First Language Acquisition

A.Theoretical Foundation

Language is acquired, not "learned." Language is an instinct and not a learned skill like playing the piano or riding a bicycle. But how do children acquire language? There are currently three general theories of language acquisition:

·Imitation Theory

·Reinforcement Theory

·The Innateness Theory plus Active Construction of Grammar Theory

Imitation Theory

Imitation theory says that children learn grammar by memorizing the words and sentences of their language. Before attacking this view, let's make sure we recognize that language acquisition MUST involve a lot of memorizing. Children born of Mexican Spanish-speaking parents in an English speaking environment will learn English, even if they hear only Spanish from their parents. There's simply no way to get around this problem. Clearly, children must hear the words (or see the signs) of their language in order to go about committing them to their mental dictionaries, and clearly English children learn English because they are getting English input, but memorizing alone is not adequate. Here are some problems with the imitation perspective:

·Children produce many things not in the adult grammar (like 'nana' for banana), i.e. they produce things not produced by adults. Some people might say that this is simply a consequence of the difficulty of learning how to speak and not a problem for the imitation theory. Speech is a complex activity requiring great muscular coordination, and little kids are simply inept at production, but they may still be simply memorizing. Maybe, but the problems don't end here.

·Children make consistent, predictable errors that cannot be attributed to mispronunciation and which still are not ever heard in the adult grammar. Children make errors like saying "goed" instead of "went" or "drawed" instead of "drew". These errors are important. Why? Because they indicate that the child CANNOT simply be memorizing all of the words in her or his language. Adults don't make these errors! IF children are merely imitating, we have NO explanation for this. One explanation is that kids are building a grammar, not simply memorizing, and that such errors are indications that the children are applying a past tense "rule" to irregular verbs that they have not yet committed to memory as exceptions to the normal pattern. This is a good approach, but it doesn't square with imitation theory.

·Children can produce and understand novel sentences. This problem is something we've talked about all semester. It's the infinite use of finite means issue dressed up in the context of child language acquisition. If imitation is right, we'd predict that kids would not produce sentences they had not already heard. If we assume that children are constructing grammars, however, we'd EXPECT them to do this. They acquire the "rules" of their syntax and thus have a powerful device for producing novel sentences according to the general syntactic rules of their grammar. Back to the problem, then, for imitation theory. It is simply puzzling why children should have this capacity if language acquisition boils down simply to memorization of input. Kids should not be able to produce sentences not explicitly received as input.

Reinforcement Theory

The basic idea here is that children learn to speak like adults because they are taught to do so by being praised and otherwise rewarded for doing things right. At the same time, they are helped because parents "correct" them when they make mistakes. There are two major flaws in this theory.

·Strangely enough, parents actually don't seem to correct children's grammar as much as we might think, and they don't praise them for using proper adult grammatical constructions either. What parents (or other caretakers) DO seem to do is praise children for being truthful. So if a child uses a well formed sentence such as "the dog wants to eat", parents tend to correct the child is the sentence is not true, as in "No, Jimmy, the dog doesn't want to eat. It just ate." But if children are truthful but produce sentences that are ungrammatical in the adult grammar, such as "Nancy goed to school yesterday," parents often respond, "Yes, she did" without bothering to correct the incorrect "goed".

·This isn't to say that parents never attempt to correct their children's grammar. But even when they do, there is little evidence that this has any great effect on the language development of the child. Often times, children seem determined to continue to produce incorrect forms DESPITE correction from adults. And when adults insist on trying to make the child "do it right", more often that not everyone involved has a frustrating time. 

The bottom line is this. If reinforcement theory is really at the root of language acquisition, why does it seem to (a) not even be what parents do most of the time, and (b) hardly effective, if effective at all, when used for correction?
 

The Innateness Theory

This brings us to our third (and preferred) candidate. The innateness theory says that the brain of human beings isgenetically predisposed for language. Just as we are made to have two arms and are designed to walk, we are made to talk.

Language development in humans seems to exhibit these properties, some of which we'll look at a little more closely below. Briefly, let's note why.

·                     The behavior emerges before it seems necessary. Language does appear to emerge before it is necessary to the extent that we begin to develop and use it before we need it to fend for ourselves, i.e. while our every need is still being taken care of by our primary caregiver(s).

·                     Its appearance is not the result of a conscious decision. Children don't decide to start acquiring language. Language simply develops in them. Compare this to deciding whether or not to join the track team, or deciding whether or not to take an elective, or deciding whether or not to learn golf.

·                     Its emergence is not triggered by external events (though the surrounding environment must be sufficiently rich for it to develop adequately). What this means is that language doesn't emerge because adults suddenly decide that it's time for "language school" or organized "language play sessions". The only thing necessary is that kids live in a world of language. What I said in class, I think, is that we can think of it metaphorically as if we're born ready to sing and need simply to be exposed to the song.

·                     Direct teaching and intensive practice have relatively little effect. This is true. Correcting children and drilling them on grammar won't make them learn language any faster. Compare this to say, piano lessons. Without the drills and intense lessons, it is very difficult to learn to play the piano.

·                     There is a regular sequence of "milestones" as the behavior develops, and these can usually be correlated with age and other aspects of development. We'll look at this more below, but in broad strokes, this is true. Kids acquire language systematically, and cross the same basic milestones at roughly the same time regardless of the language that they are speaking.

·                     There is likely to be a critical period. This means that there is likely to be a period during which language acquisition is possible and after which language acquisition becomes highly unlikely, if not impossible. The idea is basically that there is a window of opportunity for language acquisition. This notion is generally accepted in one form or another by most linguists, though there is much debate regarding the issue. There are thought to be TWO critical periods. The first is hypothesized to last from birth to about two years old. During this time, it is hypothesized that if the child is not exposed to language at all, the child will never be able to gain "native" mastery of a language. The idea is that during the first couple of years of life, the language acquisition process has particular consequences for brain development and if the period is missed, the brain will never develop the same structures later. The second "critical period" has more to do with the issue of second language acquisition. Here, the basic idea is that after puberty, it is impossible (or nearly impossible) to learn a second language with "native" mastery. More on this in our next lesson.

B.                 Stages of language acquisition in children

In nearly all cases, children's language development follows a predictable sequence. However, there is a great deal of variation in the age at which children reach a given milestone. Furthermore, each child's development is usually characterized by gradual acquisition of particular abilities: thus "correct" use of English verbal inflection will emerge over a period of a year or more, starting from a stage where vebal inflections are always left out, and ending in a stage where they are nearly always used correctly.

There are also many different ways to characterize the developmental sequence. On the production side, one way to name the stages is as follows, focusing primarily on the unfolding of lexical and syntactic knowledge:

Stage	Typical age	Description
Babbling	6-8 months	Repetitive CV patterns
One-word stage (better one-morphemeor one-unit) or holophrastic stage	9-18 months	Single open-class words or word stems
Two-word stage	18-24 months	"mini-sentences" with simple semantic relations
Telegraphic stage or early multiword stage (better multi-morpheme)	24-30 months	"Telegraphic" sentence structures oflexical rather than functional orgrammatical morphemes
Later multiword stage	30+ months	Grammatical or functional structures emerge

Vocalizations in the first year of life

At birth, the infant vocal tract is in some ways more like that of an ape than that of an adult human. Compare the diagram of the infant vocal tract shown on the left to diagrams of adult human and ape.

In particular, the tip of the velum reaches or overlaps with the tip of the epiglottis. As the infant grows, the tract gradually reshapes itself in the adult pattern.

During the first two months of life, infant vocalizations are mainly expressions of discomfort (crying and fussing), along with sounds produced as a by-product of reflexive or vegetative actions such as coughing, sucking, swallowing and burping. There are some nonreflexive, nondistress sounds produced with a lowered velum and a closed or nearly closed mouth, giving the impression of a syllabic nasal or a nasalized vowel.

During the period from about 2-4 months, infants begin making "comfort sounds", typically in response to pleasurable interaction with a caregiver. The earliest comfort sounds may be grunts or sighs, with later versions being more vowel-like "coos". The vocal tract is held in a fixed position. Initially comfort sounds are brief and produced in isolation, but later appear in series separated by glottal stops. Laughter appears around 4 months.

During the period from 4-7 months, infants typically engage in "vocal play", manipulating pitch (to produce "squeals" and "growls"), loudness (producing "yells"), and also manipulating tract closures to produce friction noises, nasal murmurs, "raspberries" and "snorts".

At about seven months, "canonical babbling" appears: infants start to make extended sounds that are chopped up rhythmically by oral articulations into syllable-like sequences, opening and closing their jaws, lips and tongue. The range of sounds produced are heard as stop-like and glide-like. Fricatives, affricates and liquids are more rarely heard, and clusters are even rarer. Vowels tend to be low and open, at least in the beginning.

Repeated sequences are often produced, such as [bababa] or [nanana], as well as "variegated" sequences in which the characteristics of the consonant-like articulations are varied. The variegated sequences are initially rare and become more common later on.

Both vocal play and babbling are produced more often in interactions with caregivers, but infants will also produce them when they are alone.

No other animal does anything like babbling. It has often been hypothesized that vocal play and babbling have the function of "practicing" speech-like gestures, helping the infant to gain control of the motor systems involved, and to learn the acoustical consequences of different gestures.

One word (holophrastic) stage

At about ten months, infants start to utter recognizable words. Some word-like vocalizations that do not correlate well with words in the local language may consistently be used by particular infants to express particular emotional states: one infant is reported to have used to express pleasure, and another is said to have used to express "distress or discomfort". For the most part, recognizable words are used in a context that seems to involve naming: "duck" while the child hits a toy duck off the edge of the bath; "sweep" while the child sweeps with a broom; "car" while the child looks out of the living room window at cars moving on the street below; "papa" when the child hears the doorbell.

Young children often use words in ways that are too narrow or too broad: "bottle" used only for plastic bottles; "teddy" used only for a particular bear; "dog" used for lambs, cats, and cows as well as dogs; "kick" used for pushing and for wing-flapping as well as for kicking. These underextensions and overextensions develop and change over time in an individual child's usage.

Perception vs. production

Clever experiments have shown that most infants can give evidence (for instance, by gaze direction) of understanding some words at the age of 4-9 months, often even before babbling begins. In fact, the development of phonological abilities begins even earlier. Newborns can distinguish speech from non-speech, and can also distinguish among speech sounds (e.g. [t] vs. [d] or [t] vs. [k]); within a couple of months of birth, infants can distinguish speech in their native language from speech in other languages.

Early linguistic interaction with mothers, fathers and other caregivers is almost certainly important in establishing and consolidating these early abilities, long before the child is giving any indication of language abilities.

Rate of vocabulary development

In the beginning, infants add active vocabulary somewhat gradually. Here are measures of active vocabulary development in two studies. The Nelson study was based on diaries kept by mothers of all of their children's utterances, while the Fenson study is based on asking mothers to check words on a list to indicate which they think their child produces.

Milestone	Nelson 1973 (18 children)	Fenson 1993 (1,789 children)
10 words	15 months (range 13-19)	13 months (range 8-16)
50 words	20 months (range 14-24)	17 months (range 10-24)
Vocabulary at 24 months	186 words (range 28-436)	310 words (range 41-668)

There is often a spurt of vocabulary acquisition during the second year. Early words are acquired at a rate of 1-3 per week (as measured by production diaries); in many cases the rate may suddenly increase to 8-10 new words per week, after 40 or so words have been learned. However, some children show a more steady rate of acquisition during these early stages. The rate of vocabulary acquisition definitely does accelerate in the third year and beyond: a plausible estimate would be an average of 10 words a day during pre-school and elementary school years.

Perception vs. production again

Benedict (1979) asked mothers to keep a diary indicating not only what words children produced, but what words they gave evidence of understanding. Her results indicate that at the time when children were producing 10 words, they were estimated to understand 60 words; and there was an average gap of five months between the time when a child understood 50 words and the time when (s)he produced 50 words.

All of these methods (maternal diaries and checklists) probably tend to underestimate the number of words about young children actually know something, although they also may overestimate the number of words to which they attribute adult-like meanings.

Combining words: the emergence of syntax

During the second year, word combinations begin to appear. Novel combinations (where we can be sure that the result is not being treated as a single word) appear sporadically as early as 14 months. At 18 months, 11% of parents say that their child is often combining words, and 46% say that (s)he is sometimes combining words. By 25 months, almost all children are sometimes combining words, but about 20% are still not doing so "often."

Early multi-unit utterances

In some cases, early multiple-unit utterances can be seen as concatenations of individual naming actions that might just as well have occured alone: "mommy" and "hat" might be combined as "mommy hat"; "shirt" and "wet" might be combined as "shirt wet". However, these combinations tend to occur in an order that is appropriate for the language being learned:

1.                  Doggy bark

2.                  Ken water (for "Ken is drinking water")

3.                  Hit doggy

Some combinations with certain closed-class morphemes begin to occur as well: "my turn", "in there", etc. However, these are the closed-class words such as pronouns and prepositions that have semantic content in their own right that is not too different from that of open-class words. The more purely grammatical morphemes -- verbal inflections and verbal auxiliaries, nominal determiners, complementizers etc. -- are typically absent.

Since the earliest multi-unit utterances are almost always two morphemes long -- two being the first number after one! -- this period is sometimes called the "two-word stage". Quite soon, however, children begin sometimes producing utterances with more than two elements, and it is not clear that the period in which most utterances have either one or two lexical elements should really be treated as a separate stage.

In the early multi-word stage, children who are asked to repeat sentences may simply leave out the determiners, modals and verbal auxiliaries, verbal inflections, etc., and often pronouns as well. The same pattern can be seen in their own spontaneous utterances:

1.                  "I can see a cow" repeated as "See cow" (Eve at 25 months)

2.                  "The doggy will bite" repeated as "Doggy bite" (Adam at 28 months)

3.                  Kathryn no like celery (Kathryn at 22 months)

4.                  Baby doll ride truck (Allison at 22 months)

5.                  Pig say oink (Claire at 25 months)

6.                  Want lady get chocolate (Daniel at 23 months)

7.                  "Where does Daddy go?" repeated as "Daddy go?" (Daniel at 23 months)

8.                  "Car going?" to mean "Where is the car going?" (Jem at 21 months)

The pattern of leaving out most grammatical/functional morphemes is called "telegraphic", and so people also sometimes refer to the early multi-word stage as the "telegraphic stage".

Acquisition of grammatical elements and the corresponding structures

At about the age of two, children first begin to use grammatical elements. In English, this includes finite auxiliaries ("is", "was"), verbal tense and agreement affixes ("-ed" and '-s'), nominative pronouns ("I", "she"), complementizers ("that", "where"), and determiners ("the", "a"). The process is usually a somewhat gradual one, in which the more telegraphic patterns alternate with adult or adult-like forms, sometimes in adjacent utterances:

1.                  She's gone. Her gone school. (Domenico at 24 months)

2.                  He's kicking a beach ball. Her climbing up the ladder there. (Jem at 24 months).

3.                  I teasing Mummy. I'm teasing Mummy. (Holly at 24 months)

4.                  I having this. I'm having 'nana. (Olivia at 27 months).

5.                  I'm having this little one. Me'll have that. (Betty at 30 months).

6.                  Mummy haven't finished yet, has she? (Olivia at 36 months).

Over a year to a year and a half, sentences get longer, grammatical elements are less often omitted and less often inserted incorrectly, and multiple-clause sentences become commoner.

Perception vs. production again

Several studies have shown that children who regularly omit grammatical elements in their speech, nevertheless expect these elements in what they hear from adults, in the sense that their sentence comprehension suffers if the grammatical elements are missing or absent.

Progress backwards

Often morphological inflections include a regular case ("walk/walked", "open/opened") and some irregular or exceptional cases ("go/went", "throw/threw", "hold/held"). In the beginning, such words will be used in their root form. As inflections first start being added, both regular and irregular patterns are found. At a certain point, it is common for children to over-generalize the regular case, producing forms like "bringed", "goed"; "foots", "mouses", etc. At this stage, the child's speech may actually become less correct by adult standards than it was earlier, because of over-regularization.

This over-regularization, like most other aspects of children's developing grammar, is typically resistant to correction: