More Control of Behavior

CSGnet Archive CSG1998
41

[From Bruce Gregory (980914.0627 EDT)]

Bill Powers (980913.2117 MDT)

In particular, we are trying to devise a model that will account for the
behavior of the house's temperature over time, given that the furnace is
going on and off, people are walking in and out of doors and opening and
closing windows, and winds of varying temperatures and sun and cloud
phenomena are changing the heat losses and gains through the walls of the
house. What we observe is that the net effect of all the heat losses and
gains through doors, windows, and walls just happens to be offset by
variations in the on-time of the furnace, so that the temperature near a
small box on the wall stays remarkably close to 70 degrees F. And we also
observe that after a person goes to the box and fiddles with it, all the
same relationships go on happening, but the temperature is now constant at
65 degrees F.

This is the phenomenon for which we need a model.

I agree. It just doesn't happen to be the phenomena I was modeling. In my
example, no such stability was observed so none needed to be accounted for.
I think the issue is semantic, not substantive. You would only discover the
existence of the thermostat in the winter because in the summer the
temperature would behave in exactly the same way whether or not the
thermostat and heater were present.

>I realize that this must make me a PCT pariah but Occam's razor is too
>important a tool to put aside for reasons of theological purity.

And it is too sharp for us to encourage its use by the unskilled.

Is this a gratuitous remark or a sage observation? I'll consider it to be
the latter.

Bruce Gregory

42

[From Bruce Gregory (980914.0955 EDT)]

Bruce Abbott (980913.2020 EST)

If you wished to describe the system of variables so that you could
accurately predict the changes in room temperature under all possible
conditions, you would need to include the control system in your
description. If you wished merely to explain the changes in room
temperature during the summer, when the room temperature never drops below
70 degrees, you wouldn't, even though the control system designed to keep
room temperature from falling much below set-point is there and
functioning.

That's my interpretation as well.

Bruce Gregory

43

[Fropm Bill Powers (980914.0755 MDT)]

Bruce Gregory (980914.0627 EDT)--

I think the issue is semantic, not substantive. You would only discover the
existence of the thermostat in the winter because in the summer the
temperature would behave in exactly the same way whether or not the
thermostat and heater were present.

Exactly right, unless you happened to wonder what that box on the wall was
for and started playing with the reference signal.

>I realize that this must make me a PCT pariah but Occam's razor is too
>important a tool to put aside for reasons of theological purity.

And it is too sharp for us to encourage its use by the unskilled.

Is this a gratuitous remark or a sage observation? I'll consider it to be
the latter.

It was former. It sounded very clever to me at 2:00 AM. :frowning:

Best,

Bill P.

44

From [Bruce Gregory 9980914.1100 EDT)]

Marc Abrams (980913.1948)

>> Bruce Gregory (980913.1750 EDT) --
>>
>> > In my house, the thermostat is set to 65 F. During the
>> > summer, the temperature in the house never drops
>> >below 70 F. Is the thermostat controlling the
>> >temperature?

Rick asked and said:
>> What do you think? Your answer will be another indication
>>of how well you understand control theory.

Bruce G's response:
>In my view the question is, what are we trying to model?

Great answer, I agree. The question as originally
formulated by you is incomplete. Are people in the room?.

I think this is irrelevant since they would be additional heat sources, not
sinks. My point was simply that the furnace never turns on.

>If we are trying to model the temperature of the house,
there >is no need to introduce the thermostat and the
furnace into >the model.

Here I disagree. It might be inappropriate for _your_ model
but maybe not mine. You said "we are trying..." implying
more then one perspective of the problem.

For the period I described, the addition of the thermostat heater
combination does not effect the output of the model. You are free to include
it and anything else you like.

I totally agree and support your right to include and
exclude variables as _you_ see fit, for _your_ system
definition and boundaries. As Bill stated, lets establish the
facts first _then_ build the model.

I did my best to establish the facts.

>I realize that this must make me a PCT pariah but Occam's
>razor is too important a tool to put aside for reasons of
>theological purity.

I think your argument has more to do with establishing
_your_ system boundaries and components then with PCT and I
agree with your position on that. I don't understand the
connection to PCT though.

Simply the penchant for saying that an in place and working control system
"is" controlling when there is no need to include the control system in the
model. I would agree that the thermostat is controlling its own temperature
but feel no need to extend that control to the house. This is purely
semantics, however, and has nothing to do with the model. Imagine a
thermostat set to control for a temperature of 3000 K. Although this device
is never called on to act, it is controlling the temperature of the room.
Odd, but if used consistently, not a problem.

Bruce Gregory

45

[From Bruce Abbott (980913.1045 EST)]

Bill Powers (980913.2043 MDT) --

Bruce Abbott (980913.1320 EST)

That sounds like a perfectly good control system to me ...

I see only one problem with it: it is not designed to perceive YOUR speed.

No, not me in particular. But it is designed to perceive speeding
motorists, and if I am a speeding motorist, then with some nonzero
probability it (via its sensor the state trooper) will perceive my speed.

As you say, it is set up to perceive "motorists'" speed. The Department of
Transportation does not receive a report that Bruce Abbott was speeding.

In the system I outlined, the Department of Transportation does not have to
perceive my speed.

It
knows only that motorists drove, on I-95, at an average speed of 82 mph,
and that 1,255 speeding citations were issued from April 1 to May 1. While
your own performance contributed to that average speed, it did so only to a
minute degree; the loop gain must have been extremely low.

Bill, this is not relevant to the system I described, which does not require
the Department of Transportation to receive reports on the average speed of
motorists or on the number of citations issued.

There is some leeway in deciding just how much loop gain there has to be to
permit us to identify a control system, but I suspect that the threshold
gain will be something more than 0.001.

That the gain is low may or may not be true, but (a) the gain of the system
you described is not relevant to the question of whether the system I
described has sufficient gain, and (b) even if it were, you pulled that
figure (0.001) out of the air.

What the governor and the legislature have created is a system for
regulating the speed of motorists. The system is implemented in the form of
a radar equipped state trooper, who issues tickets to those who are detected
speeding. (The system is replicated many, many times across the state.) To
operate, the system need not report to the Department of Transportation who
was speeding or how many tickets were issued; it need only sit by the
roadside with the radar on and pull over any motorist exceeding the speed limit.

I read your post, Bill Powers (980913.1903 MDT); your description given
there of this system reads like a paraphrase of the earlier description I
gave of this system. Based on that, I think we agree about how this system
works, and that it is indeed a control system.

Puzzled,

Bruce

46

[From Bill Powers (980914.1447 MDT)]

Bruce Abbott (980913.1045 EST)--

That sounds like a perfectly good control system to me ...

I see only one problem with it: it is not designed to perceive YOUR speed.

No, not me in particular. But it is designed to perceive speeding
motorists, and if I am a speeding motorist, then with some nonzero
probability it (via its sensor the state trooper) will perceive my speed.

As you say, it is set up to perceive "motorists'" speed. The Department of
Transportation does not receive a report that Bruce Abbott was speeding.

In the system I outlined, the Department of Transportation does not have to
perceive my speed.

Then it can't control your speed, can it?

Best,

Bill P.

It
knows only that motorists drove, on I-95, at an average speed of 82 mph,
and that 1,255 speeding citations were issued from April 1 to May 1. While
your own performance contributed to that average speed, it did so only to a
minute degree; the loop gain must have been extremely low.

Bill, this is not relevant to the system I described, which does not require
the Department of Transportation to receive reports on the average speed of
motorists or on the number of citations issued.

There is some leeway in deciding just how much loop gain there has to be to
permit us to identify a control system, but I suspect that the threshold
gain will be something more than 0.001.

That the gain is low may or may not be true, but (a) the gain of the system
you described is not relevant to the question of whether the system I
described has sufficient gain, and (b) even if it were, you pulled that
figure (0.001) out of the air.

What the governor and the legislature have created is a system for
regulating the speed of motorists. The system is implemented in the form of
a radar equipped state trooper, who issues tickets to those who are detected
speeding. (The system is replicated many, many times across the state.) To
operate, the system need not report to the Department of Transportation who
was speeding or how many tickets were issued; it need only sit by the
roadside with the radar on and pull over any motorist exceeding the speed

limit.

···

I read your post, Bill Powers (980913.1903 MDT); your description given
there of this system reads like a paraphrase of the earlier description I
gave of this system. Based on that, I think we agree about how this system
works, and that it is indeed a control system.

Puzzled,

Bruce

47

[From Bruce Abbott (980914.1745 EST)]

Bill Powers (980914.1447 MDT)

Bruce Abbott (980913.1045 EST)

In the system I outlined, the Department of Transportation does not have to
perceive my speed.

Then it can't control your speed, can it?

No, it can't. But I seem to be missing the significance of that with
respect to the system we were discussing, and I'm willing to bet real money
that everyone else who has been following our exchanges is missing it, too.
Please explain.

Regards,

Bruce

48

[From Bill Powers (980915.627 MDT)]

Bruce Abbott (980914.1745 EST)--

In the system I outlined, the Department of Transportation does not have
to perceive my speed.

Then it can't control your speed, can it?

No, it can't. But I seem to be missing the significance of that with
respect to the system we were discussing, and I'm willing to bet real money
that everyone else who has been following our exchanges is missing it, too.
Please explain.

Maybe I'm mixing up two threads here, but I thought you were alluding to
control of behavior by the state. I think we're straight regarding the
trooper.

In fact, I hope I never hear from that trooper again.

Best,

Bill P.

49

[From Bill Powers (980915.0646 MDT)]

Bruce Abbott (980913.1045 EST)--

You questioned tne relevance of my comnment about the Department of
Transportation perceiving your speed. I had already archived your post but
I have it back now. Here is the section I was referring to:

···

===========================================================================
But is the state controlling your speed when it sets up speed laws and
enforces them via the state troopers? By so doing it changes the
environment in which drivers operate their vehicles. In this changed
environment, there is a probabilistic relationship between exceeding the
posted speed limit and receiving a ticket. Those for whom the prospect of a
ticket arouses anxiety can reduce this anxiety to zero by driving no faster
than the posted limit. Yet driving at this speed may conflict with other
goals, such as not being late for an appointment, and in such cases drivers
may resolve the conflict by maintaining the speed limit or by speeding and
risking the ticket. In one sense your (the motorist's) behavior is
completely under your control -- you set your own references, after all.
Yet by setting up an artificial contingency between your motoring speed
(relative to a posted speed) and the probability of receiving a ticket with
its associated delays and fine, the state sets up an internal conflict in
the motorists which in many cases will be resolved by keeping speed within
the posted limit. To the extent that this contingency works, the state is
able to bring motorists' speeds down to values near the posted (reference)
values. When it doesn't, the state, through its agents, the state troopers,
takes action by stopping the offenders and issuing tickets. To the extent
that this action convinces motorists to slow down, we have a nice little
control system, complete with reference values (posted speed limits),
sensors (radar-equipped state troopers), and output systems (state troopers)
whose actions tend to bring the controlled variable (peceived speed of
motorists) down toward the reference values. Yet the motorists are
completely in control of their own motoring speeds. Neat paradox, don't you
think?

It seems to me that my comment is entirely relevant to this passage. You
say that the state, acting through the troopers, does control your driving
behavior. But to control anything, a control system must perceive it, and
as far as I can see, your arrangement does not include any provision for
the state to perceive your driving behavior. The trooper certainly can
control your driving behavior, but the state can only control the driving
behavior it can perceive: namely, the statistical properties of the
population of drivers and their average driving behavior.

Here is my previous comment that you found irrelevant:

Powers:

As you say, it is set up to perceive "motorists'" speed. The Department of
Transportation does not receive a report that Bruce Abbott was speeding.

Abbott:

In the system I outlined, the Department of Transportation does not have to
perceive my speed.

Powers:

It
knows only that motorists drove, on I-95, at an average speed of 82 mph,
and that 1,255 speeding citations were issued from April 1 to May 1. While
your own performance contributed to that average speed, it did so only to a
minute degree; the loop gain must have been extremely low.

Abbott:

Bill, this is not relevant to the system I described, which does not require
the Department of Transportation to receive reports on the average speed of
motorists or on the number of citations issued.

So you are asserting that the Department of Transportation (or whatever
agency stands for "the state") does not need to perceive ANYTHING about
"motorists" in order to control how fast they drive. Could you please
diagram how The State does this? I really don't see how it could.

Best,

Bill P.

50

[From Bruce Abbott (980915.0815 EST)]

Bill Powers (980915.627 MDT) --

Maybe I'm mixing up two threads here, but I thought you were alluding to
control of behavior by the state. I think we're straight regarding the
trooper.

The only allusion I made to the state was that its representatives (the
legislators, the governor) have designed and implemented this control
system. They are no more a part of the system itself, than the engineer
who designed your home heating system is a part of its temperature control
system.

In fact, I hope I never hear from that trooper again.

Fine with me -- I'm a little tired of him myself! In fact, I'm much more
interested in the exchange going on between you and Bob Eberlein.

Regards,

Bruce