that tone relationships could not be stored quite declaratively. On the other
hand, some melodies are very easy to memorize, whereas others are ex-
tremely elusive. If it were just a matter of storing successive notes, any
melody could be stored as easily as any other. The fact that some melodies
are catchy and others are not seems 1.0 indicate that the brain has a certain
repertoire of familiar patterns which are activated as the melody is heard.
So, to "play back" the melody, those patterns would have to be activated in
the same order. This returns us to the concept of symbols triggering one
another, rather than a simple linear sequence of declaratively stored notes
or tone relationships.
How does the brain know whether a piece of knowledge is stored
declaratively? For instance, suppose you are asked, "What is the population
of Chicago?" Somehow the number five million springs to mind, without
your wondering, "Gee, how would [ go about counting them all?" Now
suppose I ask you, "How many chairs are there in your living room?" Here,
the opposite happens-instead of trying to dredge the answer out of a
mental almanac, you immediately either go to the room and count the
chairs, or you manufacture the room in your head and count the chairs in
the image of the room. The questions were of a single type-"how
many?"-yet one of them caused a piece of declarative knowledge to be
fetched, while the other one caused a procedural method of finding the
answer to be invoked. This is one example where it is clear that you have
knowledge about how you classify your own knowledge; and what is more,
some of that metaknowledge may itself be stored procedurally, so that it is
used without your even being aware of how it is done.
Visual ImageryOne of the most remarkable and difficult-to-describe qualities of con-
sciousness is visual imagery. How do we create a visual image of our living
room? Of a roaring mountain brook? Of an orange? Even more mysteri-
ous, how do we manufacture images unconsciously, images which guide
our thoughts, giving them power and color and depth? From what store
are they fetched? What magic allows us to mesh two or three images, hardly
giving a thought as to how we should do it? Knowledge of how to do this is
among the most procedural of all, for we have almost no insight into what
mental imagery is.
It may be that imagery is based on our ability to suppress motor
activity. By this, I mean the following. If you imagine an orange, there may
occur in your cortex a set of commands to pick it up, to smell it, to inspect it,
and so on. Clearly these commands cannot be carried out, because the
orange is not there. But they can be sent along the usual channels towards
the cerebellum or other suborgans of the brain, until, at some critical point,
a "mental faucet" is closed, preventing them from actually being carried
out. Depending on how far down the line this "faucet" is situated, the
images may be more or less vivid and real-seeming. Anger can cause us to(^364) Brains and Thoughts