# mutuality

**URL:** <http://discourse.iapct.org/t/mutuality/14358>\
**Category:** CSG1993\
**Created:** [October 8, 1993, 12:06am UTC](http://discourse.iapct.org/t/mutuality/14358 "1993-10-08T00:06:40Z")\
**Posts on this page:** 3\
**Page:** 1

<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:** [October 8, 1993, 12:06am UTC](http://discourse.iapct.org/t/mutuality/14358/1 "1993-10-08T00:06:40Z")

</div>

[Martin Taylor 931007 19:30]

In introducing PCT to a control engineer in our Human Factors division  
yesterday, I came across a relationship that I am not aware of having  
been discussed (but I haven't read all of LCS 1 and 2, so, like emotion,  
it may be there). I call it "mutuality."

In "The Selfish Gene" Dawkins uses the image of the chromosome as a team  
of agents, each of which does something that benefits the reproductive  
success of the others, though not directly of itself. Genes that have  
this kind of complementarity tend to be found nearby on a chromosome  
because chromosomes can break and reconnect differently, reducing the  
chances that distant genes will, over long time scales, be passed together.  
Likewise (not from Dawkins) if there are two cells, each of which produces  
as a side effect of its own operation a substance that enhances the operation  
of the other, the bi-cell will survive better than either alone, if they find  
a way of sticking together physically, and of reproducing in tandem.

I propose that it is very likely that evolutionarily early control systems  
may have joined in such mutual arrangements, and that evolved control systems  
continue to do so. Here's the argument.

A single ECS (A) controls its perception in the presence of disturbances to  
its CEV (CEV-A). It can neither predict nor directly observe these  
disturbances, except as fluctuations in the value of CEV-A. Any ECS has  
limits on the speed with which it can compensate for the disturbances, and  
the range of disturbance force that it can counter.

Consider a second ECS (B), which has as its CEV-B some part of the variable  
that disturbs CEV-A. ECS-B has no perception of ECS-A or CEV-A. It simply  
controls CEV-B. But as a consequence of that control, the disturbance  
to CEV-A is reduced, easing the control by ECS-A of its own perception.  
Now suppose that CEV-A is part of the variable that disturbs CEV-B. Now  
ECS-B has an easier job of control, which directly eases control exercised  
by A. Each ECS in this figure-8 loop has a multiplicative effect on the  
apparent gain of the other.

Here's a picture:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;\> \>  
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;\> ref-A | ref-B  
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;----------O--------- ---------O----------  
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;\> \> \> \>  
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;PIF-A OUT-A PIF-B OUT-B  
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;\> \> \> \>  
&nbsp;&nbsp;=======^====================V======^===================V=======  
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;\> \> \> \>  
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;\<-----CEV-A\<-------- \<------CEV-B-------  
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;\> \> \> \>  
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;V DIST-A\<-------------------V DIST-B  
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;\> ^  
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;----------------------------------| This loop in the  
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;environment is unperceived  
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;by either ECS

In the diagram, DIST-A and DIST-B are supposed to be influenced by, but not  
identical to CEV-B and CEV-A respectively. The effect of each control  
system is to smooth the disturbance on the other, purely as a side-effect  
of its own perceptual control.

If the necessary (and I think not uncommon) environmental conditions hold,  
ECS-A and -B become symbiotes. It is advantageous for them to stay together.  
Organisms that evolve so that they do will be more stable than those in which  
the symbiotes are separated.

The mutuality connection need not, of course, be restricted to pairs of  
ECSs. Any situation in the environment in which there is a cycle of  
influences among variables that disturb controlled perceptions is enough  
to enhance the stability of all affected control loops. But bilateral  
mutuality (it's not cooperation) seems most likely to occur in a random  
environment.

A consequence of this thought is that mutuality is likely to be quite  
common within any evolved control hierarchy. There will be many ECSs  
for which a biologist might say "the purpose of this structure is to  
assist that structure," where a PCT analyst might initially say that  
the second structure is not perceptible to the first, and that the control  
exercised by the first is for its own selfish purposes. Not being able  
to perceive the second structure or its CEV, the first could not control  
for helping it. But evolutionary reorganization will have "controlled"  
for the mutuality.

Do I see a model here for social structures, perhaps?

Here today, gone tomorrow.

Martin

---

<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:** [October 9, 1993, 10:34pm UTC](http://discourse.iapct.org/t/mutuality/14358/2 "1993-10-09T22:34:56Z")

</div>

[From Rick Marken (931009.1500)]

Martin Taylor (931007 19:30)

> :A single ECS (A) controls its perception in the presence of disturbances to  
> its CEV (CEV-A). It can neither predict nor directly observe these  
> disturbances, except as fluctuations in the value of CEV-A.

A single ECS can neither predict nor directly observe these disturbances  
AT ALL -- certainly not as fluctuations in the value of CEV. The fluctuations  
in the value of the CEV depend, at every instant, on the combined effects of  
disturbance and output; in the simplest case the value of the CEV at any  
instant is proportional to the SUM of the instantaneous values of  
disturbance and output -- CEV = d+o. So disturbances cannot be observed  
in the fluctuations of the CEV because the disturbance caused component  
of these fluctuations is completely "masked" by the the output caused  
component. When you adjust the temperature of the water going into the  
bath you cannot tell how much of the current temperature of the water is  
caused by the prevailing temperature of the hot and cold water in the pipes  
(the disturbance) and how much is caused by your outputs (the amount by  
which you turn the hot and cold water faucets). All you perceive are the  
fluctuations in the CEV (water temperature).

Fluctuations in the CEV (the input to the control system) are no more  
important to the process of control than fluctuations in the output. The  
fluctuations in the CEV are just as responsible for the fluctuations in  
output as the fluctuations in output are responsible for the fluctuations  
of input. Those (like me) who have been trained to look at behavior in  
input-output terms tend to focus on inputs as the "start" of the control  
process; so it is natural to think of fluctuations in the CEV (the input to  
the control process) as the start of the control process, followed by comp-  
arison to a reference and, finally, generation of output. But, in fact, the  
control process has no start and no end -- it is a wheel of causation. What  
results from the operation of this causal wheel is control of one variable;  
perception of the CEV is kept NEARLY equal to another variable, the reference  
variable. The CEV is more like a dependent than an independent variable (where  
the term "independent variable" is typically used in the behavioral sciences to  
refer to the variable that "starts" a particular causal process). The fluctua-  
tions in the CEV, then, are not potential observations regarding the effects  
of disturbances (because these fluctuations are the result of BOTH disturbances  
and system outputs); rather they represent uncontrolled variations in the CEV.  
Unless the disturbances are overwhelming to the control system (as when you  
run out of hot water, so there is no amount of faucet turning that will produce  
warm water) the fluctuations in the CEV (even when they are very small) are  
the result of BOTH disturbance and output.

All of the above is said, not just because I think it bears frequent repetition  
(since it is the basis of what makes PCT revolutionary for psychology) but  
also because I suspect that it is the basis for Martin's example of  
"mutuality":

> Consider a second ECS (B), which has as its CEV-B some part of the variable  
> that disturbs CEV-A. ECS-B has no perception of ECS-A or CEV-A. It simply  
> controls CEV-B. But as a consequence of that control, the disturbance  
> to CEV-A is reduced, easing the control by ECS-A of its own perception.  
> Now suppose that CEV-A is part of the variable that disturbs CEV-B. Now  
> ECS-B has an easier job of control, which directly eases control exercised  
> by A. Each ECS in this figure-8 loop has a multiplicative effect on the  
> apparent gain of the other.

In fact, this situation (as described and shown in Martin's diagram) is  
virtually identical to the interactive control situations analyzed by  
Tom Bourbon and the coordinated control situations analyzed by yours truly  
(and described with icy clarity in "Mind Readings"). Also of relevance  
to Martin's example of mutualism is the talk given at the last CSG meeting  
on "Helpful control". In fact, the mutualiam shown byMartin's diagram  
is does not lead to a "helpful" interaction; the control actions of one  
system are resisted (as usual) as disturbances to the controlled variable.  
The control exhibited by each system in this interactive arrangement is  
actually slightly POORER then the control exhibited either system alone  
(I tested this quickly with a spreadsheet model).

There is a situation where I can imagine control systems evolving mutual  
dependence -- so that the controlling done by one system depends on the  
controlling done by the other system. Tom Bourbon showed a simple  
example of interactive (two person control) where the ability of each person  
to control a variable depended on the fact that the other person was also  
controlling a particular variable. Tom's was a simple situation but, I'm  
sure, one that has analogs in real symbiotic relationships between animals.  
But the symbiosis (cooperation) does not result from the helpful control  
proposed in Martin's diagram ("helpful control" being the situation where the  
outputs of one control system are thoutgh to reduce the effects of the  
disturbance to the controlled variable of another). There is no such thing  
as "helpful control" because it is impossible for any control system to  
reliably compensate for the disturbances to the CEVs of another; the only  
reliable way to compensate for disturbances (whatever their source) to  
CEVs is to monitor the perception of the CEV, continuously compare that  
perception to its reference specification and act continuously (in ways that  
are not perceptible to the controller itself) to "push" or"pull" that  
perception toward the reference.

Best

Rick

---

<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:** [October 13, 1993, 4:17pm UTC](http://discourse.iapct.org/t/mutuality/14358/3 "1993-10-13T16:17:53Z")

</div>

[Martin Taylor 931013 12:00]  
(Rick Marken 931009.1500)

Rick, I really think you should try to read more carefully before you post.

> > :A single ECS (A) controls its perception in the presence of disturbances to  
> > its CEV (CEV-A). It can neither predict nor directly observe these  
> > disturbances, except as fluctuations in the value of CEV-A.
> 
> A single ECS can neither predict nor directly observe these disturbances  
> AT ALL

Amazing how you take off over a point I was trying to emphasize as if your  
discussion contradicted what I was trying to say. The next two paragraphs  
simply reinforce my point.

> > Consider a second ECS (B), which has as its CEV-B some part of the variable  
> > that disturbs CEV-A. ECS-B has no perception of ECS-A or CEV-A. It simply  
> > controls CEV-B. But as a consequence of that control, the disturbance  
> > to CEV-A is reduced, easing the control by ECS-A of its own perception.  
> > Now suppose that CEV-A is part of the variable that disturbs CEV-B. Now  
> > ECS-B has an easier job of control, which directly eases control exercised  
> > by A. Each ECS in this figure-8 loop has a multiplicative effect on the  
> > apparent gain of the other.
> 
> In fact, this situation (as described and shown in Martin's diagram) is  
> virtually identical to the interactive control situations analyzed by  
> Tom Bourbon and the coordinated control situations analyzed by yours truly  
> (and described with icy clarity in "Mind Readings").

Well, you may be right, but it looked (and looks) different to me. I'm  
looking at why multicellular organisms exist, and why complementary  
cooperative structures have evolved to be so prevalent. There is no  
scintilla of "helping" in my diagram, since neither ECS can perceive any  
aspect of the CEV that corresponds to the other's controlled perception.  
BOTH act quite independently on controlling perceptions according to their  
independent reference signals, and it is only a strange vagary of the  
environment that lets an outside analyst see that there is some interaction  
between the two CEVs and therefore between the two control loops.

> In fact, the mutualiam shown byMartin's diagram  
> is does not lead to a "helpful" interaction; the control actions of one  
> system are resisted (as usual) as disturbances to the controlled variable.  
> The control exhibited by each system in this interactive arrangement is  
> actually slightly POORER then the control exhibited either system alone  
> (I tested this quickly with a spreadsheet model).

It seems to me that last year you presented a situation in which the opposite  
was true.

The result you get will be likely to occur when there is tight coupling  
between CEV-A and DIST-B and vice-versa (though not guaranteed). In the  
situation I described (though not in the diagram, because of the resulting  
confusion of alphanumerically drawn lines), CEV-A influences DIST-B. There  
are many other influences on DIST-B, but when CEV-A is well controlled,  
then DIST-B will have slower and/or smaller excursions. In the limit of  
tight coupling and high-gain control by A, DIST-B will stay almost constant,  
and control by B is almost unnecessary, other than to apply a constant  
output that opposes the force applied to CEV-B by DIST-B. But more often  
than not, the tightly coupled interaction of the two control systems  
will lead to some kind of oscillation, particularly if the two control  
systems have similar dynamical characteristics.

> There is a situation where I can imagine control systems evolving mutual  
> dependence -- so that the controlling done by one system depends on the  
> controlling done by the other system.

Oh, yes. There's a lot of that. But I was interested in a situation that  
seemed to me not to have been discussed. If it has been, there's no harm  
in seeing it in a different light.

> There is no such thing  
> as "helpful control" because it is impossible for any control system to  
> reliably compensate for the disturbances to the CEVs of another;

This sentence, more than any other in your posting, convinces me that you  
missed my point entirely.

Martin