Consciousness

# Overview
Consciousness is a characteristic 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. It is a subject of much research in philosophy of mind, psychology, neuroscience, and cognitive science.
Some philosophers divide consciousness into phenomenal consciousness, which is subjective experience itself, and access consciousness, which refers to the universal availability of information to processing systems in the brain. Phenomenal consciousness is a state with qualia. Phenomenal consciousness is being something and access consciousness is being conscious of something.
An understanding of necessary preconditions for consciousness in the human brain may allow us to address important ethical questions. For instance, how is the presence of consciousness to be assessed in severely ill or disabled individuals?  To what extent are non-human animals conscious? At what point in fetal development does consciousness begin? Can machines achieve conscious states? Are today's autonomous and intelligent machines already conscious? 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.

# Etymology
"Consciousness" derives from Latin conscientia which primarily means moral conscience. In the literal sense, "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 knowledge to our own actions.
Rene Descartes has been said to be the first philosopher to use "conscientia" in a way that does not seem to fit this traditional meaning, and, as a consequence, 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, and Bewusstsein.
However, it has also been argued that John Locke was in fact the first one to use the modern meaning of consciousness in his Essay Concerning Human Understanding, although it remains closely intertwined with moral conscience (I may be held morally responsible only for the act of which I am conscious of having achieved; and my personal identity - my self - goes as far as my consciousness extends itself). The modern sense of "consciousness" was therefore first found not in Descartes' work - who sometimes used the word in a modern sense, but did not distinguish it as much as Locke would do -, but in Locke's text. The contemporary sense of the word (consciousness associated to the idea of personal identity, which is assured by the repeated consciousness of oneself) was therefore introduced by Locke; but the word "conscience" itself was coined by Pierre Costes, French translator of Locke. Henceforth, the modern sense first appeared in Locke's works, but the word itself first appeared in the French language.
Locke's influence upon the concept can be found in Samuel Johnson's celebrated Dictionary, in which Johnson abstains from offering a definition of "consciousness," choosing instead to simply quote Locke.

# Philosophical approaches
There are many philosophical stances on consciousness, including: behaviorism, dualism, idealism, functionalism, reflexive monism, phenomenalism, phenomenology and intentionality, physicalism, emergentism, mysticism, personal identity etc.

## Phenomenal and access consciousness
Phenomenal consciousness (P-consciousness) is simply experience; it is moving, coloured forms, sounds, sensations, emotions and feelings with our bodies and responses at the center. These experiences, considered independently of any impact on behavior, are called qualia. The hard problem of consciousness was formulated by Chalmers in 1996, dealing with the issue of "how to explain a state of phenomenal consciousness in terms of its neurological basis" (Block 2004).
Access consciousness (A-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. Chalmers thinks that access consciousness is less mysterious than phenomenal consciousness, so that it is held to pose one of the easy problems of consciousness. Dennett denies that there is a "hard problem", asserting that the totality of consciousness can be understood in terms of impact on behavior, as studied through heterophenomenology. There have been numerous approaches to the processes that act on conscious experience from instant to instant. Philosophers who have explored this problem include Gerald Edelman,  Edmund Husserl and Daniel Dennett. Daniel Dennett (1988) suggests that what people think of as phenomenal consciousness, such as qualia, are judgements and consequent behaviour. He extends this analysis (Dennett, 1996) by arguing that phenomenal consciousness can be explained in terms of access consciousness, denying the existence of qualia, hence denying the existence of a "hard problem."
Events that occur in the mind or brain that are not within phenomenal or access consciousness are known as subconscious events.

## The description and location of phenomenal consciousness
Philosophers have been describing phenomenal consciousness for centuries. Rene Descartes wrote Meditations on First Philosophy in the seventeenth century, containing extensive descriptions of what it is to be conscious. Descartes described conscious experience as ideas such as imaginings and perceptions laid out in space and time that are viewed from a point. Like Aristotle he defines ideas as extended things: "Now among these figures, it is not those imprinted on the external sense organs, or on the internal surface of the brain, which should be taken to be ideas - but only those which are traced in the spirits on the surface of gland H (where the seat of the imagination and the 'common sense' is located). That is to say, it is only the latter figures which should be taken to be the forms or images which the rational soul united to this machine will consider directly when it imagines some object or perceives it by the senses"(Treatise on Man). "Gland H" is the pineal gland and animal "spirits" are an early analogy for electrical activity. This interchangeability of the term "ideas" with mental images can cause confusion for modern readers. According to Descartes each thing appears as a result of some quality (qualia) such as colour, smell, etc.
Other philosophers, such as Nicolas Malebranche, Thomas Reid, John Locke, David Hume and Immanuel Kant, also agreed with much of Descartes' description, although  David Hume and Immanuel Kant avoid mentioning a place from which experience is viewed (see further reading below) and most philosophers have not placed "ideas" on the pineal gland. 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.
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 form and contents of this phenomenal consciousness, there are fierce disagreements. As an example, Descartes proposed that the contents are brain activity seen by a non-physical place without extension (the Res Cogitans), which, in Meditations on First Philosophy, he identified as the soul. 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. This concept is a type of Direct realism. The precise physical substrate of conscious experience in the world, such as photons, quantum fields, etc. is usually not specified.
Other philosophers, such as George Berkeley, have proposed that the contents of consciousness are an aspect of minds and do not necessarily involve matter at all. This is a type of Idealism. Yet others, such as Leibniz, have considered that each point in the universe is endowed with conscious content. This is a form of Panpsychism. Panpsychism is the belief that all matter, including rocks for example, is sentient or conscious. The concept of the things in conscious experience being impressions in the brain is a type of representationalism, and representationalism is a form of indirect realism.
It is sometimes held that consciousness emerges from the complexity of brain processing. The general label 'emergence' applies to new phenomena that emerge from a physical basis without the connection between the two explicitly specified.
Some theorists hold that phenomenal consciousness poses an explanatory gap. Colin McGinn takes the New Mysterianism position that it can't be solved, and Chalmers criticizes purely physical accounts of mental experiences based on the idea that philosophical zombies are logically possible and supports property dualism. But others have proposed speculative scientific theories to explain the explanatory gap, such as Quantum mind, space-time theories of consciousness, reflexive monism, and Electromagnetic theories of consciousness to explain the correspondence between brain activity and experience.
Parapsychologists sometimes appeal to the unproven concepts of psychokinesis or telepathy to support the dualistic belief that consciousness is not confined to the brain.

## Philosophical criticisms of the concept of consciousness
From the eighteenth to twentieth centuries many philosophers concentrated on relations, processes and thought as the most important aspects of consciousness. These aspects would later become known as "access consciousness" and this focus on relations allowed philosophers such as Marx, Nietzsche and Foucault to claim that individual consciousness was dependent on such factors as social relations, political relations and ideology.
Locke's "forensic" notion of personal identity founded on an individual conscious subject would be criticized in the 19th century by Marx, Nietzsche and Freud following different angles. Martin Heidegger's concept of the Dasein ("Being-there") would also be an attempt to think beyond the conscious subject.
Marx considered that social relations ontologically preceded individual consciousness, and criticized the conception of a conscious subject as an ideological conception on which liberal political thought was founded. Marx in particular criticized the 1789 Declaration of the Rights of Man and of the Citizen, considering that the so-called individual natural rights were ideological fictions camouflaging social inequality in the attribution of those rights. Later, Louis Althusser would criticize the "bourgeois ideology of the subject" through the concept of interpellation ("Hey, you!").
Nietzsche, for his part, once wrote that "they give you free will only to later blame yourself", thus reversing the classical liberal conception of free will in a critical account of the genealogy of consciousness as the effect of guilt and ressentiment, which he described in On the Genealogy of Morals. Hence, Nietzsche was the first one to make the claim that the modern notion of consciousness was indebted to the modern system of penalty, which judged a man according to his "responsibility", that is by the consciousness through which acts can be attributed to an individual subject: "I did this! this is me!". Consciousness is thus related by Nietzsche to the classic philosopheme of recognition which, according to him, defines knowledge.
According to Pierre Klossowski (1969), Nietzsche considered consciousness to be a hypostatization of the body, composed of multiple forces (the "Will to Power"). According to him, the subject was only a "grammatical fiction": we believed in the existence of an individual subject, and therefore of a specific author of each act, insofar as we speak. Therefore, the conscious subject is dependent on the existence of language, a claim which would be generalized by critical discourse analysis (see for example Judith Butler).
Michel Foucault's analysis of the creation of the individual subject through disciplines, in Discipline and Punish (1975), would extend Nietzsche's genealogy of consciousness and personal identity - i.e. individualism - to the change in the juridico-penal system: the emergence of penology and the disciplinization of the individual subject through the creation of a penal system which judged not the acts as it alleged to, but the personal identity of the wrong-doer. In other words, Foucault maintained that, by judging not the acts (the crime), but the person behind those acts (the criminal), the modern penal system was not only following the philosophical definition of consciousness, once again demonstrating the imbrications between ideas and social institutions ("material ideology" as Althusser would call it); it was by itself creating the individual person, categorizing and dividing the masses into a category of poor but honest and law-abiding citizens and another category of "professional criminals" or recidivists.

## 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, severe forms of autism), 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.
Julian Jaynes argued to the contrary, in The Origin of Consciousness in the Breakdown of the Bicameral Mind, that for consciousness to arise in a person, language needs to have reached a fairly high level of complexity. According to Jaynes, human consciousness emerged as recently as 1300 BCE or thereabouts. Many philosophers, including W.V. Quine and neuroscientists, including Christof Koch, contest this hypothesis, as it suggests that prior to this "discovery" of consciousness, experience simply did not exist.  Ned Block argued that Jaynes had confused consciousness with the concept of consciousness, the latter being what was discovered between the Iliad and the Odyssey.  Daniel Dennett argues that consciousness is like money in that having the thing requires having the concept of it, so it is a revolutionary proposal and not a ridiculous error to suppose that consciousness only emerges when its concept does.

# 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.  It is likely that different components of consciousness can be teased apart with anesthetics, sedatives and hypnotics.  These drugs appear to differentially act on several brain areas to disrupt, to varying degrees, different components of consciousness.  The ability to recall information, for example, may be disrupted by anesthetics acting on the hippocampal cortex.  Neurons in this region are particularly sensitive to anesthetics at the time loss of recall occurs.  Direct anesthetic actions on hippocampal neurons have been shown to underlie EEG effects that occur in humans and animals during loss of recall (MacIver et al 1996; see also: ).
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. At present, the 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 alcohol, nicotine, Tetrahydrocannabinol (THC), 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 that usually arise only in test conditions. For example, while the left side of the brain can verbally describe what is going on in the right visual field, the right hemisphere is essentially mute, instead relying on its spatial abilities to interact with the world on the left visual field. Some say that 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. This evidence suggests that a functioning thalamus is necessary, but not sufficient, for human consciousness.
Neurophysiological studies in awake, behaving monkeys point to advanced cortical areas in prefrontal cortex and temporal lobes as carriers of neuronal correlates of consciousness. Christof Koch and Francis Crick argued that neuronal mechanisms of consciousness are intricately related to prefrontal cortex  the most advanced cortical area. Experimental work of Steven Wise, Mikhail Lebedev and their colleagues supports this view. They demonstrated that activity of prefrontal cortex neurons reflects illusory perceptions of movements of visual stimuli. Nikos Logothetis and colleagues made similar observations on visually responsive neurons in the temporal lobe. These neurons reflect the visual perception in the situation when conflicting visual images are presented to different eyes (i.e., bistable percepts during binocular rivalry). The studies of blindsight  vision without awareness after lesions to parts of the visual system such as the primary visual cortex  performed by Lawrence Weiskrantz and David P. Carey provided important insights on how conscious perception arises in the brain. In recent years the theory of two visual streams, vision for perception versus vision for action was developed by Melvyn Goodale, David Milner and others. According to this theory, visual perception arises as the result of processing of visual information by the ventral stream areas (located mostly in the temporal lobe), whereas the dorsal stream areas (located mostly in the parietal lobe) process visual information unconsciously. For example, quick catching of the ball would engage mostly the dorsal stream areas, and viewing a painting would be handled by the ventral stream. Overall, these studies show that conscious versus unconscious behaviors can be linked to specific brain areas and patterns of neuronal activation.. However, neuroscience only focuses on the neural correlates of consciousness. The hard problem of consciousness is to explain how all these flows and electrochemical processes in the brain give rise to the inner experience of subjective awareness.

# 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) Quantum mind. 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 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 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, and there are philosophers who argue that QM has no bearing on consciousness.
There is also a concerted effort in the field of Artificial Intelligence to create digital computer programs that can simulate consciousness.

# Functions of consciousness
We generally agree that our fellow human beings are conscious, and that much simpler 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 the extent to which 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, especially survival value. People have therefore looked for specific functions and benefits 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 an important, if not essential, 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 behaviorists, and many philosophers, such as those that support Ryle's approach, would maintain that behavior can be explained by non-conscious processes akin to artificial intelligence, and might consider consciousness to be epiphenomenal or only weakly related to function.
Regarding the primary function of conscious processing, a recurring idea in recent theories is that phenomenal states somehow integrate neural activities and information-processing that would otherwise be independent (see review in Baars, 2002). This has been called the integration consensus. However, it has remained unspecified which kinds of information are integrated in a conscious manner and which kinds can be integrated without consciousness. Obviously not all kinds of information are capable of being disseminated consciously (e.g., neural activity related to vegetative functions, reflexes, unconscious motor programs, low-level perceptual analyses, etc.) and many kinds can be disseminated and combined with other kinds without consciousness, as in intersensory interactions such as the ventriloquism effect (cf., Morsella, 2005).
Ervin Laszlo argues that self-awareness, the ability to make observations of oneself, evolved. Emile Durkheim formulated the concept of so called collective consciousness, which is essential for organization of human, social relations. The accelerating drive of human race to explorations, cognition, understanding and technological progress can be explained by some features of collective consciousness (collective self - concepts) and  collective intelligence

# Tests of consciousness
As there is no clear definition of consciousness and no empirical measure exists to test for its presence, it has been argued that due to the nature of the problem of consciousness, empirical tests are intrinsically impossible.  However, several tests have been developed which attempt to provide an operational definition of consciousness and try to determine whether computers and other non-human animals can demonstrate through their behavior, by passing these tests, that they are conscious.
In medicine, several neurological and brain imaging techniques, like EEG and fMRI, have proven useful for physical measures of brain activity associated with consciousness.  This is particularly true for EEG measures during anesthesia that can provide an indication of anesthetic depth, although with still limited accuracies of ~ 70 % and a high degree of patient and drug variability seen.

## Turing Test
Though often thought of as a test for consciousness, the Turing test (named after computer scientist Alan Turing, who first proposed it) is actually a test to determine whether or not a computer satisfied his operational definition of "intelligent" (which is actually quite different from a test for consciousness or self-awareness). This test is commonly cited in discussion of artificial intelligence.  The essence of the test is based on "the Imitation Game", in which a human experimenter attempts to converse, via computer keyboards, with two others.  One of the others is a human (who, it is assumed, is conscious) while the other is a computer.  Because all of the conversation is via keyboards (teletypes, in Turing's original conception) no cues such as voice, prosody, or appearance will be available to indicate which is the human and which is the computer.  If the human is unable to determine which of the conversants is human, and which is a computer, the computer is said to have "passed" the Turing test (satisfied Turing's operational definition of "intelligent").
The Turing test has generated a great deal of research and philosophical debate. For example, Daniel Dennett and Douglas Hofstadter argue that anything capable of passing the Turing test is necessarily conscious, while David Chalmers, argues that a philosophical zombie could pass the test, yet fail to be conscious.
It has been argued that the question itself is excessively anthropomorphic.  Edsger Dijkstra commented that "The question of whether a computer can think is no more interesting than the question of whether a submarine can swim", expressing the view that different words are appropriate for the workings of a machine to those of animals even if they produce similar results, just as submarines are not normally said to swim.
Philosopher John Searle developed a thought experiment, the Chinese room argument,  which is intended to show problems with the Turing Test.  Searle asks the reader to imagine a non-Chinese speaker in a room in which there are stored a very large number of Chinese symbols and rule books.  Questions are passed to the person in the form of written Chinese symbols via a slot, and the person responds by looking up the symbols and the correct replies in the rule books.  Based on the purely input-output operations, the "Chinese room" gives the appearance of understanding Chinese.  However, the person in the room understands no Chinese at all.  This argument has been the subject of intense philosophical debate since it was introduced in 1980, even leading to edited volumes on this topic alone.
The application of the Turing test to human consciousness has even led to an annual competition, the Loebner Prize with "Grand Prize of $100,000 and a Gold Medal for the first computer whose responses were indistinguishable from a human's."  For a summary of research on the Turing Test, see here.

## Mirror test
See also the concept of the Mirror stage by Jacques Lacan
With the mirror test, devised by Gordon Gallup in the 1970s, one is interested in whether animals are able to recognize themselves in a mirror. The classic example of the test involves placing a spot of coloring on the skin or fur near the individual's forehead and seeing if they attempt to remove it or at least touch the spot, thus indicating that they recognize that the individual they are seeing in the mirror is themselves. Humans (older than 18 months), great apes (except for gorillas), bottlenose dolphins, pigeons , and elephants  have all been observed to pass this test. The test is usually carried out with an identical 'spot' being placed elsewhere on the head with a non-visible material as a control, to assure the subject is not responding to the touch stimuli of the spot's presence. Proponents of the hard problem of consciousness claim that the mirror test only demonstrates that some animals possess a particular cognitive capacity for modelling their environment, but not for the presence of phenomenal consciousness per se.

## Delay test
One problem researchers face is distinguishing nonconscious reflexes and instinctual responses from conscious responses. Neuroscientists Francis Crick and Christof Koch have proposed that by placing a delay between stimulus and execution of action, one may determine the extent of involvement of consciousness in an action of a biological organism.
For example, when psychologists Larry Squire and Robert Clark combined a tone of a specific pitch with a puff of air to the eye, test subjects came to blink their eyes in anticipation of the puff of air when the appropriate tone was played. When the puff of air followed a half of a second later, no such conditioning occurred. When subjects were asked about the experiment, only those who were asked to pay attention could consciously distinguish which tone preceded the puff of air.
Ability to delay the response to an action implies that the information must be stored in short-term memory, which is conjectured to be a closely associated prerequisite for consciousness. However, this test is only valid for biological organisms. While it is simple to create a computer program that passes, such success does not suggest anything beyond a clever programmer.