Cognitive neuroscience

From Wikipedia, the free encyclopedia

Cognitive neuroscience is an academic field concerned with the scientific study of biological substrates underlying cognition,^[1] with a specific focus on the neural substrates of mental processes. It addresses the questions of how psychological/cognitive functions are produced by neural circuits in the brain. Cognitive neuroscience is a branch of both psychology and neuroscience, overlapping with disciplines such as physiological psychology, cognitive psychology, and neuropsychology.^[2] Cognitive neuroscience relies upon theories in cognitive science coupled with evidence from neuropsychology, and computational modeling.^[2]

Due to its multidisciplinary nature, cognitive neuroscientists may have various backgrounds. Other than the associated disciplines just mentioned, cognitive neuroscientists may have backgrounds in neurobiology, bioengineering, psychiatry, neurology, physics, computer science, linguistics, philosophy, and mathematics.

Methods employed in cognitive neuroscience include experimental paradigms from psychophysics and cognitive psychology, functional neuroimaging, electrophysiology, cognitive genomics, and behavioral genetics. Studies of patients with cognitive deficits due to brain lesions constitute an important aspect of cognitive neuroscience. Theoretical approaches include computational neuroscience and cognitive psychology.

Cognitive neuroscience can look at the effects of damage to the brain and subsequent changes in the thought processes due to changes in neural circuitry resulting from the ensued damage. Also, cognitive abilities based on brain development is studied and examined under the subfield of developmental cognitive neuroscience.

Historical origins

Timeline showing major developments in science that led to the emergence of the field cognitive neuroscience.

Cognitive neuroscience is an interdisciplinary area of study that has emerged from many other fields, perhaps most significantly neuroscience, psychology, and computer science.^[3] There were several stages in these disciplines that changed the way researchers approached their investigations and that led to the field becoming fully established.

Although the task of cognitive neuroscience is to describe how the brain creates the mind, historically it has progressed by investigating how a certain area of the brain supports a given mental faculty. However, early efforts to subdivide the brain proved to be problematic. The phrenologist movement failed to supply a scientific basis for its theories and has since been rejected. The aggregate field view, meaning that all areas of the brain participated in all behavior,^[4] was also rejected as a result of brain mapping, which began with Hitzig and Fritsch’s experiments ^[5] and eventually developed through methods such as positron emission tomography (PET) and functional magnetic resonance imaging (fMRI).^[6] Gestalt theory, neuropsychology, and the cognitive revolution were major turning points in the creation of cognitive neuroscience as a field, bringing together ideas and techniques that enabled researchers to make more links between behavior and its neural substrates.

Origins in philosophy

Philosophers have always been interested in the mind. For example, Aristotle thought the brain was the body’s cooling system and the capacity for intelligence was located in the heart. It has been suggested that the first person to believe otherwise was the Roman physician Galen in the second century AD, who declared that the brain was the source of mental activity ^[7] although this has also been accredited to Alcmaeon.^[8] Psychology, a major contributing field to cognitive neuroscience, emerged from philosophical reasoning about the mind.^[9]

19th century

Phrenology

A page from the American Phrenological Journal

Main article: Phrenology

One of the predecessors to cognitive neuroscience was phrenology, a pseudoscientific approach that claimed that behavior could be determined by the shape of the scalp. In the early 19th century, Franz Joseph Gall and J. G. Spurzheim believed that the human brain was localized into approximately 35 different sections. In his book, The Anatomy and Physiology of the Nervous System in General, and of the Brain in Particular, Gall claimed that a larger bump in one of these areas meant that that area of the brain was used more frequently by that person. This theory gained significant public attention, leading to the publication of phrenology journals and the creation of phrenometers, which measured the bumps on a human subject's head. While phrenology remained a fixture at fairs and carnivals, it did not enjoy wide acceptance within the scientific community.^[10] The major criticism of phrenology is that researchers were not able to test theories empirically.^[3]

Localizationist view

The localizationist view was concerned with mental abilities being localized to specific areas of the brain rather than on what the characteristics of the abilities were and how to measure them.^[3] Studies performed in Europe, such as those of John Hughlings Jackson, supported this view. Jackson studied patients with brain damage, particularly those with epilepsy. He discovered that the epileptic patients often made the same clonic and tonic movements of muscle during their seizures, leading Jackson to believe that they must be occurring in the same place every time. Jackson proposed that specific functions were localized to specific areas of the brain,^[11] which was critical to future understanding of the brain lobes.

Aggregate field view

According to the aggregate field view, all areas of the brain participate in every mental function.^[4]
Pierre Flourens, a French experimental psychologist, challenged the localizationist view by using animal experiments.^[3] He discovered that removing the cerebellum in rabbits and pigeons affected their sense of muscular coordination, and that all cognitive functions were disrupted in pigeons when the cerebral hemispheres were removed. From this he concluded that the cerebral cortex, cerebellum, and brainstem functioned together as a whole.^[12] His approach has been criticised on the basis that the tests were not sensitive enough to notice selective deficits had they been present.^[3]

Emergence of neuropsychology

Perhaps the first serious attempts to localize mental functions to specific locations in the brain was by Broca and Wernicke. This was mostly achieved by studying the effects of injuries to different parts of the brain on psychological functions.^[13] In 1861, French neurologist Paul Broca came across a man who was able to understand language but unable to speak. The man could only produce the sound "tan". It was later discovered that the man had damage to an area of his left frontal lobe now known as Broca's area. Carl Wernicke, a German neurologist, found a patient who could speak fluently but non-sensibly. The patient had been the victim of a stroke, and could not understand spoken or written language. This patient had a lesion in the area where the left parietal and temporal lobes meet, now known as Wernicke's area. These cases, which suggested that lesions caused specific behavioral changes, strongly supported the localizationist view.

Mapping the brain

In 1870, German physicians Eduard Hitzig and Gustav Fritsch published their findings about the behavior of animals. Hitzig and Fritsch ran an electric current through the cerebral cortex of a dog, causing different muscles to contract depending on which areas of the brain were electrically stimulated. This led to the proposition that individual functions are localized to specific areas of the brain rather than the cerebrum as a whole, as the aggregate field view suggests.^[5] Brodmann was also an important figure in brain mapping; his experiments based on Franz Nissl’s tissue staining techniques divided the brain into fifty-two areas.

20th century

Cognitive revolution

At the start of the 20th century, attitudes in America were characterised by pragmatism, which led to a preference for behaviorism as the primary approach in psychology. J.B. Watson was a key figure with his stimulus-response approach. By conducting experiments on animals he was aiming to be able to predict and control behaviour. Behaviourism eventually failed because it could not provide realistic psychology of human action and thought – it was too based in physical concepts to explain phenomena like memory and thought. This led to what is often termed as the "cognitive revolution".^[14]

Neuron doctrine

In the early 20th century, Santiago Ramón y Cajal and Camillo Golgi began working on the structure of the neuron. Golgi developed a silver staining method that could entirely stain several cells in a particular area, leading him to believe that neurons were directly connected with each other in one cytoplasm. Cajal challenged this view after staining areas of the brain that had less myelin and discovering that neurons were discrete cells. Cajal also discovered that cells transmit electrical signals down the neuron in one direction only. Both Golgi and Cajal were awarded a Nobel Prize in Physiology or Medicine in 1906 for this work on the neuron doctrine.^[15]

Mid-late 20th century

Several findings in the 20th century continued to advance the field, such as the discovery of ocular dominance columns, recording of single nerve cells in animals, and coordination of eye and head movements. Experimental psychology was also significant in the foundation of cognitive neuroscience. Some particularly important results were the demonstration that some tasks are accomplished via discrete processing stages, the study of attention, and the notion that behavioural data do not provide enough information by themselves to explain mental processes. As a result, some experimental psychologists began to investigate neural bases of behaviour. Wilder Penfield built up maps of primary sensory and motor areas of the brain by stimulating cortices of patients during surgery. Sperry and Gazzaniga’s work on split brain patients in the 1950s was also instrumental in the progress of the field.^[7]

Brain mapping

New brain mapping technology, particularly fMRI and PET, allowed researchers to investigate experimental strategies of cognitive psychology by observing brain function. Although this is often thought of as a new method (most of the technology is relatively recent), the underlying principle goes back as far as 1878 when blood flow was first associated with brain function.^[6] Angelo Mosso, an Italian psychologist of the 19th century, had monitored the pulsations of the adult brain through neurosurgically created bony defects in the skulls of patients. He noted that when the subjects engaged in tasks such as mathematical calculations the pulsations of the brain increased locally. Such observations led Mosso to conclude that blood flow of the brain followed function.^[6]

Emergence of a new discipline

Birth of cognitive science

On September 11, 1956, a large-scale meeting of cognitivists took place at the Massachusetts Institute of Technology. George A. Miller presented his "The Magical Number Seven, Plus or Minus Two" paper while Noam Chomsky and Newell & Simon presented their findings on computer science. Ulric Neisser commented on many of the findings at this meeting in his 1967 book Cognitive Psychology. The term "psychology" had been waning in the 1950s and 1960s, causing the field to be referred to as "cognitive science". Behaviorists such as Miller began to focus on the representation of language rather than general behavior. David Marr concluded that one should understand any cognitive process at three levels of analysis. These levels include computational, algorithmic/representational, and physical levels of analysis.^[16]

Combining neuroscience and cognitive science

Before the 1980s, interaction between neuroscience and cognitive science was scarce.^[17] The term 'cognitive neuroscience' was coined by George Miller and Michael Gazzaniga toward the end of the 1970s.^[17] Cognitive neuroscience began to integrate the newly laid theoretical ground in cognitive science, that emerged between the 1950s and 1960s, with approaches in experimental psychology, neuropsychology and neuroscience. (Neuroscience was not established as a unified discipline until 1971^[18]). In the very late 20th century new technologies evolved that are now the mainstay of the methodology of cognitive neuroscience, including TMS (1985) and fMRI (1991). Earlier methods used in cognitive neuroscience includes EEG (human EEG 1920) and MEG (1968). Occasionally cognitive neuroscientists utilize other brain imaging methods such as PET and SPECT. An upcoming technique in neuroscience is NIRS which uses light absorption to calculate changes in oxy- and deoxyhemoglobin in cortical areas. In some animals Single-unit recording can be used. Other methods include microneurography, facial EMG, and eye-tracking. Integrative neuroscience attempts to consolidate data in databases, and form unified descriptive models from various fields and scales: biology, psychology, anatomy, and clinical practice.^[19] Brenda Milner, Marcus Raichle and John O'Keefe received the Kavli Prize in Neuroscience “for the discovery of specialized brain networks for memory and cognition" in 2014^[20] and O'Keefe shared the Nobel Prize in Physiology or Medicine in the same year with May-Britt Moser and Edvard Moser "for their discoveries of cells that constitute a positioning system in the brain".^[21]

Recent trends

Recently the foci of research have expanded from the localization of brain area(s) for specific functions in the adult brain using a single technology, studies have been diverging in several different directions ^[22] such as monitoring REM sleep via polygraphy, a machine that is capable of recording the electrical activity of a sleeping brain. Advances in non-invasive functional neuroimaging and associated data analysis methods have also made it possible to use highly naturalistic stimuli and tasks such as feature films depicting social interactions in cognitive neuroscience studies.^[23]

Linguistics

From Wikipedia, the free encyclopedia

Linguistics is the scientific^[1] study of language.^[2] There are three aspects to this study: language form, language meaning, and language in context.^[3] The earliest activities in the description of language have been attributed to Pāṇini, who was an early student of linguistics^[4](fl. 4th century BCE),^[5] with his analysis of Sanskrit in Ashtadhyayi.^[6]

Linguistics analyzes human language as a system for relating sounds (or signs in signed languages) and meaning.^[7] Phonetics studies acoustic and articulatory properties of the production and perception of speech sounds and non-speech sounds. The study of language meaning, on the other hand, deals with how languages encode relations between entities, properties, and other aspects of the world to convey, process, and assign meaning, as well as to manage and resolve ambiguity. While the study of semantics typically concerns itself with truth conditions, pragmatics deals with how context influences meanings.^[8]

Grammar is a system of rules which govern the form of the utterances in a given language. It encompasses both sound^[9] and meaning, and includes phonology (how sounds and gestures function together), morphology (the formation and composition of words), and syntax (the formation and composition of phrases and sentences from words).^[10]

In the early 20th century, Ferdinand de Saussure distinguished between the notions of langue and parole in his formulation of structural linguistics. According to him, parole is the specific utterance of speech, whereas langue refers to an abstract phenomenon that theoretically defines the principles and system of rules that govern a language.^[11] This distinction resembles the one made by Noam Chomsky between competence and performance, where competence is individual's ideal knowledge of a language, while performance is the specific way in which it is used.^[12]

The formal study of language has also led to the growth of fields like psycholinguistics, which explores the representation and function of language in the mind; neurolinguistics, which studies language processing in the brain; and language acquisition, which investigates how children and adults acquire a particular language.

Linguistics also includes nonformal approaches to the study of other aspects of human language, such as social, cultural, historical and political factors.^[13] The study of cultural discourses and dialects is the domain of sociolinguistics, which looks at the relation between linguistic variation and social structures, as well as that of discourse analysis, which examines the structure of texts and conversations.^[14] Research on language through historical and evolutionary linguistics focuses on how languages change, and on the origin and growth of languages, particularly over an extended period of time.

Corpus linguistics takes naturally occurring texts or films (in signed languages) as its primary object of analysis, and studies the variation of grammatical and other features based on such corpora. Stylistics involves the study of patterns of style: within written, signed, or spoken discourse.^[15] Language documentation combines anthropological inquiry with linguistic inquiry to describe languages and their grammars. Lexicography covers the study and construction of dictionaries. Computational linguistics applies computer technology to address questions in theoretical linguistics, as well as to create applications for use in parsing, data retrieval, machine translation, and other areas. People can apply actual knowledge of a language in translation and interpreting, as well as in language education - the teaching of a second or foreign language. Policy makers work with governments to implement new plans in education and teaching which are based on linguistic research.

Areas of study related to linguistics include semiotics (the study of signs and symbols both within language and without), literary criticism, translation, and speech-language pathology.

Nomenclature

Before the 20th century, the term philology, first attested in 1716,^[16] was commonly used to refer to the science of language, which was then predominantly historical in focus.^[17][18] Since Ferdinand de Saussure's insistence on the importance of synchronic analysis, however, this focus has shifted^[19] and the term "philology" is now generally used for the "study of a language's grammar, history, and literary tradition", especially in the United States^[20] (where philology has never been very popularly considered as the "science of language").^[21]

Although the term "linguist" in the sense of "a student of language" dates from 1641,^[22] the term "linguistics" is first attested in 1847.^[22] It is now the common academic term in English for the scientific study of language.

Today, the term linguist applies to someone who studies language or is a researcher within the field, or to someone who uses the tools of the discipline to describe and analyze specific languages.^[23]

Variation and Universality

While some theories on linguistics focus on the different varieties that language produces, among different sections of society, others focus on the universal properties that are common to all human languages. The theory of variation therefore would elaborate on the different usages of popular languages like French and English across the globe, as well as its smaller dialects and regional permutations within their national boundaries. The theory of variation looks at the cultural stages that a particular language undergoes, and these include the following.

Lexicon

The lexicon is a catalogue of words and terms that are stored in a speaker's mind. The lexicon consists of words and bound morphemes, which are words that can't stand alone, like affixes. In some analyses, compound words and certain classes of idiomatic expressions and other collocations are also considered to be part of the lexicon. Dictionaries represent attempts at listing, in alphabetical order, the lexicon of a given language; usually, however, bound morphemes are not included.  Lexicography, closely linked with the domain of semantics, is the science of mapping the words into an encyclopedia or a dictionary. The creation and addition of new words (into the lexicon) are called neologisms.

It is often believed that a speaker's capacity for language lies in the quantity of words stored in the lexicon. However, this is often considered a myth by linguists. The capacity for the use of language is considered by many linguists to lie primarily in the domain of grammar, and to be linked with competence, rather than with the growth of vocabulary. Even a very small lexicon is theoretically capable of producing an infinite number of sentences.

Discourse

A discourse is a way of speaking that emerges within a certain social setting and is based on a certain subject matter. A particular discourse becomes a language variety when it is used in this way for a particular purpose, and is referred to as a register.^[24] There may be certain lexical additions (new words) that are brought into play because of the expertise of the community of people within a certain domain of specialisation. Registers and discourses therefore differentiate themselves through the use of vocabulary, and at times through the use of style too. People in the medical fraternity, for example, may use some medical terminology in their communication that is specialised to the field of medicine. This is often referred to as being part of the "medical discourse", and so on.

Dialect

A dialect is a variety of language that is characteristic of a particular group among the language speakers.^[25] The group of people who are the speakers of a dialect are usually bound to each other by social identity. This is what differentiates a dialect from a register or a discourse, where in the latter case, cultural identity does not always play a role. Dialects are speech varieties that have their own grammatical and phonological rules, linguistic features, and stylistic aspects, but have not been given an official status as a language. Dialects often move on to gain the status of a language due to political and social reasons. Differentiation amongst dialects (and subsequently, languages too) is based upon the use of grammatical rules, syntactic rules, and stylistic features, though not always on lexical use or vocabulary. The popular saying that a "language is a dialect with an army and navy" is attributed as a definition formulated by Max Weinreich.

Universal grammar takes into account general formal structures and features that are common to all dialects and languages, and the template of which pre-exists in the mind of an infant child. This idea is based on the theory of generative grammar and the formal school of linguistics, whose proponents include Noam Chomsky and those who follow his theory and work.

"We may as individuals be rather fond of our own dialect. This should not make us think, though, that it is actually any better than any other dialect. Dialects are not good or bad, nice or nasty, right or wrong – they are just different from one another, and it is the mark of a civilised society that it tolerates different dialects just as it tolerates different races, religions and sexes." ^[26]

Structures

Linguistic structures are pairings of meaning and form. Any particular pairing of meaning and form is a Saussurean sign. For instance, the meaning "cat" is represented worldwide with a wide variety of different sound patterns (in oral languages), movements of the hands and face (in sign languages), and written symbols (in written languages).

Linguists focusing on structure attempt to understand the rules regarding language use that native speakers know (not always consciously). All linguistic structures can be broken down into component parts that are combined according to (sub)conscious rules, over multiple levels of analysis. For instance, consider the structure of the word "tenth" on two different levels of analysis. On the level of internal word structure (known as morphology), the word "tenth" is made up of one linguistic form indicating a number and another form indicating ordinality. The rule governing the combination of these forms ensures that the ordinality marker "th" follows the number "ten." On the level of sound structure (known as phonology), structural analysis shows that the "n" sound in "tenth" is made differently from the "n" sound in "ten" spoken alone. Although most speakers of English are consciously aware of the rules governing internal structure of the word pieces of "tenth", they are less often aware of the rule governing its sound structure. Linguists focused on structure find and analyze rules such as these, which govern how native speakers use language.

Linguistics has many sub-fields concerned with particular aspects of linguistic structure. The theory that elucidates on these, as propounded by Noam Chomsky, is known as generative theory or universal grammar. These sub-fields range from those focused primarily on form to those focused primarily on meaning. They also run the gamut of level of analysis of language, from individual sounds, to words, to phrases, up to cultural discourse.

Sub-fields that focus on a structure-focused study of language:

• Phonetics, the study of the physical properties of speech sound production and perception
• Phonology, the study of sounds as abstract elements in the speaker's mind that distinguish meaning (phonemes)
• Morphology, the study of morphemes, or the internal structures of words and how they can be modified
• Syntax, the study of how words combine to form grammatical phrases and sentences
• Semantics, the study of the meaning of words (lexical semantics) and fixed word combinations (phraseology), and how these combine to form the meanings of sentences
• Pragmatics, the study of how utterances are used in communicative acts, and the role played by context and non-linguistic knowledge in the transmission of meaning
• Discourse analysis, the analysis of language use in texts (spoken, written, or signed)
• Stylistics, the study of linguistic factors (rhetoric, diction, stress) that place a discourse in context
• Semiotics, the study of signs and sign processes (semiosis), indication, designation, likeness, analogy, metaphor, symbolism, signification, and communication.

Relativity

As constructed popularly through the "Sapir-Whorf Hypothesis", relativists believe that the structure of a particular language is capable of influencing the cognitive patterns through which a person shapes his or her world view. Universalists believe that there are commonalities between human perception as there is in the human capacity for language, while relativists believe that this varies from language to language and person to person. While the Sapir-Whorf hypothesis is an elaboration of this idea expressed through the writings of American linguists Edward Sapir and Benjamin Lee Whorf, it was Sapir's student Harry Hoijer who termed it thus. The 20th century German linguist Leo Weisgerber also wrote extensively about the theory of relativity. Relativists argue for the case of differentiation at the level of cognition and in semantic domains. The emergence of cognitive linguistics in the 1980s also revived an interest in linguistic relativity. Thinkers like George Lakoff have argued that language reflects different cultural metaphors, while the French philosopher of language Jacques Derrida's writings have been seen to be closely associated with the relativist movement in linguistics, especially through deconstruction^[27] and was even heavily criticised in the media at the time of his death for his theory of relativism.^[28]

Style

Stylistics is the study and interpretation of texts for aspects of their linguistic and tonal style. Stylistic analysis entails the analysis of description of particular dialects and registers used by speech communities. Stylistic features include rhetoric,^[29] diction, stress, satire, irony, dialogue, and other forms of phonetic variations. Stylistic analysis can also include the study of language in canonical works of literature, popular fiction, news, advertisements, and other forms of communication in popular culture as well. It is usually seen as a variation in communication that changes from speaker to speaker and community to community. In short, Stylistics is the interpretation of text.

Approach

Generative vs. functional theories of language

One major debate in linguistics concerns how language should be defined and understood. Some linguists use the term "language" primarily to refer to a hypothesized, innate module in the human brain that allows people to undertake linguistic behavior, which is part of the formalist approach. This "universal grammar" is considered to guide children when they learn languages and to constrain what sentences are considered grammatical in any language. Proponents of this view, which is predominant in those schools of linguistics that are based on the generative theory of Noam Chomsky, do not necessarily consider that language evolved for communication in particular. They consider instead that it has more to do with the process of structuring human thought (see also formal grammar).

Another group of linguists, by contrast, use the term "language" to refer to a communication system that developed to support cooperative activity and extend cooperative networks. Such theories of grammar, called "functional", view language as a tool that emerged and is adapted to the communicative needs of its users, and the role of cultural evolutionary processes are often emphasized over that of biological evolution.^[30]

Methodology

Linguistics is primarily descriptive. Linguists describe and explain features of language without making subjective judgments on whether a particular feature or usage is "good" or "bad". This is analogous to practice in other sciences: a zoologist studies the animal kingdom without making subjective judgments on whether a particular species is "better" or "worse" than another.

Prescription, on the other hand, is an attempt to promote particular linguistic usages over others, often favoring a particular dialect or "acrolect". This may have the aim of establishing a linguistic standard, which can aid communication over large geographical areas. It may also, however, be an attempt by speakers of one language or dialect to exert influence over speakers of other languages or dialects (see Linguistic imperialism). An extreme version of prescriptivism can be found among censors, who attempt to eradicate words and structures that they consider to be destructive to society. Prescription, however, is practiced in the teaching of language, where certain fundamental grammatical rules and lexical terms need to be introduced to a second-language speaker who is attempting to acquire the language.

Analysis

Before the 20th century, linguists analyzed language on a diachronic plane, which was historical in focus. This meant that they would compare linguistic features and try to analyze language from the point of view of how it had changed between then and later. However, with Saussurean linguistics in the 20th century, the focus shifted to a more synchronic approach, where the study was more geared towards analysis and comparison between different language variations, which existed at the same given point of time.

At another level, the syntagmatic plane of linguistic analysis entails the comparison between the way words are sequenced, within the syntax of a sentence. For example, the article "the" is followed by a noun, because of the syntagmatic relation between the words. The paradigmatic plane on the other hand, focuses on an analysis that is based on the paradigms or concepts that are embedded in a given text. In this case, words of the same type or class may be replaced in the text with each other to achieve the same conceptual understanding.

Anthropology

The objective of describing languages is to often uncover cultural knowledge about communities. The use of anthropological methods of investigation on linguistic sources leads to the discovery of certain cultural traits among a speech community through its linguistic features. It is also widely used as a tool in language documentation, with an endeavor to curate endangered languages. However, now, linguistic inquiry uses the anthropological method to understand cognitive, historical, sociolinguistic and historical processes that languages undergo as they change and evolve, as well as general anthropological inquiry uses the linguistic method to excavate into culture. In all aspects, anthropological inquiry usually uncovers the different variations and relativities that underlie the usage of language.

Sources

Most contemporary linguists work under the assumption that spoken data and signed data is more fundamental than written data. This is because:

• Speech appears to be universal to all human beings capable of producing and perceiving it, while there have been many cultures and speech communities that lack written communication;
• Features appear in speech which aren't always recorded in writing, including phonological rules, sound changes, and speech errors;
• All natural writing systems reflect a spoken language (or potentially a signed one) they are being used to write, with even pictographic scripts like Dongba writing Naxi homophones with the same pictogram, and text in writing systems used for two languages changing to fit the spoken language being recorded;
• Speech evolved before human beings invented writing;
• People learnt to speak and process spoken language more easily and earlier than they did with writing.

Nonetheless, linguists agree that the study of written language can be worthwhile and valuable. For research that relies on corpus linguistics and computational linguistics, written language is often much more convenient for processing large amounts of linguistic data. Large corpora of spoken language are difficult to create and hard to find, and are typically transcribed and written. In addition, linguists have turned to text-based discourse occurring in various formats of computer-mediated communication as a viable site for linguistic inquiry.

The study of writing systems themselves, graphemics, is, in any case, considered a branch of linguistics.

History of linguistic thought

Early grammarians

Ancient Tamil inscription at Thanjavur

The formal study of language began in India with Pāṇini, the 5th century BC grammarian who formulated 3,959 rules of Sanskrit morphology. Pāṇini's systematic classification of the sounds of Sanskrit into consonants and vowels, and word classes, such as nouns and verbs, was the first known instance of its kind. In the Middle East Sibawayh (سیبویه‎) made a detailed description of Arabic in 760 AD in his monumental work, Al-kitab fi al-nahw (الكتاب في النحو‎, The Book on Grammar), the first known author to distinguish between sounds and phonemes (sounds as units of a linguistic system). Western interest in the study of languages began as early as in the East,^[31] but the grammarians of the classical languages did not use the same methods or reach the same conclusions as their contemporaries in the Indic world. Early interest in language in the West was a part of philosophy, not of grammatical description. The first insights into semantic theory were made by Plato in his Cratylus dialogue, where he argues that words denote concepts that are eternal and exist in the world of ideas. This work is the first to use the word etymology to describe the history of a word's meaning. Around 280 BC, one of Alexander the Great's successors founded a university (see Musaeum) in Alexandria, where a school of philologists studied the ancient texts in and taught Greek to speakers of other languages. While this school was the first to use the word "grammar" in its modern sense, Plato had used the word in its original meaning as "téchnē grammatikḗ" (Τέχνη Γραμματική), the "art of writing", which is also the title of one of the most important works of the Alexandrine school by Dionysius Thrax.^[32] Throughout the Middle Ages, the study of language was subsumed under the topic of philology, the study of ancient languages and texts, practiced by such educators as Roger Ascham, Wolfgang Ratke, and John Amos Comenius.^[33]

Comparative philology

In the 18th century, the first use of the comparative method by William Jones sparked the rise of comparative linguistics.^[34] Bloomfield attributes "the first great scientific linguistic work of the world" to Jacob Grimm, who wrote Deutsche Grammatik.^[35] It was soon followed by other authors writing similar comparative studies on other language groups of Europe. The scientific study of language was broadened from Indo-European to language in general by Wilhelm von Humboldt, of whom Bloomfield asserts:^[35]

This study received its foundation at the hands of the Prussian statesman and scholar Wilhelm von Humboldt (1767–1835), especially in the first volume of his work on Kavi, the literary language of Java, entitled Über die Verschiedenheit des menschlichen Sprachbaues und ihren Einfluß auf die geistige Entwickelung des Menschengeschlechts (On the Variety of the Structure of Human Language and its Influence upon the Mental Development of the Human Race).

Structuralism

Early in the 20th century, Saussure introduced the idea of language as a static system of interconnected units, defined through the oppositions between them. By introducing a distinction between diachronic to synchronic analyses of language, he laid the foundation of the modern discipline of linguistics. Saussure also introduced several basic dimensions of linguistic analysis that are still foundational in many contemporary linguistic theories, such as the distinctions between syntagm and paradigm, and the langue- parole distinction, distinguishing language as an abstract system (langue) from language as a concrete manifestation of this system (parole).^[36] Substantial additional contributions following Saussure's definition of a structural approach to language came from The Prague school, Leonard Bloomfield, Charles F. Hockett, Louis Hjelmslev, Émile Benveniste and Roman Jakobson.^[37][38]

Generativism

During the last half of the 20th century, following the work of Noam Chomsky, linguistics was dominated by the generativist school. While formulated by Chomsky in part as a way to explain how human beings acquire language and the biological constraints on this acquisition, in practice it has largely been concerned with giving formal accounts of specific phenomena in natural languages. Generative theory is modularist and formalist in character. Chomsky built on earlier work of Zellig Harris to formulate the generative theory of language. According to this theory the most basic form of language is a set of syntactic rules universal for all humans and underlying the grammars of all human languages. This set of rules is called Universal Grammar, and for Chomsky describing it is the primary objective of the discipline of linguistics. For this reason the grammars of individual languages are of importance to linguistics only in so far as they allow us to discern the universal underlying rules from which the observable linguistic variability is generated.In the classic formalisation of generative grammars first proposed by Noam Chomsky in the 1950s,^[39][40] a grammar G consists of the following components:

• A finite set N of nonterminal symbols, none of which appear in strings formed from G.
• A finite set of terminal symbols that is disjoint from N.
• A finite set P of production rules, that map from one string of symbols to another.

A formal description of language attempts to replicate a speaker's knowledge of the rules of their language, and the aim is to produce a set of rules that is minimally sufficient to successfully model valid linguistic forms.

Functionalism

Functional theories of language propose that since language is fundamentally a tool, it is reasonable to assume that its structures are best analyzed and understood with reference to the functions they carry out. Functional theories of grammar differ from formal theories of grammar, in that the latter seek to define the different elements of language and describe the way they relate to each other as systems of formal rules or operations, whereas the former defines the functions performed by language and then relates these functions to the linguistic elements that carry them out. This means that functional theories of grammar tend to pay attention to the way language is actually used, and not just to the formal relations between linguistic elements.^[41]
Functional theories describe language in term of the functions existing at all levels of language.

• Phonological function: the function of the phoneme is to distinguish between different lexical material.
• Semantic function: (Agent, Patient, Recipient, etc.), describing the role of participants in states of affairs or actions expressed.
• Syntactic functions: (e.g. subject and Object), defining different perspectives in the presentation of a linguistic expression
• Pragmatic functions: (Theme and Rheme, Topic and Focus, Predicate), defining the informational status of constituents, determined by the pragmatic context of the verbal interaction. Functional descriptions of grammar strive to explain how linguistic functions are performed in communication through the use of linguistic forms.

Cognitivism

In the 1950s, a new school of thought known as cognitivism emerged through the field of psychology. Cognitivists lay emphasis on knowledge and information, as opposed to behaviorism, for instance. 

Cognitivism emerged in linguistics as a reaction to generativist theory in the 1970s and 1980s. Led by theorists like Ronald Langacker and George Lakoff, cognitive linguists propose that language is an emergent property of basic, general-purpose cognitive processes. In contrast to the generativist school of linguistics, cognitive linguistics is non-modularist and functionalist in character. Important developments in cognitive linguistics include cognitive grammar, frame semantics, and conceptual metaphor, all of which are based on the idea that form–function correspondences based on representations derived from embodied experience constitute the basic units of language.Cognitive linguistics interprets language in terms of concepts (sometimes universal, sometimes specific to a particular tongue) that underlie its form. It is thus closely associated with semantics but is distinct from psycholinguistics, which draws upon empirical findings from cognitive psychology in order to explain the mental processes that underlie the acquisition, storage, production and understanding of speech and writing. Unlike generative theory, cognitive linguistics denies that there is an autonomous linguistic faculty in the mind; it understands grammar in terms of conceptualization; and claims that knowledge of language arises out of language use.^[42] Because of its conviction that knowledge of language is learned through use, cognitive linguistics is sometimes considered to be a functional approach, but it differs from other functional approaches in that it is primarily concerned with how the mind creates meaning through language, and not with the use of language as a tool of communication.

Areas of research

Historical linguistics

Historical linguists study the history of specific languages as well as general characteristics of language change. The study of language change is also referred to as "diachronic linguistics" (the study of how one particular language has changed over time), which can be distinguished from "synchronic linguistics" (the comparative study of more than one language at a given moment in time without regard to previous stages). Historical linguistics was among the first sub-disciplines to emerge in linguistics, and was the most widely practiced form of linguistics in the late 19th century. However, there was a shift to the synchronic approach in the early twentieth century with Saussure, and became more predominant in western linguistics with the work of Noam Chomsky.

Sociolinguistics

Sociolinguistics is the study of how language is shaped by social factors. This sub-discipline focuses on the synchronic approach of linguistics, and looks at how a language in general, or a set of languages, display variation and varieties at a given point in time. The study of language variation and the different varieties of language through dialects, registers, and ideolects can be tackled through a study of style, as well as through analysis of discourse. Sociolinguists research on both style and discourse in language, and also study the theoretical factors that are at play between language and society.

Developmental linguistics

Developmental linguistics is the study of the development of linguistic ability in individuals, particularly the acquisition of language in childhood. Some of the questions that developmental linguistics looks into is how children acquire language, how adults can acquire a second language, and what the process of language acquisition is.

Neurolinguistics

Neurolinguistics is the study of the structures in the human brain that underlie grammar and communication. Researchers are drawn to the field from a variety of backgrounds, bringing along a variety of experimental techniques as well as widely varying theoretical perspectives. Much work in neurolinguistics is informed by models in psycholinguistics and theoretical linguistics, and is focused on investigating how the brain can implement the processes that theoretical and psycholinguistics propose are necessary in producing and comprehending language. Neurolinguists study the physiological mechanisms by which the brain processes information related to language, and evaluate linguistic and psycholinguistic theories, using aphasiology, brain imaging, electrophysiology, and computer modeling.

Applied linguistics

Linguists are largely concerned with finding and describing the generalities and varieties both within particular languages and among all languages. Applied linguistics takes the results of those findings and "applies" them to other areas. Linguistic research is commonly applied to areas such as language education, lexicography, translation, language planning, which involves governmental policy implementation related to language use, and natural language processing. "Applied linguistics" has been argued to be something of a misnomer.^[43] Applied linguists actually focus on making sense of and engineering solutions for real-world linguistic problems, and not literally "applying" existing technical knowledge from linguistics. Moreover, they commonly apply technical knowledge from multiple sources, such as sociology (e.g., conversation analysis) and anthropology. (Constructed language fits under Applied linguistics.)
Today, computers are widely used in many areas of applied linguistics. Speech synthesis and speech recognition use phonetic and phonemic knowledge to provide voice interfaces to computers. Applications of computational linguistics in machine translation, computer-assisted translation, and natural language processing are areas of applied linguistics that have come to the forefront. Their influence has had an effect on theories of syntax and semantics, as modeling syntactic and semantic theories on computers constraints.

Linguistic analysis is a sub-discipline of applied linguistics used by many governments to verify the claimed nationality of people seeking asylum who do not hold the necessary documentation to prove their claim.^[44] This often takes the form of an interview by personnel in an immigration department. Depending on the country, this interview is conducted either in the asylum seeker's native language through an interpreter or in an international lingua franca like English.^[44] Australia uses the former method, while Germany employs the latter; the Netherlands uses either method depending on the languages involved.^[44] Tape recordings of the interview then undergo language analysis, which can be done either by private contractors or within a department of the government. In this analysis, linguistic features of the asylum seeker are used by analysts to make a determination about the speaker's nationality. The reported findings of the linguistic analysis can play a critical role in the government's decision on the refugee status of the asylum seeker.^[44]

Inter-disciplinary fields

Within the broad discipline of linguistics, various emerging sub-disciplines focus on a more detailed description and analysis of language, and are often organized on the basis of the school of thought and theoretical approach that they pre-suppose, or the external factors that influence them.

Semiotics

Semiotics is the study of sign processes (semiosis), or signification and communication, signs, and symbols, both individually and grouped into sign systems, including the study of how meaning is constructed and understood. Semioticians often do not restrict themselves to linguistic communication when studying the use of signs but extend the meaning of "sign" to cover all kinds of cultural symbols. Nonetheless, semiotic disciplines closely related to linguistics are literary studies, discourse analysis, text linguistics, and philosophy of language. Semiotics, within the linguistics paradigm, is the study of the relationship between language and culture. Historically, Edward Sapir and Ferdinand De Saussure's structuralist theories influenced the study of signs extensively until the late part of the 20th century, but later, post-modern and post-structural thought, through language philosophers including Jacques Derrida, Mikhail Bakhtin, Michel Foucault, and others, have also been a considerable influence on the discipline in the late part of the 20th century and early 21st century.^[45] These theories emphasise the role of language variation, and the idea of subjective usage, depending on external elements like social and cultural factors, rather than merely on the interplay of formal elements.

Language documentation

Since the inception of the discipline of linguistics, linguists have been concerned with describing and analysing previously undocumented languages. Starting with Franz Boas in the early 1900s, this became the main focus of American linguistics until the rise of formal structural linguistics in the mid-20th century. This focus on language documentation was partly motivated by a concern to document the rapidly disappearing languages of indigenous peoples. The ethnographic dimension of the Boasian approach to language description played a role in the development of disciplines such as sociolinguistics, anthropological linguistics, and linguistic anthropology, which investigate the relations between language, culture, and society.

The emphasis on linguistic description and documentation has also gained prominence outside North America, with the documentation of rapidly dying indigenous languages becoming a primary focus in many university programs in linguistics. Language description is a work-intensive endeavour, usually requiring years of field work in the language concerned, so as to equip the linguist to write a sufficiently accurate reference grammar. Further, the task of documentation requires the linguist to collect a substantial corpus in the language in question, consisting of texts and recordings, both sound and video, which can be stored in an accessible format within open repositories, and used for further research.^[46]

Translation

The sub-field of translation includes the translation of written and spoken texts across mediums, from digital to print and spoken. To translate literally means to transmute the meaning from one language into another. Translators are often employed by organisations, such as travel agencies as well as governmental embassies to facilitate communication between two speakers who do not know each other's language. Translators are also employed to work within computational linguistics setups like Google Translate for example, which is an automated, programmed facility to translate words and phrases between any two or more given languages. Translation is also conducted by publishing houses, which convert works of writing from one language to another in order to reach varied audiences. Academic Translators, specialize and semi specialize on various other disciplines such as; Technology, Science, Law, Economics etc.

Biolinguistics

Biolinguistics is the study of natural as well as human-taught communication systems in animals, compared to human language. Researchers in the field of biolinguistics have also over the years questioned the possibility and extent of language in animals.

Clinical linguistics

Clinical linguistics is the application of linguistic theory to the fields of Speech-Language Pathology. Speech language pathologists work on corrective measures to cure communication disorders and swallowing disorders.

Computational linguistics

Computational linguistics is the study of linguistic issues in a way that is 'computationally responsible', i.e., taking careful note of computational consideration of algorithmic specification and computational complexity, so that the linguistic theories devised can be shown to exhibit certain desirable computational properties and their implementations. Computational linguists also work on computer language and software development.

Evolutionary linguistics

Evolutionary linguistics is the interdisciplinary study of the emergence of the language faculty through human evolution, and also the application of evolutionary theory to the study of cultural evolution among different languages. It is also a study of the dispersal of various languages across the globe, through movements among ancient communities.^[47]

Forensic linguistics

Forensic linguistics is the application of linguistic analysis to forensics. Forensic analysis investigates on the style, language, lexical use, and other linguistic and grammatical features used in the legal context to provide evidence in courts of law. Forensic linguists have also contributed expertise in criminal cases.