Perhaps the best thing to do here is to just quote a passage from McGilchrist in full.
»If one had to encapsulate the principal differences in the experience mediated by the two hemispheres, their two modes of being, one could put it like this. The world of the left hemisphere, dependent on denotative language and abstraction, yields clarity and power to manipulate things that are known, fixed, static, isolated, decontextualised, explicit, disembodied, general in nature, but ultimately lifeless.
The right hemisphere, by contrast, yields a world of individual, changing, evolving, interconnected, implicit, incarnate, living beings within the context of the lived world, but in the nature of things never fully graspable, always imperfectly known — and to this world it exists in a relationship of care.
The knowledge that is mediated by the left hemisphere is knowledge within a closed system. It has the advantage of perfection, but such perfection is bought ultimately at the price of emptiness, of self reference. It can mediate knowledge only in terms of a mechanical rearrangement of other things already known. It can never really ‘break out’ to know anything new, because its knowledge is of its own representations only.
Where the thing itself is ‘present’ to the right hemisphere, it is only ‘re-presented’ by the left hemisphere, now become an idea of a thing. Where the right hemisphere is conscious of the Other, whatever it may be, the left hemisphere's consciousness is of itself.«
The left hemisphere of the brain — the divisional, abstract hemisphere — deals in universals, in abstract concepts, in certainties, in strict division between this and that. To sum it up in one word, it deals in ‘that’.
That something is happening is a left-hemisphere thing.
The right hemisphere of the brain, the non-dual, specific, contours hemisphere, deals in ‘how’. The how of things, the specific shape of how they are.
How something is happening is a right-hemisphere thing.
The two sides communicate with each other across a thin membrane, the name of which is the corpus callosum. This allows these two different 'takes' on the world to interface with each other, and to interact. That they interact is true enough, but what is more interesting still, is how.
Some of the most revealing experiments have been behavioural studies on people who have, for whatever reason, had this connecting tissue severed. The most common reason being that severing the corpus callosum is a treatment for certain forms of epilepsy, although it can simply fail to develop, as a congenital defect. This is called having a ‘split-brain’.
It is one of these experiments that I'd like to quickly examine now. McGilchrist talks about it at length in The Master and His Emissary. But also leads to an interesting and radical possibility about the nature of left hemisphere dominance, which could potentially allow us to go beyond McGilchrist's work.
The initial set-up for the experiment is relatively simple, but before it will make sense, there's a couple of things to understand.
The first is this — as we've seen, each hemisphere of the brain controls the opposite side of the body. The left hemisphere, the dualistic one which breaks things down into graspable, abstract labels, controls the right hand side of the body, all of it, the eyes, the hands, everything. The right hemisphere, the one that works in terms of contour, and the specific shape of real things, controls the left, all of it, eyes, hands, fingers, knees and toes.
The experiment is relatively simple, and it was devised by Roger Sperry and Michael Gazzaniga at Caltech back in the 1950's. It is quite a celebrated experiment, and if you have even a passing interest in neuroscience you'll almost certainly know about it. For those who don't, here's what happens.
A split-brain patient (who has had their corpus callosum severed) is placed in a booth, with some viewing apparatus. What's special about the viewing apparatus is that they allow the person running the experiment to show different images to each eye.
At the same time, the patient has a small selection of cards available. Sometimes the experimenter will ask the patient to pick up a card with their left hand, sometimes with their right.
This experiment is well cited for a reason. It is simple, brilliantly conceived, and revealing in a way that I do not think has yet been fully understood.
What it allows the researcher to do is show one side of the patient's brain a simple image — say, a chicken. The patient is then asked to select the card which they associate with the image, from a selection of cards with pictures on, pictures of things like a snow-shovel, a wheel, a car, and a chicken's foot.
From the patient's point of view, it seems like a simple image-association test. But of course, it isn't.
If the researcher shows a picture of a chicken to the person's right eye, and then asks them to pick a card up with their right hand, they will pick up the card that has a picture of a chicken's foot on it. The side of the brain that sees the chicken is also the side of the brain that controls the hand picking up the card, so it's fair enough.
In the same way, if you show a picture of a chicken to a split-brain person's left eye, and ask them to pick a card up with their left hand, they will, again, select the card that has a picture of a chicken's foot. All fair enough and above board — a clean, obvious association.
But then the experimenters mix it up a little.
They show the patient's right eye a picture of a chicken, and their left eye a picture of a snowy landscape, and then ask them to pick up a card with their left hand.
Really take the time to get a good picture of this in your head, there's a lot of lefts and rights, it can be a little confusing, but it's absolutely worth the effort. I'll just go through that again, but this time talk in terms of hemispheres.
They show the divisional hemisphere a picture of a chicken, and the holistic hemisphere a picture of a snowy landscape, and then ask the patient to pick up a card using the hand under the control of the holistic hemisphere.
The person has to pick up the card with the side of the body that saw the snowy landscape. And it picks up the card with the picture of the snow-shovel on it, because you clear snow with a snow-shovel. Again, no real surprises. But we're about to see a very big surprise.
When the researcher asks the patient to explain why they chose the shovel, the left hemisphere always fields the question. The left, divisional hemisphere is the dominant one, and the one that deals with concepts and thus dominates in the field of language. Ask a question heard by both ears, and it's the left-hemisphere, the divisional hemisphere, that answers.
The right hemisphere saw the snowy landscape, and picked up the snow-shovel card. But the left hemisphere saw the chicken.
So when the patient is asked to explain why they chose the snow-shovel, they respond in a very interesting way. They lie.
If you ask that patient why he picked up the card with the shovel on it, the patient will give this answer:
“Because you use a shovel to clear up after chickens.”
This is enormously strange. Not so much because the link between this card or that is stronger, but because this is a lie. This isn't why they chose the card. They chose the card because you use a snow shovel to shovel snow. That is why they chose it.
But when asked to account for it, the patient tells a story of a rational connection that did not occur. Regardless of how you clean out chickens, that thought process, that connection, was not something that patient actually experienced. It's just a story, a story of a seemingly rational thought process that never actually happened.
The patient is not aware that they are lying. They aren't doing it ‘on purpose’, so to speak. The lie, the fiction, the invented story of a rational process that never occurred, is generated instantly, fully internally coherent, and ready to ship, by the left hemisphere.
Now, it's tempting to file this away as a little interesting vignette, shrug, and bemoan the dishonesty of brain-damaged people.
But while it is interesting enough to note that split-brain patients lie under these circumstances, it is also interesting to note how they lie.
Which is to say — why specifically this lie? Why not another? Why lie in this exact way? Why do all of them, always lie in this exact way?