The Divided Brain and the Search for Meaning

by Iain McGilchrist

paperback edition of The Master and His Emissary, Yale invited Iain to write one of the first in a new series of short, lively e-books by some of our most popular authors, in which he draws on

What we do not expect to find, we just will not see: much elegant research demonstrates that we are essentially blind to what we do not think is there.

The solution appears to have been the brain's separate hemispheres. Each of these neuronal masses is sufficient in itself and on its own to sustain consciousness. And since attention is an aspect of consciousness (a machine can carry out tasks, but it cannot attend) each can therefore attend to the world in a different way. What we call our consciousness moves back and forth between them seamlessly, drawing on each as required, and often very rapidly.

The left hemisphere, as in birds and animals, pays the narrow-beam, precisely focussed, attention which enables us to get and grasp: it is the left hemisphere that controls the right hand with which we grasp something, and controls the aspects of language (not all language) by virtue of which we say we have ‘grasped’ the meaning – made it certain and pinned it down. The right hemisphere underwrites sustained attention and vigilance for whatever may be, without preconception. Its attention is not in the service of manipulation, but in the service of connection, exploration and relation.

One way of looking at the difference would be to say that while the left hemisphere's raison d'être is to narrow things down to a certainty, the right hemisphere's is to open them up into possibility. In life we need both. In fact for practical purposes, narrowing things down to a certainty, so that we can grasp them, is more helpful. But it is also illusory, since certainty itself is an illusion – albeit, as I say, a useful one. There is no certainty. The more

Another way of thinking of the difference between the hemispheres is to see the left hemisphere's world as tending towards fixity, whereas that of the right tends towards flow. All

The left hemisphere's take on things comes from assessing thousands of points of information in turn and trying to reach a conclusion about the whole picture that way.

This partwise method of understanding, and resistance to the idea of things flowing and changing, together go some way to explain the left hemisphere's affinity for what is mechanical or inanimate. Only the left hemisphere encodes tools and machines – you will remember that the purpose of the left hemisphere is to allow us to manipulate the world, not to understand it.

The right hemisphere seems to be involved more with new experience, new events, things, ideas, words, skills or music, or whatever it may be, while they are still fresh, original and unique, and so to speak present, to the mind. The right hemisphere's world is present – or more precisely ‘presences’ to us, as Heidegger puts it.

By contrast the left hemisphere's world takes over once whatever it is is represented – literally ‘re-presented’ after the fact: once it is familiar and known, as an instance of something, a concept. You can actually see this process happening using brain imaging.

The left hemisphere abstracts and generalises, where the right hemisphere's world remains truer to each embodied inst...

The left hemisphere's world is a representation only. It is like a map, useful precisely because almost all the information about the land to which it refers has been left out.

Under such circumstances one has only the left hemisphere to go on, and, true to its proper function, it is interested only in the part of space that is of use to it, the right half of space. It is not interested in understanding the world as a whole, only with having control of the bit it manipulates.

Following a right-hemisphere stroke, the patient may cease to attend to anything on the left,

following a left hemisphere stroke, the right hemisphere delivers a complete world, not a half-world.

true. The left hemisphere is not in touch with reality but with its representation of reality, which turns out to be a remarkably self-enclosed, self-referring system of tokens.

I'd say the defining quality of the right hemisphere's world is that it is all in relations, what I call ‘betweenness’. This starts with its having a relationship with the world at large, not seeing it as a separate object, ripe for manipulation. What do I mean by ‘betweenness'? Think about the nature of music. Music does not exist in one particular note – which is in itself meaningless; or in a lot of such single notes, each in itself meaningless. I am tempted to say it exists more in the spaces than in the notes: the spaces between successive notes in pitch that creates the melody,

But I should remind you that both hemispheres are involved in reasoning and in emotion. The left hemisphere is especially good at voluntary and social expressions of emotion and one of the most clearly lateralised emotional registers is that of anger, which lateralises to the left hemisphere. Deeper

Much of mathematics is dependent on the right hemisphere: most of its great discoveries were perceived as complex patterns of relationships, and only later, often much later, translated painstakingly into linear sets of propositions.

left hemisphere sees truth as internal coherence of the system, not correspondence with the reality we experience.

the right hemisphere is perfectly happy with ‘both/and’ – sees in fact how necessary that is in understanding the world. The left hemisphere, by contrast, says: ‘What's the matter? Can't you make up your mind?’ It has to be ‘either/or’, black or white, never a life within the full colour

The right hemisphere, the so-called minor hemisphere, is in fact the one that knows, and more importantly the one that understands, more.

So the meaning of an utterance begins in the right hemisphere, is made explicit (literally folded out, or unfolded) in the left, and then the whole utterance needs to be ‘returned’ to the right hemisphere, where it is reintegrated with all that is implicit – tone, irony, metaphor, humour, and so on, as well as a feel of the context in which the utterance is to be understood.

I say ‘it is hot in here’, your right hemisphere knows that what I mean is ‘please open the window’, while your left hemisphere thinks I am offering helpful meteorological data. The left hemisphere is adept at procedures, but sees them as ends in themselves. In fact, in the presence of right hemisphere brain damage, or abnormal left hemisphere activation, the left hemisphere may produce a sort of meaningless logorrhoea.

The left hemisphere is not in touch with the world. It is demonstrably self-deceiving, and confabulates – makes up a story, when it cannot understand something,

right hemisphere, which tends toward self-doubt, it takes a distinctly flattering view of its own capabilities. And when, as in the case of a paralysed limb, it is confronted with evidence that all is not well, it refuses to recognise the problem. If forced to do so, it disowns it – won't take responsibility: the paralysed limb belongs to the person in the next bed.

It is not reasonable. It is angry when challenged, dismisses evidence it doesn't like or can't understand, and is unreasonably sure of its own rightness. It is not good at understanding the world. Its attention is narrow, its vision myopic, and it can't see how the parts fit together. It is good for only one thing – manipulating the world. Its world is a representation, a virtual world, only. It neglects the incarnate nature of human beings, reducing them to the equivalent of brains in a vat. It reduces the living to the mechanical. It prioritises the procedure, without a grasp of its meaning or purpose. And it requires certainty where none can be found.