Re: Images Vs. Symbols

From: HARNAD Stevan (
Date: Fri Mar 15 1996 - 20:14:03 GMT

> From: "Bollons Nicholas" <>
> Date: Thu, 14 Mar 1996 11:42:01 GMT
> A couple of things that I need to illuminate upon in my questioning
> of mental imagery. I do understand the difference between morse code
> and a propositional language. May be 'logical language' would have
> been a better word to use. But it was this form of logic language using
> computational symbol manipulation that I thought would be a better in
> explaining the process of mental functioning rather than a binary
> system. Which I reckon is too simplistic in dealing with the enormous amount
> of input.

It's not the DIFFERENCES between these codes that is relevant, it's the
similarity: The point is that morse code IS a propositional language,
once you spell out all the words. All these symbolic codes are
intertranslatable. And you might as well have used binary symbols for
all of them (i.e., just 0 and 1), because the shapes of the symbols
don't matter, they're arbitrary.

All languages are "propositional" in that they can all make statements
that are true or false. I'm not sure what you mean by "logical
language," but all the symbol codes worth using are, among other
things, logical (they don't contradict themselves and some symbol
strings are implied by others).

> Secondly, my idea for C.P.U projection was that nearly all areas of
> the brain are inter-linked to each other and do not operate
> separately.

First of all, what is your evidence that this is so? And if it were so,
what would follow from it?

> I also understand that during visual imaging : the picture
> is mapped to areas within the cortex in what (I think ?) is spatial
> relation to the details of the picture. This also seems to occur in mental
> imaging ; when the same areas are active as the subject is asked to
> "think" of an object/something (maybe 'think' is also the wrong
> word). This image mapping is retinotopic mapping.

You are right about what retinotopic mapping is: Some areas of the brain
are just analog copies of the shadow cast by objects on the retina. They
are shadows of shadows. It is these areas that light up when you have an
image, but (this is important) the brain image does not look like the
mental image (or the object): It is merely that the areas that light up
are the same ones that are known to be retinotopically mapped. Besides,
as I said, an analog copy can "projected" onto a different dimension,
as long as it preserves the geography: as I said in lecture, the
"shadow" of a sound need not be another sound (though it could be). It
could also be another dimension, like, say, length, onto which the
sound is "mapped," point for point, a higher sound becoming a longer
length and a lower sound becoming a shorter length. Re-read the
skywriting about the cochlea.

> But does P.E.T imaging only identify the retinotopic areas or is there
> activation in other parts of the brain ? I.e. is the mapped area the only
> one active during imaging or is say another one (I'm not just
> considering higher cortical functioning) also working at this point in time.
> I doubt it ? But that was the point that I was trying to convey,
> As the Kosslyn article only talked about the retinotopic mapped
> areas being active and nothing else.

Yes, other areas are active too. See the Posner & Raichle article.

> P.S If there is no Homunculus. Does he have some sort of metaphorical
> brother called the 'Unconscious Homunculus' ? 'The little
> unconscious man in our head' (and I do not mean that he is
> asleep) dealing with the 'Freudian' / unconscious motives for
> behaviour

Good question. Some people think so, but the idea of an unconscious mind
that is just like a conscious mind, except not conscious, is rather like
saying it is just like a mind, but not a mind!

We know we have minds. To have a mind is to be conscious, to have
feelings, experiences. If there were no experiences going on, there
would be no mind there. So what does it mean to say we have yet ANOTHER
"mind," except that one is unconscious, i.e., has no feelings, no

Two answers are possible: that other mind does have feelings, but they are
unconscious feelings. That, I'm afraid, makes no sense; it's like saying
"unfelt feelings." That's just a word-game or a word-mistake. Feelings
are only feelings if they are felt.

The other possibility is that my "unconscious mind" does have feelings,
does feel, except that I don't feel what it feels: IT feels it. But
then it WOULD be a conscious mind, only not mine! It would be the mind
of someone else living in my head. (Now multiple personality -- more than
one mind co-existing in the same head -- IS said to be possible, but
if it exists, it's rare and it's strange, and certainly not what people
mean when they speak of the unconscious mind.)

If you want to know what I think: Introspecting about what's going on in
your own mind doesn't tell you much; that means that most of what's
going on in your head is unconscious. Usually, we take it for granted
that what we think and do comes from US. But challenges like "How did
you recognise that face? How did you remember that name? How did you
know that?" force us to admit that we have no idea where our thoughts and
actions really come from. So we invent another mind, not the conscious
one that has no idea where its ideas and actions come from, but another
one, very much like it, except unconscious, and IT's the one it all came

You're right that that's homuncular, in that it also doesn't explain
anything, but just attributes it to another mind in your head. But that
other mind, unlike the conscious one looking at the mental image, isn't
even conscious! So why call it a mind at all? Whatever it is is indeed
responsible for what we think and do, but it isn't a mind, it's just
mindless processes (yet to be identified, possibly computational) that
do the work and then hand us the results on a platter.

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