be triggered. In cells, all the complex molecules and organelles are built up,
simple step by simple step. Some of these new structures are often enzymes
themselves, and they participate in the building of new enzymes, which in
turn participate in the building of yet other types of enzyme, etc. Such
recursive cascades of enzymes can have drastic effects on what a ceil is
doing. One would like to see the same kind of simple step-by-step assembly
process imported into AI, in the construction of useful subprograms. For
instance, repetition has a way of burning new circuits into our mental
hardware, so that oft-repeated pieces of behavior become encoded below
the conscious level. It would be extremely useful if there were an analogous
way of synthesizing efficient pieces of code which can carry out the same
sequence of operations as something which has been learned on a higher
level of "consciousness". Enzyme cascades may suggest a model for how this
could be done. (The program called "HACKER", written by Gerald
Sussman, synthesizes and debugs small subroutines in a way not too much
unlike that of enzyme cascades.)
The sameness-detectors in the Bongard problem-solver (Sams) could
be implemented as enzyme-like subprograms. Like an enzyme, a Sam
would meander about somewhat at random, bumping into small data
structures here and there. Upon filling its two "active sites" with identical
data structures, the Sam would emit a message to other parts (actors) of the
program. As long as programs are serial, it would not make much sense t~
have several copies of a Sam, but in a truly parallel computer, regulating
the number of copies of a subprogram would be a way of regulating the
expected waiting-time before an operation gets done, just as regulating the
number of copies of an enzyme in a cell regulates how fast that function
gets performed. And if new Sams could be synthesized, that would be
comparable to the seepage of pattern detection into lower levels of our
minds.
Fission and FusionTwo interesting and complementary ideas concerning the interaction of
symbols are "fission" and "fusion". Fission is the gradual divergence of a
new symbol from its parent symbol (that is, from the symbol which served
as a template off of which it was copied). Fusion is what happens when two
(or more) originaily unrelated symbols participate in a ')oint activation",
passing messages so tightly back and forth that they get bound together
and the combination can thereafter be addressed as if it were a single
symbol. Fission is a more or less inevitable process, since once a new symbol
has been "rubbed off" of an old one, it becomes autonomous, and its
interactions with the outside world get reflected in its private internal
structure; so what started out as a perfect copy will soon become imperfect,
and then slowly will become less and less like the symbol off of which it was
"rubbed". Fusion is a subtler thing. When do two concepts really become
one? Is there some precise instant when a fusion takes place?(^664) Artificial Intelligence: Prospects