The material soul
Anil Seth explores what neuroscience can – and can’t – tell us about consciousness.
Over the past decade, our sense of ourselves as largely rational, self-determining beings has been called into question. And from nowhere have more doubts been cast than the field of neuroscience. Popular science writers and philosophers, like David Eagleman and Daniel Dennett, tell us our agency is an illusion, that love consists of neurons firing in the caudate nucleus, that Wordsworth’s poetry is pleasurable because it stimulates certain neuronal pathways. It can sometimes seem that we are nothing more than that tofu-like substance sequestered away in our craniums.
But is that true? Are we to be reduced to our brains? Is neuroscience about to unravel the mystery of human consciousness and banish the ghost from the machine once and for all? Who better to ask than Anil Seth, a professor of neuroscience and the co-director of the Sackler Centre for Consciousness Science at the University of Sussex.
spiked review: What can neuroscience tell us about consciousness?
Anil Seth: In general terms, neuroscience is the study of the brain. Most of neuroscience has very little to do with the study of consciousness. If you attend the Society for Neuroscience’s annual meeting, you’ll find about 30,000 people there, and the majority of the meeting will be about this or that cell type, or this or that receptor. It’s very low level, very important stuff, but a lot of it you could study in a worm, or another very simple organism. And it’s not directly related to how we experience the world.
Within neuroscience, you have cognitive neuroscience, which is more about how the brain underlies cognitive functions that potentially involve conscious awareness – vision, perception, memory, etc. But even then, we’re not conscious of all our perceptions. And we’re not conscious of the mechanisms themselves: for example, we’re not generally aware of how particular memories spring bring back to mind or how our visual cortex constructs a rich visual scene.
Consciousness science, then, is specifically about understanding the brain mechanisms, and the psychological mechanisms underpinning consciousness – all the causal factors that directly impact our subjective experience of the world. So it’s a subset of neuroscience, but it also asks questions that go beyond neuroscience – what it is to be a self, and so on.
review: Are you able to give a neuroscientific definition of consciousness?
Seth: There’s a frequent misunderstanding that a scientific explanation of a phenomenon first needs a definition everyone agrees is the right one. Almost any talk I give, people will always ask, ‘can you define consciousness?’. But if you look at the history of science, definitions continually evolve. Life is a good example. Definitions of life have evolved along with our understanding of it. The gene wasn’t really defined until scientists had figured out that there was something that was a hereditary basis for organism characteristics.
It is sometimes possible to measure how well a science is progressing by how the definition moves from something that is quite descriptive, to something that is quite mechanistic. So, at the moment, our definitions of consciousness remain quite descriptive. But as long as we’re not labouring under some quite weird definitions, it’s enough.
As I see it, consciousness is the presence of a phenomenal world. There is some sort of experience happening – the presence of any kind of experience. Now that’s very, very general – by itself it’s not going to generate a theory – but it places itself against other definitions, which might say, for instance, that consciousness is dependent on language, or is some kind of quantum fluctuation.. So consciousness is any kind of experience, an experience of pain, of suffering, of joy. It includes our sense of body, our memories… For a conscious organism, there is something it is like to be that organism – that is my basic definition of consciousness.
review: What do you mean by a mechanistic definition?
Seth: Take temperature, for example. A descriptive definition is saying that something feels hot, or that something feels cold. Then you have definitions that are based on the behaviour of liquids under certain conditions – the boiling point of water in a smooth vessel. This was actually very hard to establish. At one point, a zero-point for temperature was defined for a while as the temperature of a piece of cheese in a basement in Paris, because that was assumed to be the most stable baseline. But now we have a definition of temperature which is very mechanistic, namely, the mean kinetic energy of a bunch of molecules, and this is based on a well-developed physical theory of what temperature is, and extends way beyond our experience of temperature. We can now define absolute zero; and we can define temperatures in the middle of the Sun, which far exceed what would feel hot or cold to us.
In the same way, currently we have a descriptive definition of consciousness as the presence of any kind of subjective experience. We can refine that subjective definition by saying, there’s being conscious at all, there’s being conscious of colour, or this particular object, and there’s consciousness of being a self. This is still all descriptive. But then I might say that when you’re conscious at all, there’s this particular mechanistic process unfolding in your brain, and right now we’re at the stage of trying to figure out what that process is. Consciousness seems to depend on a particular dynamic pattern the brain organises itself into. There are some very specific theories that it’s to do with the amount of integrated information generated by the brain’s dynamics that can be quantified in various ways. And if that turns out to be predictive and explanatory about being conscious, then we would have an increasingly mechanistic definition of consciousness that was framed in something other than its subjective experience or phenomenological description. So there are some candidate definitions in terms of information theory and other sorts of mathematical descriptions of the brain’s activity. But they’re still at a very early stage. We are not in a position to say what consciousness actually ‘is’ at the level of brain mechanism. We’re still at the stage of saying, ‘if consciousness is related to this particular pattern of brain activity, can we measure it? Can we predict consciousness under anaesthesia?’ And so on.
review: Your description of the state of the science of consciousness, and its ambitions, seems a far cry from the grander claims made for neuroscience – that our political leanings, our artistic judgement, love even, can all be reduced to, and understood in terms of, brain functioning. What do you make of those claims?
Seth: There is an unfortunate tendency to plonk the word ‘neuro’ in front of a particular field of knowledge or aspect of culture and treat it as an explanation of that thing. So you can have neuro-aesthetics, neuro-marketing, neuro-architecture, neuro-politics. Some of this might be quite interesting, because we live in a social world where politics, aesthetics and marketing play important roles, so there’s some value to studying brain responses to these aspects of our environment. But neuroscience here doesn’t by itself generate any explanations as to why, say, we value a particular painting or vote a certain way. So the worst kind of theory is one that says the fact that you are a left-leaning liberal, but still want to keep a nuclear deterrent, is explained by, let’s say, the increased activity in your left-inferior-parietal cortex. It doesn’t explain anything of the sort. It’s a reductive account, usually accompanied by a nice picture of an MRI brain scan.
Of course you can find correlations between, say, political beliefs and the brain. But the fact that you can find correlations isn’t that surprising given our experience of and engagement with politics does depend on our brains. But that doesn’t mean neuroscience can account for those social or cultural phenomena.
review: It is often claimed that neuroscience puts the brain in the driving seat, and that it undermines free will. What do you make of the challenge neuroscience poses to traditional, liberal conceptions of self-determination?
Seth: A big part of being a self is our experience of determining, or being in control of, our behaviour. We do X but we could have done Y, and we do so in a way that seems not completely constrained by our environment.
So we do have this experience of being the origin of voluntary actions. But we have it selectively. When you quickly move your hand quickly away from a hot stove, you don’t experience any sense of volition. It’s a reflex action. But when making very difficult decisions, having to balance multiple factors, we can have a very strong and actually quite aversive experience of deciding this way or that way, and being responsible for our actions.
So what can neuroscience say about this experience of will? Now, in one sense, the concept of free will is a bit redundant. This is the spooky metaphysical sense in which there is a cause without a prior cause. Some immaterial influence comes in and changes things in the brain to make its activity change in a different direction. It’s a hangover from philosophical dualism – there’s an immaterial soul, a material brain and body, and the soul can interact and change what the brain and therefore the body does. The problem here is the same problem Descartes faced – if you’ve got an immaterial soul how does it interact with the material body?
But, in another sense, one is best off thinking about free will in terms of actions that are accompanied by a sense of volition, and a sense of agency: ‘I intended to do that’; ‘I was the cause of that’. Some of our actions are associated with this experience, and others aren’t. And one of the things that seems to distinguish our experience of volitional acts, as the neuroscientist Patrick Haggard put it, is so-called freedom from immediacy. That is, the extent to which our action is less constrained by the immediate configuration of our environment, the more we experience it as a volitional action, as an internally caused action. So, right now, if I decide to move my arm when nothing in the environment has really changed, then I’ll experience that as volitional.
There’s one famous neuroscience experiment that has often been taken to show that free will doesn’t exist. Back in the 1980s, Benjamin Libet found a brain signal – a ‘readiness potential’ that reliably preceded a person’s awareness of the intention to act. As if the brain knows what you are going to do before you do. But this isn’t mysterious at all, since everything that happens – be it a voluntary action or an experience of volition – must have a prior cause somewhere.
People will worry that a neuroscientific understanding of volition is dehumanising. We’re just our brains, and so on. Well, in one sense, we are our brains. I’m very closely attached to my brain – without it I wouldn’t be anything. But my brain is more than an isolated bunch of neurons. It’s shaped by my upbringing, my environment, my culture, my moral framework. For example, my visual experience of an object can be shaped by my social context. There’s research, for example, that shows that images that look ambiguous, say something that could be a power tool or a gun, will be seen as being gun more in some contexts than others.
The only reasonable free will we should care about is the freedom to act according to our nature. So, if you’re the kind of person who, in virtue of your cultural context, your moral framework and development, is the kind of person who wants to do X in a particular situation, and is free to do X, then that’s the only type of free will that matters.
review: Do you think that that those moments of decision, when it feels like we are determining our own lives, are illusory?
Seth: No, I don’t think they are illusory in general. Most experiences of volition and agency happen when our behaviour has a ‘freedom from immediacy’ and is more reliant on internal causes. There are, however, some exceptions. In certain pathological cases, for instance, people can make voluntary actions but not experience them as voluntary – this is typically called alien-hand syndrome, where I might make an action but I wouldn’t experience it as being under my control, even though it is. I might be doing something to reach a goal – cooking food to eat, for instance – but I wouldn’t experience it as such. You get related phenomena in some types of psychosis, where I believe I’m being controlled by the TV or the CIA, and so on. So, affected individuals make the same actions they might make voluntarily, but they lose the sense of volition that normally attaches to those actions. And we can also have the opposite thing, whereby something happens, and I wasn’t the cause of it, but I experience myself as the cause – an example is called choice blindness, where I experience myself, wrongly, as having made a particular choice.
review: So neuroscience doesn’t undermine the idea of being responsible for one’s actions? After all, the idea of individual selves being responsible for their actions is at the centre of our legal systems – does neuroscience undermine the law as it exists?
Seth: Western legal frameworks have the concepts of mens rea and actus reus– which means effectively that someone must be in their right mind to be held culpable for a particular action. Certainly neuroscience makes things a bit more complicated in some otherwise difficult cases. But it’s not as if the whole way we think about morality and punishment is suddenly about to crumble because we’re saying what you do depends on your brain. If someone wants to say, ‘I couldn’t help it, my brain made me do it’, one might say, ‘okay, we’ll send your brain to prison’.
So the fact that what you do depends on your brain shouldn’t change whether an action is moral or not, but, in certain cases, it may change how society should respond. There are a couple of famous legal cases that highlight these issues. There’s one where a man stabbed his mother-in-law to death. His defence was that he had been sleepwalking and hadn’t intended to do it –. After considering lots of evidence including brain recordings he was let off, because he wasn’t in his right mind. There are other cases where individuals develop brain tumours and suddenly start behaving anti-socially, and then the tumour is removed and they’re okay again. There’s one case involving paedophilia, where someone developed paedophilic tendencies and then it was found he had a brain tumour. It was removed, and he was fine. But when it grew back, he developed the same tendencies again. These are cases where you can say there is a clear difference in how someone’s brain is from how it would be without the tumour. So in those cases it seems unfair to hold the whole individual responsible. But if their brain is not affected by a disease or some other disturbance, then their guilt or otherwise is not a matter for neuroscience.
Just to be clear, neuroscience is not saying that there is no such thing as free will, and therefore no such thing as individual moral responsibility. Neuroscience is saying that there’s no such thing as spooky, metaphysically weird free will – an immaterial soul. It’s saying that you do make volitional actions, and you do so when they’re more prescribed by your internal state than by your immediate external situation. You make a freely willed action when you do something according to your nature that’s not prevented by the immediate constraints of your environment. And you experience volition and agency. And I think, to all intents and purposes, you are an agent. And you are responsible for your actions. You don’t need an immaterial soul to be held responsible for your actions. If you’re being coerced, then you’re not responsible for your actions. And if you’re being internally coerced, say by a brain disease, then you’re arguably not responsible for your actions either. In any case, science doesn’t tell us what to do – it just tells us how the world, including ourselves, works.
review: You mention one’s nature quite a bit. Given the idea of neuroplasticity, is it possible to change one’s nature?
Seth: Of course. It happens, right? We do change our nature, and often for the better. As Steven Pinker points out, far more were killed in the Second World War than in all the wars since. Against what we see in the news every day, things can sometimes get better.
At a more basic level, the more we look for evidence that the adult brain can change, the more evidence we find that there’s a lot of changeability, a lot of plasticity. Basically the same basic brain structure has allowed human beings over the course of the past thousands of years to adjust to radically different environments. Evolution hasn’t had a chance to rewire our brains or our genetic blueprint, so our brains have evolved to be plastic, to be changeable. The world we live in now is very different to the world of our ancestors, but we have much the same ‘hardware’ up here. So I think that this gives us reason to think of neuroplasticity as a cause for optimism.
Anil Seth is professor of cognitive and computational neuroscience at the University of Sussex, co-director of the Sackler Centre for Consciousness Science and editor-in-chief of Neuroscience of Consciousness. Visit Anil’s website and follow him on Twitter at @anilkseth.