Incoherence, Predictability

[From Rick Marken (960323.1720)]

Ellery Lanier (960323 11:40) --

I am new to this list and slightly bewildered by the jargon.

Hi Ellery. Welcome to CSGNet. How did you find us?

We actually think of the "jargon" as "very precise use of
language":slight_smile: Words like "control", "controlled variable",
"disturbance", "reference", etc. have very specific denotations.
Part of learning about perceptual control theory (PCT)
involves learning the meaning of the words that refers to
specific aspects of control theory and the phenomenon that it
explains. Doing this _usually_ helps reduce confusion in

It is hard to realize that the Powers book was published in
1973! Have the psychologists been asleep?

No. I think they have been wide awake and controlling for
a perception of a cause-effect model of behavior, to which
PCT is a distinct disturbance.

What I see now is that the somatotype controls perception

What perception does the somatotype control? Indeed, how can
a somatotype control anything? In order to control, a somatotype
would have to be able to perceive and influence the state of
the controlled variable(s). I doubt that a somatotype has
the organizational components required to be able to control, but
maybe I'm wrong. Maybe I just don't know what a somatotype is.

Apparently I am the only one on the planet working with S.S. Stevens'
tables for human body types. Do I have a partner somewhere out there?

I kinda doubt it. What is it about control theory that leads you
to suspect that it might have something to do with Sheldon and
Stevens' body type work (boy,it's been a while since I heard about
that work)?

I thought there was reference to a meeting in Flagstaff in July, but I lost
the reference. Can someone fill me in on the details?

There will be a meeting of the Control Systems Group at Nortern Arizona U
from July 17 to 21. I'm sure someone will be posting some information
about the meeting soon.

Martin Taylor (960323 16:30) --

Thanks for the HyperCard stack. It's always nice to see you
doing experimental work.

One language problem: "quicker" is not the same as "higher amplitude."

Yes. But the result is the same; control is poorer (as you found in
your HyperCard experiment) with a higher frequency disturbance. But,
as with amplitude, this has nothing to do with predictability. Control
is poorer with a higher frequency disturbace even when the disturbance
is predictable (a sine wave, for example).

This whole predictability thing came up because it was said that
predictability is esential for control. I understood this to be a claim
that the ability to control required a lawful environment; one in
which there is a "predictable", lawful physical relationship between
the system's actions and the influence those actions have on the
controlled variable.

Most control does take place in such a predictable situation; the
actions of a thermostat system (heater on or off) have a predictable
influence on room temperature, for example. [I say predictable
_influence_ because the actual effect of actions on the controlled
variable also depends on prevailing disturbances; a heater's influence
on room temperature is to increase it; but the net effect of all
influences on room temperature (including, for example, the cold air
coming through the open window) may be to decrease it.]

The E. coli demo simply shows that it is _not_ necessary that the actions
of a control system have a predictable effect on the controlled variable
in order for there to be control. The direction of movement of the
dot after a bar press (whether or not there is a disturbance, and
regardless of the bandwidth if there is one) is perfectly unpredictable;
yet subjects can easily control the position of the dot. So predictability
(a predictable environmental influence of action on controlled variable)
is _not_ necessary for control.