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{{distinguish|conscientiousness}}{{About|cognition||Consciousness (disambiguation)|and|Conscious (disambiguation)}}{{Good article}}
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Representation of consciousness from the seventeenth century by Robert Fludd, an English Paracelsian physician
Consciousness at its simplest refers to “sentience or awareness of internal or external existence”.DICTIONARY, consciousness, Merriam-Webster, June 4, 2012,weblink Despite centuries of analyses, definitions, explanations and debates by philosophers and scientists, consciousness remains puzzling and controversial,ENCYCLOPEDIA, Robert van Gulick, 2004, Consciousness, Stanford Encyclopedia of Philosophy,weblink Metaphysics Research Lab, Stanford University, being “at once the most familiar and most mysterious aspect of our lives".BOOK, Susan Schneider, Max Velmans, 2008, Introduction, Max Velmans, Susan Schneider, The Blackwell Companion to Consciousness, Wiley, 978-0-470-75145-9, Max Velmans, Perhaps the only widely agreed notion about the topic is the intuition that it exists.BOOK, John Searle, 2005, Honderich T, The Oxford companion to philosophy, Consciousness, Oxford University Press, 978-0-19-926479-7, John Searle, Opinions differ about what exactly needs to be studied and explained as consciousness. Sometimes it is synonymous with 'the mind', other times just an aspect of mind. In the past it was one's “inner life”, the world of introspection, of private thought, imagination and volition.BOOK, Jaynes, Julian, Julian Jaynes, The Origin of Consciousness in the Breakdown of the Bicameral Mind, Houghton Mifflin, 1976, 2000, 0-618-05707-2,weblink Today, with modern research into the brain it often includes any kind of experience, cognition, feeling or perception. It may be ‘awareness’, or 'awareness of awareness’, or self-awareness.JOURNAL, Rochat, Philippe, Five levels of self-awareness as they unfold early in life, Consciousness and Cognition, 2003, 12, 4, 717–731,weblink 10.1016/s1053-8100(03)00081-3, There might be different levels or "orders" of consciousness,WEB, Peter Carruthers, Higher-Order Theories of Consciousness,weblink Stanford Encyclopedia of Philosophy, 31 August 2014, 15 Aug 2011, or different kinds of consciousness, or just one kind with different features.JOURNAL, Michael V. Antony, Is consciousness ambiguous?, Journal of Consciousness Studies, 8, 2001, 19–44, Other questions include whether only humans are conscious or all animals or even the whole universe. The disparate range of research, notions and speculations raises doubts whether the right questions are being asked.JOURNAL, Peter Hacker, Hacker, P.M.S.,weblink pdf, The Sad and Sorry History of Consciousness: being, among other things, a challenge to the "consciousness-studies community", Royal Institute of Philosophy, supplementary volume 70, 2012, Examples of the range of descriptions, definitions or explanations are: simple wakefulness, one's sense of selfhood or soul explored by "looking within", or “nothing at all”; being a metaphorical "stream" of contents, or being a mental state, mental event or mental process of the brain; having phanera or qualia and subjectivity; being the ‘something that it is like' to 'have' or 'be' it; being the “inner theatre” or the executive control system of the mind.BOOK, The Psychology of Consciousness, Farthing G, 1992, Prentice Hall, 978-0-13-728668-3,

Inter-disciplinary perspectives

Western philosophers since the time of Descartes and Locke have struggled to comprehend the nature of consciousness and how it fits into a larger picture of the world. These issues remain central to both continental and analytic philosophy, in phenomenology and the philosophy of mind, respectively. Some basic questions include: whether consciousness is the same kind of thing as matter; whether it may ever be possible for computing machines like computers or robots to be conscious; how consciousness relates to language; how consciousness as Being relates to the world of experience; the role of the self in experience; whether individual thought is possible at all; and whether the concept is fundamentally coherent.Recently, consciousness has also become a significant topic of interdisciplinary research in cognitive science, involving fields such as psychology, linguistics, anthropology,BOOK,weblink Questions of Consciousness, Cohen A.P., Rapport N., Routledge, 1995, 9781134804696, London, neuropsychology and neuroscience. The primary focus is on understanding what it means biologically and psychologically for information to be present in consciousness—that is, on determining the neural and psychological correlates of consciousness. The majority of experimental studies assess consciousness in humans by asking subjects for a verbal report of their experiences (e.g., "tell me if you notice anything when I do this"). Issues of interest include phenomena such as subliminal perception, blindsight, denial of impairment, and altered states of consciousness produced by alcohol and other drugs, or spiritual or meditative techniques.In medicine, consciousness is assessed by observing a patient's arousal and responsiveness, and can be seen as a continuum of states ranging from full alertness and comprehension, through disorientation, delirium, loss of meaningful communication, and finally loss of movement in response to painful stimuli.BOOK, Güven Güzeldere, The Nature of Consciousness: Philosophical debates, 1997, Ned Block, Owen Flanagan, Güven Güzeldere, 1–67, Cambridge, MA, MIT Press, Issues of practical concern include how the presence of consciousness can be assessed in severely ill, comatose, or anesthetized people, and how to treat conditions in which consciousness is impaired or disrupted.JOURNAL, Late recovery from the minimally conscious state: ethical and policy implications, J.J. Fins, N.D. Schiff, K.M. Foley, Neurology, 2007, 68, 304–307, 17242341, 10.1212/01.wnl.0000252376.43779.96, 4, The degree of consciousness is measured by standardized behavior observation scales such as the Glasgow Coma Scale.


File:JohnLocke.png|thumb|John Locke, British Enlightenment philosopher active in the 17th century]]The origin of the modern concept of consciousness is often attributed to John Locke's Essay Concerning Human Understanding, published in 1690.WEB, An Essay Concerning Human Understanding (Chapter XXVII), Locke, John, University of Adelaide, Australia,weblink August 20, 2010, Locke defined consciousness as "the perception of what passes in a man's own mind".ENCYCLOPEDIA,weblink Science & Technology: consciousness, Encyclopædia Britannica, August 20, 2010, His essay influenced the 18th-century view of consciousness, and his definition appeared in Samuel Johnson's celebrated Dictionary (1755).BOOK, A Dictionary of the English Language, Samuel Johnson, Knapton, 1756,weblink Samuel Johnson, "Consciousness" (French: conscience) is also defined in the 1753 volume of Diderot and d'Alembert's Encyclopédie, as "the opinion or internal feeling that we ourselves have from what we do".Jaucourt, Louis, chevalier de. "Consciousness." The Encyclopedia of Diderot & d'Alembert Collaborative Translation Project. Translated by Scott St. Louis. Ann Arbor: Michigan Publishing, University of Michigan Library, 2014. Originally published as "Conscience," Encyclopédie ou Dictionnaire raisonné des sciences, des arts et des métiers, 3:902 (Paris, 1753).The earliest English language uses of "conscious" and "consciousness" date back, however, to the 1500s. The English word "conscious" originally derived from the Latin conscius (con- "together" and (wikt:scio|scio) "to know"), but the Latin word did not have the same meaning as our word—it meant "knowing with", in other words "having joint or common knowledge with another".BOOK, Studies in words, C. S. Lewis, 1990, Cambridge University Press, Ch. 8: Conscience and conscious, 978-0-521-39831-2, C. S. Lewis, There were, however, many occurrences in Latin writings of the phrase conscius sibi, which translates literally as "knowing with oneself", or in other words "sharing knowledge with oneself about something". This phrase had the figurative meaning of "knowing that one knows", as the modern English word "conscious" does. In its earliest uses in the 1500s, the English word "conscious" retained the meaning of the Latin conscius. For example, Thomas Hobbes in Leviathan wrote: "Where two, or more men, know of one and the same fact, they are said to be Conscious of it one to another."BOOK, Leviathan: or, The Matter, Forme & Power of a Commonwealth, Ecclesiasticall and Civill, Thomas Hobbes, University Press, 1904,weblink 39, Thomas Hobbes, The Latin phrase conscius sibi, whose meaning was more closely related to the current concept of consciousness, was rendered in English as "conscious to oneself" or "conscious unto oneself". For example, Archbishop Ussher wrote in 1613 of "being so conscious unto myself of my great weakness".BOOK, The whole works, Volume 2, James Ussher, Charles Richard Elrington, 417, 1613, Hodges and Smith, Locke's definition from 1690 illustrates that a gradual shift in meaning had taken place.A related word was (:la:conscientia|conscientia), which primarily means moral conscience. In the literal sense, "conscientia" means knowledge-with, that is, shared knowledge. The word first appears in Latin juridical texts by writers such as Cicero.BOOK, Dictionary of Untranslatables. A Philosophical Lexicon, Barbara Cassin, Princeton University Press, 978-0-691-13870-1, 2014, 176, Here, conscientia is the knowledge that a witness has of the deed of someone else.JOURNAL, G. Molenaar, Seneca's Use of the Term Conscientia, Mnemosyne, 22, 2, 1969, 170–180, 10.1163/156852569x00670, René Descartes (1596–1650) is generally taken to be the first philosopher to use conscientia in a way that does not fit this traditional meaning.JOURNAL, Boris Hennig, Cartesian Conscientia, British Journal for the History of Philosophy, 2007, 15, 3, 455–484, 10.1080/09608780701444915, Descartes used conscientia the way modern speakers would use "conscience". In Search after Truth (, Amsterdam 1701) he says "conscience or internal testimony" (conscientiâ, vel interno testimonio).Charles Adam, Paul Tannery (eds.), Oeuvres de Descartes X, 524 (1908).BOOK, 205–206, Consciousness: from perception to reflection in the history of philosophy, 978-1-4020-6081-6, Springer, Sara Heinämaa, Vili Lähteenmäki, Pauliina Remes, 2007,

Dictionary definitions

The dictionary meanings of the word consciousness extend through several centuries and several associated related meanings. These have ranged from formal definitions to definitions attempting to capture the less easily captured and more debated meanings and usage of the word.One formal definition indicating the range of these related meanings is given in Webster's Third New International Dictionary stating that consciousness is:
    • awareness or perception of an inward psychological or spiritual fact: intuitively perceived knowledge of something in one's inner self
    • inward awareness of an external object, state, or fact
    • concerned awareness: INTEREST, CONCERN—often used with an attributive noun.
  1. the state or activity that is characterized by sensation, emotion, volition, or thought: mind in the broadest possible sense: something in nature that is distinguished from the physical.
  2. the totality in psychology of sensations, perceptions, ideas, attitudes and feelings of which an individual or a group is aware at any given time or within a particular time span—compare STREAM OF CONSCIOUSNESS."
The Cambridge Dictionary defines consciousness as "the state of understanding and realizing something."WEB,weblink CONSCIOUSNESS – meaning in the Cambridge English Dictionary,, The Oxford Living Dictionary defines consciousness as "The state of being aware of and responsive to one's surroundings.", "A person's awareness or perception of something." and "The fact of awareness by the mind of itself and the world."WEB,weblink consciousness – Definition of consciousness in English by Oxford Dictionaries, Oxford Dictionaries – English, Most definitions include awareness, but some include a more general state of being.

Philosophy of mind

The philosophy of mind has given rise to many stances regarding consciousness. The Routledge Encyclopedia of Philosophy in 1998 defines consciousness as follows:}}In a more skeptical definition of consciousness, Stuart Sutherland has exemplified some of the difficulties in fully ascertaining all of its cognate meanings in his entry for the 1989 version of the Macmillan Dictionary of Psychology:}}Most writers on the philosophy of consciousness have been concerned with defending a particular point of view, and have organized their material accordingly. For surveys, the most common approach is to follow a historical path by associating stances with the philosophers who are most strongly associated with them, for example Descartes, Locke, Kant, etc. An alternative is to organize philosophical stances according to basic issues.

The coherence of the concept

Many philosophers have argued that consciousness is a unitary concept that is understood intuitively by the majority of people in spite of the difficulty in defining it. Others, though, have argued that the level of disagreement about the meaning of the word indicates that it either means different things to different people (for instance, the objective versus subjective aspects of consciousness), or else it encompasses a variety of distinct meanings with no simple element in common.JOURNAL, Max Velmans, How to define consciousness—and how not to define consciousness, Journal of Consciousness Studies, 2009, 16, 139–156, Max Velmans, Philosophers differ from non-philosophers in their intuitions about what consciousness is.JOURNAL, Justin Sytsma, Edouard Machery, Two conceptions of subjective experience, Philosophical Studies, 2010, 151, 2, 299–327, 10.1007/s11098-009-9439-x,weblink While most people have a strong intuition for the existence of what they refer to as consciousness, skeptics argue that this intuition is false, either because the concept of consciousness is intrinsically incoherent, or because our intuitions about it are based in illusions. Gilbert Ryle, for example, argued that traditional understanding of consciousness depends on a Cartesian dualist outlook that improperly distinguishes between mind and body, or between mind and world. He proposed that we speak not of minds, bodies, and the world, but of individuals, or persons, acting in the world. Thus, by speaking of "consciousness" we end up misleading ourselves by thinking that there is any sort of thing as consciousness separated from behavioral and linguistic understandings.BOOK, The Concept of Mind, Gilbert Ryle, University of Chicago Press, 1949, 156–163, 978-0-226-73296-1, The Concept of Mind, Gilbert Ryle, More generally, many philosophers and scientists have been unhappy about the difficulty of producing a definition that does not involve circularity or fuzziness.

Types of consciousness

Ned Block proposed a distinction between two types of consciousness that he called phenomenal (P-consciousness) and access (A-consciousness).BOOK, The Nature of Consciousness: Philosophical Debates, N. Block, O. Flanagan, G. Guzeldere, On a confusion about a function of consciousness, Ned Block, 375–415, 1998, 978-0-262-52210-6, MIT Press,weblink Ned Block, P-consciousness, according to Block, is simply raw experience: it is moving, colored 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. A-consciousness, on the other hand, 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 access conscious; when we introspect, information about our thoughts is access conscious; when we remember, information about the past is access conscious, and so on. Although some philosophers, such as Daniel Dennett, have disputed the validity of this distinction,BOOK, Daniel Dennett, 2004, Consciousness Explained, 375, Penguin, 978-0-7139-9037-9, Consciousness Explained, Daniel Dennett, others have broadly accepted it. David Chalmers has argued that A-consciousness can in principle be understood in mechanistic terms, but that understanding P-consciousness is much more challenging: he calls this the hard problem of consciousness.JOURNAL,weblink Facing up to the problem of consciousness, David Chalmers, Journal of Consciousness Studies, 2, 1995, 200–219, dead,weblink" title="">weblink 2005-03-08, David Chalmers, Some philosophers believe that Block's two types of consciousness are not the end of the story. William Lycan, for example, argued in his book Consciousness and Experience that at least eight clearly distinct types of consciousness can be identified (organism consciousness; control consciousness; consciousness of; state/event consciousness; reportability; introspective consciousness; subjective consciousness; self-consciousness)—and that even this list omits several more obscure forms.BOOK, William Lycan, Consciousness and Experience, 1–4, 1996, MIT Press, 978-0-262-12197-2, William Lycan, There is also debate over whether or not A-consciousness and P-consciousness always coexist or if they can exist separately. Although P-consciousness without A-consciousness is more widely accepted, there have been some hypothetical examples of A without P. Block for instance suggests the case of a “zombie” that is computationally identical to a person but without any subjectivity. However, he remains somewhat skeptical concluding "I don’t know whether there are any actual cases of A-consciousness without P-consciousness, but I hope I have illustrated their conceptual possibility." JOURNAL, Block N, 1995, How many concepts of consciousness?, Behavioral and Brain Sciences, 18, 2, 272–284, 10.1017/s0140525x00038486,

Mind–body problem

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Illustration of dualism by René Descartes. Inputs are passed by the sensory organs to the pineal gland and from there to the immaterial spirit.
Mental processes (such as consciousness) and physical processes (such as brain events) seem to be correlated, however the specific nature of the connection is unknown.The first influential philosopher to discuss this question specifically was Descartes, and the answer he gave is known as Cartesian dualism. Descartes proposed that consciousness resides within an immaterial domain he called res cogitans (the realm of thought), in contrast to the domain of material things, which he called res extensa (the realm of extension).BOOK, Philosophy of Man: selected readings, Dy, Jr., Manuel B., Goodwill Trading Co., 2001, 978-971-12-0245-3, 97, He suggested that the interaction between these two domains occurs inside the brain, perhaps in a small midline structure called the pineal gland.WEB, Descartes and the Pineal Gland, Stanford University, November 5, 2008,weblink 2010-08-22, Although it is widely accepted that Descartes explained the problem cogently, few later philosophers have been happy with his solution, and his ideas about the pineal gland have especially been ridiculed.WEB, Descartes and the pineal gland, Gert-Jan Lokhorst, Stanford Encyclopedia of Philosophy (Summer 2011 Edition), Edward N. Zalta,weblink However, no alternative solution has gained general acceptance. Proposed solutions can be divided broadly into two categories: dualist solutions that maintain Descartes' rigid distinction between the realm of consciousness and the realm of matter but give different answers for how the two realms relate to each other; and monist solutions that maintain that there is really only one realm of being, of which consciousness and matter are both aspects. Each of these categories itself contains numerous variants. The two main types of dualism are substance dualism (which holds that the mind is formed of a distinct type of substance not governed by the laws of physics) and property dualism (which holds that the laws of physics are universally valid but cannot be used to explain the mind). The three main types of monism are physicalism (which holds that the mind consists of matter organized in a particular way), idealism (which holds that only thought or experience truly exists, and matter is merely an illusion), and neutral monism (which holds that both mind and matter are aspects of a distinct essence that is itself identical to neither of them). There are also, however, a large number of idiosyncratic theories that cannot cleanly be assigned to any of these schools of thought.BOOK, William Jaworski, Philosophy of Mind: A Comprehensive Introduction, John Wiley and Sons, 2011, 978-1-4443-3367-1, 5–11, Since the dawn of Newtonian science with its vision of simple mechanical principles governing the entire universe, some philosophers have been tempted by the idea that consciousness could be explained in purely physical terms. The first influential writer to propose such an idea explicitly was Julien Offray de La Mettrie, in his book Man a Machine (L'homme machine). His arguments, however, were very abstract.BOOK, Ann Thomson, Julien Offray de La Mettrie, Machine man and other writings, Cambridge University Press, 1996, 978-0-521-47849-6, Julien Offray de La Mettrie, The most influential modern physical theories of consciousness are based on psychology and neuroscience. Theories proposed by neuroscientists such as Gerald EdelmanBOOK, Bright Air, Brilliant Fire: On the Matter of the Mind, Gerald Edelman, Basic Books, 1993, 978-0-465-00764-6, Gerald Edelman, and Antonio Damasio,BOOK, Antonio Damasio, 1999, The Feeling of What Happens: Body and Emotion in the Making of Consciousness, New York, Harcourt Press, 978-0-15-601075-7, Antonio Damasio,weblink and by philosophers such as Daniel Dennett,BOOK, Daniel Dennett, 1991, Consciousness Explained,weblink registration, Boston, Little & Company, 978-0-316-18066-5, Daniel Dennett, seek to explain consciousness in terms of neural events occurring within the brain. Many other neuroscientists, such as Christof Koch,BOOK, Christof Koch, 2004, The Quest for Consciousness, Englewood, CO, Roberts & Company, 978-0-9747077-0-9, Christof Koch, have explored the neural basis of consciousness without attempting to frame all-encompassing global theories. At the same time, computer scientists working in the field of artificial intelligence have pursued the goal of creating digital computer programs that can simulate or embody consciousness.Ron Sun and Stan Franklin, Computational models of consciousness: A taxonomy and some examples. In: P.D. Zelazo, M. Moscovitch, and E. Thompson (eds.), The Cambridge Handbook of Consciousness, pp. 151–174. Cambridge University Press, New York. 2007A few theoretical physicists have argued that classical physics is intrinsically incapable of explaining the holistic aspects of consciousness, but that quantum theory may provide the missing ingredients. Several theorists have therefore proposed quantum mind (QM) theories of consciousness.BOOK, Quantum Approaches to Consciousness, Stanford University, December 25, 2011,weblink Notable theories falling into this category include the holonomic brain theory of Karl Pribram and David Bohm, and the Orch-OR theory formulated by Stuart Hameroff and Roger Penrose. Some of these QM theories offer descriptions of phenomenal consciousness, as well as QM interpretations of access consciousness. None of the quantum mechanical theories have been confirmed by experiment. Recent publications by G. Guerreshi, J. Cia, S. Popescu, and H. BriegelJOURNAL, 10.1103/PhysRevE.82.021921, 20866851, Cai, J., Popescu, S., Briegel, H., Persistent dynamic entanglement from classical motion: How bio-molecular machines can generate non-trivial quantum states, Physical Review E, 82, 2, 021921, 0809.4906, 2010PhRvE..82b1921C, 2010, could falsify proposals such as those of Hameroff, which rely on quantum entanglement in protein. At the present time many scientists and philosophers consider the arguments for an important role of quantum phenomena to be unconvincing.BOOK, John Searle, 1997, The Mystery of Consciousness, The New York Review of Books, 53–88, 978-0-940322-06-6, John Searle, Apart from the general question of the "hard problem" of consciousness, roughly speaking, the question of how mental experience arises from a physical basis,For a discussion see BOOK, The Consciousness Paradox: Consciousness, Concepts, and Higher-Order Thoughts, Rocco J. Gennaro,weblink 75, §4.4 The hard problem of consciousness, 978-0-262-01660-5, 2011, MIT Press,
a more specialized question is how to square the subjective notion that we are in control of our decisions (at least in some small measure) with the customary view of causality that subsequent events are caused by prior events. The topic of free will is the philosophical and scientific examination of this conundrum.

Problem of other minds

Many philosophers consider experience to be the essence of consciousness, and believe that experience can only fully be known from the inside, subjectively. But if consciousness is subjective and not visible from the outside, why do the vast majority of people believe that other people are conscious, but rocks and trees are not?JOURNAL, Knobe J, 2008, Can a Robot, an Insect or God Be Aware?, Scientific American Mind,weblink 10.1038/scientificamericanmind1208-68, 19, 6, 68–71, This is called the problem of other minds.BOOK, Alec Hyslop, Other Minds, 1995, Springer, 978-0-7923-3245-9, 5–14, It is particularly acute for people who believe in the possibility of philosophical zombies, that is, people who think it is possible in principle to have an entity that is physically indistinguishable from a human being and behaves like a human being in every way but nevertheless lacks consciousness.WEB, Robert Kirk, Zombies, Stanford Encyclopedia of Philosophy (Summer 2009 Edition), Edward N. Zalta,weblink Related issues have also been studied extensively by Greg Littmann of the University of Illinois,The Culture and Philosophy of Ridley Scott, Greg Littmann, pp. 133–144, Lexington Books (2013). and Colin Allen a professor at Indiana University regarding the literature and research studying artificial intelligence in androids.Moral Machines, Wendell Wallach and Colin Allen, 288 pages, Oxford University Press, USA (June 3, 2010), {{ISBN|0-19-973797-5}}.The most commonly given answer is that we attribute consciousness to other people because we see that they resemble us in appearance and behavior; we reason that if they look like us and act like us, they must be like us in other ways, including having experiences of the sort that we do. There are, however, a variety of problems with that explanation. For one thing, it seems to violate the principle of parsimony, by postulating an invisible entity that is not necessary to explain what we observe.BOOK, Alec Hyslop, The analogical inference to other minds, Other Minds, 1995, Springer, 978-0-7923-3245-9, 41–70, Some philosophers, such as Daniel Dennett in an essay titled The Unimagined Preposterousness of Zombies, argue that people who give this explanation do not really understand what they are saying.JOURNAL, Daniel Dennett, The unimagined preposterousness of zombies, Journal of Consciousness Studies, 2, 1995, 322–325, Daniel Dennett, More broadly, philosophers who do not accept the possibility of zombies generally believe that consciousness is reflected in behavior (including verbal behavior), and that we attribute consciousness on the basis of behavior. A more straightforward way of saying this is that we attribute experiences to people because of what they can do, including the fact that they can tell us about their experiences.JOURNAL, Stevan Harnad, Why and how we are not zombies, Journal of Consciousness Studies, 1995, 1, 164–167, Stevan Harnad,

Animal consciousness

{{see also|Animal consciousness}}The topic of animal consciousness is beset by a number of difficulties. It poses the problem of other minds in an especially severe form, because non-human animals, lacking the ability to express human language, cannot tell humans about their experiences.WEB, Colin Allen, Animal consciousness, Stanford Encyclopedia of Philosophy (Summer 2011 Edition), Edward N. Zalta,weblink Also, it is difficult to reason objectively about the question, because a denial that an animal is conscious is often taken to imply that it does not feel, its life has no value, and that harming it is not morally wrong. Descartes, for example, has sometimes been blamed for mistreatment of animals due to the fact that he believed only humans have a non-physical mind.JOURNAL, Peter Carruthers, Sympathy and subjectivity, Australasian Journal of Philosophy, 1999, 77, 4, 465–482, 10.1080/00048409912349231, Peter Carruthers (philosopher), Most people have a strong intuition that some animals, such as cats and dogs, are conscious, while others, such as insects, are not; but the sources of this intuition are not obvious, and are often based on personal interactions with pets and other animals they have observed.Philosophers who consider subjective experience the essence of consciousness also generally believe, as a correlate, that the existence and nature of animal consciousness can never rigorously be known. Thomas Nagel spelled out this point of view in an influential essay titled What Is it Like to Be a Bat?. He said that an organism is conscious "if and only if there is something that it is like to be that organism—something it is like for the organism"; and he argued that no matter how much we know about an animal's brain and behavior, we can never really put ourselves into the mind of the animal and experience its world in the way it does itself.BOOK, Thomas Nagel, Mortal Questions, Ch. 12 What is it like to be a bat?, Cambridge University Press, 1991, 978-0-521-40676-5, Thomas Nagel, Other thinkers, such as Douglas Hofstadter, dismiss this argument as incoherent.BOOK, Douglas Hofstadter, Reflections on What Is It Like to Be a Bat?, 403–414, The Mind's I, Douglas Hofstadter, Daniel Dennett, Basic Books, 1981, 978-0-7108-0352-8, The Mind's I, Douglas Hofstadter, Several psychologists and ethologists have argued for the existence of animal consciousness by describing a range of behaviors that appear to show animals holding beliefs about things they cannot directly perceive—Donald Griffin's 2001 book Animal Minds reviews a substantial portion of the evidence.BOOK, Animal Minds: Beyond Cognition to Consciousness, Donald Griffin, University of Chicago Press, 2001, 978-0-226-30865-4, Donald Griffin, On July 7, 2012, eminent scientists from different branches of neuroscience gathered at the University of Cambridge to celebrate the Francis Crick Memorial Conference, which deals with consciousness in humans and pre-linguistic consciousness in nonhuman animals. After the conference, they signed in the presence of Stephen Hawking, the 'Cambridge Declaration on Consciousness', which summarizes the most important findings of the survey:"We decided to reach a consensus and make a statement directed to the public that is not scientific. It's obvious to everyone in this room that animals have consciousness, but it is not obvious to the rest of the world. It is not obvious to the rest of the Western world or the Far East. It is not obvious to the society."AV MEDIA,weblink Animal Consciousness Officially Recognized by Leading Panel of Neuroscientists, 3 September 2012, YouTube, "Convergent evidence indicates that non-human animals [...], including all mammals and birds, and other creatures, [...] have the necessary neural substrates of consciousness and the capacity to exhibit intentional behaviors."WEB,weblink Cambridge Declaration on Consciousness,

Artifact consciousness

{{see also|Artificial consciousness}}The idea of an (wikt:artifact|artifact) made conscious is an ancient theme of mythology, appearing for example in the Greek myth of Pygmalion, who carved a statue that was magically brought to life, and in medieval Jewish stories of the Golem, a magically animated homunculus built of clay.BOOK, Moshe Idel, Golem: Jewish Magical and Mystical Traditions on the Artificial Anthropoid, 1990, SUNY Press, 978-0-7914-0160-6, Note: In many stories the Golem was mindless, but some gave it emotions or thoughts. However, the possibility of actually constructing a conscious machine was probably first discussed by Ada Lovelace, in a set of notes written in 1842 about the Analytical Engine invented by Charles Babbage, a precursor (never built) to modern electronic computers. Lovelace was essentially dismissive of the idea that a machine such as the Analytical Engine could think in a humanlike way. She wrote:}}One of the most influential contributions to this question was an essay written in 1950 by pioneering computer scientist Alan Turing, titled Computing Machinery and Intelligence. Turing disavowed any interest in terminology, saying that even "Can machines think?" is too loaded with spurious connotations to be meaningful; but he proposed to replace all such questions with a specific operational test, which has become known as the Turing test.BOOK, Stuart Shieber, The Turing Test : Verbal Behavior as the Hallmark of Intelligence, MIT Press, 2004, 978-0-262-69293-9, To pass the test, a computer must be able to imitate a human well enough to fool interrogators. In his essay Turing discussed a variety of possible objections, and presented a counterargument to each of them. The Turing test is commonly cited in discussions of artificial intelligence as a proposed criterion for machine consciousness; it has provoked a great deal of philosophical debate. For example, Daniel Dennett and Douglas Hofstadter argue that anything capable of passing the Turing test is necessarily conscious,BOOK, Daniel Dennett, Douglas Hofstadter, 1985, The Mind's I, Basic Books, 978-0-553-34584-1, Douglas Hofstadter, Daniel Dennett,weblink while David Chalmers argues that a philosophical zombie could pass the test, yet fail to be conscious.BOOK, David Chalmers, 1997, The Conscious Mind: In Search of a Fundamental Theory, Oxford University Press, 978-0-19-511789-9, David Chalmers, A third group of scholars have argued that with technological growth once machines begin to display any substantial signs of human-like behavior then the dichotomy (of human consciousness compared to human-like consciousness) becomes passé and issues of machine autonomy begin to prevail even as observed in its nascent form within contemporary industry and technology. Jürgen Schmidhuber argues that consciousness is simply the result of compression.BOOK, Jürgen Schmidhuber, 2009, Driven by Compression Progress: A Simple Principle Explains Essential Aspects of Subjective Beauty, Novelty, Surprise, Interestingness, Attention, Curiosity, Creativity, Art, Science, Music, Jokes,weblink Jürgen Schmidhuber, 2008arXiv0812.4360S, 0812.4360, As an agent sees representation of itself recurring in the environment, the compression of this representation can be called consciousness.(File:John searle2.jpg|thumb|John Searle in December 2005)In a lively exchange over what has come to be referred to as "the Chinese room argument", John Searle sought to refute the claim of proponents of what he calls "strong artificial intelligence (AI)" that a computer program can be conscious, though he does agree with advocates of "weak AI" that computer programs can be formatted to "simulate" conscious states. His own view is that consciousness has subjective, first-person causal powers by being essentially intentional due simply to the way human brains function biologically; conscious persons can perform computations, but consciousness is not inherently computational the way computer programs are. To make a Turing machine that speaks Chinese, Searle imagines a room with one monolingual English speaker (Searle himself, in fact), a book that designates a combination of Chinese symbols to be output paired with Chinese symbol input, and boxes filled with Chinese symbols. In this case, the English speaker is acting as a computer and the rulebook as a program. Searle argues that with such a machine, he would be able to process the inputs to outputs perfectly without having any understanding of Chinese, nor having any idea what the questions and answers could possibly mean. If the experiment were done in English, since Searle knows English, he would be able to take questions and give answers without any algorithms for English questions, and he would be effectively aware of what was being said and the purposes it might serve. Searle would pass the Turing test of answering the questions in both languages, but he is only conscious of what he is doing when he speaks English. Another way of putting the argument is to say that computer programs can pass the Turing test for processing the syntax of a language, but that the syntax cannot lead to semantic meaning in the way strong AI advocates hoped.JOURNAL, John R. Searle, Is the brain's mind a computer program, Scientific American, 1990, 262, 1, 26–31,weblink 10.1038/scientificamerican0190-26, 2294583, 1990SciAm.262a..26S, John R. Searle, BOOK, The Chinese Room Argument,weblink Metaphysics Research Lab, Stanford University, 2019, In the literature concerning artificial intelligence, Searle's essay has been second only to Turing's in the volume of debate it has generated.JOURNAL, John Searle, Minds, brains, and programs, Behavioral and Brain Sciences, 1980, 3, 3, 417–457, 10.1017/S0140525X00005756, etal,, John Searle, Searle himself was vague about what extra ingredients it would take to make a machine conscious: all he proposed was that what was needed was "causal powers" of the sort that the brain has and that computers lack. But other thinkers sympathetic to his basic argument have suggested that the necessary (though perhaps still not sufficient) extra conditions may include the ability to pass not just the verbal version of the Turing test, but the robotic version,WEB, Graham Oppy, David Dowe, 2011, The Turing test,weblink Stanford Encyclopedia of Philosophy (Spring 2011 Edition), which requires grounding the robot's words in the robot's sensorimotor capacity to categorize and interact with the things in the world that its words are about, Turing-indistinguishably from a real person. Turing-scale robotics is an empirical branch of research on embodied cognition and situated cognition.JOURNAL, Margaret Wilson, Six views of embodied cognition, Psychonomic Bulletin & Review, 9, 4, 2002, 625–636,weblink 10.3758/BF03196322, dead,weblink" title="">weblink 2011-09-27, In 2014, Victor Argonov has suggested a non-Turing test for machine consciousness based on machine's ability to produce philosophical judgments.JOURNAL, Victor Argonov, Experimental Methods for Unraveling the Mind-body Problem: The Phenomenal Judgment Approach, Journal of Mind and Behavior, 35, 2014, 51–70,weblink He argues that a deterministic machine must be regarded as conscious if it is able to produce judgments on all problematic properties of consciousness (such as qualia or binding) having no innate (preloaded) philosophical knowledge on these issues, no philosophical discussions while learning, and no informational models of other creatures in its memory (such models may implicitly or explicitly contain knowledge about these creatures’ consciousness). However, this test can be used only to detect, but not refute the existence of consciousness. A positive result proves that machine is conscious but a negative result proves nothing. For example, absence of philosophical judgments may be caused by lack of the machine's intellect, not by absence of consciousness.

Scientific study

For many decades, consciousness as a research topic was avoided by the majority of mainstream scientists, because of a general feeling that a phenomenon defined in subjective terms could not properly be studied using objective experimental methods.BOOK, Horst Hendriks-Jansen, Catching ourselves in the act: situated activity, interactive emergence, evolution, and human thought, 1996, Massachusetts Institute of Technology, 114, 978-0-262-08246-4, In 1975 George Mandler published an influential psychological study which distinguished between slow, serial, and limited conscious processes and fast, parallel and extensive unconscious ones.Mandler, G. "Consciousness: Respectable, useful, and probably necessary". In R. Solso (Ed.) Information processing and cognition: NJ: LEA. Starting in the 1980s, an expanding community of neuroscientists and psychologists have associated themselves with a field called Consciousness Studies, giving rise to a stream of experimental work published in books,Mandler, G. Consciousness recovered: Psychological functions and origins of thought. Philadelphia: John Benjamins. 2002 journals such as Consciousness and Cognition, Frontiers in Consciousness Research, Psyche, and the Journal of Consciousness Studies, along with regular conferences organized by groups such as the Association for the Scientific Study of ConsciousnessBOOK, Toward a Science of Consciousness III: The Third Tucson Discussions and Debates, Stuart Hameroff, Alfred Kaszniak, David Chalmers, David Chalmers, Preface, 978-0-262-58181-3, MIT Press, 1999, xix–xx, Stuart Hameroff, and the Society for Consciousness Studies.Modern medical and psychological investigations into consciousness are based on psychological experiments (including, for example, the investigation of priming effects using subliminal stimuli), and on case studies of alterations in consciousness produced by trauma, illness, or drugs. Broadly viewed, scientific approaches are based on two core concepts. The first identifies the content of consciousness with the experiences that are reported by human subjects; the second makes use of the concept of consciousness that has been developed by neurologists and other medical professionals who deal with patients whose behavior is impaired. In either case, the ultimate goals are to develop techniques for assessing consciousness objectively in humans as well as other animals, and to understand the neural and psychological mechanisms that underlie it.


File:Necker cube.svg|thumb|right|150px|The Necker cubeNecker cubeExperimental research on consciousness presents special difficulties, due to the lack of a universally accepted operational definition. In the majority of experiments that are specifically about consciousness, the subjects are human, and the criterion used is verbal report: in other words, subjects are asked to describe their experiences, and their descriptions are treated as observations of the contents of consciousness.BOOK, Bernard Baars, A Cognitive Theory of Consciousness, 1993, Cambridge University Press, 978-0-521-42743-2, 15–18, Bernard Baars, For example, subjects who stare continuously at a Necker cube usually report that they experience it "flipping" between two 3D configurations, even though the stimulus itself remains the same.BOOK, Perception: Theory, Development, and Organization, Paul Rooks, Jane Wilson, 2000, Psychology Press, 978-0-415-19094-7, 25–26, The objective is to understand the relationship between the conscious awareness of stimuli (as indicated by verbal report) and the effects the stimuli have on brain activity and behavior. In several paradigms, such as the technique of response priming, the behavior of subjects is clearly influenced by stimuli for which they report no awareness, and suitable experimental manipulations can lead to increasing priming effects despite decreasing prime identification (double dissociation).JOURNAL, Thomas Schmidt, Dirk Vorberg, Criteria for unconscious cognition: Three types of dissociation, Perception and Psychophysics, 68, 2006, 489–504, 10.3758/bf03193692, 16900839, 3, Verbal report is widely considered to be the most reliable indicator of consciousness, but it raises a number of issues. For one thing, if verbal reports are treated as observations, akin to observations in other branches of science, then the possibility arises that they may contain errors—but it is difficult to make sense of the idea that subjects could be wrong about their own experiences, and even more difficult to see how such an error could be detected.BOOK, Quining qualia, Daniel Dennett, Consciousness in Modern Science, A. Marcel, E. Bisiach, Oxford University Press, 1992,weblink 2011-10-31, 978-0-19-852237-9, Daniel Dennett, Daniel Dennett has argued for an approach he calls heterophenomenology, which means treating verbal reports as stories that may or may not be true, but his ideas about how to do this have not been widely adopted.JOURNAL, Daniel Dennett, 2003, Who's on first? Heterophenomenology explained, Journal of Consciousness Studies, 10, 19–30, Daniel Dennett, Another issue with verbal report as a criterion is that it restricts the field of study to humans who have language: this approach cannot be used to study consciousness in other species, pre-linguistic children, or people with types of brain damage that impair language. As a third issue, philosophers who dispute the validity of the Turing test may feel that it is possible, at least in principle, for verbal report to be dissociated from consciousness entirely: a philosophical zombie may give detailed verbal reports of awareness in the absence of any genuine awareness.BOOK, David Chalmers, The Conscious Mind,weblink registration, 1996, Ch. 3: Can consciousness be reductively explained?, Oxford University Press, 978-0-19-511789-9, David Chalmers, Although verbal report is in practice the "gold standard" for ascribing consciousness, it is not the only possible criterion.BOOK, The Boundaries of Consciousness: Neurobiology and Neuropathology, Methods for studying unconscious learning, Arnaud Destrebecqz, Philippe Peigneux, Steven Laureys, 2006, Elsevier, 978-0-444-52876-6, 69–80, In medicine, consciousness is assessed as a combination of verbal behavior, arousal, brain activity and purposeful movement. The last three of these can be used as indicators of consciousness when verbal behavior is absent. The scientific literature regarding the neural bases of arousal and purposeful movement is very extensive. Their reliability as indicators of consciousness is disputed, however, due to numerous studies showing that alert human subjects can be induced to behave purposefully in a variety of ways in spite of reporting a complete lack of awareness. Studies of the neuroscience of free will have also shown that the experiences that people report when they behave purposefully sometimes do not correspond to their actual behaviors or to the patterns of electrical activity recorded from their brains.JOURNAL, Human volition: towards a neuroscience of will, Patrick Haggard, Nature Reviews Neuroscience, 2008, 9, 934–946, 19020512, 10.1038/nrn2497, 12, Another approach applies specifically to the study of self-awareness, that is, the ability to distinguish oneself from others. In the 1970s Gordon Gallup developed an operational test for self-awareness, known as the mirror test. The test examines whether animals are able to differentiate between seeing themselves in a mirror versus seeing other animals. The classic example 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.JOURNAL, Gordon Gallup, Chimpanzees: Self recognition, Science, 167, 86–87, 1970, 10.1126/science.167.3914.86, 4982211, 3914, 1970Sci...167...86G, Gordon G. Gallup, Humans (older than 18 months) and other great apes, bottlenose dolphins, killer whales, pigeons, European magpies and elephants have all been observed to pass this test.JOURNAL, Animal consciousness: a synthetic approach, David Edelman, Anil Seth, Trends in Neurosciences, 2009, 32, 476–484, 19716185, 10.1016/j.tins.2009.05.008, 9,

Neural correlates

File:Neural Correlates Of Consciousness.jpg|thumb|right|550px|{{center|Schema of the neural processes underlying consciousness, from Christof KochChristof KochA major part of the scientific literature on consciousness consists of studies that examine the relationship between the experiences reported by subjects and the activity that simultaneously takes place in their brains—that is, studies of the neural correlates of consciousness. The hope is to find that activity in a particular part of the brain, or a particular pattern of global brain activity, which will be strongly predictive of conscious awareness. Several brain imaging techniques, such as EEG and fMRI, have been used for physical measures of brain activity in these studies.BOOK, Christof Koch, 2004, The Quest for Consciousness, Englewood, CO, Roberts & Company, 978-0-9747077-0-9, 16–19, Christof Koch, Another idea that has drawn attention for several decades is that consciousness is associated with high-frequency (gamma band) oscillations in brain activity. This idea arose from proposals in the 1980s, by Christof von der Malsburg and Wolf Singer, that gamma oscillations could solve the so-called binding problem, by linking information represented in different parts of the brain into a unified experience.JOURNAL, Binding by synchrony, Wolf Singer, Scholarpedia, 2, 12, 1657, 10.4249/scholarpedia.1657, 2007, 2007SchpJ...2.1657S, Rodolfo Llinás, for example, proposed that consciousness results from recurrent thalamo-cortical resonance where the specific thalamocortical systems (content) and the non-specific (centromedial thalamus) thalamocortical systems (context) interact in the gamma band frequency via synchronous oscillations.BOOK, Rodolfo Llinás, 2002, I of the vortex: from neurons to self, MIT Press, 978-0-262-62163-2, Rodolfo Llinás, I of the vortex: from neurons to self, A number of studies have shown that activity in primary sensory areas of the brain is not sufficient to produce consciousness: it is possible for subjects to report a lack of awareness even when areas such as the primary visual cortex show clear electrical responses to a stimulus.Koch, The Quest for Consciousness, pp. 105–116 Higher brain areas are seen as more promising, especially the prefrontal cortex, which is involved in a range of higher cognitive functions collectively known as executive functions. There is substantial evidence that a "top-down" flow of neural activity (i.e., activity propagating from the frontal cortex to sensory areas) is more predictive of conscious awareness than a "bottom-up" flow of activity.JOURNAL, A framework for consciousness, Francis Crick, Christof Koch, 2003, Nature Neuroscience, 6, 119–126, 12555104,weblink 10.1038/nn0203-119, 2, dead,weblink" title="">weblink 2012-05-22, Christof Koch, Francis Crick, The prefrontal cortex is not the only candidate area, however: studies by Nikos Logothetis and his colleagues have shown, for example, that visually responsive neurons in parts of the temporal lobe reflect the visual perception in the situation when conflicting visual images are presented to different eyes (i.e., bistable percepts during binocular rivalry).Koch, The Quest for Consciousness, pp. 269–286Modulation of neural responses may correlate with phenomenal experiences. In contrast to the raw electrical responses that do not correlate with consciousness, the modulation of these responses by other stimuli correlates surprisingly well with an important aspect of consciousness: namely with the phenomenal experience of stimulus intensity (brightness, contrast). In the research group of Danko Nikolić it has been shown that some of the changes in the subjectively perceived brightness correlated with the modulation of firing rates while others correlated with the modulation of neural synchrony.JOURNAL, Biederlack J., Castelo-Branco M., Neuenschwander S., Wheeler D.W., Singer W., Nikolić D., 2006, Brightness induction: Rate enhancement and neuronal synchronization as complementary codes, Neuron, 52, 6, 1073–1083, 10.1016/j.neuron.2006.11.012, 17178409, An fMRI investigation suggested that these findings were strictly limited to the primary visual areas.JOURNAL, Williams Adrian L., Singh Krishna D., Smith Andrew T., 2003, Surround modulation measured with functional MRI in the human visual cortex, Journal of Neurophysiology, 89, 1, 525–533, 10.1152/jn.00048.2002, 12522199,, This indicates that, in the primary visual areas, changes in firing rates and synchrony can be considered as neural correlates of qualia—at least for some type of qualia.In 2011, Graziano and KastnerJOURNAL, Graziano, M.S.A., Kastner, S, 2011, Human consciousness and its relationship to social neuroscience: A novel hypothesis, Cog. Neurosci, 2, 2, 98–113, 10.1080/17588928.2011.565121, 22121395, 3223025, proposed the "attention schema" theory of awareness. In that theory, specific cortical areas, notably in the superior temporal sulcus and the temporo-parietal junction, are used to build the construct of awareness and attribute it to other people. The same cortical machinery is also used to attribute awareness to oneself. Damage to these cortical regions can lead to deficits in consciousness such as hemispatial neglect. In the attention schema theory, the value of explaining the feature of awareness and attributing it to a person is to gain a useful predictive model of that person's attentional processing. Attention is a style of information processing in which a brain focuses its resources on a limited set of interrelated signals. Awareness, in this theory, is a useful, simplified schema that represents attentional states. To be aware of X is explained by constructing a model of one's attentional focus on X.In 2013, the perturbational complexity index (PCI) was proposed, a measure of the algorithmic complexity of the electrophysiological response of the cortex to transcranial magnetic stimulation. This measure was shown to be higher in individuals that are awake, in REM sleep or in a locked-in state than in those who are in deep sleep or in a vegetative state,JOURNAL, Adenauer G. Casali, Olivia Gosseries, Mario Rosanova, Mélanie Boly, Simone Sarasso, Karina R. Casali, Silvia Casarotto, Marie-Aurélie Bruno, Steven Laureys, Giulio Tononi, Giulio Tononi, Marcello Massimini, A Theoretically based index of consciousness independent of sensory processing and behavior, Science Translational Medicine, 14 August 2013, 5, 198, 198ra105, 10.1126/scitranslmed.3006294, 23946194,weblink making it potentially useful as a quantitative assessment of consciousness states.Assuming that not only humans but even some non-mammalian species are conscious, a number of evolutionary approaches to the problem of neural correlates of consciousness open up. For example, assuming that birds are conscious—a common assumption among neuroscientists and ethologists due to the extensive cognitive repertoire of birds—there are comparative neuroanatomical ways to validate some of the principal, currently competing, mammalian consciousness–brain theories. The rationale for such a comparative study is that the avian brain deviates structurally from the mammalian brain. So how similar are they? What homologues can be identified? The general conclusion from the study by Butler, et al.,JOURNAL, Ann B. Butler, Paul R. Manger, B.I.B Lindahl, Peter Århem, 2005, Evolution of the neural basis of consciousness: a bird-mammal comparison, BioEssays, 27, 9, 923–936, 10.1002/bies.20280, 16108067, is that some of the major theories for the mammalian brain JOURNAL, Francis Crick and Christof Koch, 1995, Are we aware of neural activity in primary visual cortex?, Nature, 375, 121–123, 10.1038/375121a0, 7753166, 6527, 1995Natur.375..121C, BOOK, Gerald Edelman, Gerald M. Edelman and Giulio Tononi, 2000, A Universe of Consciousness: How Matter Becomes Imagination, Basic Books, 978-0-465-01376-0, JOURNAL, Rodney M.J. Cotterill, Cooperation of the basal ganglia, cerebellum, sensory cerebrum and hippocampus: possible implications for cognition, consciousness, intelligence and creativity, Progress in Neurobiology, 2001, 64, 1, 1–33, 10.1016/s0301-0082(00)00058-7, 11250060, also appear to be valid for the avian brain. The structures assumed to be critical for consciousness in mammalian brains have homologous counterparts in avian brains. Thus the main portions of the theories of Crick and Koch, Edelman and Tononi, and Cotterill seem to be compatible with the assumption that birds are conscious. Edelman also differentiates between what he calls primary consciousness (which is a trait shared by humans and non-human animals) and higher-order consciousness as it appears in humans alone along with human language capacity. Certain aspects of the three theories, however, seem less easy to apply to the hypothesis of avian consciousness. For instance, the suggestion by Crick and Koch that layer 5 neurons of the mammalian brain have a special role, seems difficult to apply to the avian brain, since the avian homologues have a different morphology. Likewise, the theory of EcclesJOURNAL, 1982, J.C. Eccles, Animal consciousness and human self-consciousness, Experientia, 38, 12, 1384–1391, 10.1007/bf01955747, John Eccles (neurophysiologist), JOURNAL, 1990, John Eccles, A unitary hypothesis of mind-brain interaction in the cerebral cortex, Proceedings of the Royal Society of London B, 240, 1299, 433–451, 10.1098/rspb.1990.0047, 1990RSPSB.240..433E, John Eccles (neurophysiologist), seems incompatible, since a structural homologue/analogue to the dendron has not been found in avian brains. The assumption of an avian consciousness also brings the reptilian brain into focus. The reason is the structural continuity between avian and reptilian brains, meaning that the phylogenetic origin of consciousness may be earlier than suggested by many leading neuroscientists.Joaquin Fuster of UCLA has advocated the position of the importance of the prefrontal cortex in humans, along with the areas of Wernicke and Broca, as being of particular importance to the development of human language capacities neuro-anatomically necessary for the emergence of higher-order consciousness in humans.Joaquin Fuster, The Prefrontal Cortex, Second Edition.

Biological function and evolution

Opinions are divided as to where in biological evolution consciousness emerged and about whether or not consciousness has any survival value. Some argue that consciousness is a byproduct of evolution. It has been argued that consciousness emerged (i) exclusively with the first humans, (ii) exclusively with the first mammals, (iii) independently in mammals and birds, or (iv) with the first reptiles.BOOK, Peter Århem, B.I.B. Lindahl, Paul R. Manger, Ann B. Butler, 2008, Hans Liljenström, Peter Århem, On the origin of consciousness—some amniote scenarios, Consciousness Transitions: Phylogenetic, Ontogenetic, and Physiological Aspects, Elsevier.,weblink 978-0-444-52977-0, Other authors date the origins of consciousness to the first animals with nervous systems or early vertebrates in the Cambrian over 500 million years ago.JOURNAL, Feinberg, TE, Mallatt, J, October 2013, The evolutionary and genetic origins of consciousness in the Cambrian Period over 500 million years ago., Frontiers in Psychology, 10.3389/fpsyg.2013.00667, 24109460, 4, 667, 3790330, Donald Griffin suggests in his book Animal Minds a gradual evolution of consciousness. Each of these scenarios raises the question of the possible survival value of consciousness.Thomas Henry Huxley defends in an essay titled On the Hypothesis that Animals are Automata, and its History an epiphenomenalist theory of consciousness according to which consciousness is a causally inert effect of neural activity—“as the steam-whistle which accompanies the work of a locomotive engine is without influence upon its machinery”.JOURNAL, T.H. Huxley, On the hypothesis that animals are automata, and its history, The Fortnightly Review, 16, 253, 555–580, 1874, T.H. Huxley, 1874Natur..10..362., 10.1038/010362a0, To this William James objects in his essay Are We Automata? by stating an evolutionary argument for mind-brain interaction implying that if the preservation and development of consciousness in the biological evolution is a result of natural selection, it is plausible that consciousness has not only been influenced by neural processes, but has had a survival value itself; and it could only have had this if it had been efficacious.JOURNAL, W. James, Are we automata?, Mind, 4, 13, 1–22, 1879, 10.1093/mind/os-4.13.1, William James,weblink JOURNAL, B.I.B. Lindahl, Consciousness and biological evolution, Journal of Theoretical Biology, 187, 4, 613–629, 1997, 10.1006/jtbi.1996.0394, Karl Popper develops in the book The Self and Its Brain a similar evolutionary argument.BOOK, The Self and Its Brain, Karl Popper, Karl R. Popper, John Eccles (neurophysiologist), John C. Eccles, Springer International, 1977, 978-0-387-08307-0, 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.JOURNAL, Bernard Baars, The conscious access hypothesis: Origins and recent evidence, Trends in Cognitive Sciences, 6, 47–52, 11849615, 10.1016/S1364-6613(00)01819-2, 1, January 2002, Bernard Baars, This has been called the integration consensus. Another example has been proposed by Gerald Edelman called dynamic core hypothesis which puts emphasis on reentrant connections that reciprocally link areas of the brain in a massively parallel manner.JOURNAL, Seth, Anil, Eugene Izhikevich, George Reeke, Gerald Edelman, Theories and measures of consciousness: An extended framework, Proceedings of the National Academy of Sciences, 2006, 103, 28, 10.1073/pnas.0604347103, 10799–10804, 16818879, 1487169, 2006PNAS..10310799S, Edelman also stresses the importance of the evolutionary emergence of higher-order consciousness in humans from the historically older trait of primary consciousness which humans share with non-human animals (see Neural correlates section above). These theories of integrative function present solutions to two classic problems associated with consciousness: differentiation and unity. They show how our conscious experience can discriminate between a virtually unlimited number of different possible scenes and details (differentiation) because it integrates those details from our sensory systems, while the integrative nature of consciousness in this view easily explains how our experience can seem unified as one whole despite all of these individual parts. However, it remains unspecified which kinds of information are integrated in a conscious manner and which kinds can be integrated without consciousness. Nor is it explained what specific causal role conscious integration plays, nor why the same functionality cannot be achieved 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 of information can be disseminated and combined with other kinds without consciousness, as in intersensory interactions such as the ventriloquism effect.JOURNAL, Ezequiel Morsella, 2005, The function of phenomenal states: Supramodular Interaction Theory, Psychological Review, 112, 1000–1021, 16262477, 4, 10.1037/0033-295X.112.4.1000, Hence it remains unclear why any of it is conscious. For a review of the differences between conscious and unconscious integrations, see the article of E. Morsella.As noted earlier, even among writers who consider consciousness to be a well-defined thing, there is widespread dispute about which animals other than humans can be said to possess it.BOOK, S. Budiansky, If a Lion Could Talk: Animal Intelligence and the Evolution of Consciousness, 1998, The Free Press, 978-0-684-83710-9,weblink Edelman has described this distinction as that of humans possessing higher-order consciousness while sharing the trait of primary consciousness with non-human animals (see previous paragraph). Thus, any examination of the evolution of consciousness is faced with great difficulties. Nevertheless, some writers have argued that consciousness can be viewed from the standpoint of evolutionary biology as an adaptation in the sense of a trait that increases fitness.JOURNAL, S. Nichols, T. Grantham, Adaptive Complexity and Phenomenal Consciousness, 2000, Philosophy of Science, 67, 4, 648–670, 10.1086/392859,weblink, 2017-10-25,weblink" title="">weblink 2017-08-13, dead, In his article "Evolution of consciousness", John Eccles argued that special anatomical and physical properties of the mammalian cerebral cortex gave rise to consciousness ("[a] psychon ... linked to [a] dendron through quantum physics").JOURNAL, John Eccles, Evolution of consciousness, Proc. Natl. Acad. Sci. USA, 89, 16, 7320–7324, 1992, 1502142, 49701, 10.1073/pnas.89.16.7320, 1992PNAS...89.7320E, John Eccles (neurophysiologist), Bernard Baars proposed that once in place, this "recursive" circuitry may have provided a basis for the subsequent development of many of the functions that consciousness facilitates in higher organisms.BOOK, Bernard Baars, A Cognitive Theory of Consciousness, 1993, Cambridge University Press, 978-0-521-42743-2, Bernard Baars, Peter Carruthers has put forth one such potential adaptive advantage gained by conscious creatures by suggesting that consciousness allows an individual to make distinctions between appearance and reality.BOOK, Carruthers, Peter, Phenomenal Consciousness: A Naturalistic Theory, 2004, Cambridge University Press, Cambridge, This ability would enable a creature to recognize the likelihood that their perceptions are deceiving them (e.g. that water in the distance may be a mirage) and behave accordingly, and it could also facilitate the manipulation of others by recognizing how things appear to them for both cooperative and devious ends.Other philosophers, however, have suggested that consciousness would not be necessary for any functional advantage in evolutionary processes.JOURNAL, Owen Flanagan, T.W. Polger, 1995, Zombies and the function of consciousness, Journal of Consciousness Studies, 2, 313–321, Owen Flanagan, JOURNAL, Rosenthal, David, Consciousness and its function, Neuropsychologia, 2008, 46, 3, 829–840, 10.1016/j.neuropsychologia.2007.11.012, 18164042, No one has given a causal explanation, they argue, of why it would not be possible for a functionally equivalent non-conscious organism (i.e., a philosophical zombie) to achieve the very same survival advantages as a conscious organism. If evolutionary processes are blind to the difference between function F being performed by conscious organism O and non-conscious organism O*, it is unclear what adaptive advantage consciousness could provide.BOOK, Stevan Harnad, 2002, Turing indistinguishability and the Blind Watchmaker, J.H. Fetzer, Consciousness Evolving, John Benjamins,weblink 2011-10-26, Stevan Harnad, As a result, an exaptive explanation of consciousness has gained favor with some theorists that posit consciousness did not evolve as an adaptation but was an exaptation arising as a consequence of other developments such as increases in brain size or cortical rearrangement. Consciousness in this sense has been compared to the blind spot in the retina where it is not an adaption of the retina, but instead just a by-product of the way the retinal axons were wired.JOURNAL, Zack Robinson, Corey J. Maley, Gualtiero Piccinini, 2015, Is Consciousness a Spandrel?., Journal of the American Philosophical Association, 1, 2, 365–383, 10.1017/apa.2014.10, Several scholars including Pinker, Chomsky, Edelman, and Luria have indicated the importance of the emergence of human language as an important regulative mechanism of learning and memory in the context of the development of higher-order consciousness (see Neural correlates section above).

States of consciousness

File:Abbot of Watkungtaphao in Phu Soidao Waterfall.jpg|thumb|right|150px|A Buddhist monk meditating ]]There are some brain states in which consciousness seems to be absent, including dreamless sleep, coma, and death. There are also a variety of circumstances that can change the relationship between the mind and the world in less drastic ways, producing what are known as altered states of consciousness. Some altered states occur naturally; others can be produced by drugs or brain damage.JOURNAL, Dieter Vaitl, Psychobiology of altered states of consciousness, 2005, Psychological Bulletin, 131, 98–127, 10.1037/0033-2909.131.1.98, 15631555, 1, etal, Altered states can be accompanied by changes in thinking, disturbances in the sense of time, feelings of loss of control, changes in emotional expression, alternations in body image and changes in meaning or significance.BOOK, Schacter, Daniel, Gilbert, Daniel, Wegner, Daniel, Psychology 2nd Ed., 2011, Worth Publishers, New York, 190, 978-1-4292-3719-2, The two most widely accepted altered states are sleep and dreaming. Although dream sleep and non-dream sleep appear very similar to an outside observer, each is associated with a distinct pattern of brain activity, metabolic activity, and eye movement; each is also associated with a distinct pattern of experience and cognition. During ordinary non-dream sleep, people who are awakened report only vague and sketchy thoughts, and their experiences do not cohere into a continuous narrative. During dream sleep, in contrast, people who are awakened report rich and detailed experiences in which events form a continuous progression, which may however be interrupted by bizarre or fantastic intrusions.JOURNAL, Anton Coenen, Subconscious Stimulus Recognition and Processing During Sleep,weblink 2010, Psyche, 16-2, Thought processes during the dream state frequently show a high level of irrationality. Both dream and non-dream states are associated with severe disruption of memory: it usually disappears in seconds during the non-dream state, and in minutes after awakening from a dream unless actively refreshed.BOOK, J. Allan Hobson, Edward F. Pace-Schott, Robert Stickgold, Robert Stickgold, Dreaming and the brain: Toward a cognitive neuroscience of conscious states, Sleep and Dreaming: Scientific Advances and Reconsiderations, Edward F. Pace-Schott, Mark Solms, Mark Blagrove, Stevan Harnad, 2003, Cambridge University Press, 978-0-521-00869-3, J. Allan Hobson, Research conducted on the effects of partial epileptic seizures on consciousness found that patients who suffer from partial epileptic seizures experience altered states of consciousness.Johanson, M., Valli, K., Revonsuo, A., & Wedlund, J., 2008. Content analysis of subjective experiences in partial epileptic seizures. Epilepsy & Behavior, 12, pp. 170–182JOURNAL, Johanson M., Valli K., Revonsuo A., 2008, Alterations in the contents of consciousness in partial epileptic seizures, Epilepsy & Behavior, 13, 2, 366–371, 10.1016/j.yebeh.2008.04.014, 18522873, etal, In partial epileptic seizures, consciousness is impaired or lost while some aspects of consciousness, often automated behaviors, remain intact. Studies found that when measuring the qualitative features during partial epileptic seizures, patients exhibited an increase in arousal and became absorbed in the experience of the seizure, followed by difficulty in focusing and shifting attention.A variety of psychoactive drugs, including alcohol, have notable effects on consciousness.BOOK, Diagnostic and statistical manual of mental disorders: DSM-IV,weblink 31 July 1994, American Psychiatric Association, Washington, DC, 978-0-89042-025-6, These range from a simple dulling of awareness produced by sedatives, to increases in the intensity of sensory qualities produced by stimulants, cannabis, empathogens–entactogens such as MDMA ("Ecstasy"), or most notably by the class of drugs known as psychedelics. LSD, mescaline, psilocybin, Dimethyltryptamine, and others in this group can produce major distortions of perception, including hallucinations; some users even describe their drug-induced experiences as mystical or spiritual in quality. The brain mechanisms underlying these effects are not as well understood as those induced by use of alcohol, but there is substantial evidence that alterations in the brain system that uses the chemical neurotransmitter serotonin play an essential role.WEB, Michael Lyvers, The neurochemistry of psychedelic experiences, 2003, ePublications@bond,weblink PDF, There has been some research into physiological changes in yogis and people who practise various techniques of meditation. Some research with brain waves during meditation has reported differences between those corresponding to ordinary relaxation and those corresponding to meditation. It has been disputed, however, whether there is enough evidence to count these as physiologically distinct states of consciousness.BOOK, M. Murphy, S. Donovan, E. Taylor, 1997, The Physical and Psychological Effects of Meditation: A Review of Contemporary Research With a Comprehensive Bibliography, 1931–1996, Institute of Noetic Sciences, The most extensive study of the characteristics of altered states of consciousness was made by psychologist Charles Tart in the 1960s and 1970s. Tart analyzed a state of consciousness as made up of a number of component processes, including exteroception (sensing the external world); interoception (sensing the body); input-processing (seeing meaning); emotions; memory; time sense; sense of identity; evaluation and cognitive processing; motor output; and interaction with the environment.BOOK, Charles Tart, States of Consciousness, Ch. 2: The components of consciousness, 2001,, 978-0-595-15196-7,weblink 2011-10-05, Charles Tart, Each of these, in his view, could be altered in multiple ways by drugs or other manipulations. The components that Tart identified have not, however, been validated by empirical studies. Research in this area has not yet reached firm conclusions, but a recent questionnaire-based study identified eleven significant factors contributing to drug-induced states of consciousness: experience of unity; spiritual experience; blissful state; insightfulness; disembodiment; impaired control and cognition; anxiety; complex imagery; elementary imagery; audio-visual synesthesia; and changed meaning of percepts.JOURNAL, Psychometric evaluation of the altered states of consciousness rating scale (OAV), E. Studerus, A. Gamma, F.X. Vollenweider, PLoS ONE, 2010, 5, 8, 20824211, 2930851, 10.1371/journal.pone.0012412, e12412, 2010PLoSO...512412S,


Phenomenology is a method of inquiry that attempts to examine the structure of consciousness in its own right, putting aside problems regarding the relationship of consciousness to the physical world. This approach was first proposed by the philosopher Edmund Husserl, and later elaborated by other philosophers and scientists.BOOK, Robert Sokolowski, Introduction to Phenomenology, 2000, Cambridge University Press, 211–227, 978-0-521-66792-0, Husserl's original concept gave rise to two distinct lines of inquiry, in philosophy and psychology. In philosophy, phenomenology has largely been devoted to fundamental metaphysical questions, such as the nature of intentionality ("aboutness"). In psychology, phenomenology largely has meant attempting to investigate consciousness using the method of introspection, which means looking into one's own mind and reporting what one observes. This method fell into disrepute in the early twentieth century because of grave doubts about its reliability, but has been rehabilitated to some degree, especially when used in combination with techniques for examining brain activity.BOOK, Trusting the Subject?: The Use of Introspective Evidence in Cognitive Science, Volume 1, Anthony Jack, Andreas Roepstorff, Imprint Academic, 2003, 978-0-907845-56-0, Valid and non-reactive verbalization of thoughts during performance of tasks: towards a solution to the central problems of introspection as a source of scientific evidence, K. Anders Ericsson, 1–18, K. Anders Ericsson, File:Neon colour spreading illusion no caption.png|thumb|150px|right|Neon color spreadingNeon color spreading (File:Square neon spread.png|thumb|Square version of the neon spread illusion)Introspectively, the world of conscious experience seems to have considerable structure. Immanuel Kant asserted that the world as we perceive it is organized according to a set of fundamental "intuitions", which include 'object' (we perceive the world as a set of distinct things); 'shape'; 'quality' (color, warmth, etc.); 'space' (distance, direction, and location); and 'time'.ENCYCLOPEDIA, Kant's view of the mind and consciousness of self, Andrew Brook, Stanford Encyclopedia of Philosophy,weblink Metaphysics Research Lab, Stanford University, 2018, Note: translating Kant's terminology into English is often difficult. Some of these constructs, such as space and time, correspond to the way the world is structured by the laws of physics; for others the correspondence is not as clear. Understanding the physical basis of qualities, such as redness or pain, has been particularly challenging. David Chalmers has called this the hard problem of consciousness. Some philosophers have argued that it is intrinsically unsolvable, because qualities ("qualia") are ineffable; that is, they are "raw feels", incapable of being analyzed into component processes.BOOK, On leaving out what it's like, Joseph Levine, The Nature of Consciousness: Philosophical Debates, N. Block, O. Flanagan, G. Guzeldere, 1998, MIT Press, 978-0-262-52210-6, Joseph Levine (philosopher), Other psychologists and neuroscientists reject these arguments. For example, research on ideasthesia shows that qualia are organised into a semantic-like network. Nevertheless, it is clear that the relationship between a physical entity such as light and a perceptual quality such as color is extraordinarily complex and indirect, as demonstrated by a variety of optical illusions such as neon color spreading.BOOK, The Science of Color, Steven K. Shevell, Color appearance, Steven K. Shevell, 149–190, 2003, Elsevier, 978-0-444-51251-2, In neuroscience, a great deal of effort has gone into investigating how the perceived world of conscious awareness is constructed inside the brain. The process is generally thought to involve two primary mechanisms: (1) hierarchical processing of sensory inputs, and (2) memory. Signals arising from sensory organs are transmitted to the brain and then processed in a series of stages, which extract multiple types of information from the raw input. In the visual system, for example, sensory signals from the eyes are transmitted to the thalamus and then to the primary visual cortex; inside the cerebral cortex they are sent to areas that extract features such as three-dimensional structure, shape, color, and motion.BOOK, Philosophical Foundations of Neuroscience, M.R., Bennett, Peter Michael, Stephan Hacker, 2003, Wiley-Blackwell, 978-1-4051-0838-6, 121–147, Memory comes into play in at least two ways. First, it allows sensory information to be evaluated in the context of previous experience. Second, and even more importantly, working memory allows information to be integrated over time so that it can generate a stable representation of the world—Gerald Edelman expressed this point vividly by titling one of his books about consciousness The Remembered Present.BOOK, Gerald Edelman, The Remembered Present: A Biological Theory of Consciousness,weblink registration, Basic Books, 1989, 978-0-465-06910-1, 109–118, Gerald Edelman, In computational neuroscience, Bayesian approaches to brain function have been used to understand both the evaluation of sensory information in light of previous experience, and the integration of information over time. Bayesian models of the brain are probabilistic inference models, in which the brain takes advantage of prior knowledge to interpret uncertain sensory inputs in order to formulate a conscious percept; Bayesian models have successfully predicted many perceptual phenomena in vision and the nonvisual senses.JOURNAL, Knill DC, 2007, Learning Bayesian priors for depth perception,weblink7/8/13/, Journal of Vision, 7, 8, 1–20, 10.1167/7.8.13, 17685820, 2015-04-02, 2008-11-21, dead, JOURNAL, Battaglia PW, Jacobs RA, Aslin RN, 2003, Bayesian integration of visual and auditory signals for spatial localization, Journal of the Optical Society of America, 20, 7, 1391–1397, 10.1364/josaa.20.001391, 2003JOSAA..20.1391B, JOURNAL, Goldreich, Daniel, Tong, Jonathan, Prediction, Postdiction, and Perceptual Length Contraction: A Bayesian Low-Speed Prior Captures the Cutaneous Rabbit and Related Illusions, Frontiers in Psychology, 10 May 2013, 4, 221, 10.3389/fpsyg.2013.00221, 23675360, 3650428, Despite the large amount of information available, many important aspects of perception remain mysterious. A great deal is known about low-level signal processing in sensory systems. However, how sensory systems, action systems, and language systems interact are poorly understood. At a deeper level, there are still basic conceptual issues that remain unresolved. Many scientists have found it difficult to reconcile the fact that information is distributed across multiple brain areas with the apparent unity of consciousness: this is one aspect of the so-called binding problem.Koch, The Quest for Consciousness, pp. 167–170 There are also some scientists who have expressed grave reservations about the idea that the brain forms representations of the outside world at all: influential members of this group include psychologist J. J. Gibson and roboticist Rodney Brooks, who both argued in favor of "intelligence without representation".JOURNAL, Brooks, Rodney A., Intelligence without representation, Artificial Intelligence, January 1991, 47, 1–3, 139–159, 10.1016/0004-3702(91)90053-M,,

Entropic brain

The entropic brain is a theory of conscious states informed by neuroimaging research with psychedelic drugs. It suggests that the brain in primary states (rapid eye movement (REM) sleep, early psychosis and when using psychedelic drugs) is in a highly disordered state, and that normal waking consciousness constrains some of this freedom and adds associated metacognitive functions, including reality-testing and self-awareness.JOURNAL, Carhart-Harris, R. L., Friston, K. J., Barker, Eric L., REBUS and the Anarchic Brain: Toward a Unified Model of the Brain Action of Psychedelics, Pharmacological Reviews, 20 June 2019, 71, 3, 316–344, 10.1124/pr.118.017160, 31221820, JOURNAL, Carhart-Harris, Robin L., The entropic brain – revisited, Neuropharmacology, November 2018, 142, 167–178, 10.1016/j.neuropharm.2018.03.010, 29548884, JOURNAL, Carhart-Harris, Robin L., Leech, Robert, Hellyer, Peter J., Shanahan, Murray, Feilding, Amanda, Tagliazucchi, Enzo, Chialvo, Dante R., Nutt, David, The entropic brain: a theory of conscious states informed by neuroimaging research with psychedelic drugs, Frontiers in Human Neuroscience, 2014, 8, 10.3389/fnhum.2014.00020, 3909994, WEB,weblink Entropy as More than Chaos in the Brain: Expanding Field, Expanding Minds, 2018-06-22, Criticism has included questioning whether the theory has been adequately tested.JOURNAL, Papo, David, Commentary: The entropic brain: a theory of conscious states informed by neuroimaging research with psychedelic drugs, Frontiers in Human Neuroscience, 30 August 2016, 10, 10.3389/fnhum.2016.00423, 5004455,

Medical aspects

The medical approach to consciousness is practically oriented. It derives from a need to treat people whose brain function has been impaired as a result of disease, brain damage, toxins, or drugs. In medicine, conceptual distinctions are considered useful to the degree that they can help to guide treatments. Whereas the philosophical approach to consciousness focuses on its fundamental nature and its contents, the medical approach focuses on the amount of consciousness a person has: in medicine, consciousness is assessed as a "level" ranging from coma and brain death at the low end, to full alertness and purposeful responsiveness at the high end.BOOK, The Neurology of Consciousness: Cognitive Neuroscience and Neuropathology, Steven Laureys, Giulio Tononi, The neurological examination of consciousness, Hal Blumenfeld, 2009, Academic Press, 978-0-12-374168-4, Consciousness is of concern to patients and physicians, especially neurologists and anesthesiologists. Patients may suffer from disorders of consciousness, or may need to be anesthetized for a surgical procedure. Physicians may perform consciousness-related interventions such as instructing the patient to sleep, administering general anesthesia, or inducing medical coma. Also, bioethicists may be concerned with the ethical implications of consciousness in medical cases of patients such as the Karen Ann Quinlan case,JOURNAL, Kinney HC, Korein J, Panigrahy A, Dikkes P, Goode R, 26 May 1994, 21, N Engl J Med, 1469–1475, 8164698, Neuropathological findings in the brain of Karen Ann Quinlan – the role of the thalamus in the persistent vegetative state, 330, 10.1056/NEJM199405263302101, while neuroscientists may study patients with impaired consciousness in hopes of gaining information about how the brain works.Koch, The Quest for Consciousness, pp. 216–226


In medicine, consciousness is examined using a set of procedures known as neuropsychological assessment.JOURNAL, J.T. Giacino, C.M. Smart, 2007, 10.1097/WCO.0b013e3282f189ef, Current Opinion in Neurology, 614–619, 17992078, Recent advances in behavioral assessment of individuals with disorders of consciousness, 20, 6, There are two commonly used methods for assessing the level of consciousness of a patient: a simple procedure that requires minimal training, and a more complex procedure that requires substantial expertise. The simple procedure begins by asking whether the patient is able to move and react to physical stimuli. If so, the next question is whether the patient can respond in a meaningful way to questions and commands. If so, the patient is asked for name, current location, and current day and time. A patient who can answer all of these questions is said to be "alert and oriented times four" (sometimes denoted "A&Ox4" on a medical chart), and is usually considered fully conscious.BOOK, Essentials of Abnormal Psychology,weblink registration, V. Mark Durand, David H. Barlow, Cengage Learning, 2009, 978-0-495-59982-1, 74–75, Note: A patient who can additionally describe the current situation may be referred to as "oriented times four".The more complex procedure is known as a neurological examination, and is usually carried out by a neurologist in a hospital setting. A formal neurological examination runs through a precisely delineated series of tests, beginning with tests for basic sensorimotor reflexes, and culminating with tests for sophisticated use of language. The outcome may be summarized using the Glasgow Coma Scale, which yields a number in the range 3–15, with a score of 3 to 8 indicating coma, and 15 indicating full consciousness. The Glasgow Coma Scale has three subscales, measuring the best motor response (ranging from "no motor response" to "obeys commands"), the best eye response (ranging from "no eye opening" to "eyes opening spontaneously") and the best verbal response (ranging from "no verbal response" to "fully oriented"). There is also a simpler pediatric version of the scale, for children too young to be able to use language.In 2013, an experimental procedure was developed to measure degrees of consciousness, the procedure involving stimulating the brain with a magnetic pulse, measuring resulting waves of electrical activity, and developing a consciousness score based on the complexity of the brain activity.WEB,weblink New tool peeks into brain to measure consciousness, Neergaard, Lauren, August 14, 2013, Associated Press through NBC News,weblink August 16, 2013, dead,

Disorders of consciousness

Medical conditions that inhibit consciousness are considered disorders of consciousness. This category generally includes minimally conscious state and persistent vegetative state, but sometimes also includes the less severe locked-in syndrome and more severe chronic coma.JOURNAL, Bernat JL, 8 Apr 2006, 10.1016/S0140-6736(06)68508-5, 9517, Lancet, 1181–1192, 16616561, Chronic disorders of consciousness, 367, JOURNAL, Bernat JL, 20 Jul 2010, 10.1212/WNL.0b013e3181e8e960, 3, Neurology, 206–207, 20554939, The natural history of chronic disorders of consciousness, 75, Differential diagnosis of these disorders is an active area of biomedical research.JOURNAL, Coleman MR, Davis MH, Rodd JM, Robson T, Ali A, Owen AM, Pickard JD, September 2009, 10.1093/brain/awp183, 9, Brain, 2541–2552, 19710182, Towards the routine use of brain imaging to aid the clinical diagnosis of disorders of consciousness, 132, JOURNAL, Monti MM, Vanhaudenhuyse A, Coleman MR, Boly M, Pickard JD, Tshibanda L, Owen AM, Laureys S, 18 Feb 2010, 10.1056/NEJMoa0905370, 7, N Engl J Med, 579–589, 20130250, Willful modulation of brain activity in disorders of consciousness, 362, JOURNAL, Seel RT, Sherer M, Whyte J, Katz DI, Giacino JT, Rosenbaum AM, Hammond FM, Kalmar K, Pape TL, December 2010, 10.1016/j.apmr.2010.07.218, 12, Arch Phys Med Rehabil, 1795–1813, 21112421, Assessment scales for disorders of consciousness: evidence-based recommendations for clinical practice and research, 91, etal, Finally, brain death results in an irreversible disruption of consciousness. While other conditions may cause a moderate deterioration (e.g., dementia and delirium) or transient interruption (e.g., grand mal and petit mal seizures) of consciousness, they are not included in this category.{| class="wikitable" style="width:100%"! Disorder !! Description
| The patient has awareness, sleep-wake cycles, and meaningful behavior (viz., eye-movement), but is isolated due to quadriplegia and pseudobulbar palsy.
| The patient has intermittent periods of awareness and wakefulness and displays some meaningful behavior.
| The patient has sleep-wake cycles, but lacks awareness and only displays reflexive and non-purposeful behavior.
| The patient lacks awareness and sleep-wake cycles and only displays reflexive behavior.
| The patient lacks awareness, sleep-wake cycles, and brain-mediated reflexive behavior.


One of the most striking disorders of consciousness goes by the name anosognosia, a Greek-derived term meaning 'unawareness of disease'. This is a condition in which patients are disabled in some way, most commonly as a result of a stroke, but either misunderstand the nature of the problem or deny that there is anything wrong with them.BOOK, George Prigatano, Daniel Schacter, Awareness of Deficit After Brain Injury: Clinical and Theoretical Issues, Oxford University Press, 1991, Introduction, George P. Prigatano, Daniel Schacter, 3–16, 978-0-19-505941-0, Daniel Schacter, The most frequently occurring form is seen in people who have experienced a stroke damaging the parietal lobe in the right hemisphere of the brain, giving rise to a syndrome known as hemispatial neglect, characterized by an inability to direct action or attention toward objects located to the left with respect to their bodies. Patients with hemispatial neglect are often paralyzed on the right side of the body, but sometimes deny being unable to move. When questioned about the obvious problem, the patient may avoid giving a direct answer, or may give an explanation that doesn't make sense. Patients with hemispatial neglect may also fail to recognize paralyzed parts of their bodies: one frequently mentioned case is of a man who repeatedly tried to throw his own paralyzed right leg out of the bed he was lying in, and when asked what he was doing, complained that somebody had put a dead leg into the bed with him. An even more striking type of anosognosia is Anton–Babinski syndrome, a rarely occurring condition in which patients become blind but claim to be able to see normally, and persist in this claim in spite of all evidence to the contrary.BOOK, George Prigatano, Daniel Schacter, Awareness of Deficit After Brain Injury: Clinical and Theoretical Issues, Oxford University Press, 1991, Anosognosia: possible neuropsychological mechanisms, Kenneth M. Heilman, 53–62, 978-0-19-505941-0,

Stream of consciousness

William James is usually credited with popularizing the idea that human consciousness flows like a stream, in his Principles of Psychology of 1890. According to James, the "stream of thought" is governed by five characteristics: "(1) Every thought tends to be part of a personal consciousness. (2) Within each personal consciousness thought is always changing. (3) Within each personal consciousness thought is sensibly continuous. (4) It always appears to deal with objects independent of itself. (5) It is interested in some parts of these objects to the exclusion of others".BOOK, William James, The Principles of Psychology, Volume 1, 1890, H. Holt, 225, William James, A similar concept appears in Buddhist philosophy, expressed by the Sanskrit term Citta-saṃtāna, which is usually translated as mindstream or "mental continuum". Buddhist teachings describe that consciousness manifests moment to moment as sense impressions and mental phenomena that are continuously changing.JOURNAL, Karunamuni N.D., The Five-Aggregate Model of the Mind, Sage Open, 5, 2, 215824401558386, May 2015, 10.1177/2158244015583860, The teachings list six triggers that can result in the generation of different mental events. These triggers are input from the five senses (seeing, hearing, smelling, tasting or touch sensations), or a thought (relating to the past, present or the future) that happen to arise in the mind. The mental events generated as a result of these triggers are: feelings, perceptions and intentions/behaviour. The moment-by-moment manifestation of the mind-stream is said to happen in every person all the time. It even happens in a scientist who analyses various phenomena in the world, or analyses the material body including the organ brain. The manifestation of the mindstream is also described as being influenced by physical laws, biological laws, psychological laws, volitional laws, and universal laws. The purpose of the Buddhist practice of mindfulness is to understand the inherent nature of the consciousness and its characteristics.BOOK, Losing the Clouds, Gaining the Sky: Buddhism and the Natural Mind, Taming the mindstream, Dzogchen Rinpoche, Doris Wolter, 2007, Wisdom Publications, 978-0-86171-359-2, 81–92,

Narrative form

In the west, the primary impact of the idea has been on literature rather than science: stream of consciousness as a narrative mode means writing in a way that attempts to portray the moment-to-moment thoughts and experiences of a character. This technique perhaps had its beginnings in the monologues of Shakespeare's plays, and reached its fullest development in the novels of James Joyce and Virginia Woolf, although it has also been used by many other noted writers.BOOK, Robert Humphrey, Stream of Consciousness in the Modern Novel, 1954, University of California Press, 978-0-520-00585-3, 23–49, Here for example is a passage from Joyce's Ulysses about the thoughts of Molly Bloom:}}

Spiritual approaches

{{Further|Level of consciousness (esotericism)|Higher consciousness}}To most philosophers, the word "consciousness" connotes the relationship between the mind and the world. To writers on spiritual or religious topics, it frequently connotes the relationship between the mind and God, or the relationship between the mind and deeper truths that are thought to be more fundamental than the physical world. The mystical psychiatrist Richard Maurice Bucke distinguished between three types of consciousness: 'Simple Consciousness', awareness of the body, possessed by many animals; 'Self Consciousness', awareness of being aware, possessed only by humans; and 'Cosmic Consciousness', awareness of the life and order of the universe, possessed only by humans who are enlightened.BOOK, Richard Maurice Bucke, Cosmic Consciousness: A Study in the Evolution of the Human Mind, Innes & Sons, 1905,weblink 1–2, Richard Maurice Bucke, Many more examples could be given, such as the various levels of spiritual consciousness presented by Prem Saran Satsangi and Stuart Hameroff.Satsangi, Prem Saran and Hameroff, Stuart (2016) Consciousness: Integrating Eastern and Western Perspectives New Age Books. {{ISBN|978-81-7822-493-0}} The most thorough account of the spiritual approach may be Ken Wilber's book The Spectrum of Consciousness, a comparison of western and eastern ways of thinking about the mind. Wilber described consciousness as a spectrum with ordinary awareness at one end, and more profound types of awareness at higher levels.BOOK, Ken Wilber, The Spectrum of Consciousness, Motilal Banarsidass, 2002, 978-81-208-1848-4, 3–16, Ken Wilber,

See also

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Further reading

External links

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