[From Bill Powers (951014.1400 MDT)]
Bruce Abbott (951014.1400 EST) --
Perhaps my last post, which crossed yours in the mail, will help resolve
our differences.
True as far as it goes. Yet, is there any reason to believe that
the control system by which I move my arm and the one my dog Muffie
uses to move her front leg might have something in common, not only
in their structural organization but also in their functional
organization?
Of course I recognize that there are similar structures and functions in
different species. I probably sounded as though I doubted that, but I
don't. The point is that what these structures and functions have in
common is not the behavior that they produce, but the fact that they
control similar sensory variables, tension and muscle length. That is
how the PCTer would approach them, while a neurologist would probably
say that what they have in common is the production of movements and the
support of reflexes. What you go on to build on these very basic
interpretations will be very different, depending on the basic concepts
you start with.
I'll bet the same control system, having the same anatomical locus,
initiated those actions in accordance with its error signal, and
that is the point being debated here, not whether the same control
system always produces the same actions.
Yes, but remember that the state of the error signal depends on what
disturbances are present and the state of the reference signal; there is
no "typical behavior" produced by such systems. Human's seldom scratch
behind their ears with a left toe.
One can't
conclude that there is some specific structure inside the organisms
that makes them both use the same method and hence get the same
result.
Yes, and that is precisely why one needs to observe both function
AND structure before one can reach any secure conclusions on the
matter.
But what functions will one be looking for? That will depend on the
theory of behavioral organization in which one believes. One person
might see the function of the eye as being to cause adaptive responses
to distant events. Another might see it as providing a representation of
the world to be controlled by actions.
Perhaps our difference lies in the degree to which we believe that
adaptive reorganization can restructure the functions of the brain.
No, the real difference, once all the side-issues and false trains are
omitted, is in what we consider to be the outcome of adaptive
reorganization. The PCT concept is that adaptive reorganization brings
perceptual variables under control as a means of maintaining intrinsic
variables near their reference levels. It is not to create objective
events or relationships in the environment; that is a side-effect.
Large numbers of assumptions? Now there's a vague referent!
Contrary to these principles? Which principles?
The assumptions, for example, contained in an expression like
"separation anxiety" and "imprinting." But this is already an old
subject; I think I have found a better way to talk about what is going
on between us.
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Best,
Bill P.