Consciousness

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Representation of consciousness from the 17th century.

Consciousness is a term that has been used to refer to a variety of aspects of the relationship between the mind and the world with which it interacts.[1] It has been defined, at one time or another, as: subjective experience; awareness; the ability to experience feelings; wakefulness; having a sense of selfhood; or as the executive control system of the mind.[2] Despite the difficulty of definition, many philosophers believe that there is a basic underlying intuition about consciousness that is shared by nearly all people.[3] As Max Velmans and Susan Schneider wrote in The Blackwell Companion to Consciousness:

"Anything that we are aware of at a given moment forms part of our consciousness, making conscious experience at once the most familiar and most mysterious aspect of our lives."[4]

In philosophy, consciousness is often said to imply four characteristics: subjectivity, change, continuity, and selectivity.[2][5] Philosopher Franz Brentano has also suggested intentionality or aboutness (that consciousness is about something); however, there is no consensus on whether intentionality is a requirement for consciousness.[6] Issues of practical concern in the philosophy of consciousness include whether consciousness can ever be explained mechanistically; whether non-human consciousness exists and if so how it can be recognized; at what point in fetal development consciousness begins; and whether it may ever be possible for computers to achieve a conscious state.[7][8][9]

At one time consciousness was viewed with skepticism by many scientists and considered within the domain of philosophers and theologians, but in recent years it has been an increasingly significant topic of scientific research. In psychology and neuroscience, the focus of most research 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 use human subjects and assess consciousness 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 psychoactive 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, then delirium, then loss of any meaningful communication, and ending with loss of movement in response to painful stimuli.[10] 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.[11]

Etymology of the word and history of the concept

The origin of the modern concept of consciousness is often attributed to John Locke's Essay Concerning Human Understanding, published in 1690.[12] Locke explicitly defined consciousness as “the perception of what passes in a man’s own mind.”[13] His essay had much influence on the 18th century view of consciousness, and his definition appeared in Samuel Johnson's celebrated Dictionary (1755).

The earliest English language uses of "conscious" and "consciousness" date back, however, to the 1500s. The English word "conscious" originally derived from Latin word conscius (con- "together" + scire "to know"), but the Latin version did not have the same meaning as our word — it meant knowing with, in other words having joint or common knowledge with another, privy to, cognizant of.[14] 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. Taken literally this is nonsense, but it 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 retained the Latin meaning. 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." The Latin conscius sibi 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".[15]

A related word was 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.[16] Here, conscientia is the knowledge that a witness has of the deed of someone else.[17] 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.[citation needed] Descartes used "conscientia" the way modern speakers would use "conscience." In Search after Truth he says "conscience or internal testimony" (conscientia vel interno testimonio).[18]

Shortly thereafter, in Britain, the neo-Platonist theologian Ralph Cudworth used something resembling the modern meaning of consciousness in his "True Intellectual System of the Universe" (1678), although he never explicitly defined the term.[19]

Philosophical approaches

The philosophy of mind has given rise to many stances regarding consciousness. They differ in the answers they give to a set of fundamental questions, including:

  1. Is consciousness a valid concept or a conceptual error?
  2. Is it a single unified entity or a collection of distinct entities?
  3. How does it relate to language?
  4. Can it be explained in terms of the laws of physics?
  5. Why are we convinced that other people (or even we ourselves) possess consciousness?
  6. Why do we believe that some animals possess consciousness, and is there any way to test this belief?
  7. What is the nature of experience, and particularly what is the nature of sensory qualities such as the color red?

The question about the relationship between consciousness and the physical realm is perhaps the most contentious of all: several schools of thought are defined mainly in terms of the answers they give to it.

Is it a valid concept?

A majority of philosophers have felt that the word consciousness names a genuine entity, but some who belong to the physicalist and behaviorist schools have not been convinced; many scientists have also been dubious. The most compelling argument in favor is that the vast majority of mankind has an overwhelming intuition that there truly is such a thing. The argument against is that this intuition, however compelling it may be, is false. Gilbert Ryle, for example, argued that traditional understanding of consciousness depends on a Cartesian dualist outlook that divides into mind and body, 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.[citation needed]

Another problem that concerns many philosophers and scientists is the difficulty of producing a definition that does not rely on circularity or fuzziness. The neuroscientist Antonio Damasio, for example, calls consciousness "the feeling of what happens", and defines it as "an organism's awareness of its own self and its surroundings".[20] These formulations seem intuitively reasonable, but they are difficult to apply to specific situations.

Is it a single thing?

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 is an umbrella term meaning different things to different people.

Ned Block proposed a distinction between two types of consciousness that he called phenomenal (P-consciousness) and access (A-consciousness).[21] 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,[22] 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. Dennett denies that the concept of qualia is coherent, that P-consciousness is intrinsically different from A-consciousness, and that there is anything especially hard about the "hard problem".

How does it relate to the physical world?

Main article: Mind–body problem

The first influential philosopher to discuss this question specifically was Descartes, and the answer he proposed 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).[23] He suggested that the interaction between these two domains occurs inside the brain, perhaps in a small midline structure called the pineal gland.[24]

Although it is widely accepted that Descartes explained the problem very cogently, few later philosophers have been happy with his solution, and in particular his emphasis on the pineal gland has generally been ridiculed. Alternative solutions, however, have been extremely diverse. They can be divided broadly into two categories: dualist solutions that maintain Descartes's 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 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 camps.

Some theorists hold that phenomenal consciousness in particular creates an explanatory gap. Colin McGinn takes the New Mysterianism position that it can't be solved, and David Chalmers criticizes purely physical accounts of mental experiences based on the idea that philosophical zombies are logically possible and supports property dualism.

How does it relate to language?

In humans, the clearest visible indication of consciousness is the ability to use language. Medical assessments of consciousness rely heavily on an ability to respond to questions and commands, and in scientific studies of consciousness, the usual criterion for awareness is verbal report (that is, subjects are deemed to be aware if they say that they are). Thus there is a strong connection between consciousness and language. Philosophers differ, however, on whether language is essential to consciousness or merely the most powerful tool for gaining access to it.

Descartes believed that language is essential: he argued that non-human animals lack consciousness because they lack language. Others have reached the same conclusion, though sometimes for different reasons. Julian Jaynes argued in The Origin of Consciousness in the Breakdown of the Bicameral Mind that for consciousness to arise, language needs to have reached a fairly high level of complexity. Merlin Donald also argued for a critical dependence of consciousness on the ability to use symbols in a sophisticated way.[25]

Those are, however, minority views. If language is essential, then speechless humans (infants, feral children, aphasics, etc.) could not be said to be conscious, a conclusion that the majority of philosophers have resisted. The implication that humans are the only animals capable of consciousness is also widely resisted, and often viewed as offensive.[26]

Why do we believe that other people are conscious?

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? This is the problem of other minds. 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.

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. Some philosophers, such as Daniel Dennett in an essay titled The Unimaginable Preposterousness of Zombies, argue that people who give this explanation do not really understand what they are saying. 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 they tell us about their experiences.

Spiritual approaches

Vedanta

According to Vedanta, awareness is not a product of physical processes and can be considered under four aspects. The first is waking consciousness (jagaritasthana), the identification with “I” or “me” in relationship with phenomenal experiences with external objects. The second aspect is dream consciousness (svapna-sthana), which embodies the same subject/object duality as the waking state. The third aspect of consciousness is deep sleep (susupti), which is non-dual as a result of holding in abeyance all feelings, thoughts, and sensations. The final aspect is the consciousness that underlies and transcends the first three aspects (turiya) also referred to as a trans-cognitive state (anubhava) or a state of self-realization or freedom from body-mind identification (moksha).[27] Gaudiya Vedanta recognizes a fifth aspect of consciousness in which God becomes subordinate to bhakti.[28]

Vijñāna

In Buddhism, consciousness (viññāṇa) is included in the five classically defined experiential "aggregates". The aggregates are seen as empty of self-nature; that is, they arise dependent on causes and conditions. The cause for consciousness arising (viññāṇa) is the arising of another aggregate (physical or mental); and, consciousness arising in turn gives rise to one or more of the mental (nāma) aggregates. The causation chain identified in the aggregate (khandha) model overlaps the conditioning chain in Dependent Origination (paticcasamuppāda) model. [29] Consciousness is the third link, between mind body mental formations and name & form in the traditional Twelve Causes (nidāna) of Dependent Origination.[30] The six classes of consciousness are: eye-consciousness, ear-consciousness, nose-consciousness, tongue-consciousness, body-consciousness, intellect-consciousness. [31] The following aspects are traditionally highlighted within Dependent Origination:

  • consciousness is conditioned by mental fabrications (saṅkhāra);
  • consciousness and the mind-body (nāmarūpa) are interdependent; and,
  • consciousness acts as a "life force" by which there is a continuity across rebirths.

Scientific approaches

Broadly speaking, scientific approaches to consciousness can be divided into two categories. In one category are methods that rely on asking subjects to describe their experiences or answer questions, and therefore can only be conducted using human subjects. In the other category are methods that test for aspects of consciousness that can be manifested in nonverbal behavior, and therefore can be used in other species as well as humans. The nonverbal manifestations that have been used include arousal, responsiveness to stimulation, attention, and the ability to distinguish self from non-self.

Cognitive psychology and cognitive neuroscience

For a long time in scientific psychology, consciousness as a research topic or explanatory concept was strongly discouraged by mainstream scholars, because of concerns about the validation of primary data .[32] Research on topics associated with consciousness were conducted under the banner of attention. Modern investigations into consciousness are based on psychological statistical studies and case studies of consciousness states and the deficits caused by surgery, trauma or illness that disrupt the normal functioning of human senses and cognition. Another approach is experimental work on unconscious perception, e.g., the investigation of priming effects using subliminal stimuli. These discoveries suggest that the mind is a complex structure derived from various localized functions that are bound together with a unitary awareness.[citation needed]

Several studies point to common mechanisms in different clinical conditions that lead to loss of consciousness. Persistent vegetative state (PVS) is a condition in which an individual loses the higher cerebral powers of the brain, but maintains sleep-wake cycles with full or partial autonomic functions. Studies comparing PVS with healthy, awake subjects consistently demonstrate an impaired connectivity between the deeper (brainstem and thalamic) and the upper (cortical) areas of the brain. In addition, it is agreed that the general brain activity in the cortex is lower in the PVS state. Some electroneurobiological interpretations of consciousness characterize this loss of consciousness as a loss of the ability to resolve time (similar to playing an old phonographic record at very slow or very rapid speed), along a continuum that starts with inattention, continues on sleep, and arrives to coma and death .[33] It is likely that different components of consciousness can be teased apart with anesthetics, sedatives and hypnotics. These drugs appear to act differently on several brain areas to disrupt, to varying degrees, different components of consciousness. The ability to recall information, for example, may be disrupted by anesthetics acting on the hippocampal cortex. Neurons in this region are particularly sensitive to anesthetics at the time loss of recall occurs. Direct anesthetic actions on hippocampal neurons have been shown to underlie EEG effects that occur in humans and animals during loss of recall.[34]

Brain chemistry affects human consciousness. Sleeping drugs such as midazolam (Dormicum) can bring the brain from the awake condition (conscious) to the sleep (unconscious) condition. Wake-up drugs such as flumazenil reverse this process. Many other drugs (such as alcohol, nicotine, Tetrahydrocannabinol (THC), heroin, cocaine, LSD, MDMA, caffeine), have a consciousness-changing effect.[citation needed]

Neurophysiological studies in awake, behaving monkeys point to advanced cortical areas in prefrontal cortex and temporal lobes as carriers of neuronal correlates of consciousness. Christof Koch and Francis Crick argue that neuronal mechanisms of consciousness are intricately related to prefrontal cortex — cortical areas involved in higher cognitive function, affect, behavioral control, and planning. Rodolfo Llinas proposes 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 time coincidence. According to this view the "I" represents a global predictive function required for intentionality.[35][36] Experimental work of Steven Wise, Mikhail Lebedev and their colleagues supports this view. They demonstrated that activity of prefrontal cortex neurons reflects illusory perceptions of movements of visual stimuli. Nikos Logothetis and colleagues made similar observations on visually responsive neurons in the temporal lobe. These neurons reflect the visual perception in the situation when conflicting visual images are presented to different eyes (i.e., bistable percepts during binocular rivalry). The studies of blindsight — vision without awareness after lesions to parts of the visual system such as the primary visual cortex — performed by Lawrence Weiskrantz and David P. Carey provided important insights on how conscious perception arises in the brain. [citation needed]

The Neuroscience of free will also seems to provide relevant insights to the understanding of consciousness.

Measurement aspects

Experimental research on consciousness presents special difficulties, e.g., when establishing whether an observer is unaware of a critical stimulus. Several techniques exist for dissociating the conscious visibility of stimuli from indirect effects they might have on behavior.[37] For example, the experimental technique of Response Priming allows researchers to find conditions where the conscious visibility of a critical stimulus and the ability of that stimulus to affect a motor response develop in opposite directions, e.g., when motor effects of a stimulus become larger under conditions where its visibility is decreasing.[38]

Experimental philosophy

A new approach has attempted to combine the methodologies of cognitive psychology and traditional philosophy to understand consciousness. This research has taken place in the new field called experimental philosophy, which seeks to use empirical methods (like conducting experiments to test how ordinary non-experts think) to inform the philosophical discussion.[39] The aim of this type of philosophical research on consciousness has been to try to get a better grasp on how exactly people ordinarily understand consciousness. For instance, work by Joshua Knobe and Jesse Prinz suggests that people may have two different ways of understanding minds generally.[40] Another suggestion has been that there is actually no such phenomenon as consciousness, based on a criticized study by Justin Sytsma and Edouard Machery.[41] Further, Justin Sytsma and Edouard Machery have written about the proper methodology for studying folk intuitions about consciousness.[42]

Evolutionary psychology

Consciousness can be viewed from the standpoints of evolutionary psychology or evolutionary biology approach as an adaptation because it is a trait that increases fitness.[43] Consciousness also adheres to John Alcock's theory of animal behavioral adaptations because it possesses both proximate and ultimate causes.[44]

In his paper "Evolution of consciousness," John Eccles argues that special anatomical and physical properties of the mammalian cerebral cortex gave rise to consciousness.[45] Budiansky, by contrast, limits consciousness to humans, proposing that human consciousness may have evolved as an adaptation to anticipate and counter social strategems of other humans, predators, and prey.[46] Alternatively, it has been argued that the recursive circuitry underwriting consciousness is much more primitive, having evolved initially in premammalian species because it improves the capacity for interaction with both social and natural environments by providing an energy-saving "neutral" gear in an otherwise energy-expensive motor output machine.[47] Another theory, proposed by Shaun Nichols and Todd Grantham, proposes that it is unnecessary to trace the exact evolutionary or causal role of phenomenal consciousness because the complexity of phenomenal consciousness alone implies that it is an adaptation.[48] Once in place, this recursive circuitry may well have provided a basis for the subsequent development of many of the functions that consciousness facilitates in higher organisms, as outlined by Bernard J. Baars.[49]

Functions of Consciousness

Functions of Consciousness
Function Purpose
Definition and context-setting Relating global input to its contexts, thereby defining input and removing ambiguities
Adaptation and learning Representing and adapting to novel and significant events
Editing, flagging, and debugging Monitoring conscious content, editing it, and trying to change it if it is consciously "flagged" as an error
Recruiting and control function Recruiting subgoals and motor systems to organize and carry out mental and physical actions
Prioritizing and access control Control over what will become conscious
Decision-making or executive function Recruiting unconscious knowledge sources to make proper decisions, and making goals conscious to allow widespread recruitment of conscious and unconscious "votes" for or against them
Analogy-forming function Searching for a partial match between contents of unconscious systems and a globally displayed (conscious) message
Metacognitive or self-forming function Reflection upon and control of our own conscious and unconscious functioning
Auto-programming and self-maintenance function Maintenance of maximum stability in the face of changing inner and outer conditions

Physical

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 even 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).[50]

The most influential modern physical theories of consciousness are based on psychology and neuroscience. Theories proposed by neuroscientists such as Gerald Edelman[51] and António Damásio,[52] and by philosophers such as Daniel Dennett,[53] seek to explain access consciousness and phenomenal consciousness in terms of neural events occurring within the brain. Many other neuroscientists, such as Christof Koch,[54] 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.

Some theorists—most of whom are physicists—have argued that classical physics is intrinsically incapable of explaining the holistic aspects of consciousness, but that quantum theory provides the missing ingredients. The most notable theories falling into this category include the Holonomic brain theory of Karl H. 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 has been confirmed by experiment, and many scientists and philosophers consider the arguments for an important role of quantum phenomena to be unconvincing.[citation needed]

Medical aspects

In medicine, consciousness is measured by neuropsychological assessment.[55] It is of concern to patients, physicians, and ethicists as well as biological scientists and biomedical engineers. Patients may suffer from disorders of consciousness and seek medical treatment. Physicians may perform medical interventions of consciousness such as instructing the patient to sleep, administering general anesthesia, or inducing medical coma. Bioethicists and neuroethicists may be concerned with the ethical implications of consciousness in medical cases of patients such as Karen Ann Quinlan[56] and Terri Schiavo[57]. Furthermore, biological scientists study patients with these disorders while biomedical engineers develop neuroprosthetics for them.

Disorders of consciousness

Medical conditions that inhibit consciousness are considered disorders of consciousness.[58] 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.[58][59] Differential diagnosis of these disorders is an active area of biomedical research.[60][61][62] Finally, brain death results in an irreversible disruption of consciousness.[58] While other conditions may cause a moderate deterioration (e.g., dementia and delirium) or transient disruption (e.g., grand mal and petit mal seizures) of consciousness, they are not included in this category.

Disorder Description
Locked-in syndrome The patient has awareness, sleep-wake cycles, and meaningful behavior (viz., eye-movement), but is isolated due to quadriplegia and pseudobulbar palsy.
Minimally conscious state The patient has intermittent periods of awareness and wakefulness and displays some meaningful behavior.
Persistent vegetative state The patient has sleep-wake cycles, but lacks awareness and only displays reflexive and non-purposeful behavior.
Chronic coma The patient lacks awareness and sleep-wake cycles and only displays reflexive behavior.
Brain death The patient lacks awareness, sleep-wake cycles, and behavior.

Functions

Regarding the primary function of conscious processing, a recurring idea in recent theories is that phenomenal states somehow integrate neural activities and information-processing that would otherwise be independent (see review in Baars, 2002). This has been called the integration consensus. However, it remained unspecified which kinds of information are integrated in a conscious manner and which kinds can be integrated without consciousness. Obviously not all kinds of information are capable of being disseminated consciously (e.g., neural activity related to vegetative functions, reflexes, unconscious motor programs, low-level perceptual analyses, etc.) and many kinds can be disseminated and combined with other kinds without consciousness, as in intersensory interactions such as the ventriloquism effect (cf., Morsella, 2005).

Ervin László argues that self-awareness, the ability to make observations of oneself, evolved. Émile Durkheim formulated the concept of so called collective consciousness, which is essential for organization of human, social relations. The accelerating drive of human race to explorations, cognition, understanding and technological progress can be explained by some features of collective consciousness (collective self - concepts) and collective intelligence[citation needed]

Tests

As there is no clear definition of consciousness and no empirical measure exists to test for its presence, it has been argued that due to the nature of the problem of consciousness, empirical tests are intrinsically impossible. However, several tests have been developed that attempt an operational definition of consciousness and try to determine whether computers and non-human animals can demonstrate through behavior, by passing these tests, that they are conscious.

In medicine, several neurological and brain imaging techniques, such as EEG and fMRI, have proven useful for physical measures of brain activity associated with consciousness. This is particularly true for EEG measures during anesthesia, which can provide an indication of anesthetic depth.

The Turing test

See also: Turing test and philosophy of artificial intelligence

Though sometimes thought of as a test for consciousness, the Turing test (named after computer scientist Alan Turing, who proposed it) was originally presented as an operational replacement for the question "Can machines think?", which Turing regarded as too ambiguous to be meaningful. This test is commonly cited in discussion of artificial intelligence. The test is based on an "Imitation Game" in which a human experimenter converses, via computer keyboards, with two competitors, one human, the other a computer. Because all of the conversation is by keyboard, no cues such as voice, prosody, or appearance will be available to indicate which is human and which is the computer. If the human judge is unable to determine which of the conversants is the computer, the computer is said to have "passed" the test.

The Turing test has generated 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,[63] while David Chalmers, argues that a philosophical zombie could pass the test, yet fail to be conscious.[64]

It has been argued that the question itself is excessively anthropomorphic. Edsger Dijkstra commented that "The question of whether a computer can think is no more interesting than the question of whether a submarine can swim", expressing the view that different words are appropriate for the workings of a machine to those of animals even if they produce similar results, just as submarines are not normally said to swim.

Philosopher John Searle developed a thought experiment, the Chinese room argument, which is intended to show problems with the Turing Test.[65] Searle asks the reader to imagine a non-Chinese speaker in a room in which there are stored a very large number of Chinese symbols and rule books. Questions are passed to the person in the form of written Chinese symbols via a slot, and the person responds by looking up the symbols and the correct replies in the rule books. Based on the purely input-output operations, the "Chinese room" gives the appearance of understanding Chinese. However, the person in the room understands no Chinese at all. This argument has been the subject of intense philosophical debate since it was introduced in 1980, even leading to edited volumes on this topic alone.

The application of the Turing test to human consciousness has even led to an annual competition, the Loebner Prize[citation needed], with "Grand Prize of $100,000 and a Gold Medal for the first computer whose responses were indistinguishable from a human's."

Mirror

Main article: Mirror test

See also the concept of the Mirror stage by Jacques Lacan

With the mirror test, devised by Gordon Gallup in the 1970s, one is interested in whether animals are able to recognize themselves in a mirror. The classic example of the test involves placing a spot of coloring on the skin or fur near the individual's forehead and seeing if they attempt to remove it or at least touch the spot, thus indicating that they recognize that the individual they are seeing in the mirror is themselves. Humans (older than 18 months) and other great apes, bottlenose dolphins, pigeons, elephants[66] and magpies[67] have all been observed to pass this test. The test is usually carried out with an identical 'spot' being placed elsewhere on the head with a non-visible material as a control, to assure the subject is not responding to the touch stimuli of the spot's presence.

Delay

One problem researchers face is distinguishing nonconscious reflexes and instinctual responses from conscious responses. Neuroscientists Francis Crick and Christof Koch have proposed that by placing a delay between stimulus and execution of action, one may determine the extent of involvement of consciousness in an action of a biological organism.[citation needed]

For example, when psychologists Larry Squire and Robert Clark combined a tone of a specific pitch with a puff of air to the eye, test subjects came to blink their eyes in anticipation of the puff of air when the appropriate tone was played. When the puff of air followed a half of a second later, no such conditioning occurred. When subjects were asked about the experiment, only those who were asked to pay attention could consciously distinguish which tone preceded the puff of air.[citation needed]

Ability to delay the response to an action implies that the information must be stored in short-term memory, which is conjectured to be a closely associated prerequisite for consciousness. However, this test is only valid for biological organisms. While it is simple to create a computer program that passes, such success does not suggest anything beyond a clever programmer.[26][page needed]

Merkwelt

The merkwelt (German; English: "way of viewing the world", "peculiar individual consciousness") is a concept in robotics, psychology and biology that describes a creature or android's capacity to view things, manipulate information and synthesize to make meaning out of the universe.[citation needed]

In biology, a shark's merkwelt for instance is dominated by smell due to its enlarged olfactory lobes whilst a bat's is dominated by its hearing, especially at ultrasonic frequencies. In literature, a character's merkwelt can be defined by their particular consciousness. For the collective, the plural is merkwelten. It is related to the original German meaning of zeitgeist and indeed a merkwelt can be thought of as a more general, individual zeitgeist.[68][69][70]

To have a merkwelt, the individual must be self-aware. This "self-awareness" may involve thoughts, sensations, perceptions, moods, emotions, and dreams. This term was particularly developed by the German biologist Jakob von Uexküll who framed it as part of his theory of umwelt. This basically stated that any living 'observer' of the broader environment or umwelt through their particular werkwelt or 'mechanical viewing' (that is to say, the organs through which they view the world- their eyes, ears, mouth etc. in humans and electrical sensors in sharks for instance) could have a merkwelt or 'perceptual universe'. In essence, his theory posits that the way each human or certain type of aware animal perceives of their environment both through their experiences, the particular way their organs perceive their environment and the way in which their consciousness processes this information (how their brain works).[clarification needed][71]

See also

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Notes

  1. ^ van Gulick, 2004
  2. ^ a b Farthing, 1992
  3. ^ Searle, 2005, In Honderich, 2005
  4. ^ Schneider and Velmans, 2007, pp.1-6 In Velmans & Schneider, 2007; For a similar comment see also Güzeldere, 1995 In Block, Flanagan & Güzeldere, 1997, pp.1-67
  5. ^ James, W. 1910 In Block, Flanagan & Güzeldere
  6. ^ cf. Searle, 2005 In Honderich, 2005, s.v. consciousness
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  8. ^ Stuart Shieber (ed): The Turing test : verbal behavior as the hallmark of intelligence, Cambridge, Mass, MIT Press, 2004, ISBN 978-0-262-69293-9
  9. ^ Steven Marcus: Neuroethics: mapping the field. Dana Press, New York 2002. ISBN 978-0-9723830-0-4.
  10. ^ Güzeldere, 1995 In Block, Flanagan & Güzeldere, 1997, pp.1-67
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  12. ^ Locke, John. "An Essay Concerning Human Understanding (Chapter XXVII)". Australia: University of Adelaide. Retrieved August 20, 2010.
  13. ^ "Science & Technology: consciousness". Encyclopedia Britannica. Retrieved August 20, 2010.
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  16. ^ Hastings, John A.; Selbie (2003). Encyclopedia of Religion and Ethics Part 7. Kessinger Publishing. p. 41. ISBN 0766136779. {{cite book}}: More than one of |first1= and |first= specified (help) note: "In the sense of 'consciousness,' consientia is rare, but it is exceedingly common in most writers after Cicero with the meaning 'conscience'."
  17. ^ Melenaar, G. Mnemosyne, Fourth Series. Vol. 22. Brill. pp. 170–180. note: reference only that Cicero had been using the word.[1]
  18. ^ Heinämaa, Sara (2007). Consciousness: from perception to reflection in the history of philosophy. Springer. pp. 205–206. ISBN 978-1-4020-6081-6.
  19. ^ Gaukroger, Stephen (1991). The Uses of antiquity: the scientific revolution and the classical tradition. D. Reidel Publishing Company. p. 79. ISBN 0-7923-1130-2.
  20. ^ Damasio. A. 1999. The Feeling of What Happens: Body and Emotion in the Making of Consciousness. New York: Harcourt Brace. p. 4.
  21. ^ Block, N. (2004). The Encyclopedia of Cognitive Science.
  22. ^ Dennett, D. (2004). Consciousness Explained, p. 375. Harmondsworth: The Penguin Press, Middlesex, England. ISBN 0971399037-6.
  23. ^ Dy, Jr., Manuel B. (2001isbn=971-12-0245-X). Philosophy of Man: selected readings. Goodwill Trading Co.Inc. p. 97. {{cite book}}: Check date values in: |year= (help)
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  25. ^ A Mind So Rare p.202
  26. ^ a b Christof Koch, The Quest for Consciousness: A Neurobiological Approach. Englewood, Colorado: Roberts and Company Publishers.
  27. ^ Yegan Pillay, Katherine K. Ziff and Christine Suniti Bhat, Vedānta Personality Development: A Model to Enhance the Cultural Competence of Psychotherapists, International Journal of Hindu Studies, Volume 12, Number 1 / April, 2008, OUP
  28. ^ Tripurari, Swami, Entering the Fifth Dimension, Sanga, 1999.
  29. ^ This overlap is particularly pronounced in the Mahanidana Sutta (DN 15) where consciousness (viññāṇa) is a condition of name-and-body (nāmarūpa) and vice-versa (see, e.g., Thanissaro, 1997a).
  30. ^ Not all canonical texts identify twelve causes in Dependent Origination's causal chain. For instance, the Mahanidana Sutta (DN 15) (Thanissaro, 1997a) identifies only nine causes (omitting the six sense bases, formations and ignorance) and the initial text of the Nalakalapiyo Sutta (SN 12.67) (Thanissaro, 2000) twice identifies ten causes (omitting formations and ignorance) although its final enumeration includes the twelve traditional factors.
  31. ^ For instance, similar to the sensory-specific description of consciousness found in discussing "the All" (above), the "Analysis of Dependent Origination Discourse" (Paticcasamuppada-vibhanga Sutta, SN 12.2) describes viññāṇa ("consciousness") in the following manner:
    "And what is consciousness? These six are classes of consciousness: eye-consciousness, ear-consciousness, nose-consciousness, tongue-consciousness, body-consciousness, intellect-consciousness. This is called consciousness." (Thanissaro, 1997b)
  32. ^ Hendriks-Jansen, Horst (1996). Catching ourselves in the act: situated activity, interactive emergence, evolution, and human thought. Massachusetts Institute of Technology. p. 114. ISBN 0-262-08246-2.
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References

  • Block, N., Flanagan, O., & Güzeldere, G. (1997). The Nature of Consciousness: Philosophical debates Cambridge, MA: MIT.
  • Carruthers, P. (2007). In Stanford Encyclopedia of Philosophy. (version Sep 11, 2007) http://plato.stanford.edu/entries/consciousness-higher/
  • Farthing, G. W. (1992). The Psychology of Consciousness. Upper Saddle River, NJ: Prentice Hall.
  • van Gulick, R. (2004). Consciousness. In Stanford Encyclopedia of Philosophy. (version Aug 16, 2004) http://plato.stanford.edu/entries/consciousness/
  • Nagel, T. (1974). What it is like to be a bat. Philosophical Review 83. October, 435-450.
  • Searle (2005). Consciousness. In Honderich, T. (Ed.) (2005). The Oxford Companion to Philosophy (2nd ed.). Oxford.
  • Velmans, M., & Schneider, S. (Eds.) (2007). The Blackwell Companion to Consciousness. Malden, MA: Blackwell.
  • McKenna, T., McKenna, D. (1975). "The Invisible Landscape - Mind, Hallucinogens, and I Ching". Seabury Press.

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