicated on another occasion, it is highly unlikely they would
have any useful effect.  Actions affect CEVs, and the effects lead to changes
in the percepts associated with the affected CEVs.  But unless the observer
knows what the CEV *is*, the actions are meaningless.  And to know what the
CEV is, is to know the intentions of the actor.

You are talking, for example, with a few other people, and one gets up and
opens the door.  You see the arm and hand manipulating the doorknob.  But the
real question you can ask him or her is "Are you leaving, or are you leaving?"
Your two alternatives are opposites, couched in exactly the same words.  You
want to know whether he or she is finished with the discussion or is coming
back after a short but necessary break.  You need to know what CEV is being
acted upon.  Is it one related to the interest value of the discussion, or
is it related to internal physiological states?  The actions are the same,
but the implications are very different.  And so it is with your question.
Two almost identical actions (word strings with intonation) have meanings
associated with the CEVs you see as possibly related to controlled percepts
in the person opening the door.  All unitary, all complex in construction.

Anyway, the root misunderstanding expressed in your quoted paragraph seems to
be based on the idea that there is a single unitary percept that we control,
whereas in PCT terms, each ECS controls a single unitary percept, but there
are myriads of them involved in even very simple real-world activities such
as driving.

Hope this helps

Martin
Comments: Gated by NETNEWS@AUVM.AMERICAN.EDU