(No 12) - New Scientist Essential Guide_ Consciousness-New Scientist (2022)

ESSENTIAL GUIDE№12 E D I T E D B Y RICHARD WEBB CONSCIOUSNESS T H E O R I E S O F C O N S C I O U S N E S S A N I M A L A N D H U M A N M I N D S T H E S E L F A N D F R E E W I L L S L E E P A N D D R E A M I N G A L T E R E D C O N S C I O U S N E S S C O N S C I O U S N E S S A N D R E A L I T Y A N D M O R E U N D E R S T A N D I N G T H E G H O S T I N T H E M A C H I N E -- 1 of 100 -- -- 2 of 100 -- N E W S C I E N T I S T E S S E N T I A L G U I D E C O N S C I O U S N E S S NEW SCIENTIST ESSENTIAL GUIDES NORTHCLIFFE HOUSE, 2 DERRY STREET, LONDON, W8 5TT +44 (0)203 615 6500 © 2022 NEW SCIENTIST LTD, ENGLAND NEW SCIENTIST ESSENTIAL GUIDES ARE PUBLISHED BY NEW SCIENTIST LTD ISSN 2634-0151 PRINTED IN THE UK BY PRECISION COLOUR PRINTING LTD AND DISTRIBUTED BY MARKETFORCE UK LTD +44 (0)20 3148 3333 EDITOR Richard Webb DESIGN Craig Mackie SUBEDITOR Bethan Ackerley PRODUCTION AND APP Joanne Keogh TECHNICAL DEVELOPMENT (APP) Amardeep Sian PUBLISHER Nina Wright EDITOR-IN-CHIEF Emily Wilson DISPLAY ADVERTISING +44 (0)203 615 6456 displayads@newscientist.com ADDITIONAL CONTRIBUTORS Anil Ananthaswamy, Philip Ball, Michael Brooks, Andy Coghlan, Sofia Deleniv, Liam Drew, Liz Else, Linda Geddes, Alison George, Bob Holmes, Rowan Hooper, Joshua Howgego, Simon Makin, Tiffany O’Callaghan, Sean O’Neill, David Robson, Per Snaprud, Laura Spinney, Helen Thomson, Richard Webb, Caroline Williams, Clare Wilson, Emma Young ABOUT THE EDITOR Richard Webb is executive editor of New Scientist “Afascinating but elusive phenomenon; it is impossible to specify what it is, what it does, or why it evolved. Nothing worth reading has been written about it”. So wrote psychologist Stuart Sutherland of consciousness in the International Dictionary of Psychology a little over three decades ago. Much has changed in the past years. Imaging technologies have given fresh insights into what goes on in the brain as we experience sensations from love to colour to hunger to fear. Biologists have traced where subjective experience first appeared in the tree of life, and the sensations other animals have. Mathematical models are providing new angles on consciousness. But in all this, there is much we still don’t understand about consciousness and its place in the cosmos – not least, the “hard problem” of why there is something it is to be like us at all. This 12th New Scientist Essential Guide looks at this most fascinating and elusive phenomenon in the round, and I do hope it provides food for thought. The other titles in the Essential Guide series can be bought by visiting shop.newscientist.com; feedback is welcome at essential guides@newscientist.com. Richard Webb COVER: PABLO HURTADO DE MENDOZA ABOVE: LUMEZIA/ISTOCK NEXT PAGE: BASHTA/ISTOCK New Scientist Essential Guide | Consciousness | 1 -- 3 of 100 -- C H A P T E R 1 W H A T I S C O N S C I O U S - N E S S ? C H A P T E R 2 C O N S C I O U S M I N D S C H A P T E R 3 Y O U R C O N S C I O U S S E L F Consciousness is the ghost in our machine. It is all there is: the world, the self, all experience. But beyond that, the very subjectivity of consciousness makes it hard to define and harder still to characterise. p. 6 The easy and hard problems p. 8 Five ways to think about consciousness p. 10 Seeking the seat of consciousness p. 12 INTERVIEW: David Chalmers “Why is there something it’s like to be us?” p. 14 Consciousness and the networked brain p. 16 PERSPECTIVE: Christof Koch “Physics overwhelmingly favours consciousness” By asking what the outward signs of consciousness are, and tracing back where they first appeared in the history of life, we might begin to understand why the phenomenon exists – and so learn a little more about what it is. p. 20 Why did consciousness evolve? p. 25 Ten signs of consciousness p. 26 Inside animal minds p. 28 Five elements of consciousness p. 29 Could a robot ever be conscious? p. 30 PERSPECTIVE: Michael Graziano “Consciousness is an engineering phenomenon” A sense of self and its related trait of metacognition, the ability to monitor your own mental states and those of others, are often regarded as the pinnacles of consciousness. In fact, they might be evolutionary accidents, and perhaps even figments of our own imaginations. p. 36 The evolution of the self p. 39 What animals are self-aware? p. 40 Is the self an illusion? p. 42 Metacognition: Knowing that you know p. 44 Your conscious body p. 48 Free will and the self 2 | New Scientist Essential Guide | Consciousness -- 4 of 100 -- C H A P T E R 4 S L E E P A N D D R E A M I N G C H A P T E R 5 A L T E R E D C O N S C I O U S - N E S S C H A P T E R 6 C O N S C I O U S - N E S S A N D R E A L I T Y The true purpose of sleep remains unclear, but among organisms with some degree of consciousness, it seems near-universal that they spend some time in a reduced state of it. Exactly why is a big question – as is the meaning of the many different states of consciousness we seem to enter in our non-waking hours. p. 52 Why do we sleep? p. 55 Your brain while sleeping p. 57 Hypnagogia p. 57 The meaning of dreaming p. 58 When dreams happen Many altered states of consciousness exist, from anaesthesia and natural or drug-induced hallucinations to minimally conscious states such as comas. In all cases, what is going on in our brains is far from clear-cut. p. 62 The mystery of anaesthesia p. 66 The power of hallucination p. 68 Psychedelia: A higher state? p. 69 Curiosities of consciousness p. 70 Free won’t p. 71 Covert consciousness p. 73 Six reduced states of consciousness p. 74 What happens to consciousness when we die? p. 75 PERSPECTIVE: Daniel Bor “Consciousness is about combining information” The relationship between our internal world and the external one – how the processes of physics contrive to produce consciousness and also, perhaps, how consciousness influences the processes of physics – is another of the great mysteries of consciousness, with as yet few answers. p. 80 The physics of consciousness p. 84 Does consciousness create reality? p. 88 Is the universe conscious? p. 93 PERSPECTIVE: Anil Seth “We need to solve the real problem of consciousness” New Scientist Essential Guide | Consciousness | 3 -- 5 of 100 -- 4 | New Scientist Essential Guide | Consciousness 4 | New Scientist Essential Guide | Consciousness C H A P T E R 1 Consciousness is the ghost in the machine. It is, for each of us, all there is: the world, the self, all experience. But the very subjectivity of consciousness makes it difficult to define, and harder still to characterise. How do our brains create conscious experiences and a feeling of being? Why do we have these sensations at all? These are unanswered questions that lie at the heart of the mystery of consciousness. -- 6 of 100 -- Chapter 1 | What is consciousness? | 5 Chapter 1 | What is consciousness? | 5 -- 7 of 100 -- 6 | New Scientist Essential Guide | Consciousness ONSCIOUSNESS is a slippery concept. It isn’t just the stuff in your head; it is the subjective experience of some of that stuff. When you stub your toe, your brain doesn’t merely process information and trigger a reaction: you have a feeling of pain. Being in pain; experiencing joy; smelling onions frying; feeling humiliated; recognising a friend in the crowd; reflecting that you are wiser than you were last year – all of these are examples of conscious experiences, sometimes termed “qualia”. The mysteries starts with what those experiences are made of. In the 1600s, the philosopher René Descartes famously divided the universe into “mind stuff” (res cogitans) and “matter stuff” (res extensa), raising the conundrum of how the two might ever interact. He was convinced that the body and conscious mind are two different substances: the first is made of matter, the latter is immaterial. Today, most – although not all – scientists reject this strict “dualist” perspective. The relatively orthodox PABLO HURTADO DE MENDOZA PREVIOUS PAGE: LUMEZIA/ISTOCK > THE EASY AND HARD PROBLEMS Among scientists and philosophers grappling with the mystery of consciousness, a popular division has sprung up in recent decades – between asking what it is made of, and why it exists at all. Neither question is easy to answer, but one is distinctly harder than the other. -- 8 of 100 -- Chapter 1 | What is consciousness? | 7 -- 9 of 100 -- 8 | New Scientist Essential Guide | Consciousness scientific view today goes by the name of physicalism (see “Five ways to think about consciousness”, right). Consciousness is related to or emerges from physical matter, in particular the firing of neurons in our brains. But how does the brain, a physical object, generate the non-physical essence that is consciousness? In the final years of the 20th century, philosopher David Chalmers at New York University made an influential distinction between two aspects of consciousness: the “easy” and the “hard” problems. The “easy” problem consists of explaining the brain processes associated with consciousness, such as the integration of sensory information, learning, thinking and the states of being awake or asleep. These problems are called easy not because they are trivial, but because there seems no reason why they can’t be solved in terms of physical mechanisms – albeit potentially very complex ones. →- Chapter 4 looks at sleep and dreaming in more depth- The hard problem, which Chalmers introduced at a scientific meeting in 1994, is to explain why we have subjective experiences at all. “Consciousness poses the most baffling problem in the science of the mind,” said Chalmers. When we think and perceive, there is a “whirr of information-processing” in the brain, as he put it, but also very distinctive, subjective states F I V E W A Y S T O T H I N K A B O U T C O N S C I O U S N E S S D U A L I S M Brain and mind are two separate things, and conscious experiences can’t, in all probability, be fully explained through the workings of physical matter. M O N I S M Brain and mind are the same thing, and consciousness is ultimately a phenomenon that derives from the workings of matter – in humans, the matter of the brain. The dominant subgenre of monism today is… P H Y S I C A L I S M Existing laws of physics governing electrical and chemical signalling in our brains are ultimately enough to explain consciousness and the workings of our minds. Understand these workings, and we should be able to “see” the physical markers of different conscious experiences, and so know what other people are experiencing. P A N P S Y C H I S M Deriving from the idea that consciousness is a fundamental component of the universe in its own right, this suggests that all matter – perhaps even inanimate objects like rocks – are imbued with some degree of consciousness that may or may not be explained by current matter-based physics. If we can find a measure of consciousness, we can quantify how much different objects have. I L L U S I O N I S M Illusionists agree with physicalists that our conscious experiences have a physical basis in the workings of the brain, but argue these are illusory experiences derived from our brain’s processes for monitoring itself, and don’t themselves represent “real” properties of the world. TIM UR/ISTOCK -- 10 of 100 -- Chapter 1 | What is consciousness? | 9 of mind. We don’t just perceive the world; we feel it. Conscious thought can influence the body and the world: a conscious desire to move your arm results in physical movement. →- Chapter 6 discusses consciousness and- reality in more depth- These experiences seem, to an external observer, fundamentally unknowable. What is someone else’s experience of grief, or pain, or the smell of onions, or the colour red actually like? Thomas Nagel, also at New York University, expressed this conundrum famously in the 1970s when he asked: “What is it like to be a bat?” You could know every detail of the physical workings of a bat’s brain, but still not know what that bat is experiencing. When it comes to the hard problem, opinions differ wildly. Adherents of the illusionist school of thought dismiss the problem out of hand, and say that the hard problem creates an issue where there is none. We don’t normally talk about our qualia, they say: we talk about things such as being tired, needing to eat or even being in love. All of these phenomena have relatively straightforward, non-spooky biological origins in things such as the workings of hormones in our body. And if we experience a strawberry as “red”, say, it isn’t because the real world is like that, but because our visual systems effectively colour-code the world for us to simplify it. And much as colour is an illusion created by the brain, so, too, is consciousness and our sense of self. “Consciousness is a user illusion designed by evolution to make life easier for the brain that must guide a body through a perilous life,” says philosopher Daniel Dennett at Tufts University in Massachusetts, a prominent illusionist. If our brain is a smartphone, consciousness is the screen and individual experiences are icons on it, our interface to the brain. →- See chapter 3 for more on the conscious self- The metaphor isn’t exact: when we feel dizzy or pinpoint where a sound is coming from, for example, it is the result of physical processes in the brain. In that sense, you might think of consciousness as more like a smartphone screen that presents different apps according to the amount of battery left or how much it has been shaken. That remains a minority view, however: most researchers believe that consciousness is a real phenomenon, and that by delving into the mysteries of the brain’s workings, we can illuminate its nature. But that is far easier said than done. ❚ What does the colour red look like to someone else? -- 11 of 100 -- 10 | New Scientist Essential Guide | Consciousness ACK in 1998, two young men sat in a smoky bar in Bremen, northern Germany. Neuroscientist Christof Koch and philosopher David Chalmers, originator of the “hard problem” of consciousness, had spent the day lecturing at a conference about consciousness, and they still had more to say. After a few drinks, Koch suggested a wager. He bet a case of fine wine that within the next 25 years, someone would discover a “neural correlate of consciousness” – a particular pattern of brain activity that relates to a given conscious state, such as the experience of a painful toothache. Chalmers said it wouldn’t happen, and bet against. The wager was rooted in the dominant physicalist school of consciousness – that consciousness is a real phenomenon whose physical origins can be uncovered – and particularly in an approach to the problem that Koch, now president and chief scientist of the Allen Institute for Brain Science in Seattle, Washington, had pioneered together with the co-discoverer of DNA, Francis Crick. In his work on DNA, Crick had reduced the mystery of biological heritability to a few intrinsic properties of a small set of molecules. He and Koch thought SEEKING THE SEAT OF CONSCIOUSNESS What is being in love, feeling pain or seeing colour made of? How our brains construct our conscious experience has long been a riddle – but we are slowly uncovering clues. consciousness might be explained using a similar approach. Imaging techniques such as electroencephalography (EEG) provided tools with which researchers could look at the brain’s patterns of activities while performing all sorts of different tasks, in the hope of finding physical signatures of specific conscious experiences. One early surprise was that the cerebellum, a sort of mini brain hanging off the back of your cortex that contains about three-quarters of the 86-billion-odd neurons in the brain, seems to have almost nothing to do with consciousness. One reason we know this is because some people are born without a functioning cerebellum, and while they experience some problems, a lack of consciousness isn’t one of them. Frustratingly, similar observations have undermined most suggestions of a “seat of consciousness” within the brain. Take the notion, which Koch and Crick favoured for a while, that a sheet-like structure beneath the cortex called the claustrum is crucial for consciousness. There was reason to be optimistic: a case study in 2014 showed that electrically stimulating this structure in a woman’s brain caused her to stare blankly ahead, seemingly unconscious, until the stimulation stopped. But another study described someone who remained fully conscious after his claustrum was destroyed by encephalitis, undermining that idea. -- 12 of 100 -- Chapter 1 | What is consciousness? | 11 Some bundles of neurons do appear to be vital for consciousness, however. If damage occurs to specific parts of the thalamus, or to a particular region of the brainstem, for instance, the result can be permanent unconsciousness. But the question remains whether these brain regions are central to generating conscious experiences, or whether they are more like a power socket that simply allows whatever is plugged into it to work. Some researchers ascribe a vital role to the prefrontal cortex (PFC), which is responsible for sophisticated cognitive processes including attention, decision- making and planning. They argue that for information from the outside world to become a conscious perception – for you to actually see a red apple, say – it has to be processed not just by the part of the brain responsible for that, the sensory cortex, but also by the PFC. Neuroimaging studies of people and macaques support this idea, but sceptics say that the PFC activity these show could relate to thinking about a stimulus and planning a response, rather than being conscious of it. And again, there are people who have had large regions of their PFC surgically removed due to tumours or epileptic seizures. “They go on living, by and large, a normal life, never complaining that they have been turned into zombies,” says Koch. In 2021, Omri Raccah at New York University and his colleagues conducted a review of the evidence and concluded that stimulation of only two regions of the PFC, the orbitofrontal cortex and the anterior cingulate cortex, sometimes alters reports of conscious experience. It seems likely that they support emotional aspects of conscious experience, as well as self- consciousness and meta-consciousness (the awareness of being aware), but may not be involved in more fundamental sensory perceptual awareness. It appears that an area towards the rear of the brain’s cortex – the “posterior hot zone”, as Koch calls it – is crucial for this. One posterior region apparently important for consciousness is the parietal cortex, which processes sensory information from the body. In 2021, Mohsen Afrasiabi and Michelle Redinbaugh at the University of Wisconsin-Madison and others reported research on macaques that were sleeping, anaesthetised or awake. They concluded that connectivity between the parietal cortex, the striatum and the thalamus is a “hallmark” of conscious states. All in all, it remains a confusing picture – and with the clock ticking on his wager, Koch is anticipating defeat. “The extent to which more frontal regions of the cortex, let alone other brain regions, contribute to consciousness will remain open for many years to come,” he says. “After all, the brain is the most complex piece of active matter in the known universe.” ❚ STRIATUM PEDUNCULOPONTINE NUCLEUS GLOBUS PALLIDUS INTERNA THALAMUS Central station of sensory input Regulation of voluntary movement Many brain regions are implicated in aspects of our conscious experience, meaning the hunt for a single seat of consciousness has been so far fruitless FRONTAL LOBE PREFRONTAL CORTEX MOTOR CORTEX Complex behaviours, communication, memory, attention and personality BASAL GANGLIA Movement, reward and emotion Planning and control of voluntary movement Emotion regulation, intuition, insight, empathy Involved in diverse aspects of behaviour and movement Initiation of movement Language, attention and senses PARIETAL LOBE Memory and senses TEMPORAL LOBE OCCIPITAL LOBE Vision -- 13 of 100 -- 12 | New Scientist Essential Guide | Consciousness “WHY IS THERE SOMETHING IT’S LIKE TO BE US?” How does someone become a philosopher of consciousness? To me, the problem of consciousness is the most interesting unsolved problem in the universe – a central aspect of our existence that we almost entirely fail to understand. I actually started out as a mathematician and got part way through a doctorate in mathematics, but I gradually became obsessed by this question of why there is consciousness in the world. I thought, how am I going to study this from a big- picture perspective? Philosophy is the field that allows you to integrate science and technology, history and everything together, so I ended up switching to study philosophy, cognitive science and artificial intelligence, and eventually became a philosopher of consciousness. Concerning your bet with Christof Koch about finding neural correlates of consciousness: you’ve won, haven’t you? It’s looking pretty good for me. I’m quite open to the idea that eventually we’ll find some system or property INTERVIEW PROFILE DAVID CHALMERS The originator of the “hard problem” of consciousness, philosopher David Chalmers is co-director of the Center for Mind, Brain and Consciousness at New York University Although we have made some progress understanding how patterns of brain activity relate to conscious experiences, the basic question of why we have them remains unresolved, says David Chalmers -- 14 of 100 -- Chapter 1 | What is consciousness? | 13 in the brain that correlates with consciousness – which plays the role DNA plays for the gene, if you like. That wouldn’t fully explain consciousness, but it would be a huge step. But the bet was that some intrinsic property or small number of properties of neurons would be acknowledged as the neural correlate of consciousness by 2023. I was always very sceptical about that: I thought it was going to be a lot more complicated and take a lot more time. Meanwhile, the wider hard problem of consciousness seems as intractable as ever. Why is it so hard? The hard problem is the problem of explaining subjective experience. Why is there something it’s like to be us? When we see, when we hear, information strikes our sensory organs and gets processed by our brains, and that leads to behaviour. We can tell a nice mechanistic story about all of that, and how it might explain things like learning or language or memory. But why does this feel like something from the inside? Why is there subjective experience of hearing and seeing? Why doesn’t it go on in the dark without consciousness? That just looks like a different kind of question. Have we made any progress towards answering it? Although we haven’t nailed the neural correlates of consciousness, we’re on the way to understanding the correlations between brain activity and consciousness better. When it comes to the question of why there is consciousness at all, we’ve explored some theoretical options, many of which are very interesting and promising. But in my experience, the further you go down these paths, the more problems you find. I’ve not found anything that I’m actually satisfied with yet. Do you have any hunches about where a solution might lie? In general, I’ve argued for views that don’t try to reduce consciousness to, say, a brain process or something simpler, but take it as something fundamental in the way that space and time, or mass and charge, might be. I do take panpsychism especially seriously, the idea that some element of consciousness at the fundamental level of physical reality somehow adds up to and produces our consciousness. Also, the idea that maybe consciousness is distinct from any physical process that plays a role in the physical world. →- Chapter 6 has more on consciousness- and reality- Isn’t the basic problem that we don’t have a brain that can understand itself? What’s the old saying here? If the mind was so simple that we could understand it, we’d be too simple to understand the mind. Some people think it’s a miracle that we can understand nature at all, so maybe there are some things that we’re just too dumb to understand. I’d like to think that’s not the case. I don’t see any obstacle in principle to eventually having a scientific theory of consciousness. Science and philosophy is a process that takes centuries or millennia. Probably even in 100 years’ time, all this is going to look very different. ❚ JENNIE EDWARDS -- 15 of 100 -- 14 | New Scientist Essential Guide | Consciousness ACK in 2005, a team of neuroscientists led by Giulio Tononi at the University of Wisconsin-Madison and Marcello Massimini at the University of Milan injected a pulse of energy into the brain via transcranial magnetic stimulation, then used electroencephalography to monitor the response. They found that the electrical echo generated by the energy pulse will bounce all around a conscious brain, but stays very localised in an unconscious one. In other words, the conscious brain is much more connected. Such insights have come to be plugged into more sophisticated ideas that see consciousness arising not from the workings of specific cells or any single area of the brain, but from the properties of networks of neurons. Global workspace theory has perhaps been the most influential of these ideas. First floated in 1983 by Bernard Baars at The Neurosciences Institute in San Diego, California, it proposes that non-conscious experiences are processed locally within separate regions of the brain, such as the visual cortex. We only become conscious of this information if these signals are broadcast to an assembly of neurons distributed across many different regions of the brain – the CONSCIOUSNESS AND THE NETWORKED BRAIN As searches for the seat of consciousness have failed to turn up convincing answers, attention has shifted to the idea that consciousness depends on networked properties of neurons, and how they deal with information. That is the starting point of two leading models of consciousness: the global workspace, and integrated information theory. “global workspace” – which then reverberates in a flash of coordinated activity. The result is a mental interpretation of the world that has integrated all the senses into a single picture, while filtering out conflicting pieces of information (see diagram, right). A popular version of this concept is that special “workspace neurons” in the cortex, primarily in the front of the brain, broadcast information through their long-range connections. Global workspace theory seems to fit with a lot of findings about the brain. Critics ask, however, whether it explains subjective experience itself, or just indicates when information is available for reasoning, speech and bodily control. Other network-based ideas suggest that consciousness is the result of information being combined so that it is more than the sum of its parts. One that has grabbed much attention is integrated information theory (IIT), the brainchild of Tononi. It is based on the observation that each moment of our conscious awareness is unified. When you contemplate a bunch of flowers, say, it is impossible to be conscious of the flower’s colour independently of its fragrance because the brain has integrated the sensory data. Tononi argues that for a system to be conscious, it must integrate information in such a way that the whole contains more information than the sum of its parts. He proposed a measure of how a system integrates -- 16 of 100 -- Chapter 1 | What is consciousness? | 15 information – a proxy for the “amount” of consciousness in any system – that he called phi. Very approximately, phi will be high in a system of specialised modules that can interact rapidly and effectively. This is true for large parts of the brain’s cortex. In contrast, phi is low in the cerebellum, which is composed of modules that work largely independently of each other. In this way, IIT reflects some observations about the brain – for example, how a stroke or tumour may destroy the cerebellum without significantly affecting consciousness, whereas similar damage to the cortex usually disrupts subjective experience. Among IIT’s high-profile supporters are Christof Koch, who thinks it fits with his work pointing to activity in a highly connected “hot zone” of the posterior cortex with high phi being a neural correlate of consciousness. Among IIT’s problems, however, is that there are so many ways to divide up a system as complex as the human brain, or even constituent parts of it, that calculating phi is as good as impossible in any real situation. It suggests that something inanimate like a grid of electronic logic gates may have an extremely high degree of consciousness because it integrates information in the same way, and might even imply that the universe itself has some form of consciousness. →- Turn to page 88 for more on the- conscious universe- These are far from the only theories of consciousness out there. The “attention schema” model proposed by Michael Graziano at Princeton University, for example, is closely associated with the illusionist school of thought. It proposes that the brain evolved to contain a model of how it represents itself. This attention schema is like a self-reflecting mirror, and is what creates the subjective feeling of consciousness. There is no “ghost in the machine”; consciousness is just a mirage created by sophisticated neural processing. Anil Seth at the University of Sussex in the UK, meanwhile, proposes an idea called “predictive processing”: the brain is a prediction machine, meaning that what we perceive is the brain’s best guesses about the causes of its sensory input. As a result, much of conscious experience and selfhood is based on what we expect, not what is there. ❚ →- Michael Graziano and Anil Seth explain their ideas- in more depth on pages 30 and 93 respectively- The global workspace theory suggests that consciousness arises from highly coordinated, widespread activity in the brain CONSCIOUS When signals are broadcast to a wider network of neurons across much of the cortex – the global workspace – we become conscious of the sensation NON-CONSCIOUS When signals remain localised, the associated sensations are not perceived consciously PERCEPTIONS Sight, sound, taste and touch are first processed in small, localised areas of the brain GLOBAL WORKSPACE -- 17 of 100 -- 16 | New Scientist Essential Guide | Consciousness PERSPECTIVE CHRISTOF KOCH PROFILE CHRISTOF KOCH Christof Koch is chief scientific officer at the Allen Institute of Brain Science in Washington and author of books on consciousness including The Feeling of Life Itself “PHYSICS OVERWHELMINGLY FAVOURS CONSCIOUSNESS” Mathematical models of consciousness, such as integrated information theory, can lead us to a better understanding of what it is. QUICK glance at the thousands of books that purport to explain consciousness makes the real understanding of it look like a Herculean task. There is, after all, a profound explanatory gap between neural activity of any sort and subjective feelings. The first belongs to the realm of physics, to space and time, energy and mass; the second to experience. And while experiences are ephemeral, they are the very stuff of life. The only way we know about the world, about space and time, about energy and mass, about anything in fact is by seeing, hearing and smelling, by lusting and hating, by remembering and imagining. That these two realms are closely related is revealed by the effects of a stroke, a strong blow to the head or a neurosurgeon electrically stimulating some part of a person’s brain and evoking a childhood memory. Yet consciousness doesn’t appear in the equations of physics, nor in chemistry’s periodic table, nor in the A-T-G-C molecular chatter of our genes. Somehow, it emerges from the nervous system. I have spent more than three decades – the first 16 years working with my mentor, colleague and friend Francis Crick – linking specific aspects of consciousness to the mammalian brain. We popularised the idea of the neuronal correlates of consciousness (NCC): the minimal neuronal mechanisms – the synapses, neurons and brain regions – that are jointly sufficient for any one conscious percept. Since then, much progress has been made. We now -- 18 of 100 -- Chapter 1 | What is consciousness? | 17 know that some sectors of the cerebral cortex making up the bulk of the brain (for its size, the most complex organ in the universe) have a privileged relationship to consciousness, that not all of its many regions participate equally in generating the content of a conscious experience. Micro-electrodes and magnetic scanners have also shown us that the neocortex can be active without necessarily giving rise to a conscious experience. This is the domain of the non-conscious. Yet Crick and I looked deeper. Why did a particular NCC give rise to one specific conscious experience? Why should particular vibrations of highly organised matter trigger conscious feelings? It seems as magical as rubbing a lamp and having a genie emerge. What is needed is a fundamental account of how activity in any system can give rise to consciousness. We therefore turned to the ideas of Giulio Tononi at the University of Wisconsin-Madison. He advocates a sophisticated information theory account of consciousness, called integrated information. The idea introduces a precise measure, called phi, which captures the extent of consciousness. Expressed in bits, phi quantifies the extent to which any system of interacting parts is both differentiated and integrated when that system enters a particular state. This is the heart of phenomenal experience: any one conscious experience is both highly differentiated from any other one and also unitary, holistic. The larger the phi, the richer the conscious experience of that system. Integrated information makes specific predictions about which brain circuits are involved in consciousness and which ones are peripheral players, even though they might contain many more neurons. The theory should let doctors build a consciousness meter to measure the extent to which severely brain- injured patients are in a vegetative state, and which ones are partially conscious but unable to signal their pain and discomfort. At the Allen Institute for Brain Science in Seattle, Washington, we have been pursuing a different tack. Our goal is to understand how information is encoded, transformed and represented in the mouse and the human cerebral neocortex and its satellites. The neocortex is a layered structure: the human neocortex is about twice as thick that of the mouse, and has about 1000 times the surface area. It is a highly versatile, computational tissue that excels at processing sensory information, making and storing associations, and planning and producing complex motor patterns. The neocortex is partitioned into multiple areas, made up of smaller columns with reasonably similar cell types and architectures across species and brain regions. Our brain “observatories” aim to identify, record and intervene in the cortical networks underlying visually guided behaviours in the mouse, including visual perception, decision-making, and even murine consciousness. The fast-developing technology of optogenetics allows us to control defined events in defined neurons at defined times in mouse brains – that is, to move from correlation to causation. Building these observatories is a large-scale effort to synthesise anatomical, physiological and theoretical knowledge into a model of the cerebral cortex, which has the potential to revolutionise our understanding of the mammalian brain. Throughout my quest to understand consciousness, I never lost my sense of living in a magical universe. I do believe some deep and elemental organising principle created the universe and set it in motion for a purpose I cannot comprehend. I grew up calling this god. A pioneering generation of stars had to die in spectacular supernovae to seed space with the heavier elements needed for the rise of self-replicating bags of chemicals, on a rocky planet orbiting a young star at just the right distance. The competitive pressures of natural selection made possible the accession of creatures with nervous systems. As the complexity of these systems grew to staggering proportions, some of the creatures evolved the ability to reflect on themselves, to contemplate their beautiful but cruel world. While the rise of sentient life was inevitable, it doesn’t mean Earth had to bear life or that bipedal, big-brained primates had to walk the African grasslands. But I do believe the laws of physics overwhelmingly favoured the emergence of consciousness, and that those laws will lead us to a more or less complete knowledge of it. ❚ -- 19 of 100 -- 18 | New Scientist Essential Guide | Consciousness C H A P T E R 2 18 | New Scientist Essential Guide | Consciousness -- 20 of 100 -- Chapter 2 | Conscious minds | 19 We know – or we think we know – that we are conscious. But how about your pet dog or cat, or a tool-making crow, or a playful octopus or writhing worm? It might seem impossible to answer these questions. We have yet to identify any distinctive pattern of brain activity that indicates consciousness even in humans, and we can hardly ask other animals about their experiences. But posing these questions does provide another way to approach the phenomenon of consciousness. By asking what its outward signs are, and tracing back where they first appeared in the history of life, we might begin to understand why consciousness exists – and so learn a little about more what it is. Chapter 2 | Conscious minds | 19 -- 21 of 100 -- 20 | New Scientist Essential Guide | Consciousness ONSCIOUSNESS could have evolved for multiple reasons – or perhaps none. Some think that, rather than having a survival advantage, it is an “epiphenomenon”, simply emerging as an automatic property of intelligence. For most, however, that is a bit of a cop- out. “My guess is that consciousness, because of its complexity and costliness, in fact conferred adaptive value on its possessors,” says David Barash, a psychologist at the University of Washington in Seattle. Tracking the evolution of what we call consciousness has its own difficulties, however. “Consciousness doesn’t leave any fossil record,” says Anil Seth at the University of Sussex, UK. We must infer its evolutionary history by comparing animals alive today and working back to what their common ancestor might have been able to do. But because we don’t really know what we are looking for, we have to grope our way around the evolutionary tree, with only our own experience of consciousness as a guide. Some signs seem obvious. Chimpanzees recognise themselves in the mirror. Scrub jays will sneak back and re-cache food if another bird watched them hide it the first time – unless the watcher is their mate. Rats that push the wrong lever and fail to get a food reward gaze regretfully at the lever they should have pushed. In these cases, we can infer some sort of awareness of PABLO HURTADO DE MENDOZA PREVIOUS PAGE: LUMEZIA/ISTOCK > WHY DID CONSCIOUSNESS EVOLVE? Until recently, the question of what consciousness is for has been largely ignored. But now evolutionary biologists are starting to feel their way around the tree of life to consider when and where elements of our own consciousness emerged – and therefore why. -- 22 of 100 -- Chapter 2 | Conscious minds | 21 Chapter 2 | Conscious minds | 21 -- 23 of 100 -- 22 | New Scientist Essential Guide | Consciousness self, of others and of what might have been, which looks a lot like what we recognise in ourselves as consciousness (see “10 signs of consciousness”, page 25). If this were the sole criterion, however, there would be precious few non-human animals that cleared the bar, as not many show more than a few of the outward signs we might relate to our consciousness. →- Chapter 3 has more on the sense of self- There is reason to consider a broader benchmark: not every conscious experience is as complex as regret or self-awareness, even for us. “If you ask yourself, what are you conscious of… you see colours, you smell coffee, you feel your aches and pains,” says Jesse Prinz, a philosopher at the CUNY Graduate Center in New York. “Consciousness looks like it’s largely about perception and emotion: it’s not about thought or higher, more human capacities.” These basic components of conscious experience could be widespread, even in animals that lack our mental sophistication and brainpower. Consider emotion – or “hedonic valuation”, to use a less anthropocentric term. As Prinz points out, much of our conscious experience consists of perceptions with shades of feeling: objects are comforting or scary, sounds are pleasing or annoying, our body feels good or bad. Such evaluations play a crucial role in guiding our behaviour. “Behaviour is about moving toward what is beneficial or moving away from what isn’t. Feelings are meant to guide us by offering positive and negative rewards,” says evolutionary biologist Bjørn Grinde at the Norwegian Institute of Public Health in Oslo. That makes hedonic valuation a useful evolutionary tool. Grinde believes this sensation – the awareness that something good (or bad) is happening to you – may represent the dawn of consciousness. Surveying the vertebrate family tree, he sees a clear pattern: mammals, birds and reptiles all show signs of emotional responses, such as an increased heart rate and elevated body temperature when handled, while fish and amphibians don’t. The brains of higher vertebrates are also much richer in receptors for dopamine, the neurotransmitter most closely associated with reward pathways. He believes this is evidence that the ability to assign value to an experience arose around 300 million years ago in the common ancestor of modern reptiles, birds and mammals – the first fully terrestrial vertebrate. It makes sense. This ancestor would have faced challenges that its aquatic cousins didn’t, like temperature regulation and water conservation. Simple animals have reflex, or “unconscious”, responses, and even a worm can learn a fixed behaviour pattern by trial and error, but an individual with hedonic valuation is capable of much more flexible behaviour. In this new environment, such adaptability would have been a big advantage. Not that it doesn’t have disadvantages, too. Compared with unconscious processing of sensory data, it is slow and energy intensive, and can only do one thing at a time. What’s more, it can lead to behaviours that are capricious or even detrimental to the individual – for example, there would be no self-harm without conscious thought. Nevertheless, it seems to be useful enough that it might have evolved more than once. In 2020, Andreas Nieder at the University of Tübingen in Germany conducted an ingenious experiment to discover the brain processing underpinning visual consciousness in corvids such as crows. The birds were trained to respond to different coloured squares, some of them almost imperceptibly faint. Neurons in a region called the pallial endbrain lit up whenever the crows reported seeing the squares, but not when they failed to spot them, suggesting that this area is essential for their conscious visual perception. In humans and primates, a different part of the brain, the prefrontal cortex, performs the same job. For this reason, Nieder thinks that consciousness probably emerged separately on multiple occasions, in much the same way that wings appeared separately in insects, birds and bats. ←- Turn back to page 10 for more on locating- the seat of human consciousness- While many researchers agree that mammals, birds and reptiles have something special, many others believe consciousness is found elsewhere in the animal -- 24 of 100 -- Chapter 2 | Conscious minds | 23 kingdom too. They point out that the signs of emotion become harder to discern the further we get from ourselves. Would we recognise the expression of feelings in a fish, let alone a fruit fly? Instead, many researchers are converging on another indicator. Forget about sophisticated abilities like emotion, reason or imagination. An animal is conscious, they propose, if it experiences the world subjectively: if it has the distinctive “me, here, now” element of our own experience. Like hedonic valuation, subjective experience allows behavioural flexibility that goes beyond mere reflex responses. It sounds like a plausible basis for consciousness, but how can you measure an animal’s subjective experience? Bruno van Swinderen thinks he has found a way. A neuroscientist at the University of Queensland in Brisbane, Australia, he believes the essence of subjectivity is selective attention – focusing on just a few elements among all the sensory information available – because it indicates that an individual is taking control of its perception. “I’m not sure there’s really much difference between subjective experience and selective attention,” he says. To discover whether fruit flies are capable of selective attention, van Swinderen trained them to walk on a trackball suspended on a cushion of air, in front of a virtual scene projected onto a wrap-around wall of LEDs. By rotating the trackball, the flies could shift the scene and choose which of two objects to pay attention to. The images flickered at different rates, so that when a fly was paying attention to a particular object, it produced telltale frequencies in its neural activity, recorded by probes implanted in its brain. The results were remarkable. “It’s like a spotlight. There’s a dynamic window of attention that’s moving around, and other competing objects are being suppressed,” says van Swinderen. “The small fly brain really has a capacity for attention. That is, to me, the dawn of consciousness.” Measuring attention like this is very labour intensive, but there might be an easier way: so far, it seems like the animals that can pay attention are also the ones that need to sleep. These include vertebrates, insects, crustaceans and octopuses, but probably not more lumpen animals such as starfish, worms, and jellyfish. > Signs of consciousness have been found in animals from at least three different phyla, suggesting it evolved more than once and is far more common than most people think CNIDARIANS FLATWORMS ROTIFERS ANNELIDS ROUNDWORMS ECHINODERMS SPONGES MOLLUSCS ARTHROPODS CHORDATES -- 25 of 100 -- 24 | New Scientist Essential Guide | Consciousness →- Chapter 4 has more on sleep and dreaming- Intriguingly, van Swinderen has also found that insects and vertebrates respond almost identically to general anaesthetics. “The concentration to knock out a fly is pretty much the same as the concentration to knock out an elephant,” hinting that the two lose consciousness in a similar way, he says. By contrast, nematode worms, which are unlikely to have selective attention or anything approaching consciousness, require 10 times as much anaesthetic before they stop moving. →- Turn to page 62 for more on anaesthetics- The hunt for selective attention suggests that something like consciousness occurs in vertebrates, insects and octopuses at the very least. We know that the common ancestor of these three groups was a very simple organism that resembled a flatworm. Modern flatworms show few, if any, signs of rudimentary consciousness, so it seems a safe bet that the common ancestor also lacked consciousness. If so, that means consciousness evolved separately in the three groups. That reinforces Grinde’s idea about the function of consciousness. “When you step back and start to reflect on why these systems arise where they do, the story seems to make sense,” says Prinz. All three groups feature nimble, fast-moving animals that encountered rapidly changing conditions as they moved. That puts a premium on flexible decision-making. However, not everyone is convinced that being able to direct focus is a signifier of consciousness. Selective attention is about data handling, says Michael Graziano, a neuroscientist at Princeton University. To act on that data, an animal needs a mental model of that attention, for much the same reasons it needs a mental model of its body. “It’s fine for me to say ‘arm, go here’,” says Graziano. “But something in my brain needs to have a model of what an arm is, its possible motions, and so on.” Similarly, a model of attention would recognise that you are focusing on something and understand how quickly you can shift focus and so forth. According to Graziano’s “attention schema” idea, this model – not selective attention per se – is responsible for our conscious awareness of the world. He speculates that such a level of mental sophistication may only be found in vertebrates. ↓- Michael Graziano explains his ideas on- page 30 later in this chapter- Evolutionary biologist Eva Jablonka at Tel Aviv University, Israel, also thinks there is more to consciousness than selective attention. She believes we should be looking for “unlimited associative learning” as a marker for the origin of consciousness. This is the ability to knit multiple cues into a single perception that is more than the sum of its parts, and then use that compound cue to drive behaviour. This allows animals to respond flexibly to the challenges they face, rather than relying on hardwired behaviours. It means, for instance, that they can better discriminate between a healthy and a poisonous source of food based on small perceptual differences. It is also what allows us to learn that a growling dog may be playful in one context but threatening in another. “That marks the beginning of minimal consciousness,” says Jablonka. Unlimited associative learning requires an array of brain functions, not only selective attention, but also the ability to combine sensations into one perception, perform compound action patterns and distinguish between self and environment. Scientists have found evidence that this complex learning is surprisingly widespread throughout the animal kingdom. “Even little fish are able to do this,” says Jablonka. Already, researchers have documented it in almost every vertebrate (except, possibly, lampreys); some arthropods, such as insects and crustaceans; a few molluscs including octopuses; and, perhaps, some snails. The jury is out on other groups, such as worms, since we don’t have enough evidence to be sure. “There are huge gaps in our knowledge,” says Jablonka. -- 26 of 100 -- Chapter 2 | Conscious minds | 25 alive today, and Jablonka suggests that consciousness – driven by selection for powerful learning ability – might have helped drive that rapid evolution. Predators, for example, would have been better at detecting their prey, which, in turn, would have needed to find new ways to avoid detection – pushing the predators to become even more sophisticated in their strategies. “There is a kind of ongoing co-evolutionary arms race,” says Jablonka. “I can’t think of many things that could change adaptability that dramatically.” But the emergence of consciousness didn’t just allow animals to adopt more complex behaviours. Jablonka suggests that it is responsible for much of the beauty that we see in nature too. It led different species to evolve camouflage, for example. And it pushed plants to evolve colourful flowers that would stick out from the competition to attract pollinating insects. “It changed the world completely,” she says. “The world would have been a very different place, and a very much more boring place, without consciousness.” It is early days when it comes to considering consciousness in an evolutionary context. While researchers have yet to reach a consensus on when it arose and which animals possess it, they have already enriched our understanding of what consciousness is, and what is and isn’t distinctive about our own version of it. But the fact that the rudiments of consciousness are all around us has come as a surprise to many. “When I started, I was really sure we would find it in mammals. I was pretty convinced we wouldn’t find it elsewhere,” says Prinz. “I have been absolutely convinced that the contrary is true. The basic mechanisms can be found in creatures of an enormous variety.” Another lesson we can draw from this approach is that consciousness isn’t clear-cut. “I don’t think we’re ever going to find a single dividing line between those species that enjoy the glow of an inner universe and those that don’t,” says Seth. “There is not just one single way of being conscious. The animal kingdom is going to be suffused with other kinds of minds and other kinds of consciousness, and they’re not going to be just mini versions of human consciousness. We’re not the centre of the universe.” ❚ T E N S I G N S O F C O N S C I O U S N E S S Our assessment of the degree to which something is conscious is necessarily anthropocentric, as we can go only on our – highly imperfect – understanding of what consciousness is and what it relates to in ourselves. But some or all of these characteristics in other animals are often seen as indicating some degree of inner life. • Recognises itself in a mirror • Has insight into the minds of others • Displays regret at having made a bad decision • Heart races in stressful situations • Has many dopamine receptors in its brain to sense reward • Highly flexible in making decisions • Has ability to focus attention (selective experience) • Needs to sleep • Is sensitive to anaesthetics • Displays unlimited associative learning ↓- See the next section for more on- other animals’ consciousness- Nevertheless, what we already know has led Jabonka to suspect that consciousness evolved in early vertebrates and early arthropods during the Cambrian explosion, about 540 million years ago, when these groups diversified rapidly. Consciousness in octopuses, meanwhile, probably evolved about 250 million years later, after their lineage diverged from other, less intellectually gifted molluscs such as clams and snails. This origin is interesting. The Cambrian explosion saw the emergence of most of the major animal groups -- 27 of 100 -- 26 | New Scientist Essential Guide | Consciousness HILDREN know the fun of throwing a ball into the sea, only to watch the waves fling it back. Jennifer Mather, a comparative psychologist at the University of Lethbridge in Alberta, Canada, and Roland Anderson, a marine biologist at the Seattle Aquarium in Washington, were surprised to find octopuses playing similar games. Their toy was a floating pill bottle, which they were free to ignore or explore as they wished. Six of the aquarium’s octopuses soon lost interest, but two showed childlike curiosity, pushing it with their arms or shooting jets of water to move it against the tank’s current. It is hard to interpret this as anything other than play, which many researchers argue requires some form of conscious awareness. The challenge, of course, is to understand how the inner lives of these creatures differ from our own. In the past, scientists spoke about “levels of consciousness”, as if there were a hierarchy with humans on top. Philosopher Jonathan Birch at the London School of Economics has argued, however, that we would do better to consider five separate broad aspects of what we might call conscious experience (see “Five elements of consciousness”, page 28). According to Birch and his colleagues, it doesn’t make sense to ask whether one animal is more or less conscious than another, since each species may score highly on some of these facets of consciousness, but low on others. Research by Birch’s co-author Nicola Clayton at the University of Cambridge offers a good example. The propensity of scrub jays to bury food to eat later demonstrates high temporality because it involves planning for future scarcity and remembering the location of caches. Their use of deception when hiding food in the presence of a rival bird, meanwhile, shows theory of mind, which suggests a relatively sophisticated sense of selfhood, too. Cephalopods, by contrast, haven’t yet shown INSIDE ANIMAL MINDS Evidence of what seem to be conscious behaviours is rife, not just among warm-blooded mammals and birds, but in very different animals such as octopuses and even spiders. Getting inside these alien minds is extremely challenging indeed. PIOLA666/ISTOCK Octopuses seem to play, plan and learn by observation – all abilities we associate with conscious experience -- 28 of 100 -- Chapter 2 | Conscious minds | 27 evidence of self-recognition. But the octopuses’ enjoyment of play may be a sign that cephalopods can experience something akin to pleasure – evidence of some evaluative richness. They also have extraordinary perceptual richness, with complex vision that can detect polarised light and the ability to taste by touch via their suckers. And if you consider essential elements of consciousness to be a notion of self in space and an ability to make decisions based on information from previous experience and the current situation, then cephalopods pass with flying colours. Experiments in the 1980s, for example, involved offering octopuses a tasty hermit crab with a stinging anemone on its back. Unlike other predators, the octopuses didn’t back off after the first sting. Instead, they tried various strategies to get rid of the anemone: jetting water at it from their siphon, attacking from below and attempting to delicately extract the crab with one tentacle. Octopuses show similar cunning when they are presented with a clam. They will often try to get at the meat inside by drilling a hole with their beak, before injecting a poison to stop the clam’s heart or disable the muscles that clamp the shell shut. “There is some evidence that the location of the hole that is drilled is learned – it is no use putting it in most places,” says Mather. “I think that this has to be ‘decision-making’.” There are numerous other examples of the kinds of advanced abilities that might constitute conscious thought. Octopuses and cuttlefish can learn by observing each other, for example, something that suggests a notion of “self” and “other” and perhaps the ability to put themselves mentally in that position. Cuttlefish also seem able to send contradictory signals simultaneously: a male might show a courtship display to a female facing one side of his body and a “back off” display on the other to a challenging male, for instance. At other times, a male might try to deceive his love rivals by wearing a female-like pattern that leads the other males to believe he is no threat, as he edges closer to his mate. These look a lot like conscious decisions based on the information at hand. Some octopuses also use tools, and will, for example, hulk a heavy shell around all day in case it comes in handy for shelter later on. This suggests an ability to plan ahead, showing the kind of complex decision- making that defines consciousness. “Tool use and observational learning suggests to me that if you are able to look at another entity and know that it is ‘other’, then there’s likely to be a sense of self,” says Jennifer Basil, a cephalopod researcher at the City University of New York. However, she warns that when a creature is so different to us, it is difficult to have any idea of what they are thinking, or even if they are thinking at all. Perhaps the most startling difference between species concerns the unity of their conscious experience. Humans have two eyes, but we seamlessly integrate the two visual fields into a single conscious experience, thanks to the thick nerve tract connecting our left and right brain hemispheres. Birds lack that connective structure, leading Birch and his colleagues to speculate that within each individual, there may be “a pair of conscious subjects, intimately cooperating with each other”. In the octopus, meanwhile, two-thirds of its neurons are located in its arms, and there is some evidence that each limb operates semi-autonomously. “You could conceive of there being eight conscious experiences associated with the different arms, that are partially unified with the experience associated with the brain,” says Birch. That is a consciousness so alien that it is almost impossible for us to imagine – but it is perhaps not even the most surprising evidence of consciousness we have found. The way web-spinning spiders tailor their constructions to fit into restricted spaces or around obstacles suggests the abilities both to plan and to form a mental representation of space. That is particularly impressive when you consider that most spiders are almost completely blind. Other species of > -- 29 of 100 -- 28 | New Scientist Essential Guide | Consciousness hunting spider also seem to plan routes, and even seem capable of being surprised. Such findings, combined with new evidence of spider sociability, indicate advanced cognition across many spider species. Yet the brains of these creatures are often minute: most orb weaver spiders, for instance, weigh between 50 and 80 milligrams, with some less than 1 milligram, and their brains are just a fraction of that. Spiders’ ancient origins also raise some profound philosophical questions about the evolution of the brain. Previously, we have tended to look for intelligence in our closer relatives, but broadening the web to animals like spiders has proved profitable. “The success of this line of research shows that we should be careful not to restrict our research questions or study species,” says Caroline Strang at the University of Texas at Austin, who investigates insect cognition. It is exciting, too, because it means that spiders could provide valuable information about which neural structures are necessary for conscious experience, as well as how these evolved. In a vertebrate, the midbrain gathers sensory information and bodily signals, then integrates these to create a mental simulation of the world and the creature’s place in it. This, in turn, directs its attention and movement according to its needs, creating an “experiential consciousness” on which to build other types of awareness, such as self-reflection. “It basically underpins everything,” says Andrew Barron at Macquarie University, Australia. Invertebrate brains take a different form, but a structure called the central complex shows the same connectivity in insects, argues Barron. In spiders, a region known as the arcuate body may have the same purpose. Detailed studies of spider brains have been low on neuroscientists’ lists of priorities. However, if further evidence supports the idea that these regions create an inner representation of the world, this could help us pinpoint a date for the emergence of conscious experiences – potentially more than half a billion years ago, when the Cambrian explosion gave rise to almost all the animal groups around today. It means consciousness may be far more widespread than we thought. ❚ F I V E E L E M E N T S O F C O N S C I O U S N E S S To avoid searching for traits specific to humans in other animals, Jonathan Birch, a philosopher at the London School of Economics, and his colleagues suggest we should concentrate on five broad aspects of conscious experience that can be used to distinguish different animals’ degree of consciousness. P E R C E P T U A L R I C H N E S S How well an animal can discriminate different details in each of its senses. E V A L U A T I V E R I C H N E S S Broadly speaking, the capacity to differentiate between positive rewards and noxious stimuli, which could be analogous to human emotions such as pleasure or pain. U N I T Y The extent to which an animal integrates the information from its sensory organs into a single experience. T E M P O R A L I T Y Whether a creature’s past experience influences its present behaviour, and whether it can plan for the future and make decisions. S E L F H O O D This may be tested by assessing whether an animal recognises itself in the mirror, or has so-called theory of mind – the ability to understand that another animal has its own mind. -- 30 of 100 -- Chapter 2 | Conscious minds | 29 COULD A ROBOT EVER BE CONSCIOUS? Sentient machines are a science-fiction staple – but are they possible, and would we know if one were? The answers may depend on how you view consciousness. F THE subjective feeling of consciousness is an illusion created by brain processes, then machines that replicate such processes would be conscious in the way that we are. How would we know this? Daniel Dennett at Tufts University in Massachusetts says a Turing test, in which a machine has to convince a human interrogator that it is conscious, should, if conducted “with suitable vigour and aggression and cleverness”, be enough. Michael Graziano at Princeton University thinks we could take a more direct approach. His attention schema hypothesis sees consciousness as the brain’s simplified model of its own workings – a representation of how it represents things. He believes it is possible to build a machine that possesses a similar self-reflective model. “If we can build it in a way that we [can] see into its guts, then we will know this is a machine that has a rich self-description,” he says. “It is a machine that thinks and believes it has consciousness. And those are confirmable because you can understand, in principle, how the machine is processing information.” For Graziano, consciousness could appear in any machine, whether it is purely in software or constructed of matter, biological or otherwise. Anil Seth at the University of Sussex, UK, isn’t so sure. “I think it is still an unknown whether consciousness is substrate-independent,” he says. For him, determining whether a machine is conscious requires making informed judgements based on whether, for example, it has analogues of brain structures that we know are important for consciousness in humans, and what it is made of (brain organoids, for example, are made of biological material). Identifying consciousness in a machine may be more straightforward if you subscribe to the integrated information theory of consciousness. In principle, this simply entails ensuring that phi, a quantity indicating the degree of information integration within the system, is greater than zero. In practice, calculating phi is computationally intractable for anything but the simplest of systems. So, even if a machine were designed to integrate information, it would be far beyond our abilities to tell whether it is conscious. ←- Page 14 has more on the integrated- information model- Phil Maguire at the National University of Ireland, Maynooth, goes further. He notes that, by definition, integrated systems can’t be understood by looking at their parts. “Machines are made up of components that can be analysed independently,” he says. “They are disintegrated. Disintegrated systems can be understood without resorting to the interpretation of consciousness.” In other words, machines can’t be conscious. Selmer Bringsjord at Rensselaer Polytechnic Institute in Troy, New York, agrees – but for different reasons. He thinks our subjective feeling of being conscious is the outcome of non-material stuff of some sort, and that this is crucial for some of our intelligent behaviour. For him, machines can never possess this essence, so will never be conscious or intelligent in the way that we are. ❚ -- 31 of 100 -- 30 | New Scientist Essential Guide | Consciousness “CONSCIOUSNESS IS AN ENGINEERING PHENOMENON” One possible reason for the existence of subjective experience is that it emerges from the way our brain regulates itself. PERSPECTIVE MICHAEL GRAZIANO PROFILE MICHAEL GRAZIANO Michael Graziano is a neuroscientist and psychologist at Princeton University and the author of books including Rethinking Consciousness: A scientific theory of subjective experience NGINEERING, and the science of robotics in particular, tells us that every good control device needs a model – a quick sketch – of what it controls. We already know from cognitive neuroscience that the brain constructs many internal models, bundles of information that represent items in the real world. These models are simplified descriptions, useful but not entirely accurate. For example, the brain has a model of the body, called the body schema, to help control movement of the limbs. When someone loses an arm, the model of the arm can linger on in the brain so that people report feeling a ghostly, phantom limb. But the truth is, all of us have phantom limbs, because we all have internal models of our real limbs that merely become more obvious if the real limb is gone. By the same engineering logic, the brain needs to model many aspects of itself to be able to monitor and control itself. It needs a kind of phantom brain. One part of this self-model may be particularly important for consciousness. Here’s why. Too much information flows through the brain at any moment for it all to be processed in equal depth. To handle that problem, the system evolved a way to focus its resources and shift that focus strategically from object to object: from a nearby object to a distant sound, or to an internal event such as an emotion or memory. Attention is the main way the brain seizes on information and processes it deeply. To control its roving attention, the brain needs a model, which I call the attention schema. -- 32 of 100 -- Chapter 2 | Conscious minds | 31 The attention schema theory explains why people think there is a hard problem of consciousness at all. Efficiency requires the quickest and dirtiest model possible, so the attention schema leaves aside all the little details of signals and neurons and synapses. Instead, the brain describes a simplified version of itself, then reports this as a ghostly, non-physical essence, a magical ability to mentally possess items. Introspection – or cognition accessing internal information – can never return any other answer. It is like a machine stuck in a logic loop. The attention schema is like a self-reflecting mirror: it is the brain’s representation of how the brain represents things, and is a specific example of higher-order thought. In this account, consciousness isn’t so much an illusion as a self-caricature. A major advantage of this idea is that it gives a simple reason, straight from control engineering, for why the trait of consciousness would evolve in the first place. Without the ability to monitor and regulate your attention, you would be unable to control your actions in the world. That makes the attention schema essential for survival. Consciousness, in this view, isn’t just smoke and mirrors, but a crucial piece of the engine. It probably co-evolved with the ability to focus attention, just as the arm schema co-evolved with the arm. In which case, it would have originated as early as half a billion years ago. Sometimes, the best way to understand a thing is to try to build it. According to this new idea, we should be able to engineer human-like consciousness into a machine. It would require just four ingredients: artificial attention, a model of that attention, the right range of content (information about things like senses and emotions) and a sophisticated search engine to access the internal models and talk about them. The first component, attention, is one of the most basic processes in most nervous systems. It is nicely described by the global workspace theory. If you look at an object, such as an apple, the brain signals related to the apple may grow in strength and consistency. With sufficient attentional enhancement, these signals can reach a threshold where they achieve “ignition” and enter the global workspace. The visual information about the apple becomes available for systems around the brain, such as speech systems that allow you to talk about the apple, motor systems that allow you to reach for it, cognitive systems that allow you to make high- level decisions about it and memory systems that allow you to store that moment for possible later use. ←- Turn back to page 14 for an explanation- of global workspace theory- Scientists have already built artificial versions of attention, including at least a simple version of the global workspace. But these machines show no indication of consciousness. The second component that our conscious machine requires is an attention schema, the crucial internal model that describes attention in a general way, and in so doing informs the machine about consciousness. It depicts attention as an invisible property, a mind that can experience or take possession of items, > -- 33 of 100 -- 32 | New Scientist Essential Guide | Consciousness something that in itself has no physical substance but still lurks privately inside an agent. Build that kind of attention schema, and you will have a machine that claims to be conscious in the same ways that people do. The third component our machine needs is the vast stream of material that we associate with consciousness. Ironically, the hard problem – getting the machine to be conscious at all – may be the easy part, and giving the machine the range of material of which to be conscious may be the hard part. Efforts to build conscious content might begin with sensory input, especially vision, because so much is known about how sensory systems work in the brain and how they interact with attention. But a rich sensory consciousness on its own won’t be enough. Our machine should also be able to incorporate internal items, such as abstract thought and emotion. Here, the engineering problem becomes really tricky. Little is known about the information content in the brain that lies behind abstract thought and emotion, or how they intersect with the mechanisms of attention. Sorting out how to build a machine with that content could take decades. The final component that our conscious machine requires is a talking search engine. Strictly speaking, talking isn’t necessary for consciousness, but for most people the goal of artificial consciousness is a machine that has a human-like ability to speak and understand. We want to have a good conversation with it. The problem is deceptively hard. We already have digital assistants like Siri and Alexa, but these are limited in their functions. You give them words, they search for words on the internet and they then give you back more words. If you ask for the nearest restaurant, the digital assistant doesn’t know what a restaurant is, other than as a statistical clustering of words. In contrast, the human brain can translate speech into non-verbal information and back again. If someone asks you how the taste of a lemon compares with that of an orange, you can translate the speech into taste information and compare the two remembered tastes, then translate back into words to give your answer. This easy back-and-forth conversion between speech and many other information domains is challenging to do artificially. Our conscious machine would need to correlate information across every imaginable domain, a problem that hasn’t yet been solved in artificial intelligence. Given all the promise and all the difficulties, just how close are we to conscious machines? If the attention schema approach is correct, the first attempts at visual consciousness could be built with existing technology. But it will take a lot longer to give machines a human-like stream of consciousness. It will take time to build a conscious machine that is capable of seeing, hearing, tasting, touching, thinking abstract thoughts and feeling emotions, with a single integrated focus of attention to coordinate within and between all those domains, and that is able to talk about this full range of content. But I believe it will happen. To me, though, the purpose of this thought experiment isn’t to advocate for conscious robots. The point is that consciousness itself can be understood. It isn’t an ethereal essence or an inexplicable mystery. The attention schema idea puts it in context and gives it a concrete role in adaptation and survival. Instead of an ill-defined epiphenomenon, a fog extruded by the brain and floating between the ears, consciousness becomes a crucial component of the cognitive machine. ❚ PERSPECTIVE MICHAEL GRAZIANO -- 34 of 100 -- NEW SCIENTIST ESSENTIAL GUIDES DELIVERED DIRECT TO YOUR DOOR ESSENTIAL GUIDES &EWIHSRXLIFIWXGSZIVEKIJVSQ 2I[7GMIRXMWXXLI )WWIRXMEP+YMHIWEVI GSQTVILIRWMZIRIIHXSORS[GSQTIRHMYQWGSZIVMRKXLIQSWXI\GMXMRK XLIQIWMRWGMIRGIERHXIGLRSPSK]XSHE] +IXXLIWIVMIWMRGPYHMRKXLIVIGIRXP]TYFPMWLIHMWWYISR0MJISR)EVXL [MXLER)WWIRXMEP+YMHIWWYFWGVMTXMSR-XQIERW]SYHSR XLEZIXSWIEVGLJSV MWWYIWMRXLIWLSTWr[IGERHIPMZIVXLIQHMVIGXXS]SYVHSSV FOR MORE INFORMATION ON FUTURE ISSUES AND SUBSCRIPTION OFFERS, VISIT: NEWSCIENTIST.COM/ESSENTIALGUIDE -- 35 of 100 -- 34 | New Scientist Essential Guide | Consciousness C H A P T E R 3 34 | New Scientist Essential Guide | Consciousness -- 36 of 100 -- Chapter 3 | Your conscious self | 35 A sense of existence is essential to consciousness as we experience it. There is something it is like to be us, and perhaps to be a scrub jay, or an octopus, or a newborn child. Presumably, there is nothing it is like to be a table or an iPhone. Self-awareness and its related trait of metacognition, the ability to monitor your own mental states and those of others, are often regarded as the pinnacles of consciousness. In fact, they might be evolutionary accidents, and perhaps even figments of our own imaginations. Chapter 3 | Your conscious self | 35 -- 37 of 100 -- 36 | New Scientist Essential Guide | Consciousness ANY psychologists and anthropologists hold to the idea that there is a hierarchy of consciousness that corresponds with increasing brain complexity. At its base is the minimal consciousness attributed to animals with simple nervous systems. These minds are thought to be permanently adrift in a sea of raw sensory experiences, tossed around between perceptions such as colour, hunger, warmth and fear, with little awareness of their meaning. ←- Turn back to chapter 2 for- more on animal minds- Few minds are sophisticated enough to experience the world differently – through an introspective lens. Even then, they may have a limited sense of self. Only at the peak of mental complexity do we find minds able to construct a lifelong narrative of experiences centred around an abstract concept of “self”. These are the elite. There is no question that some brains are much bigger and more structurally complicated than others. This disparity is mainly the result of the differing evolutionary demands that animals must meet to survive. For example, the nervous system of a sedentary, filter-feeding oyster consists of just two cell clusters. These allow it to do exactly what an oyster needs to do – control its digestion and transmit signals from light- sensing tentacles to the muscle that snaps it shut when a predator looms. Meanwhile, at the other end of the spectrum, there is one particular demand that seems to have led to the evolution of complex brains. It could also have created the conditions for a sense of self to arise. That challenge is dealing with the minds of others – be they prey, competitors or other members of your social group. According to the social brain hypothesis, developed by Robin Dunbar at the University of Oxford, life in tight-knit communities hinges on being able to understand what is going on PABLO HURTADO DE MENDOZA PREVIOUS PAGE: LUMEZIA/ISTOCK > THE EVOLUTION OF THE SELF Look into a mirror and you may see pimples, wrinkles or unruly facial hair, but beneath the superficial lies something far more interesting. Every time you lock eyes with your reflection, you know exactly who is looking back at you. -- 38 of 100 -- Chapter 3 | Your conscious self | 37 Chapter 3 | Your conscious self | 37 -- 39 of 100 -- 38 | New Scientist Essential Guide | Consciousness in another individual’s mind. That could be the basis of our distinctive human consciousness. In the 1970s, the idea emerged that it was the need to understand other people’s minds that made us aware of our own. “It is more difficult to anticipate the perceptions of others if you cannot perceive your own,” says David Barash, a psychologist at the University of Washington in Seattle. That might suggest human consciousness scaled greater heights as our ape-like ancestors started living in larger social groups, with the ensuing daily potential for aggression and competition. This isn’t the only hypothesis that relates the evolution of “higher” consciousness to group living. But for neuroscientist Chris Frith at University College London, the benefits concern cooperation rather than competition. “It’s so that we can talk to each other about experiences,” he says. Frith’s group has shown that people make better decisions in laboratory tasks if they are allowed to mull over the pros and cons of the evidence with a partner. That might sound obvious, but it is hard to imagine a zombie with no inner life whatsoever being able to do so, as it requires reflection and introspection – key traits we associate with consciousness. “We have to be able to reflect upon our experiences before we can talk about them,” says Frith. Frith’s colleague Geraint Rees gives the example of two early humans regarding a distant dust cloud and trying to work out if it signals a herd of buffalo or a pack of lions. The better they are at reflecting on their feelings and judgements, the better their collective decision- making about whether to hunt or flee. “If you can combine the forces of your sensory systems, that becomes a useful advantage,” says Rees. Yet Frith thinks a better example of the benefits of consciousness would be the early humans discussing the characteristic flavour of buffalo meat – and thereby deducing where the herd had been grazing. The key point is that, to achieve an understanding of the minds of others, brains needed to evolve from being simply things that experience sensations and thoughts to becoming their observer. Not everyone thinks we should put a sense of self on a pedestal, however. “Self-awareness is not higher-order, or intrinsically more complicated, than consciousness,” says neuroscientist Michael Graziano at Princeton University. “It is another example of consciousness.” In his view, a mind is just an object that some brains can model, and so become aware of. And once the biological machinery for such model- building evolved, it could be used to represent not only the minds of others, but also one’s own mind. Most researchers agree that the brain operates at least partly by generating simulations. However, some disagree that self-awareness is a functional piece of the modelling machinery. Indeed, some think it is the unintended, “emergent” by-product of information rushing through the closed loop of connections that is the brain. It serves no particular purpose, rather like the noise emitted by a running engine has no bearing on the workings of the engine itself. Rather, the tone of this noise reflects the predominant connections in our brains. There will be a huge diversity of emergent mental patterns that serve the various survival needs of different species. In bats, for example, it might be those transmitting information from the echolocation clicks used to construct a 3D model of the world. In humans, it simply seems to be the case that the predominant connections in our brains seem to be those used to contemplate the minds of others – the same connections used to contemplate ourselves. What emerges from this is a pattern that seems constant. To you, that is your sense of self. ❚ Like humans, mice, ravens and chimps have general intelligence, indicating that even animals with small brains can think flexibly MOUSE 0.4g 71 million neurons RAVEN 10.2g 1.2 billion neurons CHIMP 380g 28 billion neurons HUMAN 1350g 86 billion neurons -- 40 of 100 -- Chapter 3 | Your conscious self | 39 IN THE most widely used test of self-awareness, the so-called face-mark test, researchers stealthily apply a spot of odourless dye to an animal’s forehead or cheek and observe its reaction when it is in front of a mirror. The underlying premise is that those with a firm sense of self can acknowledge their reflection and attempt to scrub off the dye. Animals that have passed this test include chimps, bonobos, orangutans, Asian elephants and Eurasian magpies, a member of the notoriously clever corvid family. Killer whales and bottlenose dolphins also seem to recognise themselves in a mirror, although their anatomy means they can’t remove a face mark. This apparent correlation with smarts is why self-awareness has become a sort of proxy for mental complexity. But there are some puzzling evolutionary gaps. Gorillas, for instance, usually fail the test, yet our more distant primate relatives, the orangutans, pass it. Also, the self-aware elite contains some bizarre anomalies, such as pigeons, manta rays and ants. Some of these findings – particularly with ants and pigeons – are contested. Researchers have tried to explain away others, arguing, for example, that gorillas have mentally regressed since their split from the other ape lineages because they face fewer pressures in their environment. Then again, we have reason to believe mirror tests are flawed. Rhesus macaques generally fail them, but experiments in 2017 by Liangtang Chang at the Shanghai Institutes for Biological Sciences, China, and colleagues seem to suggest this is simply because they lack the hand-eye coordination to rub the dye off. When trained how to do it, they began to pass the test with flying colours. That hints that there could be many other species with undetected self-awareness. Meanwhile, some developmental psychologists working with young children have long argued that mirror tests don’t necessarily reveal an awareness of self that extends beyond the here and now. Experiments show that children can acknowledge themselves in a mirror at the age of 3, yet cannot recognise themselves in videos taken a few months earlier, and will struggle with the idea of existing in the past for another year or two. And the fact that the majority of animals that pass the self- awareness test are either our primate relatives or animals with complex social lives, like us, could mean that rather than reflecting mental complexity, the trait simply indicates that their minds have evolved to face similar challenges to our own. W H A T A N I M A L S A R E S E L F - A W A R E ? RUGLIG/ISTOCK Magpies and other corvids recognise themselves in the mirror – whatever that means -- 41 of 100 -- 40 | New Scientist Essential Guide | Consciousness E KNOW that we change over time. Our bodies grow, then age; we mature and our views shift; our memories sharpen and fade. Yet for most of us, our sense of self is seamless and continuous. You remain the same old you, right? That just raises the question of how. One interesting perspective on the question is that, while the cells in many organs in our body live for only days or weeks before being replaced, the neurons in our brain are with us from before birth, and can live more than 100 years. “Most of the nerve cells in the brain are actually as old as we are,” says molecular biologist Jonas Frisén at the Karolinska Institute in Sweden. And it is definitely our brains where we think our sense of self resides, at least. When Christina Starmans at the University of Toronto in Canada and her colleagues showed people from the US and India pictures of flies circling around a person, and asked which flies they thought were closest, the results were striking: regardless of cultural background, most people pointed to flies near a person’s eyes. “This suggests there is a universal sense of the self being located in the head, near the eyes,” says Starmans. Subjectively at least, the eyes being windows to the self checks out. “The sense of where in our bodies we are located is informed by our dominant experience IS THE SELF AN ILLUSION? We have a strong sense of continuous, coherent existence, yet from the cells that make our bodies to our defining character traits, we are in a constant state of change. That suggests a rather different answer. -- 42 of 100 -- Chapter 3 | Your conscious self | 41 of the world,” says Starmans. “Almost all of our input from the world comes in through our head.” And it squares with some objective evidence too. In some extremely rare brain conditions, people have a sense of existing outside their bodies: those experiencing heautoscopy, for instance, see a doppelgänger, and feel they are located both in their own body and the doppelganger’s. “They are in two places at one time. It’s very disturbing,” says Jane Aspell, a cognitive neuroscientist at Anglia Ruskin University in the UK. Similar illusions can be generated in the lab. For example, volunteers who have their back stroked while wearing a virtual reality headset showing a simulation of themselves being stroked start to feel that they are closer to their virtual self than to their actual body. Brain scans show that a region called the temporoparietal junction is affected. “This area is key for the brain computation that creates the perception of where your self is located in space,” says Aspell. So it is tempting to think the continuity of our sense of self has something to do with the physical continuity of our brains. And yet even our long-lived neurons are constantly in flux, rewiring themselves to generate new thoughts, memories and states of mind. The fact is that what we learn, what we eat, how well we have slept and countless other things influence our choices and behaviours all the time. So, in many ways, “you are not the same person from one moment to the next”, says Helge Gillmeister at the University of Essex, UK. The illusory nature of the continuous self was backed up in 2016 when researchers at the University of Edinburgh, UK, investigated changes in the behavioural habits that make up our personalities across a span of 63 years. Previous studies, looking over shorter periods, found only small changes, suggesting that we largely stay the same. But the longer view was startling: measured over six decades, barely anything about our personalities stays the same. We turn into different people over time. Sometimes, people go through major changes all at once – “something big happens that turns their lives upside down and very thoroughly shakes them up”, says psychologist Wendy Johnson, a co-author of that paper. Yet for the most part, our personalities drift through “dribbles of change, conscious and not, in specific behaviours over long periods of time”, she says. We are strangely skilled at shifting our notions of who we were or what we believed to maintain an illusion of a continuous self. For example, we scramble to rewrite history to get our previous attitudes to more closely match our current ones, dismissing the idea that we once held strong political views, say, with which we now disagree. “You make yourself up in the past,” says Gillmeister. At some level, we are also aware of the disconnect. Studies have demonstrated that we think about our future selves in a very different way to how we think of ourselves in the moment – in our brains, it is as if future you is a completely different person. ❚ Ask most of us where our sense of self is located and we point to somewhere near the eyes SKYNESHER/ISTOCK -- 43 of 100 -- 42 | New Scientist Essential Guide | Consciousness OUR pet dog, if you have one, is probably aware of many sensations at any given moment: that it is hungry, that it is tired after a long walk, perhaps, and that there is a delicious smell emanating from the kitchen. As its owner, however, you are aware of all those sensations and yet have an extra level of thought processes overlaying them. As a human, we can be aware that we are aware of our basic sensory inputs, and that allows us to reflect on the accuracy or validity of our feelings and judgements. That lets us think: “How tired I am after that long walk, it’s that satisfying kind of tiredness you get after exercise. But I’m not too tired to walk to the pub tonight.” This faculty is often referred to as introspection or metacognition. “It’s the ability to self-reflect, to know about yourself,” says Steve Fleming, who studies consciousness at University College London. “This is something that we think is, if not unique to humans, at least one of the most developed faculties of human psychology.” Fleming dubs this capacity our super- consciousness. “Metacognition seems to be quite core to who we are,” he says. Past research on metacognition has focused on whether it really is unique to humans or whether it is shared to some extent by more intelligent animals. There have been hints of this capacity in dolphins and monkeys, for instance, although sceptics say METACOGNITION: KNOWING THAT YOU KNOW While debate rages as to which animals have a sense of self, there is one trait that, as far as we know, is uniquely human – the ability to think about what we are thinking and know what we know. there could be other explanations for the results. Scanning the brains of humans while they carry out metacognitive tasks suggests the seat of this ability lies in our prefrontal cortex, at the front of our heads. But this faculty has been hard to get the measure of. If we ask people how sure they are about their answers in a test, say, the results are muddled by the variation in people’s ability to do the test. So are you measuring ability or awareness of that ability? ←- Turn back to page 10 for more on where- the seat of consciousness lies in the brain- Back in 2010, Fleming, then based at New York University, and his colleagues came up with a crucial extra step. They flashed two stripy images briefly onto a screen, separated by a blank image, and asked people to say which had the greatest contrast (see picture, top right). After each question, subjects had to rate how confident they were that they had chosen the right answer. Crucially, the contrast of the stripes was adjusted for each person so that, no matter how good their vision, everyone got about 70 per cent of the answers right. This meant that for the confidence ratings, the only variable was people’s metacognitive abilities, giving the first demonstration in the lab that this ability varies widely. As well as doing these tests, the volunteers also had their brain scanned, and this revealed that those with the best metacognitive abilities had more grey matter -- 44 of 100 -- Chapter 3 | Your conscious self | 43 in an area at the very front of the prefrontal cortex just behind the forehead, known as the anterior prefrontal cortex. “What is it about this region that gives us this ability?” asks Fleming. “Could the fact that it is more developed in humans mean that we have a fundamentally different self-awareness to animals?” The other classic way of understanding how the brain works is to look what happens when it isn’t functioning as it should. Take “blindsight”, a very rare condition usually caused by brain injury. Those affected act as though they are, to all intents and purposes, sightless. But careful testing reveals they can take in some visual information about the world at an unconscious level. When asked to guess what object is in front of them, for instance, they do better than if they had just guessed randomly – insisting all the while that they can see nothing. Blindsight has always been thought to arise from damage to the visual cortex, at the back of the brain, where information from the optic nerves first arrives. But some brain imaging studies, however, suggest that the damage also affects connections to the prefrontal cortex, the same region highlighted by Fleming. Less extreme impairments of metacognition may be involved in other more common conditions, such as schizophrenia, which involves delusions and hallucinations. “Schizophrenics have a problem with that very central metacognition; that I know I’m me and I know what I’m doing,” says Janet Metcalfe, also at Columbia University. →- Chapter 5 has more on altered states of the brain- She has studied the metacognitive abilities of people with schizophrenia using a simple cursor-based computer game. At first, the participants were as good at judging how well they performed as the group of control subjects. But when Metcalfe started secretly moving the cursor herself, the control group quickly recognised something strange was going on. People in the schizophrenia group, on the other hand, failed to realise that they were no longer completely responsible for the cursor’s movements. Some people with schizophrenia come to believe that others are controlling their behaviour, thinking, for instance, that a microchip has been implanted inside their head. “If you don’t know you’re controlling your own behaviour, you could be open to that kind of symptom,” says Metcalfe. It may be possible to improve people’s metacognitive abilities by giving them feedback after the kind of computer tasks used by Fleming. Metcalfe hopes this will help people with schizophrenia. But suppose the rest of us did the same kind of training. Would that give us a turbocharged super-consciousness? “If you define consciousness as what it’s like to see the colour red, then it’s not going to change that,” says Fleming. “But if it’s being able to accurately reflect on what you see, or whether you just made a good decision, then training could give it a boost.” ❚ Metacognition can be tested by getting people to rate which of two images is sharper, and then asking them how confident they are – but manipulating the images so they can only be right a certain proportion of the time -- 45 of 100 -- 44 | New Scientist Essential Guide | Consciousness YOUR CONSCIOUS BODY Increasingly, we are realising that conscious experience isn’t just about the brain. Electrical signals coming from your heart and other organs influence how you perceive the world, the decisions you take and your sense of who you are, providing a window on consciousness itself. T HAS long been known that our internal organs have lives of their own. They generate electrical activity, which is conveyed by neurons to the brain. As a result, signals from your heartbeat, your breathing, the slow, regular pulses of your stomach and the state of your muscles are all represented in the brain’s electrical activity. The brain, in turn, regulates these functions. In other words, there is a neuronal loop in which nerve cells carry information from the organs up to the brain, and commands down to the organs. However, in the 20th century, neuroscientists tended to ignore the body. They associated mental life exclusively with the brain – an approach epitomised by the “brain in a vat” thought experiment, in which a disembodied brain continues to have normal conscious experiences. Things began to change at the turn of this century, when neuroscientist Antonio Damasio at the University of Southern California pioneered the field of embodied consciousness. “I have been defending the idea that the body is a critical player in anything that has to do with mind,” he says. For years, he was more or less alone in this view, but now a handful of researchers have joined him in his quest for the bodily origins of our sense of self. Their starting point is interoception, a sort of sixth sense that we have about what is going on in our own body. A simple way to measure interoception is to get someone to count their heartbeats over a fixed time and compare their count with the actual one measured by an electrocardiogram (ECG). People’s ability to do this varies a lot. Those who can sense their heartbeat most accurately tend to make better intuitive decisions and are better at perceiving the emotions of others. What is going on? To tease it out, the researchers needed a read-out of interoception in the brain. They found one in the brain’s response to the heartbeat, known as the heartbeat-evoked potential (HEP). Many studies focus on this because the HEP is relatively easy to measure: the heartbeat isn’t completely regular, so -- 46 of 100 -- Chapter 3 | Your conscious self | 45 it is possible to filter the HEP out from all the brain’s other activity. The HEP can be found by simultaneously recording a person’s heartbeat, via an ECG, and scanning their brain. It shows up as activity in various “resting-state networks” in the brain, which are active even when a person isn’t consciously doing anything. One clue as to what the HEP might be doing came in 2016 when neuroscientist Hyeongdong Park at the Swiss Federal Institute of Technology in Lausanne (EPFL) and his colleagues measured it in people who were experiencing a full-body illusion. Volunteers donned a virtual reality headset and watched a simulation of themselves having their back stroked as it was being stroked in reality. After a while, they described feeling as if they were now physically located closer to where their virtual self was, rather than where they were actually sitting. The more pronounced their HEP, the stronger the illusion. Here was the first neurophysiological evidence of a link between interoception and the brain’s notion of self, claimed the researchers. “The HEP reflects changes in bodily self-consciousness such as changes in self-identification with – and displacement towards – the virtual body,” says Olaf Blanke, who heads EPFL’s Laboratory of Cognitive Neuroscience. The EPFL group has gone on to show that our bodily self is anything but passive – it intervenes in every decision we make. Blanke’s team has built on work by physiologist Benjamin Libet, who in 1983 detected a signal that arose in the brain just before a person became aware of their intention to act. Libet interpreted it as meaning that there is no such thing as free will. The EPFL group has found that the same signal is linked with a particular bodily act, breathing: we are more likely to initiate a voluntary act when exhaling. Blanke describes the finding as a clear indication that “acts of free will are hostage to a host of inner body states”. ↓- The next section has more on free will- Such experiments have led Park and Blanke to propose that signals from the organs, together with signals from the outside world, feed a representation of the bodily self to the brain. This includes self-identification and self-location, as in the full-body illusion. They also believe that the rhythmic nature of signals from the organs helps generate a feeling of your self being continuous in time. “The cyclic pattern of the heartbeat is predictable,” says Blanke, “and this temporal element could play a big role in that continuity of self.” Catherine Tallon-Baudry, a neuroscientist at the Ecole Normale Supérieure in Paris, France, has a different conception of how the body contributes to self-consciousness. The brain is constantly bombarded by signals from inside and outside the body and as a result of its own cognitive processes. The signals are processed by different brain circuits. She thinks that How accurately someone can count their own heartbeat is a test of interoceptive ability > VOYAGERIX/ISTOCK -- 47 of 100 -- 46 | New Scientist Essential Guide | Consciousness rhythmic signals from the organs impose a unified frame of reference on the brain. This allows us to perceive all that incoming information from the perspective of a single, subjective “I”. “I think of consciousness as a property that is generated by the brain once it has integrated information from the whole organism,” she says. And a series of experiments supports her contention, she believes. In 2014, Tallon-Baudry and Park, who worked in her lab before he moved to Blanke’s, began by exploring how the HEP might influence our conscious experience of things. They asked people to fix their gaze on a central point and to say whether they could see a faint ring around that point. The bigger a person’s HEP just before showing them the ring, the more likely they were to perceive it. “The heartbeat behaves like an extra piece of visual information,” says Tallon-Baudry. It also provides the intrinsic “mineness” of the conscious experience. “In the person’s response – ‘I saw something’ – there is that element of ‘I’,” she says. “We shouldn’t ignore that element of ‘I’ in perception.” Blanke sees this study as a beautiful demonstration of the threshold of consciousness, but says there is no need to conclude that the self is involved. To address this issue, Tallon-Baudry and her group devised another study. This time, they homed in on the distinction between “I” and “me”. Tallon-Baudry says “I” captures the most basic aspect of self – the aspect that comes before thought, the unified entity that does the thinking. It is fundamentally different from the kind of reflection about “me” that implies monitoring different bodily functions without that sense of unity. To see if they could show that the brain treats those two concepts differently too, Tallon-Baudry’s team asked people who were having their brain scanned to fixate on a point and then let their mind wander. Every now and then, they were interrupted and asked whether – at that precise moment – they were thinking about “me” or “I”, which they had been trained to recognise. Depending on which they reported, the HEP occurred in different parts of the brain: a region near the front for “me” thoughts and one further back for “I” thoughts. This showed for the first time that the brain does indeed discern between the two concepts. Tallon-Baudry’s group has also shown how the body might contribute to our decisions on our personal preferences, which in many ways define us in the eyes of others. Volunteers saw 200 posters of well-known films and were asked to rate the ones they had seen. Next day, they were shown pairs of posters from the films they had rated, and had to indicate which they preferred as they had their HEP tracked. As is usual with these sorts of experiments, people’s responses weren’t wholly consistent. However, people with the biggest HEP at the moment of choice gave answers that were most in line with their original ratings. Their choices were truest to themselves when their brains were listening most closely to their hearts. Blanke’s notion of a bodily self and Tallon-Baudry’s notion of bodily consciousness may not be too far apart. Indeed, they can imagine hitting on an overarching model of the embodied self that reconciles their findings. Sarah Garfinkel at the University of Sussex in the Virtual reality headsets can be used to create an illusion of being outside your self MAX-KEGFIRE/ISTOCK -- 48 of 100 -- Chapter 3 | Your conscious self | 47 UK, meanwhile, has been approaching things from a different angle. She has been exploring two connected ideas: that bodily signals influence emotions and that emotions shape our sense of self through memory and learning. Working with autistic people, she has concluded that the issues they often encounter relating to others stem from their brains being overwhelmed with the visceral inputs associated with their own and others’ emotions. Building on the idea of an overactive body-brain axis, Garfinkel’s research has now turned to a sensation most of us feel to great or lesser degrees at stages in our lives: fear. In her most recent study, she has adapted a classic psychology paradigm called fear conditioning, in which volunteers learn to associate neutral stimuli with negative consequences. She measured people’s heartbeats and their skin’s electrical conductivity, which increases when we feel fearful. Her volunteers showed more fear when stimuli were presented as their heart was contracting than when it was relaxing. The phase of the heartbeat also affected how easily those fear responses were evoked later on. “These signals from the heart can really drive and override conditioned fear responses,” she says. Garfinkel doesn’t like to talk about consciousness because she thinks the concept is woolly. “Consciousness operates on so many levels,” she says. But she does believe she is trying to solve the same puzzles as Blanke and Tallon-Baudry. For Damasio, all three approaches are reconcilable if we take an evolutionary perspective. Four billion years ago, the first primitive organisms monitored changes in their bodily state – equivalent to hunger, thirst, pain and so on – and had feedback mechanisms to maintain equilibrium. The relic of those primitive mechanisms is our autonomic nervous system, which controls bodily functions such as heartbeat and digestion, and of which we are largely unconscious. Then, about half a billion years ago, the central nervous system, featuring a brain, evolved. “It was an afterthought of nature,” says Damasio. But it became the “anchor” of what had once been a more distributed mind. Changes in bodily state were projected onto the brain and experienced as emotions or drives – the emotion of fear, say, or the drive to eat. Subjectivity evolved later again, he argues. It was imposed by the musculoskeletal system, which evolved as a physical framework for the central nervous system and, in so doing, also provided a stable frame of reference: the unified “I” of conscious experience. While Damasio contemplates a synthesis, the other researchers are thinking about applications of their findings. Garfinkel intends to test her idea about an overactive heart-brain axis directly in people affected by trauma. Already, her results lend support to the rationale that drugs designed to act on the cardiovascular system might help treat post- traumatic stress disorder – and indeed such drugs are now in clinical trials. Blanke and Park have filed a patent related to the use of breathing patterns to predict behaviour. Among other applications, it could help in tuning brain-computer interfaces to be more sensitive to the choices of people with disabilities. Tallon-Baudry is working with neurologist Steven Laureys at the University of Liège in Belgium to study the HEP in people with conditions of consciousness, such as coma. They have trained an artificial intelligence to learn how the HEP relates to measurable clinical signs in such patients, to test whether the HEP alone could serve as a diagnostic tool in people whose clinical signs are ambiguous – particularly those in the grey area known as a minimally conscious state. There are philosophical implications to these discoveries too. If consciousness is embodied, that could affect how we think about death, which is currently defined by the World Health Organization as the irreversible loss of brain (but not body) function. The research also has implications for the consciousness of other animals and how we treat them. And if consciousness is embodied, it would mean that a machine or robot with no way of integrating signals from its body will never be truly conscious. “When you start to think through the implications of the embodied self,” says Tallon-Baudry, “they are really quite profound.” ❚ -- 49 of 100 -- 48 | New Scientist Essential Guide | Consciousness FREE WILL AND THE SELF Our sense of self is based on an assumption so fundamental it seems unassailable: that we are masters of our own destiny. But the more we unpick the subtle knot tying conscious experience to the brain, the shakier that assumption feels. ID I really just decide to have fish and chips for lunch?” Humans have been wrestling with such questions for millennia. Maybe not about the fish and chips, but about whether we are truly in control or whether some external agent – be that an omnipotent god or the laws of physics – predetermines the trajectory of our lives. Unfortunately, there are no easy answers. Who is the “I” who decided to have fish and chips? Your gut reaction might tell you that you are a conscious entity controlling your physical body. But that physical body includes the brain that generates your consciousness. There is no splitting the two. The free will debate is an old one, but in the 1980s, psychologist Benjamin Libet really stirred things up. He performed an experiment in which people were told to wait a little while and then press a button, and to note the exact time they decided to act on an ultra- precise clock. They also had electrodes placed on their scalp to measure electrical activity in their brain. This set-up revealed that neuronal activity preceded people’s conscious decision to press the button by nearly half a second. More recently, a similar experiment placed people in a functional magnetic resonance imaging scanner instead of hooking them up to electrodes. This found stirrings in the brain’s prefrontal cortex up to 10 seconds before someone became aware of having made a decision. Although Libet’s work remains controversial, it raises a big question: is our unconscious brain really in the driver’s seat, with our consciousness a mere passenger? Even if we are driving, we may be on rails. Split-second life-or-death decisions – a police officer choosing to fire a gun, say – are often made too quickly for conscious deliberation to play a part. Instead, such choices may be guided by hardwired, unconscious bias. Neuroscientist John-Dylan Haynes at the Berlin Center for Advanced Neuroimaging, who led the brain scanning study, warns against jumping to this conclusion. “I wouldn’t interpret these early [brain] signals as an ‘unconscious decision’,” he says. “I would think of it more like an unconscious bias of a later decision.” Others agree it is a big extrapolation to claim that all of our actions are outside our control and there is no such thing as free will. “Libet deals with the very short-term precursors of very simple actions,” says Patrick Haggard at University College London. Then again, even longer-term decisions and actions are the result of specific brain processes, assuming you buy into the physicalist notion that consciousness can be explained by the workings of physical matter at all. In that view, biological material is nothing more than agglomerations of atoms and molecules that follow the laws of physics. Whenever you decide something, a certain pattern of neurons fires in your brain to turn -- 50 of 100 -- Chapter 3 | Your conscious self | 49 your thought into action – moving towards the kitchen to make coffee, perhaps, or formulating an utterance you will come to regret. Ultimately, that is all down to pulses of electrons – fundamental particles that follow the cast-iron laws of physics, under which everything is determined by what happened immediately before. →- Chapter 6 is all about consciousness and reality- That doesn’t leave much room for free will, apparently. “Physical laws, if they’re deterministic, tell me that everything that I do, everything that happens in the world, including everything that I do, including every decision I ever made, follows logically from the laws of nature [and] the initial conditions of the universe,” says philosopher of physics Jenann Ismael at Columbia University in New York. Since we control neither the laws of nature nor the initial conditions of the universe, we can’t be fully in control of our actions – can we? Not so fast. We should define our terms first, says philosopher Eleanor Knox at King’s College London. “There’s this really strong notion of free will, which is what my students all come into the classroom with,” she says. “To have free will, I must right now be able to behave just with no connection to any contingent plan – so however I like.” Even leaving physics aside, that clearly isn’t the case. “We think that when we make a decision, the locus of control for behaviour is inside,” says Ismael. “But really, there’s all kinds of influences: cultural influences, psychological influences, influences that are more formative of our psychology that we don’t control and so on.” Our choices are the result of a bundle of predilections formed by genetic nature and environmental nurture – a unique product of circumstances we aren’t necessarily in immediate control of. But for Nicholas Humphrey, an emeritus psychologist at the London School of Economics, acknowledging that decisions have an involuntary, material cause in brain processes doesn’t amount to denying free will. “On the contrary, I’m saying that I, myself, am the cause of it,” he says. Humphrey calls his “I” an “embodied self”: the sum of the thoughts, beliefs, desires, dispositions and so on that live within him. The embodied self might not be conscious of every action, but it ultimately determines them – a sort of free will on autopilot. The crucial point is that you can still choose to go against the grain of what you just decided. That, after all, is the core of free will as we experience it. And to say that this sort of free will is incompatible with deterministic laws of physics is rather to get things the wrong way round, unless you are a diehard dualist who advocates a non-physical essence of the mind. “Whatever we call free will must ultimately be explicable by the laws of physics,” says Knox. Unless, of course, you take the illusionist way out – that nothing we experience necessarily corresponds to anything happening out there in the real, physical world. ❚ Voltage Time (ms) Resting Experiments performed by psychologist Benjamin Libet in the 1980s seem to challenge the notion of free will Button pressed First stirrings of brain activity -200 ms 0 Subject becomes aware of decision to press People are asked to note the exact time on an ultra-precise clock when they first decide to press a button Electrodes on the scalp reveal activity in the brain about half a second before they are conscious of their decision to press -- 51 of 100 -- 50 | New Scientist Essential Guide | Consciousness C H A P T E R 4 50 | New Scientist Essential Guide | Consciousness -- 52 of 100 -- Chapter 4 | Sleep and dreaming | 51 Every night, we enter a netherworld of consciousness. The true purpose of sleep remains unclear, but among organisms with some degree of consciousness, it seems to be near-universal that they spend some time in a reduced state of it. It is also clear is that consciousness isn’t like a light switch, on when you are awake and off when you are sleeping. Our brains are in a variety of states of consciousness at different stages of sleep, as is most obvious in the way we dream – another great mystery of our brains’ night-time wanderings. Chapter 4 | Sleep and dreaming | 51 -- 53 of 100 -- 52 | New Scientist Essential Guide | Consciousness N THE face of things, it seems obvious that we sleep so our brains and bodies can rest and recuperate. But why not rest while conscious, so that we can also watch out for threats? And if recuperation means things are being repaired, why can’t that take place while we are awake? Scientists who study how animals eat, learn or mate are unburdened by questions about the purpose of these activities. But for sleep researchers, the “why” is maddeningly mysterious. Sleep is such a widespread phenomenon that it must be doing something useful. Even fruit flies and nematode worms experience periods of inactivity from which they are less easily roused, suggesting sleep is a requirement of the simplest of animals. But surveying the animal kingdom reveals no clear correlation between sleep habits and some obvious physiological need. In fact, there is bewildering diversity in sleep patterns. Some bats spend 20 hours a day slumbering, while large grazing mammals tend to sleep for less than 4 hours a day. Horses, for instance, take naps on their feet for a few minutes at a time, totalling only about 3 hours daily. In some dolphins and whales, newborns and their PABLO HURTADO DE MENDOZA PREVIOUS PAGE: LUMEZIA/ISTOCK > WHY DO WE SLEEP? The average human spends about a third of their life sleeping. If deprived of sleep for too long, we get physically ill. So it is puzzling that we still don’t really know why it is so essential. -- 54 of 100 -- Chapter 4 | Sleep and dreaming | 53 Chapter 4 | Sleep and dreaming | 53 -- 55 of 100 -- 54 | New Scientist Essential Guide | Consciousness mothers stay awake for the entire month following birth. All this variation is vexing to those hoping to discover a single, universal function of sleep. “Bodily changes in sleep vary tremendously across species,” says Marcos Frank at the University of Pennsylvania in Philadelphia. “But in all animals studied so far, the [brain] is always affected by sleep.” So most sleep researchers now focus on the brain. The most obvious feature of sleep, after all, is that consciousness is either lost or, at least in some animals, reduced. And lack of sleep leads to cognitive decline, not only in humans, but also rats, fruit flies and pretty much every other species studied. Much of our slumber is spent in slow-wave sleep, also known as stage 3 or deep sleep, during which there are easily detectable waves of electrical activity across the whole brain, caused by neurons firing in synchrony about once a second. This is interspersed with other phases, including rapid-eye-movement sleep, where brain activity resembles that seen during wakefulness, and transitional stages between the two states. It is slow-wave sleep that is generally thought to do whatever it is that sleep actually does. As well as appearing to be the most different to the brain’s waking activity, the waves are larger at the beginning of sleep, when sleep need is presumably greatest, and then gradually reduce. And if you go without sleep for longer than usual, these slow waves are larger when you do eventually nod off. Explanations for sleep fall into two broad groups: those related to brain repair or maintenance, and those in which the sleeping brain is thought to perform some unique, active function. There has been speculation over the maintenance angle for over a century. It was once a fashionable idea that some kind of toxin built up in the brain during our waking hours, which, when it reached a certain level, made sleep irresistible. Such a substance has never been found, but a modern version of the maintenance hypothesis says that during the day, we deplete supplies of large molecules essential for the operation of the brain, including proteins, RNA and cholesterol, and that these are replenished during sleep. It has been found in animals that production of such macromolecules increases during slow-wave sleep, although critics point out that the figures show a mere correlation, not that levels of these molecules control sleep. The unique function school of thought also has a long pedigree. Sigmund Freud proposed that the purpose of sleep was wish fulfilment during dreaming, although scientific support for this notion failed to materialise. There is good evidence, however, for sleep mediating a different kind of brain function: memory consolidation. Memories aren’t written in stone the instant an event is experienced. Instead, initially labile traces are held as short-term memories, before the most relevant aspects of the experience are transferred to long-term storage. Several kinds of experiment, in animals and people, show that stronger memories form when sleep takes place between learning and recall. Some of the most compelling support for this idea came when electrodes placed into rats’ brains showed small clusters of neurons “replaying” patterns of activity during sleep that had first been generated while the rats had been awake and exploring. “Memory representations are > One theory about the purpose of sleep says it is to stop our brains being overloaded by the new memories we form each day 100 100 80 120 100 150 80 120 Two hypothetical synapses each have a strength of 100 units MORNING Cycle starts New memories formed Ready to start again MORNING EVENING NIGHT Synapses rebalance During sleep, all synapses are scaled down, in proportion to their strength, so that the day's memories are not lost… …while the total strength of all synapses throughout the brain is returned to what it was at the start of the day Later, one synapse becomes stronger due to a new memory -- 56 of 100 -- Chapter 4 | Sleep and dreaming | 55 Some people swear that if they want to wake up at 6 am, they just bang their head on the pillow six times before going to sleep. Nonsense? Maybe not. A study from 1999 shows that it all comes down to some nifty unconscious processing. For three nights, researchers at the University of Lübeck in Germany put 15 volunteers to bed at midnight. They either told the participants they would wake them at 9 am and did; told them they would wake them at 9 am, but actually woke them at 6 am; or said they would wake them at 6 am and did. This last group had a measurable rise in the stress hormone adrenocorticotropin from 4:30 am, peaking around 6 am. People woken unexpectedly at 6 am had no such spike. The unconscious mind, the researchers concluded, can not only keep track of time while we sleep, but also set a biological alarm to jump-start the waking process. The pillow ritual might help set that alarm. The sleeping brain can also process language. In a 2014 study, Sid Kouider at the École Normale Supérieure in Paris and his colleagues trained volunteers to push a button with their left or right hand to indicate whether they heard the name of an animal or object as they fell asleep. They monitored the brain’s electrical activity during training and when the people heard the same words when asleep. Even when asleep, activity continued in the brain’s motor regions, indicating that the sleepers were preparing to push the correct button. The people could also correctly categorise new words they first heard after they had dropped off, showing that they were genuinely analysing the meaning of the words while asleep. It is an ability that makes good evolutionary sense, says Kouider. “If you stop monitoring your environment, you become very vulnerable during sleep… It makes sense that you don’t simply shut down, but continue tracking in a kind of standby mode.” This might explain why some sounds, like our names, wake us more easily than others. This protective monitoring may not last all night, however. A study published in 2016 found that while language processing continues in REM sleep for words heard just before bed, once in deep sleep, all responses disappear as the brain goes “offline” to allow the day’s memories to be processed. “Your cognition about things in the environment declines progressively towards deep sleep,” says Kouider. “Sleep is not all-or-none in terms of cognition; it’s all-or-none in terms of consciousness.” Y O U R B R A I N W H I L E S L E E P I N G BASHTA/ISTOCK -- 57 of 100 -- 56 | New Scientist Essential Guide | Consciousness “There is good evidence for sleep mediating memory consolidation” reactivated during sleep,” says Jan Born at the University of Tübingen in Germany. Many labs remain focused on how memory systems are updated during sleep, but since 2003, a new idea has been gaining traction. It straddles both categories of theory, concerned as it is with neuronal maintenance and memory processing. The hypothesis concerns synapses, the junctions between neurons through which they communicate. We know that when we form new memories, the synapses of the neurons involved become stronger. The idea is that while awake, we are constantly forming new memories and therefore strengthening synapses. But this strengthening cannot go on indefinitely: it would be too expensive in terms of energy, and eventually there would be no way of forming new memories as our synapses would become “maxed out”. The proposed solution is slow-wave sleep. In the absence of any appreciable external input, the slow cycles of neuronal firing gradually lower synaptic strength across the board, while maintaining the relative differences in strength between synapses, so that new memories are retained (see diagram, page 54). There is now much evidence to support what is known as the “synaptic homeostasis hypothesis“. In humans, brain scans show that our grey matter uses more energy at the end of the waking day than at the start. Giulio Tononi and Chiara Cirelli at the University of Wisconsin-Madison, who proposed the hypothesis, have shown that synaptic strength increases in rodents and fruit flies during wakefulness and falls during sleep. The pair have also shown that when people learn a task that uses a specific part of the brain, that area generates more intense slow waves during subsequent sleep. This kind of downscaling is best done “offline”, says Tononi. “You can activate your brain in all kinds of ways, because you don’t need to behave or learn.” Synaptic homeostasis hasn’t won over everyone, but it is certainly getting a great deal of attention. It is, says Born, “currently the most influential [theory] among sleep researchers”. Frank, however, would like Tononi and Cirelli to provide more detail about mechanisms. Jerry Siegel isn’t convinced either. A neuroscientist at the University of California, Los Angeles, Siegel is sticking with his provocative theory that sleep is simply an adaptive way of saving energy when not doing essential things, such as foraging or breeding, which are in fact more dangerous than napping someplace safe. For Siegel, sleep habits reflect the variety of animal lifestyles, with different species sleeping for different purposes. It is certainly possible that a phenomenon as complex as sleep performs a multitude of functions, says Jim Horne, who studies the impact of sleep loss on health at Loughborough University, UK. What’s more, given the complexity of the human brain, our sleep may well be among the most complicated of all. Perhaps, then, it should be no surprise that theories of sleep function are so diverse. Fathoming whether the big “why” of sleep will yield a single, succinct solution or require myriad answers will probably keep biologists up at night for a little while yet. In that sense, perhaps appropriately, it is a mirror of the situation with consciousness generally. ❚ -- 58 of 100 -- Chapter 4 | Sleep and dreaming | 57 It is the brain’s natural twilight zone – a halfway stage between wakefulness and sleep that we all experience as we drop off. Known as hypnagogia or “N1”, it is often characterised by vivid dreams – although usually people progress into deep sleep and forget the dreams when they wake. It repays closer attention. “If you are a good observer, you will notice that those spots have a hallucinoid quality to them,” says Tore Nielsen, a sleep researcher at the Montreal Sacred Heart Hospital in Canada. We don’t know what causes hypnagogia, but one idea is that some parts of the brain are falling asleep ahead of the rest. “It’s known that different parts of the brain tune out at different times,” says Nielsen. It has long been thought that hypnagogia can inspire creativity. Chemist Friedrich August Kekulé had his insight about the ring structure of benzene while half asleep. The surrealist artist Salvador Dalí tuned in to his creativity by letting himself drop off while suspending a spoon over a metal plate. As he fell asleep, the spoon would crash down, jerking him awake while the dream images were still fresh in his mind. Inventor Thomas Edison did something similar by holding a steel ball in each hand as he drifted off while trying to grapple with a difficult problem. In 2021, Delphine Oudiette at the National Institute of Health and Medical Research in Paris and her team tested the link with creativity objectively by getting people to tackle a tricky maths problem using a particular method – without telling them there was a simple shortcut. While grappling with the problem, they were encouraged to take a short nap while holding a bottle in their hand, during which they were wired up to an electroencephalogram (EEG). On returning to the maths problem, 83 per cent of those who had only reached the N1 stage of sleep as revealed by the EEG worked out the hidden shortcut, compared with 31 per cent of those who remained awake and 14 per cent of those who had progressed to deeper N2 sleep. Hypnagogia has a darker side, however. It can sometimes trigger one terrifying kind of sleep paralysis, when the nerve inhibition that normally accompanies our dreams kicks in before someone is fully asleep. “Hypnagogia is largely an uncharted domain,” says Nielsen. “We are still developing tools for navigating it.” H Y P N A G O G I A THE MEANING OF DREAMING Dreams are a signature feature of the altered state of consciousness we call sleep. We are beginning to understand how our brains shape our dreams, and why they contain such an eerie mixture of the familiar and the bizarre. ARY SHELLEY’S involved a pale student kneeling beside a corpse that was jerking back to life. Paul McCartney’s contained the melody of Yesterday, while James Cameron’s feverish visions inspired the Terminator films. With their eerie mixture of the familiar and the bizarre, it is easy to look for meaning the nightly wanderings of our dreams. Why do our brains take these journeys and why do they contain such outlandish twists and turns? Anyone who has ever awoken feeling amazed by their night’s dream only to forget its contents by the time they reach the shower will understand the difficulties of studying such an ephemeral state of mind. Some of the best attempts to catalogue dream features either asked participants to jot them down as soon as they woke up every morning or, better still, invited volunteers to sleep in a lab, where they were awoken and immediately questioned at intervals in > -- 59 of 100 -- 58 | New Scientist Essential Guide | Consciousness the night. Such experiments have shown that our dreams tend to be silent movies, with just half containing traces of sounds. It is even more unusual to enjoy a meal or feel damp grass beneath your feet: taste, smell and touch appear only very rarely. Similar studies have tried to pin down some of the factors that might influence what we dream about, though they have struggled to find anything reliable. You might expect your dreams to reveal something about your personality, but traits such as extroversion or creativity don’t seem to predict features of someone’s journeys through the land of nod. Shelley and McCartney’s dreams aren’t that unlike ours. “People’s dreams seem to be more similar than different,” says Mark Blagrove at Swansea University in the UK. This suggests common symbols in dreams might represent shared anxieties and desires, but attempts to find these have also been disappointing. A more fruitful approach has been to look at the brain’s activity during sleep for clues to the making of our dreams. Of particular interest is the idea that sleep helps to cement our memories for future recall. After first recording an event in the hippocampus – which can be thought of as the human memory’s printing press – the brain then transfers its contents to the cortex, where it files the recollection for long-term storage. This has led some psychologists, including Blagrove, to suspect that certain elements of the memory may surface in our dreams as the different pieces of information are passed across the brain. By studying participants’ diaries of real-life events and comparing them with their dream records, his team has found Sleep occurs in repeating cycles, each about 90 minutes long. In a cycle, there are three stages of non-REM sleep, where brain activity becomes gentle and rhythmic, eventually heading into slow-wave, deep sleep. After slow-wave sleep, the brainwaves change pattern again, the eyes start roiling under their lids and most of the muscles in the body become paralysed to stop us acting out our dreams. This is REM sleep, and the proportion of time spent in this stage increases in each successive sleep cycle throughout the night, so that by early morning, much of those 90 minutes can be spent in REM. We do dream in other stages of sleep, but these dreams tend to be unemotional, concerned with simple things and hard to remember. In short, they are boring. REM sleep is where classic dreams occur, those with bizarre juxtapositions, physically impossible feats and emotional, puzzling events. W H E N D R E A M S H A P P E N -- 60 of 100 -- Chapter 4 | Sleep and dreaming | 59 that memories enter our dreams in two separate stages. They first float into our consciousness on the night after the event itself, which might reflect the initial recording of the memory, and then they reappear between five and seven days later, which may be a sign of consolidation. Even so, it is quite rare for a single event to appear in a dream in its entirety – instead, our memories emerge piecemeal. “What usually happens is that small fragments are recombined into the ongoing story of the dream,” says Patrick McNamara at Northcentral University in Arizona. And the order in which the different elements appear might reflect the way a memory is broken down and then repackaged during consolidation. One of McNamara’s studies, which compared one individual’s dream and real-life diaries over a two-month period, found that a sense of place – a recognisable room, for instance – was the first fragment of a memory to burst onto the subject’s dreamscape, followed by characters, actions and finally physical objects. While it may cement a memory into our synapses during consolidation, the sleeping brain also forges links to other parts of your mental autobiography, allowing you to see associations between different events. This might dredge up old memories and plant them in our dreams, which in turn might explain why we often dream of people and places that we haven’t seen or visited for months or even years. It could also lie behind those bizarre cases of mistaken identity while dreaming, when objects or people can appear to be one thing, but assume another shape or character. “It’s a by-product of the way the brain blends different elements,” says McNamara. Our dreams are more than a collection of characters and objects, of course. Like films or novels, they tell their stories in many different styles – from a trivial and disordered sequence to an intense poetic vision. Our emotional undercurrents seem to be the guiding force here. Ernest Hartmann, a psychiatrist at Tufts University in Massachusetts, has studied the dream diaries of people who have recently suffered a painful personal experience or grief. He found that they are more likely to have particularly vivid dreams that focus on a single central image, rather than a meandering narrative. These dreams are also more memorable than those from other, more placid times. Why would our emotions drive the form of our dreams in this way? Hartmann suspects this might also reflect underlying memory processes – our emotions are known to guide which memories we store and later recall. Perhaps the intense images are an indication of what a difficult process it is integrating a traumatic event with the rest of our autobiography. The result may help us to come to terms with that event. “I think it makes a new trauma less traumatic,” says Hartmann, though he readily admits that his hypothesis is difficult to prove. Despite these advances, many, many mysteries remain. Top of the list is the question of the purpose of our dreams: are they essential for the preservation of our memories, for instance, or could we manage to store our life’s events without them? “There’s no consensus,” says McNamara. But if we understood their origins, we would get a better grasp on consciousness in general. ❚ A good night’s sleep of about 8 hours is comprised of five or six cycles. We get a higher proportion of REM sleep after about 5.5 hours REM AW AA A W W KE First Second Cycle Third Fourth Fifth TRANSITIONAL STAGES SLOW-WAVE SLEEP Brain repair and maintenance DREAMING Can occur at any stage but more common during REM Key period for REM sleep STA TT GE 2 STA TT GE 1 STA TT GE 3 Time (hours) 0 1 2 3 4 5 6 7 8 -- 61 of 100 -- 60 | New Scientist Essential Guide | Consciousness C H A P T E R 5 Consciousness isn’t an on-off state, but more like a dimmer switch. Or perhaps you might view it as a ladder of states, with zero consciousness at the bottom and maximum consciousness at the top. Many altered states of consciousness exist, from induced unconsciousness in the form of anaesthesia to hallucinatory states that, besides being induced by drugs, occur naturally in many of us. And even with states regarded as minimally conscious, from comas to a persistent vegetative state, it seems things aren’t as clear-cut as we once thought. 60 | New Scientist Essential Guide | Consciousness -- 62 of 100 -- Chapter 5 | Altered consciousness | 61 Chapter 5 | Altered consciousness | 61 -- 63 of 100 -- 62 | New Scientist Essential Guide | Consciousness T WAS a Japanese surgeon who performed the first known surgery under anaesthetic, in 1804, using a mixture of potent herbs. In the West, the first operation under general anaesthetic took place at Massachusetts General Hospital in 1846. A flask of sulphuric ether was held close to the patient’s face until he fell unconscious. Since then, a slew of chemicals have been co-opted to serve as anaesthetics, some inhaled, like ether, and some injected. The people who gained expertise in administering these agents developed into their own medical speciality. Although long overshadowed by the surgeons who patch you up, the humble “gas man” does just as important a job, holding you in the twilight between life and death. The development of general anaesthesia has transformed surgery from a horrific ordeal into a gentle slumber. It is one of the most common medical procedures in the world. Perhaps it isn’t that surprising that we don’t know how it works: we still don’t understand consciousness, after all, so how can we comprehend its disappearance? Altered consciousness doesn’t only happen under a general anaesthetic, of course – it occurs whenever we drop off to sleep, or if we are unlucky enough to be whacked on the head. But anaesthetics do allow neuroscientists to manipulate our consciousness safely, reversibly and with exquisite precision. We have long known that there are different levels of anaesthesia (see diagram, overleaf) – just PABLO HURTADO DE MENDOZA PREVIOUS PAGE: LUMEZIA/ISTOCK > THE MYSTERY OF ANAESTHESIA Many of us have put our faith in the ability of doctors to use general anaesthesia to remove our consciousness safely, even if we don’t really understand how it works. The truth is, given that no one knows what they are removing, no one does. -- 64 of 100 -- Chapter 5 | Altered consciousness | 63 Chapter 5 | Altered consciousness | 63 -- 65 of 100 -- 64 | New Scientist Essential Guide | Consciousness as consciousness exists on a scale, so we slide along that scale. “The process of going into and out of general anaesthesia isn’t like flipping a light switch,” says George Mashour, an anaesthetist at the University of Michigan in Ann Arbor. “It’s more akin to a dimmer switch.” A typical subject first experiences a state similar to drunkenness, which they may or may not be able to recall later, before falling unconscious, which is usually defined as failing to move in response to commands. As they progress deeper into the twilight zone, they now fail to respond to even the penetration of a scalpel – which is the point of the exercise, after all – and at the deepest levels may need artificial help with breathing. These days, anaesthesia is usually started off with injection of a drug called propofol, which gives a rapid and smooth transition to unconsciousness. Unless the operation is only meant to take a few minutes, an inhaled anaesthetic, such as isoflurane, is then usually added to give better minute-by-minute control of the depth of anaesthesia. Since they were first discovered, one of the big mysteries has been how the members of such a diverse group of chemicals can all result in the loss of consciousness. Other drugs work by binding to receptor molecules in the body, usually proteins, in a way that relies on the drug and receptor fitting snugly together like a key in a lock. Yet the long list of anaesthetic agents ranges from large, complex molecules, such as barbiturates or steroids, to the inert gas xenon, which exists as mere atoms. How could they all fit the same lock? For a long time, there was great interest in the fact that the potency of anaesthetics correlates strikingly with how well they dissolve in olive oil. The popular “lipid theory” said that instead of binding to specific protein receptors, the anaesthetic physically disrupted the fatty membranes of nerve cells, causing them to malfunction. In the 1980s, though, experiments in test tubes showed that anaesthetics could bind to proteins in the absence of cell membranes. Since then, protein receptors have been found for many anaesthetics. Propofol, for instance, binds to receptors on nerve cells that normally respond to a chemical messenger called GABA. Presumably, the solubility of anaesthetics in oil affects how easily they reach the receptors bound in the fatty membrane. But that solves only a small part of the mystery. We still don’t know how this binding affects nerve cells, and which neural networks they feed into. “If you look at the brain under both xenon and propofol anaesthesia, there are striking similarities,” says Nick Franks at Imperial College London, who overturned the lipid theory in the 1980s. “They Losing consciousness under anaesthesia is not so much flipping a light switch as turning down a dimmer switch LIGHT- HEADEDNESS AMNESIA UNCONSCIOUSNESS Failure to respond to commands STAGES OF ANAESTHESIA FAILURE TO RESPOND TO PAIN May need mechanical ventilation to maintain breathing -- 66 of 100 -- Chapter 5 | Altered consciousness | 65 must be triggering some common neuronal change, and that’s the big mystery.” Many anaesthetics are thought to work by making it harder for neurons to fire, but this can have different effects on brain function, depending on which neurons are being blocked. So brain-imaging techniques such as functional MRI scanning, which tracks changes in blood flow to different areas of the brain, are being used to see which regions of the brain are affected by anaesthetics. Such studies have been successful in revealing several areas that are deactivated by most anaesthetics. Unfortunately, so many regions have been implicated that it is hard to know which, if any, are the root cause of the loss of consciousness. But is it even realistic to expect to find a discrete site or sites acting as the mind’s “light switch”? It isn’t if you adhere to theories of consciousness such as the global workspace theory that see consciousness as a widely distributed phenomenon, in which we only become conscious of an experience if incoming signals are broadcast to a network of neurons spread through the brain. ←- Page 14 has the low-down on- global workspace theory- The idea has gained support from recordings of the brain’s electrical activity using electroencephalograph (EEG) sensors on the scalp as people are given anaesthesia. This has shown that, as consciousness fades, there is a loss of synchrony between areas of the cortex – the outermost layer of the brain important in attention, awareness, thought and memory. This process has also been visualised using functional magnetic resonance imaging scans. One study of what happens during propofol anaesthesia when patients descend from wakefulness, through mild sedation to the point at which they fail to respond to commands, found that while small “islands” of the cortex lit up in response to external stimuli when people were unconscious, there was no spread of activity to other areas, as there was during wakefulness or mild sedation. Another study, which slowed down this process to look at it in more detail, gave volunteers a mild electric shock at different points as they went under, and took EEG readings of the response. At the deepest levels of anaesthesia, the primary sensory cortex was the only region to respond to the electric shock, supporting the idea that loss of consciousness is associated with a blockage of long-distance communication in the brain – as if the message is somehow reaching the mailbox, but no one is picking it up. ❚ BROADLY EQUIVALENT TO UNCONSCIOUSNESS due to brain damage – includes persistent vegetative state and coma BEING DRUNK SLEEP -- 67 of 100 -- 66 | New Scientist Essential Guide | Consciousness THE POWER OF HALLUCINATION In recent years, it has become clear that hallucinations are much more than a rare symptom of mental illness or the result of mind-altering drugs. Their appearance elsewhere has led to a better understanding of how the brain can create a world that doesn’t really exist. ALLUCINATIONS are sensations that appear real but aren’t elicited by anything in our external environment. They aren’t only visual – they can be sounds, smells, even experiences of touch. It is difficult to imagine just how real they seem unless you have experienced one. As Sylvia, a woman who has had musical hallucinations for years, explains, it isn’t like imagining a tune in your head – more like “listening to the radio”, she says. There is evidence to support the idea that these experiences are authentic. In 1998, researchers at King’s College London scanned the brains of people having visual hallucinations. They found that brain areas that were active are also active while viewing a real version of the hallucinated image. Those who hallucinated faces, for example, activated areas of the fusiform gyrus, known to contain specialised cells that are active when we look at real faces. The same was true with hallucinations of colour and written words. It was the first objective evidence that hallucinations are less like imagination and more like real perception. Their convincing nature helps explain why hallucinations have been given such meaning – even considered messages from gods. But as it became clear that they can be symptoms of mental health conditions such as schizophrenia, they were viewed with increasing suspicion. We now know that hallucinations occur in people without a mental illness. The likelihood of experiencing them increases in your 60s; 5 per cent of us will experience one or more hallucinations in our life. Many people hallucinate sounds or shapes before they drift off to sleep, or just on waking. People experiencing extreme grief have also been known to hallucinate in the weeks after their loss – often visions of their loved one. But the hallucinations that may reveal the most about how our brain works are those that crop up in people who have recently lost a sense. This is known as Charles Bonnet syndrome. Bonnet, a Swiss scientist who lived in the early 1700s, first described the condition in his grandfather, who had begun to lose his vision. One day, the older man was sitting talking to his granddaughters when two men appeared, wearing majestic cloaks of red and grey. When he asked why no one had told him they would be coming, he discovered that only he could see them. It is a similar story with Sylvia. After an ear infection caused severe hearing loss, she began to hallucinate a sound that was like a cross between a wooden flute and a bell. At first, it was a couple of notes that repeated over and over. Later, there were whole tunes. “You’d expect to hear a sound that you recognise, maybe a piano or a trumpet, but it’s not like anything I know in real life,” she says. Max Livesey was in his 70s when Parkinson’s disease destroyed the nerves that send information from the nose to the brain. Despite his olfactory loss, one day he suddenly noticed the smell of burning leaves. The odours intensified over time, ranging from burnt wood to a horrible onion-like stench. “When they’re at their -- 68 of 100 -- Chapter 5 | Altered consciousness | 67 most intense, they can smell like excrement,” he says. They were so powerful that they made his eyes water. Sensory loss doesn’t have to be permanent to bring on such hallucinations. When our senses are diminished, all of us have the potential to hallucinate. It can take just 30 to 45 minutes for people to experience hallucinations if they try a simple visual deprivation technique, such as the Ganzfeld procedure. This involves seating yourself in a room that is evenly lit, cutting a table-tennis ball in half, taping each segment over your eyes and then listening to some white noise over headphones. In one study run by Jiří Wackermann at the Institute for Frontier Areas of Psychology and Mental Health in Freiburg, Germany, one volunteer saw a jumping horse. Another saw an eerily detailed mannequin. “It was all in black… had a long narrow head, fairly broad shoulders, very long arms,” they said. These hallucinations seem to come about because the brain can’t tolerate inactivity in areas where it is usually constantly stimulated. These unreal experiences could thus provide a glimpse into the way our brains stitch together our perception of reality. Although bombarded by thousands of sensations every second, the brain rarely stops providing you with a steady stream of consciousness. When you blink, your world doesn’t disappear. Nor do you notice the hum of traffic outside or the tightness of your socks (until they are mentioned, at least). Processing all of those things all the time would be a very inefficient way to run a brain. Instead, it takes a few shortcuts. Sound waves, for example, enter the ear and are transmitted to the brain’s primary auditory cortex, which processes the rawest elements, such as patterns and pitch. From here, signals get passed on to higher brain regions that process more complex features, such as melody and key changes. Instead of relaying every detail up the chain, the brain combines the noisy signals coming in with prior experiences to generate a prediction of what is happening. If you hear the opening notes of a familiar tune, you expect the rest of the song to follow. That prediction passes back to lower regions, where it is compared with the actual input, and to the frontal lobes, which perform a kind of reality check, before it pops up into our consciousness. Only if a prediction is wrong does a signal get passed back to higher areas, which adjust subsequent predictions. You can test this for yourself. Anil Seth at the University of Sussex, UK, suggests listening to sine- wave speech, basically a degraded version of a speech recording. The first time, all you will hear is a jumble of beeps and whistles. But if you listen to the original recording and then switch back to the degraded version, you will suddenly be able to make out what is being said. All that has changed is your brain’s expectations of the input. It means it now has better information on which to base its prediction. “Our reality,” says Seth, “is merely a controlled hallucination, reined in by our senses.” This idea is consistent with what was happening to Sylvia. Although she was mostly deaf, she could still make out some sound – and she discovered that listening to familiar Bach concertos suppressed her hallucinations. Timothy Griffiths, a cognitive Sensory deprivation is one way to stimulate hallucination > ULZA/ISTOCK PHOTO -- 69 of 100 -- 68 | New Scientist Essential Guide | Consciousness neurologist at Newcastle University, UK, scanned Sylvia’s brain before, after and while listening to Bach, and had her rate the intensity of her hallucinations throughout. They were at their quietest just after the real music was played, gradually increasing in volume until the next excerpt. The brain scans showed that during her hallucinations, the higher regions that process melodies and sequences of tones were talking to one another. Yet, because Sylvia is profoundly deaf, they weren’t constrained by the real sounds entering her ears. Her hallucinations are her brain’s best guess at what is out there. Understanding why people react differently to a diminished sensory environment could reveal why some are more prone to the delusions and hallucinations associated with certain mental health conditions. People with schizophrenia often have overactivity in their sensory cortices, but poor connectivity from these areas to their frontal lobes. So the brain makes lots of predictions that aren’t given a reality check before they pass into conscious awareness, says Flavie Waters, a clinical neuroscientist at the University of Western Australia in Perth. In conditions like Charles Bonnet syndrome, it is underactivity in the sensory cortices that triggers the brain to start filling in the gaps, and there is no actual sensory input to help it correct course. In both cases, says Waters, the brain starts listening in on itself, instead of tuning in to the outside world. Something similar seems to be true of hallucinations associated with some recreational drug use (see “Psychedelia: A higher state?”, right). The knowledge that hallucinations can be a by-product of how we construct reality might change how we experience them. In his later years, the late psychologist Oliver Sacks experienced hallucinations after his eyesight began to fail. When he played the piano, he would occasionally see showers of flat symbols when he was looking carefully at musical scores. “I have long since learned to ignore my hallucinations, and occasionally enjoy them,” said Sacks. “I like seeing what my brain is up to when it is at play.” ❚ From magic mushrooms and ayahuasca – a potion used in South America during certain religious rites – to LSD and ketamine, using chemical means to achieve altered, hallucinogenic states of consciousness has been part of human culture for millennia. In recent years, such mind-altering drugs have been an increasing focus of medical attention as a treatment for conditions such as depression and post-traumatic stress disorder. Only recently have we discovered how these experiences are produced, however. In 2016, researchers at Imperial College London monitored brain activity in 19 volunteers who had taken ketamine, 15 who had consumed LSD and 14 who were under the influence of psilocybin, a hallucinogenic compound in magic mushrooms. The scans showed that the volunteers’ hallucinations arose from the combined activity of brain regions that don’t normally communicate with each other. Regions responsible for vision, attention, movement and hearing became far more connected, while networks thought to give us an appreciation of the self became less so. That may be why people who take LSD often say they feel “ego dissolution” – their sense of self disintegrating – instead becoming more at one with the world around them. A reanalysis of this research by Anil Seth at the University of Sussex, UK, suggests that the brain on psychedelics might even, on some measures, be in a “higher” state of consciousness than the waking brain. “We see an increase in the diversity of signals from the brain,” he says. “The brain is more complex in its activity.” P S Y C H E D E L I A : A H I G H E R S T A T E ? -- 70 of 100 -- Chapter 5 | Altered consciousness | 69 CURIOSITIES OF CONSCIOUSNESS In some rare brain conditions, people noticeably experience the world very differently from the average individual. This provides another angle of attack on the problem of consciousness. HERE is no lack of rare conditions that seem to suggest altered states of consciousness. Take phantom limb syndrome – the sensation some people have that their missing limb is still present – or Cotard syndrome, in which people believe they are dead. Or calendar synaesthesia, perhaps one of the most striking examples of how the body and brain interact to shape our minds. When most people think about what they plan to do in November, say, they have a hazy concept of the months ahead. But people with calendar synaesthesia can actually see a calendar in front of them, often in a strange formation – a hula hoop that touches them in the centre of their chest, for instance. Neuroscientist V. S. Ramachandran, who has studied calendar synaesthesia and many other conditions, suspects this hints at the way our brains cope with the non-intuitive concept of months. “The brain didn’t have time in evolution for creating the representation of time – it’s too abstract,” he says. “What evolution often does is take pre-existing hardware and re-tool it.” We did develop tools for conceptualising our surroundings. “So you take a spatial map, map time onto space, and you get a calendar,” he says. For synaesthetes, that calendar seems to be visible in space. Studies of such conditions can help illuminate some of the mysteries of consciousness by revealing the blurry boundary between the self and the outside world. One of Ramachandran’s most unusual cases is a man called David, who has Capgras syndrome. This is usually characterised by the belief that a loved one has been replaced by an impostor. David, though, believes himself to be the impostor. “He looks at his reflection and says: ‘Mom, that’s the real David. If he comes back, are you going to disown me?’,” says Ramachandran. When pressed for an explanation, David said the only logical one was that he had a long-lost twin and they were separated at birth. “It’s an ingenious solution to the dilemma that he’s in, and it sends a chill down your spine. It takes you into questions about what the self is.” Our sense of self is also affected by those around us. For instance, when people with mirror-touch synaesthesia see someone else being touched, it feels as though they are being touched in the same way. People who experience such dramatic differences in perception may be rare, but we are all capable of distorting our sense of self. A simple experiment can > -- 71 of 100 -- 70 | New Scientist Essential Guide | Consciousness show how. Try looking at yourself in a double-reflecting mirror – two mirrors facing each other such that the second reflects the image in the first. Then, raise your right arm. The first reflection is a normal mirror image, but the second is inversed, which we aren’t used to seeing – it is a doppelganger, raising its right arm when you do and miming your behaviour. Keep looking and something odd can happen to your sense of self – you start feeling you are out there. What’s more, if you watch your arm moving in the second mirror, you may see a slight delay. Exactly why this happens is something Ramachandran and his team are working on, but we know that neurons in your brain telling your hand to move fire milliseconds before you consciously decide to move it. To avoid the sensation of being a puppet, your brain smoothes things out so that everything feels simultaneous. Ramachandran suspects that when you see this doppelganger in the mirror, your brain doesn’t compute it as you – so the correction isn’t applied. In essence, you are seeing the unconscious machinery of the brain laid bare. These insights build a picture of our consciousness as something very flimsy – but there is a limit to what it can tell us about the hard problem of consciousness. “You can figure out the circuitry and all that, but it still leaves the qualia, or experiences – whether it’s an orgasm or the colour of red or the flavour of Marmite or curry or whatever,” says Ramachandran “That problem will remain with us until we find a new way to do science. Maybe it’ll be a permanent dual view of the world. The inside view and the outside view.” ❚ In the 1964 film Dr Strangelove, the lead character had an unusual affliction: his right arm seemingly had a mind of its own. Such a condition really does exist, although it is vanishingly rare. People with so-called alien hand syndrome find that their affected limb reaches out and grabs things they have no wish to pick up. They might try restraining it with their other hand, and if that doesn’t work, “they sometimes come to the surgery with their hand tied up”, says Sergio Della Sala, a neuroscientist at the University of Edinburgh, UK, who studies the condition. The cause is injury to the brain, usually in a region known as the supplementary motor area (SMA). Work on monkeys has shown that another part of the brain, the premotor cortex, generates some of our actions unconsciously in response to things we see around us. The SMA then kicks in to allow the movement or stop it, but damage to the SMA can wreck this control – hence the anarchic hand, acting on every visual cue. A few people are unfortunate enough to have damage to the SMA on both sides of the brain, and experience both hands acting outside their control. They are at the mercy of environmental triggers, says Della Sala. The system sounds like the very opposite of free will – Della Sala calls it “free won’t”. The findings suggest that, while it feels like our actions are always under our conscious control, in reality, there is a lot of unconscious decision-making going on too. If that sounds implausible, have you ever been driving somewhere on a day off and found yourself heading towards the office the moment you hit part of your normal route to work? That is your premotor cortex responding to an environmental cue. F R E E W O N ’ T -- 72 of 100 -- Chapter 5 | Altered consciousness | 71 COVERT CONSCIOUSNESS It has been one of the most eye-opening insights into consciousness in recent decades – that people believed to be in an unconsciousness state after traumatic brain injury might be more aware than we thought. S RECENTLY as the late 1990s, it was assumed that people in a vegetative state, by definition, had no conscious awareness. They would show signs of sleep and wake cycles, and occasionally open their eyes or make involuntary movements, but weren’t aware of themselves or the people around them. However, Adrian Owen, then at the MRC Cognition and Brain Sciences Unit in Cambridge, UK, had a worrying thought: what if we were wrong? Neurologists have long been aware of locked-in syndrome, in which people are awake and aware but unable to move almost all of their body. It was first defined in medical textbooks in 1966, but must have been known about much earlier; it was described in Alexandre Dumas’s 1844 tale, The Count of Monte Cristo. People who are locked in need help breathing and many can communicate only using eye movements. But they aren’t classed as having a condition of consciousness because, unlike people in a coma, vegetative state or minimally conscious state, they are fully conscious (see “Six reduced states of consciousness”, page 73). Still, a diagnosis can take months, or even years if eye movement is limited. Owen wondered whether people in a vegetative state could also have a hidden awareness. At the time, this was dismissed as a “bonkers idea”, he says, not least because it made people feel uncomfortable that someone might be trapped inside their body without anyone knowing. Nevertheless, Owen and his team began to test the idea. Their first patient was Kate, a woman left in a vegetative state by a virus. In 1997, they scanned Kate’s brain using positron emission tomography, which can measure brain activity, while showing her pictures of her family or playing familiar speech. To their surprise, her brain responded just as you might expect a conscious person’s brain to respond. But Owen’s team faced a problem: a lot of neural activity happens automatically, so the result didn’t necessarily prove she was conscious. It took another decade to work out a solution. In 2006, Owen and his colleagues showed that a 23-year-old woman in a vegetative state could respond to instructions, by asking her to imagine walking around her house or playing tennis. These two mental tasks require different brain activity, which can be identified from brain scans. It confirmed, beyond any doubt, that she was consciously aware of herself and the researchers, and that she had the ability to respond to their requests. Disorders of consciousness are notoriously difficult to diagnose. Most doctors use variations of the Glasgow Coma Scale to assess someone’s ability to open their eyes in reaction to various stimuli, and their verbal responses and motor movements. They can also use brain scans to identify physical damage. However, to identify covert consciousness, you need to use functional magnetic resonance imaging (fMRI) or several electroencephalograph (EEG) tests over time to verify brain activity that reflects comprehension and the capacity to follow commands. “But we’re just not > -- 73 of 100 -- 72 | New Scientist Essential Guide | Consciousness screening patients for this level of higher function,” says Nicholas Schiff at Weill Cornell Medical College in New York. “And it’s not that hard to find them when we do.” The real canary in the coal mine, says Schiff, was a study carried out in 2017 by Brian Edlow at Massachusetts General Hospital. Edlow knew that covert consciousness had been discovered in people who’d had months or years to recover from their injuries, but he wondered whether it might exist in people with more recent brain injuries. He and his colleagues scanned the brains of 16 seemingly unconscious people with severe head injuries. During the scans, he asked them to do mental tasks, such as “imagine squeezing your right hand”. Of eight people who had no behavioural evidence of awareness, four could follow his instructions. It was a small study, but it had massive ramifications. “These people were in intensive care,” says Schiff. “What if you’d withdrawn their care?” Even for those who are provided with life-sustaining treatment, a misdiagnosis might result in limited rehabilitation that thwarts an opportunity for recovery. A diagnosis of covert consciousness can be life- changing. For instance, one man, thought to be in a vegetative state, made sporadic head movements that had been dismissed as random. Once Schiff’s team became aware of his covert consciousness, these movements were given more attention. A researcher developed a head-mounted computer mouse for him, which he used to control a keyboard. Eventually, he was able to write Schiff an email to give his own consent to join Schiff’s next study. There is no data on the exact number of people with conditions of consciousness across the world, but Schiff has been involved in an international investigation into rates of misdiagnosis. A conservative estimate is that 1 in 10 people who appear to be in a coma, vegetative state or minimally conscious state actually has covert consciousness. “It’s a big problem,” says Schiff. “And now we know it’s not a rare problem.” These new insights have been accompanied by other advances in medical science. Twenty years ago, there wasn’t a lot you could do for people in a vegetative state other than hope that they would slowly recover, or have a rare, spontaneous awakening. Now, we know that some people in a vegetative state have the capacity to be awoken with the right intervention. There is no golden bullet, but some drugs seem to assist the process, in certain cases. Schiff’s team implanted electrodes in the thalamus of a man who had been in a minimally conscious state for six years following an assault. Improvements were seen straight away. By the end of the six-month trial, the man could eat, speak and watch a movie. In 2016, Martin Monti at the University of California, Los Angeles, and his colleagues showed that something similar might be possible by stimulating the thalamus using low-intensity ultrasound. Others are focusing on different areas of the brain and on the vagus nerve, which runs between the brain, the thalamus and several areas of the body. These advances raise new ethical questions. Some people may see surviving a brain injury with some degree of consciousness as worse than being in a vegetative state, because you can experience pain and have some awareness of your predicament. “Some people in a vegetative state can be awoken with the right intervention” -- 74 of 100 -- Chapter 5 | Altered consciousness | 73 B R A I N D E A D A person is brain dead when they no longer have any brain activity. They won’t regain consciousness or be able to breathe without artificial life support. C O M A Someone in a coma is unconscious and has low levels of brain activity. They will be unresponsive to sound and pain and will have greatly reduced reflexes, such as swallowing or coughing. They may be able to breathe on their own. V E G E T A T I V E S T A T E A state in which a person may have some reflexes, including yawning and eye movements, but shows no awareness of themselves or their environment. M I N I M A L L Y C O N S C I O U S As a person begins to show intermittent awareness of themselves or their environment, they are said to be in a minimally conscious state. As they develop the ability to communicate, they are said to have emerging consciousness. C O V E R T C O N S C I O U S N E S S Some people who are diagnosed as being in a coma, vegetative state or minimally conscious state may have periods of awareness that they are unable to reveal because they can’t make any purposeful movements. This differs from locked-in syndrome because the person still has cognitive troubles, such as memory loss, or inconsistent consciousness. L O C K E D - I N S Y N D R O M E A person who is locked in is fully conscious, so isn’t classed as having a condition of consciousness, but is unable to move most of their body. Sometimes, they can communicate through eye and facial movements. Their condition is normally associated with an injury to the brain stem. S I X R E D U C E D S T A T E S O F C O N S C I O U S N E S S Some improvements using drugs have proved to be only temporary and to produce diminishing returns, with people lapsing back into unconsciousness. And then there is the pain of discovering a loved one has covert consciousness, but that you can’t offer any means of continuing the conversation. Another question is whether it is possible for people with conditions of consciousness to have a more meaningful conversation about their welfare. “Once a person shows signs of awareness, can they decide whether to live or die?” asks medical ethicist Joseph Fins, also at Weill Cornell Medical College. Historically, we have thought about such decisions as all or nothing – people are either capable of consenting to treatment or not, he says. But now, we have this third scenario, he says, a person who may be aware enough to answer difficult questions some of the time. “Now that people with brain injuries are emerging and communicating, we have to listen to what they say,” says Fins. One thing we do know is that a locked-in life isn’t necessarily a miserable one. A small survey of people who could only communicate using eye movements found that the majority were happy, and the longer they had been locked in, the happier they were. But that stems from their ability to engage with those around them regularly. Without that, Schiff fears people with conditions of consciousness face extreme isolation. “There hasn’t been a formal study of well-being in people with disorders of consciousness,” says Ralf Clauss at the Royal Surrey County Hospital, UK. “But anecdotally, from what people have told me during periods of awareness, they are happy.” ❚ -- 75 of 100 -- 74 | New Scientist Essential Guide | Consciousness WHAT HAPPENS TO CONSCIOUSNESS WHEN WE DIE? The short answer comes as no surprise: we don’t know. N 15 April 1987, Michelle Francl- Donnay’s husband Tom was due to pick her up from an evening meeting, but decided to take a swim first. He had an undiagnosed heart condition, and while in the pool had a catastrophic aneurysm. Michelle rode with him in the ambulance. That was the last time she spoke to him. “When I saw Tom’s body the next morning, he clearly wasn’t there anymore,” says Francl-Donnay, a chemist at Bryn Mawr College in Pennsylvania and an adjunct scholar at the Vatican Observatory who writes extensively on both science and spirituality. Over the years, she found herself mulling a question humans have asked for a long time: where had he gone? Even those of us who rationally reject the idea of an afterlife have trouble letting go of the idea. That might be down to our theory of mind. Because we habitually put ourselves in other people’s shoes and imagine their thoughts and feelings, it can be hard to believe that those thoughts and feelings can just cease to be when ours still feel so real. ←- Turn back to page 42 for more on metacognition- Yet we have no evidence for anything different. When you die, blood stops flowing, the muscles cool, consciousness slips away – and your physical body begins to return to the atoms that made it. But as to whether this is really the last word on you – well, no one truly knows. The integrated information theory of consciousness, for example, suggests it emerges because of the way particular physical systems organise information. Some researchers think life itself is a similar emergent property embodied in a simple equation: life = matter + information. It is a cast-iron rule of physics that information cannot be destroyed. So might physics provide a back door for some form of afterlife in which information associated with you can live on? Francl-Donnay reckons quantum physics provides teasing hints, in the way that the quantum wave functions defining our individual atoms and particles don’t have a well- defined boundary in space or time. “At some long distance, there is still some incredibly tiny chance of finding an electron there,” says Francl-Donnay. “It’s not measurable. But that doesn’t mean it’s not important.” The suggestion that some form of consciousness survives death goes way beyond what science can currently tell us. But we continue to exist in the minds of those who outlive us, of course. “Even today there’s a sense in which Tom persists – in my memory,” says Francl-Donnay. “And I can hear his voice if I shut my eyes.” The last resting place of our self that we can be sure of is in the minds of those we leave behind. ❚ -- 76 of 100 -- Chapter 5 | Altered consciousness | 75 PERSPECTIVE DANIEL BOR PROFILE DANIEL BOR “CONSCIOUSNESS IS ABOUT COMBINING INFORMATION” Different lines of evidence point to the origins of consciousness lying in how the brain deals with the data it receives, giving hope for cracking its mysteries. HE first time I saw my father in hospital after his stroke, I was disturbed to find that my strong and confident dad had been replaced by someone confused and childlike. Besides being concerned about whether or not he would recover, I was struck by the profound metaphysical implications of what had just happened. At the time, I was a few weeks away from my final university exams in philosophy and neuroscience, both of which addressed consciousness. In my philosophy lectures, I had heard elegant arguments that consciousness isn’t a physical phenomenon and must be somehow independent of our material, corporeal brains. This idea, most famously articulated by René Descartes as dualism nearly 400 years ago, seemed in stark contrast to the neuroscientific evidence in front of me: my father’s consciousness had been maimed by a small blood clot in his brain. Soon after, I abandoned plans for a PhD in the philosophy of the mind, opting for one on the neuroscience of consciousness instead. There are certainly questions about our minds that seem more in the realms of philosophy. What is it like to be a bat? Is your experience of seeing the colour red the same as mine? In fact, how do we know for certain that other people are conscious at all? But I would argue that it is neuroscience, not philosophy, that has the best chance Daniel Bor is a neuroscientist and psychologist at the University of Cambridge, UK > -- 77 of 100 -- 76 | New Scientist Essential Guide | Consciousness PERSPECTIVE DANIEL BOR of answering even these most difficult questions. One area in which we have made great progress is in discovering the physical or neural correlates of consciousness – what consciousness in the brain “looks like”, you might say. One way to investigate this question is to see what changes when consciousness is reduced or absent, as happens when people are in a vegetative state, with no sign of awareness. Brain scans show that such people usually have damage to the thalamus, a relay centre located smack bang in the middle of the brain (see diagram, right). Another common finding is damage to the connections between the thalamus and the prefrontal cortex, a region at the front of the brain, generally responsible for high-level complex thought. The prefrontal cortex has also been implicated using another technique – scanning the brain while people lose consciousness under general anaesthesia. As awareness fades, a discrete set of regions are deactivated, with the lateral prefrontal cortex the most notable absentee. Those kinds of investigations have been invaluable for narrowing down the search for the parts of the brain involved in us being awake and aware, but they still don’t tell us what happens in the brain when we see the colour red, for example. Simply getting someone to lie in a brain scanner while they stare at something red won’t work, because we know that there is lots of unconscious brain activity caused by visual stimuli – indeed, any sensory stimuli. How can we get round this problem? One solution is to use stimuli that are just at the threshold of awareness, so they are only sometimes perceived – playing a faint burst of noise, for instance, or flashing a word on a screen almost too briefly to be noticed. If the person doesn’t consciously notice the word flashing up, the only part of the brain that is activated is that which is directly connected to the sense organs concerned – in this case, the visual cortex. But if the subject becomes aware of the words or sounds, other areas kick into action. These are the lateral prefrontal cortex and the posterior parietal cortex, another region heavily involved in complex, high-level thought, this time at the top of the brain, to the rear. Satisfyingly, while many animals have a thalamus, the two cortical brain areas implicated in consciousness are nothing like as large and well developed in other species as they are in humans. This fits with the common intuition that, while there may be a spectrum of consciousness across the animal kingdom, there is something very special about our own form of it. In humans, the three brain areas implicated in consciousness the thalamus, lateral prefrontal cortex and posterior parietal cortex – share a distinctive feature: they have more connections to each other and to elsewhere in the brain than any other region. With such dense connections, these three areas are best placed to receive, combine and analyse information from the rest of the brain. Many neuroscientists suspect that it is this drawing together of information that is a hallmark of consciousness. When I talk to a friend in the pub, for instance, I don’t experience him as a series of disjointed features, but as a unified whole, combining his appearance with the sound of his voice and my knowledge of his name, favourite beer and so on – all amalgamated into a single person-object. How does the brain knit together all these disparate strands of information from a variety of brain locations? The leading hypothesis is that the relevant neurons start firing in synchrony many times a second, a phenomenon we can see as brainwaves on an electroencephalogram (EEG), whereby electrodes are placed on the scalp. The signature of consciousness seems to be an ultra-fast form of these brainwaves originating in the thalamus and spreading across the cortex. One of the most prominent attempts to turn this experimental data into a theory of consciousness is the -- 78 of 100 -- Chapter 5 | Altered consciousness | 77 global neuronal workspace model. This suggests that input from our eyes, ears and so on is first processed unconsciously, primarily in sensory brain regions. It emerges into our conscious awareness only if it ignites activity in the prefrontal and parietal cortices, with these regions connecting through ultra-fast brainwaves. This model links consciousness with difficult tasks, which often require a drawing together of multiple strands of knowledge. This view fits nicely with the fact that there is high activity in our lateral prefrontal and posterior parietal cortices when we carry out new or complex tasks, while activity in these areas dips when we do repetitive tasks on autopilot, like driving a familiar route. The main rival to the global workspace as a theory of consciousness is integrated information theory, which says consciousness is simply combining data together so that it is more than the sum of its parts. This idea is said to explain why my experience of meeting a friend in the pub, with all senses and knowledge about him wrapped together, feels so much more than the raw sensory information that makes it up. But the model could be applied equally well to the internet as to a human: its creators make the audacious claim that we should be able to calculate how conscious any particular information-processing network is, be it in the brain of a human, rat or computer. All we need to know is the network’s structure, in particular how many nodes it contains and how they are connected together. Unfortunately, the maths involves so many fiendish calculations, which grow exponentially as the number of nodes increases, that our most advanced supercomputers couldn’t perform them in a realistic time frame for even a simple nematode worm with about 300 neurons. The sums may well be simplified in future, however, to make them more practical. This mathematical theory may seem very different from the global neuronal workspace – it ignores the brain’s anatomy, for a start – yet encouragingly, both models say consciousness is about combining information, and both focus on the most densely connected parts of the information-processing network. I feel this common ground reflects the significant progress the field is making. We may not yet have solved the so-called hard problem of consciousness – how a bunch of neurons can generate the experience of seeing the colour red. Yet to me, worrying about the hard problem is just another version of dualism, seeing consciousness as something that is so mysterious it can’t be explained by studying the brain scientifically. Every time in history we thought there had to be some supernatural cause for a mysterious phenomenon, such as mental illness or even the rising of bread dough, we eventually found the scientific explanation. It seems plausible to me that if we continue to chip away at the “easy problems”, we will eventually find there is no hard problem left at all. ❚ THALAMUS (internal) LATERAL PREFRONTAL CORTEX Brain scanning reveals that certain areas of the brain have a pivotal role in generating conscious experience POSTERIOR PARIETAL CORTEX -- 79 of 100 -- 78 | New Scientist Essential Guide | Consciousness C H A P T E R 6 78 | New Scientist Essential Guide | Consciousness -- 80 of 100 -- Chapter 6 | Consciousness and reality | 79 Consciousness is all we have, but what is its place in the world? The relationship between our internal world and the external one is another of the great mysteries of consciousness with as yet few answers. It is a conundrum with two sides. The first, already touched on, is how the physical processes that we understand to underlie the workings of reality contrive to make conscious experience. The second is the role consciousness itself plays in constructing reality – which is where matters become very murky indeed. Chapter 6 | Consciousness and reality | 79 -- 81 of 100 -- 80 | New Scientist Essential Guide | Consciousness HIMS, memories, hopes, judgements, morals, qualms – all coming together to influence decisions. It is sometimes hard for us to understand how we reach the decisions we do. For fundamental physicists, it is a complete mystery. Our decision-making ability, rooted in our conscious experience of the world, is a not-so-secret superpower to alter the physical world, changing its evolution apparently at will. That is something no physical law yet devised can explain, and it leads to a question at the sharp end of considerations of the relationship between consciousness and the external world. “We act, we decide, we initiate actions,” says Carlo Rovelli at Aix- Marseille University in France. “How can we insert this agency into the general picture of nature?” Agency seems to exist on a similar sort of spectrum as consciousness. We wouldn’t be inclined to ascribe conscious experience to an apple, say, and an apple doesn’t decide when it falls from a tree. If we climb a tree, however, we can make a conscious decision to jump down. Things get messy in the middle, though – is a slime mould using chemotaxis to move towards a food source displaying agency, for example? Most people think not. “Agency is not just reflexes,” PABLO HURTADO DE MENDOZA PREVIOUS PAGE: LUMEZIA/ISTOCK > THE PHYSICS OF CONSCIOUSNESS To what extent can physical laws explain the workings of consciousness? Attempts to answer that question come to a head in one of the most mysterious abilities of conscious minds – to apparently use our subjective experience to change the world around us. -- 82 of 100 -- Chapter 6 | Consciousness and reality | 81 Chapter 6 | Consciousness and reality | 81 -- 83 of 100 -- 82 | New Scientist Essential Guide | Consciousness says Larissa Albantakis at the Center for Sleep and Consciousness at the University of Wisconsin- Madison. “If you’re only reacting to the environment, you’re not an agent, you’re just a system going through the motions.” The apparently deliberative quality of our agency sets it apart from bacteria responding to chemical stimuli, or even frogs reflexively snapping at passing flies. “We collect influences from our past, we subject those influences to reflective process, we somehow extract things like hope and dreams and bring them to bear on behaviour, to mediate between the influences impinging on us,” says philosopher Jenann Ismael at Columbia University in New York. Our current physical laws don’t try to explain how this can come about. “We think of ourselves as coming from outside the causal order and somehow intervening in it, making things happen,” says Ismael. The godlike status we accord ourselves as conscious beings is highly suspicious to many physicists. “If I’m saying that something doesn’t boil down to the laws of physics, then I’m basically positing something supernatural, that’s outside natural laws,” says physicist Matt Leifer at Chapman University in California. This has been a popular way out for natural philosophers over the years, in various forms of mind- body dualism: the idea that the mental and physical realms are separate, and the rules of one don’t apply to the other. But that hardly seems a tenable position within modern science. “Being a full-on dualist is quite hard because it does look like, for instance, when I put lots of serotonin in your brain, your mental states change,” says Knox. “The question is how you think that could work if you think there’s two kinds of separate stuff.” “If there’s evidence we should carve out a different realm for organic things or people or whatever, then by all means,” says physicist Sean Carroll at the California Institute of Technology. “But I’m made of atoms, my laws of physics purport to explain atoms, and it would seem by far the most likely hypothesis that the laws of physics explain me.” The central conundrum becomes what sort of physical laws can unify two very different, conflicting views. “We see agents that make choices and exert a causal influence on what happens in the world, and then science comes along and says, ‘you’re actually a bunch of particles or atoms and you’re just obeying differential equations’,” says Carroll. “What we want to figure out is how those things can both be true at the same time.” For Carroll and many others, the answer lies not in mysticism, but in emergence. This is the idea that behaviours and properties that are inscrutable when you look at single components of a complex system pop into existence when you view things as a whole. There are plenty of precedents. The temperature or density of a gas, for example, doesn’t mean much at the level of single molecules. Look at all the molecules of the gas together, however, and they are measurable -- 84 of 100 -- Chapter 6 | Consciousness and reality | 83 quantities that explain physical change: how temperature differences cause heat flows, for example, or how a gas pushes a piston when compressed. The catch remains the phenomenal complexity of our brains. “It’s one thing to say I can explain the temperature and density of the air by hypothesising that it is made of molecules bumping into one another,” says Carroll. “It seems quite a more dramatic project to say I can explain mind and choices and consciousness as emerging out of atoms and molecules bumping into one another.” But just as we don’t need to know how every molecule in a gas is moving to know its temperature, so agency might be understood by skating over its interior details and finding global quantities that correspond to measurable outcomes. There is still a lot of groundwork to be laid if we are to achieve that. “How do you even translate concepts like ‘make a decision’ or ‘choice’ or ’cause something to happen’ into the language of statistical mechanics where you have things bumping into each other and probability distributions and stuff like that?” asks Carroll. Such progress that has been made so far revolves around the still-nebulous concept of “information” as a physical thing, with the way conscious brains manipulate it being seen as a key. That is the starting point, for example, of mathematical theories of consciousness, such as integrated information theory (IIT). Some doubt whether physics-based theories have the chops at all, however. “I don’t believe that physics is necessarily as fundamental as most of us have been led to believe,” says Leifer. Physics has been so successful, he thinks, precisely because it has extracted the easy stuff – the bits of the world amenable to characterisation by regular, mathematical laws – and put it in a box marked “physics”. But that doesn’t mean everything fits in there. Take an old chestnut that often comes up in discussions of conscious perceptions: colour. “Physicists have a definition of red: light of such and such a wavelength,” says Leifer. But they miss out the most essential aspect of a thing’s redness – how red we perceive it to be – purely because we have no way of coming up with a common standard. The question is what reason we have to think that physics has an answer. That might represent a return to new, more subtle dualist ways of thinking. Others think answers might lie in some new understanding of how quantum effects play out in our brains, or even more speculatively in the interplay of quantum theory and gravity, or other physics we haven’t even invented yet. “Is it just a matter of building the bridges between different layers of scientific description, or understanding an entirely new phenomenon?” asks Carroll. “I think it’s the first answer, but I’m admitting there’s a question there.” ❚ “One question is why we should expect physics to explain consciousness” -- 85 of 100 -- 84 | New Scientist Essential Guide | Consciousness DOES CONSCIOUSNESS CREATE REALITY? Because our conscious experience seems related to and part of an external physical world, our natural take is that our consciousness is a product of it. We might have got things precisely the wrong way round. OES reality exist without us? Albert Einstein appeared to be in no doubt: surely the moon doesn’t vanish when we aren’t looking, he once asked incredulously. He had been provoked by the proposition that things only become real when we observe them. That suggestion emerges from the best-tested theory of material reality that we have ever had: quantum theory. When it comes to forecasting how the world will behave, quantum theory is unsurpassed. Its every prediction, no matter how counter-intuitive, is borne out by experiment. Electrons, for instance, can sometimes display behaviour characteristic of waves, even though they seem in other circumstances to behave like particles. Before observation, such quantum objects are said to be in a superposition of all possible observable outcomes. This doesn’t mean they exist in many states at once, rather that we can only say that all the allowed outcomes of measurement remain possible. This potential is represented in the quantum wave function, a mathematical expression that encodes all outcomes and their relative probabilities. But it isn’t at all obvious what, if anything, the wave function can tell you about the nature of a quantum system before we make a measurement. That act reduces all those possible outcomes to one, dubbed the collapse of the wave function – but no one really knows what that means either. Some researchers think it might be a real physical process, like radioactive decay. Those who subscribe to the many-worlds interpretation think it is an illusion conjured by a splitting of the universe into each of the possible outcomes. Others still say that there is no point in trying to explain it – and besides, who cares? The maths works, so just shut up and calculate. Whatever the case, wave function collapse seems to hinge on intervention or observation, throwing up some huge problems, not least about the role of consciousness in the whole process. This is the measurement problem, arguably the biggest headache in quantum theory. “It is very hard,” says Kelvin McQueen, a philosopher at Chapman University in California. “More interpretations are being thrown up every day, but all of them have problems.” The most popular is known as the Copenhagen interpretation after the home city of one of quantum theory’s pioneers, Niels Bohr. He argued that quantum mechanics tells us only what we should expect when we make a measurement, not what causes that outcome. The theory can’t tell us what a quantum system is like before we observe it; all we can ever ask of it is the probabilities of different possible outcomes. Such a perspective seems to back you into an uncomfortable corner: that the act of our observation calls the outcome into being. Can that be true? It seems the antithesis of what science normally assumes, as Einstein intimated. Yet the idea has some pedigree. Hungarian physicist John von Neumann was the first to entertain it in the early 1930s, and his compatriot Eugene Wigner went deepest with a thought experiment in the 1950s now known as Wigner’s friend. -- 86 of 100 -- Chapter 6 | Consciousness and reality | 85 Suppose that Wigner is standing outside a windowless room where his friend is about to make some measurement on a particle. Once that is done, she knows what the observed property of the particle is, but Wigner doesn’t. He can’t meaningfully say that the particle’s wave function has collapsed until his friend tells him the result. Worse still, until she does, quantum theory offers no way for Wigner to think about all the unseen events inside the lab as having fixed outcomes. His friend, her measuring apparatus and the particle remain one big composite superposition. It is as if we live in a solipsistic world where collapse only occurs when knowledge of the result impinges on a conscious mind. “It follows that the quantum description of objects is influenced by impressions entering my consciousness,” Wigner wrote. “Solipsism may be logically consistent with present quantum mechanics.” John Wheeler at Princeton University put it differently: it isn’t solipsism, but a kind of interactive collaboration that brings things into being. We live, said Wheeler, in a “participatory universe” – one that can’t be meaningfully described without invoking our active involvement. “Nothing is more astonishing about quantum mechanics,” he wrote, “than its allowing one to consider seriously… that the universe would be nothing without observership.” But Wheeler couldn’t escape the thicket of irresolvable questions that the participatory universe raises. For one, Wigner and his friend seem locked in an infinite regress. Is Wigner himself in a superposition Albert Einstein queried whether the moon really ceases to exist when we aren’t looking at it > WEERACHONOAT/ISTOCK -- 87 of 100 -- 86 | New Scientist Essential Guide | Consciousness of states until he passes on the result to his other friends in the next building? Which observer “decides” when wave function collapse occurs? And what constitutes a conscious observation anyway? Despite the persistence of such questions, some theorists have recently returned to a form of Wheeler’s vision, what Chris Fuchs at the University of Massachusetts in Boston has called “participatory reality”. That shift is partly for want of a better alternative, but primarily it is because if you take quantum mechanics seriously, some element of observer-dependent subjectivity seems impossible to avoid. A couple of years ago, theoretical physicist Caslav Brukner at the University of Vienna revisited the Wigner’s friend scenario in a slightly altered form proposed by David Deutsch at the University of Oxford. Here, the friend makes the measurement – she has collapsed the particle’s wave function, producing either outcome A or B – but tells Wigner only that she sees a definite result, not what it is. In Deutsch’s scenario, Wigner is forced to conclude that his friend, her measuring apparatus and the particle are in a joint superposition, even though he knows a measurement has happened. To Wigner’s friend, she is definitely in, say, the state “I see A”, but to Wigner, she is in a superposition of “I see A” and “I see B”. So who is right? They both are, says Brukner, depending on whose point of view you adopt. He has shown that if quantum mechanics is correct, there is no privileged perspective from which a third observer can reconcile both Wigner’s and his friend’s statements. “There is no reason to assume that the ‘facts’ of one of them are more fundamental than those of the other,” says Brukner – and so we are forced to conclude that “there are no ‘facts of the world per se’ ”. Rather, there are only facts for each observer. One interpretation of quantum mechanics takes such a conclusion in its stride. Devised in the 2000s by Fuchs and others, quantum Bayesianism (also known as QBism) is rooted in the view that quantum mechanics supplies only recommendations about what a rational observer should believe they will see on making a measurement – and that these beliefs can be updated as the observer takes fresh experiences into account. That is where the “Bayesianism” comes in: it refers to the classical theory of probability, initiated in the 18th century, that assigns probabilities on the basis of what the observer already knows to be the case. QBism point-blank denies that there is any objective notion of a quantum state at all. This doesn’t mean there can be nothing “real” beyond personal belief, only that quantum mechanics doesn’t speak directly to that issue. The existence of Brukner’s “alternative facts” causes no pain in such a picture, because it has assumed them all along. Nor, indeed, does wave function collapse, which is then just a way of talking about how measurement updates our knowledge. But few physicists are prepared to accept such stringent limits on their efforts to describe reality, which is why QBism remains a minority sport. The response of Markus Müller, a theorist at the Institute for Quantum Optics and Quantum Information in Vienna, is to take things up a notch. “QBism is not extreme enough,” he says. “It assumes that there is this one external world out there which is “Quantum theory could imply that nothing would happen without our involvement” -- 88 of 100 -- Chapter 6 | Consciousness and reality | 87 ultimately responsible for our experiences.” His approach involves imagining that there are no fundamental laws of nature – no general relativity, Maxwell’s equations or Heisenberg’s uncertainty principle – and asking what the world would then look like. Müller stripped away the physics and used a field of maths called algorithmic information theory, which uses inductive logic to ask, given that you experience X – you make an observation of the world and see the outcome X – what are the chances you will then experience another outcome, Y? The idea, says theorist Giulio Chiribella at the University of Hong Kong, “is to think of our experience as a movie made of many frames and to ask the question, given the frames I have seen so far, what frame will I see next?” The remarkable answer is that, even without any underlying laws, as random experiences stack up, the conditional probability of the next experience, as described by a string of bits, tends to be higher for simpler bit sequences than for complex ones. This makes it look as if there is a fairly simple algorithm generating the bit strings. So the observer deduces a simple “model” of reality, characterised by regular and comprehensible laws that smoothly connect one experience to the next. This seems deeply odd: how can randomness give rise to this apparently law-bound behaviour? It is a little like the way we understand a gas. Although, in principle, all possible configurations of its molecules are allowed, the probability distribution of particle speeds we see has a simple bell-shaped curve, and the particles are distributed in space with bland uniformity. Out of that come simple laws relating to things we can easily measure: pressure, temperature and volume. Those laws aren’t written into the gas particles themselves; they are an emergent property of the probabilities of different configurations. “The remarkable thing is that a notion of an objective external world emerges automatically in the long run,” says Müller. What’s more, “different observers will tend to agree on properties of that external world”, he says. That is because, according to algorithmic information theory, the probabilities of bit strings for different observers will tend to converge on the same distribution – so they will agree on what the “laws of the world” are. “Overall, the ‘movie’ is likely to be simple and different observers can generally agree on some aspects of the plot,” says Chiribella. The surprises don’t stop there. This emergent reality should have just the qualities we see in quantum physics, where objects can show wave-like properties and behave in “non-local” ways, when a measurement on one particle can seem instantaneously to influence the state of another separated in space. The upshot is that from the most minimal assumptions about the probabilities of what our personal experiences will contain, you can recover a world like the one we know. “The world could still look something like how we experience it, even though in truth it would be mind-bogglingly different,” says Müller. It isn’t easy to see how Müller’s ideas can be tested. But circumstantial evidence that he could be on the right track comes with the way they solve a long- standing metaphysical conundrum. In the late 19th century, Austrian physicist Ludwig Boltzmann described the world as space filled with particles in random motion, adopting all manner of different configurations. Experiments have long confirmed that our reality matches this vision, but there is a problem. If you examine the probabilities of each configuration, it turns out we are much less likely to be sentient beings who evolved on a planet over billions of years than ephemeral lone “brains”, condensed out of chaos by sheer chance and floating freely, complete with imagined memories and experiences. How can we know we aren’t these “Boltzmann brains”, apt to dissolve back into the fluctuating cosmos at any moment? If objective reality emerges from the mathematically predictable way our past experiences determine future observations, then sudden discontinuities in experience of the sort Boltzmann brains would encounter will be vanishingly improbable. Experience should be smooth, connected and, at our scale, rather predictable. All the same, this image of the universe built directly from conscious experiences is so “out there” that other researchers barely know what to make of it. Yet few would dismiss it out of hand. Even Einstein kept an open mind. “It is basic for physics that one assumes a real world existing independently from any act of perception,” he wrote in a letter shortly before he died in 1955. “But this we do not know.” ❚ -- 89 of 100 -- IS THE UNIVERSE CONSCIOUS? Attempts to encapsulate the problem of consciousness mathematically lead down some very strange alleyways – most controversially, suggesting that some form of consciousness might be a universal property of matter. -- 90 of 100 -- Chapter 6 | Consciousness and reality | 89 HE unique difficulty of the hard problem of consciousness stems from the inherently subjective nature of felt experience. Whatever it is, you might think, it isn’t something you can prod and measure – not a natural fit for our mathematically based models of physical phenomena. Then again, mathematics has a track record with hard problems. Physicist Eugene Wigner coined the phrase the “unreasonable effectiveness of mathematics” in the 1960s to encapsulate the curious fact that merely by manipulating numbers, we can describe and predict all manner of natural phenomena with astonishing clarity, from the movements of planets and the strange behaviour of fundamental particles to the consequences of a collision between two black holes billions of light years away. That success is down to the ability of mathematics to translate concepts into formal, logical statements that can draw out insights that wouldn’t be exposed from just talking about things in messy human language. “This might help us to quantify experiences like the smell of coffee in ways that we can’t if we rely on plain English,” says Johannes Kleiner, a mathematician at the Munich Centre for Mathematical Philosophy in Germany. This is why Kleiner and Sean Tull, a mathematician at the University of Oxford, have begun formalising the mathematics behind arguably the only theory of consciousness with a halfway-thought-through mathematical underpinning. Integrated information theory (IIT) holds that a system’s consciousness arises from the way information moves between its subsystems. ←- Turn back to page 14 for the basis of IIT- One way to think of these subsystems is as islands, each with their own population of neurons. The islands are connected by traffic flows of information. For consciousness to appear, so the idea goes, this information flow must be complex enough to make the islands interdependent. Changing the flow of information from one island should affect the state and output of another. In principle, this lets you put a number on the degree of consciousness: you could quantify it by measuring how much an island’s output relies on information flowing from other islands. This gives a sense of how well a system integrates information, a value called “phi”. If there is no dependence on a traffic flow between the islands, phi is zero and there is no consciousness. But if strangling or cutting off the connection makes a difference to the amount of information it integrates and outputs, then the phi of that group is above zero. The higher the phi, the more consciousness a system will display. Another key feature of IIT, known as the exclusion postulate, says that a group will explicitly display consciousness only when its phi is “maximal”. That is to say, its own degree of consciousness has to be bigger than the degree of consciousness you can ascribe to any of its individual parts, and simultaneously bigger > AGSANDREW/ISTOCK -- 91 of 100 -- 90 | New Scientist Essential Guide | Consciousness than the degree of consciousness of any system of which it is a part. Any and all parts of the human brain might have a micro-consciousness, for example. But when one part has an increase in consciousness, such as when a person is brought out of anaesthesia, the micro-consciousnesses are lost. In IIT, only the system with the largest phi displays the consciousness we register as experience. The idea has won adherents since Giulio Tononi, a neuroscientist at the University of Wisconsin, first came up with it. “Theoretically, it’s quite appealing,” says Daniel Bor at the University of Cambridge. “We have this association between consciousness and intelligence: creatures able to recognise themselves in the mirror also seem to be the most intelligent. So some connection between consciousness and intelligence seems reasonable.” And intelligence has a link to gathering and processing information. “That means you may as well make the related connection that, in some way, consciousness is related to information processing and integration,” says Bor. It also makes sense given what we know about consciousness in the human brain. It is compromised, for example, if there is damage to the cerebral cortex. This region has a relatively small number of highly interconnected neurons, and would have a large phi in IIT. The cerebellum, on the other hand, has a much higher number of neurons, but they are relatively unconnected. IIT would predict that damage to the cerebellum might have little effect on conscious experience, which is exactly what studies show. IIT is less convincing when it comes to some details, though. Phi should decrease when you go to sleep or are sedated via a general anaesthetic, for instance, but Pedro Mediano, now part of Bor’s lab at the University of Cambridge, and his colleagues have shown that it doesn’t. “It either goes up or stays the same,” says Bor. And explaining why information flow gives rise to an experience, such as the smell of coffee, is problematic. IIT frames conscious experience as the result of “conceptual structures” that are shaped by the arrangement of parts of the relevant network, but many find the explanation convoluted and unsatisfying. Philosopher John Searle is one of IIT’s detractors. He has argued that it ignores the question of why and how consciousness arises in favour of making the questionable assumption that it is simply a by- product of the existence of information. For that reason, he says, IIT “does not seem to be a serious scientific proposal”. Perhaps the most troubling critiques of IIT as a mathematical theory concern a lack of clarity about the underlying numbers. When it comes to actually calculating a value for phi for the entirety of a system as complex as a brain, IIT gives a recipe that is almost impossible to follow – something even Tononi admits. “As it’s currently given, phi is very difficult to calculate for a whole brain,” says Tull. That is an understatement. Using the current method, calculating phi for the 86 billion neurons of the human brain would take longer than the age of the universe. Bor has worked out that just calculating it for the 302-neuron brain of a nematode worm would take 5 × 1079 years on a standard PC. And when you calculate phi for things you wouldn’t -- 92 of 100 -- Chapter 6 | Consciousness and reality | 91 expect to be conscious, you get all sorts of strange results. Scott Aaronson, a theoretical physicist at the University of Texas at Austin, for example, was initially excited by the theory, which he describes as “a serious, honourable attempt” to figure out how to get common sense answers to the question of which physical systems are conscious. But then he set to testing it. Aaronson took the principles of IIT and used them to compute phi for a mathematical object called a Vandermonde matrix. This is a grid of numbers whose values are interrelated, and can be used to build a grid- like circuit, known as a Reed-Solomon decoding circuit, to correct errors in the information that is read off CDs and DVDs. What he found was that a sufficiently large Reed-Solomon circuit would have an enormous phi. Scaled to a large enough size, one of these circuits would end up being far more conscious than a human. The same problem exists in other arrangements of information processing routines, Aaronson pointed out: you can have integrated information, with a high phi value, that doesn’t lead to anything we would recognise as consciousness. He concluded that IIT unavoidably predicts vast amounts of consciousness in physical systems that no sensible person would regard as particularly ‘conscious’ at all. Aaronson walked away, but not everyone sees highly conscious grid-shaped circuits as a deal-breaker. For Kleiner, it is simply a consequence of the nature of the beast: we lack information because any analysis of consciousness relies on self-reporting and intuition. “We can’t get reports from grids,” he says. “This is the problem.” Rather than abandoning a promising model, he thinks we need to clarify and simplify the mathematics underlying it. That is why he and Tull set about trying to identify the necessary mathematical ingredients of IIT, splitting them into three parts. First is the set of physical systems that encode the information. Next is the various manifestations or “spaces” of conscious experience. Finally, there are basic building blocks that relate these two: the “repertoires” of cause and effect. In 2020, they demonstrated how these ingredients can be joined in a way that provides a logically consistent way of applying the IIT algorithm for finding phi. “Now the fundamental idea is well-defined enough to make the technical problems go away,” says Kleiner. Their aspiration is that mathematicians will now be able to create improved models of consciousness based on the premises of IIT – or, even better, competitor theories. “We would be glad to contribute to the further development of IIT, but we also hope to help improve and unite various existing models,” says Kleiner. “Eventually, we may come to propose new ones.” One consequence of this stimulus might be a reckoning for the notion, raised by IIT’s application to grid-shaped circuits, that inanimate matter can be conscious. Such a claim is typically dismissed out of hand, because it appears to be tantamount to “panpsychism”, the idea that consciousness is a fundamental property of all matter. This isn’t to say that fundamental particles have feelings. But panpsychists do argue that they may have some semblance of consciousness, however fragmentary, that could combine to generate the various levels of consciousness experienced by birds or chimps or us. “Particles or other basic physical entities might Attempts to quantify consciousness suggest even some electrical circuits could have it > BET_NOIRE/ISTOCK -- 93 of 100 -- 92 | New Scientist Essential Guide | Consciousness have simple forms of consciousness that are fundamental, but complex human and animal consciousness would be constituted by or emergent from this,” says Hedda Hassel Mørch at Inland Norway University of Applied Sciences in Lillehammer. The idea that electrons could have some form of consciousness might be hard to swallow, but panpsychists argue that it provides the only plausible approach to solving the hard problem. They reason that, rather than trying to account for consciousness in terms of non-conscious elements, we should instead ask how rudimentary forms of consciousness might come together to give rise to the complex experiences we have. With that in mind, Mørch thinks IIT is at least a good place to start. Its general approach, analysing our first-person perspective in terms of what we perceive when certain brain regions become active and using that to develop constraints on what its physical correlate could be, is “probably correct”, she says. And although IIT as currently formulated doesn’t strictly say everything is conscious – because consciousness arises in networks rather than individual components – it is entirely possible that a refined version could. “I think that the core ideas underlying IIT are fully compatible with panpsychism,” says Kleiner. That might also fit in with indications from elsewhere that the relationship between our consciousness and the universe might not be as straightforward as we imagine. Take the quantum measurement problem. Quantum theory, our description of the basic interactions of matter, says that before we measure a quantum object, it can have many different values, encapsulated in a mathematical entity called the wave function. So what collapses the many possibilities into something definite and “real”? One viewpoint is that our consciousness does it, which would mean we live in what physicist John Wheeler called a “participatory universe”. There are many problems with this idea, not least the question of what did the collapsing before conscious minds evolved. A viable mathematical model of consciousness that allows for it to be a property of matter would at least provide a solution for that. Then there is University of Oxford mathematician Roger Penrose’s suggestion that our consciousness is actually “the reason the universe is here”. It is based on a hunch about quantum theory’s shortcomings. But if there is any substance to this idea, the framework of IIT – and its exclusion postulate in particular – suggests that information flow between the various scales of the universe’s contents could create different kinds of consciousness that ebb and flow depending on what exists at any particular time. The evolution of our consciousness might have, in IIT’s terms, “excluded” the consciousness of the universe. Or perhaps not. There are good reasons to remain sceptical about the power of maths to explain consciousness, never mind the knock-on effects for our understanding of physics. We seem to be dealing with something so involved that calculations may not even be possible, according to Phil Maguire, a computer scientist at Maynooth University in Ireland. “Breaking down cognitive processes is so complex that it is not feasible,” he says. Others express related doubts as to whether maths is up to the job, even in principle. “I think mathematics can help us understand the neural basis of consciousness in the brain, and perhaps even machine consciousness, but it will inevitably leave something out: the felt inner quality of experience,” says Susan Schneider, a philosopher and cognitive scientist at the University of Connecticut. Philip Goff, a philosopher at Durham University, UK, and a vocal advocate for panpsychism, has a similar view. Consciousness deals with physical phenomena in terms of their perceived qualities, he points out – the smell of coffee or the taste of mint, for example – which aren’t conveyable in a purely quantitative objective framework. “In dealing with consciousness, we need more than the standard scientific tools of public observation and mathematics,” says Goff. But Kleiner isn’t put off. He is developing a mathematical model that can incorporate ineffable, private experiences. It is currently undergoing peer review. And even if it doesn’t work, he says, something else will: “I’m fully convinced that in combination with experiments and philosophy, maths can help us proceed much further in uncovering the mystery of consciousness.” ❚ -- 94 of 100 -- Chapter 6 | Consciousness and reality | 93 PERSPECTIVE ANIL SETH PROFILE ANIL SETH “WE NEED TO SOLVE THE REAL PROBLEM OF CONSCIOUSNESS” The best way to make progress on the nature of consciousness might be to break it down into its constituent parts. HE subjective nature of consciousness makes it difficult even to define. The closest we have to a consensus is that there is “something it is like to be conscious”. There is something it is like to be me or you, and probably something it is like to be a dolphin or a mouse. But there is – presumably – nothing it is like to be a bacterium or a toy robot. The challenge is to understand how and why this can be true. How do conscious experiences relate to the cells and molecules and atoms inside brains and bodies? Why should physical matter give rise to an inner life at all? Some people fear science may not be up to the task. They point out that you can’t precisely control or observe felt experiences. Some even question the idea that physical mechanisms can ever explain consciousness. I disagree. I believe that science is capable of explaining consciousness, but only if we stop treating it as a single big mystery requiring a humdinger solution. Instead, we must break it down into its various related properties and address each in turn. As we progressively explain why particular patterns of brain activity map to particular kinds of conscious experience, we will find that the deeper mystery of consciousness itself begins to fade away. The easy problem is really a series of problems. Anil Seth is professor of cognitive and computational neuroscience at the University of Sussex, UK, and author of Being You: A new science of consciousness > -- 95 of 100 -- 94 | New Scientist Essential Guide | Consciousness PERSPECTIVE ANIL SETH These involve understanding how the brain, in concert with the rest of the body, gives rise to functions like perception, cognition, learning and behaviour. These problems aren’t actually easy at all; the point is that there is no conceptual mystery, that these problems can be solved in terms of physical mechanisms, however complex and hard to discern these mechanisms may be. The hard problem, on the other hand, is the enigma of why and how any of this should be accompanied by conscious experience at all: why aren’t we just meaty robots, without an inner universe? The temptation is to think that solving the easy problems would get us nowhere at all in solving the hard problem, leaving the brain basis of consciousness a total mystery. Fortunately, there is an alternative, which I have come to call the “real problem” of consciousness: how to explain, predict and control the various properties of consciousness in terms of physical processes in the brain and body. The real problem is distinct from the hard problem, because it isn’t – at least not in the first instance – about explaining why and how consciousness is part of our universe. It is also distinct from the easy problems, because it doesn’t sweep the subjective, experiential properties under the carpet. The real problem isn’t a completely new way of thinking, but, for me, putting things in terms of explanation, prediction and control has helped to crystallise what a successful science of consciousness should look like, since these are the criteria that are applied in most other fields of science. Take, for example, the visual experience of redness. The hard problem asks why there is such an experience at all, while the easy problems encompass all the processes and outcomes associated with light of a particular wavelength entering the eye. From the perspective of the real problem, we want to know what it is about specific patterns of activity in the brain that explains (and predicts and controls) why the experience of redness is the way it is. Why isn’t it like blueness, or toothache, or jealousy? This approach has something of a pedigree. Not so long ago, biologists and chemists doubted that the property of “being alive” could ever be explained mechanistically. Nowadays, although there are still many things about life that remain unknown, the idea that being alive requires some special sauce has long been retired. The hard problem of life wasn’t so much solved as dissolved. Now, it is true that life isn’t the same thing as consciousness. Most conspicuously, the properties of life are objectively describable, whereas the properties of consciousness exist only in the first person. But this isn’t an insurmountable barrier; it mostly means the relevant information, because it is subjective, is harder to collect. Part of the strategy in dissolving the hard problem of life was to stop treating it as one big scary mystery in need of a eureka solution and instead as a collection of related properties, each addressable somewhat separately. For consciousness, there are many ways to cut the cake. One way I advocate is to distinguish between conscious level (how conscious you are, as in the difference between general anaesthesia and normal wakeful awareness), conscious content (what you are conscious of) and conscious self (the experience of “being you” or “being me”). By developing accounts that explain, predict and control these different aspects of consciousness, my belief is that a fulfilling picture of all conscious experience will come to light. Let’s focus on content and self. My strategy for explaining these properties of consciousness is based on an increasingly popular theory in cognitive neuroscience called predictive processing. The bedrock idea is simple. Imagine that you are your brain, locked inside the bony vault of the skull, trying to figure out what is out there in the world – a world that, -- 96 of 100 -- Chapter 6 | Consciousness and reality | 95 from the perspective of the brain, also includes the body. All you have to go on are noisy and ambiguous sensory signals, which are only indirectly related to what is out there, and which certainly don’t come with labels attached (“I’m from a cup of coffee! I’m from a tree!”). Perception, in this view, has to be a process of inference, of neurally implemented probabilistic guesswork. When I see a red coffee cup on the table in front of me, this is because “red coffee cup” is the brain’s best guess of the hidden, and ultimately unknowable, causes of the corresponding sensory signals. When I experience the glow of a sunset, or the sharp taste of an adventurous cheese, that, too, is a perceptual best guess. How are these perceptual best guesses arrived at? According to predictive processing, the brain is constantly calibrating its perceptual predictions using data from the senses. The predictive processing theory has it that perception involves two counterflowing streams of signals. There is an “inside-out” stream, cascading downwards through the brain’s perceptual hierarchies, that conveys predictions about the causes of sensory inputs. Then there are “outside-in” prediction errors – the sensory signals – that report the differences between what the brain expects and what it gets. By continually updating its predictions to minimise sensory prediction errors, the brain will settle and resettle on an evolving best guess of its sensory causes, and this is what we consciously perceive. Perception, in this view, isn’t a passive registration of an external reality. It is an active construction, a kind of “controlled hallucination”, in which the brain’s best guesses are tied to the world – and the body – through a continuous process of prediction error minimisation. Predictive processing isn’t a theory of consciousness, in the sense that solving the hard problem would require. Instead, at least at first, it is best thought of as a theory for consciousness science, in the real problem sense. It provides a method for building explanatory bridges between neural mechanisms and aspects of what conscious experiences are like, from the perspective of the person experiencing them. This is what my colleagues and I have been doing in my laboratory at the University of Sussex, UK. Some of our experiments are very simple – for example, finding that people consciously perceive expected images more quickly, and more accurately, than unexpected images. But the really exciting work is taking us deeper into the phenomenology – the “what-it-is-like”-ness – of conscious experiences. In one example, we are investigating the phenomenology of different varieties of visual hallucination in terms of their dependence on different kinds of perceptual prediction. Some hallucinations, such as those due to psychosis or neurodegenerative disease, can be complex, featuring rich perceptual scenes experienced as being real. Others, such as those arising from progressive visual loss, can be relatively simple and aren’t experienced as being continuous with the real world. These differences can be simulated by novel neural network architectures that deploy perceptual predictions in different ways. These neural networks serve as computational models of the brain basis of visual experiences, and we can check their output by asking people who experience hallucinations to rate what they come up with. We are now extending this approach – which we call “computational phenomenology” – to other, more fundamental aspects of perceptual experience, like the sensation of time passing and the three-dimensional structure of visual space. By progressively accounting for the deep structure of perceptual experiences – not only the specific contents they present, like a cat or a coffee cup, but how they unfold over time and space – my belief is that the apparent mystery of the hard problem is already beginning to dissolve. And this process gathers momentum when we ask who, or what, is doing > -- 97 of 100 -- 96 | New Scientist Essential Guide | Consciousness all this perceiving – and consider the experience of being a conscious self from the same “real problem” perspective. Contrary to how things might seem, selves aren’t essences-of-you that peer out through the windows of the senses from somewhere inside the skull. Instead, the self is a perception too. Experiences of “being you” are collections of brain-based best guesses, and understanding this further erodes the dualistic intuitions on which the hard problem rests. Just as consciousness has many aspects, there are also many ways we experience being a self. These can be arranged in a loose hierarchy, beginning with low- level experiences of being a physical body, through to experiences of seeing the world from a particular first- person perspective, conscious intentions to do things (what we might call experiences of free will), all the way up to experiences of being a continuous person over time within a rich social and cultural environment – a self with a name, an identity and a set of memories. I argue that each of these aspects of selfhood can be understood as a distinctive form of controlled hallucination. For now, let’s drill down to the most basic aspect of conscious selfhood: the experience of being a body. I think of this as a rudimentary feeling of simply being a living organism – partly expressed through emotions and moods, but at its deepest layers without any describable content at all. It is here that the perception of the body from within, known as interoception, comes to the fore. Interoceptive sensations tell the brain about the internal state of the body – blood pressure, say, or how the heart is doing – and therefore enable the brain to perform its most important task: keeping the body alive. Like all sensory signals, interoceptive signals are only indirectly related to their causes, and so interoception must also involve a process of best- guessing. And just as inference about the causes of visual signals underpins visual experience, my proposal is that interoceptive inferences underpin other kinds of experiences: in this case, bodily experiences, like emotions and moods. This proposal might seem nothing more than a modern gloss on some old ideas that emotion involves perception of changes in the physiological condition of the body. But there is more to it than that. Following the real problem strategy, the differences between emotional experiences and visual experiences can now be understood in terms of the different kinds of perceptual prediction at play. Visual experiences of objects are generally concerned with figuring out what is there, so it makes sense for the corresponding perceptual experiences to have the character of things with specific locations and physical extents. Emotional experiences, by contrast, are generally concerned with the organism’s physiological condition and prospects of staying alive. These experiences, and experiences of being a body more generally, don’t have shapes and locations in space. They instead have valence, which, in psychology, means things are good or bad now, or likely to be good or bad in the future – which is what it is like to feel an emotion. ❚ PERSPECTIVE ANIL SETH -- 98 of 100 -- THE SUN / EARTH AND THE MOON / THE INNER PLANETS / THE GAS GIANTS AND THEIR MOONS / THE UNKNOWN EDGE / EXOPLANETS AND LIFE / AND MORE ON SALE 21 JULY ESSENTIAL GUIDE №13 THE SOLAR SYSTEMA J O U R N E Y T H R O U G H O U R C O S M I C N E I G H B O U R H O O D – A N D B E Y O N D -- 99 of 100 -- £9.99 9 7 7 2 6 3 4 0 1 5 0 1 9 1 2 ESSENTIAL GUIDE№12 WHY DO WE HAVE CONSCIOUS EXPERIENCES AND HOW DO OUR BRAINS MAKE THEM? WHAT IS THE SELF, AND HOW DOES CONSCIOUSNESS FIT INTO THE COSMOS? CONSCIOUSNESS IS EVERYTHING WE HAVE – OUR FEELING OF BEING, AND OUR RELATIONSHIP WITH THE WORLD. BUT WHAT IT IS AND WHY IT EXISTS REMAIN FUNDAMENTAL MYSTERIES, THE SUBJECTS OF THIS 12TH NEW SCIENTIST ESSENTIAL GUIDE. TOPICS INCLUDE: ❶ Theories of consciousness ❷ Animal and human minds ❸ The self and free will ❹ Sleep, dreaming and altered consciousness ❺ Consciousness and the universe CONSCIOUSNESS -- 100 of 100 --