From [Marc Abrams (2005.02.10.1402)]
In a message dated 2/10/2005 1:37:22 P.M. Eastern Standard Time, powers_w@FRONTIER.NET writes:
[From Bill Powers (2005.02.10.0908 MST)]
** 1. Propagation of PCT** Bruce Gregory, through his studies of teaching science, gave us an answer to the first question. People are able to learn new ideas, but first they have to unlearn what they think they already know.
Unlearn? What is that, a mind wipe?
Their intellectual capital is already invested, and you have to persuade them to cash it in and spend it on something else.
You are right on target here, and you have done a woeful job of doing this and understanding what needs to be done.
Maybe your arguments are just not convincing and maybe they are just not worth knowing.
Marc Abrams is, through his commendable effort to get a belated education, reading many ideas that have been developed without benefit of control theory,
Newton developed the calculus without the benefit of control theory, I guess we should discard that as junk as well
and like any enthusiastic student exposed to ideas for the first time, he takes everything he finds in print as true, if written with the trappings of authority.
Even PCT, and that was my BIGGEST mistake.
In other words, he is learning from those whose investment would be lost if control theory proved to be important,
Really??? Weick? Argyris? Forrester? Llinas? Which of these would LOSE their credibility? And for what reasons?
You don’t know, or understand the work of these men. You speak as you usually do, from IGNORANCE, and a lack of understanding
and he keeps wondering, “Gee, how could Powers have missed all this wonderful stuff?”
Real easy. Powers never knew about it. Your 74 or so cites in B:CP is one of the WEAKEST referenced books I have looked at. I have read 3rd classs journals (Some of which Marken is familiar with) with articles that had more cites then B:CP.
Your introspection might be wonderful, but others have done some wonderful work as well, and you should try reading a book every now and again, and then pass it on to Rick. something post 1940 preferably.
Powers surely missed some of it, but not much.
What did you miss besides the autonomic nervous system in your first go around?
Powers simply didn’t believe as much of it as Abrams did and does. Abrams is not yet equipped with enough knowledge and experience to be skeptical.
How would you know what my ideas are based on? How do you know what I believe and don’t believe in? And how do you know what I am, and am not equipped with?
You don’t have a clue.
And a belated education? Hardly pal, Your mantra is getting old Billy boy. I’ve been educating myself for the past 25 years and CONTINUE to do so. What’s your excuse?
The real big difference between you and I Bill , is that I understand how ignorant I really am and try to improve on it. You revel in yours, and carry it around as some form of honor.
**2. The P in PCT.**This is directly related to the second question: why the “P” in “PCT”? The answer is very simple: because to far too many people, the word “control” means a myriad of processes that have nothing to do with negative feedback control,
NONSENSE. You really should take a look at the literature. I know you have a hard time reading, but you might want to stop making yourself look like a jackass.
**3. System Dynamics and PCT.**Marc’s ignorance ***[Ad Hominem Attack]***shows up most clearly when he talks about “System Dynamics” as if it is something separate from the kind of modeling that has gone on in science and engineering
NO Bill, My point which you simply refuse to acknowledge is that a negative feedback loop IS a PCT loop.
since they started. Engineers and scientists deal with system dynamics (no capital letters) by setting up differential equations and solving them, or more commonly in practical situations by simulating them on some kind of analog computer. I learned how to do this in 1953 and 1954 with a Philbrick analog computer, and learned a great deal about simulating control systems that way. I even used the analog computer as a component in a control system for making isodose traces for a cobalt-60 radiation therapy machine. so what I learned was practical as well as theoretical.
What does ANY of this have to do with my point about PCT and SD?
Martin, you are perfectly right in saying that System Dynamics models do not often (if they ever do) deal with control. Those I have seen do not contain any human controlling agents;
A false claim. In fact any legit SD model is made FROM time series data and the reason is simple.
The entire purpose of an accurate SD model is to mimic the time series data.
The model behavior is compared to the existing empirical data to confirm the validity of the model. Adjustments are made to the model until the model produces the expected time series data.
PCT should be so lucky with something other then a tracking task.
they deal only with large systems which interact according to very arbitrary assumptions, through parameters that are not measured, but are guessed at.
Another false claim. SD models contain a variety of types of data
Actually some of them must be doing it right, because Bob Eberlein’s Vensim contains facilities for using data from the real world and matching models against real performance by adjusting assumed parameters, the essence of the analog computing method of system analysis. I just haven’t seen any examples of that.
Hey, maybe you should first understand how they build their models. At least the legitimate ones.
Maybe you should come out of the 1950’s and into the year 2005, if it isn’t to uncomfortable for you.
The most serious lack in SD (the movement) is the lack of a human controller with goals and means of making perceptions match them.
Why is this a problem? Because Bob sent you a test problem?
Bob Eberlein sent me a test problem having to do with balancing inspection with production to minimize the costs of dealing with returned products. I worked up a model with several managers in it, having the appropriate goals and means of acting to achieve them, which accomplished the objectives very quickly. Since Bob had said he was thinking about how to introduce agents into SD models (this was about 40 years after SD came into existence), I thought he would be happy to see an example of how this could be done. I never heard another word from him on the subject – not even “good model”. Or “terrible model,” for that matter. Nothing.
I wonder why? Maybe he felt the model did not represent anything better then what he already had. It might have been worth a follow-up call to find out.
I asked Bob about your meeting and he said the mathematics were IDENTICAL. What was different was in the details and that for his modeling purposes those details were not significant.
When I met with Forrester. Eberlein, and George Richardson a few years ago (Marc Abrams set up the meeting), I showed them my tracking model. Forrester and Eberlein couldn’t understand why I put the reference signal inside the controller instead of saying it was the target position on the screen, and why I didn’t say that the controlling person was sensing the error signal. You may recall this same problem arising in the discussions between John Flach and me. I was violating the “engineering psychology” model that had been standard since the early 1950s. Richardson, who has a very clear understanding of PCT, tried to explain the reason to them, to no avail. I kept my mouth pretty much shut, not wanting to be the outsider telling them their business. It was pretty clear that neither Forrester nor Eberlein had any idea of how to model a controlling agent. That would explain the lack of such agents in SD models, of course.
And Herein lies at least one of the issues for PCT folks. The PCT model does NOT produce results that are in any way different then a negative feedback NON perceptual input model. It seems a negative feedback loop is a negative feedback loop. With or without the perceptual input.
Tough luck.
I certainly think so.