From of review of The Cerebral
Code: Thinking a Thought in the Mosaic of the Mind by William H. Calvin (1996).
A
The book is also an ode to
selection (the Darwin Machine), the creative process so common in nature
(Dawkins, 1976) and represented (1) on a geologic time scale by speciation, (2)
in days to weeks by the immune system, and (3) in milliseconds in the corticocortical neurons in the superficial layers of
cerebral cortex by the mechanism responsible for thinking. Evidence from
techniques that allow observation of living human brains suggest
that memories are repetitive across many cells. Looking at the brain from
above, Calvin envisions a patchwork of incessantly active interlocking
hexagons, the boundaries of which are dynamic, "twinkling" with
vibrancy. While the firing patterns of spatiotemporal representations last for
a while, they must be prepared for transformation via
a cerebral code into spatial representations for permanent (long term) storage
with capacity for retrieval.
Two neuroscience events in 1991
enabled Calvin to conceive of the operation of neurons in cortex as a darwinian process. First,
synchrony was found in nervous tissue, and, second, standard length axons were
observed in the very area of the brain in which the processes responsible for
higher intellectual functions appeared to take place. In Calvin's conception,
thoughts - combinations of sensations, memories, and imagined plans of action
-- take the form of "cerebral codes" the cloning of which produces
the replications needed to start up the Darwin Machine. Standard length axons
in the outermost layers of the neocortex opened a
door into geometry from whence came the concept of hexagons cloning with
variation in a "multifaceted" neural environment that encourages some
variations over others and in which memory is the re-evoking of an activity
patterns, or cerebral codes. The "sophisticated groping," as Piaget
referred to it, is, for Calvin, an evolutionary contest within the brain. The
currently most active cortical representations are conscious; unconscious
processes are background noises that come to a degree of transitory awareness
in dreaming. Plastic areas in the brain do not retain their innate attractors.
The triangular arrays in hexagonal Hebbian cell
assemblies, like the lights of fireflies, live together in synchrony before
they fade. In the cortex, unlike in fireflies, when the number of copies of
spatiotemporal patterns of neural firing reaches critical mass, the circuit
trips and the message is conscious. Unsuccessful
competitors among the cerebral codes linger in weakened form and may later
re-emerge.
For Calvin, the darwinian process is correctly
seen as consisting of six essential parts, natural selection being just one of
the six. Among others are capacity for replication,
variation, competition, and inheriting such that each generation is derived
from the "more successful" of the one before, a process that
"looks Lamarkian enough to overlay even inborn
wiring patterns," and if so, might be of significance for cultural
evolution. (p. 117)
In the past, neuroanatomists
studied the brain, psychologists studied behavior, and the two were as separate
as any Cartesian dualist would posit. No one studied the mind except
philosophers and such early heretics as William James. Today, Derek Bickerton (1994), to whom Calvin devotes several pages,
speaks of a "catastrophic event" when the machinery for syntax
suddenly came in whole cloth, and language was upgraded from protolanguage to a
far more powerful form. The same neuronal machinery, Calvin opines,
that is needed for throwing, dancing, and "fondness for" music,
underlies all languages; it is the syntactical substrate they have in common
and to which linguists refer as the Universal Language. It is not known, of
course, which of the sudden new capacities was the adaptation and which the
ones that, given availability of the marvelous apparatus, were then developed.
Perhaps language piggy-backed on capacities developed to increase ability to
throw projectiles ("hand-axes") at prey. The basic similarity of
language structure worldwide means that the big change happened early in human
prehistory, roughly two hundred fifty thousand years ago, as Homo erectus gave
way to Homo sapiens, a change associated with a brain size expansion which,
interestingly enough, overshot current size. The Neanderthals appear to have
had cranial capacities larger than that of Homo sapiens. The focus shifted to
internal organization and differentiation. More overall space was not needed;
the payoffs for intricate organization were bigger than for unorganized size.
Consider the compactness (to say nothing of the retrieval capacity) of a
tree-structured taxonomy compared with sheer proliferation of unconnected
units. The Neanderthals may have had a protolanguage, even one with a large
vocabulary, but they were incapable of the infinite variety of thoughts that
can be thought and images that can be imagined that came with the neural
machinery upgrade that made Homo sapiens, Homo sapiens.
Creativity and ability to plan are
the result of ability to process images off-line and to analyze using
metaphors. We imagine actions and their probable consequences, and then those
consequences, and their probable consequences, and so forth. The procedure
helps us select the best. This is intelligence; it is mental rehearsal,
abstraction, and what-if thought freed from immediate circumstances. Off-line
thinking IS what we can do that members of other species cannot (Bickerton, 1995).
Calvin's foray into the kinds of
neural processes that might produce aspects of brain activity associated with
higher intellectual functions can be traced to Donald O. Hebb's
(1949) theoretical formulations. Hebb maintained that
psychology was about underlying processes, not just overt acts. Memory requires
some form of enduring change -- in the chemistry of the cells, in attractors,
in firing patterns.
Whatever modifications to hexagon
theory might be required, whatever criticism it may receive, in spelling out a
conceivable process at the level of events in the material world, Calvin
operates at the frontier that has separated science and philosophy, the point
of split from "qualia" to traceable
patterns of electrical and chemical activity in neocortex.
This might bother the pious, but is irrelevant here. Understanding which
muscles, nerves, bones and neurotransmitters might be involved in lifting the
arm does not produce paralysis of the limb. Similarly, understanding the
nervous system does not in itself affect the process, (although understanding
the process might lead ultimately to culturally mediated improvements).
Calvin's theory covers much
psychological ground -- intelligence, creativity, memory, even consciousness.
Above all, he bridges a gap many believe to be unbridgeable -- the chasm
between behavior and observable physiological events, between the world of self
and self-consciousness, and the world of what really, physically, observably,
goes on inside the previously inscrutable brain. The Darwin Machine is the
answer to the Argument From Design which to many
minds, including (in subtler guises) the majority of scientific minds, remains
the major "reasonable" objection to evolution (Dennett, 1995). Calvin
intones that where the Darwin Machine operates complexity emerges despite
simple beginnings, the plain turns into the fancy, and human beings emerge in
unbroken line from unicellular specks. In Calvin's words, a "milliseconds
to minutes darwinian rachet forms the foundation, atop which our sophisticated
mental life is built" (p. 5).
Calvin published a second book in
1996, How Brains Think. Aimed at a more general audience, it covers much of the
same theoretical ground as Cerebral Codes, and will be reviewed elsewhere in
these pages. Although the "twin" books parallel each other, How
Brains Think expands on subjects not dealt with in The Cerebral Code (e.g., ice
age evolution and animal intelligence). Written "for colleagues,"
Code will be of greater interest and be better understood by those familiar
with the basic vocabulary and findings of brain theorists.
References:
Bickerton, D. (1990). Language and
Species.