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Michael S. Gazzaniga


The Sience Behind What Makes Us Unique

Book review by Anthony Campbell. The review is licensed under a Creative Commons Licence.
People who write about the brain in an evolutionary context tend to fall into one of two groups. Some seek for continuity between humans and other animals, while others concentrate on the differences between them. Gazzaniga belongs to the second group; he finds there is a qualitative as well as a quantitative difference separating us from other species.

The book covers a lot of territory, starting with brain anatomy and ending with the prospects for technology to modify the human brain by means of implants or genetic manipulation. On the way there is extensive discussion of the neurological basis of social interactions, religion, and morality.

Gazzaniga is an eminent neuroscientist who definitely possesses the common touch; his writing is extremely accessible to the non-specialist. Its tone is popular and light-hearted, even jocular at times, without falling into the trap of superficiality. Gazzaniga doesn't over-simply by presenting only one point of view about the subjects he discusses; he usually provides a summary of the differing opinions that researchers have expressed.

For example, the question of whether, or to what extent, non-human animals possess theory of mind (the ability to understand what other individuals, including humans, are thinking) comes up a good deal in the book. This is still a contentious matter. There seems little doubt that some species, especially chimpanzees, do have this capacity, although not to the extent that we do. But chimps are bested in this respect by dogs, at least so far as interaction with humans is concerned. Owing to their long association with us, dogs are better than chimps at interpreting human thoughts and attention.

Gazzaniga attaches a lot of importance to the idea of brain modules. By this he means "a hard-wired (innate) mechanism that unconsciously directs you to think in a certain way, that directs your attention to such states as belief, desires, and pretense and then allows you to learn about these mental states". This is what has been called the Swiss-army-knife view of how the brain works, and it comes up in many contexts throughout the book; for example, in the discussion of how religious beliefs are formed. Here Gazzaniga draws on the view of Pascal Boyer, who holds that religion results from the normal functioning of the brain mechanisms that have evolved to deal with everyday situations.

Probably the most obvious difference between humans and other animals is our use of language. Just for this reason it is a huge subject that has attracted a vast amount of speculation and argument, and this is probably why Gazzaniga has chosen to touch on it somewhat peripherally here. He does discuss the attempts to communicate with chimpanzees, which have succeeded up to a point, although there is still much controvery about these experiments. But he doesn't mention Noam Chomsky's theory of an innate language mechanism (module?), which I find a little surprising.

The notorious mind-body problem always lurks below the surface in books of this kind and Gazzaniga does have something to say about it; in fact, it gets a chapter to itself towards the end of the book (Chapter 7). This opens with a quotation from Roger Sperry, who said that the brain processes that give rise to consciousness "are so far beyond our comprehension that no one I know of has been able to imagine their nature". Gazzaniga doesn't attempt to provide a solution to this conundrum.

We are not going to talk about whether the mind and body are the same or separate in reality We are going to talk about why most people believe they are separate, and why even people who don't believe they are separate act as if they are separate.
The answer, once again, is modules. We have inbuilt brain mechanisms that cause us to have an intuitive biology, an intuitive physics, and an intuitive psychology, among other innate mental propensities for conceiving the world. Dualism emerges as a result of these things. Other animals share these mechanisms to varying extents, but Gazzaniga finds that humans are unique in their ability to reason about unobservable forces behind phenomena. This kind of rational thinking is a recent acquisition and it does not come easily, but it is what underpins science.

In spite of his disavowal of an intention to discuss the physical basis of consciousness which I quoted above, it obviously intrigues Gazzaniga because he returns to it in Chapter 8, where he considers "the unsolved mystery" of how conscious experience emerges from unconscious brain processes. As he rightly remarks, much of the discussion of this question has become rather confusing, with the postulation of multiple levels of awareness. He prefers Antonio Damasio's relatively simple concept of just two levels, core and extended consiousness. Core consciousness is not unique to humans. Extended consciousness is present in animals too, but to what degree is the important question. Extended consciousness is what we normally think of as being conscious. It brings us knowledge of what is going on in the world around us.

Modularity is important in relation to extended consciousness. But if the brain is made up of modules, how come we feel unified? This is a topic that Gazzaniga's own research has focused on over many years and to which he has made major contributions, particularly concerning those rare patients who have been treated for intractable epilepsy by surgical division of the corpus callosum (the main nerve tract connecting the two hemispheres of the brain). There are only about ten of these patients still alive and there won't be many more, because the operation has (fortunately) been largely superseded by improvements in medical treatment.

One would think that cutting this tract would have dramatic effects on the personality, but in fact there is very little obvious effect and the patients feel quite normal and unified. It takes sophisticated techniques to reveal differences from normality. The findings Gazzaniga describes are not new but his discussion brings out some nuances that I hadn't been aware of before. According to Gazzaniga, the reason patients who have had this operation don't seem to have split personalities is because speech is located in only one hemisphere (nearly always the left). The right hemisphere is therefore unable to speak. If the patient is asked to explain something the right hemisphere has done, it won't know the real reason but will produce a plausible-sounding explanation.

Chapter 8 concludes with a fairly detailed discussion of whether any animals have been shown to possess awareness of self, the ability to recall events or imagine future events, or to think about what they know. Some research suggests that they do, but there are always reasons to doubt that this is really the case.

I found Chapters 7 and 8 to be the best part of the book. In fact, I would say that it is worth reading for these sections alone.


%T Human
%S The Science Behind What Makes Us Unique
%A Michael A. Gazzaniga
%I Ecco (HarperCollinsPublishers
%C New York
%D 2008
%G ISBN 9780060892883
%P xii + 447pp
%K biology

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