Is that you, James?

Thomas Nagel

  • Philosophy and the Brain by J.Z. Young
    Oxford, 241 pp, £12.95, January 1987, ISBN 0 19 219215 9
  • Freedom and Belief by Galen Strawson
    Oxford, 353 pp, £27.50, January 1987, ISBN 0 19 824938 1
  • The Oxford Companion to the Mind edited by Richard Gregory
    Oxford, 874 pp, £25.00, September 1987, ISBN 0 19 866124 X

Your nervous system is as complex a physical object as there is in the universe, so far as we know: 12 billion cells, each of them a complex structure with up to sixty thousand synaptic points of connection with other cells. It is also the one piece of physical real estate of which you have an inside view, so to speak, since the events of your inner life, and the experiences through which you learn about the external world, are all immediate manifestations of what is going on in there. Since you can also study your central nervous system by external observation and experiment as you study other physical systems – by exposing its outer edges, such as the retina, to bombardment by suitably produced and therefore informative physical impulses – there arises a problem about how to bring these two views of yourself together.

The problem is as far from solution today as it was when Descartes tried to prove the distinction between mind and body 350 years ago – in spite of a widespread sense, fostered by the popular culture of science, that with the aid of computer analogies and advances in molecular biology we are on the verge of a breakthrough. The more we learn about the brain the clearer it is how little we understand its embodiment of the mind.

Here is a typical passage from Philosophy and the Brain by the eminent neurophysiologist J.Z. Young:

The pressure waves falling upon the ear from the sound of ‘Hullo’ are first transferred by the eardrum, then by the chain of three ossicles, next by fluid in the cochlear chamber and so into a travelling wave on the basilar membrane. From here they activate the hair cells to modify the trains of nerve impulses in the auditory nerve. These are then in turn re-coded several times before arriving at the auditory cortex. Here there are cells that respond only to certain patterns of these already much transformed versions of the original air waves. This is by no means the end of the process. The cortical cells continually exchange signals among themselves, which represent the patterns that have been learned in the past. Modification of the action of some of the cells by the incoming signals from the ear will produce appropriate outputs towards motor centres. The first response to the sound ‘Hullo’ may be a sharpening of attention and then, if it is repeated, perhaps a pattern of motor activity by the larynx and muscles of the throat that sends the response ‘Yes – is that you, James?’

There are evidently some gaps in the physiological story, but they get filled in with nothing more than the psychology of the man in the street dressed up as remarks about the brain.

The truth is that while a good deal is known about the outer boundaries of the nervous system – the initial effects of sensory stimulation and the last stages in the initiation of muscle contractions – we are largely ignorant about the central processes essential for hearing and seeing, let alone recognising the voice of your obnoxious colleague James who has to say ‘Hullo’ twice before you will answer him.

This darkness at the centre is emphasised by Young again and again, though there are interesting fragments of information: at least six ‘maps’ of the visual field in the cortex, in the form of patterns of cells activated by the irradiation of particular points on the retina; cells that respond to particular features of the visual stimulus, such as the directional orientation of a light-dark boundary; cells that are activated specifically by the look of human faces, and not by other types of patterns. A good deal has been learned about how individual neurons operate, how they interact with others in their neighbourhood, and how electrical nerve impulses are propagated. And a certain amount of crude geography has been inferred from the deficits produced by injury: lose Broca’s area and you can’t produce coherent speech; lose Wernicke’s area and you can’t understand language, though you can produce words; lose the hippocampus and you can’t form any new memories; lose the secondary visual association area and you can’t recognise what you are looking at, though you can see the shapes. But the understanding provided by such information is so far very limited. It is like trying to understand how the US political system works by locating the public buildings on a map of Washington DC.

Psychological theories formulated in terms of mental operations – theories of perception, learning, memory, motivation – do seek and often provide an understanding of how the mind works which transcends common sense and introspection. Some of those theories are represented in Young’s book, but though they are embellished with references to programmes in the cortex or activity in the basal forebrain areas, they are no more about the brain (and no less) than is my belief that Picasso had a remarkable imagination. The capacities described by those theories, or by that belief, are somehow or other due to the activity of the billions of cells beneath the skull or of particular large subsets of those cells, but we know remarkably little beyond that.

Young’s book is a clear, concise guide for the layman to what we do know, and he is scrupulous in pointing out the speculative character of any contemporary theory of the physical basis of central mental processes. The factual material is often fascinating, though I was disturbed by the statement, in a discussion of Sperry’s well-known split-brain cases, that the left eye communicates only with the speechless right cerebral hemisphere. In fact, it is the right half of each retina – which scans the left half of the visual field – that communicates with the right hemisphere, while information from the right half of the visual field goes to the left hemisphere. I have to assume that Young thought his simplification of the anatomical facts would be easier on the reader, but it makes me wonder whether other inaccuracies were introduced with a similar purpose – particularly since he seems concerned throughout to keep things very simple.

That aside, the book provides easy access to much information about current brain research that non-specialists should want to know, and bibliographical reference to more detailed treatments. But it is also presented, however diffidently, as a contribution to philosophy, and in this respect I am afraid it is not a success. Young believes that the information he has to offer about the brain can be useful in dealing with some of the big philosophical questions about knowledge, meaning, value and free will that have been around for a long time, but the trouble is that he has a tin ear for philosophy. He thinks information about the brain will help answer these questions because he doesn’t understand them well enough to see how easily they can be re-introduced once the facts have been heard.

The full text of this book review is only available to subscribers of the London Review of Books.

You are not logged in