Information Theory Misleads About Control

[From Rick Marken (2012.12.08.1045)]

I'm moving this to a new subject head which I think better reflects
the subject of the debate.

Martin Taylor (2012.])--

RM: I'm afraid that you have fallen completely for the behavioral illusion.

MT: Them's fightin' words, buddy!

MT: Are you trying to say that the equations we usually use to describe the operation of a control system are wrong? It certainly sounds like it. Or are you saying that there is no signal path from sensory input through the perceptual function, the comparator, the output function and the environmental feedback path?

RM: No, I'm saying that the idea that variations in the output of a
control system are based on information about the disturbance to the
input to the system is an S-R concept. And the idea that S causes R in
a control system is the behavioral illusion. S (disturbances to a
controlled variable) are not the cause of R (outputs that also affect
the controlled variable. This "behavioral illusion" -- the appearance
that disturbances are the cause of outputs when they are not -- are
derived from the solution of the simultaneous equations for a negative
feedback control system.

Bruce Abbott (2012.12.07.1830 EST)--

RM: You are assuming that the only way for information about the disturbance to appear at the output is for this information to have gone through the organism.

BA: How else could it get there? Magic?

RM: Actually, there is no "it" (information) to get there. The
information about the disturbance in output is in the mind of the
observer who sees a correlation between disturbance and output. So
when I say that there is information about the disturbance in the
output of a control system I just mean that we do see a correlation
between disturbance and output when a system is controlling a
controlled variable. But that doesn't mean that there is really
something called "information" that is telling the system how to vary
its output in a way that compensates for the disturbance. And we know
from the equations of PCT that there is no such information becaust
the observed relationship between disturbance and output depends not
on characteristics of the organism but on characteristics of the
feedback connection between system outputs and controlled variable.

RM: One way to show, sans mathematics, that information about the
disturbance could not possibly be the cause of outputs that keep a
variable under control is by changing the feedback connection from
output to controlled variable during a tracking task. For example, if
cv = k*o+d then if you vary the value of k you are varying the gain of
the feedback connection from output to controlled input (cv). When
you do this you will find that the subject is perfectly capable of
keeping cv at a reference value (assuming you don't vary k too
quickly) but that there is no longer any information about the
disturbance in the output; that is, there is no longer any correlation
between o and d. That's because information about d was never
necessary. All that was needed was a perception of the state of cv
which could be continuously compared to a reference resulting in
variations in o that prevent the cv from moving very far from the

RM: By making believe that outputs are driven by information about the
disturbance you are not only ignoring a fundamental insight of PCT
(that the apparent causal link between disturbance and output is an
illusion) but you are also ignoring the central feature of control
that is the reason why the illusory causal connection between
disturbance and output exists (when the feedback function is
constant): the controlled variable.

RM: The importance of the controlled variable in this illusion is
demonstrated by a little demonstration I reported in Marken, R. S.
(1989) Behavior in the First Degree. In W. Hershberger (Ed.)
Volitional Action, Elsevier Science Publishers: North-Holland.The
subject controlled either the perimeter or area of a rectangle. The
subject varied the width of the rectangle while the computer varied
the height. So w is the subjects output and h is the disturbance. When
the subject controlled perimeter the controlled variable was cv =
2(w+h); when the subject controlled area cv = w*h. In both cases the
subject was to keep the cv constant at some value. When the subject
was controlling perimeter, the relationship between output(w) and
disturbance (h) was linear; when controlling area the relationship
between output and input was quadratic. Since the disturbance was the
same in both cases, somehow the "information" about this disturbance
either changed when controlling area rather than perimeter (you would
have to explain the mechanism by which this happened) or the subject
was just controlling a different perception with a different
relationship of disturbance to controlled perception (and, per the
"behavioral illusion" output is a function of both the feedback
connection from output to cv -- which doesn't change when going from
control of perimeter to control of area -- and the connection from
disturbance 9h) to control led variable, which does).

RM: I care about you guys getting this right -- understanding that
information about the disturbance is not what "guides" the output in
control -- only because I think not getting this right takes your eye
off what I think is the main "ball" in PCT: controlled variables. This
is the revolutionary and powerful new concept that is provided by PCT
(compared not only to conventional psychology but to other
applications of control theory to behavior as well). When you
understand that behavior is organized around the control of perceptual
variables -- controlled variables -- and you see how this explains the
variations in "outputs" that we see as behavior, then it reorients (or
_should_ reorient) the goal of research in behavioral science from the
search for the information that guides output to a search for the
perceptual variables that organisms control.




Richard S. Marken PhD