[Martin Taylor 2018.03.05.10.51]
Thanks for the vote of confidence, misplaced as you may think it
after this one, which I offer having read no more than the first two
paragraphs of the Hart paper. This answer is about energy usage in
control, which I think has implications for the issue you raised.
That’s why I changed the subject line.
The fundamental physical fact that allows control is the flow of
energy that can carry entropy from a concentrated source (food, the
sun, radioactivity, for example) to a more diffuse (high-entropy)
sink, typically waste products and heat. By exporting entropy, it is
possible for the system to keep its own entropy relatively low and
extract entropy from distinct parts of its environment. This is all that your kitchen refrigerator does. It accepts energy
from (usually) the electrical power grid, extracts some entropy from
its interior, enough to bring the interior temperature to a
reference value set by you, and exports the extracted entropy in an
energy flow to the room in the form of heat. Heat is also generated
in what we might call “administrative functions” such as the
friction of a pump and other moving parts. When you put newly bought
food into the refrigerator, it is hotter than the reference
temperature, and tends to equalize its specific entropy level with
that of its new, cold, environment, heating the environment and
producing a disturbance to the thermostat’s controlled temperature
perception. The fridge extracts that added entropy and exports is,
generating a bit more heat in the process.
From the viewpoint of energy and entropy, an organism (any living
organism) does the same. Its interior is at a generally lower
entropy than that of the surrounding environment. In other words, it
has more structure than the environment, but it is vastly more
complex than a simple refrigerator, and controls more variables.
Warm-blooded animals export heat, perhaps simply from the skin by
radiation or conduction, but often by producing sweat that can
evaporate, extracting the latent energy of evaporation in the form
of the vapour, which is a loss of moisture to transport the entropy
away from the body.
In control, one can usefully partition energy use conceptually into
two components, which I label, for lack of better words,
“administrative” and “effective”. The “effective” use of energy is
that which actually changes the value of a controlled variable or
that opposes the influence of a disturbance. In the latter case, the
effect is the same as when you load warm food into the refrigerator:
the extraction of entropy the disturbance adds to the variable
(which is a rather fundamental reason why control can never be
perfect) and hence from the internal controlled quantity (the
perception, in PCT). “Administrative” energy is that used to drive
the refrigerator’s machinery, or the body’s control system elements.
So long as nobody changes the contents of the fridge, its
temperature in the absence of control would slowly change until the
internal entropy level matches that of the room. In other words, the
food stored there would warm up and the microbes and fungi would
quickly increase the entropy of the passively stored food. To make
the food edible again would take a lot more work than simply
reducing the temperature, and in practice, most refrigerated food
gets thrown out after a prolonged power outage, and is replaces by
fresh (low entropy) warm food that takes a lot more administrative
and effective energy to bring back to its reference temperature than
it would have taken to keep the original food near the reference
temperature in the first place.
Now consider the organism. Since the question was about animals, and
I think warm-blooded animals, I will limit the discussion to them.
What is happening inside a healthy animal? Let’s start at the
smallest component, a bacterium in the microbiome. If I remember
correctly, we contain a couple of orders of magnitude more bacteria
that we have body cells, and we can’t live without them. They
dispose of some cellular waste and produce useful products as their
own waste. They compete and cooperate in a stable community of
control systems that keep their individual controlled variable
levels more or less near their reference values, using little energy
to do so. As a result, our cellular systems maintain reasonably
stable homeostatic loops, with any relevant biochemical and other
control systems keeping their controlled variables where they should
be without using too much administrative energy.
All these internal control systems continuously use energy, even if
it is at a relatively low rate, and that energy must be exported,
carrying the entropy they extracted. Our microbiome and cellular
processes export both waste and heat into the body, and even a
healthy animal must export those further to the outer world. It can
do this only by reducing the entropy of its environment, the
province in which we usually consider perceptual control. We control many variables in our interactions with the environment,
but to control each uses both administrative and effective energy
that generates heat that must be exported, carrying the entropy with
it. The more successfully we control them, the less heat we need to
export (which, incidentally, is a good reason why hierarchical
control systems are energetically favoured). So we eventually have
the old English school motto “A healthy mind in a healthy body”.
But what if the animal is “sick”. Then from outside, we observe what
Hart says in the opening paragraph of the paper Alex cited: ===========
···
On 2018/03/5 10:44 AM, Alex Gomez-Marin
wrote:
Youare right, Martin. I value your answers and I could have been
more detailed in my questions.
-
Animals that are acutely ill with systemic protozoan, bacterial
or viral infections are typically described as depressed and
lethargic with little interest in eating food and drinking water.
A little later in the course of a disease they commonly show signs
of dehydration along with indications that they have lost interest
in grooming since they develop rough hair coats. These behavioral
signs generally accompany a fever response and, together with the
occurrence of fever, are recognized by animal handlers and
veterinarians as signs that an animal is sick or is becoming sick
with an infectious disease.*
On Mon, Mar 5, 2018 at 4:20 PM, MartinTaylor mmt-csg@mmtaylor.net
wrote:[Martin Taylor 2018.03.05.10.12]
On2018/03/5 5:35 AM, Alex Gomez-Marin wrote:
Again,fair answers in general, but when
the rubber meets the road… I mean in the light
of this paper (attached). The idea that, when
fever quicks in, animals shall display some
behaviours that are typically and clearly
characteristic of sick animals, and that those
behaviours are not simply by-products of shitting
going on but actual adaptive strategies to cope
with the infection. But again, I can’t expect more
than a bunch of emails re-quoting the ten
commandments… Agh…
Why would you expect that? I ask this in thespirit of your enquiry about sickness “behaviour”, except
that here we have a specific instance of “expectation”,
which might be amenable to a specific analysis.Had you quoted the first paragraph of the Hart paper alongwith your original question, you would have given the
CSGnet community something to chew on. Now we have the
opportunity to see what you are asking, and an
understanding of the question offers a possibility that
some answer(s) may be forthcoming. Maybe I will have an
idea, maybe I won’t. But at least I now have an
opportunity to be relevant.Martin