Tom Bourbon [941209.0933]
[Jeff Vancouver 941208]
I probably should not make this post as it violates my self-set moratorium
of interacting on the net, but when a thought nags it can be hard to think
about other things.
So, you are trying to control your output. That's a pretty hard thing for a
perceptual control system to do! 
It is about the simple fever example that Bruce Abbott and Bill have
discussed. Bill described it as a nice example of a simple 2 level
system, which it seems to me is true. He is also leery of considering
truncated control systems (i.e., considering the subsystem without
reference to the related systems), which is the source of my question.
In the
fever example the levels include 1) the immune system whose input is the
detection of a foreign body of some type which a reference signal does not
want and whose output function is to reset one's internal temperature
reference signal and 2) the internal temperature system whose input is an
assessment of internal temperature and whose reference signal is the
aforementioned temperature set point. The question is what is the
nature of this second system's output function?
This is a nifty problem, Jeff. From what I have seen, the literature on
temperature regulation is not pretty. There some fairly clear
indications that a feedback control process is "involved," but there are
also lots of discussions about one-way reflex pathways and the like.
My guess is that we are dealinng with more than two levels. For our
purposes, we can lump "the immune system" into one intrinsic level, as you
say. After that, I believe things are more complicated. There is probably
another intrinsic level concerned with core body temperature, or sensed
temperature of blood in the core of the brain. We don't consciously
perceive the signals in that one. We probably consciously perceive
something more closely related to the rate of gain or loss of heat across
the skin. If that is so, we are not sensing error signals from the
core-control system, but perceptual signals from a more peripheral system
whose reference signal has been adjusted by the core-system.
The picture is complicated by the fact that the temperature control system
comprises two linked systems that serve to control perceptions relative to
the the same reference signal, much as paired muscles (e.g., extensors and
flexors) serve to control perceptual signals relative to refrence signals
in the motor system. In the temp system, the same reference signal for core
temperature must do something like split and go into a pair of comparators,
one where the reference signal is subtracted from the perceptual sigal for
sensed core temp, and one where the perceptual signal is subtracted from the
reference signal. In a system like that, a sensed core temp _below_ the
reference would would produce a _positive_ error signal out of one
comparator (call it the comparator for the heat gain system) and a negative
(but physiologically limited to zero) error signal out of the other
comparator (call it the heat loss system). A sensed core temp _above_ the
reference would produce zero error for the gain system and positive error
for the loss system.
Creatures such as we come with a set of standard output devices attached at
the bottom ends of the heat gain system (e.g., skeletal muscles) and heat
loss system (e.g., sweat glands). Among other effects, those output devices
affect heat flow across the skin, and that is at least a major part of what
we experience consciously as "temperature." That is a long way from the
(unconscious) perceptual signals coming out of cells affected by the
temperature of the blood in the core of the brain, and it is different from
sensing error signals out of those cells.
Further, the
perceptions of chilled and hot are relative. That is, the experience of a
chill only makes sense if we understand that the perceptual signal of the
temperature system is compared again the reference signal (which the
immune system set to a higher than normal level). Thus, the
subjective experience is of the ERROR signal, not the perceptual signal.
I thought we did not experience (consciously) error signals.
I think the slightly more elaborate system I described above at least
begins to get at this interesting problem.
One way out of this dilemma is to say that the temperature system is
intrinsic and that its output is to send an input to a parallel system in
the perceptual hierarchy. The input is translated to the perceptual signal
of "I feel cold," which is discrepant from the reference signal for that
system and is thus translated into behaviors like getting a blanket, etc.
I was thinking of _two_ intrinsic systems: a system that controls
perceptual signals that are analogues of blood temperature in the core (by
way of lower-level perceptual control systems that affect heat gain and loss
at the body surface), and an immune system that controls its perceptual
signals that are analogues of the presence of pathogens (by way of, among
other things, adjusting the reference signal on the system for blood
temperature in the core).
In this reply, I haven't even begun to talk about voluntary, inentional
actions that also affect perceptions of temperature. Things like adding or
removing clothing or blankets; opening or closing windows or doors; turning
on or off air heaters or coolers. Or some of the interesting things people
do just for the fun of it, like sitting in an excessively hot hot tub and
sipping too much wine, or sleeping nude on a glacier.
. . .
So my dilemma is that if I try to give the fever example as a simple
example of control systems and their non-intuitive consequences in terms
of subjective experience, I may get trapped if asked for more detail. So
Rick & Tom, here is an opportunity to tell me what an idiot I am.
I don't do things like that. If you thought I did it sometime in the past,
it was not my intent.
BTW, I have finished revising my paper on Living Systems, but have let the
copies sit on my desk. This public declaration is to help motivate me to
send them out to those on the net to which I promised it.
Good.
Back to lurking,
If you must. This time, don't stay away so long.
Later,
Tom
