No, a symbol is simply anything abstract that stands for an object - word
sounds, alphabetic words, numbers, logical variables etc. The earliest
proto-symbols may well have been emotions.
My point is that Harnad clearly talks of two intermediate visual/sensory
levels of processing - the iconic and still-more-schematic "categorical
representations" - neither of which I can remember seeing in the ideas of
anyone here for their AGI's. But I may have forgotten something/someone.
Have I?
Richard:
You may want to check out the background material on this issue. Harnad
invented the idea that there is a 'symbol grounding problem', so that is
why I quoted him. His usage of the word 'symbol' is the one that is
widespread in cognitive science, but it appears that you are missing this,
and instead interpreting the word 'symbol' to be one of your own
idiosyncratic meanings. You can see this most clearly when you write that
the symbols are things like "H-O-R-S-E" and "C-A-T" etc .... those look
like strings of letters, so if you think that a symbol, by definition,
must involve a string of letters (or phonemes), then you are
misunderstanding Harnad's (and everyone else's) meaning of by rather a
wide margin. That probably explains your puzzlement in this case.
Richard Loosemore
Mike Tintner wrote:
I'm not quite sure why Richard would want to quote Harnad. Harnad's idea
of how the brain works depends on it first processing our immediate
sensory images as "iconic representations" - not 1m miles from Lakoff's
image schemas. He sees the brain as first developing some kind of horse
graphics, for the horses we see,
Then there is an additional and very confusing level of "categorical
representations" which pick out the "invariant features" of horses - and
are still nonsymbolic. But Harnad doesn't give any examples of what
these features are. They are necessary he claims to be able to
distinguish between horses and similar animals.
(If anyone has further light to shed here, I'd be v. interested).
And only after those two levels of processing does the brain come to
symbols - to "H-O-R-S-E" and "C-A-T" etc - although, of course, if you're
thinking evolutionarily, it's arguable that the brain doesn't actually
need these symbols at all -our ancestors survived happily without
language.
So Harnad depicts symbols as not so much simply grounded as deeply rooted
in a tree of imagistic processing - and I'm not aware of any AGI-er using
imagistic processing (or have I got someone, like Ben, wrong?)
Richard:
Derek Zahn wrote:
Richard Loosemore:
> My god, Mark: I had to listen to people having a general discussion
of
> "grounding" (the supposed them of that workshop) without a single
person
> showing the slightest sign that they had more than an amateur's
> perspective on what that concept actually means.
I was not at that workshop and am no expert on that topic, though I
have seen the word used in several different ways. Could you point at
a book or article that does explain the concept or at least use it
heavily in a correct way? I would like to improve my understanding of
the meaning of the "grounding" concept.
Note: sometimes written words do not convey intensions very well --
I am not being sarcastic, I am asking for information to help improve
the quality of discussion that you have found lacking in the past.
I still think it is best to go back to Stevan Harnad's two main papers
on the topic. He originated the issue, then revisited it with some
frustration when people starting diverging it to mean anything under the
sun.
So:
http://users.ecs.soton.ac.uk/harnad/Papers/Harnad/harnad90.sgproblem.html
and
http://users.ecs.soton.ac.uk/harnad/Papers/Harnad/harnad93.cogsci.html
are both useful.
I do not completely concur with Harnad, but I certainly agree with him
that there is a real issue here.
However......
The core confusion about the SGP is so basic that you will find it
difficult to locate one source that explains it. Here it is in Harnad's
own words (from the second paper above):
"The goal of symbol grounding is not to guarantee uniqueness but to
ensure that the connection between the symbols and the objects they are
systematically interpretable as being about does not depend exclusively
on an interpretation projected onto the symbols by an interpreter
outside the system."
The crucial part is to guarantee that the meaning of the symbols does
not depend on interpreter-applied meanings. This is a subtle issue,
because the interpreter (i.e. the programmer or system designer) can
insert their own interpretations on the symbols in all sorts of ways.
For example, they can grab a symbol and label it "cat" (this being the
most egregiouse example of failure to ground), or they can stick
parameters into all of the symbols and insist that the parameter "means"
something like the "probability that this is true, or real". If the
programmer does anything to interpret the meaning of system components,
then there is at least a DANGER that the symbol system has been
compromised, and is therefore not grounded.
You see, when a programmer makes some kind of design choice, they very
often insert some *implicit* interpretation of what symbols mean. But
then, if that same programmer goes to the trouble of connecting that AGI
to some mechanisms that build and use symbols, then the build-and-use
mechanisms will also *implictly* impose a meaning on those symbols.
under almost all circumstances (and especially if there is ANY SUSPICION
OF COMPLEXITY IN THE SYSTEM), these two sets of implicit meanings will
diverge. There is simply no reason why they should stay in sync with
one another, so they don't. If there is any conflict, then the
grounding of the system has been compromised. Ideally, the programmer
gets out of the way completely and leaves it to the system to ground its
own symbols. (That, of course, almost never happens).
But now, what happens in practice when people talk about symbol
grounding? They usually take an extremely naive approach and assume that
IF a system has some kind of connection to the outside world THEN it
must have grounded symbols! This is crazy. The fact is that having an
outside connection is a good first step to getting grounded symbols, but
it does not even begin to address all the ways that the grounding can
get compromised. Yet, people who do not really understand the idea of
grounding, but know that it is a cool buzzword, tend to use the buzzword
as if it just meant "connecting your AGI to the outside world".
This certainly happens on this list, but it was also present in many of
the AGI 2006 papers.
At the 2006 workshop (whose theme was something like "Grounding symbols
in the real world") I became more and more frustrated to see that
grounding was being mentioned in this trivial way, and that nobody was
stopping to point out that this was just downright wrong. Remember,
this was supposed to be the *theme* of the workshop! How can that be
the theme, and then everyone (including the workshop convener) not
understand that this usage was trivial and worthless?
This idiotic situation went on and on until the penultimate session of
the workshop, at which point I remember that I stood up in the discssion
period just before the final coffee break and explained that we were not
using "grounding" in a sensible way. Since I had only a few moments to
talk I said that I was looking forward to the roundtable discussion
after the break, because the topic of that roundtable was "Symbol
Grounding", so we would have an opportunity to get down to some real
meat and sort the problem out.
Then, when we came back from the break, Ben Goertzel announced that the
roundtable on symbol grounding was cancelled, to make room for some
other discussion on a topic like "the future of AGI", or some such. I
was outraged by this. The subsequent discussion was a pathetic waste of
time, during which we just listened to a bunch of people making vacuous
speculations and jokes about artificial intelligence.
In the end, I decided that the reason this happened was that when the
workshop was being planned, the title was chosen in ignorance. That, in
fact, Ben never even intended to talk about the real issue of grounding
symbols, but just needed a plausible-sounding theme-buzzword, and so he
just intended the workshop to be about a meaningless concept like
connecting AGI systems to the real world.
I hope that clarifies the issue a little. I have also written about the
grounding issue on these lists, but I don't remember where those posts
are.
Richard Loosemore
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