Consciousness

Agreed upon definitions of consciousness are notoriously difficult to come by. While no single definition for the term 'consciousness' exists, it is generally regarded to comprise qualities such as self-awareness, sentience, sapience, and the ability to perceive the relationship between oneself and one's environment. In common parlance, consciousness denotes being awake and responsive to one's environment; this contrasts with being asleep or being in a coma.

Many cultures and religious traditions place the seat of consciousness in a soul separate from the body. Conversely, many scientists and philosophers consider consciousness to be intimately linked to the neural functioning of the brain.

An understanding of necessary preconditions for consciousness in the human brain may allow us to address important ethical questions. For instance, to what extent are non-human animals conscious? At what point in fetal development does consciousness begin? Can machines ever achieve conscious states? These issues are of great interest to those concerned with the ethical treatment of other beings, be they animals, fetuses, or in the future, machines.

Philosophy of Consciousness

Philosophers distinguish between phenomenal consciousness and psychological consciousness. Phenomenal consciousness is the state of being conscious whereas psychological consciousness is about the contents of conscious experience. It is sometimes suggested that consciousness resists or even defies definition but there is a long tradition in philosophy of describing what it is like to be conscious. There are many philosophical stances on consciousness, sometimes known as 'isms', including: behaviorism, cognitivism, dualism, functionalism, phenomenalism, physicalism, pseudonomenalism, and mysticism.

Phenomenal consciousness

There is, in the view of very many philosophers, one mental function that accompanies some, or perhaps all, mental events, namely, consciousness. In a philosophical context, the word "consciousness" means something like awareness, or that a mind is directed at something. (That sounds more like a definition of that philosophical term "intentionality" often referred to with the layman's term "aboutness".) So when we perceive, we are conscious of what we perceive; when we introspect, we are conscious of our thoughts; when we remember, we are conscious of something that happened in the past, or of some piece of information that we learned; and so on.

In this philosophical sense of the word "conscious", we are conscious even when we are dreaming; we are conscious of what's happening in the dream. But sleep researchers believe there is a sleep stage that happens, called "deep sleep", in which apparently we are not conscious of anything in any sense. No mental processes that involve consciousness in an ordinary or in a philosophical sense are going on. So dreamless deep sleep is an instance in which one is alive and one's brain is functioning, but there are no mental events occurring in which there is any element of consciousness. This is a typical situation in which some electroneurobiological researchers see a change in time acuity or the ability to distinguish moments, assumed to arise from relativistic interval-dilation effects at work in brain biophysics.

Modern investigations into and discoveries about consciousness are based on psychological statistical studies and case studies of consciousness states and the deficits caused by lesions, stroke, injury, or surgery that disrupt the normal functioning of human senses and cognition. These discoveries suggest that the mind is a complex structure of various localized functions held together by a unitary awareness.

There has been some debate about the following question: Must one be conscious, in the philosophical sense, whenever a mental event occurs? For example, is it possible to have a pain that one does not feel? Some people think not; they think that in order for something to be a pain, one has to feel it and hence be aware of it. Philosophers call this the "incorrigibility" of certain mental states. Similarly, if anything is a thought, then one has to be aware of that of which one is thinking (indeed, that seems nearly a tautology); if there is no consciousness, then one is not thinking. This raises these questions: do mental events necessarily involve consciousness? What about functioning of the brain of which we are unaware?

Suppose we answer "No." Then, of course, what we'd be saying is that there are some mental events that do not include an element of consciousness. These events are going on even though we aren't aware of them. In other words, part of the mind is unconscious. Cognitive scientists believe that many cognitive processes are unconscious in this manner; we are aware of only some of the events that are occurring in our minds.

Some view consciousness as an emergent phenomenon, somehow arising from a hierarchy of unconscious processes. These are fairly recent views, made popular only after Freud.

Descriptions of Consciousness

Although it is the conventional wisdom that no-one can define consciousness philosophers and psychologists have been publishing similar descriptions of consciousness for centuries. Consciousness can be described but no-one has yet explained it.

Rene Descartes (1641) was clear that conscious experience is a collection of things extended in space and also extended in time:

"2. But before considering whether such objects as I conceive exist without me, I must examine their ideas in so far as these are to be found in my consciousness, and discover which of them are distinct and which confused. 3. In the first place, I distinctly imagine that quantity which the philosophers commonly call continuous, or the extension in length, breadth, and depth that is in this quantity, or rather in the object to which it is attributed. Further, I can enumerate in it many diverse parts, and attribute to each of these all sorts of sizes, figures, situations, and local motions; and, in fine, I can assign to each of these motions all degrees of duration." (Meditation V).

He was also clear that these extended things were things in the brain:

"20. I remark, in the next place, that the mind does not immediately receive the impression from all the parts of the body, but only from the brain, or perhaps even from one small part of it, viz., that in which the common sense (senses communis) is said to be, which as often as it is affected in the same way gives rise to the same perception in the mind, although meanwhile the other parts of the body may be diversely disposed, as is proved by innumerable experiments, which it is unnecessary here to enumerate." (Meditation VI)

He describes the brain as the part of the body that contains the images of thoughts and senses but considers that the thing that generates thoughts is a place with no size:

"... And although I may, or rather, as I will shortly say, although I certainly do possess a body with which I am very closely conjoined; nevertheless, because, on the one hand, I have a clear and distinct idea of myself, in as far as I am only a thinking and unextended thing, and as, on the other hand, I possess a distinct idea of body, in as far as it is only an extended and unthinking thing, it is certain that I, [that is, my mind, by which I am what I am], is entirely and truly distinct from my body, and may exist without it." (Meditation VI)

Here Descartes' Dualism is clearly described, he proposes that, as well as images extended in the brain we have a point (unextended thing) that produces the thoughts and views the images in the brain.

The things in the brain have 'qualities' such as colour and seem to be related to the brain as much as to actual objects:

"But with regard to light, colors, sounds, odors, tastes, heat, cold, and the other tactile qualities, they are thought with so much obscurity and confusion, that I cannot determine even whether they are true or false; in other words, whether or not the ideas I have of these qualities are in truth the ideas of real objects. (Meditation III)"

John Locke (1689) describes conscious experience as consisting of images and thoughts in the mind:

"Idea is the object of thinking. Every man being conscious to himself that he thinks; and that which his mind is applied about whilst thinking being the ideas that are there, it is past doubt that men have in their minds several ideas,- such as are those expressed by the words whiteness, hardness, sweetness, thinking, motion, man, elephant, army, drunkenness, and others: it is in the first place then to be inquired, How he comes by them?"

Notice how he uses 'idea' to mean images, thoughts etc. He uses the word 'mind' where Descartes uses 'brain'. Locke is also clear that conscious experience is extended in time:

"Duration is fleeting extension. There is another sort of distance, or length, the idea whereof we get not from the permanent parts of space, but from the fleeting and perpetually perishing parts of succession. This we call duration; the simple modes whereof are any different lengths of it whereof we have distinct ideas, as hours, days, years, &c., time and eternity."

Locke describes the qualities of things (qualia):

"First, our Senses, conversant about particular sensible objects, do convey into the mind several distinct perceptions of things, according to those various ways wherein those objects do affect them. And thus we come by those ideas we have of yellow, white, heat, cold, soft, hard, bitter, sweet, and all those which we call sensible qualities; which when I say the senses convey into the mind, I mean, they from external objects convey into the mind what produces there those perceptions."

David Hume (1739), in common with Decartes and Locke, describes consciousness as qualia extended in space and time:

"The idea of space is convey'd to the mind by two senses, the sight and touch;" ................ "Now such as the parts are, such is the whole. If a point be not consider'd as colour'd or tangible, it can convey to us no idea; and consequently the idea of extension, which is compos'd of the ideas of these points, can never possibly exist. But if the idea of extension really can exist, as we are conscious it does, its parts must also exist; and in order to that, must be consider'd as colour'd or tangible. We have therefore no idea of space or extension, but when we regard it as an object either of our sight or feeling.

The same reasoning will prove, that the indivisible moments of time must be fill'd with some real object or existence, whose succession forms the duration, and makes it be conceivable by the mind."

Immanuel Kant (1781) also describes things laid out in the mind and goes further to suggest that 'form' is a property of the mind:

"That in the appearance which corresponds to sensation I term its matter; but that which so determines the manifold of appearance that it allows of being ordered in certain relations, I term the form of appearance. That in which alone the sensations can be posited and ordered in a certain form, cannot itself be sensation; and therefore, while the matter of all appearance is given to us a posteriori only, its form must lie ready for the sensations a priori in the mind, and so must allow of being considered apart from all sensation. "(p 66)....

"The representation of space cannot, therefore, be empirically obtained from the relations of outer appearance. On the contrary, this outer experience is itself possible at all only through that representation. 2. Space is a necessary a priori representation, which underlies all outer intuitions. "(p 68)

He considers that time is found in the mind:

"Time is not an empirical concept that has been derived from any experience. For neither coexistence nor succession would ever come within our perception, if the representation of time were not presupposed as underlying them a priori. Only on the presupposition of time can we represent to ourselves a number of things as existing at one and the same time (simultaneously) or at different times (successively)."

William James (1890) described our conscious experience of time as "the short duration of which we are immediately and incessantly sensible" and used a term due to ER Clay, the "specious present", to describe it.

Many other pre-twentieth century philosophers have described consciousness and agreed that conscious experience is a manifold (geometric form) of things with qualia arranged in space and time. This geometric form is thought to be present in the physical brain, conveyed there from the senses or created by reflection (thinking). Descartes also notices that there is an observation point (unextended place) from which this form appears to be viewed.

It has long been realised that this description of conscious experience is not easily explained by science. A scientific explanation for how the images in the brain are viewed within the brain is particularly problematic. Any simple theories of the empirical descriptions would seem to involve the need for an absurd homunculus, a little man in the brain who would look at the contents of the brain.

Dennett and Kinsbourne (1992) summarised this problem:

"Wherever there is a conscious mind, there is a point of view. A conscious mind is an observer, who takes in the information that is available at a particular (roughly) continuous sequence of times and places in the universe. A mind is thus a locus of subjectivity, a thing it is like something to be (Farrell, 1950, Nagel, 1974). What it is like to be that thing is partly determined by what is available to be observed or experienced along the trajectory through space-time of that moving point of view, which for most practical purposes is just that: a point. For instance, the startling dissociation of the sound and appearance of distant fireworks is explained by the different transmission speeds of sound and light, arriving at the observer (at that point) at different times, even though they left the source simultaneously.

But if we ask where precisely in the brain that point of view is located, the simple assumptions that work so well on larger scales of space and time break down. It is now quite clear that there is no single point in the brain where all information funnels in, and this fact has some far from obvious consequences."

Some neuroscientists (see Bogen(1995)) would question the generalisation of Dennett and Kinsbourne's assertion that "there is no single point in the brain where all information funnels in", it being possible that there are places in the brain that contain output from all over the cerebral cortex, so there may be single places even though there are no single points.

But how could there be a "single point in the brain where all information funnels in"? A point cannot contain many things. Descartes was faced with this problem and invented a form of Dualism in which the 'point' is non-physical. Some scientists have proposed physical theories to account for the point (Green (2003), Smythies(2003)). Dennett and Kinsbourne explained the viewing point as something we think we have but which may not exist.

References

Bogen, J.E. (1995). On the neurophysiology of Conciousness: I. An overview. Consciousness and Cognition, 4, 52-62. http://www.its.caltech.edu/~jbogen/text/bogen-95.pdf

Dennett, D. and Kinsbourne, M. (1992) Time and the Observer: the Where and When of Consciousness in the Brain. (1992) Behavioral and Brain Sciences, 15, 183-247, 1992. Reprinted in The Philosopher's Annual, Grim, Mar and Williams, eds., vol. XV-1992, 1994, pp. 23-68; Noel Sheehy and Tony Chapman, eds., Cognitive Science, Vol. I, Elgar, 1995, pp.210-274 http://ase.tufts.edu/cogstud/papers/time&obs.htm

Descartes, R. (1641). Meditations on First Philosophy. http://www.orst.edu/instruct/phl302/texts/descartes/meditations/meditations.html

Green, A. (2003) The Science and Philosophy of Consciousness. http://www.users.globalnet.co.uk/~lka/conz.htm

Hume (1739-40). A Treatise of Human Nature: Being An Attempt to Introduce the Experimental Method of Reasoning Into Moral Subjects. http://www.class.uidaho.edu/mickelsen/ToC/hume%20treatise%20ToC.htm

James, W. (1890). The Principles of Psychology (p608), New York: Henry Holt.

Kant, I (1781). Critique of Pure Reason. Trans. Norman Kemp Smith with preface by Howard Caygill. Pub: Palgrave Macmillan. http://www.hkbu.edu.hk/~ppp/cpr/toc.html

Locke, J. (1689). An Essay Concerning Human Understanding http://www.arts.cuhk.edu.hk/Philosophy/Locke/echu/

Smythies J. (2003) Space, Time and Consciousness Journal of Consciousness Studies, 2003, vol. 10, iss. 3, pp. 47-56(10) Imprint Academic

Epiphenomenalism

Philosophers had realised since the days of Descartes that conscious experience seemed to be more about observation than action. Descartes (1641) noted that words and actions could just pop into mind 'unbidden'. The experiments and theories of the behaviourists in the twentieth century have added to this idea that consciousness does not initiate actions, that it is 'epiphenomenal'.

The work of neuroscientists such as Benjamin Libet has also suggested that decisions and actions enter conscious experience after the brain has undergone the changes necessary to embark on these actions.

The epiphenomenal mind is often rejected because something without an apparent function should not exist. Such rejections are premature however because all that epiphenomenalism tells us is that we do not understand the nature or role of consciousness. Epiphenomenalism might also be rejected because it seems to rule out free will but again, when we have little or no understanding of the nature of conscious experience it is premature to reject legitimate observations on the basis of a poorly understood idea like 'free will'.

Libet himself proposed that consciousness may censor actions, preventing unsuitable actions from occurring, rather than initiating actions.

Neuroscience of Consciousness

Several studies point to common mechanisms in different clinical conditions that lead to loss of consciousness. Persistent vegetative state (PVS) is a condition in which a person loses the higher cerebral powers of the brain, but maintains sleep-wake cycles with full or partial autonomic functions. Studies comparing PVS with healthy, awake subjects consistently demonstrate an impaired connectivity between the deeper (brainstem and thalamic) and the upper (cortical) areas of the brain. In addition, it is agreed that the general brain activity in the cortex is lower in the PVS state. Some non-Angloamerican traditions in electroneurobiology (a technical term to search the Web for them) view this loss of consciousness as a loss of the ability to resolve time, along a continuum that starts with inattention, continues on sleep and arrives to coma and death.

Loss of consciousness also occurs in other conditions, such as general (tonic-clonic) epileptic seizures, in general anaesthesia, maybe even in deep (slow wave) sleep. The currently best supported hypotheses about such cases of loss of consciousness focus on the need for 1) a widespread cortical network, including particularly the frontal, parietal and temporal cortices, and 2) cooperation between the deep layers of the brain, especially the thalamus, and the upper layers; the cortex. Such hypotheses go under the common term "globalist theories" of consciousness, due to the claim for a widespread, global network necessary for consciousness to exist in the first place.

Brain chemistry affects human consciousness. Sleeping drugs (such as Midazolam = Dormicum) can bring the brain from the awake condition (conscious) to the sleep (unconscious). Wake-up drugs such as Anexate reverse this process. Many other drugs (such as heroin, cocaine, LSD, MDMA) have a consciousness-changing effect.

Theories of Consciousness

No theory of consciousness is universally accepted but some of the more prominent theories are described below.

Consciousness and language

Because humans express their conscious states using language, it is tempting to equate language abilities and consciousness (see for instance Julian Jaynes theory of the breakdown of the Bicameral Mind). There are, however, speechless humans (infants, Kaspar Hauser, aphasics), to whom consciousness is attributed despite language lost or not yet acquired. Moreover, the study of brain states of non-linguistic primates, in particular the macaques, has been used extensively by scientists and philosophers in their quest for the neural correlates of the contents of consciousness.

Behaviourism and Consciousness

Behaviourism is a school of psychology that, in its most radical form, considers consciousness to be unnecessary to the organism and perhaps no more than a 'reflex to a reflex' (Lev Vygotsky (1925).

Behaviourism gained huge impetus with the work of Pavlov on animals at the turn of the nineteenth century and was seen by many psychologists as an antidote to the Freudian and other introspective approaches to psychology. John B. Watson, who was influenced by Pavlov, performed experiments on conditioning in human beings and, in his 1913 manifesto, 'Psychology as the Behaviourist Views It', he defines his approach to psychology:

"Psychology, as the behaviorist views it, is a purely objective, experimental branch of natural science which needs introspection as little as do the sciences of chemistry and physics. It is granted that the behavior of animals can be investigated without appeal to consciousness. Heretofore the viewpoint has been that such data have value only in so far as they can be interpreted by analogy in terms of consciousness. The position is taken here that the behavior of man and the behavior of animals must be considered on the same plane; as being equally essential to a general understanding of behavior. It can dispense with consciousness in a psychological sense."

So according to Watson phenomenal consciousness may exist but it is immaterial to psychology. In the Soviet Union however behaviourism took a more idealistic turn and supported the ideas of Marxism in which human consciousness is constructed by society. Vygotsky(1925) proposed that:

"The problem of consciousness must be solved in psychology in a sense that consciousness is an interaction, reflection, and mutual excitation of different systems of reflexes. What is conscious is what is transmitted as an irritant to other systems in which it has a response. Consciousness is always an echo, a response apparatus. ... With this, the problem of mind is resolved without any waste of energy. Consciousness is wholly reduced to the transmitting mechanisms of reflexes operating according to general laws, i.e., no processes other than reactions can be admitted into the organism."

In the 1950's B. F. Skinner developed a form of behaviourism which was very similar to that of Vygotsky but still admitted the possibility of phenomenal consciousness. He considered that mental states were redundant to the analysis of behaviour. In other words, if phenomenal consciousness does exist it is epiphenomenal (has no role in the control of behaviour).

In 1949 Gilbert Ryle discussed a form of behaviourism known as 'Analytical Behaviourism' in which consciousness is also considered to be unnecessary for the function of human beings, phenomenal consciousness being no more than 'the dogma of the ghost in the machine' of the brain. Ryle, like Skinner, also proposed that explaining behaviour in terms of some inner being was circular and equivalent to suggesting that the brain contained a homunculus.

Of the behaviourists, Vygotsky dismissed phenomenal consciousness and has much in common with modern Strong AI Theorists.

References

Ryle, G. (1949) The Concept of Mind. Chicago: The University of Chicago Press, 1949.

Vygotsky, LS. (1925) “Consciousness as a problem in the psychology of behavior” Secondary source: Undiscovered Vygotsky: Etudes on the pre-history of cultural-historical psychology (European Studies in the History of Science and Ideas. Vol. 8), pp. 251-281; http://www.marxists.org/subject/psychology/works/veresov/consciousness.htm

Watson, J.B. (1913) Psychology as the Behaviorist Views it. First published in Psychological Review, 20, 158-177 http://psychclassics.yorku.ca/Watson/views.htm

Quantum mechanical theories of consciousness

The physicist Roger Penrose, in his book The Emperor's New Mind, argued for a quantum mind approach, suggesting that non-local quantum mechanical effects within sub-neural structures give rise to conscious states. He has argued for the need for a fundamentally new physics in order to explain consciousness, which he conceives as a fungible material: one of which any portion can substitute another (ie: consciousness being a property of the brain rather than a property some special place in the brain).

This central feature is of much importance: Quantum mechanical theories of consciousness investigate such an entity, namely an experience having the property of being fungible, and their work has not hitherto faced the problems set by experience as it is found, namely as distinctively exclusive and "unbarterable". This for other researchers makes a main controversial point.

Penrose was not the first to suggest a link between this fungible consciousness and QM; Michael Lockwood and Henry Stapp did so earlier, as did Brian Flanagan. Before them there was Niels Bohr, the father of quantum mechanics (QM), who, as David Bohm tells us, "suggests that thought involves such small amounts of energy that quantum-theoretical limitations play an essential role in determining its character." Also of interest are the ideas of Hermann Weyl, Eugene Wigner, and Erwin Schrödinger. All of them shared in the view of consciousness as a fungible reality; adversaries of this stance call it "antipersonalism" and argue that such a construct has never been factually found.

No real evidence has been found to support any relationship between quantum mechanics and the phenomenon of consciousness but it is interesting to explore the roots of these theories.

Theoretical physicists have been interested in the possible connection between conscious observation and quantum mechanics since the beginning of quantum theory. This interest stemmed from the discovery that quantum phenomena such as the way an electron moves seemed to have different physical descriptions depending upon whether of not the electron could, in principle, be observed. If the electron is unobserved its position varies in a wave-like fashion; when its position is observed it moves like a particle. According to early quantum physics the variation of position in a wave like fashion should apply to whole objects like cars or planets. It seemed as if there was some feature of being a conscious observer that prevented this wave or prevented the wave from being observed. This problem is also known as the 'measurement problem'.

Recently, however, work on quantum decoherence has demonstrated that no special, consciousness-related processes are necessary to prevent such peculiar properties of everyday objects from being observed. Measurements that would reveal, say, large-scale quantum uncertainty in the position of a car or a planet rapidly become prohibitively difficult for any measuring apparatus that physically interacts with the observed system. Even if there is no explicit wavefunction collapse, the observations available in practice to any observer in the world are limited to a 'quantum environment' resembling the world that we see. One popular interpretation of the 'environment' is that it is a zone of interrelated events in a 'multiverse' that contains all possible events.

Unfortunately the quantum 'environment' is not entirely classical, it still has the capacity for branching into multiple environments because some quantum events within the environment can lead to it splitting into distinct branches that do not interact with each other. The problem of the observer in quantum physics has been reduced a problem of why a particular observer observes a particular branch. This is discussed by Zeh (2000), one of the founders of decoherence theory, in the reference below.

Quantum physics could be involved in consciousness in two ways. In the first, quantum uncertainty could occur in the brain and this could be used to affect the outcome of information processing; in the second, consciousness itself could be prior to all other things and be involved in some unknown way in the branching process.

Recently Max Tegmark calculated the rate at which quantum uncertainty disappeared in the brain as a result of decoherence and predicted that this would occur very rapidly, perhaps a thousand million times faster than processes such as the generation of nerve impulses. This suggests that information processing in the brain due to nerve impulses is a non-quantum effect. This does not resolve the problem of the conscious observer in physics although it does mean that behaviourists and neurophysiologists who deal with information processing in the brain can disregard quantum effects when dealing with nerve impulses. However, it does not deal with possible exotic effects such as electromagnetic fields in the brain and these may still be responsible for QM effects on information processing.

The problem of whether consciousness precedes all other physical phenomena is still very much a subject for discussion and speculation but it should be stressed this is entirely speculative and not supported by experimental data or widely believed.

References

Tegmark, M (2000) The importance of quantum decoherence in brain processes. quant-ph/9907009, Phys. Rev. E 61, 4194-4206

Tegmark, M & Wheeler, J,A. (2001). A Hundred Years of Quantum Mysteries. quant-ph/0101063, Scientific American Feb. 2001, 68-75

Zeh, H.D, (2000). The Problem of Conscious Observation in Quantum Mechanical Description. quant-ph/9908084. Found.Phys.Lett. 13 (2000) 221-233

Buddhism

The buddhism analyzes the personal experience by the theory of the five aggregates or shandhas. It says that any personal experience occurs through these five aggregates: form, feeling, perception, volition and consciousness.

Tests of Self Awareness and Consciousness

As there is still not a clear definition of consciousness, no empirical tests currently exist to test consciousness as a whole. Some have even argued that empirical tests of consciousness are intrinsically impossible. However, some researchers have devised tests to detect what they feel are certain aspects of consciousness such as self awareness.

Mirror test

With the mirror test [1], devised by Gordon Gallup in the 1970s, one is interested in whether or not animals are able to recognize themselves in a mirror. Such self-recognition is said to be an indicator of consciousness. Humans (older than 18 months), great apes (except for gorillas), and bottlenose dolphins have all been observed to pass this test.

See also

• Attention, Cognitive science, Society of Mind, Neural Darwinism, Unconscious mind
• Altered state of consciousness, Simulated consciousness
• Consciousness-only
• Daniel Dennett, Gerald Edelman, Marvin Minsky, John Searle
• New Mysterianism
• Qualia
• Quantum mind
• Stream of consciousness

Further reading

• Blackmore, S. (2004). Consciousness: an introduction. Oxford: Oxford University Press.
• Koch, C. (2004). The quest for consciousness. Englewood, CO: Roberts & Company.
• Cleermans, A. (Ed.) (2003). The unity of consciousness. Oxford: Oxford Univerisity Press
• Metzinger, T. (2003). Being no one: the self-model theory of subjectivity. Cambridge, MA: MIT Press.
• Metzinger, T. (Ed.) (2000). The neural correlates of consciousness. Cambridge, MA: MIT Press.
• Damasio, A. (1999). The feeling of what happens. New York: Harcourt Press.
• Dennett, D. (1991). Consciousness explained, Boston: Little & Company.
• Penrose, R. (1989). The emperor's new mind. Oxford: Oxford University Press.

External links

Journals & newsletters

• The journal Consciousness and Cognition
• The Journal of Consciousness Studies
• English papers in the Argentinian free State journal Electroneurobiología
• The free electronic journal Psyche
• the free e-zine Science & Consciousness Review

Societies

• Association for the Scientific Study of Consciousness

Philosophy resources

• David Chalmers' collection of online papers on consciousness

Misc Sites

• The Science and Philosophy of Consciousness
• Conscious Entities
• Endogenous Light Theory of Consciousness
• The Evolution of the Higher Consciousness