arguments for all seasons

[Ken Miller]

With respect to the great NN/AI/Neurobiology debates:

While history serves as a guide to some of the possibilities of the future,
it by no means limits them.  Furthermore, one can within history find
examples to suit most prejudices.  Some examples:

(1) In the late 1800's some scientists conceived the beautiful idea that the
fundamental physical entities were vortices in some medium.  It seemed
tantalizingly as though such a program could explain all of physics.
Working seriously on this idea, a full mathematics of vortices could probably
have been developed, albeit one that would always have had some major
difficulties in explaining reality.  Without experimental studies of atomic
physics there was no chance of anyone inventing the real explanation,
quantum mechanics, through pure thought.  Score one for the neurobiologists.

(2) The thermodynamics/stat mech example.  An extremely good science of
gases, liquids, etc. (thermodynamics) evolved from observation of those
things without any knowledge of the underlying atomic and molecular
physics.  When consideration of atomic level things led eventually to
statistical mechanics, it was possible to derive thermodynamics from stat
mech; but nobody would ever have found thermodynamics from stat mech alone;
knowledge of the laws at the thermodynamic level was needed to find those
laws within stat mech.  This phenomena of finding the higher-level laws in
the lower level ONLY through guidance by prior knowledge of the higher-level
laws has occured repeatedly in modern physics.  Score one for the NN and AI
types --- but only if they are strongly guided by the phenomenological,
empirical study of intelligence, perception, motor behavior, or whatever
they are modeling.

(3) Heredity, like intelligence, was once a great soupy mess.  People had
lots of complicated, dynamical ideas of how it was accomplished.  Detailed
study of the biology finally led to a simple structural explanation --- the
structure of DNA --- that was largely unanticipated (yes I know about
Schrodinger -- who anticipated certain things in an abstract way but not in
a way that enabled any useful understanding of heredity).  Score one for the
neurobiologists.  On the other hand, many details of heredity --- i.e.
genetics --- were worked out without this molecular-level knowledge,
including Barbara McClintock's ``jumping genes" (a discovery that was not
widely acknowledged until a molecular-level explanation was found 20 years
later, at which time she finally got the Nobel prize).  Score one for those
studying at a phenomenological level.

(4) Einstein took a pre-existing mathematics, essentially differential
geometry, and applied it to the invention of general relativity.  Similarly,
modern field theorists have found the largely preexisting mathematics of
knot theory to be crucial to the understanding of superstrings.  Score one
for those who believe development of mathematical tools in
non-neurobiological contexts may aid neurobiologists.

(5) Many aspects of modern mathematics were first invented by physicists
trying to solve particular physics problems; later they was cleaned up,
rigorized, and generalized by the mathematicians.  Score one for those who
believe the mathematical tools relevant to neurobiology may only be found
through attempts to model neurobiology.  Although, note that many of these
tools were developed in studying "toy" models that at best only caricature one
aspect of the real physical problem.  So score one for everybody.

I could go on and on.  We could all go on and on.  There's enough history
and abstract arguments for everyone.

Personally, I hold these truths to be self-evident:

(1) Intelligence, like quantum mechanics, is too strange, difficult, complex
or what-have-you to be understood by pure thought alone.

(2) Insights into intelligence will come both from studying it at its own
phenomenological level, and by studying the physical structures (i.e. the
brain) that are known to realize it.  Personally, I'm putting my bets on
studying the brain, but that's just a personal decision.

(3) Development of toy models is useful to neurobiologists.  Until
connectionist models came into being, no one had a solid, non-vague,
working model of how a parallel distributed system might represent and
transform information.  Since experiments are necessarily framed in terms of
whatever concepts and metaphors are at hand, connectionist models have had
and will continue to have an important influence on systems neurobiology.
This does not mean that the toy models are necessarily biological, only that
they usefully expand the thinking tools available to the working
neurobiologist.  [on the other hand, the lack of relevance of the
DETAILS of these models to the neurobiologists is suggested by the 
great lack of working neurobiologists on this net.]

(4) Neurobiology is useful to NN/AI types.  Again, not too many of the
details at any point in time are considered by the NN/AI types, but the
overall progress of neurobiology leads to ideas that are important to those
trying to engineer or theoretically understand intelligence.

(5) Insights and influences will run in all possible directions, and no one
can predict for sure what will turn out to be useful to who.  We all place our
bets by the work we choose to do.

(6) None of us have the foggiest idea how the brain, or real intelligence,
works.  Therefore, we would all be wise to be humble and to listen well.

Ken Miller
ken at descartes.cns.caltech.edu