Sorry for the long delay. I didn't catch up on the mail backed up from the
previous trip before I went away for another couple of weeks, and there are
about 170 messages still awaiting perusal. But this interchange is worth
a comment, since I disagree somewhat (and agree somewhat) with both Hans
and Rick. I'll cast this in the same form as Rick's response to Hans.
Marken queries noted ">>", Blom responses ">".
What would you say are the essential insights about human nature
that come from looking a people from the MCT perspective?
One: Learning comes before control. If learning does not succeed,
there can be no control. Babies. Schizophrenics.
Learning has to be done largely by evolution, and is continued by the
individual. Many animals can walk (fly, or whatever) immediately on birth,
hatching, larval emergence... Only in humans is a quarter of the life-span
devoted to learning how to control effectively within the social-physical
environment. For MCT this means that the _data_ for the models must be
fed into the appropriate storage before birth; for PCT it means that a good
part of the _structure_ of the hierarchy is inborn.
It seems far more probable to me that biological systems have evolved to
grow structures like the structures of their parents than that they have
evolved both to grow structures like those of their parents to serve as
memories _and_ to fill those memories with the same data as filled their
parents' memories at birth.
(But that's an article of faith rather than of fact.)
Hans's statement is the same for MCT and HPCT, but there is a profound
underlying difference between the two in the implications of that statement.
Using Rick's scoring method, I'd say the similarity rating between MCT and
HPCT here is about 2 out of 10 (Rick's score, 5).
2. Two: We are all different, because our circumstances (perceptions and
actions) have been different. Our "internal models", that say how we
perceive the world and what we can do, are partly innate (DNA pre-
scribed hardware), partly based on our individual history. Ask any
Here, Rick says:
The "internal models" in MCT are models of the
laws of physics, not perceptual representations of external variables. MCT,
therefore, has to predict that people who live in the same environment
would _have to_ build the same internal models of that environment or
they could not control at all.
This is incorrect, at least according to my understanding of MCT. The
"internal models" are models of what PCT calls "the environmental feedback
function," and possibly of the statistical characteristics of the disturbing
influences. Only, because there is no hierarchy, the environmental feedback
function is incredibly complicated in a one-level MCT system, so the models
must embody a _lot_ of situation-specific knowledge (such as the different
behaviours of the reaction to turning the steering wheel when the road is
(a) uniformly grey, (b) textured (i.e. gravelly), (c) dark and glistening,
(d) shiny (icy), (e) dark and matte....). In PCT, these situation-specific
differences in the environmental feedback functions show up as changes in
the reference values fed to the muscular systems from intermediate level
control systems that have reference values based on moderately complex
perceptions controlled at higher levels. Both MCT and HPCT systems that
have learned to control a car well on dark, matte roads are likely to crash
when first encountering a dark shiny (icy) road; both will probably perform
well by the hundredth such encounter (if they survive).
Similarity score 10. (Rick 5).
Three: Uncertainties play a major role in how we view the world, but
much less in how we act... A world view can be crazy or underdeveloped,
whereas the individual may still function pretty well in society. Just
look around ;-).
I'm afraid I don't understand this well enough to comment or to score. Rick
It seems to me that uncertainties play the opposite role in PCT as they
do in MCT.
They play a different role, but I don't think it is an opposite role. In
both cases, control is better, the lower the uncertainty of the disturbance
given the recent history of the perception.
Just so that my score can be compared with Rick's, I'll give a half-way 5
Four: There are a great many (sub)goals at any one time. Actions will
attempt to control for all of these goals at the same time, as far as
possible. This point of view pretty much dooms The Test ;-).
Up until the last statement things were going along fine. Since we have
successfully done The Test over and over again, any theory that says The
Test can't be done has real problems. Anyway, MCT and PCT certainly seem
to differ on this matter.
Here I agree with Rick, but differ on the score. The fact that Hans
misunderstands The Test has no bearing on the similarity between MCT and
HPCT. Score 8 (Rick 0).
Five: All subgoals serve one topmost goal. The question is: what is
PCT would say that many subgoals could (and probably do) serve several topmost
goals. We have also written models to show how simply and elegantly this
hierachical control of perception system can be implemented.
I'd say both statements are correct, except that the "topmost goal" seen
by Hans to be required is the evolutionary "goal" that one has in fact come
from an unbroken line of ancestors stretching back some 4 billion years.
The "goal" of passing on one's genes is not, however, a "goal" in the sense
the word in used in PCT discussions--the value of a reference signal. There
is no controlled perception of passing one's genes into a distant future.
One may hope for grandchildren, but that's not quite the same thing.
When one is comparing the individual control structures implied by HPCT
and MCT, Hans asserts that an MCT structure must have one single goal.
I'm afraid I don't see why, but have to accept his word. I don't see why
the MCT "goal" should not be vector valued, as is everything else in the
MCT system. Anyway, there is no limit to the number of top-level goals
in a HPCT structure, though there is a limit to how many can be simultaneously
satisfied (i.e. how many there can be without conflict).
Similarity score 0 (Rick 0).
Six: Control is best in a fully predictable world.
PCT and MCT agree here, but for different reasons. Still, the general
statement has to count as true for both theories.
Agree. Similarity score 10 (Rick 10).
Seven: Because the world is not fully predictable, it needs to be explored
continuously. Explorations reestablish the up-to-date-ness of the model.
PCT shows that no world model is necessary for control.
HPCT does not show this, as I mentioned at the top of this message. What
HPCT suggests is that no _explicit_ world model is necessary for control.
Rick has not addressed the question of exploration--a question that deserves
a whole long message or several, on its own. Without going into the reasons,
I believe that HPCT and MCT are very close here, though not identical.
Similarity score 8 (Rick 0).
Eight: Exploration and control require different types of action:
random versus "computable".
This is not at all like the PCT perspective. Exploration per se isn't
necessary to tune a world model becuase there is no world model.
I'm not sure what Hans means by "computable." As I understand MCT, the
building of a model requires both the ability to analyze the feedback
function and an ability to assess the statistical structure of the
disturbance waveforms. The first demands that control be relinquished
to some degree, "randomizing" the output _independently of the disturbance_
to see how the jittered perceptual signal correlates with the jittered
output; the second also demands that control be relinquished, at least
in the absence of a good model of the environmental feedback function,
so that the perceptual signal can be taken as a surrogate for the disturbance
(with good control there is very little correlation between the perceptual
signal and the disturbance).
Now, in an HPCT structure that has _not_ been well reorganized, control is
poor to nonexistent, and perceptual signals do correlate with disturbance
waveforms. When it has reorganized, and the perceptual input functions and
the output functions and linkages are such that control is good, there is
very little correlation between any of the perceptual signals and any of
the disturbances. It is during the period of poor control that reorganization
occurs; in Hans's terms, the output actions are "random" with respect to
the disturbances, which permits (MCT), or leads to (HPCT), learning
Similarity rating 6 (Rick 0).
Nine: Developing correct perception is much more important than
developing correct action.
This makes no sense from a PCT perspective. There is no such thing as a
"correct" perception. In order to control, we have to construct perceptions
that can be influenced in all relevant dimensions.
In HPCT, the overriding "goal" is that all the "intrinsic variables" are
kept within their tolerance limits of the evolutionarily determined
reference levels. To do this, some perceptual signals are controlled,
and one of the facets of reorganization (or of evolutionary "learning")
is to vary the perceptual input functions until the perceptual signals
being controlled have the side effect of keeping the intrinsic variables
under control. Far from saying that "there is no such thing as a 'correct'
perception," HPCT _insists_ that "developing correct perception is much
more important than developing correct action." But this may not be the
sense in which Hans meant it. I assume that it is, and therefore give
a similarity rating of 10. (Rick 0).
Ten: There are no "unused" perceptions. _All_ perceptions tune the
model, although some may be discarded AFTER it has been established
that they cannot be fit into the model.
PCT suggests that some perceptions are controlled; some are not.
I think Rick is talking about something different from Hans. In reorganization,
HPCT does what Hans suggests. Perceptual input functions and linkages
change according to the success that perceptual control has in keeping the
intrinsic variables under control. But in the hierarchy, there are, as
Rick says, perceptions that are not controlled--many of them, at any
specific moment--even though those perceptual signals may well contribute
to higher-level perceptions that _are_ controlled. In Hans's sense, those
"uncontrolled" perceptions are _used_ by the hierarchy. In HPCT, reorganization
tends to eliminate perceptions that are not used, simply because a random
change that eliminates them will not reduce the stability of the intrinsic
Similarity rating 9 (Rick 0).
Corollary of the above: All behavior is optimal.
I don't think there is a conceptual equivalent to this statement in HPCT.
If there is, I either don't understand the statement or I don't understand
HPCT. In HPCT, behaviour is what it is. It may not affect the controlled
perceptions as efficiently as other behaviour might do for the same hierarchy
of perceptions, and therefore might not be considered as optimal by an
analyst. But what does that mean to the hierarchy that exists?
Similarity rating 0 (Rick 0).
Another corrolary: Every second part of an optimal trajectory is
itself an optimal trajectory. The past does not matter
Well, this is pretty vague but, I've gotta admit that PCT leads to
the same conclusion.
Again I don't understand Hans. It's that word "optimal". If "optimal" means
that the model of the environment is only as good as it is, and the
behaviour based on the model is the reference against which the optimality
of the behaviour is judged, then both this and the previous corollary are
tautologies. If "optimal" means something else, I don't know what that is,
except for evolutionary success. Some control systems leave no
descendants, so they are not "optimal" in that sense. But we all came
from ancestors who did leave descendants, so our ancestors must have been
"optimal", I suppose, even if we are not.
I agree with Rick here. It's vague, but I understand "the past does not
matter" to mean that memories of the past are actually in the present, in
which case we have another tautology. It doesn't matter to a tautology
which view is taken of a control system, so I agree with Rick in giving
a similarity rating of 10.
Why, according to MCT, do people have problems?
People have to solve the riddle of how to live optimally.
In HPCT, "problems" mean that some aspect of control is imperfect, whether
it be of intrinsic or of perceptual variables. Imperfect control is often
due to conflict between control systems, either within the same body or in
different bodies. But Hans claimed that all behaviour is optimal, so again
I don't understand where the "riddle" is in learning to behave optimally.
Similarity rating a dubious 5 (Rick 0).
Why do people fight with one another?
Because one person does not understand how he/she can "control" the
other. A person is like a rock or a chain saw or a chemical plant in
that he/she/it can be controlled only if we get to know how he/she/it
functions...Fighting is suboptimal behavior.
Apart from the last sentence, which again seems to conflict with "all
behaviour is optimal", one _can_ construe Hans's statement as agreeing
with HPCT if one wants to. One can also construe it as being in direct
opposition to HPCT. So it is hard to assign a similarity rating. On the
assumption that to "control" another person is to act so that the other
person's actions advance one's own goals, Hans's answer is almost an HPCT
answer. The main different is that in HPCT there is no part of the
hierarchy that "understands how" it works. The "understanding" is
distributed through the structure. When one's actions serve to advance
one's own goals, the structure is less likely to change than when they
don't. And when at the same time one's actions serve to advance another
person's goals, the other person's structure is unlikely to change. So
collaboration is stable whereas conflict is not. The two people's systems
come to "understand" how to "control" each other.
Maybe that's what Hans means. If so, similarity rating 10 (Rick 0). But
that may not be what he means, and the similarity rating could go as low
What can people do to get along with others and themselves?
Build better models. Get to know others better.
That's very vague, but since the essence of MCT is the building of explicit
models, it's probably the best that can be done. In HPCT, the same effect
comes about by reorganization that happens more when conflict impedes good
control than when conflict is removed. Implicitly, then, the answers are
the same, since to "build better models" in HPCT translates into "reorganize
into a structure that controls better."
But, reversing field, Rick says:
PCT would say that this is
_exactly_ the wrong way to go. The first thing to do to get along with
people is to realize that people are control systems and that, therefore,
they cannot be controlled arbitrarily.
Rick is saying that PCT _requires_ the building of models. As I noted at the
top of this message, we acknowledge that models may well be used at the
upper levels of an HPCT structure, but in my similarity ratings I am
assuming that we have an extreme variant that does not use models. By his
own statement, Rick should have given a similarity rating of at least 8,
rather than the zero he did give. I give a similarity rating of about 7.
Ok. That's it for this group. There were a total of 15 answers; the
highest possible similarity score is, thus, 150. I gave MCT a total
similarity rating of 30 yielding an average similarity value of 2
out of 10 between MCT and PCT (assuming all answers are equally
My similarity ratings total 90 to 100 out of 150, or an average of around 6
out of 10.
MCT may be the greatest thing since sliced bread (I'll take the sliced
bread, thanks) but it is DEFINITELY not PCT.
Nobody said it _was_ PCT, and I prefer to slice my own bread, thank you.
But the implications of MCT are not as different from those of PCT as
Rick makes out.
Then again, maybe I don't understand MCT very well.
I can see from the message headers that there were several subsequent
postings on this topic, but it seemed to me worthwhile presenting my own
answers independently of whatever anyone else might have said on these
various issues. Sorry if my comments turn out to have been redundant.
Now for the rest of the 200 backed-up messages.