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another---increases as you move down-spectr um. Rea-
soning works (theoretically) from rst principles. But
common sense depends on your recalling a familiar
idea or technique, or a previous experience. When your
mind drifts as you look out a window, one recollection
leads to another, and to a third, and onward---but even-
tually you return to the task at hand. Once you reach the
edge of sleep, though, free association goes unchecked.
And when you dream, one character or scene transforms
itself into another smoothly and illogically---just as one
memory transforms itself into another in free associa-
tion. Dreaming is free association "from the inside."
At the high-focus end, you assemble your thought
train as if you were assembling a comic strip or a story-
board. You can step back and "see" many thoughts
at once. (To think analytically, you must have your
premises, goal, and subgoals in mind.) At the high-
focus end, you manipulate your thoughts as if they
were objects; you control the train.
At the bottom, it s just the opposite. You don t
control your thoughts. You say, "my mind is wander-
ing," as if you and your mind were separate, as if your
thoughts were roaming around by themselves.
If at high focus you manipulate your thoughts
"from the outside," at low focus you step into each
thought as if you were entering a room; you inhabit
it. That s what hallucination means. The opposite of
high focus, where you control your thoughts, is hallu-
cination---where your thoughts control you. They con-
trol your perceived environment and experiences; you
"inhabit" each in turn. (We sometimes speak of "sur-
rendering" to sleep; sur rendering to your thoughts is
the opposite of controlling them.)
At the high-focus end, your "I" is separate from
your thought train, obser ving it critically and con-
trolling it. At the low end, your "I" blends into it (or
The cognitive continuum is, arguably, the single
most important fact about thought. If we accept its
existence, we can explain and can model (say, in soft-
ware) the dynamics of thought. Thought styles change
throughout the day as our focus level changes. (Focus
levels depend, in turn, partly on personality and intel-
ligence: some people are capable of higher focus; some
are more comfortable in higher-focus states.)
It also seems logical to surmise that cognitive
maturing increases the focus level you are able to
reach and sustain---and therefore increases your abil-
ity and tendency to think abstractly.
Even more important: if we accept the existence of
the spectrum, an explanation and model of analogy
discovery---thus, of creativity---falls into our laps.
As you move down-spectrum, where you inhabit (not
observe) your thoughts, you feel them. In other words,
as you move down-spectr um, emotions emerge. Dream-
ing, at the bottom, is emotional.
Emotions are a powerful coding or compression
device. A bar code can encapsulate or encode much
information. An emotion is a "mental bar code" that
encapsulates a memory. But the function E(m)---the
"emotion" function that takes a memory m and yields
the emotion you in particular feel when you think about
m---does not generate unique values. Two di erent-
seeming memories can produce the same emotion.
How do we invent analogies? What made
Shakespeare write, "Shall I compare thee to a summer s
day?" Shakespeare s lady didn t look like a summer s
day. (And what does a "summer s day" look like?)
An analogy is a two-element thought train---"a sum-
mer s day" followed by the memory of some person.
Why should the mind conjure up these two elements
in succession? What links them?
Answer: in some cases (perhaps in many), their
"emotional bar codes" match---or were su ciently simi-
lar that one recalled the other. The lady and the sum-
mer s day made the poet feel the same sort of way.
We experience more emotions than we can name.
"Mildly happy," "happy," "ebullient," "elated"; our
choice of English words is narrow. But how do you feel
when you are about to open your mailbox, expecting a
letter that will probably bring good news but might be
cr ushing? When you see a rhinoceros? These emotions
have no names. But each "represents" or "encodes"
some collection of circumstances. Two experiences that
seem to have nothing in common might awaken---in you
only---the same emotion. And you might see, accord-
ingly, an analogy that no one else ever saw.
The cognitive spectrum suggests that analogies are
created by shared emotion---the linking of two thoughts
with shared or similar emotional content.
To build a simulated unconscious mind, we don t
need a computer with real emotions; simulated emo-
tions will do. Achieving them will be hard. So will
representing memories (with all their complex "multi-
But if we take the route Turing hinted at back in
1950, if we forget about consciousness and concen-
trate on the process of thought, there s every reason to
believe that we can get AI back on track---and that AI
can produce powerful software and show us important
things about the human mind.
David Gelernter is a professor of computer science at Yale
University and a national fellow of the American Enterprise
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