The now problem: a lived moment emerges

Here is something that, as a philosopher, I have always found both fascinating and deeply puzzling: A complete scientific description of the physical universe would not contain the information as to what time is “now.” Indeed, such a description would be free of what philosophers call “indexical terms.” There would be no pointers or little red arrows to tell you “You are here!” or “Right now!” In real life, this is the job of the conscious brain: It constantly tells the organism harboring it what place is here and what time is now. This experiential Now is the second big problem for a modern theory of consciousness.¹⁰

The biological consciousness tunnel is not a tunnel only in the simple sense of being an internal model of reality in your brain. It is also a time tunnel — or, more precisely, a tunnel of presence. Here we encounter a subtler form of inwardness — namely, an inwardness in the temporal domain, subjectively experienced.

The empirical story will have to deal with short-term memory and working memory, with recurrent loops in neural networks, and with the binding of single events into larger temporal gestalts (often simply called the psychological moment). The truly vexing aspect of the Now Problem is conceptual: It is very hard to say what exactly the puzzle consists of. At this point, philosophers and scientists alike typically quote a passage from the fourteenth chapter of the eleventh book of St. Augustine’s Confessions. Here the Bishop of Hippo famously notes, “What then is time? If no one asks me, I know. If I wish to explain it to one that asketh, I know not.” The primary difficulty with the Now Problem is not the neuroscience but how to state it properly. Let me try: Consciousness is inwardness in time. It makes the world present for you by creating a new space in your mind — the space of temporal internality. Everything is in the Now. Whatever you experience, you experience it as happening at this moment.

You may disagree at first: Is it not true that my conscious, episodic memory of my last walk on the beach refers to something in the past? And is it not true that my conscious thoughts and plans about next weekend’s trip to the mountains refer to the future? Yes, this is true — but they are always embedded in a conscious model of the self as remembering the starfish on the beach right now, as planning a new route to the peak at this very moment.

A major function of conscious experience consists, as the great British psychologist Richard Gregory has put it, in “flagging the dangerous present.”¹¹ One essential function of consciousness is to help an organism stay in touch with the immediate present — with all those properties in both itself and the environment that may change fast and unpredictably. This idea relates to a classic concept introduced by Bernard Baars of the Neurosciences Institute in San Diego, best known for his book A Cognitive Theory of Consciousness, in which he outlines his global-workspace theory as a model for consciousness. His fruitful metaphor of consciousness as the content of a global workspace of the mind implies that only the critical aspects are represented in consciousness. Conscious information is exactly that information that must be made available for every single one of your cognitive capacities at the same time. You require a conscious representation only if you do not know exactly what will happen next and which capacities (attention, cognition, memory, motor control) you will need to react properly to the challenge around the corner. This critical information must remain active so that different modules or brain mechanisms can access it simultaneously.

My idea is that this simultaneity is precisely why we need the conscious Now. In order to effect this, our brains learned to simulate temporal internality. In order to create a common platform — a blackboard on which messages to our various specialized brain areas can be posted — we need a common frame of reference, and this frame of reference is a temporal one. Although, strictly speaking, no such thing as Now exists in the outside world, it proved adaptive to organize the inner model of the world around such a Now — creating a common temporal frame of reference for all the mechanisms in the brain so that they can access the same information at the same time. A certain point in time had to be represented in a privileged manner in order to be flagged as reality. The past is outside-time, as is the future. But there is also insidetime, this time, the Now, the moment you’re currently living. All your conscious thoughts and feelings take place in this lived moment.

How are we going to find this special form of inwardness in the biological brain? Of course, conscious time experience has other elements. We experience simultaneity. (And have you ever noticed that you cannot will two different actions at the same moment or simultaneously make two decisions?) We experience succession: of the notes in a piece of music, of two thoughts drifting by in our minds, one after the other. We experience duration: A musical tone or an emotion may stay constant over time. From all this emerges what the neuroscientist Ernst Pöppel, one of the pioneer researchers in this field, and his colleague Eva Ruhnau, director of the University of Munich’s Human Science Center, describe as a temporal gestalt:¹² Musical notes can form a motif — a bound pattern of sounds constituting a whole that you recognize as such from one instant to the next. Similarly, individual thoughts can form more complex conscious experiences, which may be described as unfolding patterns of reasoning.

By the way, there is an upper limit to what you can consciously experience as taking place in a single moment: It is almost impossible to experience a musical motif, a rhythmic piece of poetry, or a complex thought that lasts for more than three seconds as a unified temporal gestalt. When I was studying philosophy in Frankfurt, professors typically did not extemporize during their lectures; instead, they read from a manuscript for ninety minutes, firing rounds of excessively long, nested sentences, one after another, at their students. I suspected that these lectures were not aimed at successful communication at all (although they were frequently about it) but that this was a kind of intellectual machismo. (“I am going to demonstrate the inferiority of your intelligence to you by spouting fantastically complex and seemingly endless sentences. They will make your short-term buffer collapse, because you cannot integrate them into a single temporal gestalt anymore. You won’t understand a thing, and you will have to admit that your tunnel is smaller than mine!”)

I assume many of my readers have encountered this type of behavior themselves. It is a psychological strategy we inherited from our primate ancestors, a slightly more subtle form of ostentatious display behavior that made its way into academia. What enables this new kind of machismo is the limited capacity of the moving window of the Now. Looking through this window, we see enduring objects and meaningful chains of events. Underlying all these experiences of duration, succession, and the formation of temporal wholes is the rock-solid bed of presence. In order to understand what the appearance of a world is, we urgently need a theory of how the human brain generates this temporal sense of presence.

Presence is a necessary condition for conscious experience. If the brain could solve the One-World Problem but not the Now Problem, a world could not appear to you. In a deep sense, appearance is simply presence, and the subjective sense of temporal immediacy is the definition of an internal space of time.

Is it possible to transcend this subjective Now-ness, to escape the tunnel of presence? Imagine you are lost in a daydream. Completely. Your conscious mind is not “flagging the dangerous present” anymore. Those animals in the history of our planet that did this too often did not stand a chance of becoming our ancestors; they were eaten by other, less pensive animals. But what actually happens at the moment you fully lose contact with your present surroundings, say, in a manifest daydream? You are suddenly somewhere else. Another lived Now emerges in your mind. Now-ness is an essential feature of consciousness. And, of course, it is an illusion. As modern-day neuroscience tells us, we are never in touch with the present, because neural informationprocessing itself takes time. Signals take time to travel from your sensory organs along the multiple neuronal pathways in your body to your brain, and they take time to be processed and transformed into objects, scenes, and complex situations. So, strictly speaking, what you are experiencing as the present moment is actually the past.

At this point, it becomes clear why philosophers speak about “phenomenal” consciousness or “phenomenal” experience. A phenomenon is an appearance. The phenomenal Now is the appearance of a Now. Nature optimized our time experience over the last couple of millions of years so that we experience something as taking place now because this arrangement is functionally adequate in organizing our behavioral space. But from a more rigorous, philosophical point of view, the temporal inwardness of the conscious Now is an illusion. There is no immediate contact with reality.

This point gives us a second fundamental insight into the tunnel-like nature of consciousness: The sense of presence is an internal phenomenon, created by the human brain. Not only are there no colors out there, but there is also no present moment. Physical time flows continuously. The physical universe does not know what William James called the “specious present,” nor does it know an expanded, or “smeared,” present moment. The brain is an exception: For certain physical organisms, such as us, it has proved viable to represent the path through reality as if there were an extended present, a chain of individual moments through which we live our lives. I like James’s metaphor, according to which the present is not a knife-edge but a saddleback with a breadth of its own, on which we sit perched and from which we look in two directions into time. Of course, from the illusory smearing of the present moment in human consciousness it does not follow that some kind of nonsmeared present could not exist on the level of physics — but remember, a complete physical description of the universe would not contain the word “now”; there would be no little red arrow telling us “This is your place in the temporal order.” The Ego Tunnel is just the opposite of a God’s-eye view of the world. It has a Now, a Here — and a Me, being there now.

The lived Now has a fascinating double aspect. From an epistemological point of view, it is an illusion (the present is an appearance). The moving window of the conscious Now, though, has proved functionally advantageous for creatures like us: It successfully bundles perception, cognition, and conscious will in a way that selects just the right parameters of interaction with the physical world, in environments like those in which our ancestors fought for survival. In this sense, it is a form of knowledge: functional, nonconceptual knowledge about what will work with this kind of body and these kinds of eyes, ears, and limbs.

What we experience as the present moment embodies implicit knowledge about how we can integrate our sensory perceptions with our motor behavior in a fluid and adaptive manner. However, this type of knowledge applies only to the kind of environment we found on the surface of this planet. Other conscious beings, in other parts of the universe, might have evolved completely different forms of time experience. They might be frozen into an eternal Now or have a fantastically high resolution, living for only a few of our Earth minutes and experiencing more intense individual moments than a million human beings experience in a lifetime. They could be masters of boredom, subjects of an extremely slow passage of time. A good (and more difficult) question is how much room for variation there is in terms of subjective time experience. If my argument is sound, conscious minds can be situated only in one single, real Now at a time — because this is one of the essential features of consciousness. Is it logically possible to live in two or more absolutely equivalent Nows at the same time, to have a subjective perspective originating from multiple points in the temporal order? I don’t think so, because there would no longer be one single, present “self” who had these experiences. Moreover, it’s hard to imagine a situation in which experiencing multiple lived presents might have been adaptive. Thus, although no such thing as an extended present exists from a strict philosophical point of view or from the perspective of a physicist, there must be deep biological truths and a profound evolutionary wisdom behind the way conscious beings such as ourselves happen to represent time in the brain.

Even given a radically materialist view of mind and consciousness, one must concede that there is a complex physical property that (as far as we know) exists only in biological nervous systems on this planet. This new property is a virtual window of presence, and it is implemented in the brains of vertebrates and particularly of higher mammals. It is the lived Now. The physical passage of time existed before this property emerged, but then something new was added — a representation of time, including an illusory, smeared present, plus the fact that the beings harboring this new property in their brains could not recognize it as a representation. Billions of conscious, time-representing nervous systems created billions of individual perspectives.

At this point, we also touch on a deeper and more general principle running through modern research on consciousness. The more aspects of subjective experience we can explain in a hardheaded, materialistic manner, the more our view of what the self-organizing physical universe itself is will change. Very obviously, and in a strictly no-nonsense, nonmetaphorical, and nonmysterious way, the physical universe itself possesses an intrinsic potential for the emergence of subjectivity. Crude versions of objectivism are false, and reality is much richer than we thought.

Дата добавления: 2015-10-31