BMN ANGD A2 Linguistic Theory
Lecture 12: Language Acquisition 1
What children do and what they don’t do
1
Introduction
To end this series of lectures I will give a double lecture on the theme of language
acquisition, the first part will concentrate on what we can observe happening as children go
through the process and next week we will take a tour through various theories which have
attempted to account for not only these observations but also for the possibility of language
acquisition in general.
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Some Common Misconceptions
It is commonly thought that parents teach their children how to speak their language and that
this accounts for why children do. But a few basic observations are enough to completely
dispel this myth. First all children learn language very well: virtually every one of them
completes this task perfectly with very little visible sign of effort. Second, parents, and adults
in general, do not make good language teachers: they are mostly not trained to perform this
task, and most adults do not make naturally good teachers without some training, and they all
have virtually no knowledge of the subject they would be required to teach. Human
knowledge of language, as anyone who has tried to study it knows, is simply not accessible to
conscious consideration. How could anyone teach something that they have no conscious
knowledge of? These two points put together show that language learning is something
children do despite whatever their parents do rather than because of it.
But this is hard for some to accept. It is obvious, they argue, that parents have some role in
the acquisition process as it is the parent’s language which determines the child’s language: a
child of Chinese speaking parents will grow up speaking Chinese, providing that is the
language that the parents speak to the child. But this only demonstrates that the parents
merely provide the necessary conditions for the child to learn a language, not that they play
any active role in the process at all.
More stubborn proponents of the idea that parents have a direct role in their children’s
language acquisition might point to the fact that children often make ‘errors’ during the time
they are learning their language, as evidenced by the fact that child language is not the same
as adult language for some period of time. One would not need conscious knowledge of the
grammatical system to play a role in its acquisition by recognising the child’s errors and
correcting them.
There are a number of criticisms of this point of view, however, that make it not half as
attractive as it at first sounds. First, although the differences between child and adult language
indicate that children go through a process of language learning, where they clearly entertain
a number of different grammatical systems before eventually settling on the correct adult one,
they do not necessarily indicate ‘errors’ in the way that is meant. Typically, the language that
children produce is perfectly consistent and as rule governed as any other language.
Presumably this is because they are operating with a working grammar of their own which
differs from the adult one. Over time they abandon these grammars and move on to others,
eventually settling on the correct adult one. But to say that the sentences that they produce at
earlier stages are ‘errors’ is like saying that a Hungarian sentence is an error to someone who
speaks English. Still, something makes a child abandon early grammars to eventually arrive
Mark Newson
at the adult one. But for adult correction to play a role in this it would be necessary for the
child to realise that what they said was an error and furthermore that what the parent responds
is meant to be taken as a correction of this error. While this may be logically possible, despite
the fact that it perhaps attributes to very young children powers of deduction that they
typically do not demonstrate in other areas, it is highly unlikely that it is practically possible.
For such corrective behaviour on the part of the parent to have any positive effect on the
child’s linguistic development, it should at least be consistent. Thus, whenever a child utters
something that is inconsistent with the adult grammar, the parent should immediately respond
with the relevant correction (just how the child can work out from the behaviour of the parent
what exactly is wrong with their own grammar and how to change this so it approaches the
adult grammar is of course rarely elaborated on by the proponents of the idea that parents
teach their children language by correction). Unfortunately, studies of the behaviour of
parents have shown that this behaviour is quite rare, let alone consistent. Although, parents
may feel that they correct their children’s grammatical errors, in fact they rarely do so. A
study by Brown and Hanlon (1970) showed that parents are far more likely to correct their
children’s factual errors than their grammatical ones. This is hardly surprising. For example,
if a child were to utter ‘daddy gone’ when in fact daddy had just crawled under the table to
retrieve the item of cutlery the child had thrown down (an all too common event as anyone
with children will testify), the mother is hardly likely to correct the child by saying ‘no,
daddy HAS gone’ as this would only serve to confuse the poor child the moment the father
re-emerges from under the table, spoon in hand.
More anecdotal evidence also seems to demonstrate that children are impervious to
grammatical correction, even on those few occasions when it actually happens. There are
numerous instances in the language acquisition literature of hapless parents repeating their
own version of the child’s utterance, eliciting only a repetition of the child’s original version
in response. This is probably another reason why parents do not do it. It appears to have no
effect whatsoever on the behaviour of the child – parents are human after all, and humans, as
we know are very good learners. It would not take too many occurrences of the pointless
exercise of trying to get a child to mimic adult language and failing spectacularly for the adult
to give up and go and do something far more worthwhile.
Finally, consider the fact that adults differ from each other. Some are talkative, some are not.
Some interact with children well, some not so well. Indeed, different cultures expect different
behaviours from adults when interacting with children, encouraging more or less of it to take
place. Yet child language acquisition is a universal phenomena and one which shows
remarkably little difference from one culture to another and from one individual to another. If
adult behaviour had such a major role to play in the acquisition process, one would expect
there to be relatively few similarities in the results of the process let alone in the course of the
process itself. It is worth repeating, children learn their language despite what their parents do
rather than because of it.
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What Children Do Do
Virtually all children make vocal noises from birth. But it is not easy to determine when
making noises stops and speaking language starts. Fairly quickly babies start to make noises
that can’t be simply attributed to physical reflexes, such as hiccoughing or burping, or direct
responses to physical or mental discomfort, such as crying. These noises are often termed
‘babble’ and although they are clearly not language, they appear to be universal and so some
have supposed them to be part of the process of language acquisition.
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Language Acquisition – What children do and what they don’t do
What role babble plays in language acquisition is not at all clear, however. It doesn’t appear
to be essential, as babies that have to have medical procedures to help them breath but which
effectively prevents them from making vocal noises during the period when babies normally
start babbling, seem to acquire language perfectly well enough after the procedure is
reversed. Neither does it seem to be a response to linguistic signals around the child: deaf
babies babble without having heard adult language. The idea that babbling is the child
practising language sounds seems far too simple and although there have been claims that the
initial period of babbling contains language sounds from all possible languages and that it
reduces to those found in the child’s home language, it is difficult to corroborate this for the
simple fact that the child’s vocal tract is developing at this time and hence it is not easy to
map the sounds babies make onto the sounds used in adult language.
Babbling does, however, undergo development. The first stage involves the child making
random noises similar to CV sequences. However, from about 25 weeks after birth, an
element of repetition comes to be a feature of babbling and certain CV sequences may be
repeated, such as ‘babababa’ or ‘dididididi’. This behaviour is known as reduplicative
babbling. Some time after this, more variation appears in the babbling, both in terms of the
CV sequences used and in the pitch contour of stream of babble. This is called jargon and
some have taken this to be the child’s attempt to produce language sounding strings prelinguistically, though it is of course difficult to know exactly what children think they are
doing when they do this.
From about one year, children start to use sounds meaningfully, usually starting with single
words, though what a child’s ‘word’ corresponds to in adult speech is not always a single
word – my own daughter had a ‘word’ dootagen which clearly corresponded phonetically and
semantically to the English phrase ‘do it again’. Moreover, children use these one word
utterances as complete communications and so they correspond to what would be a whole
sentence in adult language. Of course, when a child says ‘ball’ and points to a ball, it does not
make much sense to say that what the child is saying is ‘I want the ball’, even if it is true that
they do want the ball. That would be like attributing to the child an adult linguistic system
which was somehow being filtered to produce more limited sentences. Besides, it is rather
dangerous to assume exactly what single word utterances mean: ‘ball’ could be taken to mean
‘look, there’s a ball’, ‘that’s a ball’, ‘the ball is over there’, ‘I like that ball’, ‘that ball reminds
me of a dream I had last night’, etc.
Obviously at the one word stage of development, we cannot talk much of syntactic
development. There are no distributional patterns to distinguish between word categories as
in one word utterances all words have the same distribution. Furthermore, at this stage there
is also no use of productive morphology. Although children may use words which are
different categories in adult language, there is, then, no evidence that they have different
statuses in the child’s system. During this stage, the number of words the child uses gradually
increases, with no real patterns emerging.
At about the age of one and a half, however, drastic developments take place. First there is a
vocabulary explosion and the child seems to have access to many more words. Then at
roughly the same time sentences with more than one word in them appear. From early on,
there is evidence that children have learned basic aspects of the target adult grammar. For
example, word order in two and three word utterances show similar patterns to equivalent
adult sentences: ‘daddy go’ rather than ‘go daddy’, for example. Again, we need to be careful
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of interpreting child utterances. Is ‘mummy sock’ to be taken as ‘mummy has a sock’ or
‘mummy’s sock’, for example? In this particular case, it is hard to determine what the child
intends, but note that either way the word order is still the same as the adult version.
As multiword sentences do allow for syntactic positions to be identified, it is possible to
determine that children at this stage use different words differently and thus they have
established the foundations of word categories. Use of nouns and verbs, though perhaps not
identical to the adult’s, is quite easy to recognise. The remarkable thing about language at this
stage, however, is its lack of functional words, such as determiners, auxiliaries and
complementisers, as well as inflections for tense etc. Language used at this stage is often
described as ‘telegraphic’ as it shows similarities to that used in telegrams where the ‘small
words’ were often omitted for economic reasons – in a telegram, you paid per character! Also
lacking at this point is much variation in sentence type. Obviously there is not much you can
do with a two word sentence for variation, but even with three and four word utterances, used
a little later at this stage, children seem to stick to the same basic patterns: SVO, or whatever
the basic order of the target adult language is. Essentially this means that a good proportion
of the syntax is missing. For example, most of what is handled by transformations in a
transformational grammar would be inapplicable to telegraphic speech.
Again, like in the one word stage, there is gradual development from two to three and four
word sentences. But once the child reaches about two and a half, there is once again rapid
development. This time new vocabulary items are of the functional categories and these are
accompanied by a sudden expansion in sentence type used. This is often called the syntax
spurt. Of course, not everything comes ‘on line’ at this point and there is development in the
period after the syntax spurt. By the time the child is five, however, the vast majority of their
language is in place and there are only superficial aspects which develop after this,
sometimes until around puberty.
The basic pattern of development described above is fairly uniform both within and across
linguistic groups. There are individual differences, but the majority of children enter these
stages within about four months of each other. Thus it is fairly common to see dates of
significant development stated as an age plus or minus two months, e.g. the syntax spurt takes
place at 2;6 (±0;2). Moreover the order of development within a developmental stage may
vary from one individual to another, but the general progress from stage to stage is
remarkably uniform.
4
What is going on inside their heads?
It is clear that language acquisition involves the learning of grammars rather than languages:
children learn grammatical rules, not sentences. One early but convincing demonstration of
this came from an experiment which showed children a stylised cartoon drawing of a creature
which was introduces as a wug (Berko 1958). The children were then shown a drawing with
two of the creatures and asked what they were and the invariably got the answer []
showing that they could apply the English plural morphophonemic rule to words that they
had never been introduced to before.
Another demonstration that what children learn are grammatical rules rather than linguistic
phenomena comes from early child pronunciation. It is well known that children often
pronounce words in ways which differ from the adult pronunciation, such as pronouncing the
word ‘puddle’ as puggle. It is commonly believed that this shows a lack of control over the
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Language Acquisition – What children do and what they don’t do
vocal tract by the child or a failure to learn the sounds of the language. However, Smith
(1973) demonstrated that this cannot be so. He observed that children who produce puggle
for ‘puddle’ also produce puddle for ‘puzzle’, demonstrating that the child is perfectly
capable of producing the relevant sound combinations. Smith then showed that the
pronunciation of the child is related to that of the adult via regular phonological rules,
seeming to imply that children have the same underlying form for words as adults, but
produce pronunciations by phonological rules systems that differ from the adult’s grammar.
This is also supported by so called ‘fis’ phenomena, in which children are unwilling to accept
an adult copying their own pronunciation of a word: the child says “there’s a fis” (pointing to
a fish) and the adult replies, “where’s a fis?”. The child then corrects the adult “not fis, FIS!”
Clearly the child knows what the pronunciation of the word is, presumably because this is
what they have as the underlying form. But then this underlying form undergoes some
modification in expression, showing that there is a rules system underlying pronunciation.
However, this fact raises a serious problem. How is it possible for a child to figure out the
grammar of the target language just from hearing it spoken around them. Recall that parents
do not teach their child the grammar, or even present the language itself in a particularly
learner friendly way. For example, the child is not presented with consistent information
about what is not possible in the language via corrections etc. This actually puts the child in a
worse position than the linguist. At least the linguist can ask native speakers for consistent
observations about what is grammatical and what is not. One only has to look at the
performance of linguists in coming up with the correct grammar for a language to see just
how difficult the task is. The problem is, of course, the one that Chomsky recognised in his
earliest work: there are an infinite number of compatible grammars with any set of linguistic
data and it is not just simply a matter of coming up with one that predicts which sentences are
grammatical in a language, but doing it so that they are deemed grammatical in the right way,
with the right structural analysis, etc.
There are in fact more serious problems still. It seems from our studies of language that the
kinds of grammars that human language is generated by are rather abstract, making use of
abstract elements, such as empty categories, involving complex relationships, such as binding
relationships to determine the reference of pronouns, and grammatical mechanisms such as
transformations. Linguists have discovered these things, somewhat imperfectly, after many
years of collaborative work and rational argumentation and with ready access to whatever
data they have seen the need for. If linguists were to operate under the conditions facing the
child, progress would be impossible. Yet, progress is indeed possible for the child. The
question is how? This is known as the poverty of the stimulus argument and it is often quite
misunderstood by those who would rather not go where the argument obviously takes us.
Chomsky is often cited as claiming that language cannot possibly be learned from data alone
because the linguistic data is so full of errors – speakers of a language make mistakes in their
speech as a common occurrence and so such errors will undoubtedly be part of what children
hear. But this is a separate issue from the poverty of the stimulus argument, which claims that
the linguistic data alone does not contain enough information to be able to reconstruct
grammars from. That the data also may include misleading or confusing material adds to the
problems facing the child. But if it turns out that this is not too big a problem, for example
because parents are more careful in their speech directed towards children, this does not mean
that the poverty of the stimulus argument is solved, as some seem to think.
In the end, it has to be admitted that children formulate complex and abstract grammars on
the basis of limited data and they do it in around five years with apparently little effort and
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Mark Newson
virtually no help from adults. Moreover, at the same time they are undergoing many other
significant cognitive and social developments, a point which is often made, but which seems
rarely to lead to the appropriate conclusion. This fact complicates the task of language
acquisition rather than simplifies it. Again, compare the situation to linguists: most of these
have fully developed cognitive and social skills and yet they still struggle to come up with
acceptable theories.
Next week we will discuss the conclusions that can be drawn from these observations, but for
now we are concentrating on what children actually do rather than on theories that try to
account for this.
5
The formal modelling of language acquisition
During the 1960s when Chomsky’s approach to language sparked interest in properties of
formal languages, such as context free or context sensitive languages, there was also some
interest in the question of the development of a formal approach to language acquisition. We
need not go into the technicalities of this kind of work to appreciate its methods and some of
its important conclusions.
Formal language learning theory started by formalising the conditions under which language
acquisition can take place. This included making assumptions about the learner, the learning
process or algorithm, the learning situation and the definition of what counted as successful
learning.
5.1
The learner and the learning situation
While we know that in actual fact real children learn grammars not languages, formal
learning theory started with the simpler goal of recognising languages from given data, rather
than deducing the grammar which generates the language. Thus, the learning situation could
be described as there being a selected target language taken from a range of languages, say
the set of context free languages, and this is used to form a subset which will count as the
data presented to the learner. The data will be presented one at a time and after each
presented datum, the learner makes a guess at the target language. The next datum is
presented and the learner makes another guess. This process continues forever.
Obviously this has some aspects to it which are not completely compatible with real child
language learning. There seems to be a natural time limit placed on children that they acquire
their languages in about five years. They do not take an infinite amount of time to do it. But
these differences only serve to make the learning situation more simple that that which
actually faces the child, and so results about what cannot be learned under these more
generous assumptions should pass over to the real learning situation too.
There are other ways in which this formal account of the learning situation is rather similar to
the real one. For example, note that only positive data is given to the learner: that is sentences
from the target language. Ungrammatical sentences are not presented. As we have seen, it
seems that real children learn mostly from positive evidence and are either not presented with
easy negative evidence or are resistant to it if they are. If we allowed negative evidence to be
presented to the formal learner, again this would simplify the situation and make learning
easier. We will see that one of the most important results from this work demonstrates the
difficulties of working with positive data alone.
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Language Acquisition – What children do and what they don’t do
5.2
the learning strategy
The learning strategy assumed in formal learning theory is a simple one, but one which also
has connections to the real situation. As we have seen, the learner is presented with data one
at a time and makes a guess at the target language compatible with the data presented.
Learning is assumed to be conservative. This means that having made a guess at the target
language, the learner will stick with that guess until such times as they receive evidence that
the guess is wrong. Given the learning situation this means that they are presented with a
sentence from the target language which is not a sentence of the hypothesised language. Once
the hypothesised language is shown to be an error, the learner can change the hypothesis to a
language which is compatible with the data presented up to that date. In this way learning
proceeds towards the correct language.
Again, this does mirror certain aspects of real language learning. Children clearly entertain
hypotheses about the language they are learning and these are abandoned as the child
progresses in the learning task. It is difficult to think of why a child would abandon an earlier
grammar for another one unless there is a reason to do so. Thus it seems reasonable to assume
that children are conservative learners and not ones which leap wildly between guesses at
whim.
5.3
conditions of learning
As I said, the learning situation is such that data presentation goes on forever. This may strike
you as a little unnatural. However it is intended to model an actual aspect of language
learning, that no one tells the child when they have correctly learned their language.
Similarly, there is no point at which the learner in the formal learning situation is informed
that they have been successful and so the learning process has no end point.
So how do we know that learning is successful? The criteria for successful learning is that the
learner identify the correct language at some finite times and then never abandons this
hypothesis at any future time. Thus learning fails if the correct language is never
hypothesised or if the correct language is hypothesised but then abandoned in favour of some
other hypothesis.
We can see the importance of conservative learning on the basis of positive evidence from
this perspective. Once the correct language has been hypothesised, every piece of positive
data presented to the learner will be compatible with the hypothesis and hence the learner
should never abandon this hypothesis.
5.4
Gold’s results
One of the most important pieces of work to follow from the above assumptions was Gold
(1967). Gold considered the learning conditions outlined above with respect to different types
of formal languages. His conclusion was that as long as only positive data is available to the
learner, only finitely large languages are learnable. All context free, context sensitive and
languages generated by unrestricted rewrite systems, of which transformational grammar fall
into, are not learnable under these conditions.
The result follows from what we might refer to as the subset problem. Suppose two languages
are in a subset relationship to each other, such that all the sentences of one are in the other but
not vice versa. The problem is that if the learner hypothesises the larger language but the
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Mark Newson
subset language is the target, every piece of positive evidence from the target language will
be compatible with the wrongly hypothesised one. Thus the learner will never reject the
wrong hypothesis and learning will fail.
As I said earlier, because this learning model makes learning easier than the situation facing
children, any negative result for the model passes over to the real learning situation. What can
we conclude therefore? There are a number of possibilities. Obviously human languages are
not finite and so it would not be possible to solve the problem by assuming that the languages
that children learn are not in the sets that Gold showed to be unlearnable. Another possibility
then is to assume that children in fact do have access to negative evidence which would help
solve the subset problem by enabling the learner to reject wrongly hypothesised superset
languages. However, although it is possible that children are able to make use of some
negative evidence in their acquisition of language, this is clearly problematic from all that we
have discussed above. Assuming a non-conservative learning strategy might help solve the
subset problem, but this would create larger problems elsewhere and so this would not be a
viable solution overall. Finally, it is possible that the problem can be solved by assuming that
the set of languages that the child has available to select from is not equivalent to a whole
formally defined set, such as the context free languages. Instead, if the set of possible human
languages were a more restricted subset of some set of formal languages, the subset problem
can be solved. This would amount to claiming that human languages are limited in a way
compatible with what Chomsky has been claiming since the earliest days of transformational
grammar.
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Conclusion
The great mystery of language acquisition is the fact that children do it, despite all the
apparent odds against them. The task is undeniably hard, the data they have to work with far
from ideal and the situation under which it takes place is complicated by many other factors.
And yet they do it – seemingly with little effort, without very much support and in an
amazingly short amount of time. From the child’s perspective, this seems to be a simple fact
of development. From the adult perspective it is a miracle almost beyond explanation. We
will review a number of possible explanations that have been proposed next week, but it is
important in evaluating these theories to bare in mind the task that faces the child and the
ease with which they tackle it. This obviously poses a challenge for any theory.
References
Berko, Jean, 1958 ‘The Child's Learning of English Morphology’ Word, 14, 150-177.
Berko, Jean and Roger Brown 1960 ‘Psycholinguistic Research Methods’ in P. Mussen.
Handbook of Research methods in Child Development. New York: John Wiley.
pp. 517–557.
Brown, R. and C. Hanlon, 1970 ‘Derivational complexity and order of acquisition in child
speech’ in J. R. Hayes (Ed.) Cognition and the development of language, 11-54, New
York: Wiley.
Gold, E. M. 1967 ‘Language identification in the limit’ in Information and Control, 10, 447–
474.
Smith, Neil, 1973 The acquisition of phonology: A case study Cambridge: Cambridge
University Press.
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