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L'émergence de la conscience

HelpOnline papers on consciousness compiled by David ChalmersThe Puzzle of Conscious ExperienceMoving Forward on the Problem of Consciousness
Why Great Minds Can't Grasp ConsciousnessThe Center for Consciousness Studies at the University of Arizona: The Problem of ConsciousnessLes zombis philosophiquesFacing Up to the Problem of Consciousness
The Puzzle of Conscious ExperienceJournal of Consciousness StudiesPSYCHE, an interdisciplinary journal of research on consciousnessBook: Purple Haze. The Puzzle of Consciousness. By Joseph Levine
Science et conscienceMoving Forward on the Problem of ConsciousnessFacing Backwards on the Problem of ConsciousnessState of the Art - The Psychology of Consciousness
AN INTEGRAL THEORY OF CONSCIOUSNESS, by Ken WilberScience & Consciousness ReviewAssociation for the Scientific Study of ConsciousnessChristof Koch Lecture 1:  Prolegomenon to the Study of Consciousness
David ChalmersNed Block

The “hard problem” of consciousness in fact constitutes the central question of the philosophy of mind: the broader relationship between the body and the mind that philosophers have been trying to understand since the dawn of time.

This “mind-body problem” of course takes a different form today than it did in the time of Descartes. In those days, science was still in its infancy, and it was still possible for a serious thinker to conceive of this problem in a non-materialist framework—something that most scientists today regard as problematic, to say the least.

This major difference affects the very way we approach the mind-body problem today. Descartes said that he doubted everything except his own thinking and his conscious experience of having qualia. Today, the definition and the very existence of qualia are questioned by philosophers such as Daniel Dennett.

Another central question of the philosophy of mind is how our conscious intentions can be the cause of the activation of neurons that lead to the contraction of our muscles, so that they do what we were planning to do. Other scientists today also question whether the intentions that are the source of our behaviours are in fact conscious; hence these thinkers question the very foundations of our free will.

Thus the field of the philosophy of mind may have narrowed since the time of Descartes, but it is still far from exhausted.

Lien : Quining Qualia

Some authors, such as philosopher Colin McGinn and linguist Steven Pinker, think that the difficulties we experience in dealing with the hard problem of consciousness are simply due to the limitations of the human brain. This brain is the product of evolution, and, like the brains of other animals, it has its cognitive limits. For example, a human brain cannot hold 100 digits in its short-term memory, cannot visualize a 7-dimensional space, and perhaps also may be unable to understand how neuronal activity that can be observed from the outside can give rise to our subjective inner experience. But of course, the authors who hold this position cannot completely discard the possibility that new ideas might emerge from the head of a future Darwin or Einstein to shed a completely new light on this question.



The idea of consciousness covers a variety of phenomena; the categories of consciousness as distinguished by philosopher Ned Block are described in the first box below.

In 1994, at the first “Toward a Science of Consciousness” conference in Tucson, Arizona, philosopher David Chalmers proposed that the problems posed by the study of consciousness could be divided into two distinct types: the “easy problems” of consciousness and the “hard problem” of consciousness.

When Chalmers talked about the “easy problems”, he was of course speaking in relative terms. These problems are “easy” in the same sense that the problems of curing cancer and sending a person to Mars are “easy”: they are far from having been solved, but scientists have a good idea of the steps that they must still complete to solve them.

In the case of consciousness, the “easy problems” are to explain certain characteristics of consciousness that seem solvable by the classic methods of scientific observation and experimentation. For example, a conscious experience of pain may be attributed to an injury suffered by the body. Scientists can then investigate further and discover that pain reception in human beings occurs through one system of “A” nerve fibres, another system of “C” nerve fibres, and so on.

The same classic methods can be used to investigate the mechanics of all of the unconscious processes (vision, memory, attention, emotions, etc.) that make consciousness possible. Thus, when it comes to the “easy problems” of consciousness, investigators can hope to identify the brain processes underlying them and attempt to understand why they have evolved. Or to paraphrase Chalmers, we can hope to find adequate functional explanations for these phenomena.

The “hard problem” of consciousness arises from discoveries made in the field of physics in the first half of the 20th century. These discoveries made it hard to find a place in the world for consciousness. Everything was so much simpler before, when philosophers and scientists had no trouble in assuming that the reality of consciousness was at least as “real” as the reality of the physical world. But once the world in its entirety came to be understood as the relationships among forces, atoms, and molecules, that left very little room for the subjective aspect of consciousness.

And it is precisely this aspect that constitutes the heart of what Chalmers calls the “hard problem” of consciousness, or what his fellow philosopher Joseph Levine calls the “explanatory gap”. For these two thinkers, no explanations about the causal role of our states of mind and their instantiation in a given nervous system (the easy problems) will ever tell us anything about the subjective dimension of consciousness or, to borrow the language of another philosopher, Thomas Nagel, about “what it is like” to be oneself and to experience qualia subjectively.

In other words, any solution to the hard problem of consciousness must do more than explain, for instance, the processes that let us distinguish the colour red from the colour green, which is an example of an “easy problem”. A solution to the hard problem must also explain how this particular subjective impression of the “redness” of some object can arise from the activity of our neuronal assemblies. In its simplest form, the hard problem may be couched as follows: why does the activity of my brain make me feel something rather than nothing? Thus the hard problem focuses chiefly on the phenomenological aspect of consciousness, whereas the easy problems are more concerned with the functional aspects.

As often happens in new fields of study such as consciousness, a whole constellation of different solutions to the hard problem have been proposed, often contradicting one another. To help you understand them more clearly, the next main section of this page describes the various positions that various groups of philosophers have taken on the hard problem of consciousness, and how these positions are classified conceptually. This classification generally depends on whether the philosophers in question accept or reject certain premises, which often makes for some complex combinations of positions.


Various thinkers have taken a variety of fairly convergent approaches to categorizing the various forms of human consciousness. For philosopher Ned Block, there are at least four main aspects of consciousness that are manifested in the waking state. They are as follows.:

Access consciousness refers to any state of consciousness where, when you are in it, a representation of its content is immediately available to you. You can then use this representation as a basis for reasoning and apply it in your rational control of your actions and speech. The concept of access consciousness recalls that of the global workspace.

Phenomenal consciousness corresponds to the qualitative aspects, or qualia, of our mental lives—in other words, “what it is like” to feel a pain, perceive a colour, etc.

Reflexive consciousness (or “monitoring” consciousness) is the ability to deliberately scrutinize the flow of one’s own thoughts, to engage in introspection, and to track one’s own behaviours.

Self-consciousness is the representation of self that imparts a certain unity to one’s mental life.


The expression “altered states of consciousness” refers to usually temporary experiences in which people have the impression that the normal functioning of their consciousness has been disturbed. For example, after experiencing an altered state of consciousness, someone might say that they had had the impression of living in a different relationship with the world, with their identity, or with their body.

Altered states of consciousness may be associated with events connected to sleep, such as falling asleep, sleepwalking, or being sleep-deprived. Altered states may be induced by another person (as in hypnosis), or by oneself (through meditation, prayer, or physical exercise, for example), or by a group dynamic (as in a collective trance state). Altered states may also be associated with pathological conditions, such as fever or oxygen deprivation, or with the use of drugs.

One example of a drug-induced altered state would be the very well documented effects of marijuana on the various components of consciousness, such as sensory inputs, clarity of perception, distortion of time, memory, expectations, functional associations, and attention.

The pursuit, attainment, and consequences of altered states of consciousness may be socially acceptable and recognized or socially disapproved and illegal (as, for example, in the case of the use of certain drugs).

In general, there seems to be an optimal register of external stimulation that is needed to maintain a normal waking state of consciousness. Levels of stimulation above or below this register seem to result in altered states of consciousness. For example, the extreme boredom that comes with being deprived of social contact for prolonged periods can induce altered states. But altered states can also be induced by situations that demand, on the contrary, sustained alertness or a high degree of concentration (being intensely absorbed in a task, reading, performing in a sport, etc).


Contrary to what McGinn and Pinker believe (see sidebar), Gerald Edelman sees no intrinsic problem in the scientific study of consciousness. He summarizes his position in the following two sentences: “If the phenomenal part of conscious experience that constitutes its entailed distinctions is irreducible, so is the fact that physics has not explained why there is something rather than nothing. Physics is not hindered by this ontological limit nor should the scientific understanding of consciousness be hindered by the privacy of phenomenal experience.”

Lien : The Mystery of Consciousness


Levels of explanationMary the colour scientistBook : Introducing ConsciousnessStairway to the Mind. By Alwyn Scott
ConsciousnessDavid Chalmers' collection of online papers on consciousnessDaniel Andler (ENS), Vidéo  Les neurosciences cognitives sont-elles réductrices ?The 19th Century: Mind and Brain
Classics in Psychology. 1855-1914 : Historical EssaysJaegwon Kim's book 'Physicalism, or something near enough'THINKING ABOUT THINKINGThe Puzzle of Conscious Experience
Review of Science and the Riddle of Consciousness by Jeffrey FossMaterialism, the philosophy that all is matter, or at least, all is governed by physical lawCartesian dualism, the philosophy that both matter and mind are primary and irreducibleIdealism, the philosophy that mind is all and all is mind
The teaching of nondualityL'émergence, les modèles de réduction et le mentalVI. The philosophy of consciousnessThéories de l’identité psychophysique
Philosophy of mindFaut-il éliminer l'esprit?PhysicalismeL'identité de l'esprit et du cerveau
Le fonctionnalismeLe physicalisme selon Jaegwon KimRésoudre le problème corp-esprit d’une façon radicale : le matérialisme éliminatifEliminative Materialism
Notre compréhension du physicalisme et de ses enjeuxStatut de la psychologie du sens communReduction and Emergence
Patricia S. ChurchlandPaul Churchland
Original modules
History Module: When the History of Science Sheds Light on the Philosophy of MindWhen the History of Science Sheds Light on the Philosophy of Mind

An even more radical stance than epiphenomenalism, psychophysical parallelism, postulates that mind and matter have distinct statuses but evolve in parallel, without exerting causal influences in either direction. In other words, matter only affects matter, and mind only affects mind.

The German philosopher Gottfried Leibniz defended this thesis of “pre-established harmony” in the 17th century. He believed that God had arranged things in advance so that minds and bodies would remain in constant harmony with each other.

Because many of today’s dualists acknowledge the complete nature of the causality of the physical world (see next sidebar), they have concluded that mental processes might not exert any causal influence on the physical world. Even though common sense encourages us to think that our intentions, desires, and feelings directly affect our behaviours, this may ultimately prove to be only an illusion, and consciousness might be causally powerless.

That is why, if these dualists are going to remain dualists, the concept of psychophysical parallelism is so useful to them. Because if mind and matter can’t really influence each other, then we can continue to assume that they go along together like two identical trains on parallel tracks. Thus mind and matter always remain in phase, so that, for example, sitting on a tack will always provoke a conscious sensation of pain.


Who’s in Charge—Us?

We Are All Complex Networks

The Collective Intelligence of Human Groups

The Infinitely Large, Infinitely Small, and Infinitely Complex

Even for property dualists, the question of how subjective states can influence matter without violating the laws of physics remains a thorny one, because the physical world demonstrates “complete causality”. A soccer goalie stops an incoming ball because his muscles have contracted, because electrical stimuli have travelled along certain nerves, because his motor cortex has experienced a certain activity, because his sensory cortex had done so just before that, because his retinas had registered the shape of the incoming ball, and so on.

Enaction proposes an especially original approach to this problem.

One widely shared materialist view is that it is the particular physiology of the human brain that makes us feel pain, just as it is the particular physiology of the octopus that must make it experience pain, and not, as functionalism would have it, some hypothetical structural similarity.

This suggests that other animals that do not share the physiology of the human brain would have trouble in experiencing human feelings. In contrast, functionalism offers the attractive proposition that such sharing of mental states among species is possible.

But many materialists dispute this proposition. They say that an octopus’s pain can very readily be distinguished from a human’s and that these two kinds of pain can very easily not be the same. For example, many neurobiologists consider it entirely possible that humans can attenuate their pain (or, indeed, amplify it) with all sorts of conscious thoughts that arise from their highly developed cerebral cortex, something that octopi obviously cannot do.

A position similar to functionalism is to admit that there is something very mysterious about subjective consciousness, or at least the impression that we have of it, but that it must be possible to explain this something by means of the physical processes of the material world. Hence the thinkers who espouse this position - many of whom are physicists or mathematicians - believe that the “hard problem” of consciousness can be solved only through the application of some elements of the equally mysterious realm of quantum physics, or even of some physical principles that have yet to be discovered.

As regards quantum physics, it is the probabilistic, indeterminate nature of this branch of science that, some people believe, opens a breach through which mental states might have an influence on the physical world.

To demonstrate the difficulties of the functionalist approach that allows for the possible existence of conscious states in machines, philosopher John Searle has devised a famous thought experiment known as the “Chinese room”.

In this experiment, Searle imagines that a man is in a room where he receives, through a slot in the wall, a piece of paper bearing a set of symbols in Chinese, which he does not understand. He then looks these symbols up in a book that matches them with another set of Chinese symbols, which he also does not understand, but he writes them down on a piece of paper and sends it back out of the room.

Now suppose that the first set of symbols was actually a series of questions in Chinese, and the second set was the right answers.

According to Searle, this man is like a computer program that is doing nothing but responding to inputs with appropriate outputs in a systematic, causal way. In other words, all he is doing is manipulating symbols according to the instructions written by a programmer (in the book containing the match-ups), without being able to assign any meaning to them. But Chinese-speaking people receiving the outputs outside the room might still be convinced that the man inside understands Chinese, because he would have passed the Turing test: he would have succeeded in fooling them.

This experiment thus shows the limitations of the Turing test and how the appearance of a conscious state may be mistaken for consciousness itself.

But not all functionalists have capitulated to the Chinese room argument. Some believe that what is essential is not to conclude that the man inside the room is not conscious, but rather that the man/room system as a whole may be. Nobody argues that a single transistor inside a computer can be conscious. It is rather the combination of all of the computer’s components that might be conscious, and not just some of them.

Lien : L’argument de la chambre chinoiseLien : Les machines peuvent-elles penser?Lien : The Chinese Room


Among all of the philosophical approaches proposed over the centuries to try to solve the “hard problem” of human consciousness, dualism and materialism are two that have gained the support of a considerable number of thinkers. But many of these thinkers have felt the need to nuance these two general theoretical positions so as to address the criticisms that have been levelled at them.

For example, to avoid the pitfalls of substance dualism, some philosophers have proposed an approach called “property dualism”. Property dualism recognizes that everything consists of matter, but holds that matter can have two types of properties, physical and mental, and that the latter cannot be reduced to the former. Property dualism is also often referred to as “non-reductive physicalism”.

According to this approach, pain, for example, would have a physical property (the action potentials transmitted by the C nerve fibres that sense pain) and, at the same, a conscious mental property (the feeling of pain).


Gottfried Wilhelm Leibniz (1646-1716)
Leibniz, see also the sidebar on
“pre-established harmony”.)

One of the arguments for property dualism is the “knowledge argument”. This argument was first presented by the German philosopher Gottfried Leibniz, in the 17th century. It was updated by Australian philosopher Frank Jackson in the 1980s, in the form of a little fable about anticipation.

Suppose, says Jackson, that a great neurobiologist has learned everything that she knows about colour perception from reading books about it, but has never seen a single colour in her entire life. The day that she sees a red rose for the first tine, she will learn something new about colour: what it is like to see the colour red. Which proves, according to Jackson, that matter has two distinct categories of properties.


For modern property dualists such as David Chalmers, this option does not constitute a rejection of science, but rather a call to broaden its horizons, by recognizing consciousness as a full-fledged entity, just as fundamental as space, time, or the force of gravity.

But the question of how subjective states can influence matter without violating the laws of physics remains unresolved. Not to mention that property dualism leads to panpsychism—the idea that all matter (even a thermostat, even a rock) has some conscious properties, however limited they might be.

Lien : Le dualisme des propriétés

Some dualists accept that the closed causality of the physical world must be respected at all times and that no mental state can influence the brain. For these dualists, mental states do exist, and are produced by the brain, but add nothing to its physical functioning. This philosophical position is called epiphenomenalism; it recognizes causal influences of the brain on the mind, but not the reverse. (Some philosophers have defended a more radical position, psychophysical parallelism, according to which there are no causal influences in either of these directions; see sidebar.)

For epiphenomenalists, the impression that our intentions, desires, and feelings directly affect our behaviours is therefore only an illusion, an “epiphenomenon”. Thus we adults would be somewhat like a small child playing with a toy steering wheel attached to his booster seat while his parent drives the car. The child gets so wrapped up in his play that he ends up believing that he’s the one who’s actually driving. Similarly, we give ourselves the illusion that it is our minds that are actually guiding our behaviours.

Nowadays, among those who accept the idea of a physical world in which conscious subjectivity exists, many are also prepared to accept that mental processes might not exert any causal influence on the physical world after all, even though common sense encourages us to think that our intentions, desires, and feelings do directly affect our behaviours.

According to these thinkers, the subjective feeling of thirst that makes us head for the kitchen faucet has nothing to do with our taking this action. Even more surprisingly, if consciousness has no influence on our behaviour, then it follows that our behaviour would remain exactly the same even if we were zombies, that is, even if our brain activity were not accompanied by mental states.

But it is hard to imagine ourselves as zombies, especially when you consider the verbal behaviours that we usually interpret as reflecting our mental states. David Chalmers has tried to show the difficulty of this position by caricaturing himself as a zombie with no mental states who is busy discussing consciousness with other zombie philosophers.

Lien : L’esprit comme un programme de machine

Other philosophers, whom American philosopher Paul Churchland has labelled “interactionist emergent property dualists”, believe that mental phenomena, even though they are not physical, can nevertheless play a causal role in the physical world. Once the brain has generated the subjective sensation of an odour or a colour, for example, this sensation could influence the functioning of the brain in return.

This stance, often referred to simply as emergentism for short, introduces the idea of a hierarchy of complexity in matter. According to the emergentists, only those systems that, through the process of evolution, have attained a sufficiently complex configuration can cause conscious phenomena to emerge. Emergentists thus see subjective consciousness as something that is more than the sum of its basic parts (neurons, for example), because these parts are physical, while subjective consciousness seems to be different in kind.

Once again, these emergent properties cannot be reduced to the basic properties from which they emerge. In other words, they can be neither predicted nor explained by the conditions underlying them. The classic example is the way that atoms combine to form a molecule with different properties. For instance, at room temperature, both hydrogen and oxygen are gases, but the water that forms from their combined atoms is a liquid.

Some materialist neurobiologists regard this concept of emergence and its strange nature as an excuse for not buckling down to the task of actually studying the neural correlates of consciousness. Other materialists, however, invoke the concept of emergence when they offer neurobiological models of consciousness in which consciousness emerges from the complexity of the proposed neural processes. But, according to their critics, they thereby leave an “explanatory gap” that tends to reduce their position to a form of mysterianism.

After Valentine, E.R. (1982) and


The materialist (or physicalist) alternative to dualism gets around this problem by positing that conscious states may not be distinct from physical states after all . The effect of our mental states on our behaviour is therefore no longer problematic, because both are part of the physical world.

Some materialists opt for a “dual-aspect” theory that considers the brain and the mind to be the same thing, but seen from two different perspectives: one external and objective, the other internal and subjective.

Other materialists, known as reductionist materialists, tend to simply reduce the mental to the physical. But they offer at least two different theories about the kind of identity relationship that exists between mental and physical events. Some reductionist materialists believe in type-to-type identity, in which a given type of mental event is considered identical to one, and only one, type of physical event. This is a theory of identity between two types of things—mental states on the one hand, and states of the brain on the other. For people who believe in type-to-type identity, if a flame burns your finger and makes you feel pain, this type of mental state is identical to the activation of a brain circuit that signals excessive, harmful heat.

But many objections have been raised to the idea of type-to-type identity. For example, some people argue that before you can declare a given mental state identical to a given physical state of the brain, you would have to know precisely what types of mental states actually exist, so that you would not identify this particular mental state with a brain state that is actually identical to some other mental state. But there is nowhere near any unanimity as to what mental states actually exist.

On the other hand, if we assume, for instance, that the love that a father feels for his children is identical to a certain state of his brain, it still seems far-fetched to claim that anyone who loves their children must have that exact same brain state. And what about other species? It does not seem impossible that in mice, for example, some types of pain may correspond to certain types of neurophysiological processes that are different from those found in the human brain. That is why the philosopher Ned Block has described the theory of type-to-type identity as “neuronal chauvinism”.

In contrast, the other identity theory embraced by some reductionist materialists, token-to-token identity, holds that no two people can have the exact same mental state. Consequently, a given mental state is always unique to a given individual. This unique mental state will therefore be identified with a neurophysiological state that is equally unique to the brain of that individual. In short, a token-to-token identity is a specific, individual case of identity between a unique mental state and an equally unique brain state.

Thus, whereas a “type” is a general concept, a “token” refers to a particular occurrence. In this version of identity theory, every individual can love his or her children in an entirely personal way, producing a mental state that is unique to that individual and identical to an equally unique neurophysiological state.

But is it conceivable that two individuals could have exactly the same mental state at a specific point in time? If it is, as the critics of token-to-token identity believe, then there could be some cases where the same mental state is physically manifested in two different ways in the brains of these two individuals. How can we then still speak of identity when one thing can be identical to two different things?

Lien : Une théorie robuste: l'identité esprit/cerveau

The answer to this question has come from another theory of the relationship between the body and the mind, known as functionalism. For functionalists, what is identical in the two different physical occurrences of the same mental state is the function—the complete set of cause-and-effect relationships between the internal mental states.

Functionalism thus accepts the idea that mental states are internal and hidden, yet does not go so far as to identify them with qualia, which are purely subjective experiences. Nor does it adopt the behaviourist stance, from which the mind is regarded as a “black box” that should be set aside in order to focus on purely behavioural explanations. Also, functionalists, even though they believe that mental states are hidden, unobservable phenomena, nevertheless consider them part of the physical world.

The classic functionalist analogy to describe this position is the analogy with a computer’s hardware and software. The hardware consists of the components that the computer is made of—integrated circuits, connectors, cables, and so on. The software consists of the various programs that the computer can run, such as your word processor or your e-mail package. These programs can often be installed on various types of hardware (PC, Mac, etc.), because the programmers have made sure to adapt the software’s essence—the causal structure of its components—to each of these types. What is essential is that when you type a command, it produces a certain internal state in the machine, and this state in return produces the right response on the screen. And that is exactly the way that functionalism envisions the human mind—in terms of causal relations among internal states.

Consequently, just as various types of computers can run similar types of software, various types of brains could have similar conscious states if they have structural modules that perform the same functions. This is the “multiple realization” argument, that mental states can be realized in multiple ways, on various platforms, and hence not necessarily in a human brain.

But functionalism does not necessarily require that the platform be physical, because there is no necessary logical connection between functionalism and materialism. The premise that there are mental states that are causally interrelated does not necessarily imply that these states are of a material nature. But given the current state of our knowledge, it seems rather implausible that there are causes and effects that are not physical. And in fact, the main defenders of functionalism are materialists.

Contrary to behaviourism, functionalism accepts that human beings have mental states inside themselves and that these states are the source of their behaviours. But functionalism sheds no light at all on the “subjective“ side of our mental states, their “qualia”. Hence functionalists have trouble in responding to criticisms centered on the existence of qualia, such as Frank Jackson’s story of the neurobiologist who sees the colour red for the first time or Thomas Nagel’s discussion of “what it is like to be a bat”.

Another objection to functionalism targets the hardware/software analogy, according to which the mind is to the brain as a software program is to a computer. American philosopher John Searle attacked this analogy with what some philosophers regard as the most difficult argument to refute: the “Chinese room” argument (see sidebar).

Another problem that materialist functionalists create for themselves is that by denying the importance of the particular substrate of neural physiology, they distance themselves from the particular strength of materialism, which says that the only conscious states of which we know, those of human beings,come from the activity of their physical substrate, that is, the form and activity of their networks of neurons.

Functionalism thus finds itself in the same position as epiphenomenalism, trying to explain how mental states can have an influence on the physical world.

Lien : Une théorie robuste: Le fonctionnalisme d'Armstrong et de LewisOutil : Similitudes et différences cerveau - ordinateurLien : Fixing Functionalism

All of the positions discussed so far accept the existence of “mental states”, meaning desires, beliefs, intentions, etc., at the origin of our behaviours. But the “eliminative” version of materialism states that these popular concepts are quite simply false, even if they seem to have real explanatory power.

The way that eliminative materialists see things, just as the setting of the Sun is an illusion that can be explained by the Earth’s rotation on its axis, so conscious mental states are only an illusion that will eventually be dispelled by progress in the neurosciences. That is why this form of materialism is called “eliminative”: it quite simply eliminates the concept that is causing the problem, i.e., mental states.

For philosophers such as Paul and Patricia Churchland, two of the main proponents of eliminative materialism, no one is conscious in the phenomenal sense—the sense of the “hard problem” of consciousness formulated by Chalmers. Instead, all problems can be reduced to the “easy” problems that may eventually be solved without recourse to physical properties other than those that we already know. In short, philosophers like the Churchlands believe that psychological explanations of our mental states are only temporary stopgaps that will one day be replaced by new neurobiological models.

Faced with arguments such as those of Jackson and his vision specialist who has never seen a colour, the eliminative materialists get around them by saying that one can speak of conscious states in two way: as being conscious, and as being physical. It is not a matter of two different properties, but rather of a single property that can be discussed in two different ways. It’s somewhat like discussing an actor’s role in a particular movie: you can talk about him using the name of the character he plays, or using his name in real life, but either way, you are talking about the same person, the same reality.

Another example is temperature. You learn to think of it in degrees first, but then you learn that it is the average kinetic energy of the particles concerned—two ways of conceptualizing the same reality.

Thus the eliminative materialists would say that Jackson’s vision specialist who is experiencing the colour red for the first time is basically just experiencing a new way of talking about the same reality.




MONTE GRANDE what is life?L'énaction: un concept des neurosciences cognitives"Review of F. Varela, E. Thompson and E. Rosch, The Embodied Mind," by Daniel C. DennettRestoring to cognition the forgotten primacy of action, intention and emotion
Reclaiming Cognition. The Primacy of Action, Intention and EmotionEncyclopaedia AutopoeticaWalter J. Freeman and Rafael Núñez Restoring to Cognition the Forgotten Primacy of Action, Intention and EmotionCognitio 2006 : Beyond the brain: embodied, situated & distributed cognition
Sciences cognitives et modèles de la penséeLa psychologie cognitive survivra-t-elle aux sciences cognitives?EmbodimentEnactivism (psychology)
L’étude de tout, par tous les moyens ; étude critique de Philosophie de l’esprit, état des lieuxIncarnation, cognition et représentation : comment les sciences cognitives pensent-elles le corps?EnactivismCognitio 2006 : La cognition incarnée, située et distribuée
Lien : Minding the Body in Social Interaction and CognitionLien : Minding the Body in Social Interaction and CognitionLien : Qu’est-ce qu’un concept scientifique ? L’exemple de l’énaction de Francisco Varela.Link : Video : Le cercle créatif dans l'entreprise
Francico VarelaMONTE GRANDE what is life? The new documentary with Francisco VarelaPierre Poirier
Sciences cognitives et modèles de la pensée

Many people may think that the importance that the theory of enaction accords to behaviour is a step backward to a form of traditional behaviourism. But enaction differs from behaviourism in the way that it conceives of behaviour. Unlike behaviourists, enaction theorists see behaviour not only as individuals’ accessing their mental processes and knowledge, but also as knowledge itself, which in turn is defined as any action that is adequate in the world.

Enaction theory also differs from behaviourism in the idea of agents that enaction theorists have developed. In enaction theory, every agent is an entity who learns, in a personalized way. Hence the regularity of the response to a given stimulus, which is the foundation of behaviourism, does not apply in this case. The same stimulus may trigger various behaviours, not only in different individuals, but also in the same individual at different times, because all agents are constantly learning and changing as the result of their experiences.

Shedding Some Light on the First Cell Membranes

In the early 1970s, Humberto Maturana and Francisco Varela formulated the concept of autopoiesis to try to capture the essence of living beings. Until then, living beings had been defined by various properties or functions observed in living systems. Maturana and Varela saw this reasoning as somewhat circular or teleological.

The word “autopoiesis” comes from the Greek words autos (“self”) and poiein (“to produce”). It refers to the ability of any living system to maintain its structure and renew its own components. Hence an autopoietic system is a complex network of elements that, through their interactions and transformations, constantly regenerate the network that produced them. In short, a living system continuously engenders and specifies its own organization.

Source: John Stewart

In this central idea of autonomy, Maturana and Varela distinguish the system’s “structure”, which is formed by all of its physical components, from its “organization”, which consists of the relationships among these components.

At just about the same time, Henri Laborit had made a similar distinction with his concepts of “structural information” and “circulating information”. The latter enables each level of organization of a living being to be open to the next level up, which thus becomes the servomechanism for the underlying regulated system (follow the Tool module link below).

Henri Atlan’s writings on self-organization also have been influenced by cybernetics and systems theory and mesh nicely with the concept of autopoiesis, because of the emphasis that they place on the idea of autonomy.

The concept of autopoiesis has many other implications. One is that it relegates definitions of life based on evolution and reproduction to a secondary role, because as the advocates of autopoeisis point out, for reproduction to occur, there must first be self-preservation of the living organism that makes reproduction possible. Only then could phylogenetic evolution come into play, at the time of reproduction.

Source: John Stewart

Another implication of autopoiesis is the impossibility of distinguishing between what comes from the environment and what comes from the system itself. Communication between a system and its environment is established by a reciprocal process called “structural coupling” (see next sidebar) that takes place between their respective elements. And it is the presence of possible couplings that enables the organism to preserve its identity. The main implication of this idea for the concept of the “self” is that the self is necessarily autopoietic—constantly changing, never fixed, and not resting on any stable base or foundation (see the first box to the right, on Buddhism).

Lien : Introduction à la pensée de Francisco J. VarelaOutil : La CybernétiqueLien : De la biologie à la société de l'informationLien : Reconfiguration de la question hiérarchique dans le capitalisme cognitif : le détour par Henri Laborit
Lien : Individuation, énaction, émergences et régulations bio-phycho-sociologiques du psychismeChercheur : Henri AtlanLien : Sites sur l'AutopoïèseLien : Qu’est-ce qu’un concept scientifique ? L’exemple de l’énaction de Francisco Varela.

From the enactive perspective, people interact with their environment through all of the personal experiences that they have stored in their memories. This interaction gives rise to what Varela and Maturana call structural coupling. This concept places the emphasis not on the optimal adaptation of an organism to various regularities in the world, but rather on the “viability”of a certain number of couplings between the organism and its environment.

It was on the basis of the concept of structural coupling that Varela and Maturana developed their vision of evolution, centered on the concept of natural drift.

Natural drift is distinct from Darwinian natural selection (see the Tool Module link below) in that natural drift sees the environment chiefly as something that prevents or prohibits certain couplings between an organism and its environment. If an organism does not have the structure needed to couple with its environment in one way or another, then that organism will disappear.

Consequently, the environment is not regarded as something that dictates organisms’ optimal structure to them, and in fact, a variety of structures may be able to accommodate themselves to the constraints imposed by the same environment.

Lien : “Enactivism” ou la théorie cognitive de la « Personnifiaction » : Une tentative pour mieux comprendre notre activité langagièreChercheur : Humberto MaturanaLien : Livre: Francisco Varela: A new idea of perception and life
Lien : Structural couplingLien : Entretien avec Francisco VarelaOutil : La sélection naturelle de Darwin

Situated robotics (see the last box to the right) places most of its emphasis on perception, action, and learning in a complex environment. In contrast, a related field, artificial life, is more concerned with using computer simulations to attempt to recreate the conditions of evolution and reproduction of life itself.

In other words, if biology is interested in the material bases of life, artificial-life research deals with the dynamic form of life, without reference to its material substance. Researchers in this field apply the concept of self-organization, and they conceive of life as a process emerging from the interactions of a large number of non-living elements.

For these researchers, understanding the essence of life thus comes down to understanding its abstract, dynamic organization—its logic. This makes artificial-life research a functionalist approach. It is open to the study of any form of “thought” and thus differs from the neurobiological theories of consciousness which focus on understanding the functioning of thought and of the human brain.

Lien : Vie ArtificielleLien : Vie Artificielle, présentation et illustration JavaLien : Vie artificielleLien : Artificial life
Lien : Artificial LifeLien : Recension de Totalement inhumaine, de Jean-Michel TruongLien : Totalement inhumaine, de Jean-Michel Truong



Around the 1950s and 1960s, behaviourism, the paradigm that had dominated the experimental study of the human mind since the start of the 20th century, gradually gave way to the cognitive sciences, which developed two major theories of consciousness: cognitivism and connectionism.

Cognitivism equates thinking with the manipulation of symbols and regards it as an algebra that operates on representations of the world, just as a digital computer does. Connectionism, in contrast, equates thinking with the operation of a network of neurons and argues that every cognitive operation is the result of countless interconnected units interacting among themselves, with no central control. Connectionism does, however, retain the idea of representation, which it defines as the correspondence between an emergent global state and some properties of the world.

Some critics believe that this idea of representation smacks strongly of dualism and maintains a separation between the mind and the body, as well as between the self and the external world. This conception of the human mind has also been criticized as too passive, reducing it to an input/output device for processing information. Some authors, such as Ryle, Freeman, and Núñez, have even argued that the concept of internal representation was an error of category, or simply a fiction.

These authors subscribe to a theory of human thought known as embodied cognition. They are influenced by pragmatists such as John Dewey and phenomenologists such as Merleau-Ponty, both of whom could conceive of actions and intentions without representations. The embodied-cognition critique of connectionism and cognitivism (and hence also of functionalism) revolves around the idea that the embodied experience of the individual in his or her environment plays a fundamental role in human thought. In addition to shedding new light on some of the astonishing cognitive abilities that we display every day (making unconscious inferences, coordinating speech and gestures, understanding language, etc.), the embodied cognition movement argues that many of the abilities that let us think about the world and interact with other people actually originated in the bodily experience of the individuals of our species.

This way of defining cognition by intimately linking the body with thought has produced some interesting alternatives to the epistemological difficulties of the representational models (see first three sidebars), and in particular to the restrictions imposed by linear causality, the “subject/object” dichotomy, and “body/mind” dualism. Among other things, it allows for a rehabilitation of the role of the emotions in cognition, a reconsideration of our everyday unconscious thought mechanisms as probably being of capital importance in our cognitive apparatus, and a recognition of the evolutionary data showing that the human brain has evolved in large part to allow the organization of social life. Embodied cognition is also consistent with the work of thinkers such as Vygotsky who have emphasized the social and cultural environment as the main driver of human cognitive development.

In the 1980s, a movement therefore developed that rejected the cognitivist and connectionist orthodoxy based on the idea of representation. To understand the essence of this new movement’s argument, consider the example of a baby who is learning to walk. No one teaches her any rules for doing so, as the cognitivist approach would postulate. Yet by trial and error, she learns how to maintain her balance on her articulated limbs, while avoiding obstacles that would upset that balance.

The connectionist approach is probably more appropriate for describing what is happening in this case, but another approach would be to seek a more complete understanding of this phenomenon by considering this baby’s particular legs and the environment in which she needs to move about.

This is the approach that was proposed by Francisco Varela, the author of many works that inspired the embodied cognition movement, notably The Embodied Mind: Cognitive Science and Human Experience (1991). This movement does not deny all the contributions of cognitivism and connectionism, but does deem them insufficient. For example, it does not discard the idea of symbol manipulation, but sees it as a higher-level description of properties that in practical terms are embodied in an underlying distributed system—the network of neurons. For Varela, this network can therefore be used to describe cognition adequately, but for such a network to be able to produce meaning, it must necessarily have a history, and it must be able to act on its environment and be sensitive to variations in that environment.

Indeed, in everyday life, what we observe in practical terms are embodied agents who are placed in situations where they can act and hence are completely immersed in their particular perspectives. For Varela, this is the subject on which cognitivism and the emergent properties of connectionism remain silent: our everyday human experience. This critique of the two major successive currents in the cognitive sciences places Varela in an epistemological position known as the theory of autopoiesis (see sidebar). This theory is accompanied by a particular methodology rooted in Buddhism (see box below). Together they form what is conventionally called the paradigm of enaction.


Conceptual chart of the state of the cognitive sciences in 1991, with the contributing disciplines and the various approaches (the term “Emergentism” here is equivalent to connectionism). Source: The Embodied Mind: Cognitive Science and Human Experience, by Francisco Varela, Evan Thompson, and Eleanor Rosch, Cambridge, MA: MIT Press, 1991.


From the perspective of enaction, perception has nothing to do with a static, contemplative attitude. Instead it consists in a form of action that is guided perceptually, in the way that the perceiving subject manages to guide his actions in his local situation of the moment. From this perspective, the surrounding world is shaped by the organism just as much as the organism is shaped by the surrounding world. In the language of enaction, the senses of smell and vision thus become not mere sensory receptors, but ways of enacting meanings.

Thus the reference point is no longer a world predetermined independently of the perceiving subject, but rather the subject’s own sensorimotor structure. Consequently, categorization emerges from our structural coupling with the environment (see sidebar), and our conceptual understanding of the world is necessarily shaped by our experience. Cognition therefore is not representation, but intrinsically depends on the capabilities of our own bodies.

Enaction also invites researchers in the cognitive sciences to place the greatest stock in first-person accounts and the irreducibility of experience, while refusing even the smallest concessions to dualism. This is also why enaction claims a kinship with phenomenology, not in its transcendental or highly theoretical sense, but rather in its etymological sense, meaning that which is manifested in the “first person”, in embodied thought. This thought must be “mindful and aware”, and hence non-abstract, and open to the body that makes it possible. This practice of mindfulness/awareness, Varela tells us, can be found in the Buddhist tradition. That is why he takes an interest in certain Buddhist practices calling for the gradual development of the ability to be present in both the mind and the body, both in meditation and in the experiences of ordinary life (see box below).

The main idea of enaction is that the cognitive faculties develop when a body interacts in real time with an environment that is just as real. This idea has had repercussions in several fields of research, in particular situated robotics (see box below).

Enaction also stimulates debates in still broader fields, such as consciousness, the nature of the self, and the very foundations of the world. Because if it is in the very nature of a cognitive system to function in and thanks to an embodied subjectivity, then the body, far from being cumbersome excess baggage, becomes both the limitation on all cognition and the condition that makes all cognition possible. And the body/brain system, far from being a mere cognitive machine that provides itself with representations of the world and finds solutions to problems, instead contributes to the joint evolution of the world and of the individual’s way of thinking about that world. In addition, that way of thinking is conditioned by the history of the various actions that this body has performed in this world.

To paraphrase the 19th century French philosopher Jules Lequier, it is a process of doing, and by so doing, of creating oneself. This concept of the psyche is also in line with Swiss psychologist Jean Piaget’s research on child development, which tended to show that the child’s psyche is constructed through its contacts with the environment, which leads the child to become conscious of itself and of the outside world simultaneously.

Both for Piaget and for Varela, the outside world is no longer the framework for our experience, against which the “I” stands out as a distinct entity. In other words, the relationship between the I and the world is no longer one of differentiation, but rather one of reciprocal engendering. The world, though it seems to have been there before thought commenced, actually is not separate from us: it is our body that enables us to discover a part of it. It is produced by the history of a structural coupling between a body and an environment, a coupling that is different for every living system.

This co-determination between cognitive system and environment thus calls into question the entire representational aspect of cognitivism and connectionism, which implies a world that is pre-formed and gradually represented. From the enactive perspective, it is instead the historical sequence of actions in context that causes the emergence of a world of meanings—an “enacted world”, to use Varela’s expression.

Francisco Varela wanted cognitive science, and in particular the theories of embodied cognition, to have an impact on people’s daily lives. But the daily practice that he proposed for exploring the “embodied mind” comes not from Western tradition but from Buddhism: a practice called “mindfulness/awareness meditation”. In this practice, to be mindful/aware means that one’s mind is present to daily experience, that one experiences what one’s mind is doing as it does it—in short, that one co-ordinates body and mind.

In this form of meditation, the individual also gradually makes peace with the idea that there is no specific, stable refuge in experience. This feeling is called “no-self” or“groundlessness” (sunyata). And in fact, the Buddhist path deals almost entirely with ways of overcoming emotional attachment to the self.

By relying on a philosophical tradition that is not abstract but is instead anchored in human experience, Varela seeks to go beyond the Western demand that we find an objective ground for our existence, at any expense. He believes that practicing mindfulness/awareness meditation would lead us to what Buddhist tradition calls the “Middle Way”, avoiding the two extremes of objectivism and nihilism. The two are intimately linked, according to Varela, inasmuch as nihilism may be a reaction to the loss of confidence in objectivism.

Objectivism is the idea that things can be understood as such, independently of the subject who perceives them. But this idea has had the ground pulled out out from under it by quantum physicists’ discoveries regarding the undecidable nature of reality. And because it is hard for Western thought to exist on less than solid ground, the temptation is strong to look for new ground that cannot be shaken. In this sense, the form of reality-denial that characterizes nihilism can be seen as a subtle form of objectivism, insofar as nihilism itself continues to provide a form of grounding.

For Varela, Buddhist mindfulness/awareness meditation, which takes our first-person experiences in our environment into account, provides the ideal way of returning to ourselves without having to believe that either subjectivity alone or the “objective world” constitutes an absolute ground for our existence.

This tradition also affords the opportunity for a reformulation of ethics in the absence of such foundations. By confronting our own tendencies to search for foundations, Varela believes, we end up developing a feeling of friendship toward ourselves that we can gradually extend to those around us.

This empathy would then be based not on any pragmatic moral injunctions, nor any system of ethical axioms, but rather on our ability to respond to ourselves and to others as sentient beings who suffer, because they cling to a self that does not actually exist. Groundlessness would thus prove to be a form of all-encompassing, non-egotistical concern for all sentient beings.

Lien : Incarnation, cognition et représentation : comment les sciences cognitives pensent-elles le corps?

The embodied-cognition approach has also had a significant impact on linguistics.

Starting in the 1950s, Noam Chomsky sparked the “cognitive revolution” by showing that the study of language could help us to understand human cognition as a whole. But whereas Chomsky focused on syntax, other linguists, such as George Lakoff, gradually came to regard metaphor, and hence semantics, as more central to human language faculties. In 1980, he and co-author Mark Johnson published a book called Metaphors We Live By in which they set out this theory of conceptual metaphor in detail and thus founded the field of research now known as cognitive semantics.

Metaphors were long regarded as purely linguistic constructs, but in cognitive semantics, they are instead regarded as conceptual constructs that have some fundamental effects on the way we think. For cognitive semanticists such as Lakoff, any conceptual system that we use for thinking every day is metaphorical, and non-metaphorical thought is possible only when we are speaking of purely physical entities. And the more abstract something is, the more levels of metaphor we need to express it.

Moreover, according to Lakoff, these metaphors are largely unconscious and hard to detect, because they are often too distant from their origins or too embedded in our language for us to even notice them. For example, when you think about it, the most common metaphor for an intellectual debate is a war: if you were a debater, you might characterize your opponent’s position as indefensible, then attack it violently until you had destroyed it, at which point you would hope that the judges would declare that you had won.

Another good example of the effect of metaphor on cognition is the widespread use of the expression “the tax burden” in the mass media. Now that this metaphor has become so firmly established, regardless of the intentions of the writer who uses it, it tends to reinforce the idea that taxes are something that weighs heavily on the backs of taxpayers. The mass media may thus influence public opinion in favour of privatization—a result that probably does not displease the financial interests with which these media are often so closely linked.

Lakoff believes that the development of thought within societies has always been influenced by the way that metaphors have been used. He also believes that the application of one field of knowledge to another has often provided new perspectives and new understanding precisely because it has generated new metaphors.

Indeed, the way that metaphors work is by enabling us to understand one domain in the terms of another. For example, when we say “time flies”, we are using a concept related to space (the source domain from which we draw the metaphor) in order to understand time (the target domain that we wish to understand).

The other major intuition of cognitive semantics is that all human cognition, including even the most abstract reasoning, is embodied. In other words, cognition uses and depends on basic bodily phenomena such as the sensorimotor system and emotions (follow the Tool Module link below).

This embodied conception of cognition thus rejects not only mind/body dualism but also the very idea that human cognition could be understood without reference to the details of how it functions at the neural level.

In short, in Lakoff’s view, because the human brain is so intimately linked with the human body, its form, and the way it functions, the metaphors that emerge from this brain must necessarily be based on this body and its relationship to the world. And for Lakoff, it is precisely from these metaphors that we form the concepts that let us think about this world.

Lakoff’s ideas have had significant impacts on epistemology, including the very principle of disproving hypotheses that is so central to the scientific method. For Lakoff, the hypotheses that we construct with the help of complex metaphors cannot be directly disproved. They can only be rejected following empirical observations that are themselves guided by other complex metaphors.

George Lakoff is also known for his progressive political analyses and for the theses that he and Rafael Núñez have developed regarding the embodied origin of mathematics. According to Lakoff and Núñez, mathematics, far from being a tool that predates human nature, in fact constitutes a human conceptual system that is bound by biological constraints, such as the facts that we have frontal binocular vision, that we walk in the direction of our field of vision, and that we have certain specific mechanisms for proprioception.

Chercheur : George LakoffLien : "Philosophy In The Flesh": A Talk With George LakoffLien : George Lakoff: PHILOSOPHY IN THE FLESH (Basic, 1998)Outil : Cognition et Émotion : deux concepts distincts pour deux réalités distinctesLien : Conceptual metaphorLien : Cognitive semanticsChercheur : Mark L. JohnsonChercheur : Rafael Núñez: explorateur de l’infini mathématique
Chercheur : Rafael NúñezLien : MATHEMATICAL IDEA ANALYSIS: WHAT EMBODIED COGNITIVE SCIENCE CAN SAY ABOUT THE HUMAN NATURE OF MATHEMATICSLien : Center for the Cognitive Science of Metaphor OnlineOutil : La grammaire universelle de Chomsky dans l’encadréLien : MétaphoreLien : MetaphorLien : George Lakoff books

From the enactive perspective, if machines are ever to become “intelligent”, they will have to be designed to operate as autonomous agents in an actual physical environment —in other words, designed from the bottom up and not from the top down, as in the cognitivist paradigm. This approach is called situated robotics, a research area first developed in the 1980s by Rodney Brooks in a major departure from traditional robotics research based on a cognitivist artificial intelligence (AI) model.

Brooks applied two basic principles to his robots. First, rather than satisfying abstract criteria for action, they had to be immersed in and interact with the real world. Second, they had to be “embodied”, meaning that they literally had to have physical bodies that let them perceive the world and act on it, but without ever forming complete representations of this world or of their actions.

At first, the academic community had much trouble in accepting Brooks’s approach, because it contradicted years of effort in traditional AI research. For example, Brooks said that to enable a robot to move along a wall, there was no need to write a complicated program. Instead, one could simply equip the robot with a device that detected the wall, and design the robot so that it always had a slight tendency to advance toward the wall, but also tended to veer slightly away from the wall once it detected that it was close. If these two tendencies were balanced correctly, then the behaviour of moving along the wall would emerge from the robot naturally.

In fact, proponents of embodied cognition even argue that all of our human cognitive faculties may have their source in mechanisms of this same kind.

Lien : Situated RoboticsLien : Rodney Brooks : Books & MoviesLien : Situated roboticsChercheur : Rodney A. Brooks
Lien : Autonomy and CognitionLien : Recension du livre Flesh and Machines de Rodney A. BrooksLien : Fast, Cheap and Out of ControlLien : Fast, Cheap and Out of Control


Seminar (Philosophy 6593): Mental Subsystems and the Construction of ContentChristof Koch  Lecture 9: Attention and ConsciousnessChristof Koch   Lecture 10: The Neuronal Underpinnings of AttentionChristof Koch  Lectures on Consciousness
Le mécanisme de concentration du cerveau expliqué grâce au singeSeparate brain areas rule concentration and distractionPaying Attention to ConsciousnessRENCONTRES FRANCOPHONES SUR L'APPROCHE SCIENTIFIQUE DE LA CONSCIENCE
ON THE ORIGIN OF CONSCIOUSNESS A POSTULATE AND ITS COROLLARYON THE ORIGIN OF CONSCIOUSNESS A POSTULATE AND ITS COROLLARYConscious, preconscious, and subliminal processing: a testable taxonomyState of the Art - The Psychology of Consciousness
ConsciousnessWhy visual attention and awareness are differentEssential  Sources in the Scientific Study of ConsciousnessL'attention visuelle: une sorte de stroboscope
Brain Rules: AttentionMolecular and Biophysical Mechanisms of Arousal, Alertness, and AttentionOur somatosensory cortex embodies the facial expressions of others
Michael PosnerMary RothbartA 3D animation depicting the early molecular events underlying long term potentiation in the spinal cord of pain pathways
A Website devoted to Scientific Research on Human Multi-task Performance and Attention Limits

Who’s in Charge—Us?

The metaphor often used to discuss attention, whether initiated from the bottom up or from the top down, is that of a searchlight sweeping across the landscape with a beam of light that may be relatively wide or relatively narrow. But some authors, such as Christof Koch, say that it would be more accurate to compare attention to the various stage lights that do not sweep across everything in their path but instead illuminate one point, then go out, then light up another point somewhere else.

Our perception of the world around us depends first of all on what our senses are capable of detecting (for example, bees can see ultraviolet light, but human beings cannot). Next, our perception depends on the attention circuits in our brains, which decide what stimuli to give priority to, applying either bottom-up or top-down mechanisms (see main text opposite). And it is only what passes through these two filters that we can consciously perceive.

We learn a whole lot of things without realizing it. This is called implicit learning. The following experiment demonstrates this phenomenon. Suppose that there are six locations that can light up on a display screen, and six keys on a keyboard that match these locations spatially. When one of the locations lights up, the subjects’ task is to press the corresponding key. What the subjects don’t know is that these locations are changing according to a specific set of rules. Without being consciously aware of these rules, the subjects learn them implicitly, because their response times improve more than they do when the locations that light up change randomly.

As this experiment shows, our brains are constantly trying to structure the world around us, but in doing so they must work with perceptions that are influenced by all sorts of experiences that we have had unconsciously or implicitly in the past. That is why, for example, we tend to see what we have seen before and to act in the same way that we have always acted. Collectively, this mechanism probably contributes to a people’s “national character”, their collective memory, and their common cultural behaviours.

Munakata’s experiment on how 3-year-old children learn to follow new rules clearly shows that the quality of their mental representations may not be completely solid.

In this experiment, children were given a deck of cards, some bearing pictures of trucks, others pictures of flowers. In both cases, some of the pictures were red, while others were blue.

In the first task, the children were asked to sort the cards by colour, the blues to the left and the reds to the right. The children performed this task successfully.

Next, the children were told that they were now going to play the shape game instead of the colour game, and that the rule had now changed so that their task was to sort the trucks to the left and the flowers to the right. When the children came to a card with a red truck on it, they mistakenly sorted it to the right, as they would have in the colour game.

The crucial point is that when the children were asked explicitly where they were supposed to place the trucks, they answered correctly and pointed to the left. But if they were given a card with a red truck again, they again placed it to the right. In this experiment, the quality of the representations of the task that the children had developed was still fragile. They could respond properly to questions that called on only one dimension at a time, but not to stimuli where colour and shape conflicted.

Because human beings can express the contents of their consciousness through language, there is the temptation to equate consciousness with language. But in fact, consciousness does not seem to owe its existence to language. For example, there are many human beings who cannot speak (such as babies, or people who are mute, or people who suffer from aphasia), but nobody questions whether these people experience conscious states. Scientists have also studied the neural correlates of consciousness in many non-human primates.

However, some authors believe that language, and more particularly “interior language” (or the phonological loop), may refine or augment a consciousness of self that is already present. This question is complex, however, and remains the subject of much debate.

Lien : Consciousness and Language by John Rogers SearleLien : Conscience de soi et langage intérieurLien : Animal Communication
Lien : Francis Kaplan : Variation sur le propre de l'hommeLien : Entretien avec Francis Kaplan

Consciousness is constantly passing from one state of organization to another. Much of its activity can thus be described as chaotic, from both a phenomenological and an electrical standpoint. Scientists must therefore use tools of non-linear mathematics to describe these stable states that alternate with destabilizations. The most obvious example is the alternation between sleep and wakefulness. Another example is the alternation among moments when our attention is focused, moments when it is shifting, and moments when we are not paying any attention at all. Because if consciousness is still a big mystery, so is the absence of consciousness when we are awake but have our heads “in the clouds”!

Lien : Wandering Minds: The Default Network and Stimulus-Independent ThoughtLien : Escape from the Insipid: Our Brains May Be Wired for Daydreaming

The Brain’s Default Network


The idea that we are fully conscious of the world around us has been discredited by a multitude of experimental data. These data indicate that our environment is far too rich and complex for our nervous systems to process all of the information from it continuously in real time. Whereas the classical model of consciousness proposes that we are conscious of the entire world around us, in reality we pay attention to only a tiny proportion of our environment, while ignoring the rest.

Because of our limited cognitive abilities, evolution appears to have favoured the emergence of two complementary types of mental processes: attentional processes and unconscious processes. The phenomena of consciousness, attentional processes, and unconscious processes have all arisen from the same need: to facilitate effective action in a complex environment.

First, let us consider the attentional processes that are so intimately connected with consciousness. We know that attentional processes existed far back in the evolutionary past, because they have been detected even in flies. Some scientists even believe that consciousness itself may be nothing more than an extension of the attention mechanism associated with working memory. Michael Posner and Mary Rothbart, for example, find it reasonable to hypothesize that phylogenetically speaking, our conscious functions developed from the attention mechanism.

Indeed, it seems quite plausible to say that when some ancient predator first noticed a prey animal, then focused all of its attention on it, that predator had just taken its first step toward conscious thought. And that first step was most likely followed by a second, in which the predator engaged in some rudimentary reasoning involving various internal and external stimuli and then either triggered or inhibited a movement to capture the prey.

One thing is certain: there are many theories about attention, but all of them say that we are attentive to something when we select it. Attention occurs when we focus on a certain stimulus by being more sensitive to it than we are to others. Our attention may thus be spatial, or based on a property of an object, or a type of object, etc.

For example, suppose you are watching TV, and you are also vaguely aware of the sound of a conversation in the next room, the noise of a fan, and the smell of bread in the toaster. But then suppose the toast gets stuck in the toaster and starts to burn. You will unconsciously attribute a meaning of danger to that smell, then shift your attention to it abruptly.

The corollary to this selective aspect of attention is that when you pay attention to one thing, you automatically ignore a lot of others. Our human attention resources are limited, and it is hard for us to allocate them to more than one object at a time. If you try to pay attention to two complex tasks simultaneously—for example, driving in rush hour while negotiating a contract over your cell phone—you will necessarily neglect one or the other, very likely with negative consequences in either case.

If you ever read the written transcript of a conversation, evidence of this same phenomenon will leap off the page: you’ll be surprised at the number of pauses and “ums”, because when you’re involved in a conversation yourself, you simply ignore these things. The same process explains why it’s so hard to find errors in a text that you’ve written yourself: your attention is so focused on what you’re trying to convey that you overlook minor misspellings.

Thus, the only stimuli that reach our consciousness are those that we have selected as worthy of attention. If anyone is still skeptical that this is the case, a phenomenon such as inattentional blindness (see box below) will generally manage to convince them.

Attention also comes into play when a task or a stimulus requires special processing. In such cases, attentional processes may be required in order to hold certain data in memory, to discriminate between two similar stimuli, to anticipate certain events, to plan a course of action, or to co-ordinate various behavioural responses so as to achieve an objective.

Attentional processes are therefore more specific than wakefulness or awareness. Wakefulness and awareness are preconditions for attention and depend on more general processes arising from the activation of diffuse neural systems in the brainstem, such as the norepinephrine system in the locus coeruleus.

Neuroscientists also frequently distinguish two different kinds of attention mechanisms. The first is initiated from the bottom up, that is, by neuronal signals from specialized processing modules whose job is to detect and process stimuli. These signals then trigger a global activation of the neural control networks.

The archetypical bottom-up attention behaviour is the orientation reaction: sensory organs such as the eyes or the ears detect a new stimulus in the environment, and the entire body then turns toward this stimulus to learn more about it. This reaction explains why it is so hard to look away from the TV screens in sports bars or airport waiting areas: the changing images on the screen are constantly drawing your attention.

When the initial stimulus is visual, our bottom-up attention responses depend on a network of interconnected areas of the brain that include the parietal lobe, the pulvinar and the superior colliculus.

The second kind of attention mechanism operates from the top down, such as when the neural control networks execute an action that is motivated by a goal. Our thoughts, motivations, perceptions, and emotions then become available to consciousness when we pay attention to them.

Top-down attention mechanisms are what let you read in
noisy surroundings.
Top-down attention mechanisms come into play, for example, when you consciously decide not to pay attention to something that is very attractive (such as the TV screen in the airport or the people around you in a club) so that you can concentrate on something else (such as the book you’re reading). Top-down attention mechanisms are also what enables you to continue pretending to read while actually concentrating your attention on an interesting conversation going on nearby.

This ability for attention to be an active phenomenon has also been well demonstrated in experiments where the subjects were required to press a button as soon as a visual target lit up. These experiments showed that the subjects’ reaction time was faster when they were shown an indication of where the target was going to light up shortly before it did so. And when they were shown an intentionally misleading indication, their response time was slower than when they were given no indication at all. These results clearly show that our expectations influence our perceptions, or, in other words, that attention can be a mental process directed from the top down.

Lien : Mask Illusion

In short, we live in a complex environment where stimuli from all directions make claims on our attention, but our attention focuses only on those stimuli that are new or already have some meaning for us. We may think that we are conscious of the entire scene around us, but that is indeed an illusion, as phenomena like change blindness clearly demonstrate.

It is therefore a trap to accept the standard, naïve, realist view of the world around us as a place where “objective reality” is composed of objects whose characteristics are independent of our senses. The projective nature of perception means that the content of our consciousness—each individual’s psychic reality—is greatly influenced both by biological predispositions and by learning, both of which are projections of the distant or recent past onto the present.

A visual scene that you have not yet explored is equivalent to chaos, or, in more modern language, to “latent information”. It is your brain that immediately projects a meaning onto the scene, establishing order within it. And the processes by which your brain decides which lines and surfaces go together to form particular objects, such as the cubes of cheese in the photo to the right, are entirely unconscious. In other words, the attentional processes that lead to consciousness are applied not to a reality that exists completely outside of us, but rather on the basis of our preconceptions and remembered forms that we project onto our environment. That is why all of our perceptions can be regarded as constructed—a fact that is the basis for many optical illusions .

When you look at a complex image like this one, you don’t see an undifferentiated mass of disjointed lines and surfaces, but rather a pile of separate, three-dimensional cubes of cheese.

We therefore cannot speak of consciousness and attentional processes without also considering the extensive unconscious activity that is going on in our brains at all times. On the one hand, attention plays a fundamental role in learning by amplifying the important representations that enable us to take appropriate actions at any given time. But on the other hand, by thus increasing the quality of certain mental contents, learning increases the likelihood that a given piece of mental content will be at the centre of the attentional processes of our subjective consciousness sometime in future. That is why many people believe that the true relationship between the self and the world is one of reciprocal engendering.

Many experimental findings support this description of consciousness in terms of quality of representation (see sidebar concerning Munakata’s experiment). From this standpoint, the quality of representations is therefore a continuous variable, a continuum that allows a gradual transition from the unconscious to the conscious. This quality gradient between unconscious and conscious, which is shaped by learning, also suggests that the corresponding representations depend on the same underlying processes, rather than on two distinct neural systems.

But although learning, by increasing the quality of a stimulus, can facilitate its access to consciousness, recurrent consciousness of a stimulus can paradoxically return it to the realm of the unconscious, through habit or automaticity. We can therefore describe consciousness (or the realm of the explicit) as a peak between two domains of lesser consciousness in which the two extremes would be two very different types of unconscious.

  1. In the first type of unconscious, the quality of the representations is too low to enter consciousness. Like fish that are too small and get thrown back into the water, these stimuli do not reach consciousness. They remain unconscious, but this does not mean that they cannot affect our behaviour.

  2. In the second type of unconscious, the quality is so high that it enables the representations to be expressed all on their own, unconsciously, because they are so well engrained in our memory.

This transfer from the conscious to the unconscious clearly comes into play in the learning of motor skills, such as how to ride a bicycle, or ice skate, or tie your shoelaces. In the beginning, everything is conscious and laborious, but as you practice, it all becomes automatic and unconscious. In a process of automatization such as this, our conscious experience is diminished as we gain in expertise.

But the opposite can also happen, when we try to master the fine distinctions that characterize a particular field of knowledge, such as oenology or philosophy. In this case we are no longer engaged in procedural learning, but rather in explicitly expanding our knowledge in a particular field. And the more we learn about the complexity of this field, the more conscious we become of new distinctions that make it even more rewarding.

We can therefore distinguish three different possible situations involving two different characteristics of knowledge: its availability to our consciousness and our ability to control our conscious representation of it. When both availability and controllability are low, this knowledge is implicit (unconscious). When both availability and controllability are high, this knowledge is explicit (conscious). And when availability to consciousness remains high but controllability drops back to a very low level (as the result of habit or automaticity), then the knowledge is said to be automatic.


If you aren’t expecting to see something at a given time, you may not see it at all, even if it’s something big.

This curious phenomenon is called inattentional blindness, and there’s no better way to discover it than to experiment on yourself. To do so, click on the link at the end of this paragraph. It will take you to a video that shows two basketball teams. The three players on one team are wearing black, and those on the second team are wearing white. You must count the number of passes made by the players in white. This task is made harder by the fact that the players in black are passing a second ball around in the same space. Go ahead, try the experiment before you read on.

Lien : Inattentional Blindness

Now that you’ve watched the video, here are not one but two questions: how many passes did the players in white make, and what was the gorilla doing?

What was the gorilla doing? In actual experiments, this second question leaves more than half of the subjects at a loss, because they never saw any gorilla at all while they were watching the video. And yet, when they watch it again, this time without their attention being directed toward the white team, they see something really strange: someone dressed in a gorilla suit walks into the space where the players are passing basketballs around, stops, turns toward the camera, thumps his chest, then calmly walks out the other side of the frame! (If you didn’t see this the first time, run the video again, and see whether you do now.)

How come only about half of the subjects in the actual experiments noted the incongruous presence of the fake ape? Though the explanation is relatively simple (the subjects’ attention was focused elsewhere), the phenomenon of inattentional blindness is still surprising, to say the least, and raises serious questions about the idea that we have a total consciousness of the world around us. On the contrary, this experiment shows that the world is too complex for us always to have a detailed awareness of it, and that numerous attentional and unconscious processes are at work in our brains.

There is not “a” consciousness, but rather many levels of consciousness, a continuum of intermediate states. But this continuum also contains a dichotomy: because of the sequential nature of consciousness, a given representation at a given time either is conscious or is not. Just as the gradual and continuous changes in the temperature of a mass of water are accompanied by a sudden change in state at 0°C (when the water becomes solid) and at 100°C (when the water becomes steam), the degrees of unconsciousness may thus vary up to an activation threshold past which the representation suddenly enters into the realm of consciousness.

Consciousness may thus be similar to what physicists call a “phase transition”: a sudden transformation that occurs on a large scale following numerous microscopic changes. One example of a phase transition is the emergence of superconductivity in certain metals when they are cooled to a certain critical temperature. It is not surprising, then, that the concept of emergence is frequently invoked to describe the appearance of consciousness.


Conscience et cerveauDr Susan Blackmore tells us about human consciousnessWhat the Best Minds Think about the Brain, Free Will, and What It Means to Be Human  Susan BlackmoreMoving Forward on the Problem of Consciousness
Le problème de la conscienceA Neurobiologist Gets Introduced to EliminativismSCIENCES COGNITIVES ET CONSCIENCEModels of Consciousness
Video : Les origines de la conscience réflexiveThe two faces of consciousness. On Susan Blackmore “Consciousness: An Introduction“Consciousness, by John SearleConsciousness & The Brain : Anotated Bibliography
THE CONTENTS OF CONSCIOUSNESS: A NEUROPSYCHOLOGICAL CONJECTUREIs There Room for the Soul? New challenges to our most cherished beliefs about self and the human spiritThe Rediscovery of the Mind
Joëlle Proust
Original modules
Tool Module: Brain ImagingBrain Imaging

Ludwig Wittgenstein believed that philosophical problems needed to be addressed not so much with solutions as with therapies that revealed the underlying confusion from which they sprang. As he described the purpose of philosophy, “We must show the fly the way out of the fly-bottle.” That’s why it’s so important to keep alert to other points of view, just in case the problem lies with your formulation, and not with the actual reality that you are trying to understand— probably a good idea to keep in mind if you are studying consciousness!


The development of the cognitive neurosciences in the late 20th century enabled the first empirical models of human consciousness to be developed. Subsequently, many researchers have refused to accept the existence of a “hard problem” of consciousness that would preordain the failure of any attempt to model consciousness on the basis of neurobiological data. For these researchers, this “hard problem”, which refers to the subjective aspect of consciousness, comprises a multitude of more concrete problems, such as how the brain accesses information, integrates sensorimotor functions, or controls executive functions (attention, anticipation, planning, learning of rules, abstract thinking, etc.).

Today, thanks to new technologies such as brain imaging (follow the Tool Module link to the left), each of these phenomena can be subjected to experiments that the neurobiologists of the early 1980s could never have imagined. The findings of such experiments are gradually shedding light on these problems and tending to invalidate certain models of consciousness that are no longer consistent with the experimental data.

This cartoon by Saul Steinberg, published on the cover of
The New Yorker on October 18, 1969, vividly depicts the human “stream of consciousness”: an endless succession of items that come to our attention, and then are sometimes encoded in memory, but other times forgotten forever.

As a result, attempts have been made to develop new models that incorporate these data on the brain’s anatomy and function and integrate them into a coherent whole that explains the various aspects of our conscious processes. The following paragraphs briefly describe some of these neurobiological theories of consciousness. Many of these theories have some concepts in common, which the most optimistic of their authors believe points to the beginnings of an overall explanation of how the brain goes about “producing” consciousness.

CONSCIOUSNESS EXPLAINEDPhilosopher Dan Dennett on consciousnessTIME AND THE OBSERVER: THE WHERE AND WHEN OF CONSCIOUSNESS IN THE BRAINAre we explaining consciousness yet?
Publications by Daniel DennettIs Perception the "Leading Edge" of Memory?Quining QualiaStage Effects in the Cartesian Theater: A review of Daniel Dennett's Consciousness Explained
Daniel C. DennettDaniel C. DennettDaniel C. DennettDaniel Dennett - the intentional stance
Original modules
Tool Module: Neural DarwinismNeural Darwinism

As phenomena such as change blindness demonstrate, we are not conscious of so many things as we think we are. Philosopher Daniel Dennett had already predicted the existence of this phenomenon back in the early 1990s, long before experiments had provided the spectacular examples of it that we know about today.

That is why Dennett considers introspection such a bad starting point for any attempt to understand consciousness. Our immediate subjective access to our own consciousness makes us think that we can know its workings directly but masks its true nature, which is proving more and more counterintuitive.

Dennett does not categorically deny the insights that the first-person perspective can offer, through the practice of meditation, for example. But he would like it if everything that was discovered from this first-person viewpoint could then be validated by neutral observers— in other words, from the third-person viewpoint—by the scientific method. From this stance comes Dennett’s concept of hetero-phenomenology, which comprises not only what a subject reports about his or her conscious experience, but also the data that can be gathered concerning the subject’s brain and the subject’s immediate environment.

We generally sense that the winning interpretation of a conscious state arises from the Darwinian competition that plays out among its many unconscious versions. But sometimes we get a glimpse of this subliminal struggle - for example, if you are walking through a snowstorm, and see a person’s silhouette, but as you draw closer, you suddenly realize that a rival interpretation has taken its place, and that what you are really seeing is an oddly pruned apple tree.

Outil : Le darwinisme neuronal

Daniel Dennett has been greatly influenced by evolutionist thinkers such as Richard Dawkins, who introduced the concept of “memes” and who, like Dennett, staunchly criticizes creationism.

Chercheur : Richard DawkinsLien : Breaking the Spell

Daniel Dennett is a philosopher, but probably one of the philosophers who are trying the hardest to integrate the findings of neuroscience into their conception of consciousness.

Dennett wants to put an end to what he calls Cartesian materialism, a position that rejects Cartesian dualism but accepts the idea of a central (though material) theatre from which consciousness springs. To escape from this Cartesian materialism, Dennett proposes two metaphors that he considers more consistent with the neuroscientific data: “multiple drafts” and the “virtual machine”.

For Dennett, there is no little homunculus inside the human brain, no little “self” sitting in front of the theatre of consciousness and observing or even directing the spectacle before it. In his multiple drafts model, consciousness is not a unitary process, but a distributed one. At any given time, several concurrent neuronal assemblies are activated in parallel and competing with one another to be the centre of attention—to be “famous”, as Dennett puts it. The conscious self is therefore nothing more than “fame in the brain”, fragile and changing like any other ongoing reconstruction.

Thus, the result of this competition is not an “average” of the various drafts, but rather the success of the one that is the most effective in and best adapted to a given situation. What Dennett is positing here is a process of selection similar to what Edelman has called “neural Darwinism” (follow the Tool module link).

According to Dennett’s multiple-drafts model, a given piece of conscious content arises from a rapid succession of events in the brain whose order in time cannot be determined. Various neuronal assemblies distributed throughout the brain respond to the various properties of an object (during an interval of about one-fifth of a second). Consequently, the answer to the question “When did I become conscious of such-and-such an event?” can only be vague, never precise. The following diagram attempts to illustrate this point.

The first thing that the brain detects is simply that something has happened. Next, the brain determines that this something is located toward the left, and that it is a circle. The brain then detects that the circle is blue, and finally binds all these elements together and determines that the object is a blue circle to the left. There is no way of determining precisely when the brain became conscious of this blue circle, because each of its characteristics has been detected a few hundredths of a second before or after the others.

According to Dennett’s model, with these multiple drafts in constant competition, the single, conscious narrative flow so familiar to all of us and depicted in the Steinberg cartoon above can only be an illusion, just like the Cartesian theatre. To explain this illusion, Dennett posits the existence of a virtual machine that runs in serial fashion on a “hardware platform” that operates in massively parallel fashion—i.e., the human brain. This virtual machine would be a sort of mental operating system (like Linux or MS-DOS), capable of transforming the inner cacophony of the brain’s parallel activity into a conscious, serial narrative flow. It is this virtual machine that would enable us to think about our own thoughts and engage in deliberations with ourselves.

Unlike the behaviourists, Dennett thus does not dismiss what each of us may subjectively report about our emotions, feelings, or mental states. But he does not grant these reports any special status either. He regards them as real data, but as data concerning the way that people feel things, and not about how these things actually are (see sidebar on heterophenomenology). For Dennett, the task clearly becomes to understand how this illusion is generated.


Dennett thinks that many people do not want to consider explanations about consciousness, just as many people do not want to hear explanations of magic tricks. To such people, the aura pf mystery surrounding the “hard problem”of consciousness seems impenetrable. But Dennett says their error begins when they conceptualize “the hard problem” as a single problem and consciousness as a single thing.

To explain what he means, Dennett uses the example of a famous magician who showed his colleagues a card trick that he called “The Tuned Deck”. A volunteer chose a card from the deck, noted which card it was without telling the magician, then returned it to the deck. The magician then held the deck close to his ear, riffled the cards, and successfully identified the volunteer’s card, claiming that he had done so by listening to the tiny variations in the sounds of the individual cards. His colleagues thought that they had figured the trick out, so they asked him to repeat it, and he obliged. Fooled once more by the trick, but still doubting how he had really done it, they had him to do it again, and once again, they experienced the same perplexity together with the same vague feeling that they had figured out the subterfuge.

At the end of his life, the magician revealed his secret to his colleagues. The trick was simply the name of the trick: “The Tuned Deck”, and more specifically the word “The”. By using this word, the magician implied that he was performing a single trick, but in fact, every time he found the volunteer’s card, he was using a different method. And his colleagues were familiar with all of these methods, because identifying a card chosen by a volunteer was a classic trick that could be performed in many different ways. But the other magicians never identified their colleague’s methods, because they were too busy looking for a single trick.

And that, says Dennett, is exactly what happens with “the” hard problem of consciousness. We remain in the dark, because consciousness is a whole set of “tricks”, and no one of them constitutes the solution all on its own. The solution consists of all these tricks taken together . The error with consciousness is the same as with the cards: imagining that there is one specific problem beyond the numerous “tricks” that our consciousness performs.

And the same thing goes for qualia, about which Dennett is no more sparing. He describes them as the residue that is left after one has explained whatever there was to explain about perception, for example. In other words, the error here lies in continuing the analysis without realizing that one has already completed it and that there is nothing more to analyze. Or stated yet another way, the error consists in seeing insurmountable problems in a fairly ordinary fact: that any subject is inexhaustible. Even for a single grain of sand, once everything has been said that there is to say about it, there will still always be something that has not been said—about its history, for example.

Lien : Philosophical Obstacles to a Science of Consciousness
The concious access hypothesis : origins and recent evidenceBiologie et conscienceGlobal Workspace Theory: An interview with Bernard BaarsIn the theatre of consciousness. Global Workspace Theory, a rigorous scientific theory of consciousness
Understanding Subjectivity: Global Workspace Theory and the Resurrection of the Observing SelfJournal of Consciousness StudiesScience & Consciousness ReviewIN THE THEATRE OF CONSCIOUSNESS. Global Workspace Theory, A Rigorous Scientific Theory of Consciousness
The Role of Consciousness in MemoryConsciousness (William P. Banks and Ilya Farber)The foundation of cognitive scienceLIDA: A Computational Model of Global Workspace Theory and Developmental Learning
CONSCIOUSNESS AND COGNITIONThe neurophysics of consciousnessIs There Room for the Soul?Metaphors of consciousness and attention in the brain
The global brainweb: An update on global workspace theoryThe brainweb: phase synchronization and large-scale integrationChangeux : cerveau, mode d'emploi
Bernard Baars

Playing a variation on the theme of the hard problem versus the easy problems of consciousness, philosopher Ned Block developed what has become a classic distinction between “phenomenal consciousness” and "access consciousness".

Phenomenal consciousness is the kind addressed by question such as “what it is like to be a bat”, or a human being. It is this qualitative aspect of our mental states that poses a problem for Block (“Why are the neurobiological bases of certain subjective experiences precisely the ones they are and not something else?”) but not for Dennett (see the sidebar above).

On the other hand, a representation is conscious, in the sense of access consciousness, if and only if it is sufficiently distributed within a cognitive system so as to be freely used in reasoning. We are thus dealing with something fairly close to the global workspace model proposed by Baars.

The global workspace model is compatible with two phenomena that are much discussed by students of the neurobiological bases of consciousness: the probable “binding function” (the subject of the “binding problem”) and the concept of an “interpreter” , which comes from Michael Gazzaniga’s research on “split brain” patients.

With regard to the binding problem, the temporal synchronization of neuronal oscillations is often cited to explain how numerous specialized subsystems pool the results of their work. With regard to the interpreter concept, the interpreter would be the function that makes “public” the unconscious work done by a multitude of independent agents.

Expérience : Ce que nous révèlent les cerveaux divisés sur le langage

The theories that invoke the concept of a global workspace date back to the work done by Alan Newell and Herbert Simon in the cognitive sciences in the 1960s and 1970s. Newell and his colleagues were the first to show the usefulness of a global workspace in a complex system composed of specialized circuits. By providing a place to pool the information that each of these circuits had processed, this workspace would allow problems to be solve that no one of them could have solved on its own.

That in short is the great principle of the global workspace, which scientists have continued to apply and enhance ever since. In fact, most neurobiological models of consciousness incorporate some aspects of the global workspace concept. Examples include Gerald Edelman’s “global cartography”, Rodolfo Llinas’s mechanism of global synchronization from the thalamus, Antonio Damasio’s cortical convergence zones, Daniel Schacter’s “conscious attention system”, Francisco Varela’s “brainweb”, and the model of Jean-Pierre Changeux and Stanislas Dehaene, who make the neuronal workspace their primary hypothesis.

But ever since the 1980s, it is Bernard Baars who has been the strongest proponent of this model, which attempts to answer the famous question: how can a phenomenon such as consciousness, in which everything happens in series, with only one conscious object at a time, emerge from a nervous system that basically consists of countless specialized circuits that operate in parallel and unconsciously? Baars’s answer: by having a workspace where the information processed by these specialized circuits is made accessible to the entire population of neurons in the brain.


Source: Dehaene and Naccache (2001)


Baars thus suggests that there is a close connection between global availability of information on the one hand and consciousness on the other. In his view, this global accessibility of information, made possible by a global workspace, is precisely what we subjectively experience as a conscious state. The “easy problems” and the “hard problem” of consciousness are thus here regarded as two different sides of the same coin.

The global workspace is a process that involves first convergence and then divergence of information. Baars thinks that this process can best be understood through the metaphor of a theatre stage where attention acts as a spotlight cast on certain actors. These actors represent the content of consciousness selected by competition among specialized circuits. What we have here is a Darwinian selection process by which certain actors (pieces of conscious content) become “famous” for a fleeting moment. During that moment, this conscious information is disseminated or made accessible to the vast audience of unconscious circuits that fills the theatre.

Baars argues that this way of formulating the theatre metaphor does not make it what Dennett calls the “Cartesian theatre” and criticizes so harshly. Indeed, the Cartesian theatre has always been predicated on the existence of a single point, such as the pineal gland identified by Descartes himself, where everything is brought together within a “self” that receives the conscious thought or perception—almost as if there were only one spectator in the audience watching the entire stage.

In contrast, in Baars’s theatre metaphor, a multitude of entities, all of which remain unconscious, have access to a particular piece of information at the same time. Baars thereby not only avoids the problem of regression to infinity, but also offers a straightforward definition of consciousness as this in-depth exchange of information among brain functions, each of which is otherwise independent of the others and unaware of what they are doing.

The idea that consciousness has an integrating function makes it easier to understand several of the human brain’s capabilities, including working memory, learning (both explicit episodic and implicit), voluntary motor control, selective attention, and so on.

Many of these capabilities show up as integral parts of Baars’ theatre metaphor, when you get into the details. The spotlight of attention determines what place on the stage will be illuminated and therefore conscious. The stage as a whole represents the content of working memory that is immediately accessible to be picked out by this spotlight. The part of the stage that is in the “glare of the spotlight” will be seen, or, if you prefer, distributed to the unconscious audience seated in the semi-darkness, while other unconscious craftspersons, working behind the scenes, influence the course of the performance by associating a particular context with it.

Baars reminds his readers that the purpose of these details of the theatre metaphor is not to “explain” consciousness, but to provide tools that can be used to organize the existing data, to clarify certain concepts, and to formulate testable hypotheses, in particular the involvement of certain structures in the brain, so as to better understand this complex phenomenon.

Lien : L’homme neuronal en perspectiveLien : Stanislas Dehaene (CDF) , Vidéo L'imagerie cérébrale et la transition dynamique du non-conscient au conscientLien : Consciousness Research at UNICOGLien : Jean-Pierre Changeux, Paul Ricoeur - Ce qui nous fait penser. La nature et la règle
Lien : Livre : La nature et la règle - Ce qui nous fait penserLien : L'imagerie cérébrale révèle les mécanismes du passage de l'inconscient au conscientLien : Review of What Makes Us Think? by Jean-Pierre Changeux and Paul RicoeurLien : L’homme neuronal
Lien : L’Homme de Vérité. Jean-Pierre Changeux. Paris: Odile Jacob; 2002Lien : Silent Minds
Chercheur : Stanislas Dehaene

Simulations have shown that a global workspace based on the thalamocortical circuits and on long corticocortical connections behaves like a non-linear, self-amplified dynamic system.

One of the characteristics of such a system is that it has a threshold above which an activation propagates explosively across the entire network. In contrast, an activation slightly below this threshold (such as a subliminal activation) damps itself out very rapidly.

Another characteristic of such a system is that it can inhibit other activations within this same global workspace, thus preventing rival stimuli from being processed consciously. Such inhibition is seen in the phenomenon of the “attentional blink”, in which, for a short time after we are presented with one stimulus, we cannot detect a new one.

Lastly, the dynamics of access to consciousness are an abrupt, “all-or-nothing” phenomenon: when the visibility of a stimulus is increased gradually, it “appears” in consciousness suddenly. The global workspace model may account for this threshold effect by means of the connections from the neurons in the workspace back to the primary and secondary sensory areas.

Lien : Attentional blinkLien : Attentional BlinkLien : Attentional Blink
Lien : Attentional BlinkLien : Un modèle d'espace conscient étudié avec des tâches cognitives et des souris génétiquement modifées

Some authors agree that talking about a conscious workspace probably represents some progress over the idea of consciousness that prevailed in the mid-20th century. But others think that this idea is some like the earlier notion of the “dormitive virtue” of opium, which provided no information at all about the underlying mechanisms by which opiates affect the brain.

What then does this global workspace consist of, in concrete terms? If it is a set of neural pathways that interconnect the various parallel processors in the brain, then which pathways are they? And what determines whether the activation of any given set of neurons will be propagated into the global workspace?

Many neurobiologists, including Jean-Pierre Changeux and Stanislas Dehaene, are conducting research programs to attempt to answer these questions. Changeux and Dehaene start from the premise that the brain does in fact contain a conscious global workspace that combines all of the information quietly processed in the background by the numerous independent, unconscious modules to which it is connected.

Noting that layers II and III of the prefrontal, parieto-temporal, and cingulate cortexes contain pyramidal neurons with long axons that could reciprocally interconnect distinct cortical areas, Changeux and Dehaene identify these circuits as possibly constituting the neuronal substrate of this global workspace. These circuits become activated only during conscious processing and are very strongly inhibited in individuals who are in a vegetative state, or under general anaesthesia, or in a coma. Both of these facts lend support to Changeux and Dehaene’s hypothesis. In contrast, the brain’s unconscious processors are more localized, generally in the sensory cortical areas.

In 2006, Changeux and Dehaene’s research using brain-imaging techniques led them to distinguish three major forms of mental processing in the human brain: subliminal, preconscious, and conscious.

Lien : Conscious, preconscious, and subliminal processing: a testable taxonomy

For conscious processing to occur, there are two conditions that that must be met: a sufficient level of alertness (being awake rather than asleep, for example) and sufficient bottom-up activation, in other words, a response must be occurring in the primary and secondary sensory areas.

But these conditions do not suffice to let a stimulus enter consciousness. For example, some individuals may be awake and display an activation of the extrastriate visual areas of the cortex, yet deny having seen any stimulus whatever. Hence, according to Changeux and Dehaene, for a piece of information to access consciousness, a third condition also must be met: the activation of the associative cortexes by these neurons with long axons that create a reverberation between distant neuronal assemblies.

But why do certain pieces of information become conscious while others do not? To explain this phenomenon, Changeux and Dehaene distinguish four situations.

In the first situation, the information remains unconscious, because it is processed by circuits that are not anatomically connected to the conscious neuronal workspace (for instance, the circuits that regulate the body’s digestive functions). But in the three other cases, the access door to the conscious workspace does exist.

• If the signal is too weak, the processing of the information remains localized in the unconscious processor and dissipates rapidly; this corresponds to the subliminal state, which remains unconscious because the degree of activation stays below the threshold needed to enter the self-amplifying loops of the conscious workspace (see sidebar).
• If the activation is strong enough to spread into several specialized sensorimotor areas, but the individual’s attention is not focused on these stimuli, then the information remains inaccessible to consciousness. It is therefore in a preconscious state, which can, however, become conscious if it undergoes sufficient amplification from the top down.
• Lastly, a stimulus can become conscious in two ways: if it causes us to deliberately turn our attention to a preconscious state, or, if this signal is so strong and unexpected that it forces its way into the conscious workspace. An example of the first case (“top-down” activation) would be when you decide to eavesdrop on a nearby conversation at a cocktail party. An example of the second (“bottom-up” activation) would be what happens when someone calls out your name or yells “Stop, thief!” at that same party.

In these three illustrations, the darkness of the coloured dots is proportional to the intensity of activation, the small arrows represent the interactions among the specialized circuits, and the large arrows represent the direction of attention from the top down toward the stimulus or toward something else. Note that there is a continuum of states between the first illustration and the second, but a sudden transition between the second and the third. After Dehaene et al., 2006.

But in both of these last two cases, the transition from preconscious to conscious is abrupt, as is the case for any non-linear, self-amplified dynamic system (see sidebar). This transition is also always accompanied by an activation in the parieto-frontal and anterior cingulate cortex.

When this activation reaches several richly interconnected associative areas, two things can happen. The activation can undergo a reverberation in the workspace and thus remain available for a much longer time than the initial stimulus lasts. The activation can also rapidly propagate into several specialized systems of the brain that can then make use of it.

In contrast to the classic binary distinction between not conscious and conscious, this model divides the non-conscious state into subliminal and preconscious ones, thus providing a classification into three distinct states (or four, if you count vegetative regulatory processes, which by definition are always unconscious).

This distinction makes sense, in light not only of the results of brain-imaging experiments, but also of phenomena such as inattentional blindness, which show that even when there is substantial preconscious activation, a stimulus can remain unconscious if the individual is not paying attention to it.

Lien : Trois livres du Dr Antonio DamasioLien : Eléments de définition : la conscienceLien : Spinoza avait raisonLien : Review of The Feeling of What Happens By WILLIAM H. CALVIN
Lien : What is possible to call growing up in language, in any language, acquisition?Lien : Defending Damasio
Chercheur : Antonio Damasio - Feelings

“The drama of the human condition comes solely from consciousness. Of course, consciousness and its revelations allow us to create a better life… but the price we pay for that better life is high. It is not just the price of risk and danger and pain. It is the price of knowing risk, danger, and pain. Worse even: it is the price of knowing what pleasure is and knowing when it is missing or unattainable.”

- Antonio R. Damasio, The Feeling of What Happens: Body and Emotion in the Making of Consciousness (1999)

To the various levels of accessibility of the contents of consciousness described by Changeux and Dehaene, another continuum must be added: that of the brain’s ability to form its own representation of the “self”. How does this representation of self contribute to conscious experience? This question has been central to the concerns of researchers such as Edelman, Tononi, Llinás, and, especially, Antonio Damasio.

In his book Descartes’ Error: Emotion, Reason, and the Human Brain, published in 1994, Damasio argues that conscious thought depends substantially on the visceral perception that we have of our bodies. Our conscious decisions arise from abstract reasoning processes, but Damasio shows that these processes are rooted in our bodily perceptions, and that it is this constant monitoring of the communications between the body and the brain that lets us make informed decisions.

This is what Damasio means by his concept of “somatic markers”, which also clarifies the role and the nature of the emotions from an evolutionary standpoint. The somatic manifestations of the emotions are processed in working memory so as to “mark” perceptual information from the external environment with an affective value and thus assess the importance of this information to the organism. This process is essential for any decisionmaking that involves the survival of the organism in question.

In a later book, The Feeling of What Happens: Body and Emotion in the Making of Consciousness (1999), Damasio develops his model further to account for the various possible levels of consciousness of self. The visceral monitoring described above becomes the proto-self, which is a moment-to-moment perception of the body’s internal emotional state and is made possible by the insula, among other structures in the brain.

Subsequently, a perception of the outside world becomes conscious when it is placed in relationship to this proto-self. This higher-order relationship, which Damasio calls core consciousness, answers questions such as “What am I feeling about the scene I am looking at (or the sentence I am reading )?” Many species of animals may be equipped with this feeling of the “here and now”.

A third level, extended consciousness, becomes possible when the individual can form a mental representation of his or her own conscious experiences in the past or the future by means of memory and the higher functions that make abstract conceptualization possible.

Thus, according to Damasio, this autobiographical consciousness—the sense that humans have of being themselves and not someone else—is grounded in all those moments in life when our core consciousness attributes affective value to what we are experiencing. As a result, this autobiographical self is in a constant process of reconstruction that is both informed by the past and influenced by our expectations for the future.

Damasio also distinguishes extended consciousness from what is referred to by the general term “intelligence”. According to Damasio, extended consciousness provides access to the widest possible body of knowledge, whereas intelligence is related more to the ability to manipulate this knowledge in order to devise new behavioural responses.

Damasio also regards this uniquely human extended consciousness as the source of such faculties as creativity, systematic consideration of others, and moral consciousness .

Damasio’s proposed three-level hierarchy of consciousness of self can be found with many variants in the works of other authors from our own time as well as the past.

For example, Damasio’s core consciousness corresponds to William James’s agent-self or to Endel Tulving’s noetic consciousness (though these terms do not overlap completely). The general expression “awareness” is often used to describe this core consciousness or “attention-consciousness”—our state of alertness to our environment.

Human beings would thus share primary consciousness with most other animals that are equipped with sophisticated sensory organs and a complex brain. The term “creature consciousness” is also used to describe this elementary form of consciousness which, for example, enables flies to navigate through the air and presupposes that they know how to distinguish between their own movements and what is happening in the world around them.

Newborn human babies, on the other hand, are still incapable of distinguishing between themselves and the rest of the world, including their mothers. The consciousness of self develops between the ages of six months and one year.

The consciousness of existing as a person in time—what Damasio calls extended consciousness—is often classified into two types.

The first is reflexive consciousness (or introspective consciousness), which mainly stresses that it is I who am perceiving, I who am directing my attention toward such-and-such an object or such-and-such a thought, I who am controlling my reasoning or my behaviour. It is this consciousness, of being aware of something, that appears to be common to humans and the great apes.

This reflexive consciousness would be the necessary condition for consciousness of self—knowing my own personal history, knowing why I am where I am at the present moment or why I will be somewhere else tomorrow night. It is Tulving’s autonoetic consciousness, James’s object-self—in other words, the construction of self in time, which does not begin before age 2 in human beings. It is this consciousness that eventually enables us to tell our life stories, to act our role in life’s drama, and to modify our memories as this drama unfurls.

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Chercheur : Susan Greenfield

This idea that there are various degrees of consciousness and that the emotions constitute a fundamental elementary form of it is defended by many scientists, including neuropharmacologist Susan Greenfield. Greenfield stresses that the activity of the neuronal assemblies distributed in the various parts of the brain is constantly modulated by the neuromodulatory neurons associated with an individual’s emotional state.

There are also some molecules, in particular some peptides, that may influence not only the forming of assemblies of neurons in the brain, but also the body’s hormonal and immune system. The feedback loops between the brain and the body are therefore due not only to the vegetative nervous system, but also to all of these chemical molecules that can act on the brain and the body simultaneously.

From this perspective, consciousness, whose most primary levels appear to be related to the emotions, is not simply a matter of brain activity, but rather an experience involving the body as a whole. This description comes closer to the conception of the human mind advanced by Freeman and Varela, who attribute a central role to the individual’s body situated in its environment. These authors thus take exception to the traditional cognitivist approach, in which the human brain is regarded as a system that applies rules to manipulate internal representations of the world.

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Who’s in Charge—Us?

The Brain’s Default Network

Until the mid-20th century, scientists classified natural phenomena into two categories: phenomena that were random (and therefore unpredictable), and phenomena that followed deterministic rules (and hence were predictable—in other words, if you knew their initial conditions, you could predict their future behaviour).

But then scientists noticed that there were certain systems that could be described by deterministic rules but wherein a slight modification in their initial conditions could suffice to make their behaviour unpredictable. These systems that are sensitive to initial conditions are said to be “chaotic”.

The magnitudes that define these chaotic systems do not vary in an absolutely random and infinite manner over time. Instead, they appear to be contained by an element of order called a “strange attractor”. The presence of strange attractors is one of the main characteristics of “deterministic chaos” (to learn about the mathematical tools used to model deterministic chaos, see the box to the right).

Lien : Fiche de lecture du livre de James Gleick "La Théorie du Chaos"

We will now briefly discuss neurophysiologist Walter J. Freeman’s approach to the problem of consciousness. But to do so, we must first go back down to the cellular (neuronal) level, because Freeman focuses less on the anatomy of brain structures than on the way that neurons communicate with one another and the patterns of activity to which this communication gives rise in the brain as a whole.

Freeman observed that the neuronal connectivity of the human brain engenders chaotic activity that, like weather phenomena, follows the laws of non-linear dynamics (or “deterministic chaos”—see sidebar). He therefore applied the mathematical tools of non-linear dynamics to interpret the electrical states observed in the brain. By analyzing the electroencephalograms (EEGs) of human brains while they were performing many tasks, Freeman showed that the various rhythms of the human brain do it fact follow the “laws” of spatial/temporal chaos.

Behind what seems to be nothing but noise, these chaotic fluctuations actually display regularities and properties consistent with those of human thought. One example is the capacity for rapid, extensive changes. Another is the brain’s ability to almost instantly transform sensory inputs into conscious perceptions.

Vast assemblies of neurons can change their activity pattern abruptly and simultaneously in response to a stimulus that may be very weak. This destabilization of a primary sensory cortex travels to other areas of the brain, where it is “digested” in a way that is specific to each individual, depending on the content of that particular individual’s memory. This is why, according to Freeman, far from being harmful, the chaotic activity of millions of neurons is what makes all perception and all new thoughts possible.

This is also why Freeman thinks that phenomena such as consciousness cannot be understood solely by examining the properties of individual neurons. Just as a hurricane that develops from the collisions of billions of air molecules affects the physical environment, so an overall pattern that emerges from the activity of billions of neurons throughout the cortex affects, for example, the motor areas of the brain so as to produce a given set of body movements. In the latter case, the loop is then closed when the environmental changes caused by these movements in return produce a perception that transforms the brain’s general activity once again.

Freeman therefore does not regard perception and action as two independent phenomena, one input, the other output. Instead, he sees them as the same process enabling the individual to act upon the world. Thus he goes further than the idea of perception as an active phenomenon that is currently accepted today.

The rhythmic synchronization of the neurons occupies a central place in Freeman’s model. Its role, according to Freeman, is to co-ordinate activity among the various areas of the brain so that physically distant sets of neurons are combined into a single functional activity pattern. Every brain, by virtue of its history, generates a unique context (a “chaotic attractor”, in the terminology of chaos physics) in which meanings develop from such activity patterns. Consciousness would then be the highest-level pattern that connects these meanings to one another. It is not in itself the cause of any neuronal effects; it is rather a way of harmoniously and globally interconnecting the fluctuations in the brain so as to facilitate their interaction.

This model offers a way out of the impasse of trying to determine the origin of conscious will through linear causal reasoning: instead it proposes a process of circular causality—an epistemological breakthrough made possible by the mathematics of chaos. The origin of a conscious action therefore should be sought not solely in the brain of the individual who takes that action, but also in that individual’s continuing relationship with other individuals and with the rest of the world. Because according to Freeman, what we call our decisions are constructed in real time by the behaviour of our entire bodies, and we are informed of these decisions on the conscious level only after a slight delay. Thus consciousness would intervene only to smooth out the various aspects of an individual’s behaviours, to modulate them, and probably to legitimize them in relation to the entire set of meanings that constitute that individual’s personality.

In the terminology of dynamics, consciousness would correspond here to an “operator”, because it modulates the brain dynamics from which past actions have arisen. This conception is consistent with a hypothesis proposed by William James in 1878, that consciousness interacts with the brain’s processes and is neither an epiphenomenon nor a first cause.

Chaotic systems (see sidebar) are both random and determined (which is no small contradiction). They may comprise an infinite number of unstable cyclical movements of various frequencies, which makes them very useful for describing the cognitive processes that arise from various neuronal oscillations.

The ideal tool for analyzing such systems is the language of non-linear mathematics, which makes it possible to distinguish between the mere “noise” in disorderly systems and the hidden order in chaotic systems. Researchers are constantly discovering new phenomena that cannot be understood through an analysis of their components alone. Some of these phenomena are physical (such as aerodynamic turbulence), others are chemical (such as oscillating chemical reactions), and still others ecological, meteorological, or even economic. In order to understand such phenomena, it is absolutely essential to analyze their behaviour as a whole, which can be done by means of non-linear mathematics.

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“In the course of evolution, when did the neuronal system appear? Not in plants, not in fungi, not in bacteria. It appeared in animals. To feed themselves, animals found the solution of eating prey. They therefore had to move, and locomotion is the constituent logic of the animal. So that was when the neuronal system appeared, because to hunt, to move, you need a perception-action loop.”

- translated from an interview with Francisco Varela
in La Recherche, No. 308, April 1998.

The dynamic approach just described in terms of Walter J. Freeman’s work actually is part of a broader theoretical approach called “embodied cognition”. Contrary to the computational approach, the dynamic approach deals with neuronal activities rather than with symbols, and with global states of the brain observed by means of functional brain imaging, rather than with calculations and rules.

Embodied cognition theory, of which Francisco Varela was one of the greatest proponents, challenges the separation between human cognition and its embodiment. For Varela, and for the many researchers who have come to embrace this approach, we cannot understand cognition, and hence consciousness, if we abstract it from the organism embedded in a particular environment with a particular configuration.

In these “ecologically situated” conditions, in which “situated cognition” occurs, any perception results in an action, and any action results in a perception, as we have just seen with Freeman. Hence a perception-action loop constitutes the foundational logic of the neuronal system. Cognition, consciousness—in short, the individual’s entire inner world—emerges from that individual’s actions; it is an “enacted” world . Cognition is continuously enhanced by movement, because the human brain has been constructed in this way throughout the history of phylogenesis.

Non-linear mathematics have also contributed greatly to our understanding of the phenomena of self-organization and emergence that are inherent in the embodied approach, through the concept of an “attractor”, borrowed from the theory of dynamic systems.

Current knowledge thus irretrievably distances us from the traditional, causal model of consciousness as a simple matter of input, process, and output, patterned on the operation of computers. Instead, the ideas of circular causality, and the primacy of action, the emotions, and a living body in a given environment provide us with a richer matrix in which to attempt to understand human consciousness.


The image that the nervous system provides of the world may vary hugely from one species to another. For instance, our perception of colours is no doubt very different from a pigeon’s, because we have only three types of cones, whereas pigeons have five. And there are other species that have sensory modalities that we lack, such as a bee’s ability to sense ultraviolet radiation, or a bat’s ability to itself by echolocation.

How then can we argue that the human brain provides us with a consciousness of our environment that corresponds to the one true reality? What about all the other aspects of this environment that we don’t perceive at all? We are forced to admit that the activity of the human brain, like that of other animal brains, instead seems to create a virtual image of what we regard as reality—an evolutionarily useful sampling of the world. To paraphrase British psychologist Max Velmans, the universe has differing views of itself through my eyes, your eyes, the eyes of a pigeon, and the eyes of a bat.

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