[From Bill Powers (940723.1540 MDT)]
Bill Leach (940723.14:41 EDT)--
Is it really possible for sensory nerves to register "Absolute
position"? A difficultly here of course, is what is "absolute
postition" and what is "relative position"?
Sorry, a little too much shorthand. By absolute position I mean position
on the retina, or in a map corresponding 1:1 with it. I, too have heard
of Einstein.
I am inclined to believe (for what little it might be worth) that the
"relationships" between "things" are all that we can perceive.
Well, I begs to differ with yer honor. When you look at a sheet of
paper, do you get a sense of how bright it is? That's intensity
perception: "how much." When you smell something, can you often say what
kind of smell it is (fishy, fruity, flowery, acrid)? That's sensation
perception. When you hear a triad, can you say whether it is major or
minor? That's configuration perception (auditory Gestalt). When you look
at an analogue clock, do you get a sense of how fast the second-hand is
moving? That's transition perception. When you see and hear a
firecracker go off, does this strike you as a unitary event? That's
(obviously) event perception. And when you see one soldier out of step
with the others, THAT's relationship perception.
And of course, it isn't necessary to SAY what these perceptions are: you
just experience them.
If I've guessed right, these are six (of the 11) levels of perception.
Analyzing any one of them into components that are something other than
smaller pieces of the same kind of perception leaves you with a
collection of perceptions of the next lower (or at least A lower) level.
To control perceptions of any level, it is necessary to VARY perceptions
of the next lower level.
At the time you wrote that paragraph, your attention was momentarily
working from the sixth level of perception, so naturally the whole world
seemed to be made of relationships. In fact, the more you look the more
relationships there are: the distance from your nose to this "a" on your
screen, for example, which I'll bet you hadn't realized was there. But
all I have to do is ask a few questions, and you'll start perceiving at
a different level. For example, is the distance from your nose to the
"a" an example of a particular _kind_ of relationship? How about
"spatial relationships?" Then you could think of other kinds: temporal
relationships, for example, or size or speed relationships, or intensity
relationships (the paper is not as bright as the light bulb). What
you're doing now is perceiving _categories_ of relationships, and
"categories" is the 7th level of perception in my model. You can also
perceive categories of the other levels of perceptions: categories of
spatial configurations, for example, to which we give names like
"square" and "circle" and "blob." That is, we customarily use visual
configurations like the letters b-l-o-b scrunched together as equivalent
to certain category perceptions, and thus create symbols for categories.
Still convinced that all perceptions are of relationships?
Now, what do sensory nerves actually register? Intensity. Nothing else.
One sensory ending can only fire at a certain rate that corresponds to
the intensity of stimulation. So the entire world, as far as any systems
further inside the nervous system are concerned, is made of a set of
intensity signals.
When certain intensity signals are routed to a common place and added
together with specific weightings, the result is a signal that we know
as a sensation, like color, or taste, or smell, or timbre. To fast-
forward a bit, it isn't for several more levels that the functions being
computed yield signals that can stand for positions in an objective
space, corrected for size, parallax, and viewpoint. At the second level
you can say "I feel warmth". But not until the sixth level can you say
"I feel a warm spot on the back of my hand."
···
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(your note to Paul George):
The issue with PCT as I understand it IS NOT the representation of the
structure, the possible levels and hierarchy. The issue is closed loop
negative feedback control system is the only known mode of operation of
living systems that explains what is actually seen.
There's no way to separate these issues. A conceptually neat model that
violates known neuroanatomy would be just as useless as a
neuranatomically correct model that blew up when you tried to run it.
What we must have is a workable model that recreates the behavior we
actually observe, and fits what we know of the nervous system and
muscles as well -- and works in the world described by physics and
chemistry. This is supposed to be a model of a real system, not an
intellectual exercise.
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RE: boundaries.
The basic rule is: put yourself inside the system you're talking about.
If you're the dog, your perceptual field contains a cat moving
unpredictably around, as well as your nose and paws -- but no dog. If
you're the cat, there's a dog in your perceptual field along with your
nose and paws, but no cat. As an external observer, you are looking out
of the wrong boundary. You can see a cat AND a dog, and the noses you
see (other than your own) are seen in profile or in front, not from
behind them. That's the incorrect view for understanding either system.
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