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Calvin offers an evolutionary description of the development of human intelligence. He's very careful to avoid using "consciousness" since Dennett, Humphreys, Pinker and others have firmly employed that term. Calvin cites Piaget's "intelligence is what you use when you don't know what to do next" as a foundation thesis. From this he compares human mental talents with those of other animals, mostly primates, to demonstrate evolutionary roots for our intelligence. Behaviour issues common to everyday life become visible evidence for what is going on in our brains. Calvin manages to take his analysis into the physical processes that occur as we decide on our actions. It's a well written and "down to earth" explanation of many questions we have on what intelligence is and how we use it.
Piaget's comment reflects the growing knowledge of brain processes. Much of the brain's time is spent collecting, storing, retrieving and applying information. This means that both "unconscious" events and our expressions and actions only come about after numerous and complicated signal processing has already occurred. Calvin describes in both text and graphics how neurons are constructed, convey data, and interact within the brain. Clearly, nothing is instantaneous and many elements are competing for dominance during every moment awake. Clear, too, is the notion that while other primates have many talents to deal with their surroundings, none possess the powers evolution gave humans.
What drives these powerful mental abilities? He rebuffs the idea of the "quantum brain". It's too deep in the brain's structure - "in the subbasement of physics". That's too far removed from areas of vision, speech, and memory. There are certainly quantum events going on with all that chemical and electrical activity inside your skull, but Calvin sees these forces as far to deep to have direct impact on mental processes. Calvin is more concerned with the human level of analysis. One proposal he adopts wholeheartedly, but without attribution, is Daniel Dennett's concept of the "multiple drafts model" of thinking and expression. Calvin, to his credit, outstrips even Dennett's abilities of description in depicting this process. He shows, for example, how the brain's memory storage facility considers many images before it resolves that the round thing flying past is a tennis ball. It's an exquisite example, and you perceive clearly how many other daily occurrences are resolved in a similar manner.
The accumulation of evidence about our evolutionary roots, the environmental changes forced on us and the rise of language and use of syntax are all contained within a device Calvin labels the "Darwin Machine." The Machine has six "essentials" which cover topics like replication, mutation and success in adaptation. He demonstrates how the "essentials" provide a mechanism for complexity from simplicity. Where some creatures modified things like limbs, teeth or hair, it was our brain that evolved from simple to complex.
While evolution of the human brain isn't a new topic, Calvin presents a better summary of its roots and operations than most cognitive scientists. This is a fine book to start any study of the brain, but must be enhanced by other, more complete, works. [stephen a. haines - Ottawa, Canada]