[From Bill Powers (2001.02.13.0835 MST)]
Bruce Gregory (2001.0212.1642)--
Again, I find the term "verbal levels"
unclear. Aren't all levels potentially verbal? For example, "I see a red
patch." Is this not a verbal report of a rather low-level perception?
I don't claim to be clear about this subject, either. But as I think of
"the verbal levels," they are the levels where symbols are manipulated
rather than the analog perceptions for which they stand. Symbols, sequences
of symbols (statements), and logical or at least rule-driven manipulations
of statements make up what I think of as the verbal levels. Obviously, I'm
using these levels right now, the symbols being configurations on a screen
rather than sound-configurations. That's a long way from understanding
language and thought, of course.
It's quite possible to control perceptions (at lower levels) without
involving the verbal systems. You can match a red patch to paint chips by
controlling for a lack of change in color perception as you switch your
gaze from one location to another. You don't have to be saying to yourself,
"That's a red patch, and now this is another red patch."
In fact, you could never match one color sample to another using the verbal
systems. The term "red" refers to a _category_ of sensations, so all sorts
of samples would be called "red" even if we can see they don't match. Also,
you can match color samples even if you don't know the name of the color.
This applies to all kinds of perceptions. Any time continuous control is
involved, you have to use the lower-level control systems and leave the
verbal levels out of it. That's because we don't have nearly enough words
to distinguish all the states of the analog perceptions that we must
discriminate to achieve smooth control.
Why is the category level any more verbal than the relationship level?
To my mind, it's because relationships are perceived and controlled in an
analog fashion. We can name certain relationships, like "above" and "below"
and "on", but that isn't sufficient to give smooth control during, say, a
tracking task. We aren't controlling those three words when we track; we're
controlling a perceived continuum of relative distances. We pick out some
crudely defined situations and attach words to them, but a word like
"above" doesn't tell us enough quantitatively to allow good control.
More generally, verbal systems use symbols, which are discrete rather than
continuously variable. I have proposed that symbols are created by
including them in the same class with the things symbolized: that is, the
symbol "dog" (as both a sound and a visual configuration) is arbitrarily
made a member of the perceptual class that also includes such
configurations as Great Danes, Chihuahuas, huskies, terriers, and so forth.
Any example of those breeds, plus the auditory or visual word, is reported
at the category level as the same perceptual signal. Note that this creates
the same effect as memory association, but without invoking that mechanism
(whatever it is).
A judge at a dog-show can't be using just the verbal levels to distinguish
among dogs, even within a breed. Instead, dogs are judged on a continuous
scale of perceptions, on which one dog can be closer than another to the
ideal representative of the breed or type (as the judge sees it). The judge
looks back and forth between the best two terriers, and finally picks the
one that seems the most terrier-like to the judge. All that is nonverbal.
Exactly how would you [Rick] propose to distinguish
between an awareness problem and a verbalization problem. For example, if I
say I can't see anything, but I am manifesting blind sight, how do we know
if the problem is awareness or verbalization?
I think the distinction would be more properly that between visualization
and verbalization. Is it that the person can't see, or that the person
can't describe in words what is seen? Awareness, I think, is much harder to
establish, since either visual control or verbalization can, in principle,
take place without awareness.
If you want to find a PCT explanation, the test would be in whether you can
control something the state of which can't be perceived without sight. If
you control, say, the position of a vase on a table so it's exactly between
two other vases, then the only known way to do this is to be able to see
the three vases. If you succeed in this control task, then inside you there
must be a control system using visual information. If, at the same time a
person does this, that person claims not to be able to see the vases, then
we have to conclude that the person's conscious (or at least verbal) self
is cut off, in some way, from the control systems in the brain that are
using the visual information at a lower level. Of course we can investigate
physiologically to see if the visual systems (retina, optic nerve, midbrain
structures) are intact; in the cases that are most interesting, I believe
they usually are.
So we can establish the existence of visual perceptions by showing control
of variables that can be observed only by using vision. If the person still
seems unable to describe anything visual, we must then suspect that there
is something wrong with the
symbolizing/categorizing/sequencing/rule-following systems. Or, perhaps,
something is preventing awareness from receiving information from the lower
system -- although anything having to do with awareness is pretty hard to
investigate objectively.
In another post, you propose that awareness may be able to get information
without relying on the neural perceptual systems. I think that proposal is
far harder to believe than the explanation I offer (of course, otherwise I
would offer the same explanation as yours). In all cases where people claim
to get information about the world without using the senses, I feel that
almost any alternative explanation would be more believable; an "ordinary"
explanation would have to be pretty incredible to be more incredible than
positing an information channel that nobody has ever been able to
demonstrate. I think that's a pretty good rule of thumb to follow (I didn't
invent it). For example, which is more incredible: that 100 people saw a
space ship from another planet hovering in the sky exactly where Venus
should have been, but wasn't, or that 100 people saw Venus and were
ignorant of what they were looking at? I'll take the latter any day. It
doesn't take much to convince me that 100 people, or for that matter 1000,
can be totally and simultaneously mistaken about what they're looking at.
"Blindsight," I assume, does not involve any actual knowledge about the
world that does not use the senses. I would like to see the experiments
done with the person actually blindfolded (something an experimenter might
not think of doing to someone who claims to be blind). The contrary
postulate goes beyond the bounds of my credulity.
Best,
Bill P.