From: Lee Corbin (lcorbin@tsoft.com)
Date: Fri Feb 14 2003 - 18:58:30 MST
Brent writes
> For example lets take your 2D picture
[the presumed part of one's visual cortex where indeed
a pattern has been found that corresponds to the visual
image one is looking at]
> and look at the layer of neurons just in
> front of (closer to the center of the brain)
> than where the scientists found the picture
> of the display. I would argue that this layer
> likely represents the space just in front of
> the monitor.
Well, what is generally supposed is that the
areas closer to the center of the brain---
causally upward from the cruder level of the
sensory input---are where feature recognition
is performed. The edges of a triangle, for
example, are abstracted. This is the first
step along toward meaning taking by the brain.
> (Of course since the space in front of
> the monitor is empty the people observing
> the monkeys brain wouldn't have noticed
> anything even if they were looking for something.)
You stick to your 3D claim, of course, that
there is and must be a 3D faithful representation
right inside the brain. I never have heard of
anyone in my life besides you who thinks so.
> But this is all of lesser importance to the fact that we experience a real 3D
> subjective space. There is some way that our brain represents this subjective
> space, even if it isn’t with actual voxel (3D pixel) neurons in the same 3D
> configuration.
>
> >>>Well, again, the words can mean either thing. It's a
> little bit like the puzzler "do we see airplanes, or
> do we see the photons reflected off the airplanes?"
> I like to say that we see the airplanes, but I know
> what people mean when they say that we see photons.<<<
>
> Precisely. The only thing that sees the airplane is the photons. The only
> thing that sees the photons is the surface of our retina… and so on down the
> causal chain of perception. It is physically impossible for us to be directly
> aware of the airplane the way it SEEMS we do.
I have suspected that you fail to grasp that most intelligent
people---or people who have given sense perception much
thought at all---find this exceedingly elementary. Now,
yes, it's true that when I was eighteen this dawned on
me to the degree that I had an utter conviction that
most people didn't really understand that sense perceptions
come in from the outside and are handled entirely materialistically
by our brains. So I used to try to emphasize this in diagrams
that I would show people.
On the left part of the diagram I would show a circle
denoting someone's head, and then I'd draw their eye,
and show a tree on the right side of the diagram. Then
I'd trace how the light rays would come from the tree
and cross over within the eye to create a representation
in the brain. Just to be cute, I'd show the little tree
upside down inside the brain.
But I have found since then that there seem to be just
two classes of people: (a) those who understand that
already and have no need of such a lecture from me or (b)
those who could not care less about academic discussions.
> Finally all this cause and effect results in a subjectively 3D representation
> of the airplane with a subjective representation of ourselves looking out holes
> in our skulls at it. All of this subjective information being in our brain.
> When we say "we see the airplane" this entire process is what this means. We
> must remember that cause and effect perception only goes one way. It SEEMS
> like we look out of the holes in our skulls through the windows of our eyes to
> see the airplane, but in reality the cause and effect of perception flows in
> the opposite direction. You have to think very carefully not to think
> irrationally about this.
This confirms my impression. You still seem to be in the
grip of this being a profound idea, whereas I'm telling
you that to the people on this list this is entirely
commonplace. I certainly *hope* that people here (and
elsewhere where you encounter people attending to these
issues) that the difference between object and sense-
datum, between appearance and reality, is already very
clear.
Especially those of us who have known this for decades
do not "have to think very carefully not to think
irrationally about this".
> >>>What you need to stress---and you do---
> is that there is some kind of true-to-life model in
> the brain, whereas I think that most people on this
> list believe that the representation of objects in
> the brain is much more subtle, the encoding much, much
> more obscure. <<<
>
> People tend to think this way when they aren’t thinking clearly
> and rationally about how cause and effect perception works.
You are so dead wrong here. I don't know what your problem
is, but to imagine that the authors of innumerable books on
how vision works, brain scientists in general, and the vast
majority of people on this list who do not see it at all the
way you do are suffering from lack of clear thinking or
irrationality is outrageous. Not at all, I dare say! ;-)
> People think that red is something on the airplane and
> they think our brain doesn’t require anything like red
> to represent this.
Oh dear. The ultimate philosophical muddle has just been
raised---nothing is so difficult to discuss as color! But
bravely Lee and Brent sally forth! Ahem. Okay, now you're
probably *not* wrong here, but the way I'd say it comes
out a lot different: I say that there are two ways of
talking about it.
A. "Red paint is on the airplane", or "the airplane is red".
I consider this quite defensible. What the speaker means
is that the airplane now reflects light of the appropriate
wavelength that anyone with normal human color vision will
testify that the airplane now has this property. (And
animals too, but that's harder to describe.)
B. "Wavelengths of certain frequencies are reflected by
the airplane, but its redness occurs only because
one of the three types of cones---the type sensitive
to wavelengths between about 520 and 620 nanometers---
fire and this signal is called "redness" by the higher
level processes of the brain". This is quite defensible
also, and may be preferable in a careful discussion.
> If people would just stop and think carefully about this
> things become very clear, simple and obvious.
You really have to stop deluding yourself about this.
I trust that you have studied a number of books on
how sense perception really works, and may I without
being presumptuous recommend another? "Eye, Brain,
and Vision", by David H. Hubel (a Scientific American
publication), is terrific.
> When this happens you can finally realize what the
> future holds for our minds once we start effing,
> expanding and sharing the conscious experience in
> our brains.
...finally realize...
> Once you realize all this you know how stupid
...how stupid...
> it is to think things like the Turing test will forever
> be the best tool we have to determine how conscious
> another being is and so on. I wish people on this list,
> science fiction writes, and people like Raymond Kurzweil
> and most everyone else would stop being so foolish and
> irrational in this way.
...foolish and irrational...
Well, Brent, aren't you getting a little well-seasoned
for such thoughts? (I do appreciate your candor, however
---many think things like this but are too wary of really
coming out with it.) Surely you're thirty, by now, aren't
you?
(Like we used to say back in the sixties, never trust
anyone under thirty!)
Lee
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