[Martin Taylor 2006.11.11.14.14] (actually it was 11.11.14.14.14 when I started to write the date and time!)
[From Fred Nickols (2006.11.11.1213 EST)] --
What if the controlled quantity or targeted variable isn't some "remote
physical phenomena" but instead refers to some aspect of me? What if the
controlled quantity isn't "out there" but is instead "in here."
In our earlier discussion, I said you were confusing the inside and outside of a control loop with the inside and outside of the person in whom the control loop exists. You are doing it again.
A simple (canaonical in PCT) control system consists of a loop that has two places affected by signals from outside the loop. The loop itself has two segments, which we can call an "inside part" and an "outside part". The "inside part" is connected to one signal from outside the loop (the "reference signal"), while the "outside part" is connected to the other (the "disturbance signal").
The "inside part" of a canonical control loop consists of three things and only those three with their connecting links: (1) an interface to the "outside part" called the "perceptual input function", which transforms data from the outside part of the control loop into a variable PCT calls the perceptual variable; (2) a comparator that compares the value of the perceptual variable with another variable coming from outside the loop (PCT calls it the "reference variable"); and (3) an output function that produces a variable that influences the "outer world".
The "outside part" of the control loop consists of the effects on the whole universe generated by the signal emitted by the output function, insofar as those effects influence the perceptual input function inputs. The perceptual input function is also influenced by a second signal from the outer universe, which PCT calls "the disturbance variable".
Usually, the control loop is drawn without a clean separation between inside and outside parts of the control loop. But when puzzles like yours arise, it is important that the separation be marked. And it even more important to note that this separation is NOT at the person's skin, except possibly for the most peripheral control systems. For almost all control loops, BOTH the reference signal and the disturbance signal come from within the person's skin, though outside the control loop. The control loop has no way to know whether their ultimate source lies inside the skin or outside it. The person's skin is simply irrelevant to the operation of the control loop.
Now, an external observer is, by definition, outside the person's skin, though if that person is a doctor or physiologist they may have probes that look beneath the skin. For most of us, and most of the time even for a doctor, we can perceive only what happens outside a person's skin. When we think of a person controlling anything, even their (imputed) internal perceptions, it's very easy to be seduced into thinking that the "outside parts" of all the control loops fall outside the person's skin.
That seductively easy, and almost always erroneous, equation of the inside and outside of a control loop with the inside and outside of the skin seems to be at the root of most of the puzzles you have brought up in the last couple of weeks.
In any case, if someone says, "Fred, your GAP-ACT (and that PCT stuff) is
all well and good but I hope you've noticed that it's focused on 'out there'
and doesn't deal with what goes on 'in here'," then I'm struggling with what
to say.
If you forget entirely about what Bill P. calls the "imagination loop", you will have a problem. If you forget that one can perceive some of one's bodily states, you will have a problem. If you take only the strict hierarchy of inputs from the outer world generating one layer after another of perceptual signals starting only from effects at the skin periphery, you will have a problem. But even the most rigorous versin of HPCT accepts that internal signals and cross-feeds from references to perceptions do exist. So, too, should GAP-ACT. The "out there" to a control loop can very well be "in here" to the person.
I'm looking for help again - as usual ...
I hope the foregoing is more help than confusion!
Martin