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Alife Digest Number 038
ALIFE LIST: Artificial Life Research List Number 38 Tuesday, September 11th 1990
ARTIFICIAL LIFE RESEARCH ELECTRONIC MAILING LIST
Maintained by the Indiana University Artificial Life Research Group
Contents:
re: Crystalization of Complexity
re: Crystalization of Complexity
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Date: Fri, 7 Sep 90 13:03 EDT
From: Jeff Inman <jti@ai.mit.edu>
Subject: re: Crystalization of Complexity
From: ashley@spectrum.cs.unsw.OZ.AU (Ashley Aitken)
Subject: Crystalization of Complexity
Date: Wed, 5 Sep 90 16:03:50 AES
In my thinkings about the brain, and other physical systems I became more
aware of how the complexity of physical systems seems to crystalize at a
number of different levels. For example, a complete understanding of the
brain seems not to depend on knowledge of the state of every atom bound to
it. The complexity of the brain seems to crystalize out into a number of
levels, the cellular being perhaps one of the lowest and maybe some sort
of symbolic or conceptual levels being amongst the highest.
My question then is, why does the complexity crystalize out so elegantly
like this?
I think you have an interesting observation. Since a cell seems to have a
certain unity of purpose or function to us, we might expect that it's parts
would exhibit some kind of organization that "crystalizes" when we consider
the whole cell. However, there are several things to consider. The systems
we study will be limited to those that we can perceive. In other words, what
about the system composed of the "billions and billions" of cells comprizing
the creatures of earth? What about the system composed of the organic molecules
all those cells are built out of, or exchange, etc. That may seem to just be
a higher level of crystalization, but there are all sorts of other systems that
are interwoven with these systems, which may render the idea of a hierarchy of
levels unrealizable. Or maybe we could just say that the organization is
multi-dimensional.
The temptation is strong to use Occam's Razor to weed out the "true" levels
of crystalization; those systems that are most complete and have the least
complex interfaces. But, remember that we are evolved systems ourselves.
The things that seem "simple" to us depend on our categorizations, on what
information our senses and instruments bring to us, and on what our (evolved)
brains choose to do with that information. How will we control for the
possibilty that Occam's Razor works best when Occam is shaving himself?
Jeff
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Date: Tue, 11 Sep 90 11:05:32 EDT
From: "David M. Chess" <CHESS@IBM.COM>
Subject: re: Crystalization of Complexity
In "The Blind Watchmaker" (I'm pretty sure it is), Dawkins
speculates along similar lines about the hierarchical
organization of evolved systems. His argument, which
I found quite convincing, is that hierarchically organized
things are (very roughly) less likely to break under
small perturbations, and easier to fix if they do
break. His analogy was to a watchmaker who makes
a complex watch as a number of simpler subassemblies;
if he messes up one subassembly, he only has to redo
that one, not the entire watch. In evolutionary
terms (roughly again), the fact that the function of most
low-level parts of the system is "visible" only from
within a single high-level part means that small
changes to the system are likely to directly change
only a small part of the system's behavior. If
the system were not organized hierarchically,
any change to a part would be likely to have
a large impact on the system as a whole (and
evolution would in some sense have a harder time).
Put the other way around, if a complex system is
organized so that small changes to inner parts
tend to cause only small changes to behavior,
then it's (generally? always?) possible to describe
the system hierarchically.
How's that for hand-waving? *8)
DC
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End of ALife Digest
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