[From Rick Marken (2012.12.24.0950)]
Bill Powers (2012.12.23.1915 MST)--
My bark is apparently a lot worse than my bite.
> BP: However, there is a lawful chain of causation between disturbance
> and output, which we build into each model we run.RM: I thought the chain of causation went from o+d to o and that this
chain is part of of a loop. Yes' there is a path from d to o but it is
completely confounded with the path from o to o. Saying there is a
chain of causation from d to o could suggest to those trying to avoid
doing research based on the Test for Controlled Variables that we can
study the characteristics of this chain using conventional IV-DV
methods.BP: That conclusion would demonstrate a misunderstanding. Each function in
the loop has an input and an output, and is a straight-through cause-effect
function. When you solve the system of equations that describes all the
functions and their interconnections, however, you get the behavior of the
closed-loop system. In fact you can show that each system variable in the
loop, such as the output quantity, can be described as a function of the two
independent variables, d and r (where d may be the sum of many
disturbances). With r held constant, variations in o are a function of
variations in d alone unless system noise is important, which I don't think
is often the case.
RM: Yes, but is o really a causal function of d? My impression was
that the relationship between o and d is a side effect of the system
acting to to keep error at zero. Indeed, I thought that was one way of
looking at the "behavioral illusion"; the illusion being that the
relationship between d and o appears to reflect the causal path from
stimulus (disturbance) to response (output) when, in fact, no such
causal path exists. Do I have that wrong?
BP: The main difference between an S-R system and the closed-loop system is that
in the latter kind of system, the overall function connecting d and o has a
form determined mostly by the feedback function and to a lesser degree (how
much less depending on loop gain) by functions acting in the forward
direction, the perceptual input function, comparator, and output function.
RM: I see this as the second aspect of the "behavioral illusion", the
first being what I mention above; that the d - o relationship appears
to reflect a causal path through the organism (the organism function)
from d to o that doesn't actually exist. The second aspect being the
one you mention here: The form of the apparent causal relationship
between o and d is determined mostly by the feedback function. So the
complete "behavioral illusion" is that there is a causal path from d
to o and that the form of this path is determined by characteristics
of the organism. PCT shows that the reality is that there is no causal
path from d to o and that the form of this apparent causal path is
determined mainly by the feedback function connecting output to input,
not by characteristics of the organism. Do I have that wrong too?
RM: I'm barking up the same trees I've been barking up since 1980,
when the implications of PCT for my field (experimental psychology)
hit me squarely between the eyes. If Martin and Bruce would agree that
it is impossible to study the causal path from disturbance (S) to
output (R) in a control loop using the conventional methods of
experimental psychology then I'll stop barking.BP: It is time to update your conception of the implications of PCT, if it is
that ancient (unchanged for 32 years?).
RM: I actually have (hopefully) been continuously improving my
understanding of those implications over the last 32 years. But I
always appreciate "feedback" on it.
BP: Your conclusions are of course, mostly correct,
RM: Well, thank heaven that those 32 years haven't been completely wasted.
BP: but you tend to express them in terms of idealized
approximations that result from letting loop gain go to infinity. When you
say "no information" you should be saying "almost no information" and so on.
And you probably shouldn't be mentioning information (Information) at all,
since those who do understand information theory are saying that you are
misrepresenting it.
RM: I said "no information" in the context of the varying feedback
function demo where I managed to get good control with virtually zero
correlation between d and o. I said "no information" under the
assumption that the correlatoin between d and o was proportional to
the information in o about d. I suppose I should have said "almost no
information" but if the correlation is something like .012 do I really
have to be that careful? And how can I not mention information when
that's what the whole discussion is about. If the observed correlatoin
between d and o is not an indication of the information about d in o
then all the information experts have to do is say so.
BP: It is perfectly possible to study the path from disturbance (S) to output
(R) using conventional methods of system analysis -- in fact that is exactly
what we do.
RM: I think I have to disagree here. I don't believe you can study
this path without knowledge of the variable that is under control: the
controlled variable. Conventional methods are based on a causal model
that does not include the concept of a controlled variable. The only
aspect of conventional methods that we use is manipulation of an IV
(S) and measurement of a DV (R) under controlled conditions. This
methodology can be used to study the path from S to R in a control
system only if you know that both S and R influence the state of a
particular controlled variable.
BP: What this analysis does is to show the dominance of the feedback
function in determining the apparent properties of that path, a fact that
cannot be seen if one uses a model that has no feedback in it. That is the
real beef: using the wrong model.
RM: Yes, and that is how I now frame my objections to conventional
methodology. That methodology is based on the wrong model -- an
open-loop causal model that includes no reference to a controlled
variable.
BP: This is a very important point, because it
shows that S-R theory is not a consequence of stupidity or ancestor worship
or some other character defect, but simply a matter of not having discovered
the right model. When behaviorism was forming, nobody knew what the right
model was because control theory hadn't been invented yet.
RM: I have never believed and have tried never to imply that anyone is
"stupid" for continuing to do research based on the open-loop causal
model. But I am very aware of the fact that people often take
criticism of their work as implying that they are stupid. In my latest
paper on this topic I actually included a statement trying to reassure
readers that my criticisms of their methodology was not a criticism of
them personally.
BP: This gives us a way to try to enlighten conventional scientists without
their having to lose face. They can't be blamed for their teachers not
knowing about control systems, nor could their teachers be blamed when
nobody at all understood them. A disaster shared by everyone is not nearly
as hard to take as a disaster suffered by you alone, especially if it was
specifically your fault. We can tell behaviorists that failure to include
the facts of control in early analyses of behavior was not specifically
anyone's fault. The originators of behaviorism were doing the best they
could with what they did know. It just happened to be insufficient for
getting the right answers to their questions about organisms.
RM: Completely agree.
BP: We have to be very careful not to make Western scientists lose face.
RM: I'm not as concerned about this as you seem to be. I believe these
people are grown-ups and should be able to deal with criticism as
such. But I'm certainly willing to be "careful" not to have people
lose face. How do you suggest I do that and at the same time be true
to my understanding of PCT?
Best
Rick
···
--
Richard S. Marken PhD
rsmarken@gmail.com
www.mindreadings.com