The Ego Tunnel: The Science of the Mind and the Myth of the Self - Thomas Metzinger (2009)
In this book, I will try to convince you that there is no such thing as a self. Contrary to what most people believe, nobody has ever been or had a self. But it is not just that the modern philosophy of mind and cognitive neuroscience together are about to shatter the myth of the self. It has now become clear that we will never solve the philosophical puzzle of consciousness—that is, how it can arise in the brain, which is a purely physical object—if we don’t come to terms with this simple proposition: that to the best of our current knowledge there is no thing, no indivisible entity, that is us, neither in the brain nor in some metaphysical realm beyond this world. So when we speak of conscious experience as a subjective phenomenon, what is the entity having these experiences?
There are other important issues in the quest to probe our inner nature—new, exciting theories about emotions, empathy, dreaming, rationality, recent discoveries about free will and the conscious control of our actions, even about machine consciousness—and they are all valuable, as the building blocks of a deeper understanding of ourselves. I will touch on many of them in this book. What we currently lack, however, is the big picture—a more general framework we can work with. The new mind sciences have generated a flood of relevant data but no model that can, at least in principle, integrate all these data. There is one central question we have to confront head on: Why is there always someone having the experience? Who is the feeler of your feelings and the dreamer of your dreams? Who is the agent doing the doing, and what is the entity thinking your thoughts? Why is your conscious reality yourconscious reality?
This is the heart of the mystery. If we want not just the building blocks but a unified whole, these are the essential questions. There is a new story, a provocative and perhaps shocking one, to be told about this mystery: It is the story of the Ego Tunnel.
The person telling you this story is a philosopher, but one who has closely cooperated with neuroscientists, cognitive scientists, and researchers in artificial intelligence for many years. Unlike many of my philosopher colleagues, I think that empirical data are often directly relevant to philosophical issues and that a considerable part of academic philosophy has ignored such data for much too long. The best philosophers in the field clearly are analytical philosophers, those in the tradition of Gottlob Frege and Ludwig Wittgenstein: In the past fifty years, the strongest contributions have come from analytical philosophers of mind. However, a second aspect has been neglected too much: phenomenology, the fine-grained and careful description of inner experience as such. In particular, altered states of consciousness (such as meditation, lucid dreaming, or out-of-body experiences) and psychiatric syndromes (such as schizophrenia or Cotard’s syndrome, in which patients may actually believe they do not exist) should not be philosophical taboo zones. Quite the contrary: If we pay more attention to the wealth and the depth of conscious experience, if we are not afraid to take consciousness seriously in all of its subtle variations and borderline cases, then we may discover exactly those conceptual insights we need for the big picture.
In the chapters that follow, I will lead you through the ongoing Consciousness Revolution. Chapters 1 and 2 introduce basic ideas of consciousness research and the inner landscape of the Ego Tunnel. Chapter 3 examines out-of-body experiences, virtual bodies, and phantom limbs. Chapter 4 deals with ownership, agency, and free will; chapter 5 with dreams and lucid dreaming; chapter 6 with empathy and mirror neurons; and chapter 7 with artificial consciousness and the possibility of postbiotic Ego Machines. All these considerations will help us to further map out the Ego Tunnel. The two final chapters address some of the consequences of these new scientific insights into the nature of the conscious mind-brain: the ethical challenges they pose and the social and cultural changes they may produce (and sooner than we think), given the naturalistic turn in the image of humankind. I close by arguing that ultimately we will need a new “ethics of consciousness.” If we arrive at a comprehensive theory of consciousness, and if we develop ever more sophisticated tools to alter the contents of subjective experience, we will have to think hard about what a good state of consciousness is. We urgently need fresh and convincing answers to questions like the following: Which states of consciousness do we want our children to have? Which states of consciousness do we want to foster, and which do we want to ban on ethical grounds? Which states of consciousness can we inflict upon animals, or upon machines? Obviously, I cannot provide definitive answers to such questions; instead, the concluding chapters are meant to draw attention to the important new discipline of neuroethics while at the same time widening our perspective.
THE PHENOMENAL SELF-MODEL
Before I introduce the Ego Tunnel, the central metaphor that will guide the discussion from here onward, it will be helpful to consider an experiment that strongly suggests the purely experiential nature of the self. In 1998, University of Pittsburgh psychiatrists Matthew Botvinick and Jonathan Cohen conducted a now-classic experiment in which healthy subjects experienced an artificial limb as part of their own body.1 The subjects observed a rubber hand lying on the desk in front of them, with their own corresponding hand concealed from their view by a screen. The visible rubber hand and the subject’s unseen hand were then synchronously stroked with a probe. The experiment is easy to replicate: After a certain time (sixty to ninety seconds, in my case), the famous rubber-hand illusion emerges. Suddenly, you experience the rubber hand as your own, and you feel the repeated strokes in this rubber hand. Moreover, you feel a full-blown “virtual arm”—that is, a connection from your shoulder to the fake hand on the table in front of you.
The most interesting feature I noticed when I underwent this experiment was the strange tingling sensation in my shoulder shortly before the onset of the illusion—shortly before, as it were, my “soul arm” or “astral limb” slipped from the invisible physical arm into the rubber hand. Of course, there is no such thing as a ghostly arm, and probably no such thing as an astral body, either. What you feel in the rubber-hand illusion is what I call the content of the phenomenal self-model (PSM)—the conscious model of the organism as a whole that is activated by the brain. (“Phenomenal” is used here, and throughout, in the philosophical sense, as pertaining to what is known purely experientially, through the way in which things subjectively appear to you.) The content of the PSM is the Ego.
Figure 1: The rubber-hand illusion. A healthy subject experiences an artificial limb as part of her own body. The subject observes a facsimile of a human hand while her own hand is concealed (gray square). Both the artificial rubber hand and the invisible hand are stroked repeatedly and synchronously with a probe. The light areas around the hand and the dark areas in the index finger indicate the respective tactile and visual receptive fields for neurons in the premotor cortex. The illustration on the right shows the subject’s illusion as the felt strokes are aligned with the seen strokes of the probe (the dark areas show areas of heightened activity in the brain; the phenomenally experienced, illusory position of the arm is indicated by the light outline). The resulting activation of neurons in the premotor cortex is demonstrated by experimental data. (M. Botvinick & J. Cohen, “Rubber Hand ‘Feels’ Touch That Eyes See,” Nature 391:756, 1998.) Figure by Litwak illustrations studio, 2004.
The PSM of Homo sapiens is probably one of nature’s best inventions. It is an efficient way to allow a biological organism to consciously conceive of itself (and others) as a whole. Thus it enables the organism to interact with its internal world as well as with the external environment in an intelligent and holistic manner. Most animals are conscious to one degree or another, but their PSM is not the same as ours. Our evolved type of conscious self-model is unique to the human brain, in that by representing the process of representation itself, we can catch ourselves—as Antonio Damasio would call it—in the act of knowing. We mentally represent ourselves as representational systems, in phenomenological real-time. This ability turned us into thinkers of thoughts and readers of minds, and it allowed biological evolution to explode into cultural evolution. The Ego is an extremely useful instrument—one that has helped us understand one another through empathy and mind-reading. Finally, by allowing us to externalize our minds through cooperation and culture, the Ego has enabled us to form complex societies.
What lessons can be learned from the rubber-hand illusion? The first point is simple to understand: Whatever is part of your PSM, whatever is part of your conscious Ego, is endowed with a feeling of “mineness,” a conscious sense of ownership. It is experienced as your limb, your tactile sensation, your feeling, your body, or your thought. But then there is a deeper question: Isn’t there something more to the conscious self than the mere subjective experience of ownership for body parts or mental states? Isn’t there something like “global ownership,” a deeper sense of selfhood having to do with owning and controlling your body as a whole? What about the experience of identifying with it? Could this deep sense of selfhood perhaps be experimentally manipulated? When I first experienced the rubber-hand illusion, I immediately thought it would be important to see whether this would also work with a whole rubber body or an image of yourself. Could one create a full-body analog of the rubber-hand illusion? Could the entire self be transposed to a location outside of the body?
As a matter of fact, there are phenomenal states in which people have the robust feeling of being outside their physical body—these are the so-called out-of-body experiences, or OBEs. OBEs are a well-known class of states in which one undergoes the highly realistic illusion of leaving one’s physical body, usually in the form of an etheric double, and moving outside of it. Phenomenologically, the subject of experience is located in this double. Obviously, if one seriously wants to understand what the conscious self is, these experiences are of great philosophical and scientific relevance. Could they be created in the lab?
One of the neuroscientists I am proud to collaborate with is Olaf Blanke, a brilliant young neurologist at the Swiss Federal Institute of Technology in Lausannne, who was the first scientist to trigger an OBE by directly stimulating the brain of a patient with an electrode. There are typically two representations of one’s body in these experiences: the visual one (the sight of your own body, lying on the bed, say, or on an operating table) and the felt one, in which you feel yourself to be hovering above or floating in space. Interestingly, this second body-model is the content of the PSM. This is where the Ego is. In a series of virtual-reality experiments, Olaf, his PhD student Bigna Lenggenhager, and I attempted to create artificial OBEs and full-body illusions (see chapter 3).2 During these illusions, subjects localized themselves outside their body and transiently identified with a computer-generated, external image of it. What these experiments demonstrate is that the deeper, holistic sense of self is not a mystery immune to scientific exploration—it is a form of conscious representational content, and it can be selectively manipulated under carefully controlled experimental conditions.
Throughout the book, I use one central metaphor for conscious experience: the “Ego Tunnel.” Conscious experience is like a tunnel. Modern neuroscience has demonstrated that the content of our conscious experience is not only an internal construct but also an extremely selective way of representing information. This is why it is a tunnel: What we see and hear, or what we feel and smell and taste, is only a small fraction of what actually exists out there. Our conscious model of reality is a low-dimensional projection of the inconceivably richer physical reality surrounding and sustaining us. Our sensory organs are limited: They evolved for reasons of survival, not for depicting the enormous wealth and richness of reality in all its unfathomable depth. Therefore, the ongoing process of conscious experience is not so much an image of reality as a tunnel through reality.
Whenever our brains successfully pursue the ingenious strategy of creating a unified and dynamic inner portrait of reality, we become conscious. First, our brains generate a world-simulation, so perfect that we do not recognize it as an image in our minds. Then, they generate an inner image of ourselves as a whole. This image includes not only our body and our psychological states but also our relationship to the past and the future, as well as to other conscious beings. The internal image of the person-as-a-whole is the phenomenal Ego, the “I” or “self ” as it appears in conscious experience; therefore, I use the terms “phenomenal Ego” and “phenomenal self ” interchangeably. The phenomenal Ego is not some mysterious thing or little man inside the head but the content of an inner image—namely, the conscious self-model, or PSM. By placing the self-model within the world-model, a center is created. That center is what we experience as ourselves, the Ego. It is the origin of what philosophers often call the first-person perspective. We are not in direct contact with outside reality or with ourselves, but we do have an inner perspective. We can use the word “I.” We live our conscious lives in the Ego Tunnel.
In ordinary states of consciousness, there is always someone having the experience—someone consciously experiencing himself as directed toward the world, as a self in the act of attending, knowing, desiring, willing, and acting. There are two major reasons for this. First, we possess an integrated inner image of ourselves that is firmly anchored in our feelings and bodily sensations; the world-simulation created by our brains includes the experience of a point of view. Second, we are unable to experience and introspectively recognize our self-models as models; much of the self-model is, as philosophers might say, transparent.3 Transparency simply means that we are unaware of the medium through which information reaches us. We do not see the window but only the bird flying by. We do not see neurons firing away in our brain but only what they represent for us. A conscious world-model active in the brain is transparent if the brain has no chance of discovering that it is a model—we look right through it, directly onto the world, as it were. The central claim of this book—and the theory behind it, the self-model theory of subjectivity4—is that the conscious experience of being a self emerges because a large part of the PSM in your brain is transparent.
The Ego, as noted, is simply the content of your PSM at this moment (your bodily sensations, your emotional state, your perceptions, memories, acts of will, thoughts). But it can become the Ego only because you are constitutionally unable to realize that all this is just the content of a simulation in your brain. It is not reality itself but an image of reality—and a very special one indeed. The Ego is a transparent mental image: You—the physical person as a whole—look right through it. You do not see it. But you see with it. The Ego is a tool for controlling and planning your behavior and for understanding the behavior of others. Whenever the organism needs this tool, the brain activates a PSM. If—as, for instance, in dreamless deep sleep—the tool is not needed anymore, it is turned off.
It must be emphasized that although our brains create the Ego Tunnel, no one lives in this tunnel. We live with it and through it, but there is no little man running things inside our head. The Ego and the Tunnel are evolved representational phenomena, a result of dynamical self-organization on many levels. Ultimately, subjective experience is a biological data format, a highly specific mode of presenting information about the world by letting it appear as if it were an Ego’s knowledge. But no such things as selves exist in the world. A biological organism, as such, is not a self. An Ego is not a self, either, but merely a form of representational content—namely, the content of a transparent self-model activated in the organism’s brain.
Variations of this tunnel metaphor illustrate other new ideas in mind science: What would it mean for an Ego Tunnel to branch out to include other Ego Tunnels? What happens to the Ego Tunnel during the dream state? Can machines possess an artificial form of self-consciousness, and can they develop a proper Ego Tunnel? How do empathy and social cognition work; how can communication take place from one tunnel to the next? Finally, of course, we must ask: Is it possible to leave the Ego Tunnel?
The idea of an Ego Tunnel is based on an older notion that has been around for quite some time now. It is the concept of a “reality tunnel,” which can be found in research on virtual reality and the programming of advanced video games, or in the popular work of nonacademic philosophers such as Robert Anton Wilson and Timothy Leary. The general idea is this: Yes, there is an outside world, and yes, there is an objective reality, but in moving through this world, we constantly apply unconscious filter mechanisms, and in doing so, we unknowingly construct our own individual world, which is our “reality tunnel.” We are never directly in touch with reality as such, because these filters prevent us from seeing the world as it is. The filtering mechanisms are our sensory systems and our brain, the architecture of which we inherited from our biological ancestors, as well as our prior beliefs and implicit assumptions. The construction process is largely invisible; in the end, we see only what our reality tunnel allows us to see, and most of us are completely unaware of this fact.
From a philosopher’s point of view, there is a lot of nonsense in this popular notion. We don’t create an individual world but only a world-model. Moreover, the whole idea of potentially being directly in touch with reality is a sort of romantic folklore; we know the world only by using representations, because (correctly) representing something is what knowing is. Also, the Ego Tunnel is not about what psychologists call “confirmation bias”—that is, our tendency to notice and assign significance to observations that confirm our beliefs and expectations, while filtering out or rationalizing away observations that do not. Nor is it true that we can never get out of the tunnel or know anything about the outside world: Knowledge is possible, for instance, through the cooperation and communication of large groups of people—scientific communities that design and test theories, constantly criticize one another, and exchange empirical data and new hypotheses. Finally, the popular notion of a reality tunnel is playfully used in simply too many ways and contexts and therefore remains hopelessly vague.
In the first chapter, I confine discussion to the phenomenon of conscious experience and develop a better and richer understanding of why exactly it is exclusively internal. One question to be addressed is, How can all this take place inside the brain and at the same time create the robust experience of living in a reality that is experienced as an external reality? We want to understand how what Finnish philosopher and neuroscientist Antti Revonsuo calls an “out-of-brain experience” is possible: the experience you have all the time—for instance, right now, as you are reading this book. The robust experience of not being in a tunnel, of being directly and immediately in touch with external reality, is one of the most remarkable features of human consciousness. You even have it during an out-of-body experience.
To confine oneself to studying consciousness as such means to consider the phenomenal content of one’s mental representations—that is, how they feel to you from the first-person perspective, what it is like (subjectively, privately, inwardly) to have them. For example, the predominant phenomenal content of seeing a red rose is the quality of redness itself. In the conscious experience of smelling a mixture of amber and sandalwood, the phenomenal content is that raw subjective quality of “amber-ness” and “sandalwood-ness,” ineffable and apparently simple. In experiencing an emotion—say, feeling happy and relaxed—the phenomenal content is the feeling itself and not whatever it refers to.
All evidence now points to the conclusion that phenomenal content is determined locally, not by the environment at all but by internal properties of the brain only. Moreover, the relevant properties are the same regardless of whether the red rose is there in front of you or merely imagined or dreamed about. The subjective sandalwood-and-amber experience doesn’t require incense, it doesn’t even require a nose; in principle it can also be elicited by stimulating the right combination of glomeruli in your olfactory bulb. Glomeruli (there are some two thousand of them) take input from one type or another of your olfactory receptor cells. If the unified sensory quality of smelling sandalwood and amber typically involves activating smell receptor cells of type 18, 93, 143, and 211 in your nose, then we would expect to get the same conscious experience—an identical odor—by stimulating the corresponding glomeruli with an electrode. The question is, What is the minimally sufficient set of neural properties? Could we selectively elicit exactly the same phenomenon by doing even less, possibly at another location in the brain? Most neuroscientists, and probably the majority of philosophers as well, would answer yes: Activate the minimal neural correlate of a given conscious experience and you get the conscious experience itself.
The same general idea holds for more complex states: Their phenomenal content is precisely that aspect of a state (say, of happiness plus relaxation) that not only emerges naturally in everyday situations but can also be caused by a psychoactive substance—or, at least in principle, triggered by an evil neuroscientist experimenting on a living brain in a vat. The problem of consciousness is all about subjective experience, about the structure of our inner life, and not about knowledge of the outer world.
One way of looking at the Ego Tunnel is as a complex property of the global neural correlate of consciousness (NCC). The NCC is that set of neurofunctional properties in your brain sufficient to bring about a conscious experience. There is a specific NCC for the redness of the rose you experience, another for the perceptual object (that is, the rose as a whole), and yet another underlying your accompanying feeling of happiness and relaxation. But there is also a global NCC—that is, a much larger set of neural properties underlying consciousness as a whole, underpinning your experiential model of the world, the totality of everything you subjectively feel. The incessant information flow in this global NCC is what creates the tunnel, the world in which you live your conscious life.
But what is this “you”? As I claimed at the outset, we will never have a truly satisfying comprehensive scientific theory of the human mind if we don’t dissolve the core of the problem. If we want everything to fall into place—if we want to understand the big picture—then this is the challenge. Why is consciousness subjective? The most important question I seek to answer is why a conscious world-model almost invariably has a center: a me, an Ego, an experiencing self. What exactly is the self that has the rubber-hand illusion? What exactly is it that apparently leaves the physical body in an OBE? What exactly is it that is reading these lines right now?
An Ego Tunnel is a consciousness tunnel that has evolved the additional property of creating a robust first-person perspective, a subjective view of the world. It is a consciousness tunnel plus an apparent self. This is the challenge: If we want the big picture, we need to know how a genuine sense of selfhood appears. We have to explain your experience of yourself as feeling the tactile sensation in the rubber hand, of yourself as understanding the sentences you’re reading right now. This genuine conscious sense of selfhood is the deepest form of inwardness, much deeper than just being “in the brain” or “in a simulated world in the brain.” This nontrivial form of inwardness is what this book is about.