Originally published in 2009 Iain McGilchrist’s The Master and his Emissary explores the differences between the brain’s right and left hemispheres and their effects on society, history and culture. The book, which has been an enormous critical success and has sold widely across the world, is now available in a beautiful new paperback format. In this extract, McGilchrist sets out his pioneering argument.
This book tells a story about ourselves and the world, and about how we got to be where we are now. While much of it is about the structure of the human brain – the place where mind meets matter – ultimately it is an attempt to understand the structure of the world that the brain has in part created.
Whatever the relationship between consciousness and the brain – unless the brain plays no role in bringing the world as we experience it into being, a position that must have few adherents – its structure has to be significant. It might even give us clues to understanding the structure of the world it mediates, the world we know. So, to ask a very simple question, why is the brain so clearly and profoundly divided? Why, for that matter, are the two cerebral hemispheres asymmetrical? Do they really differ in any important sense? If so, in what way?
The subject of hemisphere differences has a poor track record, discouraging to those who wish to be sure that they are not going to make fools of themselves in the long run. Views on the matter have gone through a number of phases since it was first noticed in the mid-nineteenth century that the hemispheres were not identical, and that there seemed to be a clear asymmetry of function related to language, favouring the left hemisphere. At first, it was believed that, apart from each hemisphere obviously having sensory and motor responsibility for, and control of, the opposite (or ‘contralateral’) side of the body, language was the defining difference, the main specific task of the left hemisphere. The right hemisphere was considered to be essentially ‘silent’. Then it was discovered that, after all, the right hemisphere appeared better equipped than the left hemisphere to handle visual imagery, and this was accepted as the particular contribution it made, its equivalent to language: words in the left hemisphere, pictures in the right. But that, too, proved unsatisfactory. Both hemispheres, it is now clear, can deal with either kind of material, words or images, in different ways. Subsequent attempts to decide which set of functions are segregated in which hemisphere have mainly been discarded, piece after piece of evidence suggesting that every identifiable human activity is actually served at some level by both hemispheres. There is, apparently, vast redundancy. Enthusiasm for finding the key to hemisphere differences has waned, and it is no longer respectable for a neuroscientist to hypothesise on the subject.
This is hardly surprising, given the set of beliefs about the differences between the hemispheres which has passed into the popular consciousness. These beliefs could, without much violence to the facts, be characterised as versions of the idea that the left hemisphere is somehow gritty, rational, realistic but dull, and the right hemisphere airy-fairy and impressionistic, but creative and exciting; a formulation reminiscent of Sellar and Yeatman’s immortal distinction (in their parody of English history teaching, 1066 and All That) between the Roundheads – ‘Right and Repulsive’ – and the Cavaliers – ‘Wrong but Wromantic’. In reality, both hemispheres are crucially involved in reason, just as they are in language; both hemispheres play their part in creativity. Perhaps the most absurd of these popular misconceptions is that the left hemisphere, hard-nosed and logical, is somehow male, and the right hemisphere, dreamy and sensitive, is somehow female. If there is any evidence that could begin to associate each sex with a single cerebral hemisphere in this way, it tends to indicate, if anything, the reverse – but that is another story and one that I will not attempt to deal with in this book. Discouraged by this kind of popular travesty, neuroscience has returned to the necessary and unimpeachable business of amassing findings, and has largely given up the attempt to make sense of the findings, once amassed, in any larger context.
Nonetheless it does not seem to me likely that the ways in which the hemispheres differ are simply random, dictated by purely contingent factors such as the need for space, or the utility of dividing labour, implying that it would work just as well if the various specific brain activities were swapped around between hemispheres as room dictates. Fortunately, I am not alone in this. Despite the recognition that the idea has been hijacked by everyone from management trainers to advertising copywriters, a number of the most knowledgeable people in the field have been unable to escape the conclusion that there is something profound here that requires explanation. Joseph Hellige, for example, arguably the world’s best informed authority on the subject, writes that while both hemispheres seem to be involved in one way or another in almost everything we do, there are some ‘very striking’ differences in the information-processing abilities and propensities of the two hemispheres. V. S. Ramachandran, another well-known and highly regarded neuroscientist, accepts that the issue of hemisphere difference has been traduced, but concludes: ‘The existence of such a pop culture shouldn’t cloud the main issue – the notion that the two hemispheres may indeed be specialised for different functions.’ And recently Tim Crow, one of the subtlest and most sceptical of neuroscientists researching into mind and brain, who has often remarked on the association between the development of language, functional brain asymmetry and psychosis, has gone so far as to write that ‘except in the light of lateralisation nothing in human psychology/psychiatry makes any sense.’
There is little doubt that the issues of brain asymmetry and hemisphere specialisation are significant. The question is only – of what?
I believe there is, literally, a world of difference between the hemispheres. Understanding quite what that is has involved a journey through many apparently unrelated areas: not just neurology and psychology, but philosophy, literature and the arts, and even, to some extent, archaeology and anthropology, and I hope the specialists in these areas will forgive my trespasses. Every realm of academic endeavour is now subject to an explosion of information that renders those few who can still truly call themselves experts, experts on less and less. Partly for this very reason it nonetheless seems to me worthwhile to try to make links outside and across the boundaries of the disciplines, even though the price may be that one is always at best an interested outsider, at worst an interloper condemned to make mistakes that will be obvious to those who really know. Knowledge moves on, and even at any one time is far from certain. My hope is only that what I have to say may resonate with the ideas of others and possibly act as a stimulus to further reflection by those better qualified than myself.
I have come to believe that the cerebral hemispheres differ in ways that have meaning. There is a plethora of well-substantiated findings that indicate that there are consistent differences – neuropsychological, anatomical, physiological and chemical, amongst others – between the hemispheres. But when I talk of ‘meaning’, it is not just that I believe there to be a coherent pattern to these differences. That is a necessary first step. I would go further, however, and suggest that such a coherent pattern of differences helps to explain aspects of human experience, and therefore means something in terms of our lives, and even helps explain the trajectory of our common lives in the Western world.
My thesis is that for us as human beings there are two fundamentally opposed realities, two different modes of experience; that each is of ultimate importance in bringing about the recognisably human world; and that their difference is rooted in the bihemispheric structure of the brain. It follows that the hemispheres need to co-operate, but I believe they are in fact involved in a sort of power struggle, and that this explains many aspects of contemporary Western culture.
Iain McGilchrist is a former fellow of All Souls College, Oxford, where he taught literature before training in medicine. He was consultant psychiatrist and clinical director at the Bethlem Royal and Maudsley Hospital, London, and has researched in neuroimaging at Johns Hopkins University, Baltimore. He now works privately in London and otherwise lives on the Isle of Skye. The Master and His Emissary is available now in a beautiful new paperback edition from Yale.
In this 10,000-word essay, written to complement The Master and His Emissary, McGilchrist asks why – despite the vast increase in material well-being – people are less happy today than they were half a century ago, and suggests that the division between the two hemispheres of the brain has a critical effect on how we see and understand the world around us. In particular, McGilchrist suggests, the left hemisphere’s obsession with reducing everything it sees to the level of minute, mechanistic detail is robbing modern society of the ability to understand and appreciate deeper human values. Accessible to readers who haven’t yet read The Master and His Emissary as well as those who have, this is a fascinating, immensely thought-provoking essay that delves to the very heart of what it means to be human.
The Divided Brain is available from Amazon in July 2012