Language Acquisition

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:

1. 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.
2. 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.
3. 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.
4. 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.