[From Bill Powers (980209.2010 MST)]
Turns out I was kicked off the list some time last week. I'm signed up
again, and will just reply to a few highlights.
Martin Taylor 980201 10:40
The "observed relationship between inputs and outputs" is the action
of the subject that indicates the subject saw or did not see (hear, taste,
smell...) something when a real physical "something" is known to have
been available to see (hear, tast, smell...). You seem to be saying that
whether the subject can taste salt at a concentration of x per million
is a characteristic of the environment, not of the subject. If that is
so, you might explain what it is about the environment that does the
tasting and allows the subject to act according to whether the evironment
tasted the salt or not.
There is an observable relationship between the concentration of sodium
chloride and a statement "yes/no, I can/can't taste something salty."
However, we do not know what, in the environment, corresponds to the taste.
Whatever it is, it is also affected by magnesium chloride and several other
substances, and the presence of sugar can alter it, too. The missing factor
here is the relationship between salt concentration and whatever it is that
corresponds to the salt-sensation.
A comment on Standard HPCT and perceptual functions.
According to "Standard" HPCT, the hierarchy consists of a series of levels
of elementary control units (ECUs). Each ECU contains an input function
that accepts possibly many inputs from the sensors or from the outputs
of lower level ECUs. The output of an input function is a perceptual
variable. The sensors transform some physical variable in the environment
into a signal value suitable for input to an ECU input function.
Perceptual variables are therefore functions of physical variables.
This is true, but they are not _single-valued_ functions. You may be
shooting for an 8, but your reference-level for eight-ness can be satisfied
by 6 and 2, 7 and 1, 1 and 7, or 2 and 6 on the dice.
According to "Standard" HPCT, the form of a perceptual input function is
determined by reorganization, which in turn depends on the degree to which
intrinsic variables are controlled to be near their inborn reference
levels. This implies that the perceptual input functions of (at least)
low-level ECUs change slowly, if at all, over time. Hence, again according
to "standard" HPCT, there should exist functions that relate the values
of perceptual signals to the values of physical variables.
Yes, but I repeat that these functions need not be single-valued. Neither
do they have to be stable over time. Furthermore, the relationship between
physical variables in the environment and intrinsic variables is highly
variable -- how many ways are there to stay warm? The environment has far
more degrees of freedom than our perceptions do, and far more than are
monitored by the reorganizing system. So there is no unique relationship
between intrinsic variables and the perceptual variables we learn to
control, or between either class of variables and those we call "physical"
I happen to believe that Standard HPCT is inadequate in this linkage
between perceptual and physical variables, and I said so. There are many
reasons why I think it inadequate, based on the results of "conventional
research", some of which I have mentioned in previous messages. Bill P
agrees with me that it is inadequate, for the same reasons (980130.0517
MST) "I can reproduce the same perception I had before, but there is
no guarantee that in doing so I am producing the same situation as a
physicist would deduce it."
I don't see how this comes out with Standard HPCT being inadequate. For me,
this is an insight into the nature of perception. We make our perceptions
repeat, but this does not imply that we make the physical reality which
underlies them repeat. Why do you see this as an inadequacy in HPCT? What
would an adequate theory say? And when did I agree that this observation
represented an inadequacy of HPCT?
Most psychologists know this, from the results of "conventional"
psychophysical studies, but so far as I can interpret Bill's message,
his agreement is based on his powerful intuition, since to him the
results of non-PCT experiments are inadmissible.
How do they know this? Psychophysical studies can't tell you the
relationship between a physical stimulus and a given perceptual signal.
They can tell you that when a given physical stimulation gets small enough,
a person will report that some aspect of experience has disappeared. They
can't tell you what perception is being caused by the physical stimulation,
or whether it is that stimulation or some other variable that depends on it
that is involved.
Since I don't think I ever agreed that the statement you cite constitutes
an inadequacy of HPCT, this paragraph is meaningless.
I don't think I ever said that the results of non-PCT experiments are
inadmissible simply because of not being PCT experiments. Surely you can
see why I would be skeptical if someone said he had measured the response
to a stimulus, if no attempt had been made to see if the subject was in
fact perceiving that stimulus or only something dependent on it. As far as
I know, the Test is the only way to do this, so any experiment that doesn't
include something equivalent to the Test would be inadmissible -- in any
court, not just the court of PCT.
The ways in which a fixed function relating a perceptual signal to
physical variables is inadequate (according to "conventional" studies
can be summarized in the oversimplification that the output of the
sensors (and by extension the output of any perceptual function) is
dependent on the context extended over time.
This depends entirely on what you think of as the perceptual function and
its mathematical representation. If the mathematical representation is a
constant multiplier, but the actual physical function adapts over time or
exaggerates changes, then the mathematical representation is incorrect. A
correct definition of the perceptual function would include time-dependent
parameters. Likewise, if context matters, the perceptual function has to
include terms that change when context changes: in other words, the initial
definition of the perceptual function did not include enough input variables.
I have added that it is
possible that the output of the perceptual input function of an ECU
may depend on whether that ECU is actually controlling the perception
at the tested moment--but this addition is purely intuitive, and is made
largely to warn people further against taking seriously the results
of experiments that purport to "measure" the magnitudes of perceptual
It may depend on the phases of the moon, too. If it turns out that other
variables influence the measure of the controlled variable, then obviously
those other variables have to become part of the definition.
Your definition of a "fixed" function is what is creating the problems you
mention. It was never my intention to define functions that way.
Anyway, the upshot is that I think that (as a minimum) experiments that
put a bound on the ability of people to perceive changes in a perceptual
variable are useful to PCT.
Yes, that would be useful -- provided you can show what perception is
influenced by changes in a physical variable. My point is that
psychophysical experiments do not do this. You still have to ask the
subject what is being perceived, and the subject can only try to tell you
in words. At least, using the Test, you don't have to use words.
Later, replying to Perper:
What you are pointing out is what I have pointed out elsewhere, and Bill P
has pointed out many times--one cannot define a present set of physical
variables that specify a present perception, except in the simplest cases.
History matters, and current context matters.
What I believe is that neither history nor context matter, unless the
perceptual function is specifically organized to take them into account. My
point is that you don't _need_ to define a present set of physical
variables that specify a present perception. All that matters to the
organism is controlling the perception. Even the variables controlled by
the reorganizing system are not related uniquely to any physical state of
affairs. The reorganizing system wants to stay warm; it doesn't care
whether this is done by moving to Southern California, burning the
furniture, buying Inuit clothing, or sitting next to a nice warm spent
reactor rod. There are far more ways to correct errors than there are
errors to be corrected (a few of which prove to be mistakes, of course).
Jeff Vancouver 980202.15:30 EST--
(Commenting to Martin Taylor)
You (or others) may object to my use of the word prediction in introducing
this last paragraph, but that seems an apt word as the gunner (or radar
system) predicts where the target will be when the shell is on a plane
perpendicular to the target. Prediction is required to deal with the lag
in the system (due to the physics of shell travel). And this discussion is
required to counter the "too slow" argument.
The world needs to be "predictable" in the sense that the same action will
have the same direction of effect on the controlled variable, and any
disturbances will be limited in magnitude and speed. This predictability,
however, is not involved in "making predictions." It's merely a statement
of what is required for a control system (or any fixed design) to continue
working in a given environment. It's necessary to be able to predict that a
meteor is not going to destroy the control system before it can act, but
this doesn't mean that the control system works by calculating the
probability that a meteor will strike in the next x seconds.
As to whether any prediction actually occurs in firing a gun at a moving
target, this depends on the individual or on the designer of the radar
control system. When I learned anti-aircraft gunnery in the Navy, I was not
told to make any predictions of target movements. I was told to try to get
the stream of tracers to intersect the target, or alternatively (when not
using tracers) to keep the target on the "appropriate" ring of the sight.
Both strategies involved control of present-time perceptions, not prediction.
Fire-control radar (in WW 2, where most current myths about control theory
originated), however, can't see the speeding projectiles, so it can't
estimate miss distances. The only possible improvement over blind firing,
then, is to try to estimate an aiming direction that will end up in a
collision between the projectile and the target. If this really worked
well, there would be a ratio of one projectile to one target, but of course
the actual ratio is thousands, or hundreds of thousands, of projectiles to
one near-enough miss.
What needs to be predictABLE is the effect of action on input, although
this doesn't mean that this effect must actually be predicted by the
control system. What does NOT need to be predictable OR predicted is the
presence, amount, or direction of disturbances that can alter the
controlled variable independently of the system's action. Those, provided
they are not too violent, can be taken care of without prediction. Of
course if they are too violent, the control system will fail, however it is
Dan Miller (980204.1645) --
For example, there exists a statistical relationship
between amount of reading (IV) and political progressivism (DV)
(r = 0.62 and it has been replicated). To me, this is very
interesting. I wouldn't want to argue from this statistical
relationship to a full-fledged theory, but how do we explain it.
How do you explain what? The fact that the correlation is only 0.62? That
one's easy: this fact is false for almost as many people as it is true. The
underlying statement (more reading goes with progressivism)? That's even
easier: the statement of fact is wrong too often to allow it in to any
scientific discussion. If your conclusions depended on two facts like that,
they would most probably be false.
So,how do we make sense of this intriguing finding?
What is it about the act of reading (and reading a lot) that creates
a context within which progressive political ideas can generate and
The problem here is that you're trying to generate a general reason for
this finding when it's not generally true. Also, you're doing exactly what
users of statistics claim they're not doing: assigning causality to a
correlation. How do you know it's not progressivism that leads to more
reading? How do you know that this trend doesn't simply reflect the fact
that there are more avid readers of the New Republic than avid readers of
Soldier of Fortune?
No matter what explanation for this "fact" you come up with, it's going to
predict incorrectly in a very large number of cases -- not just now and
then, but almost half of the time. In my book that makes it pretty useless.
Some of the discussion on this list is about control systems and not
living control systems. A little engineering can go a long way, but
it is ONLY a metaphor, right?
No. Absolutely not. It is no more metaphorical than saying that the heart
is a pump. The heart IS a pump: it pumps. People ARE control systems: they
control. The engineering analysis of closed-loop systems tells us
literally, not metaphorically, the laws governing such organizations.
Control theory deals with facts of nature on the same levels that physics
deals with them.
All metaphors are equal, but some are more equal than others.
A few of us are
interested in social interaction. It's not always easy to do the
test in such circumstances. It's not always clear how it is done in
your controlled situations.
If you understand how to do the Test, it's very easy to do under any
circumstances. You don't have to create big disturbances; all you want to
know is what changes in the environment result in actions that oppose the
changes (successfully). You don't have to keep anyone from succeeding at
control. The test works best when the person controls as perfectly as
possible all during it. This is why ALL pct experiments involve the use of
disturbances, and why the disturbances are always constructed so they are
easy to resist. Every PCT experiment is a continuous Test for the
For example, can your experiments and
demonstrations be done without prior instruction (that damned social
stuff, again)? Is there a need to inform people what they are going
to be perceiving, and what they want to perceive? This is a very
troubling question is it not?
Not to me. We don't need to communicate verbally with anyone to do the
Test. If we have enough time and equipment, we can wait for natural
disturbances to occur, and make and test reasonable guesses about
controlled perceptions with no interaction between us and the observed
person. In fact it's through watching what people naturally control that we
get our ideas for instrumented experiments.
If we wanted to, we could just go around observing people controlling
things. But when we think we see something being controlled, we naturally
want to get a closer look, and that calls for instrumentation and
simplification of the circumstances. Of course then we have to explain what
we are asking the person to control. The instructions are usually very
brief: use that mouse to keep that object on that other object, or to keep
this sound the same, or to make this object look like that object. We don't
tell anyone HOW to do that. How they do it is what we want to measure.
The only behavior that people can produce under any conditions is very
simple: push, pull, twist, and squeeze. That's it, there ain't no more. All
the rest of what they do is concerned with controlling perceived
consquences of pushing, pulling, twisting, and squeezing. So a simple
tracking experiment has all the same elements of behavior we see in any
context; the main difference is in the kinds of perceptions we see being
controlled. For practical reasons we have to use simple perceptions that we
can show on a computer screen (and that, with our limited abilities, we
know how to program). Plus, of course, the fact that we're limited to the
visual mode with a few forays into sound, and one or two controllers at a
time. But that's not a limit in principle, only in practice. Give me a
virtual-reality setup and I'll give you control experiments with much more
Instructions simply describe to the other person a temporary goal which we
ask be adopted. Their exact wording is unimportant; we can quickly see if
the person understood what to control, which almost all participants do. We
could dispense with instructions about what to do by asking the person to
discover what the apparatus does. But that would be studying something else.
We could also ask the person to experiment with the apparatus and pick out
something to make it do. It wouldn't matter to us what the person selected;
we can measure the parameters of any control behavior that we have
quantitative data about. It's not as if some things people would do would
be control behaviors, while the rest would be something else. Everything
the person does would be control behavior. We don't have to tell people to
perceive or control; they never do anything else.
Martin Taylor 980206 00:20 --
Now I play you a snippet of Mozart and then a snippet of Hendrix. You say
"the first was Mozart." I do it again, and you say "the second was Mozart".
After I have played you 100 pairs of snippets, sometimes playing Mozart
first and sometimes Hendrix first, you have told me 100 times
correctly which one was Mozart. I conclude that you can discriminate
pretty well between Mozart and Hendrix with the duration of snippet I used.
This tells us that you can give responses that agree with our opinions
about the source of the music. It doesn't however, tell us anything about
what you're actually perceiving that allows you to give these "correct
responses." The distal stimulus is identified; the proximal stimulus