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.
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. Experimental 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 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.
Verbal report is widely considered to be the most reliable indicator of consciousness, but it raises a number of issues. 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: Although verbal report is in practice the "gold standard" for ascribing consciousness, it is not the only possible criterion.
The last three of these can be used as indicators of consciousness when verbal behavior is absent. 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.
Another approach applies specifically to the study of self-awareness , that is, the ability to distinguish oneself from others. In the s 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. A 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.
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 s, 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.
A number of studies have shown that activity in primary sensory areas of the brain is not sufficient to produce consciousness: There is substantial evidence that a "top-down" flow of neural activity i. Modulation 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: In , Graziano and Kastner  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 the , 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,  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. 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. 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.
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.
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. 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.
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. These theories of integrative function present solutions to two classic problems associated with consciousness: 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.
For a review of the differences between conscious and unconscious integrations, see the article of E. 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. 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. Other philosophers, however, have suggested that consciousness would not be necessary for any functional advantage in evolutionary processes.
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.
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.
Both dream and non-dream states are associated with severe disruption of memory: 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. 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. 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. 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.
The most extensive study of the characteristics of altered states of consciousness was made by psychologist Charles Tart in the s and s. 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.
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: 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. 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.
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.
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. 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.
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: 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.
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.
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.
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. Gibson and roboticist Rodney Brooks , who both argued in favor of "intelligence without representation".
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: 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.
In medicine, consciousness is examined using a set of procedures known as neuropsychological assessment. 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. 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 , 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. Medical conditions that inhibit consciousness are considered disorders of consciousness.
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.
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: 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.
William James is usually credited with popularizing the idea that human consciousness flows like a stream, in his Principles of Psychology of According to James, the "stream of thought" is governed by five characteristics: Buddhist teachings describe that consciousness manifests moment to moment as sense impressions and mental phenomena that are continuously changing. The mental events generated as a result of these triggers are: 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. In the west, the primary impact of the idea has been on literature rather than science: 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.
Here for example is a passage from Joyce's Ulysses about the thoughts of Molly Bloom:. Consciousness may have a determinative role in quantum mechanics. Since consciousness is the primary aspect of an observer, and observation is sometimes viewed as a primary reason for apparent wave function collapse ,  consciousness may account for aspects of the measurement problem exemplified by the Schrödinger's cat paradox. This area has been an area of lively debate for decades,  with recent efforts to substitute randomly caused decoherence as the source of apparent wave function collapse.
Max Tegmark and John Archibald Wheeler provided a useful survey  of some of the issues. 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.
Krishna consciousness , for example, is a term used to mean an intimate linkage between the mind of a worshipper and the god Krishna. Wilber described consciousness as a spectrum with ordinary awareness at one end, and more profound types of awareness at higher levels. From Wikipedia, the free encyclopedia. This article is about cognition.
For other uses, see Consciousness disambiguation and Conscious disambiguation. Problem of other minds. Schema of the neural processes underlying consciousness, from Christof Koch. Stream of consciousness psychology. Level of consciousness esotericism and Higher consciousness. Consciousness portal Medicine portal Mind and Brain portal Philosophy portal. Retrieved June 4, Stanford Encyclopedia of Philosophy.
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Beyond Cognition to Consciousness. Uses authors parameter link Note: In many stories the Golem was mindless, but some gave it emotions or thoughts. Verbal Behavior as the Hallmark of Intelligence. In Search of a Fundamental Theory.
Stanford Encyclopedia of Philosophy Spring Edition. The Phenomenal Judgment Approach". Journal of Mind and Behavior. Catching ourselves in the act: Massachusetts Institute of Technology. Respectable, useful, and probably necessary. Information processing and cognition: Aware lays the emphasis on sense perceptions insofar as they are the object of conscious recognition: He was aware of the odor of tobacco.
Cognizant lays the emphasis on an outer recognition more on the level of reason and knowledge than on the sensory level alone: He was cognizant of their drawbacks. Related Words for conscious sensible , watchful , sure , mindful , certain , informed , aware , keen , cognizant , responsive , vigilant , attentive , premeditated , deliberate , calculated , responsible , rational , reflective , self-conscious , acquainted.
Contemporary Examples of conscious To his credit, Huckabee is conscious of the fact that he will need a cluster of deep-pocketed patrons and bundlers. Lloyd Green January 4, Historical Examples of conscious And yet all the while we have been conscious that we were not part of it.
Ballads of a Bohemian Robert W. The Conquest of Fear Basil King. K Mary Roberts Rinehart. Having an awareness of one's environment and one's own existence, sensations, and thoughts.
Intentionally conceived or done; deliberate. In psychoanalysis, the component of waking awareness perceptible by a person at any given instant. Published by Houghton Mifflin Company.
Conscious, aware, cognizant refer to an individual sense of recognition of something within or without oneself. Conscious implies to be awake or awakened to an inner realization of a fact, a truth, a condition, etc.: to be conscious of an extreme weariness. Conscious definition is - having mental faculties not dulled by sleep, faintness, or stupor: awake. How to use conscious in a sentence. Synonym Discussion of conscious. having mental faculties not dulled by sleep, faintness, or stupor: awake See the full definition. SINCE conscious. Conscious is an adjective that simply means alert and awake. If you fall from a tree and smack your head on the side of the wheelbarrow, there's a good chance you won't be conscious taradsod.tkue reading.