[From Wayne Hershberger] (23 Dec 92 10:38:54 CST)
In a reply to Gary Cziko's post on VOR:
I believe Tom Bourbon's recent post regarding the control of error
is really an essay concerning feedforward. Feedforward can be
thought of as endogenous disturbances to reference signals, error
signals, or output (as I argued in my ABS article in the special
issue edited by Rick). You might want to reread Tom's posts with
that in mind.
Wayne, I tried to follow the suggestion you made to Gary, but it
doesn't work. Every time I reread my post on control of error, I
see a post on control of error, with illustrations of what happens
when various signals in a PCT model are disturbed, one at a time.
I do not see an essay on feedforward.
Feedforward can be thought of as many things other than the
possibility you describe here and in your article in ABS. I don't
recall ever seeing anyone else interpret the word "feedforward" in
the same manner as you. I still have problems with your
interpretation in ABS (American Behavioral Scientist) of Pavlovian
conditioning as an instance of feedforward.
Perhaps Gary does not need help with this, but I need some
additional information from you if I am to understand why my post
was really an essay on feedforward. Could you begin with your
definition of feedforward?
Tom Bourbon
Your post regarding the disturbance of error signals is germane to
the discussion Andy and I were having in Durango about Pavlovian
conditioning. Has he read your post?
Andy (Papanicolaou) has been out of town for the past two weeks.
A printout of my post is on his desk, where it will soon be joined
by copy of your post. I will let you know what he thinks.
ยทยทยท
From: Tom Bourbon (921223 13:20 CST)
********************************************
Rick Marken and Martin Taylor (several posts)
Thanks to both of you for sharing your previously off-line
discussion about control of error.
********************************************
[Martin Taylor 921222 18:15]
(Bill Powers 921222.0800)
Bill:
As long as the list of people actually
devising and carrying out experiments and modeling is limited to
Rick Marken, Tom Bourbon, and me, the queue of possible
experiments with HPCT is going to grow while the actual work done
trudges along at a slow pace.When I last looked, there were 132 subscribers to this list.
Permit me a moment of impatience: when are some of you people
going to get out of your armchairs?
Martin:
Well, we are trying the Little Baby experiments, and are doing
preliminary work for Genetic Algorithm experiments, both to study
reorganization. Does that count?
I haven't seen a reply to this from Bill, but it certainly should
count. Just don't tell me how many people other than Chris Love
are working on the programs -- Chris alone pushes me to a distant
fourth on a list of four!
********************************************
Martin to Bill:
I'm working on a more considered presentation of the information-
theory stuff, as requested. But it isn't going to be immediate.
To tighten it up and make it didactically useful is going to take
work, especially since I have to go back to basics, as these
questions suggest. It could be that I will make up some document
to be deposited with Bill Silvert or to be circulated on paper
(lots of pictures required).
and to
(Tom Bourbon 921222 10:10)
Yes, I started working on it after yesterday's postings. See
above. I would very much like to see it actually run as a model of
the type you like, but as a practical matter I spend much more
time on CSG matters than I should (as well as having contractors
work on PCT-related issues). I am not a strong programmer, though
I sometimes find it fun. Quite probably I will write the document
that Bill asks for, and then see whether it opens fruitful lines
of discussion that might induce me or someone else to do the
actual generative modelling. Producing the document has obvious
benefits for me, to make the ideas more precise, rather than
intuitive, as in the posting to you. And it would seem necessary
if the ideas are to be propagated (assuming that they have value).
It seems obvious that your intuitions concerning links between
information theory and PCT are strong. If the sometimes heated
exchanges on that topic here on csg-l result in your clarifying
those ideas for yourself, then we all will share in the benefits
you envision, whatever the outcome of your efforts.
Tom:
I believe a major question that is unresolved for some of the
modelers is whether you would necessarily arrive at the PCT
structure. Couldn't you just as easily arrive at other,
sometimes implausible, structures? I have seen information
theory used to justify or explain many varieties of theory in
behavioral and cognitive science. Why should one person arrive
at a PCT structure, when so many others did not? I am not saying
that you will not, just that I do not see the necessity that you
will.
Martin:
You are quite right about the (mis)uses to which information
theory has been put, and this paragraph will make me look much
harder at my assumptions than I otherwise might have done. I do
not want to provide a circular argument "PCT, therefore PCT."
What I believe should come out is "chaotic world, therefore PCT."
If that is what comes out, you need no longer wonder whether your
ideas should be propagated, or whether they have value.
Until later,
Tom Bourbon e-mail:
Magnetoencephalography Laboratory TBOURBON@UTMBEACH.BITNET
Division of Neurosurgery, E-17 TBOURBON@BEACH.UTMB.EDU
University of Texas Medical Branch PHONE (409) 763-6325
Galveston, TX 77550 USA FAX (409) 762-9961