The idea of the brain being split into right and left hemispheres that do radically different things has entered the popular imagination. Following an article exchange on the IAI, Scott Barry Kaufman and Iain McGilchrist finally meet to investigate the remaining untouched ground in this mind-melding debate. 

Ten years ago I wrote an article for Scientific American called “The Real Neuroscience of Creativity”. In that article, I presented an exciting new approach in neuroscience called the network approach that looks at how large-scale brain networks interact with each other to produce creativity, and I noted that these brain structures recruit areas in both the left and right hemisphere. In other words, creativity is not exclusively a right-brain phenomena.

Fast forward to 2023, the Institute of Art and Ideas asks me if they can re-share the article. Of course I give them permission. They published it, and they titled it “The right-left brain hemisphere split isn’t true”.

Next thing I know, I see a response from Dr. McGilchrist on their website called “The right brain is essential to creativity” where he vociferously replied to my post. Oh man, I unintentionally triggered him! I didn't know the good folks at the Institute of Arts and Ideas were going to ask him to reply to that article, especially considering that post was not originally designed as a criticism of Iain’s work. It was more a response I wrote to the pop psych notion that creativity is only a right-brain phenomena.

Anyway, long story short: I reach out to Iain and explained the situation to him and we had a good laugh about the situation. Our correspondence quickly became friendly, and we started sharing each other’s work with one another. I decided it would make sense to have the conversation in public so invited him on my podcast, and here we are.

I’ve greatly enjoyed going down the rabbit hole of reading Dr. McGilchrist’s work and was pleased to see just how many areas of overlap we have in regards to fascinations, including our attempts to understand the nature of intelligence, creativity and even sacred & transcendent experiences.

This conversation is very rich and I think brings clarity to some important issues in the field of psychology and cognitive neuroscience.

So without further ado, I bring you Dr. McGilchrist.

Scott Barry Kaufman: Iain McGilchrist, it’s an honour to speak with you.

Iain McGilchrist: Well it’s a delight to be here.

S: We have so many areas of mutual interest, as I realised as I went down the rabbit hole that is your large body of work. It’s very rich, and it aligns with many of my own interests in intuition and imagination and intelligence. I can’t help but notice linkages between things you wrote in your 1982 book Against Criticism and things you wrote even in your most recent book, The Matter With Things. You say in Against Criticism, “The understanding of any one thing requires an understanding of the whole of which it is a part.” That seems to capture a lot of your interest in the left and right brain asymmetry, right?

I: It does. At school I already thought that the whole is not the same as the sum of the parts. And wise guys would say to me, “OK, so what’s this extra something that you put in?’ And I didn’t think of saying then: it’s not that something needs to be put in, it’s that something has been taken out in the process of disassembling it. If you disassemble anything, it’s lost its structure, and the structure – the form – may be the meaning. In a piece of music it’s obvious, but also in poetry.

S: Just stepping back a moment, can you explain briefly how you see the major characteristic differences between left hemisphere and right hemisphere?

I: All living creatures have to solve the problem of how to eat without being eaten. In order to get stuff, either food or a tool – in order to manipulate the world, to help us survive – we need to be able to pay scrupulous attention to details of things. But to survive, you also need at the same time to pay a completely different kind of attention to the world. This kind of attention is wide open, sustained, broad, cohesive, integrating and vigilant.

So you need two sufficiently separate neuronal masses that can attend to the world in two different ways at the same time. And these two different kinds of attention create two phenomenological worlds. It took me a while to see that attention isn’t just another cognitive function – attention is how we construct the phenomenological world.

In a very brief sketch, the world of the left hemisphere consists of little pieces of stuff. We already know what these pieces are: they’re familiar, isolated and static so that we can quickly grab them. This world is decontextualized, explicit, abstract, general in nature, and effectively inanimate.

The right hemisphere sees a quite different world in which nothing is ultimately certain. Things have degrees of familiarity but, as Ramachandran says, the right hemisphere is the anomaly-detector and the devil’s advocate, the one that goes: “It could be something else,” so it never sees anything as finally certain or finally separate from anything else. Nor is it static: it’s flowing and changing all the time. It takes in the implicit, which means that, in terms of human psychology, it is the right hemisphere more than the left that enables us to read between the lines, to realise the implicit meaning in metaphors, poetry, and irony.

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I’m obsessed with the default mode brain network, because I think that network offers us the core of human experience, of what it means to be really human.

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And this world of the right hemisphere is basically animate. People think I’m saying that in a metaphorical way, but I’m not. If you’re using transcranial magnetic stimulation and you suppress the right hemisphere, people see things and people that they would normally consider to be alive as no longer alive – they see them as mechanical or zombie-like. Whereas if you supress the left hemisphere, they may see things that ordinarily they would think of as inanimate as having animacy, like the sun moving across the sky.

S: I think our research programmes are very consistent. I’m obsessed with the default mode brain network, because I think that network offers us the core of human experience, of what it means to be really human. And I think you’re obsessed with the right hemisphere for the same reason. I think that you and I feel many discussions about human cognition and the brain focus on abstract intelligence, and leave out the experiential – what it means to really be and feel human, the qualia of humanity. Would you agree that we’re actually quite aligned in that way?

I: I’m sure we are. I think researchers have prioritised one kind of thinking over other kinds because it helps us manipulate the world. But it doesn’t necessarily help us understand the world. If you want a crude soundbite, the right hemisphere helps us to understand the world, the left only to manipulate it. And I suppose what we’re both trying to do is to say that there’s far more going on in our brains than the bit that we’re aware of, and that other bit is fascinating. And I think intuition, imagination, these things are very important.

But that doesn’t for me – and I’m sure doesn’t for you – mean any disrespect to science or reason. My work is based very largely on both. But it’s just that they can’t deal with everything. I mean, there are certain things that are not irrational, but they’re just not rational, like music – it’s supra-rational, it’s beyond the reach of reason.

S: This might be a big stretch, but in Against Criticism you disparage analytical criticism – any form of criticism that’s based in absolutes – and you have a quote where you say, “The only application of abstraction is the rejection of abstraction”. You reject abstract intelligence as the predominant view of criticism in that book. It just seems so linked to your modern-day thinking. Am I being crazy in my connection?

I: Not at all, I think that’s exactly right. Of course, it doesn’t mean that I think there’s no value in analysis. I use analysis – for example in the part of the book where I discuss Wordsworth, I do a lot of stuff based on the frequency of certain expressions and so on, which is analytic. But I’m always worried by a process that ends in analysis, because it’s just taken everything apart, and it’s lost the structure, the form, the implicit.

What I realised about works of art is that they must remain implicit, in just the way that a joke must remain implicit – once you’ve explained it, it no longer has any power. Take paraphrasing a poem. There are only so many things that people are going to write poems about – the tragedy of love, the awareness of mortality, whatever it may be – and if you do this process of just analysing the poem then you come up with a handful of dust. You’ve just destroyed something that could move you deeply in your soul. So what I was really saying is, it’s the decontextualising and the making explicit of what needs to remain implicit that is the danger, and so much depends on context.

S: So let’s jump into the fray of the field of human intelligence for a moment. A big part of my PhD dissertation was my annoyance at psychology’s obsessive focus on abstract intelligence, as measured by, for example, Raven’s Advanced Progressive Matrices test. So I developed a theory of dual-process intelligence, that argues that we should just call that explicit intelligence. But we have a whole rich, vibrant implicit intelligence – and I found zero correlation between that capacity and IQ capacity.

I: That’s interesting. I would have thought that a lot of the important intelligence of scientists and mathematicians as well as artists, comes from an intuitive ability. If they lack the intuitive ability they can plod on in science, you know, holding down a good job and being respected, but they’re not going to make the important breakthroughs.

When you look at the experience of those who make breakthroughs – and I look at a lot of them in The Matter With Things – it’s clear that they are often guided by intuition, by Gestalt forms, by even a sense of the beauty of what they’re discovering, more than they are by simply following an analytic procedural way of thinking.

I often say that people who use their intuitions well are people who know how to reason well, and people who reason well are people who have good intuitions – you need both. I’m rather sorry to hear that you found that intuitive intelligence – if that’s really what we’re talking about – is not related to intelligence, because my strong hunch is that it is, and I think I quote some research that suggests that it is.

S: There’s a 0.5 correlation, for sure, between the personality trait “openness to experience” and IQ tests, so that is true in the mean, but that is only a 0.5 correlation. But you’re right, we’re talking about different levels of analysis. Also, we didn’t have any Einsteins in our sample, and you argue that there might be something qualitatively different about those who are fundamentally reorganising a whole field of knowledge, and they might bring their intuition more to bear, than when we talk about creative achievement in the general population.

I: Yes, absolutely. When you look at creativity research, you find that different patterns of activation are associated with different levels of creativity. The very highly creative use their brains differently from the less creative.

Also, the patterns you’re looking for must be tested for using a task that is truly creative, but since it’s so hard to set up a situation in which people are going to be creative, researchers are often not really asking subjects to do a profoundly creative thing, but instead to do something more pedestrian. This muddies the waters because when the task is highly creative and when the person is highly creative there is this very strong effect of right-hemisphere preponderance. But it can become reversed as you go down. People who are not so creatively gifted tend to use a sort of second-best mode, which is more analytic. Often the conclusions they come to are not as good as those who were able to proceed in a more intuitive way.

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One of the distinctions between the hemispheres is that the right hemisphere seems to be able to use what the left hemisphere knows, but the left hemisphere doesn’t seem capable of taking into account what the right hemisphere knows.

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S: I think one useful way of approaching this is to realise that the personality domain “openness to experience” has various components. You have intellectual curiosity, which we found out-predicted IQ when it came to creative achievement. So I’m not saying the intellect was not important, but it was important to distinguish between IQ-test performance and intellectual curiosity. Those two things were only correlated 0.5, so there could be people who ace IQ tests but don’t have a shred of intellectual curiosity or intellectual openness, and vice versa. So that was one important distinction we wanted to make.

And in the openness domain you also have openness to fantasy and imagination. There are plenty of people who score sky high in IQ tests, but who aren’t particularly imaginative. And then there’s openness to aesthetics – openness to beauty and the arts – and openness to emotions. These specific subfactors can break apart in interesting ways. Maybe the extraordinarily creative humans of our species are really good at integrating or experimenting with all these various ways of being.

I: Yes. One of the distinctions between the hemispheres is that the right hemisphere seems to be able to use what the left hemisphere knows, but the left hemisphere doesn’t seem capable of taking into account what the right hemisphere knows. And it’s also possible for the right hemisphere under certain circumstances to apply local attention just as effectively as the left, but it’s not possible for the left hemisphere to apply global attention as effectively as the right. So it’s probably going to be the right hemisphere that’s better at bringing things together in this way.

And I have found, contrary to anything I had previously assumed, that the right hemisphere is more important for IQ. And I’m not really surprised by this, because a lot of it is to do with things like pattern recognition. I mean, it’s a long time since I did an IQ test, but I think there were questions where you had to see what a series implied by looking at shapes and seeing which one was the odd one out and so on. That seems to me very Gestalt and right-hemisphere sort of orientated. I might be wrong.

S: Can I push back on that? If you look at IQ sub-tests that are more visually loaded than verbal loaded, then you do find more right-hemisphere activation. But all the most recent data I’ve seen on general intelligence – when you look at the common variants across various sub-tests – shows that general intelligence is more left-brain activated, because it is involved in abstraction and logical reasoning. I think that’s replicated by enough studies now.

I: Well, I’d be interested in that. But there are problems when you look at what’s active in a brain when it’s, say, doing an IQ test. It’s probably going to be loaded towards the left hemisphere, partly because the only way that one can often test things is going to involve some degree of articulation or verbalising, and that is going to automatically bring in the left hemisphere.

When one is looking at any kind of faculty, I like to bring together measurements in intact humans with what we know about bits of the brain that have suffered an insult – a stroke, a tumour, an injury. Strikingly, when you compare people who prior to one of these events had an IQ measured and after the event their IQ was measured again, where there are substantial drops the injury was almost always in the right hemisphere, not in the left. Now I know you can argue the pros and cons of deficit literature, but you can also argue the pros and cons of imaging literature, and I think that bringing into the picture the deficit literature is quite important.

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S: I agree. We can bring in the deficit literature – specifically, the savant literature – and give a complete counterexample to what you just said, though. Savants tend to have very low IQs but they tend to display an extraordinary ability that seems to become unlocked when you are more right-hemisphere focused, suggesting an important distinction between the kind of left-hemisphere IQ logical, abstractive performance, necessary to score high in IQ tests, and the type of intelligence that is unlocked by the right hemisphere. I think it’s important to recognise that intelligence as a construct seems to be richer and deeper than just IQ-test performance.

I: I of course agree, but I’m not sure that I would accept that that contradicts what I was saying. Most noncongenital cases of savant syndrome come on after injury, and the injury is often to the left hemisphere, and that releases the right hemisphere to be, as it were, more intelligent in certain ways. So I’m not sure that is a counterexample, and I’d just like to mention the research done by, is it Allan Snyder?

S: Allan Snyder, yeah, the nine-dot problem.

I: Yeah, the nine-dot problem. This is amazing because – I know you know all of this – his research appears to show that the nine-dot problem, which is extremely difficult to solve within the time that the test allots, was unsolvable by people who had their left-hemisphere activity augmented and their right-hemisphere activity supressed, but was solved by a staggering forty per cent of those who had their right-hemisphere activity augmented and their left-hemisphere activity supressed.

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There is a tyranny of language that the left hemisphere contributes to with creative thinking.

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S: It’s great! You’re saying, and I agree, that a lot of IQ test batteries miss creative insights. That’s not what they’re measuring. There’s a lot of cognitive processes relating to creativity and imagination and insight and metaphor and frame-shifting that the right-hemisphere contributes to that is not tapped into by measures of general intelligence.

I: Yes, and you know there are armies of psychologists making a fat living out of going around telling organisations that they shouldn’t trust their intuitions. But actually a lot of the mess we’re in now is because we’ve consistently failed to honour our intuitions for a long time. Intuitions are fallible, of course, but then so is merely looking at the world logically. With intuition, you can bring together, subtly, various strands of thought and reasoning and experience and so on and come to a conclusion which is subtler than anything that would happen if you linearly argue.

S: I love that, I’m right there with you. And there is a tyranny of language that the left hemisphere contributes to with creative thinking. I’ve seen some really cool research showing that the right hemisphere is important for accessing non-dominant meanings of words in unusual associations. There’s a test called the remote-associations test, and the left hemisphere gets in the way of that. When I say, “How many uses of a brick are there?” your left hemisphere wants to give the most obvious answer. If you can just get rid of that then you access a whole depth of unusual associations.

So, mapping on the network approach to the left-brain, right-brain approach, you’ve got me thinking about it in a much deeper way than I ever have before. These are just different levels of analysis, and they’re both probably saying the same thing. I’ve been arguing against the tyranny of the executive attention network, where you’ve been arguing against the tyranny of the left hemisphere, but conceptually I feel like we’re both bothered by the same thing.

I: I think that’s right, there’s a lot of overlap.

This conversation took place on the Psychology Podcast.