# Information

**URL:** <http://discourse.iapct.org/t/information/5644>\
**Category:** CSG1997\
**Created:** [April 19, 1997, 7:49pm UTC](http://discourse.iapct.org/t/information/5644 "1997-04-19T19:49:44Z")\
**Posts on this page:** 8\
**Page:** 1

<div class="post-metadata">

**Author:** ![Bruce\_Abbott](http://discourse.iapct.org/letter_avatar_proxy/v4/letter/b/ba8739/32.png) [@Bruce\_Abbott](http://discourse.iapct.org/u/Bruce_Abbott)\
**Post date:** [April 19, 1997, 7:49pm UTC](http://discourse.iapct.org/t/information/5644/1 "1997-04-19T19:49:44Z")

</div>

[From Bruce Abbott (970419.1450 EST)]

> Rick Marken (970418.2340) --
> 
> Me:
> 
> > If I am not able to design an experiment so that it produces clear  
> > and consistent results, I give up on the experiment until a  
> > cleverer person comes along and does it right.
> 
> Bruce Abbott (970418.1100 EST)
> 
> > Well, that explains why PCT has not advanced beyond simple  
> > tracking experiments in over 25 years. You leave all the  
> > really hard work to others -- and there ain't no others.
> 
> How true. But I reassure myself with the knowledge that  
> reinforcement theory has not advanced beyond simple feeding experiments  
> in over 60 years.

No, those "feeding experiments" have become quite sophisticated, and what  
has been learned from them could fill many large volumes. Why has there not  
been a similar explosion in the tracking field? Most studies can be  
implemented with nothing more than a PC and a single willing participant,  
and an enormous amount of data can be produced in short order (e.g., 3600  
data points in 2 minutes). (For comparison, those "simple feeding  
experiments" usually take months to complete, sometimes over a year.) Even  
ol' unfunded Rick Marken should be able to crank out several such studies a  
year in his spare time. So why the lack of activity?

> > Bruce Abbott (970418.2005 EST)
> 
> > there is no use arguing about it; it is an empirical question. We  
> > could answer it with appropriate data from a simple tracking study.

> I doubt it. We did such studies a couple years ago; Martin is convinced  
> that they showed that there is information about the disturbance in the  
> perceptual signal; I (and I think Bill and Tom)  
> am convinced that they showed that there is no such information in  
> the perceptual signal.

How can this be a matter of opinion if you have the data? Did anyone  
compute the quantity of information? What was it?

> We can design such studies again if you like. But I think it  
> might be nice to first discuss a higher level question: Why should  
> anyone care whether or not there is information about the disturbance in  
> perception? If there is such information it is certainly not  
> clear what it would be doing there.

Martin Taylor already answered that question. You are reifying  
"information" into a "something" that has something to "do." Information is  
just a metric for system performance. If I said that the output of a sensor  
conveys information about the termperature, would you ask me what the  
information is "doing there" in the wire?

The question is whether this alternative metric provides insights into  
system performance that are not as easy to obtain using other metrics (like  
the correlation between d and p). I'd like to see Martin give it a shot.  
What can it hurt?

> It may be, however, that the information about the disturbance is  
> something that control systems don't want. All control systems might  
> have a reference level of 0 for the amount of information about the  
> disturbance that they want to receive.

You seem to be on a reification \_binge\_, Rick. Control systems don't have  
wants with respect to information, nor reference levels. In fact, control  
systems don't "want" anything. They just do what they do. If this action  
happens to bring p near to r, they don't become any happier, and they don't  
feel sad or upset when these actions fail. They are not little people.

But a perfect control system \_would\_ allow \_no\_ information about a  
disturbance to p to show up in p. That's what control systems \_do\_:  
ideally, they isolate their controlled inputs from the effects of  
disturbance, and isolation means that one could learn nothing about the  
disturbance merely by monitoring p. On the other hand, if r were known to  
be constant, then any wiggles in p would indicate a disturbance to p.

> I can tell you why I \_don't\_ like the idea that there is information  
> about the disturbance in perception. I don't like it because it  
> sounds to me like an attempt to conceptualize control in S-R terms.  
> The information-based models of control that I have seen assume that  
> information about the disturbance is an aspect of the sensory input  
> to the system. This information \_guides\_ the outputs that compensate  
> for that disturbance.

That's just metaphorical speech. Information is just a metric. It implies  
nothing whatever about S-R or causality. You should be objecting to the  
concept of gain: it sounds like an attempt to conceptualize control in  
capitalist economic terms. (No doubt the term was invented by a Republican  
economist.)

> Of course, there might actually be information about the disturbance in  
> perception. If so, then I wonder what is it there for?

Arrgh. Let's rephrase this. "Of course, there might actually be some  
shared variance between the disturbance and the perception. If so, then I  
wonder what it is there for?" The steering wheel on my daughter's care  
shakes at under 20 mph. I wonder what the shaking is there for. Do these  
questions make any sense? No.

> > I note that you had \_no\_ comment about my claim that a system  
> > provided a sensor to detect the effect of its own actions on  
> > its perception of the CV would be capable of providing almost  
> > full information about the disturbance. Don't want to admit I  
> > have it right?
> 
> Both Bill and I noted that if a system (other than the one doing the  
> controlling) has access to both the perceptual signal, p, and output  
> variable, o, (assuming all other functions are constants) then it would  
> be trivially easy for that system to deduce the disturbance, since p = o  
> + d and d = o - p. The system doing the controlling  
> could compute the estimated value of d too, of course, and everything  
> would be fine as long as the system "provided" this information to some  
> other system and didn't use it itself as its perceptual or  
> output signal.

Well, you know Rick, the lack of comment does not indicate agreement; in  
fact it \_can\_ be interpreted as the opposite, if one is disposed to do so.  
I for one would find it most helpful if you explicitly indicate when you  
\_agree\_ with some observation or conclusion of mine as well as when you  
disagree. I'm not a mind reader.

> Of course, in a real situation, you would have to know a lot more  
> than just the output signal to deduce the disturbance variable(s);  
> you would have to know the feedback function, the number of  
> disturbing variables influencing the controlled variable and the  
> function relating EACH disturbing variable to the controlled  
> variable.

Yes, of course, with respect to the first. As for the rest, that depends on  
whether you need to know each disturbance individually or only their  
composite effect.

Regards,

Bruce

---

<div class="post-metadata">

**Author:** ![Human\_Factors\_Lab](http://discourse.iapct.org/letter_avatar_proxy/v4/letter/h/b3f665/32.png) [@Human\_Factors\_Lab](http://discourse.iapct.org/u/Human_Factors_Lab)\
**Post date:** [April 19, 1997, 11:41pm UTC](http://discourse.iapct.org/t/information/5644/2 "1997-04-19T23:41:13Z")

</div>

[From Rick Marken (970420.0030 PDT)]

Me:

> But I reassure myself with the knowledge that reinforcement theory  
> has not advanced beyond simple feeding experiments in over 60 years.

Bruce Abbott (970419.1450 EST) --

> No, those "feeding experiments" have become quite sophisticated,  
> and what has been learned from them could fill many large volumes.

I wasn't putting down feeding experiments. I was pointing out that  
reinforcement theorists, like control theorists, study the phenomenon of  
interest to them using a technique that has proven useful;  
feeding experiments for reinforcement theorists; tracking  
experiments for control theorists. Of course, since reinforcement  
theorists are unaware of the fact that they are studying a  
side-effect of the phenomenon of control, they have filled many  
large volumes with the results of sophisticated experiments that  
tell us almost nothing about what the subjects of these experiments are  
doing.

> Why has there not been a similar explosion in the tracking  
> field?...Even ol' unfunded Rick Marken should be able to crank  
> out several such studies a year in his spare time. So why the  
> lack of activity?

Gee. No need to mock my obvious failings. I know I haven't done much to  
advance the study of control. That's why I get excited when real smart  
people like you get interested in PCT. I figure that's when things will  
really take off.

I've been involved with PCT for about 16 years and the meager  
results of my efforts are published in \_Mind Readings\_. There are about  
11 research studies reported in that book so my PCT research output is  
about 11 studies in 16 years or .68 studies/year. Not much, I agree. But  
you can't get blood out of a turnip. You, on the other hand, have been  
involved with PCT for nearly 3 years and the results of your efforts are  
nowhere to be seen. So your research output is exactly 0 studies in 3  
years or 0.0 studies/year. If I were you  
I'd feel pretty embarassed to be bested by the likes of me;-)

> The question is whether this alternative metric [information]  
> provides insights into system performance that are not as easy  
> to obtain using other metrics (like the correlation between d  
> and p). I'd like to see Martin give it a shot. What can it hurt?

We would all like to see the insights information theory provides.  
But so far (after 4 years or so) no insights have been forthcoming. I'm  
happy to drop the information discussion until we get these insights.

> if r [reference signal value] were known to be constant, then  
> any wiggles in p would indicate a disturbance to p.

Oops. Can't drop it. Gotta point out that this is false. p is at all  
times the \_combined\_ result of output and disturbance (in the simplest  
case, p = o + d). So any variation in p less a constant is variation in  
o+d less a constant. So wiggles in r-p do not indicate a disturbance to  
p; they indicate the combined effects o and d on p.  
The wiggles could be entirely the result of variations in output,  
with d = 0.

> Information is just a metric. It implies nothing whatever about  
> S-R or causality.

Maybe not. But the psycholgical models I know that are based on  
information theory are are all open-loop, causal models. According to  
these models, sensory information is used by a central processor as the  
basis for making decisions and calculating actions. This is an  
open-loop model of behavior.

Information theory was designed to measure the quality of a  
communication channel, which is an open-loop system; messages  
are encoded at the input to the channel and the encoded messages  
are carried across the channel to a decoder which reconstructs the  
messages. Information theory allows us to measure how well the  
decoded messages match the messages that were actually encoded. I don't  
see how this analytic technique is relevant to the behavior  
of a closed loop system, where the output of the system (like the  
decoded messages) has an effect on the inputs (the encoded messages)  
that are causing those outputs.

Best

Rick

---

<div class="post-metadata">

**Author:** ![Bruce\_Abbott](http://discourse.iapct.org/letter_avatar_proxy/v4/letter/b/ba8739/32.png) [@Bruce\_Abbott](http://discourse.iapct.org/u/Bruce_Abbott)\
**Post date:** [April 20, 1997, 2:46pm UTC](http://discourse.iapct.org/t/information/5644/3 "1997-04-20T14:46:52Z")

</div>

[From Bruce Abbott (970420.1045 EST)]

> Rick Marken (970420.0030 PDT) --

> > Bruce Abbott (970419.1450 EST)

> > No, those "feeding experiments" have become quite sophisticated,  
> > and what has been learned from them could fill many large volumes.

> I wasn't putting down feeding experiments. I was pointing out that  
> reinforcement theorists, like control theorists, study the phenomenon of  
> interest to them using a technique that has proven useful;  
> feeding experiments for reinforcement theorists; tracking  
> experiments for control theorists. Of course, since reinforcement  
> theorists are unaware of the fact that they are studying a  
> side-effect of the phenomenon of control, they have filled many  
> large volumes with the results of sophisticated experiments that  
> tell us almost nothing about what the subjects of these experiments are  
> doing.

There is nothing inherently wrong with doing tracking experiments, but those  
experiments should be providing new basic knowledge about the relevant  
systems, providing a broadening foundation for further progress. So far  
there hasn't been much done beyond some simple demonstrations showing that  
people are good at controlling cursor position, and that their performance  
is nicely modeled by a simple proportional controller with leaky  
integration. These are important demonstrations of principle, but they  
haven't told us much about how the human system is actually organized; very  
little has been done to investigate the nature of the hierarchy, for example.

As for the results of reinforcement experiments, as you know, I see things a  
bit differently than you. Experiments conducted to identify the  
"reinforcer" in a given situation tell us quite a bit about what the subject  
was attempting to control, in my view.

> > Why has there not been a similar explosion in the tracking  
> > field?...Even ol' unfunded Rick Marken should be able to crank  
> > out several such studies a year in his spare time. So why the  
> > lack of activity?

> Gee. No need to mock my obvious failings. I know I haven't done much to  
> advance the study of control. That's why I get excited when real smart  
> people like you get interested in PCT. I figure that's when things will  
> really take off.

I'm not mocking your "failings," nor am I casting aspersions on your  
intelligence. I am asking why an intelligent scholar well-versed in control  
theory has not produced more in the way of empirical research into control.  
It clearly isn't for lack of motivation, and such research doesn't appear to  
require a lot of subjects, time, or sophisticated and expensive equipment.  
Might it have something to do with the nature of the subject matter?

> I've been involved with PCT for about 16 years and the meager  
> results of my efforts are published in \_Mind Readings\_. There are about  
> 11 research studies reported in that book so my PCT research output is  
> about 11 studies in 16 years or .68 studies/year. Not much, I agree. But  
> you can't get blood out of a turnip. You, on the other hand, have been  
> involved with PCT for nearly 3 years and the results of your efforts are  
> nowhere to be seen. So your research output is exactly 0 studies in 3  
> years or 0.0 studies/year. If I were you  
> I'd feel pretty embarassed to be bested by the likes of me;-)

How about summarizing what you learned about the human control system from  
those 11 studies?

I've now been involved in PCT since November 1994, or a little under 2.5  
years. I spent the first year and a half developing my understanding of  
control theory (with a lot of help from Bill P., you, and many other  
CSGnetters), learning how do program control simulations, programming,  
conducting, and analyzing several tracking experiments, and constructing  
control models capable of generating certain results known from the operant  
conditioning literature. I spent the next year conducting experiments to  
understand what is going on in ratio schedules of reinforcement and to  
investigate the control of nutrient level (as reflected in body weight) in  
lab rats. In these studies, data were collected \_daily\_ for nearly a year.  
Given the massive amount of data collected, it is going to take me a while  
to get it all sorted out. That brings us up to now.

For some reason, I don't feel embarrassed at all.

> > if r [reference signal value] were known to be constant, then  
> > any wiggles in p would indicate a disturbance to p.

> Oops. Can't drop it. Gotta point out that this is false. p is at all  
> times the \_combined\_ result of output and disturbance (in the simplest  
> case, p = o + d). So any variation in p less a constant is variation in  
> o+d less a constant. So wiggles in r-p do not indicate a disturbance to  
> p; they indicate the combined effects o and d on p.  
> The wiggles could be entirely the result of variations in output,  
> with d = 0.

If r is fixed, d = 0, and output varies, then o is itself a disturbance to  
p. Output varies because the residual effects of earlier variations in d  
are still reverberating in the loop. So what I said is \_not\_ false: if p  
wiggles, then p is being disturbed. By definition.

Regards,

Bruce

---

<div class="post-metadata">

**Author:** ![Human\_Factors\_Lab](http://discourse.iapct.org/letter_avatar_proxy/v4/letter/h/b3f665/32.png) [@Human\_Factors\_Lab](http://discourse.iapct.org/u/Human_Factors_Lab)\
**Post date:** [April 20, 1997, 10:09am UTC](http://discourse.iapct.org/t/information/5644/4 "1997-04-20T10:09:26Z")

</div>

[From Rick Marken (970420.1100)]

Bruce Abbott (970420.1045 EST)

> very little has been done to investigate the nature of the  
> hierarchy, for example.

Well, if you want more investigations, why don't YOU do them. I  
think the tiny number of PCT based tracking studies that have been done  
(and published) tell us more about human nature that all the books found  
in the BF section of the library put together.

> As for the results of reinforcement experiments, as you know, I  
> see things a bit differently than you. Experiments conducted  
> to identify the "reinforcer" in a given situation tell us quite  
> a bit about what the subject was attempting to control, in my  
> view.

They may \_suggest\_ possible controlled variables but I can't see  
how they could possibly tell us "quite a bit" about what the subject  
is attempting to control. I think that all we can say from the results  
of 60 years worth of reinforcement experiments is that animals  
probably control some aspect of their food and water intake.

> I'm not mocking your "failings," nor am I casting aspersions on  
> your intelligence. I am asking why an intelligent scholar  
> well-versed in control theory has not produced more in the way  
> of empirical research into control.

I can only produce the amount of research that I want to (and can)  
produce. In fact, I have produced more research than is reported in  
\_Mind Readings\_ but it's very difficult to get this stuff published,  
largely because it is virtually impossible to get it past reviewers who  
(like you) see this research as contributing very little to our  
understanding of behavior.

> Might it have something to do with the nature of the subject  
> matter?

Yes, of course. Conventional psychologists seem to think that  
PCT experiments don't tell them much; certainly nothing they didn't  
already know. So it's hard to publish PCT experiments or get  
conventional psychologists to pay attention to them. To me, science is,  
in large part, a social enterprise; a collective effort to  
understand the world around us (including ourselves and other people in  
that world). If the members of this scientific society show no interest  
in (and, in many cases, active hostility towards) one's research  
offerings, the inclination is to do stop offering.

> How about summarizing what you learned about the human control  
> system from those 11 studies?

Gee, I've been doing that on the net here for years. I've learned  
that people control perceptual input variables by varying their actions,  
as necessary, to produce intended perceptions. I've learned that you  
can't tell what variable an organism is controlling by just looking for  
patterns in its actions or in the results of those actions. I've learned  
that multiple control systems can automatically coordinate their outputs  
to produce intended results. I have learned  
that the only way to determine what a person is controlling is by  
testing for controlled variables. I have learned that people select the  
consequences their actions and that the appearance that actions are  
selected by their consequences is an illusion. I have leaned that the  
controlling done by one control system can be changed by the controlling  
done by other control systems in the same person.

> I've now been involved in PCT since November 1994, or a little  
> under 2.5 years. I spent the first year and a half developing  
> my understanding of control theory

It seems to me that you've spent most of your time trying to set me  
straight about conventional psychology.

> I spent the next year conducting experiments to understand what  
> is going on in ratio schedules of reinforcement and to  
> investigate the control of nutrient level (as reflected in body  
> weight) in lab rats...Given the massive amount of data collected,  
> it is going to take me a while to get it all sorted out.

I think it's great that you are doing this research. I look forward  
to your report of the results. Based on Bill Powers' report on the  
status of the research (at the CSG meeting nearly 1 year ago!) it  
seems like there are plently of interersting findings that should  
be brought to the attention of the animal behavior community. I hope  
you're planning to write this up and submit it for publication soon.

> If r is fixed, d = 0, and output varies, then o is itself a  
> disturbance to p. Output varies because the residual effects  
> of earlier variations in d are still reverberating in the loop.  
> So what I said is \_not\_ false: if p wiggles, then p is being  
> disturbed. By definition.

Actually, this is NOT the definition of disturbance. See Bill Powers  
(970419.1830 MST).

Best

Rick

---

<div class="post-metadata">

**Author:** ![Bruce\_Abbott](http://discourse.iapct.org/letter_avatar_proxy/v4/letter/b/ba8739/32.png) [@Bruce\_Abbott](http://discourse.iapct.org/u/Bruce_Abbott)\
**Post date:** [April 21, 1997, 2:29am UTC](http://discourse.iapct.org/t/information/5644/5 "1997-04-21T02:29:36Z")

</div>

[From Bruce Abbott (970420.2230 EST)]

> Rick Marken (970420.1100)]
> 
> Bruce Abbott (970420.1045 EST)
> 
> > very little has been done to investigate the nature of the  
> > hierarchy, for example.
> 
> Well, if you want more investigations, why don't YOU do them.

O.K. What do you suggest, boss?

> > As for the results of reinforcement experiments, as you know, I  
> > see things a bit differently than you. Experiments conducted  
> > to identify the "reinforcer" in a given situation tell us quite  
> > a bit about what the subject was attempting to control, in my  
> > view.

> They may \_suggest\_ possible controlled variables but I can't see  
> how they could possibly tell us "quite a bit" about what the subject  
> is attempting to control. I think that all we can say from the results  
> of 60 years worth of reinforcement experiments is that animals  
> probably control some aspect of their food and water intake.

You really don't know much about it, or you wouldn't say that. However,  
definitely \_lacking\_ is any physical model of the system that would  
\_explain\_ the many interesting behavioral phenomena this research has  
disclosed. That's the next step, and what PCT promises to do.

> I am asking why an intelligent scholar
> 
> > well-versed in control theory has not produced more in the way  
> > of empirical research into control.

> I can only produce the amount of research that I want to (and can)  
> produce. In fact, I have produced more research than is reported in  
> \_Mind Readings\_ but it's very difficult to get this stuff published,  
> largely because it is virtually impossible to get it past reviewers who  
> (like you) see this research as contributing very little to our  
> understanding of behavior.

I didn't say that. I asked why there seems to have been so little progress  
beyond the basic tracking studies.

> > Might it have something to do with the nature of the subject  
> > matter?
> 
> Yes, of course. Conventional psychologists seem to think that  
> PCT experiments don't tell them much; certainly nothing they didn't  
> already know. So it's hard to publish PCT experiments or get  
> conventional psychologists to pay attention to them.

No, no, you've changed the context of my questions. I wasn't asking why  
more studies have been \_published\_, but why more have not been \_conducted\_.  
Reviewers and journal editors may make it difficult to get a study  
published, but they certainly can't stop you from doing the research.

> > How about summarizing what you learned about the human control  
> > system from those 11 studies?
> 
> Gee, I've been doing that on the net here for years. I've learned  
> that people control perceptual input variables by varying their actions,  
> as necessary, to produce intended perceptions. I've learned that you  
> can't tell what variable an organism is controlling by just looking for  
> patterns in its actions or in the results of those actions. I've learned  
> that multiple control systems can automatically coordinate their outputs  
> to produce intended results. I have learned  
> that the only way to determine what a person is controlling is by  
> testing for controlled variables. I have learned that people select the  
> consequences their actions and that the appearance that actions are  
> selected by their consequences is an illusion. I have leaned that the  
> controlling done by one control system can be changed by the controlling  
> done by other control systems in the same person.

Most of those things are implications of PCT, not empirical results. I  
didn't ask you to summarize what you've learned about control, I asked you  
to summarize your \_research findings\_. Didn't one study, for example, show  
that suddenly reversing the sign of the environmental function produced a  
runaway action for about 0.5 seconds, after which the participant regains  
control by reversing the sign of the output function? That's the sort of  
empirical stuff I'm asking about.

> > I've now been involved in PCT since November 1994, or a little  
> > under 2.5 years. I spent the first year and a half developing  
> > my understanding of control theory

> It seems to me that you've spent most of your time trying to set me  
> straight about conventional psychology.

Yes, an obvious example of maladaptive behavior that supports neither  
reinforcement theory nor the reorganization principle. It's probably a  
manifestation of brain damage.

> I think it's great that you are doing this research. I look forward  
> to your report of the results. Based on Bill Powers' report on the  
> status of the research (at the CSG meeting nearly 1 year ago!) it  
> seems like there are plently of interersting findings that should  
> be brought to the attention of the animal behavior community. I hope  
> you're planning to write this up and submit it for publication soon.

I certainly could use a publication or two at the moment, so I'm hoping so, too.

> > If r is fixed, d = 0, and output varies, then o is itself a  
> > disturbance to p. Output varies because the residual effects  
> > of earlier variations in d are still reverberating in the loop.  
> > So what I said is \_not\_ false: if p wiggles, then p is being  
> > disturbed. By definition.

> Actually, this is NOT the definition of disturbance. See Bill Powers  
> (970419.1830 MST).

Disturbance it is; THE disturbance it isn't. When \_I\_ use a word, it means  
what I want it to mean; that's why I pay it so well. (;-\>

Let's not quibble over words; the reverberations of previous disturbance  
appear in the form of output wiggles, which shake p from its tranquility.  
If an action itself results in the production of further error, it is a  
disturbance in my book. It makes more sense to me to call this a form of  
disturbance when, for example, it leads to oscillations, damped or undamped.  
After the first impulse, the system keeps disturbing \_itself\_.

Regards,

Bruce

---

<div class="post-metadata">

**Author:** ![Richard\_Marken](http://discourse.iapct.org/letter_avatar_proxy/v4/letter/r/9fc348/32.png) [@Richard\_Marken](http://discourse.iapct.org/u/Richard_Marken)\
**Post date:** [April 26, 1997, 12:25am UTC](http://discourse.iapct.org/t/information/5644/6 "1997-04-26T00:25:48Z")

</div>

[From Rick Marken (970425.1730)]

Bill Powers (970422.1622 MST)

> I'll agree that Rick's point is different from mine, but it is not wrong...  
> Rick is wrong in saying that d CANNOT (by any means) be deduced from  
> knowledge of the variables, parameters and functions in the control loop.

I appreciate your efforts to provide Martin with some spiritual fulfillment  
but Rick (me;-)) never said that "d CANNOT (by any means) be deduced from  
knowledge of the variables, parameters and functions in the control loop".  
In fact, I (like you) have always pointed out that it is rather easy to  
compute d given p and knowledge of all the other relevant functions and  
variables' in a control loop. Indeed, earlier on the very same day that you  
said the kind words above to Martin, I [Rick Marken (970422.0920)] told  
Hans (another fellow whose soul seems to sustain itself on the hope that  
"Rick is wrong"):

> If p = f(u) + d and you are given p and f(u) then I have no doubt that even  
> you could solve for d.

Of course, I am going with Hans' assumption that g(d) = 1\*d. I know, in  
other words, that if p = f(u) + g(d) then you would have to have f(u)  
\_and\_ g(d) (not just d) to solve for p.

Love

Rick

---

<div class="post-metadata">

**Author:** ![HANS\_BLOM2](http://discourse.iapct.org/letter_avatar_proxy/v4/letter/h/f17d59/32.png) [@HANS\_BLOM2](http://discourse.iapct.org/u/HANS_BLOM2)\
**Post date:** [April 28, 1997, 4:36pm UTC](http://discourse.iapct.org/t/information/5644/7 "1997-04-28T16:36:17Z")

</div>

[Hans Blom, 970428g]

(Rick Marken (970425.1730))

> Hans (another fellow whose soul seems to sustain itself on the hope  
> that "Rick is wrong"):

On the contrary, Rick! My only hope is that you will see the light,  
some time soon now ;-).

Hans

---

<div class="post-metadata">

**Author:** ![\_Martin\_Taylor](http://discourse.iapct.org/letter_avatar_proxy/v4/letter/_/a9adbd/32.png) [@\_Martin\_Taylor](http://discourse.iapct.org/u/_Martin_Taylor)\
**Post date:** [June 17, 1993, 10:06pm UTC](http://discourse.iapct.org/t/information/5644/8 "1993-06-17T22:06:05Z")

</div>

[Martin Taylor 930617 17:35]  
(Rick Marken 930617.0900)

> Martin Taylor (930617 09:50) correctly answered my three questions.  
> But he confuses me once again. In answer to:
> 
> > 3) Can you do it if I also give you the output function that was in effect at  
> > the time? Yes or no?
> 
> Martin says:
> 
> > Yes, if you assert that the output function includes the environmental  
> > path between the ECS and the CEV to which d is applied, and that the  
> > function is defined precisely and is monotonic.
> 
> This is true. But a control system that worked under these restrictions  
> would be working in a very contrived environment. In fact, it would  
> not even have to be a control system; a calculated output system  
> would do since the outputs that it generates are guaranteed to counter  
> the effects of the disturbing variable.

A misunderstanding here. All I asked was to know whether the output  
function was, say 10 \* integral(error), or 100 \* error^3 or whatever.  
The requirement was that this function be fixed. The assertion that  
the perceptual signal contains the information about the disturbance  
comes from the fact of control and the stability (relative to the  
disturbance) of the output function. And that stability has to extend  
as far as the CEV. It has to be a control system, not a calculated  
output system, or none of the argument works (it won't, either).

I agree that it is a most unnatural situation to have a fixed output  
function. I tried to persuade you of that in the earlier discussion  
on information, but you insisted that it was not so--that the output  
function would normally be fixed. My argument, which I think you now  
accept, was that control can be attained with an output function that  
is not only nonlinear, but which is also time-variant and uncertain.  
The information-theory view on this is that the time-variance and the  
uncertainty of the output function (i.e. the transform between error  
and the effect on the CEV) has to be considered as information that  
the control system must deal with, reducing the ability to control  
against the effects of the disturbance. Numerically, it is subtracted  
from the controllable information in the disturbance.

> So you are saying that the perceptual signal carries information about the  
> relationship between output and CEV. Yet, in your answer to question 3)  
> you said that you could not reconstruct the disturbance unless you were  
> given information about the relationship between the output and CEV (as  
> part of the specification of the output function).
> 
> This is why I want to stop talking about information and start talking  
> about how control systems really work.

That "This is why" is the non-sequitur that bugs me. I know I have a  
problem getting you interested. I have a problem getting Bill P interested,  
though he has asked a lot of penetrating questions that have helped me  
refine my concepts. But I hope I will succeed, and not go off into  
isolation mode, as you are tempted to do in respect of "mainstream"  
psychologists.

The point is, and always has been, that the "knowledge" of the output  
function is implicit in the fact of control. It is explicit only in  
the view of a modeller--an outsider view. It is the outsider who has  
to know the form of the function in order to do the calculation. The  
control system does it by correcting for error. If the output function is  
fixed, the amount of information involved in its specification very  
soon is swamped by the stream of information from the CEV (i.e. from  
the disturbance, if the reference is fixed). It vanishes from the  
calculation, and does not affect the ability of the system to control  
except insofar as a non-linear output function has a gain that differs  
for different levels of output. But if the output function is time-varying,  
information about it has to be factored into the calculation of the  
ability of the control system to control. That matters. And in a  
control hierarchy in which reference levels for lower ECSs come from  
several independent higher ECSs, it matters a lot.

> I know exactly  
> how control systems operate; I can build control systems that operate  
> in environments where the connection between output and CEV is  
> constantly changing and I can do it without understanding what is  
> meant be information.

Well, you are one (or more) up on me. I don't know "exactly" how  
control systems operate, especially if there are lots of them connected  
in nonlinear ways. I have some notions, however. Can you specify  
beforehand how such a net will respond, given limits on the perceptual  
resolution and bandwidth of its various perceptual input functions, and  
given a variety of behaviours of the multiple disturbances to which  
the various CEVs will be subjected? Maybe you can. I'm not claiming  
that information theory will tell you how such a system will operate,  
but I am claiming that it can provide you with limits on how well  
the different disturbances can be controlled.

I, too, want to talk about how control systems "really" work. I'm trying  
to lay the groundwork for doing so from a viewpoint complementary to  
the one you take, but supportive of it. Didn't thermodynamics help the  
understanding of many-body systems that were hard to understand using  
Newtonian mechanics? Newtonian mechanics might be correctly applied,  
and would give good prediction if the calculations could be carried through  
(with infinite precision, as we now know). But the thermodynamic approach  
provided different insights into the behaviour of such systems, insights  
that would not have been obtained even with an exact Newtonian calculation.  
In addition, it produced global results that could actually be used,  
approximate though they might be. I think we are in the same situation.

Martin