kahn%UCLA-CS@sri-unix.UUCP (02/05/84)
From: Philip Kahn <kahn@UCLA-CS>
In response to Rene Bach's question whether "the brain is a parallel
processor." There is no other response other than an emphatic YES! The
brain is comprised of about 10E9 neurons. Each one of those neurons is
making locally autonomous calculations; it's hard to get more parallel than
that! The lower brain functions (e.g., sensory preprocessing, lower motor
control, etc.) are highly distributed and locally autonomous processors (i.e.,
pure parallel data flow). At the higher thought processing levels, however,
it has been shown (can't cite anything, but I can get sources if someone
wants me to dig them out) that logic tends to run in a serial fashion.
That is, the brain is parallel (a hardware structure), yet higher logic
processes apply the timing of thought in a serial nature (a "software"
structure).
It is generally agreed that the brain is an associational
machine; it processes based upon the timing of diffuse stimuli and the
resulting changes in the "action potential" of its member neurons.
"Context" helps to define the strength and structure of those associational
links. Higher thinking is generally a cognitive process where the context
of situations is manipulated. Changing context (and some associational
links) will often result in a "conclusion" significantly different than
previously arrived upon. Higher thought may be thought as a three process
cycle: decision (evaluation of an associational network), reasonability
testing (i.e., is the present decision using a new "context" no different
from the decision arrived upon utilizing the previous "context"?), and
context alteration (i.e., "if my 'decision' is not 'reasonable' what
'contextual association' may be omitted or in error?"). This cycle is
continued until the second step -- 'reasonability testing' -- has concluded
that the result of this 'thinking' process is at least plausible. Although the
implementation (assuming the trichotomy is correct) in the brain is
via parallel neural structures, the movement of information through those
structures is serial in nature. An interesting note on the above trichotomy;
note what occurs when the input to the associational network is changed.
If the new input is not consistent with the previously existing 'context'
then the 'reasonability tester' will cause an automatic readjustment of
the 'context'.
Needless to say, this is not a rigorously proven theory of mine,
but I feel it is quite plausible and that there are profuse psychophysical
and phychological studies that reinforce the above model. As of now, I
use it as a general guiding light in my work with vision systems, but it
seems equally appplicable to general AI.
Philip Kahn
KAHN@UCLA-CS.ARPA