Almost every human child succeeds in learning language. As a result, people often tend to take the process of language learning for granted. To many, language seems like a basic instinct, as simple as breathing or blinking. But language is not simple at all; in fact it is the most complex skill that a human being will ever master. That nearly all people succeed in learning this complex skill demonstrates how well language has adapted to human nature. In a very real sense, language is the complete expression of what it means to be human.
Linguists in the tradition of Noam Chomsky tend to think of language as having a universal core from which individual languages select out a particular configuration of features, parameters, and settings. As a result, they see language as an instinct that is driven by specifically human evolutionary adaptations. In their view, language resides in a unique mental organ that has been given as a "special gift" to the human species. This mental organ contains rules, constraints, and other structures that can be specified by linguistic analysis.
Psychologists and those linguists who reject the Chomskyan approach often view language learning from a very different perspective. To the psychologist, language acquisition is a window on the operation of the human mind. The patterns of language emerge not from a unique instinct but from the operation of general processes of evolution and cognition. For researchers who accept this emergentist approach, the goal of language acquisition studies is to understand how regularities in linguistic form emerge from the operation of low-level physical, neural, and social processes. Before considering the current state of the dialog between the view of language as a hard-wired instinct and the view of language as an emergent process, it will be useful to review a few basic facts about the shape of language acquisition and some of the methods that are used to study it.
The Basic Components of Human Language
Human language involves both receptive and productive use. Receptive language use occurs during the comprehension or understanding of words and sentences. Productive language use involves idea generation and the articulation of words in speech. Both reception and production utilize the four basic structural components of language:
- Phonology: The system of the sound segments that humans use to build up words. Each language has a different set of these segments or phonemes, and children quickly come to recognize and then produce the speech segments that are characteristic of their native language.
- Semantics: The system of meanings that are expressed by words and phrases. In order to serve as a means of communication between people, words must have a shared or conventional meaning. Picking out the correct meaning for each new word is a major learning task for children.
- Grammar: The system of rules by which words and phrases are arranged to make meaningful statements. Children need to learn how to use the ordering of words to mark grammatical functions such as subject or direct object.
- Pragmatics: The system of patterns that determine how humans can use language in particular social settings for particular conversational purposes. Children learn that conversations customarily begin with a greeting, require turn taking, and concern a shared topic. They come to adjust the content of their communications to match their listener's interests, knowledge, and language ability.
These four basic systems can be extended and elaborated when humans use language for special purposes, such as for poetry, song, legal documents, or scientific discourse. The literate control of language constructs additional complex social, cognitive, and linguistic structures that are built on top of the four basic structural components.
Methods for Studying Language Acquisition
The methods used to study language development are mostly quite straightforward. The primary method involves simply recording and transcribing what children say. This method can be applied even from birth. Tape recordings become particularly interesting, however, when the child begins systematic babbling and the first productions of words. Using videotape, researchers can link up the child's use of verbal means with their use of gesture and nonlinguistic cries to draw attention to their desires and interests.
Methods for studying comprehension are a bit more complicated. During the first year, researchers can habituate the infant to some pattern of sounds and then suddenly change that pattern to see if the infant notices the difference. From about nine months onward, children can be shown pictures of toys along with their names, and then researchers can measure whether the children prefer these pictures to some unnamed distracter pictures. Later on, children can be asked to answer questions, repeat sentences, or make judgments about grammar. Researchers can also study children by asking their parents to report about them. Parents can record the times when their children first use a given sound or word or first make some basic types of child errors. Each of these methods has different goals, and each also has unique possibilities and pitfalls associated with it. Having obtained a set of data from children or their parents, researchers next need to group these data into measures of particular types of language skills, such as vocabulary, sentences, concepts, or conversational abilities.
Phases in Language Development
William James (1890) described the world of the newborn as a "blooming, buzzing confusion." It is now known, however, that, on the auditory level at least, the newborn's world is remarkably well structured. The cochlea (in the inner ear) and the auditory nerve (which connects the inner ear with the brain) provide extensive preprocessing of signals for pitch and intensity. In the 1970s and 1980s, researchers discovered that human infants were specifically adapted at birth to perceive contrasts in sounds such as that between /p/and /b/, as in the words pit and bit. Subsequent research showed that even chinchillas are capable of making this distinction. This suggests that much of the basic structure of the infant's auditory world can be attributed to fundamental processes in the mammalian ear. Moreover, there is evidence that some of these early perceptual abilities are lost as the infant begins to acquire the distinctions actually used by the native language. Beyond this basic level of auditory processing, it appears that infants have a remarkable capacity to record and store sequences of auditory events. It is as if the infant has a tape recorder in the brain's auditory cortex that records input sounds, replays them, and accustoms the ear to their patterns.
Children tend to produce their first words sometime between nine and twelve months. One-year-olds have about 5 words in their vocabulary on average, although individual children may have none or as many as thirty; by two years of age, average vocabulary size is more than 150 words, with a range among individual children from as few as 10 to as many as 450 words. Children possess a vocabulary of about 14,000 words by six years of age; adults have an estimated average of 40,000 words in their working vocabulary at age forty. In order to achieve such a vocabulary, a child must learn to say at least a few new words each day from birth.
One of the best predictors of a child's vocabulary development is the amount and diversity of input the child receives. Researchers have found that verbal input can be as great as three times more available in educated families than in less educated families. These facts have led educators to suspect that basic and pervasive differences in the level of social support for language learning lie at the root of many learning problems in the later school years. Social interaction (quality of attachment; parent responsiveness, involvement, sensitivity, and control style) and general intellectual climate (providing enriching toys, reading books, encouraging attention to surroundings) predict developing language competence in children as well. Relatively uneducated and economically disadvantaged mothers talk less frequently to their children compared with more educated and affluent mothers, and correspondingly, children of less educated and less affluent mothers produce less speech. Socioeconomic status relates to both child vocabulary and to maternal vocabulary. Middle-class mothers expose their children to a richer vocabulary, with longer sentences and a greater number of word roots.
Whereas vocabulary development is marked by spectacular individual variation, the development of grammatical and syntactic skills is highly stable across children. Children's early one-word utterances do not yet trigger the need for syntactic patterns, because they are still only one-word long. By the middle of the second year, when children's vocabularies grow to between 50 and 100 words, they begin to combine words in what has been termed "telegraphic speech." Utterances typical of this period include forms such as "where Mommy," "my shoe," "dolly chair," and "allgone banana."
At this same time, children are busy learning to adjust their language to suit their audience and the situation. Learning the pragmatic social skills related to language is an ongoing process. Parents go to great efforts to teach their children to say "please" and "thank you" when needed, to be deferential in speaking to adults, to remember to issue an appropriate greeting when they meet someone, and not to interrupt when others are speaking. Children fine-tune their language skills to maintain conversations, tell stories, ask or argue for favors, or tattle on their classmates. Early on, they also begin to acquire the metalinguistic skills involved in thinking and making judgments about language.
As children move on to higher stages of language development and the acquisition of literacy, they depend increasingly on broader social institutions. They depend on Sunday school teachers for knowledge about Biblical language, prophets, and the geography of the Holy Land. They attend to science teachers to gain vocabulary and understandings about friction, molecular structures, the circulatory system, and DNA. They rely on peers to understand the language of the streets, verbal dueling, and the use of language for courtship. They rely on the media for role models, fantasies, and stereotypes. When they enter the workplace, they will rely on their coworkers to develop a literate understanding of work procedures, union rules, and methods for furthering their status. By reading to their children, telling stories, and engaging in supportive dialogs, parents set the stage for their children's entry into the world of literature and schooling. Here, again, the parent and teacher must teach by displaying examples of the execution and generation of a wide variety of detailed literate practices, ranging from learning to write through outlines to taking notes in lectures.
Special Gift or Emergence?
Having briefly covered the methods used to study language acquisition and the basic phases in development, it is now possible to return to this question: Is language development best characterized as the use of a "special gift" or as an emergent result of various cognitive, neural, physiological, and social pressures? There are good arguments in favor of each position.
The special gift position views language as an instinct. People are often overpowered by the "urge to speak." Young children must feel this urge when they interact with others and have not yet learned how to use words correctly. It is important to recognize, however, that crickets, birds, snakes, and many other species can be possessed by a similar urge to produce audible chirps, songs, and rattling. In themselves, these urges do not amount to a special gift for language learning. Better evidence for the special gift comes from the study of children who have been cut off from communication by cruel parents, ancient Pharaohs, or accidents of nature. The special gift position holds that, if the special gift for language is not exercised by some early age, perhaps six or seven, it will be lost forever. None of the isolation experiments that have been conducted, however, can be viewed as providing good evidence for this claim. In many cases, the children are isolated because they are brain-injured. In other cases, the isolation itself produces brain injury. In a few cases, children as old as six to eight years of age have successfully acquired language even after isolation. Thus, the most that can be concluded from these experiments is that it is unlikely that the special gift expires before age eight.
The second form of evidence in favor of the notion of a special gift comes from the observation that children are able to learn some grammatical structures without apparent guidance from the input. The argumentation involved here is sometimes rather subtle. For example, Chomsky noted that children would never produce "Is the boy who next in line is tall?" as a question deriving from the sentence "The boy who is next in line is tall." Instead, they will inevitably produce the question as, "Is the boy who is next in line tall?" That children always know which of the forms of the verb is to move to the front of the sentence, even without ever having heard such a sentence from their parents, indicates to Chomsky that language must be a special gift.
Although the details of Chomsky's argument are controversial, his basic insight here seems solid. There are some aspects of language that seem so fundamental that humans hardly need to learn them. Nevertheless, the specific structures examined by linguistic theory involve only a small set of core grammatical features. When looking more generally at the full shape of the systems of lexicon, phonology, pragmatics, and discourse, much greater individual variation in terms of overall language proficiency appears.
To explain these differences, it is necessary to view language learning as emerging from multiple sources of support. One source of support is the universal concept all humans have about what language can be. A second source of support is input from parents and peers. This input is most effective when it directly elaborates or expands on things the child has already said. For example, if the child says "Mommy go store," the parent can expand the child's production by saying "Yes, Mommy is going to the store." From expansions of this type, children can learn a wide variety of grammatical and lexical patterns. A third source of support is the brain itself. Through elaborate connections among auditory, vocal, relational, and memory areas, humans are able to store linguistic patterns and experiences for later processing. A fourth source of support are the generalizations that people produce when they systematize and extend language patterns. Recognizing that English verbs tend to produce their past tense by adding the suffix -ed, children can produce over-generalizations such as "goed" or "runned." Although these overgeneralizations are errors, they represent the productive use of linguistic creativity.
Individual children will vary markedly in the extent to which they can rely on these additional sources of support. Children of immigrant families will be forced to acquire the language of the new country not from their parents, but from others. Children with hearing impairments or the temporary impairments brought on by otitis media (ear infections) will have relatively less support for language learning from clear auditory input. Blind children will have good auditory support but relatively less support from visual cues. Children with differing patterns of brain lesions may have preserved auditory abilities, but impaired ability to control speech. Alternatively, other children will have only a few minor impairments to their short-term memory that affect the learning of new words.
Because language is based on such a wide variety of alternative cognitive skills, children can often compensate for deficits in one area by emphasizing their skills in another area. The case of Helen Keller is perhaps the best such example of compensation. Although Keller had lost both her hearing and her vision, she was able to learn words by observing how her guardian traced out patterns of letters in her hand. In this way, even when some of the normal supports are removed, children can still learn language. The basic uses of language are heavily over-determined by this rich system of multiple supports. As a child moves away from the basic uses of language into the more refined areas of literacy and specific genres, progress can slow. In these later periods, language is still supported by multiple sources, but each of the supports grows weaker, and progress toward the full competency required in the modern workplace is less inevitable.
See also: Bilingualism, Second Language Learning, AND English as a Second Language; Categorization and Concept Learning; Language and Education; Literacy and Reading.
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Human language is a remarkable symbolic means of communication that makes it possible for individuals to convey their thoughts and feelings to others. Although babies are born completely without language, by the time they are three or four years old, children have acquired thousands of vocabulary words, complex grammatical and sound systems, and the ability to speak appropriately in many different social situations. Although societies around the world differ in many ways, language is a universal phenomenon, and children around the world acquire their native language in very similar ways.
The Structure of Language
All human languages include a number of systematic features that the young learner must master. Languages are organized hierarchically and include a number of subsystems. The systems of language include phonology, morphology, the lexicon and semantics, syntax, pragmatics, and discourse. Children begin to acquire some aspects of their language during their first few months of life.
The phonology of a language is its sound system. This system includes all of the significant sounds that are used in the language, as well as the ways in which they can be combined to make acceptable-sounding new words. For example, a new cereal in English might be called "Crunchix," but not "Kshicrun," because acceptable English words cannot begin with "kshi." Across the world, languages use many hundreds of different sounds, from trills on the tongue to scrapes in the throat, but each language employs only a small subset of these possible sounds. The sounds that the speakers of a language regard as different from one another are its phonemes. In English, for example, people make slightly different "p" sounds in words such as pool, where the "p" is followed by a puff of air (aspiration), or in words such as spool, where there is no puff of air following the "p." English speakers perceive these as just one sound, the phoneme "p." In the Hindi language spoken in India, however, the "p" without the puff of air and the "p" with the puff of air are different phonemes. The Hindi language has words such as phal ("fruit") and pal ("moment") that differing only in that puff of air. Some languages have many more phonemes than others, but it is typical for a language to have about twenty-six consonant and nine vowel phonemes. In written English, the alphabet does not always represent the sounds of the language clearly or consistently, but in Spanish or Russian, the sounds of the language and the letters used to represent them correspond quite well.
The morphology of a language is a set of rules for word formation and variation. (The term "rules" is used to refer to the way things are regularly done in a language by speakers of that language, not to a set of formal regulations that are taught in school.) Morphemes are the smallest units in a language that carry definable meaning or grammatical function (the word "hat," or the plural ending "-s," for example.) Addition of a morpheme can change a word from singular to plural or indicate the tense of a verb. Other morphological rules allow one word to be changed into another word (e.g., "fit" into "unfit") or into another part of speech (e.g., "fit" into "fitness").
The lexicon and semantics of a language are its vocabulary words and the meanings that go with them. Speakers of a language have a remarkably large and complicated mental lexicon or dictionary. English-speaking adults can recognize more than 50,000 different words, and in common speech, they can come up with or produce anywhere from 20,000 to 50,000 of those words.
The syntax of a language includes the ways that words can be combined or rearranged in order to produce different kinds of utterances (e.g., questions, negatives, imperatives, and passives). Children soon learn to understand syntax—such as the difference between "The tiger chases the girl" and "The girl chases the tiger." In English syntax, meaning depends on word order. Typically, the first noun in a sentence is the subject, and the next is the object. Subjects are often followed by verbs. All sentences do not follow this pattern in English, however, and children must learn to interpret passives and other complex constructions. Complex syntax is not mastered until well into the school years.
Pragmatics is the appropriate use of language in various social situations. People all know how to talk in different ways, depending on the situation they are in, or the person they are addressing. People speak differently to babies, to informal acquaintances, and to people in authority, for example. If people are called into court, they do not say "Hi, sweetie" to the judge, although they might say this to their neighbor's little girl; people's knowledge of pragmatics leads to their choice of words and their interpretation of the language that they hear in social situations. Depending on their own roles, the person they are addressing, and the situation they are in, speakers vary their language according to a complex set of pragmatic conventions. Parents stress the importance of pragmatics when they teach very young children social routines, such as when to say "hello," "thank you," and "bye-bye."
Children must gain an understanding of how connected sentences are related to each other. In English, people must use a noun before a pronoun referring to the same thing can be used. Thus, "My dog ate it" is not a good way to begin a conversation with one's teacher, but saying "it" makes sense if the teacher has just asked where the student's homework is, since, in this case, the "it" refers to the homework. How to make a conversation or engage in other spoken or written activities that last longer than a single sentence requires knowledge of the discourse conventions of a language. After children enter school and begin to gain literacy skills, learning to use all of the discourse rules that are involved in expository writing is a particularly difficult task.
Stages of Language Acquisition
Understanding how children acquire language makes it possible to identify instances where they may not be developing language in an age-appropriate way, and may need intervention or remediation. It also allows people to know when immature-sounding language is part of normal language acquisition (such as when a two-year-old says "top" instead of "stop," since it is normal for a child of this age to simplify the pronunciation of consonant clusters). Knowing what stage of language development a child has reached also makes it possible for people to interpret what the child says and to tailor their own language so that communication is effective.
At birth, infants are prepared to learn any language. For example, an American baby adopted by an Inuit-speaking Eskimo family would grow up speaking fluent Inuktitut and have no trouble saying words such as qikturiaqtauniq ("mosquito bite"). However, even before their first birthdays, babies begin to lose the ability to hear the distinctions among phonemes in languages other than their own. By around the age of six months, babies have already begun to hear the sounds of their own language in the same way that adult speakers do, as Patricia Kuhl and her associates (1992) have shown in their research.
Human infants are intensely social; even in the first few days of life, they look into the eyes of their mothers and are sensitive to the emotional tone of the human voice. Long before they say their first words, babies begin to acquire the communicative skills that underlie language. As they get a little older they begin to take their turn in little "conversations" with their caregivers. The adult speaks, and the baby's turn can be something as simple as a sneeze or a burp. As they near their first birthday, many babies understand fifty or more words and can point out the right person when asked "Where's mommy?" They show that they are intentional communicators even before they begin to talk, by using gestures, by using consistent word-like sounds, and by becoming insistent when they are not understood.
As their communicative skills grow, the ability of infants to produce speech sounds also develops. They begin to babble, or play with sounds, midway through the first year. At first, babbling may consist of just a few sounds. Soon, the infant begins to babble repeated syllables, such as "dada" and "baba." A little later, many babies babble long sequences of syllables that resemble the sentences of their language. Communicative development in the first year has universal features and occurs in this way in all parts of the world, regardless of the degree of sophistication of the culture or complexity of the language being learned. First words emerge during the babbling stage and are produced by many infants at about the same age when they take their first steps, around their first birthday or a little later.
Once babies have begun to produce a few words, they begin to use them for a number of purposes. The earliest words children acquire refer to things in their immediate world that are important to them. They learn the names of their relatives (e.g., their mommy or daddy) and words referring to food, to games, toys, animals, body parts, and simple actions (e.g., eat, sit, up, down). Babies tend to learn the names of things that move or that they can act on (e.g., a mitten or ball) rather than something that is not related to their everyday activities (e.g., the sky or a floor). Early words represent different parts of speech, such as nouns, verbs, and adjectives, although nouns tend to make up the largest category. These words are also simple in terms of their pronunciation and generally not more than two syllables long. Infants use their single words in fairly complex ways. They may say "cookie," meaning "I want a cookie" or "that is a cookie" or "another cookie." In this one-word stage of language acquisition, children are restricted to the here-and-now. They do not talk about the future or the past.
Late in the second year, after they have acquired about fifty words, children begin to put the words together into little two-word sentences. Children's early two-word utterances also have universal characteristics. Children around the world are trying to get across very much the same kinds of ideas. They want to ask for more of something ("more cookie"), to reject something ("no sock"), to notice something ("hi, doggie!"), or point out that something has disappeared ("all-gone milk"). These early word combinations are called telegraphic utterances, because the child makes them without articles, prepositions, inflections, or other little grammatical words, and they sound like telegrams. The child can now say such things as "That kitty," meaning "That is a kitty," and "Mommy sock," meaning "Mommy's sock" or "Mommy, give me my sock" or "Mommy is putting on her sock." The telegraphic utterances become longer as the child gains language ability and becomes able to say even more things. Although the language of toddlers is similar across all languages during the telegraphic stage, what is acquired next depends on the structure of the language that the child is learning.
As the child's utterances grow longer, grammatical forms begin to appear. In English, children begin to add articles, prepositions, and inflections to their language. English-speaking children learn the articles "a" and "the," but in languages such as Chinese or Russian, which do not have articles, they learn other things. One remarkable discovery has been that children acquiring a given language follow essentially the same order of acquisition. As the vocabulary of young children continues to grow they gain a knowledge of morphology even before they enter kindergarten that allows them to make plurals or past tenses of words they have never before heard. In fact, when a young child says "mouses" instead of "mice," this is good evidence that the child is learning the regular forms of the language and knows how to make plurals, even if he or she has not yet learned the irregular forms. Almost all pre-school children produce regularized plurals and past tenses such as "gooses" and "ringed" as they acquire the systematic aspects of their language. By the time they enter school, children also know how to make all of the basic sentence types of their language, and they can use them in connected discourse.
Although the basics of the language are acquired in the first few years of life, there is much to be accomplished during the school years as well. By the age of six, children have acquired approximately fourteen thousand words, as the linguist Eve Clark (1993) points out in her book The Lexicon in Acquisition. As children grow older, the words that are related to each other become associated in the mental lexicon, so that a word such as "doctor" becomes linked to words such as "nurse," "hospital," and "stethoscope." This growing vocabulary is necessary for success in school.
School-age children begin to use language in a variety of new ways. Children develop pragmatic skills as they interact with others, and they learn how to use language appropriately in many different situations. Their language becomes decontextualized, in the sense that they can now talk about things that are not in their immediate environment (e.g., ancient history, events in other countries). Another new development is the ability to think about language itself, to know what a word is and even what their favorite words are. This new skill, called metalinguistic awareness (awareness of language), contributes to their ability to make jokes and riddles and to engage in other kinds of wordplay with their peers. It also helps them to acquire literacy skills. Learning to read and write are, of course, essential developments in the school years.
Although it is evident that the major aspects of language acquisition are complete by the time an individual has finished formal schooling, language skills continue to develop throughout the life span. Individuals are continually adding new vocabulary and learning new pragmatic and discourse skills.
Theories of Language Acquisition
Although many researchers have described what happens during the course of language development, there is much debate over just how children are able to acquire such a complex system in such a short time. Several major theories have attempted to explain the mechanisms of language acquisition:
Learning theory explanations of language development are based on the work of B. F. Skinner and other behaviorists, who view language as just one kind of human behavior that is learned. According to this theory, children learn to imitate adults, who also actively teach the children the language. For example, when babies begin to babble, adults reinforce or reward the babbling. A little later, the adults are thought to reward systematically the utterances that become closer and closer approximations of the target language until, eventually, children are speaking like the adults around them.
Many linguists, including Noam Chomsky and Steven Pinker, believe that the basic principles of language are innate, or present at birth, and that only human beings are capable of language. According to this view, adults' role in children's language development is minimal; all that is necessary is for the infant to be exposed to language. A built-in mechanism in the brain—referred to as a "language acquisition device" (LAD)—allows the child to develop language skills in a very short time without explicit teaching. These theorists believe that language is a unique and separate ability and that acquisition is possible only during a brief critical period during early childhood.
Jean Piaget was a major proponent of cognitive developmental theory. According to this theory, language is not a separate capacity; rather, it is just one facet of children's general intellectual ability. Cognitive theorists believe that infants use their senses and motor skills to begin to learn about the world—for example, that cats are furry and say "meow"—and that once they have gained such knowledge, they map words such as "kitty" onto the concepts that they have already attained.
Social interactionists, including Jerome Bruner and Catherine Snow, view language as a facet of communicative behavior that develops through interaction with other human beings. They agree that humans have special linguistic abilities that are not shared by other animals, but they hold that children acquire language in part through the help of others, rather than purely through their own mental activity. Thus, interaction, rather than exposure, is seen as necessary. These researchers have found that there are special ways of talking to young language learners the world over that are tailored or fine-tuned to children's cognitive and communicative needs. They believe that the clear and simple child-directed language that adults use helps children to figure out how language works.
Understanding Language Acquisition
All of the components of language are important for communication, and disruption at any level can lead to miscommunication or even failure to communicate. For example, an individual who has not correctly acquired the sound system will not be able to make important distinctions between similar-sounding words (e.g., the difference between "ship" and "sheep"). Morphology and syntax are needed to convey meaning. A rich, shared lexicon, or vocabulary, is needed in a complex society in order to make reference to people, places, and concepts. The pragmatic system is particularly important in communication because even slight misuses or inappropriate uses of pragmatics can have quite disastrous interpersonal results, particularly if pragmatic conventions that govern politeness are violated. Finally, everyone must learn how discourse works in order to communicate about any connected set of ideas or events. If people understand how language is structured, they gain insight into what the basic building blocks of messages are and into what may have gone awry when communication fails.
Bruner, Jerome. (1983). Child's Talk: Learning to Use Language. New York: W. W. Norton.
Chomsky, Noam. (1965). Aspects of a Theory of Syntax.Cambridge, MA: MIT Press.
Gleason, Jean Berko, ed. (2000). The Development of Language. Boston: Allyn & Bacon.
Kuhl, Patricia K.; Williams, Karen A.; Lacerda, Francisco; Stevens, Kenneth; and Lindblom, Bjoern. (1992). "Linguistic Experience Alters Phonetic Perception in Infants by 6 Months of Age." Science 255 (5044):606-608.
Piaget, Jean. (1926). The Language and Thought of the Child. New York: Harcourt Brace Jovanovich.
Pinker, Steven. (1994). The Language Instinct: How the Mind Creates Language. New York: Morrow.
Skinner, Burrhus F. (1957). Verbal Behavior. Englewood Cliffs, NJ: Prentice-Hall.
Snow, Catherine E. (1989). "Understanding Social Interaction and Language Acquisition: Sentences Are Not Enough." In Interaction in Human Development, eds. Marc Bornstein and Jerome Bruner. Hillsdale, NJ: Lawrence Erlbaum.
Jean Berko Gleason
Language acquisition is defined as a natural progession or development in the use of language, typified by infants and young children learning to talk. It is an unconscious process that occurs when language is used in ordinary conversation. Language acquisition is distinguished from intentional study of a language by its informality.
Theories of language acquisition
Developmental psychologists are not agreed as to how humans acquire the ability to speak their first language. It was only in the 1950s that the availability of portable tape recorders made it possible for researchers to record children's speech patterns for later analysis in the laboratory. One early theory of language acquisition was based on imitation, which is the notion that children learn to speak by imitating adults and older children. The difficulty with the imitation theory is that it fails to account for the ability of even small children to form new sentences from words they know. A second theory, associated with the behavioral school of psychology, maintains that language acquisition is explained by reinforcement. Children learn to speak because their parents give them positive reinforcement when they speak correctly and negative reinforcement (correction or criticism) when they speak ungrammatically. This theory does not hold up under the findings of recent research that parents reinforce the meaning of what children say rather than its grammatical correctness. In addition, children often chatter to themselves or to no one in particular for the sheer pleasure of talking. This activity is hard to explain in terms of the reinforcement theory.
A third theory of language acquisition is called nativism. This theory holds that humans are neurologically "programmed" from birth with the capacity to acquire language as soon as their nervous system reaches a certain point of maturation. Noam Chomsky maintained that the human brain has a built-in language acquisition device, or LAD, that analyzes the parts of speech in the language that a child hears. The phases of language acquisition and the age at which children begin to acquire language are similar enough across different cultures and different languages to give some support to the nativist view.
Biological and neuroanatomical features of language acquisition
EVOLUTION AND DEVELOPMENT OF THE HUMAN VOCAL TRACT AND NERVOUS SYSTEM. Language is, as far as we know, unique to humans. Chimpanzees are able to learn a rudimentary sign language, but they cannot combine vocalized sounds into meaningful structured combinations as humans do. The human mouth and throat appear to have been modified over the course of evolutionary history for speech. The human larynx is situated low in the throat, and the sharp right-angle bend at the back of the mouth divides the human vocal tract into two resonant cavities (the mouth and the throat) that allow for the production of a large range of vowel sounds.
The maturation of certain neural circuits in a child's brain may explain why language development proceeds most rapidly in young children after the first year of life. Although babies are born with most of their nerve cells already formed, their head size, brain weight, and junctions between nerve cells (synapses) continue to increase in the first year after birth. The long-distance connections in the child's nervous system are not complete until nine months of age, and the rate of metabolism in the child's brain reaches adult levels by ten months. There appears to be a neurologically determined critical period for language acquisition. Children acquire language easily until age four, or six at the latest. After puberty, it is rare for humans to learn to speak if they have not done so earlier.
AREAS OF THE BRAIN ASSOCIATED WITH LANGUAGE. The areas of the brain that govern the interpretation and production of language were discovered in the nineteenth century by physicians studying patients with speech disorders. In 1861, Pierre Paul Broca, a French physician, was able to demonstrate from post-mortems of patients who had lost the ability to speak, that the loss of this ability is associated with damage to an area of the brain toward the front of the left hemisphere. In 1876, a German physician named Karl Wernicke found that damage to an area in the posterior part of the left temporal lobe of the brain is also associated with language disorders. This area, now called Wernicke's area, is connected to Broca's area by a group of nerve fibers called the arcuate fasciculus.
When a person reads aloud, information from the eyes travels along the optic nerve to the primary visual cortex of the brain. From the primary visual cortex, the information is transmitted to Wernicke's area, where it is interpreted. From Wernicke's area, it is carried by the arcuate fasciculus to Broca's area, then to the primary motor cortex. When a person repeats a word that is spoken, the information is carried from the nerves in the ear to the primary auditory cortex in the brain. It is then transmitted from the primary auditory cortex to Wernicke's area, then to Broca's area via the arcuate fasciculus, then to the primary motor cortex.
Stages of language acquisition
A young human's acquisition of language takes place in a series of six stages:
- Prelinguistic stage (birth to six months): The baby cries, coos, laughs, and makes other sounds.
- Babbling (six to 12 months): The baby makes nonspecific sounds from all human languages.
- One-word (holophrastic) stage (one to two years): The child speaks single words in isolation, in his or her first language.
- Two-word stage (24-30 months): The child forms two-word phrases or strings that reflect the language being acquired. The vocabulary increases; the child begins to learn words at the rate of one word every two waking hours.
- Telegraphic speech (30-36 months): Children begin to utter short phrases like telegraph messages, without formal grammatical structure.
- Fluent speech (three years and up): The child learns grammar and syntax (patterns of sentence formation) with surprising rapidity and accuracy; sentences increase in length and complexity.
Human language functions as a means of interpersonal communication, to convey thoughts, feelings, and many other forms of information. It is necessary to human social life as well as to intellectual development. Language also stimulates the expression of human creativity: poetry, drama, novels, short stories, vocal music, and similar forms of art are based on language.
Role in human health
The fact that language is unique to humans implies that language acquisition is necessary to full psychosocial as well as intellectual development. People who lose the ability to speak normally in later life because of a stroke or a condition known as primary progressive aphasia often become depressed because they feel cut off from others. Children and adolescents with dyslexia (a learning disability that affects reading and is sometimes related to problems understanding spoken language) often have additional difficulties learning to interact with others and feeling comfortable in social situations.
Studies of "wild" children and children reared by emotionally disturbed parents who did not talk to them indicate that children who do not learn to speak by age eight never achieve normal fluency. This feature of language acquisition implies that language is an important component of the social dimension of human nature. Humans who have never acquired the ability to communicate with others cannot be completely socialized.
Common diseases and disorders
Aphasia refers to the loss of a previously held ability to speak or to understand written or spoken language. Aphasia is most often the result of a stroke or head trauma, but it can occur in relation to other neurological disorders. Primary progressive aphasia is a disorder of the nervous system in which the person's ability to speak gradually deteriorates. In Broca's aphasia, caused by damage to Broca's area, the person can understand what words mean, but has trouble with speech output. Broca's aphasia is sometimes called motor or expressive aphasia. In Wernicke's aphasia, caused by damage to Wernicke's area, the person cannot understand spoken language. They can speak, but their speech is ungrammatical and incoherent. Wernicke's aphasia is sometimes called fluent or receptive aphasia.
Dyslexia is a disorder that affects the ability to read. Its symptoms may include problems with spelling, difficulty recognizing the sounds in words, problems processing visual information, and difficulty saying words quickly when asked to do so. Present dyslexia research is focused on studying the parts of the brain that process speech sounds and relate them to vision and other language areas in the brain.
Williams syndrome is a rare congenital disorder that occurs once in every 20,000 births. It results from a deletion of the genetic material on human chromosome 7 that makes a protein called elastin. Although children with Williams are usually mildly retarded, they often have normal language abilities. The dissociation of language acquisition from general intelligence in Williams syndrome suggests that human speech is not simply a byproduct of intelligence as such.
Specific language impairment (SLI)
Specific language impairment, or SLI, refers to a group of inherited syndromes in which children with normal intelligence and hearing are slow to acquire and use language. SLI is thought to affect 5-7% of children starting school. A cross-cultural study done in 1999 suggests that SLI may differ from other language disorders in that the number and specific types of problems the children had were related to their specific first language. The study showed that children learning Italian or Hebrew had fewer difficulties with verbs, for example, than children learning English.
Aphasia— The loss of previously held ability to speak or to understand written or spoken language, caused by disease or injury to the brain.
Arcuate fasciculus— A group of nerve fibers in the brain that connects Wernicke's area with Broca's area.
Broca's area— An area in the left hemisphere of the brain associated with the motor impulses necessary for speech. It is named for Pierre Paul Broca (1824-1880), a French physician.
Dyslexia— A reading disorder associated with impairment of the ability to integrate auditory and visual information, or to process sounds accurately. Holophrastic—An early stage in language acquisition in which a single word serves the function of a phrase or sentence.
Nativism— The theory that humans have neural circuits that are genetically programmed to acquire language.
Specific language impairment (SLI)— A developmental disorder of childhood characterized by significant delays in language development in the absence of deafness, autism, mental retardation, or similar handicaps.
Wernicke's area— An area in the left hemisphere of the brain that is important in the reception and interpretation of speech. Wernicke's area is connected to Broca's area by the arcuate fasciculus.
Williams syndrome— A rare congenital disorder caused by a deletion of the elastin gene on chromosome 7. Children with Williams syndrome have normal language skills even though they are usually mildly retarded.
Fletcher, P., and B. MacWhinney. The Handbook of ChildLanguage. Cambridge, MA: Blackwell Publishers, 1995.
Martin, John H., PhD. Neuroanatomy: Text and Atlas, second edition. Norwalk, CT: Appleton & Lange, 1996. Pinker, Steven. The Language Instinct. New York: Morrow, 1994.
Toppelberg, Claudio O. "Several developmental disorders and bilingualism." Journal of the American Academy of Child and Adolescent Psychiatry 38, no. 9 (September, 1999).
American Speech Language Hearing Association (ASHA).10801 Rockville Pike, Rockville, MD 20852-3279. (301) 897-5700 or (800) 638-8255. Fax: (301) 571-0457. 〈http://www.asha.org〉.
International Dyslexia Association. 8600 LaSalle Road, Chester Building, Suite 382, Baltimore, MD 21286-2044. (410) 296-0232. Fax: (410) 321-5069. 〈http://www.interdys.org〉.
National Institute of Child Health and Human Development (NICHD). National Institutes of Health, Bldg. 31, Room 2A32, Bethesda, MD 20892-2425. (301) 496-5133 or (800) 370-2943. 〈http://www.nichd.nih.gov〉.
National Institute of Neurological Disorders and Stroke (NINDS). Building 31, Room 8A06, 9000 Rockville Pike, Bethesda, MD 20892. (301) 496-5751. 〈http://www.ninds.nih.gov〉.
National Organization for Rare Disorders, Inc. (NORD) P. O. Box 8923, New Fairfield, CT 06812-8923. (203) 746-6518 or (800) 999-NORD. Fax: (203) 746-648. 〈http://www.rarediseases.org〉.
Williams Syndrome Association. P.O. Box 297, Clawson, MI 48017-0297. (248) 541-3630. Fax: (248) 541-3631. 〈http://www.williams-syndrome.org〉.
CHILD LANGUAGE ACQUISITION
Theoretical approachesSeveral approaches have been applied to child language data. Certain features of the data seem to be the result of the children imitating what they hear in adult speech (for example, some of the early attempts at sound patterns, and the acquisition of new words), but very little of grammatical structure is learned by simple imitation. This was early noticed by researchers, who pointed out that child coinages such as mouses for mice or goned for gone could not have been produced through a process of imitation (for adults do not say such things), but must represent the child's own application of abstract rules already acquired. Furthermore, direct correction and coaching have very little effect, showing the important role of the child's own efforts. Various ways of explaining this internal ability were proposed, most notably CHOMSKY'S argument that children must be credited with an innate language acquisition device: a set of outline principles about the way language is structured and a procedure for discovering the remainder. Investigators such as Piaget argued for the importance of relating the emergence of children's language to their underlying intellectual or cognitive development. Others stressed the importance of analysing the nature of the input presented to them by adult speakers. It is now apparent that each of these factors has a role to play in guiding the course of acquisition, but the nature of their interdependence is far from clear.
Stages of developmentAt a descriptive level, considerable progress has been made, especially for ENGLISH, in establishing the order of emergence of sounds, grammatical structures, and (to a lesser extent) vocabulary, and determining the psycholinguistic principles involved. The focus has been on the earliest years, including the prelinguistic period of the first year. Between birth and 12 months, several stages can be detected in a child's emerging sound-producing and perceptual abilities, beginning with a range of basic biological noises reflecting such states as hunger, pain, discomfort, and contentment (0–8 weeks), and proceeding to a stage of cooing and laughing (8–20 weeks), vocal play (20–30 weeks), babbling (25–50 weeks), and the first melodically shaped utterances (9–18 months). At around a year, first words appear, though these are not easily identified with the words of the adult lexicon, but tend to have idiosyncratic meanings and to be used as primitive sentences (holophrases). Dada, for example, said with appropriate intonation and gesture, might mean ‘There's daddy’ or ‘Where's daddy?’ or ‘Pick me up, daddy’. Moreover, the word dada might refer at this stage not only to the male parent, but also to the female parent, or to other adults, or to certain animals, or even to objects. From 12 months, an expressive vocabulary is acquired which by 18 months is usually around 50 words in size. By that time, children understand far more words than they produce: estimates suggest three or four times as many. In the next six months, expressive vocabulary approaches 200 words, and in the third year rapidly moves into the thousands. Detailed studies of the growth in vocabulary size in older children are as yet unavailable, though several studies have been made of the processes which seem to affect children's lexical progress, such as over-extension of meaning, as when dog is used for all animals, and under-extension, as when dog is used for one kind of dog only.
Pronunciation and grammarMost research time has been devoted to the emergence of PRONUNCIATION and GRAMMAR. Children do not learn all their sounds in an identical order, but seem to share certain general tendencies. Most English CONSONANTS are acquired between the ages of 2 and 4 years. Moreover, within this sequence, certain important trends have been established. For example, consonants are more likely to be first used correctly at the beginnings of words, with final consonants emerging later. Several processes of simplifying pronunciation have been identified in early speech, such as the avoidance of consonant clusters (sky pronounced without the s), the dropping of an unstressed syllable (banana pronounced as nana), or the replacement of fricative sounds such as [f] and [s] by plosive sounds such as [p] and [t]: for example, shoe as /tuː/ and fish as /pɪ/. During the second year, some children make great use of a process of REDUPLICATION, with the different syllables of a word being pronounced in the same way, as when (in one child) sister became [sisi] and mouth became [muːmuː]. Patterns of INTONATION also develop in the early years (such as the difference between stating and questioning, using the melody of the voice only), but some of the more subtle intonation patterns are still being learned as late as the teenage years, such as the difference between I THOUGHT it would rain (and it has) and I thought it would RAIN (but it hasn't).
Grammatical patterns in the early years are fairly well established for English. A stage of single-word SENTENCES appears from just before 12 months of age until 18 months, such as bye, gone, teddy, and mama. At around 18 months, children begin to put two words together, to make simple ‘telegrammatic’ sentences such as dada bye, want car, and mine lorry. Sentences increase in complexity during the third year, with more advanced features of CLAUSE structure being introduced. Clauses add extra elements, stabilizing word order, and developing a clearer subject-verb-object structure; and the hierarchical structure of a sentence develops, with phrasal complexity emerging within clauses, and ridding the sentences of their telegrammatic appearance. My daddy do kick that ball is a typical sentence for a 2-year-old. Each of the elements (subject, verb, object) appears as more than one word (a phrase), so that the sentence now has two layers of structure. By age 3, there is still greater complexity, in the form of linked sequences of clauses, using such words as and, but, cos (for ‘because’), and then.
Narratives, sometimes of great length, now make their appearance. As sentence control develops, so more attention is paid to the more subtle aspects of grammar, such as the learning of the irregular forms of nouns, verbs, pronouns, and other parts of speech. At 3, most children are making errors in the use of certain pronouns (such as me not like that mouse); by 4, most such errors have been eliminated. During the early school years there are still several aspects of English grammar to be acquired, such as the rarer irregular forms, more complex patterns of sentence connection (such as the use of although), and the use of multiple subordinate clauses. There is evidence of grammatical development right through the primary school years until, as the teenage years approach, all that is left is the learning of more subtle aspects of grammatical style and the building up of vocabulary.
Other skillsThe task of language acquistion requires more than the learning of the structural skills of sounds, grammar, and vocabulary. Children must also learn to use these structures appropriately in everyday situations. They need to develop conversational skills, the rules of politeness (such as when to say please and thank you), the correct use of FORMS OF ADDRESS, and how to make requests in a direct or indirect manner (‘I was wondering if you could …’). Older children need to be able to handle such ‘manipulating’ features of language as well, you know, and actually, to learn to decode and use more subtle interactional features (such as sarcasm), and to cope with such stylistic differences as formal and informal speech. School brings an encounter with learning to read and write, though for many children considerable awareness of written language has come from reading materials at home. Finally, children have to develop a set of metalinguistic skills (the ability to reflect on and talk about language), through the use of a range of popular, semi-technical, and technical notions, such as sound, word, page, sentence, capital letter. The task of language acquisition is complex. The fact that it is largely complete by puberty makes it one of the most remarkable (if not the most remarkable) of all learning achievements. See ANALOGY, HALLIDAY, LANGUAGE LEARNING, PSYCHOLINGUISTICS.
Language Acquisition Device
LANGUAGE ACQUISITION DEVICE
The Language Acquisition Device (LAD) is a hypothetical brain mechanism that Noam Chomsky postulated to explain human acquisition of the syntactic structure of language. This mechanism endows children with the capacity to derive the syntactic structure and rules of their native language rapidly and accurately from the impoverished input provided by adult language users. The device is comprised of a finite set of dimensions along which languages vary, which are set at different levels for different languages on the basis of language exposure. The LAD reflects Chomsky's underlying assumption that many aspects of language are universal (common to all languages and cultures) and constrained by innate core knowledge about language called Universal Grammar. This theoretical account of syntax acquisition contrasts sharply with the views of B. F. Skinner, Jean Piaget, and other cognitive and social-learning theorists who emphasize the role of experience and general knowledge and abilities in language acquisition.
See also:LANGUAGE DEVELOPMENT
Chomsky, Noam. Aspects of the Theory of Syntax. Cambridge, MA:MIT Press, 1965.