From: Crosby_M (CrosbyM@po1.cpi.bls.gov)
Date: Sat Oct 19 1996 - 17:35:00 MDT
On Wednesday, October 09, 1996 3:40PM, I wrote:
<has the following been discussed on the list ... the little-known
Spacetime Reductive Materialism (SRM) theories of consciousness proposed
by California PolyTechnic professor James Culbertson [discussed in Nick
Herbert's 11/94 book _Elemental Mind: Human Consciousness and the New
Physics_ >
On Sunday, October 13, 1996 2:35AM, Hara Ra replied:
<Not that I know of. Nick is an acquaintance of mine, and I've never
heard him discuss this (but neither were the circumstances appropriate).
Would you kindly provide a summary of this POV?>
I'll try, though it will be difficult to do without diagrams & flow
charts. Also, this is all second-hand (what you see in quotes below
will be from Herbert's book). I would really recommend Nick Herbert's
book to anyone interested in the mind. Herbert favors dualistic
approaches BUT he also provides one of the most comprehensive and easily
read discussions of the most cutting-edge theories of mind that I've
seen; and, _Elemental Mind_ is still available in most good-size U.S.
bookstores.
PREFACE:
This thread started with Hara Ra's mention of David Chalmer's recent
book _The Conscious Mind: In Search of a Fundamental Theory_, 1996 from
Oxford University Press. Like Chalmers, Nick Herbert starts with the
assumption that "The really hard problem of consciousness is the problem
of experience. When we think and perceive, there is a whir of
information-processing, but there is also a subjective aspect."
(Chalmers). Culbertson attempts to provide a physics-based approach to
modeling human experience and consciousness.
INTRO:
James Culbertson (JC) has worked on theories of robot & human
intelligence since the early 1950's when he was at the RAND Corporation.
In 1953, Culbertson left RAND for California Polytechnic in San Luis
Obispo, where he taught mathematics and computer science and even headed
the philosophy department. Most of what Nick Herbert (NH) describes
comes from Culbertson's 1976 book _Sensations, Memories, and the Flow of
Time_ (which is available from Amazon as a special order).
SPACETIME REDUCTIVE MATERIALISM (SRM):
"Einstein's spacetime model of external physical reality serves as
Culbertson's framework for describing internal psychological reality.
'Reductive', instead of 'emergent', because Culbertson believes ... that
consciousness permeates all of nature ... And finally 'materialism', not
'idealism', because ... mind is completely accounted for by movements of
matter.... Although all matter is sentient to some degree, most of this
awareness is of very low quality and is not functionally coupled into
matter's behavior in any important way." (p120) JC views the world "not
as unconnected particles in space but as interacting world lines in
Einsteinean spacetime." NH uses this quote from physicist Herman Weyl
to set the stage for JC's theories: "The objective world simply is; it
does not happen. Only to the gaze of my consciousness, crawling upward
along the life line of my body, does a section of this world come to
life as a fleeting image in space which continuously changes in time."
(p121)
SRM WORLDLINE DIAGRAMS:
To simplify discussions, JC's models assume that "the universe consists
entirely of two-body interactions". (Feynman?) diagrams are used to
represent events inside a conscious entity. Convergent (AND) junctions
happen when two events become correlated in memory and divergent (OR)
junctions occur when a world line splits. The current state of the
entity is the point R at the top of the diagram. "The elementary events
that spacetime point R perceives consist of certain divergent junctions
in its past called terminal breaks." All of the events leading up to R
are called R's "influence tree". When the tree is pruned at the
terminal breaks, we have what is called R's "outlook tree". "The
intensity of R's experience is measured by the number of terminal breaks
in R's outlook tree ... qualitative differences result from the
different ways in which terminal breaks are connected via the outlook
tree to the perceiving vantage point R." Euler diagrams are used to
visualize the organizational pattern of the outlook tree's terminal
breaks.
There are two types of significant loops in an influence tree:
disjunctions that later re-converge are called ZAGs; and, _clear loops_
are loops which have no breaks in at least one of their paths. The
breaks in clear loops are called ZIGs, and are never experienced. NH is
mostly interested in these 'clear loops' because, as he says, "The
perceptual transparency of a clear loop will, in principle, allow us to
build 'mind links'" (p126). "Culbertson's theory possesses the
attractive feature that it permits experimental access to the inner
experiences of other beings [through clear-loop links]." (p135)
THE SPACE-TIME HARD DISK:
"In SRM, a reminiscence [is] a partial re-experiencing of the event ...
your present vantage point connects up via a clear-loop link to the
actual moment in spacetime where that [event] is still eternally present
[and] is NOT recalled from some storage space in the brain ... memories
are never as clear as direct perceptions because the clear-loop link
connecting the past with the present becomes degraded with time,
acquiring extra breaks that make the clear link less transparent and
more cluttered with other memories.... [However] unconscious memories
such as muscle skills are probably stored in the brain in more
conventional ways ... the unconscious data rate in the human brain is at
least a trillion times larger than the conscious rate ... Coexistent
with this unconscious mechanism, part of the brain acts as a sentient
subsystem, an intricately woven spacetime tapestry stretching back into
the past with caterpillar circuitry to simulate the flow of time and
memories that are not located in the brain at all but far back in the
past where/when they first happened." (p132)
CONCLUSION:
My previous post pointed out the evolutionary advantage of this
'space-time hard disk', IF IT EXISTS! As NH points out: "Culbertson's
SRM model of mind seems to have two major problems ... [First] in the
midst of such a pandemonium of awareness, why do our minds feel so
unifed? ... [Second] the link between his abstract awareness algorithms
and actual neural or silicon hardware remains somewhat unclear....
Although it is still too abstract to be applied to actual neural nets,
Culbertson's consciousness model is not a mere vague, verbal philosophy
of mind but a clear-cut engineering description of the (possible) state
of affairs at the mind/body interface."
This assumes that there *is* a dualistic mind/body interface, rather
than an integral system. I have a hard time with this notion that
"memories are not located in the brain at all". I'm also skeptical that
'clear loops' could be useful for building "mind links" between two
conscious beings. It seems to me that if clear-loops are 'transparent'
then neither participant would ever realize they are sharing a common
experience.
Still, the influence-tree, reflection point, and outlook-tree model
seems like it could be a useful starting point for algorithms that
simulate human memory and experience.
Mark Crosby
This archive was generated by hypermail 2.1.5 : Fri Nov 01 2002 - 14:35:48 MST