[Martin Taylor 2016.09.26.12.45]
[From Rick Marken (2016.09.25.1750)]
Rupert Young (2016.09.24 1700)
The problem with that is that it is hard to prove a negative by just
modelling. You may fail to show that PCT can explain the situation
simply because you are modelling control of the wrong variable, or
have not found suitable ranges of parameter values. Failure doesn’t
mean PCT can’t explain, even though success shows it can. In most
sciences, modelling and theory go hand in hand. PCT science should
BE a science. Theory CAN show why certain sets of assumptions cannot
explain some things, and need to be expanded or amended.
A new definition of "perfectly"? And of "every" at the same time?
Huh? What version of CSGnet do you get in your alternate Universe?
The challenge has never been to PCT as a theory in its present form.
The challenge is to find the correct controlled variable(s) and
parameter values for a working model that produces the power law
appropriate to the situations under which it is observed. Nobody has
done that yet – or if they have, they haven’t posted it. That
doesn’t mean PCT needs to be changed.
Look up the definition of "chutzpa" in the Random House dictionary.
I think this paragraph is a good example, given the multitude of
ways that it has been shown that the model is not even a model of
the situation, and that the maths behind the analysis is wrong
anyway. You may have had the right to be astonished the first time
Alex showed you how it was wrong, but not over the subsequent months
of being shown in ever varying ways and levels of detail how wrong
it was.
Look, modelling is great. When used effectively with theory, it's
even better. But a model that is supposed to explain an observation
ought to be at least a little like the situation in which the
observation is made. Rick’s “model” that “accounts for the
power-law” phenomenon isn’t.
Rick's model is of a 2D tracking task, like chasing a butterfly over
an open field. How fast the butterfly goes determines how fast and
where you go (assuming you aren’t intending to end the chase by
catching it). If Rick’s “butterfly” followed the power law relation
between speed and path curvature, and his tracker was good at its
job, its tracker object (a.k.a. “cursor”) also had to follow the
same power law, didn’t it? I don’t think anyone used those words
yet, but wouldn’t it be perfectly fair to call that a “put-up job”?
The problem at hand is more like "Here's a road. How fast will you
drive around the different curves you see on the map (or that you
see before you)?" Or, “Here’s a drawing. How fast will you go over
its parts when you trace it accurately with a pencil?” That’s not a
bit like chasing a butterfly to see where and how fast it goes.
Any model of the actual task has to take as input an entire curving
line, not some point that moves along the curve. The curve could be
a closed figure such as an ellipse. The line could be input as
disturbance or as reference. The model has to control perceptions so
that something moves, and so that the moving object stays close to
the input curving line when it does move. That’s a minimum
requirement for a working model of the situation.
And who is most recently responsible for that? Might it possibly be
someone who consistently refuses every attempt over a period of
months to counter scientific criticisms of a pet theory?
You could help bring CSGnet back to "scientificity" by creating a
model that meets the minimum requirements for a model that might
explain the power law. If it’s a good model, it will generate 1/3,
1/4, and no power law at all by changing the value of one parameter,
or maybe two. You are a good modeller, and to solve this problem
would be a feather in your cap.
Martin
···
AGM:
Indeed. I am interested in the implications of
the PCT asymmetry where P could stand for
Procrustean, namely, do we shrink the genius
of Maturana or are we willing to be heretic
enough to conceive an extension of PCT…?
RY: Like any theory PCT is open to revision or
extension. So, if you think something is missing by
all means make a suggestion.
RY: In this instance could you explain: What it is
you are proposing? What do you think is missing from
PCT? How does the proposal fill the hole? What will
the revised theory explain that it didn’t
previously?
RM: Thank you Rupert. This is what has been missing from
discussions of PCT on CSGNet: an explanation of what any
proposed revision or extension of PCT would explain that PCT
does not currently explain. In order to do this you have to
had observed some phenomenon and then show, using modeling,
that PCT in its current form doesn’t explain it.
RM: It's important to understand,
however, that in PCT “modeling” is not just curve fitting;
it’s getting a working instantiation of the model to behave
in the same way as does an organism placed in the same
circumstances. Working PCT models are usually instantiated
as computer programs but now, even better, as robotic
systems.
RM: The PCT approach to modeling is
described in Chapter 2 of B:CP (both editions). It’s an
approach to modeling – and testing models against the
results of experimental test – that drew me to PCT. What
attracted me wasn’t just that PCT seemed like a nice theory
of behavior; it was that every prediction of the theory
could be tested quantitatively against observation; and
every prediction held up perfectly.
...
RM: The modeling approach to
evaluating PCT has been conspicuously missing from
discussions on CSGNet. The power law discussion is the most
recent example. The power law is an observed phenomenon
whose explanation supposedly presents a challenge to the PCT
model in its present form.
But this claim was made without
determining whether a working PCT model, behaving in the
same circumstances as those in which the power law is
observed, could produce the power law. It was simply
asserted that it couldn’t. So when I produced a PCT model of
one example of behavior that results in the power law and
found that the model accounts for the power law, I was
astonished to find that it was dismissed as a “put up job”
or something like that.
RM: So it seems that CSGNet is no
longer (if it ever was) a forum for dealing with PCT
scientifically;