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	Philosophers have provided a description of consciousness that is like our own experience. When we look around a room or have a dream, things are laid out in space and time and viewed as if from a point. However, when philosophers and scientists consider the location of the contents of consciousness there are fierce disagreements. Some philosophers and scientists do not hold that every mental event has a direct physical event (weak or no ']'). As an example, Descartes proposed that the contents of consciousness are images in the brain and the viewing point is some special, non-physical place without extension (the Res Cogitans). This idea is known as 'Cartesian ]'. Another example is found in the work of ] who thought the contents of consciousness are the world itself which becomes conscious experience in some way through a chain of cause and effect. The precise physical substrate of conscious experience in the world, such as photons, photochemicals, quantum fields etc. is not specified. This idea of a chain of cause and effect or chain of relations causing conscious experience to supervene on the world is found in ] and some forms of ].		Philosophers have provided a description of consciousness that is like our own experience. When we look around a room or have a dream, things are laid out in space and time and viewed as if from a point. However, when philosophers and scientists consider the location of the contents of consciousness there are fierce disagreements. Some philosophers and scientists do not hold that every mental event has a direct physical event (weak or no ']'). As an example, Descartes proposed that the contents of consciousness are images in the brain and the viewing point is some special, non-physical place without extension (the Res Cogitans). This idea is known as 'Cartesian ]'. Another example is found in the work of ] who thought the contents of consciousness are the world itself which becomes conscious experience in some way through a chain of cause and effect. The precise physical substrate of conscious experience in the world, such as photons, photochemicals, quantum fields etc. is not specified. This idea of a chain of cause and effect or chain of relations causing conscious experience to supervene on the world is found in ] and some forms of ].

	It is sometimes held that consciousness will emerge from the complexity of brain processing (see for instance the ] of consciousness). The general label ']' allows a new physical phenomenon to be implied by ] theorists without specifying the exact nature of the phenomenon. This leaves an ]. ] see the explanatory gap in terms of phenomenal consciousness and have proposed various physical theories such as ], ] and ], which contain a direct correspondence between brain activity and experience. As yet there is little evidence from brain studies to support these theories~~. For the recent conceptualization see ]~~. ] see the explanatory gap in terms of access consciousness and expect an explanation to emerge from an understanding of the complexity of neural processing.		It is sometimes held that consciousness will emerge from the complexity of brain processing (see for instance the ] of consciousness). The general label ']' allows a new physical phenomenon to be implied by ] theorists without specifying the exact nature of the phenomenon. This leaves an ]. ] see the explanatory gap in terms of phenomenal consciousness and have proposed various physical theories such as ], ] and ], which contain a direct correspondence between brain activity and experience. As yet there is little evidence from brain studies to support these theories. ] see the explanatory gap in terms of access consciousness and expect an explanation to emerge from an understanding of the complexity of neural processing.

	==Physical approaches==		==Physical approaches==

Revision as of 08:55, 3 October 2005

Consciousness is a quality of the mind generally regarded to comprise qualities such as subjectivity, self-awareness, sentience, sapience, and the ability to perceive the relationship between oneself and one's environment. Philosophers divide consciousness into phenomenal consciousness which is experience itself and access consciousness which is the processing of the things in experience (Block 2004).

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 dictating the way in which the world is experienced. This aspect of consciousness the subject of much debate and research in philosophy of mind, psychology, brain biology, neurology, and cognitive science.

Humans (and often others as well) are variously said to possess consciousness, self-awareness, and a mind, that contains our sensations, perceptions, dreams, lucid dreams, inner speech and imagination etc.. Each of us has a subjective view. There are many debates about the extent to which the mind constructs or experiences the outer world, the passage of time, and free will.

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.

In common parlance, consciousness denotes being awake and responsive to one's environment; this contrasts with being asleep or being in a coma. The term 'level of consciousness' denotes how consciousness seems to vary during anesthesia and during various states of mind such as day dreaming, lucid dreaming, imagining etc. Nonconsciousness exists when consciousness is not present. There is speculation, especially amongst religious groups, that consciousness may exist after death or before birth.

Etymology

"Consciousness" derives from Latin "conscientia", which primarily means moral conscience. Literallly, "conscientia" means knowledge-with, that is, shared knowledge. The word first appears in Latin juridic texts by writers such as Cicero. Here, conscientia is the knowledge that a witness has of the deed of someone else. In christian theology, conscience stands for the moral conscience in which our actions and intentions are registered and which is only fully known to god. Medieval writers such as Thomas Aquinas describe the conscientia as the act by which we apply practical and moral knowleedge to our own actions (Aquinas, De Veritate 17,1 c.a.). René Descartes was the first to use "conscientia" in a way that does not seem to fit this traditional meaning, and consequently, the translators of his writings in other languages like french and english coined new words in order to denote merely psychological consciousness. These are, for instance, "conscience psychologique", "consciousness", and "Bewusstsein". See Catherine G. Davies, Conscience as Consciousness, Oxford 1990, and Hennig, Cartesian Conscientia.

Consciousness and language

Because humans express their conscious states using language, it is tempting to equate language abilities and consciousness. There are, however, speechless humans (infants, feral children, 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.

Cognitive neuroscience approaches

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 derived from various localized functions that are bound together with a unitary awareness.

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 an individual 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 electroneurobiological interpretations of consciousness characterize this loss of consciousness as a loss of the ability to resolve time (similar to playing an old phonographic record at very slow or very rapid speed), 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 (or loss of time resolution) 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 interact with non-mental reality 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.

There is a neural link between the left and right hemispheres of the brain, known as the corpus callosum. This link is sometimes surgically severed to control severe seizures in epilepsy patients. This procedure was first performed by Roger Sperry in the 1960s. Tests of these patients have shown that after the link is completely severed, the hemispheres are no longer able to communicate, leading to certain problems which usually arise only in test conditions. For example, while the left side of the brain can verbally descibe what is going on in the right visual field, the right hemisphere is esentially mute, instead relying on its spatial abilities to interact with the world on the left visual field. Some say it is as if two separate minds now share the same skull, but both still represent themselves as a single "I" to the outside world.

The bilateral removal of the Centromedian nucleus (part of the Intra-laminar nucleus of the Thalamus) appears to abolish consciousness, causing coma, PVS, severe mutism and other features that mimic brain death. The centromedian nucleus is also one of the principal sites of action of general anaesthetics and anti-psychotic drugs.

Philosophical approaches

Philosophers distinguish between phenomenal consciousness and access or psychological consciousness. Some suggest that consciousness resists or even defies definition. There are many philosophical stances on consciousness, including: behaviorism, dualism, idealism, functionalism, phenomenalism, physicalism, emergentism, and mysticism.

Phenomenal and access consciousness

Philosophers call our current experience phenomenal consciousness. Phenomenal consciousness is simply experience, it is moving, coloured forms, sounds, sensations, emotions and feelings with our bodies and responses at the centre. The hard problem of consciousness was formulated by Chalmers in 1996, it is the problem of "how to explain a state of phenomenal consciousness in terms of its neurological basis" (Block 2004).

Access consciousness is the phenomenon whereby information in our minds is accessible for verbal report, reasoning, and the control of behavior. So when we perceive, information about what we perceive is often access conscious; when we introspect, information about our thoughts is access conscious; when we remember, information about the past (e.g. something that we learned) is often access conscious; and so on. Access consciousness is often thought to be less mysterious than phenomenal consciousness, so that it is held to pose one of the easy problems of consciousness.

Events that occur in the mind or brain that are not within phenomenal or access consciousness are known as unconscious events.

The description and location of consciousness

Although it is the conventional wisdom that consciousness cannot be defined, philosophers have been describing it for centuries. Rene Descartes wrote Meditations on First Philosophy in the seventeenth century, and this contains extensive descriptions of what it is to be conscious. Descartes defined thoughts (Latin: cogitationes) as events in us that are immediate objects of our consciousness. These events are what philosophers now call mental events or states of consciousness. Other philosophers such as Nicholas Malebranche, John Locke, David Hume and Immanuel Kant also agreed with much of this description although some avoid mentioning the viewing point. The extension of things in time was considered in more detail by Kant and James. Kant wrote that "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 stressed the extension of experience in time and said that time is "the short duration of which we are immediately and incessantly sensible". These philosophers also go on to describe dreams, thoughts, emotions etc.

Philosophers have provided a description of consciousness that is like our own experience. When we look around a room or have a dream, things are laid out in space and time and viewed as if from a point. However, when philosophers and scientists consider the location of the contents of consciousness there are fierce disagreements. Some philosophers and scientists do not hold that every mental event has a direct physical event (weak or no 'Supervenience'). As an example, Descartes proposed that the contents of consciousness are images in the brain and the viewing point is some special, non-physical place without extension (the Res Cogitans). This idea is known as 'Cartesian Dualism'. Another example is found in the work of Thomas Reid who thought the contents of consciousness are the world itself which becomes conscious experience in some way through a chain of cause and effect. The precise physical substrate of conscious experience in the world, such as photons, photochemicals, quantum fields etc. is not specified. This idea of a chain of cause and effect or chain of relations causing conscious experience to supervene on the world is found in post-modernism and some forms of behaviourism.

It is sometimes held that consciousness will emerge from the complexity of brain processing (see for instance the Multiple Drafts Model of consciousness). The general label 'emergence' allows a new physical phenomenon to be implied by physicalist theorists without specifying the exact nature of the phenomenon. This leaves an explanatory gap. Indirect Realists see the explanatory gap in terms of phenomenal consciousness and have proposed various physical theories such as Quantum mind, space-time theories of consciousness and Electromagnetic theories of consciousness, which contain a direct correspondence between brain activity and experience. As yet there is little evidence from brain studies to support these theories. Direct Realists see the explanatory gap in terms of access consciousness and expect an explanation to emerge from an understanding of the complexity of neural processing.

Physical approaches

Even at the dawn of Newtonian science Leibniz and many others were suggesting physical theories of consciousness. Modern physical theories of consciousness can be divided into three types: theories to explain behaviour and access consciousness, theories to explain phenomenal consciousness and theories to explain the quantum mechanical (QM) measurement problem. Theories that seek to explain behaviour are an everyday part of neuroscience, some of these theories of access consciousness, such as Edelman's theory contentiously identify phenomenal consciousness with reflex events in the brain. Theories that seek to explain phenomenal consciousness directly, such as Space-time theories of consciousness and Electromagnetic theories of consciousness, have been available for almost a century but have not as yet been confirmed by experiment. Theories that attempt to explain the QM measurement problem include Pribram and Bohm's Holonomic brain theory, Hameroff and Penrose's Orch-OR theory, Spin-Mediated Consciousness Theory and the Many-minds interpretation. Some of these QM theories offer descriptions of phenomenal consciousness as well as QM interpretations of access consciousness. None of the quantum mechanical theories has been confirmed by experiment.

There is also a concerted effort in the field of Artificial Intelligence to create digital computer programs that can simulate consciousness.

Spiritual approaches

Spiritual approaches to consciousness involve the idea of altered states of consciousness or religious experience. Changes in the state of consciousness or a religious experience can occur spontaneously or as a result of religious observance. It is also maintained by some religions and religious factions that the universe itself is consciousness.

In shamanic practice the change in state of consciousness is induced by mind altering drugs or as a result of activities that induce trance. The experience that occurs is interpreted as entering a real, but parallel, world. In many polytheistic religions a change in emotional state is often attributed to the action of a god, for instance love was ruled by Aphrodite and Eros in Ancient Greek polytheism. In Hinduism the change in state is induced by the practice of yoga. Yoga means "joining" and is intended to produce a state of oneness between the practitioner and Krishna. There are numerous types of yoga, for instance Karma yoga involves selfless service and Bhakti Yoga involves worship and love of god and others. Yoga, such as Surat shabd yoga also plays a role in Sikhism and Sant Mat. Forms of yoga such as Hatha Yoga, that involve exercise are popular in the West to keep the adherent sufficiently fit and of an appropriate appearance to live in a materialist society. In Islam and Christianity the change of state can occur as a result of prayer or as a religious experience.

The change in state of consciousness in Hinduism, Buddhism, Christianity and Islam is reported to be quite similar. The pursuit of yoga and the Buddhist Jhanas involve feelings of oneness with the world that give rise to a state of rapture. This is also reported by those undergoing some forms of Christian (or Islamic) religious experience, for instance James (1902) provides the following report:

"I cannot express it in any other way than to say that I did 'lie down in the stream of life and let it flow over me.' I gave up all fear of any impending disease; I was perfectly willing and obedient. There was no intellectual effort, or train of thought. My dominant idea was: 'Behold the handmaid of the Lord: be it unto me even as thou wilt,' and a perfect confidence that all would be well, that all was well. The creative life was flowing into me every instant, and I felt myself allied with the Infinite, in harmony, and full of the peace that passeth understanding. There was no place in my mind for a jarring body. I had no consciousness of time or space or persons; but only of love and happiness and faith."

Meditation is used in some forms of yoga such as Raja Yoga, Hatha Yoga, Transcendental meditation, the Buddhist Jhanas, the Buddhist Immaterial Jhanas (there are several versions of the jhanas in different types of Buddhism), in the practices of Christian monks and Islamic scholars such as Sufi's. Meditation can have a calming influence on practitioners as well as changing the state of consciousness. Therevada Buddhism views the Jhanas and some yogic practices view the early stages of meditation as a preliminary "serenity meditation" in which it is demonstrated that states such as rapture are delusions, products of mind rather than the soul. In most types of Buddhism serenity meditation is followed by a philosophical "insight meditation" that focusses on the idea that the universe is consciousness only.

Functions of consciousness

We generally agree that our fellow human beings are conscious and that lower life forms such as bacteria are not. Many of us attribute consciousness to higher-order animals such as dolphins and primates; academic research is investigating which rather than whether animals are conscious. This suggests the hypothesis that consciousness has co-evolved with life, which would require it to have some sort of added value. People have therefore looked for specific functions of consciousness. Bernard Baars (1997) for instance states that “consciousness is a supremely functional adaptation” and suggests a variety of functions in which consciousness plays a role: prioritization of alternatives, problem solving, decision making, brain processes recruiting, action control, error detection, planning, learning, adaptation, context creation, and access to information. Antonio Damasio (1999) regards consciousness as part of an organism’s survival kit, allowing planned rather than instinctual responses. He also points out that awareness of self allows a concern for one’s own survival, which increases the drive to survive. Although how far consciousness is involved in behaviour is an actively debated issue. Many psychologists, such as radical behaviourists, and many philosophers, such as those who support Ryle's approach, would maintain that behaviour can be explained by non-conscious processes akin to artificial intelligence and might consider consciousness to be epiphenomenal or only weakly related to function.

Tests of 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. A test similar to this was used in the novel "Do Androids Dream of Electric Sheep" by Philip K. Dick to see if a person was a robot or an actual human. In the Ridley Scott movie Blade Runner which was inspired by that book, the test is known as the "Voigt-Kampf" test and tests the subject for empathy.

Turing Test

Alan Turing proposed what is now known as the Turing test to determine if a computer could simulate human conversation undetectably. This test is commonly cited in discussion of artificial intelligence. The application to consciousness is highly suggestive, but not clear. One is reminded of Edsger Dijkstra's comment "The question of whether a computer can think is no more interesting than the question of whether a submarine can swim". A thought experiment which indicates a problem with the Turing Test is as follows. Imagine a computer in which are stored a very large number of questions and a very large number of actual human responses to these questions. If the number of questions and answers was large enough, then the computer would be able to mimic consciousness by a purely mechanical procedure. The simple version of this test says that, if a being behaves as a human we assume he has consciousness even if he was constructed as a zombie, i.e. missing qualia. This sounds like typical behaviourist reasoning. However, that sort of thinking was suspect even before 'The Emperor's New Mind' was published. This leads one to propose the extended Turing test (first proposed by Hugh Deasy in 2004): the robot or zombie must answer questions of how red appears to him/her or what he/she feels at that sunset or upon hearing that Shakira song or smelling Chanel nr. 5. If he/she gives convincing answers we can say that he/she is either a great liar or is conscious. But unless one especially programs the robot/zombie to lie about these issues, then if they really lack qualia then they fail the test.

Mirror test

With the mirror test, 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.

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