Language Learning for ChildrenÂ

Language acquisition is the study of the processes through which learners acquire language. By itself, language acquisition refers to first language acquisition, which studies infants' acquisition of their native language, whereas second language acquisition deals with acquisition of additional languages in both children and adults.

One hotly debated issue is whether the biological contribution includes capacities specific to language acquisition, often referred to as universal grammar. For fifty years, linguists Noam Chomsky and the late Eric Lenneberg have argued for the hypothesis that children have innate, language-specific abilities that facilitate and constrain language learning.

Other researchers, including Elizabeth Bates, Catherine Snow, Brian MacWhinney, and Michael Tomasello, have hypothesized that language learning results from general cognitive abilities and the interaction between learners and their surrounding communities. Recent work by William O'Grady proposes that complex syntactic phenomena result from an efficiency-driven, linear computational system. O'Grady describes his work as "nativism without Universal Grammar."

One of the most important advances in the study of language acquisition was the creation of the CHILDES database by Brian MacWhinney and Catherine Snow.


Nativist theories hold that children are born with an innate propensity for language acquisition, and that this ability makes the task of learning a first language easier than it would otherwise be. These "hidden assumptions" allow children to quickly figure out what is and isn't possible in the grammar of their native language, and allow them to master that grammar by the age of three. Nativists view language as a fundamental part of the human genome, as the trait that makes humans human, and its acquisition as a natural part of maturation. They believe that children learning language are as natural and normal as dolphins learning to swim or songbirds learning to sing.

The possible existence of a critical period for language acquisition is another nativist argument. Critical periods are time frames during which environmental exposure is needed to stimulate an innate trait. Young chaffinches, for example, must hear the song of an adult chaffinch before reaching maturity, or else would never be able to sing. Nativists argue that if a critical period for language acquisition exists , then language acquisition must be spurred on by the unfolding of the genome during maturation. Much research on the critical age period or window of opportunity Linguist Eric Lenneberg stated, in a 1964 paper, that a critical period of language acquisition ends around the age of 12 years. He claimed that if no language is learned before then (see Feral children), it could never be learned in a normal and fully functional sense. This was called the "Critical period hypothesis." However, the opponents of the critical period hypothesis say that in this example the child is hardly growing up in a nurturing environment, and that the lack of language acquisition in later life may be due to the results of a generally abusive environment rather than being specifically due to a lack of exposure to language.

The critical period hypothesis of brain plasticity and learning capacity has been called into question. Other factors may account for differences in adult and child language learning. Children’s apparently effortless and rapid language acquisition may be explained by the fact that the environment is set up to engage them in frequent and optimal learning opportunities. By contrast, adults seem to have an initial advantage in their learning of vocabulary and syntax, but may never achieve native-like pronunciation.[4] A more up-to-date view of the Critical Period Hypothesis is represented by the University of Maryland, College Park instructor Robert DeKeyser. DeKeyser argues that although it is true that there is a critical period, this does not mean that adults cannot learn a second language perfectly, at least on the syntactic level. DeKeyser talks about the role of language aptitude as opposed to the critical period.

LEARNING ABOUT THE MEANING OF WORDS
Parents impatiently await their infant's first words and regard this as one of the most exciting milestones in development. Whereas in Chapter 3 we considered speech perception in terms of units of sounds, in this chapter we are concerned with the acquisition of words as symbolic and meaningful: the emergence of the in fant's first productions and the development of the lexicon (the words that form a language). The very earliest stage of vocal output between two and three months is referred to as cooing (vocalizations that are interactional but nonlinguistic). The baby is learning to create sounds at varying pitches and exploring what her voice can do. Between four and six months, the variety of vocalizations she makes increases significantly. The infant now produces raspberry noises, interrupted by vowel-like sounds. This clumsy transition between vowel and consonant-type utterances is called marginal babbling. At first, infants may produce sounds outside those in her native tongue that may belong to a variety of world languages. With time, however, the sounds that she does not hear often are produced increasingly rarely.
From about seven months onward, vowel-consonant transitions become smoother. Productions now take the form of repeated syllabic strings such as "da-da-da-da." This stage is referred to as canonical babbling, and toward the end of the first year it becomes quite complex, involving variegated sequences such as "babi-babi," "biba-biba." Research into the structure of babbling suggests that it is not until about ten months of age, when speech processing is becoming increasingly specialized, that the child's native tongue begins to affect the kinds of sounds the baby utters.
Some time around the beginning of the second year, babbling and word production tend to coexist in the infant's vocal repertoire: each features similar syllables, intonation, and timing. It can be rather difficult, then, to distinguish early words from complex canonical babbles. When do the repeated syllables "ma-ma-ma" become a symbol for "mother"? Is the utterance "ahhr" still merely a babble if the baby is pointing to a car at the same time, or is it the child's idiosyncratic yet consistent sound for "car" that now has real referential status? Even experienced researchers can, at times, find it difficult to determine the nature of these sounds, because the transition from canonical babbling to first words is neither clear-cut nor abrupt. Well before uttering her first word, the infant has been busy segmenting the incoming speech stream at word boundaries. As adults we take this ability for granted. In fact, it is no easy task, because the acoustic signal itself does not provide obvious clues as to where one word ends and the next begins. In spoken language, unlike written language, there are no helpful, consistent gaps between words. But early on in language development the infant discovers the phonotactics of her language and learns which sound combinations are legal and which are not. As we saw, she is also particularly sensitive to stress patterns. Such clues help the infant learn to segment the stream of sounds into separate words. They also assist her in recognizing the presence of the same word when it appears in different linguistic contexts, or when it is pronounced by different speakers, both of which dramatically alter the acoustic signal of individual words.
Although segmentation is vital for preparing the infant for speech, learning the lexicon of one's language involves far more than simply distinguishing word boundaries. What is a "word" anyway? If you try to define this term, you will see just how difficult it is. The Oxford English Dictionary defines a "word" as "a sound or combination of sounds forming a meaningful element of speech." But this is inadequate because words also break down into even smaller
is units of meaning known as morphemes. These include parts of words such as "ed," which conveys past tense ("walked," "painted;' "cleaned") or "et.," which conveys the concept of agent ("butcher," "dancer;' "teacher"). Although morphemes convey meaning, they are not referential in isolation: they have to be attached to the stem of a word. A word, on the other hand, can on its own refer to or symbolize an object, action, event, person, abstract thought, and so forth. So how does the infant learn that words are actually meaningful, referential symbols? There are few clues in the words themselves (apart from onomatopoeic words such as "sizzle:' "crack," or "moo"). On the whole, however, the sounds that form individual words are completely arbitrary. For instance, why is the sound "car" used to represent a type of vehicle? A car could just as easily have been called a "bip" or a "toma." Indeed, across different languages the speech sounds chosen to represent the same meaning are completely different ("car" becomes "voiture" in French, for instance, or "coche" in Spanish). None of these sounds convey the shape, purpose, or even the sound of a car.
Not only are words arbitrary, they are also conventional. By this we mean that people learning English accept that "car" refers to that kind of vehicle, rather than each person choosing his own word to represent this meaning. We would find it very difficult to communicate with one another if we did not have such a tacit agreement with respect to the convention of naming. Over time, some words may be altered by slang, replaced by new ones, or even borrowed from other languages. But such changes are only accepted as part of a language when enough people adopt them.
Having considered the arbitrariness and the conventionality of words, we can see that in order to build up her receptive lexicon, an infant needs to recognize that a word like "car" refers to the whole category car, not simply to an individual car. To determine the correct meaning of words, infants must use clues other than the sounds of which the words are composed. For adults, this is a relatively easy task. But the prelinguistic infant cannot ask for definitions, examples, or clarifications. If you point to a picture of a brown dog in a book and say to the infant: "DOG! That's a DOG," how is she to know that you are referring to the four-legged animal on the page, rather than, perhaps, the page, the entire book, or the finger you are using to point? Even if her attention is correctly drawn to the dog itself, how does she come to realize that it is the animal as a whole that the word "dog" refers to, and not its tail, its furry coat, its long ears, or the fact that it is standing? Pointing alone is clearly too vague to convey the precise meaning of a new word. And there are no phonetic clues to meaning either. Even if, in this case, the toddler successfully learns that the word "dog" refers to the canine in the picture, how does she then come to know that the same sound refers to the whole category dog including pictures of other dogs and real dogs walking past her in the street? Furthermore, once she has learned the meaning of the new word spoken by others, what is the process that allows her to produce the sequence of sounds that makes up the word "d-o-g"? All of these steps must be taken into consideration if we are to understand how infants progress from early speech perception to understanding and producing words themselves.


In order to begin building up her vocabulary, however, the toddler has to rely almost completely on the speech she hears. Here, the input model is crucial, whatever the cultural or socioeconomic environments. But what precisely is it about parental speech input that facilitates or hampers word learning? Caregivers who tailor their infant-directed speech by emphasizing intonation and stress, and by repeating words, make language more salient to the young listener. But it is both the way words are delivered as well as the content of adult speech that are important.

Overall, the general pattern of language development is relatively similar across children. Though most of the research has centered on English and other Western languages, the cross-cultural work that has been carried out suggests that most children go through roughly the same sequence of stages on their way to becoming fluent speakers. While the sequence may be similar, however, individual rates of language development vary considerably. This is particularly true for word learning. There is considerable variation in the size and content of children's lexicons, not only from child to child, but also between the sexes. It is therefore important to take account of the influences--both biological, environmental, and sociocultural--that directly and indirectly contribute to individual differences in language production. Research has shown that girls tend to produce language earlier than boys. This turns out to be a biological influence. Extensive investigation into the linguistic environments of infants has revealed that this gender difference is not a result of linguistic experience. Studies of Western cultures show that parents talk as much and in a similar way to baby girls as they do to baby boys. It is thought, therefore, that differences between the sexes must be due to certain physiological factors that result in girls' brains maturing somewhat faster than boys. As a result, girls are able to gain control over their articulatory apparatus slightly earlier than boys. A further biological influence is suggested by the link that has been found to exist between maternal verbal intelligence (also referred to as verbal IQ) and infant language production. Verbal IQ refers to the mother's score on items of standardized intelligence tests that measure her language abilities as compared to those that measure her spatial and numerical reasoning. The children of mothers with high verbal IQ tend to display more advanced language skills than do children of mothers with lower verbal IQ. This finding has been further corroborated by studies of language development in adopted children. Robert Plomin and his collaborators have shown that child vocabulary competence is not simply related to adoptive mothers' verbal behavior (an environmental influence), but is also correlated with biological mothers' intelligence (a genetic effect). General biophysiological factors, such as genetic make-up, can therefore clearly affect language development even at the level of word production. Researchers have identified the presence of a number of general, nonlinguistic influences that play an indirect, although significant, role in word learning. Rather than being specific to language development, these general factors affect the overall environment within which the child grows. Maternal socioeconomic status (SES) is one such factor. In Western societies, mothers of high SES have been shown to address their children more frequently, and with a greater variety of words in longer utterances, than those of lower SES. Other parental characteristics such as education, social competence, knowledge of child development, and attitudes toward parenting can also contribute to the way that parents interact with their infants, thereby affecting the contexts within which words are acquired. In terms of more direct influences, the role of parental input (the actual speech that the child hears on a day-to-day basis) has been shown to be an important influence on word learning. Specifically, the language that the child experiences affects the onset and progress of word production. By contrast, as we saw in the last chapter, linguistic input does not seem to have a significant impact on the onset of babbling. Because the infant never hears babbling, she has no model to copy. So all infants tend to enter the canonical babbling stage at around seven months, regardless of how much or how little verbal stimulus they receive.

In their studies of American families, developmental psycho-linguists Letitia Naigles and Erika Hoff-Ginsberg have shown that when children acquire new verbs, for instance, the frequency with which each verb occurs in parental input has the greatest effect on speed of acquisition of that verb. Interestingly, verb acquisition is also affected by the position of the target word within parents' utterances. When verbs regularly appear at the end of speech segments, as in questions like, "where's Daddy going?" they are actually easier for infants to learn than when they appear at the start of sentences or mid-sentence, such as "Daddy's going to work." A second factor that contributes to the rate at which a verb is acquired is the diversity of grammatical structures in which the verb appears. So it is beneficial for the toddler to hear the same verb used in a number of different ways: in questions, in commands, in exclamations, or in declarative statements. In each case, the verb will be surrounded by different types of words, and the word order, as well as intonation and stress patterns, will vary. The verb itself will take different forms according to tense ("run," "ran," "running") and / or person ("I run," "she runs"). All of these factors make the verb more noticeable, encouraging the child to try to understand its meanings. The effects of linguistie likce contexts also hold for the learning of nouns, adjectives, and the Even when parents are supplying such supportive models, clearly the child's own capacities for processing linguistic input and discov- ering meaning and structure continue to play a crucial role. This is exemplified by the cross-cultural work of Eleanor Ochs, Bambi Schieffelin, and Shirley Heath. These researchers have shown that in some cultures the simplified register of child-directed speech is not used, so it cannot be essential to language acquisition. But of course such children do participate in the everyday activities of their opment. culture, which provide a basis for socialization and language devel In sum, even though infants do not understand everything in the speech that they hear during the first eighteen to twenty-four months, what parents actually say to them, and how they say it, can affect the nature of their subsequent word production. The variety of words used, the manner in which they are presented, and how often a child is addressed and drawn into speech-based interaction may all influence individual differences in word learning rates.