on. All of the internal representations of such entities involve the inevitable
feature of chunked models: determinism is sacrificed for simplicity. Our
representation of reality ends up being able only to predict probabilities of
ending up in certain parts of abstract spaces of behavior-not to predict
anything with the precision of physics.
Procedural and Declarative KnowledgeA distinction which is made in Artificial Intelligence is that between pro-
cedural and declarative types of knowledge. A piece of knowledge is said to
be declarative if it is stored explicitly, so that not only the programmer but
also the program can "read" it as if it were in an encyclopedia or an
almanac. This usually means that it is encoded locally, not spread around.
By contrast, procedural knowledge is not encoded as facts---only as pro-
grams. A programmer may be able to peer in and say, "I see that because of
these procedures here, the program 'knows' how to write English
sentences "-but the program itself may have no explicit awareness of how it
writes those sentences. For instance, its vocabulary may include none of the
words "English", "sentence", and "write" at all! Thus procedural knowl-
edge is usually spread around in pieces, and you can't retrieve it, or "key"
on it. It is a global consequence of how the program works, not a local
detail. In other words, a piece of purely procedural knowledge is an
epiphenomenon.
In most people there coexists, along with a powerful procedural rep-
resentation of the grammar of their native language, a weaker declarative
representation of it. The two may easily be in conflict, so that a native
speaker will often instruct a foreigner to say things he himself would never
say, but which agree with the declarative "book learning" he acquired in
school sometime. The intuitive or chunked laws of physics and other
disciplines mentioned earlier fall mainly on the procedural side; the knowl-
edge that an octopus has eight tentacles falls mainly on the declarative side.
In between the declarative and procedural extremes, there are all
possible shades. Consider the recall of a melody. Is the melody stored in
your brain, note by note? Could a surgeon extract a winding neural fila-
ment from your brain, then stretch it straight, and finally proceed to
pinpoint along it the successively stored notes, almost as if it were a piece of
magnetic tape? If so, then melodies are stored declaratively. Or is the recall
of a melody mediated by the interaction of a large number of symbols,
some of which represent tonal relationships, others of which represent
emotional qualities, others of which represent rhythmic devices, and so on?
If so, then melodies are stored procedurally. In reality, there is probably a
mixture of these extremes in the way a melody is stored and recalled.
It is interesting that, in pulling a melody out of memory, most people
do not discriminate as to key, so that they are as likely to sing "Happy
Birthday" in the key of F -sharp as in the key of C. This indicates that tone
relationships, rather than absolute tones, are stored. But there is no reason
Brains and Thoughts^363