Chris Kitzke (960517.1705 EST)
<<Bruce Abbott (960517.1445 EST)>>
<<However, it seems that subsequent data did not appear to fit readily into a
control-systems framework, and before long a concensus seems to have
developed that the classical control system does not provide a useful or
compelling account of either feeding or the stability of body weight.>>
Sounds like you are trying to fit data to a theory after the data is taken.
Would it be better to conduct an experiment with the theory first, then see
if the data fits, rather than looking at data and seeing what theory explains
it?
Perhaps the internal control variable changes? If you think rats are
different than humans, then I suppose that it might be accurate to say that
the external environment changed the rats' "wants." If you believe rats
behave like humans, then you might say the rat changed it's own reference.
<<Wirtshafter and Davis present an alternative model that nicely accounts for
these data and also for data which they believe pose difficulties for the
control-systems model.>>
Again, I ask whether it makes sense to present a model after the fact, to
account for data. My understanding is that we obtain knowledge by first
developing a theory, then observing data, then learning whether we perceive
that theory to be right or not. I believe PCT because at the time I am
observing behavior, I believe it to explain what people are doing. Taking
perceived behavior with no theory at the outset then trying to figure what
the theory might be leads to the possibility that any theory could be argued
as the real thing. Example: with no theory and only observation, I could
reasonably argue that the sun revolves around the earth. Am I making sense
here? I am certainly trying with fine people who have studied PCT more
thoroughly than me.
[from the study]
[When the food is bitter, rats eat less and lose weight, but will defend
against disturbances to the new, lower weight. A similar thing happens when
food of high palatability is offered, with weight increasing to a new level
but defended at that level. To describe the operation of this system, the
authors introduce a new term: "settling point."]
A little confusing to me, but seems like there may be more than a singular
settling point. Don't know how that might change, externally or internally
controlled, but if I were conducting the experiment, I would theorize this
from the outset.
[... the postulation of a neural set point is not necessary to account for
weight control. The fact that a given quantity is, under some circumstances,
maintained at a relatively constant value does not by itself imply the
existence of an internal reference value.]
What would account for the existence of an internal reference value? Might a
theory on this help?
<<So there you have it: the concept of set point is unnecessary; body weight
may be determined more by external (stimulus) factors than by internal set
points.>>
Sounds like you support the conclusion (perception) of this team. Also
sounds like it is not one or the other. Both external an internal stimuli
must be at play.
<<But wait. Does Wirtshafter and Davis's argument make sense?>>
Not to me, it doesn't. Seems their want was to discount a theory based on
perceived behavior after the data was collected. Of course, I wouldn't know
that without asking them.
Well, I hardly ever post here, but was interested in this one. Keep up the
good work, folks, and forgive me if I sound ignorant or uninformed here.
Really just wanted you all to know I have been watching the net with
interest, and haven't gone away.
Have a nice weekend,
Chris