Fifty ways..best yet; no PCT instructional designs exist

[From Chris Cherpas (970129.1833 PT)]
[re Bill Powers (970129.0430 MST)]

BP's post, for me, is by far the most convincing I've seen in the
PCT versus MCT debate; by george, I think he's got it!

BP:

This immunity to changes in both the environment and the output function is
what makes a closed-loop control system such a natural model of living
control systems. Living systems are not made of precision components; the
response of a muscle to driving signals begins to fall off immediately when
the muscle is used, fifty percent or more after a few minutes of heavy
exercise. Yet the performance in a control task doesn't fall off fifty
percent -- far from it. You may be shaking and weak from fatigue, but you
can still get in your car and drive away without going into the ditch. Yes,
you're adapting to the changed state of the muscles, but you don't NEED to
adapt; that's the whole point. You don't lose control and then gradually get
it back. You never lose control to any large degree. A fifty percent change
in the sensitivity of the output function is trivial, in terms of its effect
on performance. That is strictly because of the closed-loop negative
feedback involved.

In a control system of the MCT type, none of this holds true. If the
sensitivity of the output function dropped by 50 percent, the output actions
would lose strength by 50 percent. It would be entirely up to the adaptive
part of the system to change the internal world-model until control was
restored. To explain the observed lack of effect of an environmental change
on performance, we would then have to assume that the adaptive function was
set to operate very rapidly, on a time-scale of seconds, or even less than a
second. But this would negate the ONLY advantage of the MCT model, because
if it adapts very rapidly, it can't maintain apparent control for any
significant length of time when its input is lost. If you set aside that one
feature of the MCT model, then there are many other ways to put adaptation
into the control system without giving up the enormous advantages of the
closed-loop arrangement.

But I come not only to praise, but to whine...
Now if there was just a single case where someone had designed an
instructional program to teach even a small part of an academic subject
using PCT, I could justify the extra time it would take me to learn PCT
in reasonable depth. As it is, I design instructional programs with a
partial understanding of PCT, but not much hope that I'm really doing it
justice yet. I really hate starting from scratch, but if I ever succeed I
guess I'll just have to claim all the glory for myself. On the other hand
I may just have to accept that PCT only promises educational applications.

Regards,
cc

[From Bill Powers (970129.2030 MST)]

Chris Cherpas (970129.1833 PT)--

I really hate starting from scratch, but if I ever succeed I
guess I'll just have to claim all the glory for myself. On the other
hand I may just have to accept that PCT only promises educational
applications.

How are there ever going to be any educational applications if nobody who is
professional competent in education develops them? Why does everybody want
me to do their work for them?

Best,

Bill P.

ยทยทยท

Regards,
cc