[From Bruce Abbott (941228.1255 EST)]
Rick Marken (941227.1115) --
Rick, I've already replied to Bill on the issues you raise concerning my
"evolution" model, so I won't repeat myself here. But I would like to raise
another issue, which is why it is that you were not able to grasp the
essential nature of the model by reading the program's code. It's really not
difficult--all the necessary information about what the program is doing is
contained in the (very short) main loop, and the variables have been given
names that make it clear what they represent.
This troubles me, because the program is supposed to be the arbiter of any
disputes as to what the model actually is--it's supposed to short-circuit
these endless verbal tangles. You should have been able to examine the code
and tell me whether the model provides an analog of the reorganization system-
-as I said it did--even if you disagreed with my description of the model as
selection by consequences. I can understand getting lost in the ECOLI4a code-
-its logic is by no means easy to comprehend--but the evolution program's
logic is simple.
What happened instead is that you started out by agreeing that the model was
an example of selection BY consequences and then arguing with me that it could
NOT be an analog of the reorganization system, because, you said, selection BY
consequences cannot result in control, and reorganization is a control system.
If even the explicit presentation of program code cannot settle the question
of what a model actually represents, why bother with it at all? Why not just
default to verbal arguments and let it go at that?
I agree with your description (and diagram) of the evolution model but--and I
have to emphasize this again--I think it's just a matter of what you wish to
emphasize about the operation of the model. For a given reference, what
happens next depends on the outcome of the previous round of control. In the
comparator function, the reference AND the perceptual input jointly determine
the error. Thus, for a given reference, the joint effect of output and
environment on the perceptual signal determine what happens next; for a given
perceptual input, the value of the reference does so. To understand why the
model behaves as it does, you must know both.
At least I now have your agreement that it the model does encode a form of
reorganization system. With slight modification it could be converted to a
model in which a single organism reorganizes its own system parameters when
the lower-level system fails to achieve control over its perceptual variable.
The next question is, would such a system usually achieve control before the
organism expired (i.e., is the system efficient enough to be practical?).
One other point--a question, really. You have stated that the ECOLI4a model
does not learn because it only changes the parameters of an existing control
system, rather than creating a new one. By your definition, the kind of
reorganization proposed in the evolution model would not qualify as learning
either, for the same reason--it just "finds" workable parameters for an
existing control system. Do you agree? If so, how would reorganization have
to differ for it to qualify as a form of learning?
P.S. I'd appreciate a copy of the "blind men" paper, which you offered to
send on request. I want to read about the blind man who says "An elephant is
like a set of perceptual control systems...". (;->