[Fred Nickols (990307.1835 ET)] --
Okay; vacation's over, time to get back to work and, boy, was Chapter 7 work!
Chapter 7 is about first order control systems - intensity control.
As I read it, the central nervous system (CNS) is at the heart of things.
It is, however, buffered from direct interactions with the environment by
way of first order systems, ones that deal with intensity. On the input
side we have nerve endings and on the output side we have muscles and
glands. Schematically, it looks something like this:
The | | | | The
Nerve | Boundary | CNS | Boundary | Muscles and
Endings | | | | Glands
The first difficulty I encountered was with the equations on page 84. Try
as I might, I couldn't solve for p. Finally I figured it out. Mercy me;
my already strained math abilities were further taxed. Anyway, I finally
got it. More important, I got the point that the perceptual signal stays
at or near the amplitude of the reference signal or, as Bill writes, the
perceptual signal "tracks" the reference signal.
Then, on page 87, Bill writes, "Perception is controlled with reference to
the reference signal." Right about there I got a little confused. So, I'm
assuming that 'with reference to' in that sentence is equivalent to saying
"Perception is controlled in relation to the reference signal." If not,
correct my thinking.
At the beginning of this same paragraph on page 87, Bill writes, "There is,
however, one quality which is reliably controlled by the reference signal:
the perceptual signal." Now I'm really confused. I thought the perceptual
signal was controlled by behavior, that behaving kept perception aligned
with the reference signal. Here, I'm reading that the perceptual signal is
controlled by the reference signal. That sounds a lot like issuing a
command and having behavior bring perception into alignment with that
command. Is that correct? Somehow, I don't think so but I'm darned if I
can explain my way out of this predicament. Can we really say that the
perceptual signal is controlled by the reference signal?
On page 88, Bill writes, "There is the strong suggestion that the reference
signals come down saying, 'make it feel like this,' and a few tens of
milliseconds later the perceptual signals proceed back upward, 'feeling
like this.' As a side effect, forces are exerted on the external world."
I think I get the "side effect" comment, which is to say, at the level of
first-order systems there is no reference signal for an external condition,
only for internal conditions. Thus, any external changes are indeed side
effects. My question is perhaps getting ahead but it would seem to me that
if I want to pick up a book and move it from my desk to the bookcase, that
my perceptions are of the position of the book in relation to where I want
it to be and that any internal alignment of first-order reference and
perceptual signals could be viewed as the side effects of other controlled
variables. Comment please.
On page 89 it occurred to me that the neural "stuff" Bill was then citing
is now at least 25+ years old and, in many cases, older than that, which
leads me to ask of Bill: Has anything changed since then that alters your
thinking? If it has, I assume you've already updated your thinking in an
article or paper and could you point me to it? If not...well, Hmm.
Leading Questions
1. Can you perceive first-order effort-intensity signals? Try tensing
difference muscles. What is similar each time? (The amount of effort.)
I tried lifting upward the very heavy tile-topped kitchen table where I sat
reading Chapter 7 and making my notes. First I used my arm then my leg
(just above the knee). I cannot describe the "amount of effort" in ways
that allow me to compare them. What I can describe is what I would call
the "resistance" offered by the table (inertia?). Using that as my gauge,
I lifted first with my arm and then with my leg until the table began to
move. In both cases, what I would call the "weight" of the table "felt"
about the same. But I have no idea at all as to how this relates to
question 1 above.
2. Can you perceive the way in which a loud sound is like a bright light
or a pungent smell? How would each be experienced at the low end of the
intensity scale?
Again, I'm at a loss. I can imagine (and also recall) how a loud sound or
a bright light or a pungent smell "overwhelmed" my sensory apparatus and
caused me to wince, cover my ears, close my eyes, and hold my nose (and
breath), but I don't know how to compare those. At the low end of the
intensity scale I would imagine these stimuli are experienced as ordinary
perceptions or perceptual signals.
3. Can you raise and lower the total effort-intensity in an arm
independently of motion or position of the arm? Hold this book in one
hand. Can you vary the total effort-intensity without altering the net
upward forces supporting the book?
I think so. One way is to put my hand against the wall and exert pressure.
Effort goes up but neither the wall nor the arm moves. The muscles flex
and I lean into it but nothing budges. I can do the same thing by holding
the book in a fixed position and squeezing it. Nothing goes up or down but
effort increases.
4. In order for a sound to have a detectable pitch, it must have a
detectable loudness. Is the reverse true?
Ouch. This one made my memory and my head hurt. To be heard, sound must
have volume or loudness above some threshold level and it must also fall
within some frequency range (20 hertz to 20K hertz last time I looked).
So, any sound that can be heard must, as you say, have a detectable
loudness. Similarly, for a sound of any loudness to be heard, it must have
a detectable pitch or, no matter its volume, it won't be heard (although it
might well be felt).
Short answer: Yes.
5. In order for an edge to be visually detected, there must exist
detectable brightness. Is the reverse true?
Short answer here: No. "Edges," if I understand what Bill is talking about
are visual phenomena having to do with light reflected off objects. This
implies eyes open. So, I closed my eyes and played a flashlight over them.
I could detect varying intensities of light or brightness but no edges.
Again, my answer is, No.
What did I learn from Chapter 7? Well, the notion that the central nervous
system is "buffered" by first-order control systems is informative even if
I don't know what to do with that knowledge just yet. Another thought that
occurred to me is that intensity is the first level of knowing. There
might be something profound lurking in that but I don't know what it is
either (other than perhaps we are all much more tactile than we suspect and
that "tactile intelligence" -- if there is such a thing -- might be the
foundation for all intelligence).
In sum, coming away from Chapter 7, I have the sense that I have touched on
the foundation of signal processing by human beings but at such a basic
level as to be not yet terribly useful to me.
Regards,
Fred Nickols
Distance Consulting
http://home.att.net/~nickols/distance.htm
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