[Hans Blom, 960701]
(Rick Marken (960628.1200))
Martin Taylor (960628 11:00) --
> The short answer is that behaviour can change all over the lot for any
> value of a reference condition.
Hans Blom (960628) --
>That's too easy, Martin. If you look carefully, you see that perceptions
>change continually as well. They're never exactly the same, everything is in
>continuous motion, including our body and our sensors.
This is a non-sequiter.
OK, I'll try again.
If the reference condition changes, the controlled perception
changes too.
And I think that in the overwhelming majority of cases when the
_action_ changes, the controlled perception changes as well. I think
it was you who said, some days ago, that moving your finger to a
prescribed spot on the computer's screen with eyes closed is far less
accurate than with eyes open. Correct. And why is this so? Because our
perceptions generally accompany our actions. We need to perceive what
we do. That is what makes accurate feedback possible.
But it's still true that, for any value of the
reference specification, behavior [action] can change all over the place
while the perception remains in the reference condition.
If that is the case, it must confuse levels. At a certain level, the
perception must track the effects of the actions in order for
feedback to be possible. So if action changes all over the place,
chances are that perception will do the same.
Martin gets full credit for his short answer;
I agree with giving Martin full credit. I just wanted to point out
that the story (PCT) has become so routine and ingrained in some of
us, that we seem to have a natural tendency to abbreviate greatly.
With the incrowd, that's no problem: they understand. With others,
the abbreviations may look like slogans, mantra's, irrational beliefs
that are not well grounded. It was in that sense that my remark was
made, and I came up with an objection that might immediately be
raised.
As you must know by now, I sometimes play the devil's advocate's job.
As a teacher you (I) tend to do that. But I also know that my playing
this role can greatly annoy others...
you get docked 10 points;-)
Please explain the rules of the game and what points are for. I seem
to have been unaware and stepped into the middle of, what? Can you
explain to me the game we're playing here? And who is the referee?
>My answer would be to say that it is equally correct to say that perceptions
>(or rather the difference between perceptions and references) control
>behavior.
And this would be completely and utterly wrong. It is wrong because, after
all these years, you still don't know the meaning of the word "control".
Control engineering was my major in University and it made up a great
deal of my professional activities after that. So don't tell me I
don't know the meaning of the word control. Has it ever occurred to
you that maybe YOU make the meaning so idiosyncratic that discussions
become almost impossible?
As I see PCT from my perspective, it is about discovering the "human
laws of robotics", the laws that govern how we humans behave. Could
you agree with that as the top-level goal?
Control means maintaining a variable in a specified state against
disturbance.
"Maintenance" is called "stabilizing control" in the technical
literature. There are other types of control as well, often in
combination. A different type is "regulating control" where the
objective is to bring a perception TOWARD a goal, and, as I have said
a number of times before, it requires different laws (or at least
different parameter settings). This has consequences: regulating
control, for instance, is required after sudden large changes of
reference value.
Neither perception (perceptual signal) nor the difference
between perceptions and references (error signal) _control_ behavior
[actions]. They influence behavior; the error signal even comes close to
determining behavior; but they don't control behavior. That is, they don't
take steps to restore behavior [action] to any particular state if it is
disturbed (see Bill Powers (960628.0920 MDT).
Here I'm utterly lost. I thought that we had agreed that there are
DEGREES of control and that control is not a black-and-white thing.
Yet you say that "the error signal even comes close to determining
behavior". Isn't that then pretty good control?
I think it's clear, after all these years (and disturbances from me), that
you are purposefully not understanding control theory. Now I'm just curious
about why you are doing this. What variable is the concept of "control of
perception" disturbing?
That variable is the concept "circular causality". If there is
circular causality (and a constant reference value, as is stressed
time and again), you can express any variable as a function of the
others. That is simple math. But the interpretation of the math is
clear as well: if behavior [action] can change all over the place,
HOW COME IT CHANGES IN EXACTLY THE RIGHT WAY?
That is why it is equally rational to say that actions are controlled.
It would not be rational to say this if you equate control with
stabilization or constancy. But control is not only that!
Greetings,
Hans