Anil Seth’s quest to understand the biological basis of conscious experience is one of the most exciting contributions to twenty-first-century science.
What does it mean to “be you”—that is, to have a specific, conscious experience of the world around you and yourself within it? There may be no more elusive or fascinating question. Historically, humanity has considered the nature of consciousness to be a primarily spiritual or philosophical inquiry, but scientific research is now mapping out compelling biological theories and explanations for consciousness and selfhood.
Anil Seth is Professor of cognitive and computational neuroscience at the University of Sussex, co-director of the Sackler Centre for Consciousness Science and in his new book, BEING YOU: A New Science of Consciousness, he argues that we do not perceive the world as it objectively is, but rather that we are prediction machines, constantly inventing our world and correcting our mistakes by the microsecond, and that we can now observe the biological mechanisms in the brain that accomplish this process of consciousness.
In this interview, I speak to Anil Seth about the fundamental nature of consciousness, how we perceive the world around us, our selves, and how the science of consciousness is helping to unlock who we are.
Q: What is consciousness, and why do we need it?
[Anil Seth]: Consciousness is used by different people in different ways, and while it’s hard to fix on a definition everyone will agree on, it’s important to get at least some idea of what we’re talking about. To an extent, everyone knows what consciousness is to some extent; it’s what goes away when you fall into a dreamless sleep or go into general anesthesia, and what comes back when you wake-up or come around. My preferred definition of consciousness is that it’s the presence of any subjective experience whatsoever. The philosopher, Thomas Nagel, put it like this, ‘for a conscious organism, there is something it is like to be that organism…’ – there is something it is like to be me, to be you, to be a dolphin – but there’s probably nothing like what it is to be a chair, table, or iPhone.
People often load onto consciousness aspects that are not fundamental to it – for instance, a sense of self. That sense is very central to the human experience of being consciousness – that we associate it with being a particular individual. That might even be the most important part- but- you can imagine consciousness happening in the absence of a conscious ‘person’ or ‘subject’ – it’s just experience. Certain states of meditation or psychedelics might even achieve this level of ego dissolution. Consciousness is not the same thing as intelligence either – we don’t have to be smart in order to be conscious – the feeling of pain when you step on a nail is certainly a conscious experience but doesn’t require intelligence or rational thought.
Consciousness is any kind of subjective experience whatsoever.
Q: What is the real problem of consciousness?
[Anil Seth]: Consciousness is a difficult concept to get your hands on scientifically, and therefore it was not a legitimate or widespread mainstream part of neuroscience or psychology fo most of the last century. I was quite lucky coming into this field about 25 years ago when the tides changed.
There are different problems that people associate with consciousness. I use the term real problem as a reference to the philosopher David Chalmers who distinguished between hard and easy problems. It’s not those easy problems are simple to solve, but rather that there are no conceptual mysteries associated with them. How the brain works as a mechanism, how it guides our behaviour, how it takes-in sensory input. Those are all extremely complex, but we can imagine a sufficiently complicated mechanism is up to the job, even if we don’t know precisely how. In the same way… I’m confident there’s some explanation of how a Boeing 787 flies, but I don’t know how the damn thing works. Those are the easy problems.
The hard problem for Chalmers is why- and how- any of these complex (explainable) mechanisms give rise to, or could be identical to, any kind of experience whatsoever. Why doesn’t it all go on in the dark? This grand mystery seems resistant to the scientific approach altogether.
That’s why in trying to solve the hard problem head-on, people come with quite far-out theories. Perhaps- they say- it’s something to do with quantum mechanics… or perhaps consciousness is everywhere… I prefer to think of the problem in a different way. Consciousness exists, it’s real. That’s the place we start from. We have conscious experience, and we know it’s something to do with the brain. You change the brain? You change consciousness. The question is how and why these relationships between brain, body and consciousness play out.
We know, for instance, what we refer to as the colour red in terms of photons and wavelengths – but can we explain the experience of redness? And how that is different from the experience of pain or complex thought? That’s what I call the real problem of consciousness – an indirect way of solving the deep mystery.
Q: What is perception, and how does it relate to consciousness?
[Anil Seth]: The question of perception is a broad problem in psychology and neuroscience. How does the brain transform ambiguous, noisy sensory signals into a rich perceptual scene? The way I prefer to think of perception is as a processor of active construction, a controlled hallucination. This is sometimes counterintuitive. It seems as if the world out there has all these properties like redness, shape, and temperature and that we detect these through our senses and something in our brain reads out this information from the outside world. In this view, perception is a bottom-up outside-in process. You can build systems that perceive things this way, and that’s not entirely wrong per-say, but it’s missing the central part of the story which is the context of what we perceive. When I perceive something as being red, it’s not just sensitive to an externally existing redness. Redness is coming from within my brain, as a way of predicting how certain patterns of light appear, how surfaces reflect patterns of light. Sensory data by itself is not red, it’s not anything. It’s just energy. Sensory signals don’t come with labels attached. Everything we perceive is a kind of inference, a burst guess about what’s out there. The question for me is how we use these ideas to explain not just what we perceive ‘oh, I perceive a cup because a cup is somehow there…’ but why the experience of cupness is the way it is. What is it about the predictions that my brain is making that makes the experience of cupness different from the experience of tomatoness, jealousy or something very different?
If we start to think of perception as a construction then, indeed, we all inhabit distinctive inner universes. We all see and experience the world in a slightly different way. We all know this is true to some extent. There are some extremely viral examples such as the dress which people perceived as being different colours – these things go viral and get popular because they reveal something that is essentially true but often hidden- that people can be exposed to the same image or be in the same place and be having very different experiences.
Understanding perception has a lot of consequences for our understanding of how diverse groups of people experience and believe things about our world, and thus has a lot of consequence in understanding who we are.
Q: To what extent is our subjective experience of the world a probabilistic experience of the world, rather than experience of how things are?
[Anil Seth]: Think about your vision for a moment. If you reflect on your visual experience, it doesn’t seem probabilistic at all, right? It seems determinate. You’re looking at a computer screen, you’re hearing me saying a particular thing and if our video-call is working correctly, it should leave very little ambiguity. Under the hood, there’s a mess of probabilistic calculations. In the 19th century, the philosopher, physicist, and psychologist, Hermann Von Helmholtz talked about this. He thought perception was this process of unconscious inference. The inference part is all the wizardry inside the skull that’s dealing with probabilities. The output of that- most of the time- is that we perceive a determinate world. Is perception really that determinate and unambiguous though?
Think about your peripheral vision. Not the vision in the centre, but out to the side. We know sensory sensitivity is low in the periphery, there aren’t many light sensitive cells that respond to that part of your visual field – yet you still ‘see’ what’s out there albeit not as richly as the centre. You experience it consistently with the centre of your visual field, it doesn’t feel blurry. There’s a sense in which experience itself becomes a bit statistical in the fringes- and for me, that’s the fascinating and understudied aspect of perceptual experience.
This exposes the whole real problem approach to consciousness. When you say, oh yeah, I see a cup… it’s the result of signals, and how your whole visual experience is structured based on probabilistic activity inside your skull!
Q: How does aesthetic experience relate to consciousness?
[Anil Seth]: Aesthetics are super-interesting, but I’m suspicious about the neuroscience of aesthetics such that people are put in scanners, made to look at Picassos and scientists look at which part of the brain activates. I do think there’s something rich to be said here. The art historian, Ernst Gombrich, came up with the idea of the beholders share. This is the idea that in the observation of a piece of art, it’s not just a passive registration and conceptual analysis like oh yeah, this is a Picasso and therefore it’s supposed to look a bit weird in this way. The observer is bringing something to the process of perceiving the artwork- they’re bringing their expectations, context, background, and history to any given perceptual experience. This is very similar to what Helmholtz was saying in psychology and what we’ve been talking about in terms of perceptual experience in this inside-out prediction. From then you can ask, why do certain artworks or visual experiences have aesthetic contents? I’m drawn here quite often to thinking about impressionist art like Monet or Pissarro which have a beautiful incompleteness- they’re just scratches and blobs on canvas but done so well that the brain is drawn into completing the image. That’s partly why paintings like that have such aesthetic appeal- because they’re engaging the mechanisms of the brain in completing the picture, thus giving an inherent sense of satisfaction.
This links to emotions which are – at least in my view – part of the same realm of existence as perception or belief. Emotions are perception, but perception of the body itself. Psychologists like William James and Carl Lange have said this – talking about emotion not as a response to an external world that is created by the body to put the body in a certain state, but as perception of the body responding to the outside world. You see something scary like a bear, that triggers all kinds of physiological changes in your body. Your heart rate increases, your breath quickens, and the perception of those changes is the emotion. Finally, of course you have perception which is not just reading the body, but making an inference – a best-guess- of what’s going on in the body alongside all the other inputs. Emotion is another kind of controlled hallucination but geared to the interior of the body rather than the outside world.
Any perceptual experience that we have is constituted partly by predictions about signals from the outside world, and partly by signals from within the body in the context of that world.
Q: What are we referring to when we think of the self?
[Anil Seth]: There is some identity that persists over time that is- in some sense- real. This identity receives all these sensory signals and is doing the perceiving, planning actions, holding beliefs, and thinking thoughts.
Self can be thought of as just another perceptual experience. It perhaps has many different parts- memory, emotional experience, the experience of agency, and the things we associate with the very slippery concept of free-will. There are a lot of things that get bundled together in our ongoing experience of being who we are – but instead of explaining all that in terms of there being an indivisible, eternal, persistent and perhaps removable ‘essence’ it is more satisfying and accurate to think of selfhood as something like a process… something that unfolds over time as a bundle of perceptions that come together in different ways in different people, animals, and which can come apart with degenerative disease.
The study of degenerative diseases like Alzheimer’s and Parkinson’s together with the study of psychiatric disease and brain injury show us that the self is precarious and fragile. Different parts can be lost while other parts remain. It’s possible for somebody to entirely lose their ability to lay down new memories. They’ve lost a core part of their personal identity, but every other aspect of selfhood is still there. Other people can lose different aspects of selfhood. Some people can lose their ability to perceive their body as being their own or lose the ability to experience intentions over actions (schizophrenia). All these things point to a central truth – that there is no indivisible essence of selfhood, but nonetheless we do experience it that way.
It’s not that I now have a different experience of selfhood from you. I still experience being me as something that is persisting and real, but in the sense that I know redness doesn’t exist out there in the world as an observer independently, I know I don’t either.
Q: What is the relationship of body to consciousness?
[Anil Seth]: The fundamental reason we have brains is not to do complex abstract thinking but to keep the body alive. That’s the fundamental duty of the brain – to regulate the physiology of the body such that it continues to persist over time. Perception of the body is geared towards keeping it going, and a good way to do that is to experience it as having some sort of unchanging target state- homeostasis or allostasis… some region of viability that bodies and mental states have that keeps us going. For me, that’s the real ground state of being a ‘self.’ It’ s a self-fulfilling perception of the body as continuing to exist over time. If you think this way – it means that consciousness, especially what it means to be a self, is very closely tied to our nature as living creatures.
This goes against the grain a bit when we think about the last 50 years when we’ve had computers, AI and other technologies that have relegated the importance of the body to being this unreliable meat-robot that moves our brain from meeting to meeting. It’s not like that at all. The body is essential to how we are, how we experience being a self… Conscious selfhood is not just going to shimmer into existence when machine learning crosses some unknown threshold, at least I don’t think it will… I think conscious selfhood requires a body and that the brain is in the business of keeping alive.
Q: What are the consequences of ‘solving’ consciousness?
[Anil Seth]: A better understanding of the mechanisms of consciousness will help us develop better approaches to psychiatric medicine, neurology, and smarter machines. All that is true. But… the real consequence of ‘solving’ consciousness would be how we understand our place in the universe.
A satisfying scientific and philosophically informed account of consciousness would pretty much change everything.
In some cultures, we come equipped with an intrinsic drive to think of ourselves as somehow separate from nature… a bit at the top of everything… somehow special. That’s been quite characteristic of human thought… such that we think about ourselves at the centre of the universe (quite literally in the pre-Copernican days), at the centre of everything else, and perhaps even God.
Over the last few centuries, science has radically overturned human anthropocentrism- we no longer see ourselves at the pinnacle or the centre. We’re not the centre of the universe, we’re in some backwater somewhere on the Western spiral arm of one of thousands of galaxies. The Pale Blue Dot photo had a remarkable impact on the way we see ourselves as a species. It showed us to be this tiny blue crystal hanging in the vast abyss. We see ourselves now more as part of the universe. Then Darwin came along and revealed that we’re not some special creature that’s fundamentally different from every other living creature, but rather that we’re one twig on this beautifully rich and delicate evolutionary tree. We’re built into the tapestry of life.
Consciousness is the one remaining aspect where- at the moment- we still see ourselves as separate. We think of our rational minds as being closer to God than animals. We have the hard problem of consciousness that says no, consciousness is so different from everything that it cannot be part of the physical picture of the universe. When we get there and when we have a picture and explanation of consciousness continuous with our understanding of the rest of the world- it might be a bit frightening in the same way that the realisation of how vast our universe is can be frightening. Ultimately, it’s rewarding us. Science takes us away from being at the centre and gives us far more back in return. We understand how much richer, more marvellous, and beautiful our universe is and how our place in it is not unimportant, but part of a much bigger story.