[From Fred Nickols (2005.02.14.0723 EST)] --
I have a question about a comment Bill P made in the Prediction thread (see
below):
>That is what Flach said, and what Forrester and Eberlein said, too.
>I disagree with that idea. I think that reference signals are inside
>the head, not outside in the environment.
I've got some experience working with the SD folks, including Eberlein and
others, including a fellow John Sterman said was the best SD modeler of all.
Those folks are usually grappling with what I call "contrived" systems
(e.g., the dynamics of a business or perhaps some portion of it (e.g., a
process). In contrived systems, the "reference signals" are definitely in
the environment (although they doubtless started out in someone's head).
PCT folks are dealing with what I call "natural" systems (e.g, people). In
natural systems, the reference signals are definitely in the head (and
perhaps in other parts of the body as well. Do muscles have "memory"?)
In any event, as I've watched the PCT/SD dialogue, it's struck me that the
two tackle very different kinds of systems. The control mechanism in a
contrived (i.e., man-made) system is likely to be different from the control
mechanism in a natural system.
More to the point, the SD view of things seems to work for the systems with
which they deal but wouldn't work for individual human beings. I don't know
if the PCT view would work for the same kinds of systems that SD folks
tackle.
Just a thought...
Regards,
Fred Nickols
nickols@att.net