[From Rick Marken (2014.03.01.1230)]
···
RM: I’m going to move this discussion to a new subject heading that, I think, gets at what this debate is really about, which is: How do we go about trying to understand the behavior of living organisms? Our debate up to this point must seem rather arcane and nit picky to anyone listening in – if anyone is listening in. So in the interests of showing its relevance to the “real world” of understanding living control systems (which is what I think people interested in PCT are interested in) I suggest that we try to frame this in terms of what our differences mean in terms of how we would go about trying to understand the behavior of living systems. So before I answer your post (below) in detail I’ll just say what I think are the “real world” implications of our debate.
What this all means to me is this: Understanding the behavior of living systems is a matter of learning what perceptual variables they control and how they control them. The fact that you can’t understand the true input-output characteristics of a component of a closed-loop system by measuring the input-output characteristics of that component while it is part of a control loop – the subject of the arcane debate between Martin and I – means that the way behavioral scientists have been going about trying to understand the behavior of living systems is misguided.
This is a profoundly important and revolutionary implication of PCT and it is one with which Martin, I believe, disagrees. And this disagreement is based on his belief that you can measure the true input-output characteristics of a component of a closed-loop system by measuring the input-output characteristics of that component while it is part of a control loop. In other words, you can continue trying to understand the behavior of living systems using the methods for understanding their behavior that have been used for the last 100 years.
So that’s the big picture, as I see it. If anyone is listening I’d be interested in their point of view on this topic as well.
Best regards
Rick
[Martin Taylor 2014.03.01.14.05]
Wrong.
You did it wrong. The reconnection should go to X, not S. Xrepresents the output, Z the disturbance, Y the perceptual value.
Yes.
No.
You did, and did again, perhaps more seriously.
OK, here’s a picture of a control loop, with signal values labelled.
Now tell me what are the i, the d and the o for the perceptual inputfunction component of the loop? I can see it for the comparator
component, (i is p, d is r, and o is e), but what are they for the
output function component? What are they for the Environmental
Feedback component up (the function E( ) in the diagram) to the
point where the disturbance gets added in?You insist that if you could measure the signals labelled "i" and“p” in the diagram, you could not say anything about the function P(
), because it is in a loop, but if you disconnected, say the “o”
connection to the input of E( ), then by looking at “i” and “p” you
could determine P( ). I say that P( ) does not change if you
disconnect “o” from the input of E( ). All that would change would
be the statistics of the values you would see at “i”, not the
relationship between the “i” values and the “p” values. The same
goes for “e” and “o” being determined by, and determining G( ), and
for “o” and “v” being determined by, and determining E( ).According to you, these relationships are different if the componentis part of a loop or if the loop is broken at some point. Why so?
(And a mathematical argument would be preferable to an argument
based on “OCT says so” or “I believe strongly that it is so”). If
you are correct, how is it possible to set up and use the control
equations that depend on the relationships between those inputs and
outputs being the same in open-loop and closed-loop situations.RM: So if by "input-output characteristic" you mean themeasured (rather than the actual) input-output characteristic of
a system component, then there is no disagreement between us:
components of differently structured circuits, in terms of
whether these circuits are open or closed loop, will not have
the same measured input-output characteristics even if
they have the same actual input-output characteristic.
If that’s what you believe as well then we are on the same page,
indeed.
MT: It's rather annoyingto be continually misrepresented in this way.
RM: Well I sure hope that's true. Is what I say above a moreaccurate representation of your point of view?
No.
Martin
Richard S. Marken PhD
www.mindreadings.com
The only thing that will redeem mankind is cooperation.
-- Bertrand Russell
–
[From Rick Marken (2014.03.01.1045)]
Martin Taylor(2014.02.28.23.15)–
MT: Let’s ask another question. Here are two circuits:
` Z` ` |`` `` X------|---S---->function>------YX------S—>function>-------Y `
Now, given a lot of observations of X and Y, is itpossible to discover the nature of the function in each
circuit? In theory one cannot…You can, however, measure the function in both diagramsif, instead of measuring at X you measure at S.
RM: So you say. In an open loop situation, as in your
two diagrams above, S is a function of X+Z for the left
diagram and of X on the right. So you would measure the
same relationship between X+Z and Y (on the left) and X
and Y (on the right) as between S and Y in both cases,
taking into account, of course, the relationship between
X+Y and S and X and S respectively. In a closed loop,
however, S is also a function of Y, so measuring the
relationship between S and Y will not reveal the nature of
the function relating S and Y.
MT: Map thesesubgraph diagrams onto the control loop by taking X to
be the output and Y the perceptual signal.
RM: That still leaves them as open-loop diagrams. To
map these properly onto a control loop (with X as output
and Y as input, you would have to draw a feedback path
from X back to Y. But then what’s S? The proper way to map
you diagrams onto a control loop is as follows (I’ll just
do it for the right hand diagram):
Z
` |``
`` X------|---S---->function>------Y`
^ |
| |
…
MT: I say that ifyou have a circuit element whose behaviour you can
assess by recording the covariation of its input and
output (not covariance), the assessment is exactly the
same whether the element forms part of a closed loop or
is measured in isolation or in any other network of
connections.
RM: Oops, this is quite different than what I showed in
my demonstration
RM: I went though the trouble to make this point,
not because I think it will convince you, Martin; it
looks like you’re pretty committed to the idea that
you can measure the open-loop input -output
characteristics of a system when that system is in a
closed loop.
(and what PCT shows).
So it looks like I didn't misrepresent your position
at all.
RM: Actually, it does. I think you might be saying that
you can measure the true i-o of a component of a loop by
looking at the relationship between i and o rather than
between d and o for that component.
MT: There is both truth
and error in this. See above. The error is not
by Powers, who was talking about the behavioural
illusion and the fact that if you look at the
disturbance and the output, what you learn is
the nature of the environmental feedback path,
not the properties of the organism. And that has
nothing to do with the topic under discussion.