BMN ANGD A2 Linguistic Theory
Lecture 13: Language Acquisition 2
Theories of Language Acquisition
1
Introduction
There are very few ancient theories of language acquisition per se. Probably it is such a
natural fact about humans that it didn’t come across as anything worth questioning. The
Greeks did debate over whether words were in language were a natural ‘god-given’ aspect of
the bits of the universe they refer to or whether they were invented by man, ultimately giving
rise to the rationalist/empiricist divide on the question of the origin of knowledge, and one
might speculate as to whether these points of view led ancient philosophers to the claim that
language was given to children by the gods, or invented by them as they went through the
procedure. But to my knowledge, the question was never really put in these terms.
Certainly with ancient grammar mainly focussing on word meanings and morphological
properties of words, the problem of learning complex syntactic systems was not considered
and we had to wait until the early 20th century before syntax became seen to be a central part
of grammatical investigation and it was recognised that there was a complex system that
would have to be acquired. Even then, however, theories of language acquisition tended to
down play the problem and so were entirely inadequate in accounting for the fact that
children can and do do it.
For example, Bloomfield (1933), influenced as he was by Behaviourist Psychology, put
forward the following proposal as to how language acquisition works. Children make noises
from birth. Some of these noises approximate language noises of the child’s parents.
Whenever the child produces such noises he or she is rewarded by parental attention (aaah!
she just said mama!), which reinforces the behaviour of producing that sound. In this way,
appropriate languages sounds become more likely to be part of a child’s output and nonappropriate sound production decreases, until such a time that the only sounds that a child
makes are those of the parents’ language.
While this theory does make use of some real aspects of language acquisition, such as the fact
that children do babble, it is clearly totally inadequate to account for even the simplest
observations concerning what children actually do. We saw last week that children acquire an
abstract grammar not sentences (nor indeed reinforced linguistic behaviour) and it is clear
that such a system could not possibly be learned by the proposed method. It requires the child
to come out with all the relevant constructions in the first place, so that these can be
reinforced by the parents, and the chance that this could happen accidentally are so close to
zero as to be not worth considering. Thus the child would already have to possess the
linguistic system that they were supposed to be learning in order to be able to learn it!
Nearly 25 years later, the Behaviourist B.F. Skinner published another account of language
acquisition (Skinner 1957), making use of a more sophisticated model of language, which we
will not go into the details of. More important is the fact that two years later Chomsky
published a highly critical review of Skinners work (Chomsky 1959), pointing out that it still
suffered from the same problems facing Bloomfield’s simplistic theory, though heavily
disguised in what Chomsky saw as pseudo scientific notions and terminology. The
subsequent fall of Behaviourism and the popularity of Chomsky’s Syntactic Structures (1957)
virtually left Chomsky unchallenged in his rationalist approach to language and language
acquisition.
Mark Newson
2
The Innateness Hypothesis – early years
Of course Chomsky’s approach to language acquisition is the rationalist one: the child is born
with something which specifically functions to acquire language. It seems hard to avoid this
conclusion given the facts of languages acquisition: the difficulty of the task and the ease
with which it is carried out.
However, although Chomsky had defeated the strong empiricist ‘tabula rasa’ approach, and
had argued convincingly in favour of an innatist position, he did not at the time put forward
any particular theory. His view was that the theory of language acquisition that was most
likely to succeed would be based on a successful theory of language, which was naturally the
primary objective of linguistics. Thus while Chomsky argued that an account of language
acquisition without reference to some in built mechanism, which he strongly believed would
have to be directly related to language, and not just some general ability to learn, he was not
really in a position to say just what that mechanism was.
Thus, the first attempts to provide a theory of language acquisition along Chomskyan lines
were based on a rather vague notion of some kind of Language Acquisition Device (LAD)
that the child came equipped with. As transformational grammar developed, and especially as
the mathematical linguistics became better understood, it was suggested that what the LAD
did was to order possible grammars to provide the learner with not only a set of hypotheses to
be tested against the linguistic data presented, but also a set path through this set of
languages, so that once a grammar was rejected, the learner would adopt the next hypothesis
determined by the LAD. Thus the model of acquisition that followed these ideas was as in
(1):
(1)
data → LAD → learned grammar
In this way, we can see how this theory at least attempts to address the fundamental problem
of language acquisition: how is it that the child is able to construct an abstract grammar when
what they receive is representative sentences from the language generated by the target
grammar.
However, lacking much of the detail, at the time there was virtually no way to make this
theory fit with observations about what children actually did. The LAD was some sort of
‘black box’ that if one fed linguistic data into it, out popped a hypothesised grammar, but just
what went on inside the box was little understood. Thus the theoretical approach to the study
of language acquisition and the experimental approach, which investigated children during
the process of acquisition seemed miles apart with little chance of meeting up.
3
Chomskyan Inspired Theories of Acquisition
This is not to say that there were no attempts during this period to try to account for child
language acquisition patterns using the kind of linguistics that Chomsky introduced. In 1963
Martin Braine proposed to account for the early two word stage in terms of a simplified
phrase structure grammar, which he called a Pivot Grammar.
The idea is that children operate with a simplified set of categories, split into two: pivots and
open categories and sentences are constructed from these by combining them following a
simple phrase structure grammar:
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Language Acquisition – Theories of Language Acquisition
(2)
S→OP
S→PO
S→OO
So, for example, if the child had categorised the word see as a pivot and the words daddy and
baby as open categories, the following sentences would be possible:
(3)
a
b
c
daddy see
see baby
daddy baby
The idea was that from this simple grammar the child was able to work up to a more
complicated one in which there were more categories and more complex rules, including
transformations.
This idea however, although initially popular, suffered a number of problems. First it is not
clear how entertaining a grammar which is clearly of a different nature to adult grammars is
supposed to help the child to eventually acquire an adult system. One would have thought
that if human language is something which comes from having a human mind, that children’s
grammars should be of the same nature as adult grammars and that switching radically from
something which is nothing like an adult grammar would hinder rather than help the process.
Moreover, it was also pointed out that even at this stage, the similarities between child and
adult language are greater than one would expect if children’s grammars were so radically
different. For example, the word orders that children use on the whole tend to be alike to the
adult language. This is obviously difficult to account for it children and adults make use of
very different grammatical systems. Indeed, the evidence, such as it is, seems to indicate that
even at this early stage, children operate with similar categories to adults, at least in terms of
nouns, verbs and adjectives. As we know, the functional categories seem to come ‘on line’
along with the syntax spurt at about 2 and a half years. This is again something that the
adoption of a pivot grammar would fail to account for: why would there be a slow
development of grammar from the two word stage until about the age of 2 and a half and then
a rapid expansion of grammar after this, coinciding with the development of functional
categories, if children start with a pivot grammar and then abandon it (suddenly) in favour of
something far more complicated?
4
The Effect of Constraints on Language Acquisition Theory
As generative theory underwent development during the 1970s, moving from construction
specific rules, to a constrained system using more general principle, then, for the first time,
some notion of Universal Grammar became a tenable consideration. If rules are not directed
at specific constructions in specific languages, then it can be proposed that the same rules are
applicable to more languages. For example, many languages seem to have a wh-movement
process, which moves interrogative elements to the front of the clause, though there are some
differences as to what moves and where.
A viable theory of Universal Grammar would of course make an innatist theory of language
acquisition more specific. It could be claimed that children are born with the principles of
Universal Grammar as part of their innate language faculty and it is this that aids them in
their acquisition process. For one thing, an innate Universal Grammar imposes restrictions on
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Mark Newson
what the child can hypothesise about the language they are attempting to learn. This in itself
would greatly help in the learning process as searching a restricted space of possible solutions
for the right one is clearly an easier task than searching an unrestricted space. Universal
Grammar defines what is a possible human grammar and therefore determines what is not
possible and not to be hypothesised by the learner. This also answers the learning problem of
Gold’s work in formal learnability theory: Gold showed that context free and context
sensitive languages are unlearnable from positive data only (which seems to be what is
available to children) given fairly generous assumptions about the learning situation and the
conditions placed on the process. But the problem can be solved if human languages are not
equated with the set of context sensitive or free languages, but rather constitutes a more
limited set. Obviously, this is potentially what Universal Grammar does. It remains to be seen
whether the set of languages defined by Universal Grammar are learnable in Gold’s model,
but clearly that is a difficult question to ask until we know more about what Universal
Grammar is.
In a real sense, the notion of Universal Grammar also fleshes out what was vaguely reported
as the LAD. The general learning situation assuming an innate Universal Grammar looks as
follows:
(4)
data → Universal Grammar → particular grammar
The linguistic data provide the child with evidence about which of the options made available
by Universal Grammar are made use of in the target language, and so the child is able to
home in on the correct grammar.
Although the notion of Universal Grammar would be a step in the right direction for a viable
innatist theory of language acquisition, it still remains to be shown how it could work.
Obviously, Universal Grammar can only be seen as the basis of all human languages, not
what generates human language as otherwise there would only be one language and this
would not have to undergo any learning process at all. The fact that there is more than one
possible human language and that children do undergo some period of language learning
demonstrates that Universal Grammar must allow a certain degree of variation and that this is
what is the cause of the learning process. We will discuss how this is done in the next section.
5
Principles and Parameters Theory
By the time of the 1980s, grammatical theory had reached a stage at which grammatical rules
were as generalised as possible: the X-bar principles of phrase structure and the movement
rule Move  could hardly be any more general. Such is the nature of such general rules that
we can take them to be a part of all languages: all languages have phrases which have heads
and these heads select complements, etc. in accordance with X-bar theory; all languages
show some evidence of things moving from one place to another. Chomsky (1981) argued
that these ‘rules’ are so general and therefore different to the kind of grammatical rules
previously utilised in syntactic theories, that they should not be considered rules at all.
Instead, he proposed that we term them ‘principles’. Principles are then what Universal
Grammar is constructed from.
However, principles cannot account for language variation. It may be true that all languages
make use of the notions ‘head’ and ‘complement’, but languages differ in terms of how these
elements are related to each other syntactically. For example, in English heads always
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Language Acquisition – Theories of Language Acquisition
precede their complements, unless the complement is moved. This is true no matter what the
head. So, nouns, verbs, adjectives and adpositions all have following complements (which is
why adpositions are called prepositions in English):
(5)
a
b
c
d
student [of linguistics]
write [a letter]
fond [of chocolate]
under [the bridge]
In a language like Japanese for example, the head always follows its complement (Japanese
has post positions):
(6)
a
[gengogakuno] gakusei
linguistics(of) student
[tegami o] kaku
letter –acc write
[hashi] shita
bridge under
b
c
Note that both English and Japanese are similar in some respects as they have phrases headed
by nouns verbs and prepositions (and adjectives, I just couldn’t find one for Japanese), only
the order differs:
(7)
NP
NP
N'
N'
N
PP
PP
student of linguistics
N
gengogakuno gakusei
linguistics(of) student
Both of these structures conform to the same basic rules:
(8)
X' → X YP
or
X' → YP X
Thus we might claim that while the X-bar principles are universal, languages differ in how
these principles are realised and in particular in whether the head precedes or follows its
complement. Thus we might suppose a general X-bar rule which makes no reference to order,
saying that an X' contains the head and its complement, and then have a variant rules which
says that either heads come first or last:
(9)
X' → X, YP
a) head is first
b) head is last
The choice given in this rule is known as a Parameter: a variable part of a principle which
may be set to one of a number of possible values. It is the existence of parameters, then, that
give rise to language variation.
The theory that follows from these assumptions is that Universal Grammar consists of a set of
invariable principles which may come with a number of parameters. Each parameter has two
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Mark Newson
or more possible values that it can be set to. Universal Grammar, then, is similar to any
possible human grammar, without its parameters set. Any specific language is the result of
setting the parameters in a particular way. Thus we have the following model:
(10)
Universal Grammar + parameter settings = a specific language
It also follows that it is the parameter settings that require learning. In learning English, the
child does not have to discover that phrases have heads and complements, as this is true for
all languages and is a principle of Universal Grammar and therefore given innately, but they
do have to find out whether English is a head initial language or a head final one. Thus they
must learn how to set the ‘head parameter’. Presumably this is not particularly difficult: all it
requires is hearing one instance of a head initial phrase, such as see the ball, and the
parameter can be set. Recall, this is the kind of thing that children show mastery of from a
very early age.
6
Problems for Parameter Setting
One fairly obvious problem with the parameter setting theory of language acquisition is that it
appears to make the problem of language acquisition so easily solved that it is hard to see
why it takes children as long as five years to complete. If it is just a matter of hearing one
relevant piece of data for each parameter to be set, then surely language acquisition should be
almost spontaneous! Of course, on top of parameter setting, children have to learn lexical
facts and this, to a large extent, must be rote learning as the lexicon is entirely unpredictable
information. But still, the evidence is that it is not just words that take time to learn, but
syntax also develops.
Recall however, that there are two spurts in the acquisition process, one where vocabulary
increases and basic word combinations start to take place and the second where functional
categories are learned and more complex syntactic processes start to appear. It has been
suggested that these spurts indicate that language acquisition is to some extent biologically
triggered, similar to the way teeth develop or the body undergoing development at puberty.
Clearly these bodily changes are biologically determined – set to go off at some predestined
time. The idea is that the development of language may also be subject to these kinds of
maturational time lags and that the onset of certain linguistic notions is biologically
determined rather than subject to a gradual learning process. If this is so, it would account for
the sudden spurts that we see in child linguistic behaviour and it would further account for
why parameter setting is generally spread out rather than being spontaneous.
What is needed is some detail about exactly what matures and so what is available (and
unavailable) to the child at any particular moment in the acquisition process. It seems clear
that what develops during the vocabulary spurt is some of the basic concepts which allow
combinations of words, particularly the kind of semantic relationships for forming basic
propositions. For example the idea of predicate and argument seems to be missing at the one
word stage, but is present once two or more words start to be combined. The thematic words
which take part in these combinations are also what are evident at this stage and it is verbs,
nouns and adjectives which predominate. During the syntax spurt it is the functional
categories which seem to mature. Current syntactic theory holds that it is the functional
words which play a central role in the more complex aspects of syntax and so it is not
surprising that these syntactic processes are absent before functional words are present and
that they should rapidly develop after the onset of these elements.
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Language Acquisition – Theories of Language Acquisition
A more worrying criticism of parameter setting is that it virtually reduces an otherwise highly
explanatory theory of language to mere description. This argument is based on the question
of what counts as a parameter. Obviously as parameters are the mechanisms for language
variation, it is parameters which determine the possible range of linguistic variation. But in
principle anything may be parameterised and any parameter can have any conceivable value.
The head parameter we saw above is a simple case as there are only two possible ways to
order the head and the complement and both of these are realised in languages. But if there is
no limit on what we can consider to be parameterised, we are free to assume that differences
between any two languages are to be captured by a specific parameter setting. The absurd
limit to this would be for all languages to be the result of unique parameter settings which are
not apparent in any other language. Thus there would be a +Spanish parameter setting and a
+Swahili setting, etc. This would be perfectly consistent with the notion of Universal
Grammar under the view of principles and parameters theory, but it would render the whole
theory without explanation.
The response to this problem has tended to build into the notion of Universal Grammar some
restrictive theory of parameters, though it has to be said that nothing has been particularly
persuasive. For example, one of the earliest ideas about parameters is that given that they
were embedded in a theory in which linguistic complexity arises from the complex
interaction of simple and general grammatical modules, that parameters, though simple in
themselves could affect grammars in extensive and yet subtle ways by changing the
conditions in which the modules interact. In effect then, a small change in a parameter setting
could be enough to have wide and fairly drastic effects on resulting language. This would
account for why languages can seem to be so different from each other and yet be related to
the same Universal Grammar. Note that this would also aid the acquisition process too as it
means that the amount of data that can be used to trigger a parameter setting is much wider.
Probably the most well known of this kind of parameter was the pro-drop parameter, which,
amongst other things, determines whether a language can have an empty pronoun subject of a
finite clause or not. English is a non-pro-drop language as its finite clause subjects have to be
overt:
(11)
a
b
he sleeps
* sleeps
Hungarian is a pro-drop language as it can have a covert subject in a similar case:
(12)
a
b
ő alszik
alszik
Thus, there are two settings for this parameter: pro-drop and non-pro-drop. It was in fact
more technical than this, resting on a certain property of the tense and agreement inflection of
the language, but we need not go into these details. However, it was also claimed that the prodrop parameter was responsible for other phenomena too (again, the technicalities will be
avoided, but it should be noted that the facts did follow from the same properties of the
inflection, and wasn’t just a stipulated association as might seem from the present
presentation). For example, the presence of pleonastic (meaningless) subjects in a language
correlates with the language lacking null subjects in finite clauses:
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Mark Newson
(13)
a
b
it seems that John is ill
sembra che Gianni sia ammalato
seems that John is ill
In English the it subject is necessary for a grammatical sentence, but in Italian, a pro-drop
language, there is no such element.
Another distinction between pro-drop and non-pro-drop languages is the ability to invert the
subject with the VP. This is possible in Italian, for instance, but not in English:
(14)
a
b
ha telefonato Gianni
* has phoned John
Finally, certain long distance movements are possible in pro-drop languages, seemingly
violating certain Island conditions, which are not possible in non-pro-drop languages:
(15)
a
b
che credi che verrà
* who do you believe that will come
Thus, if we set the pro-drop parameter one way, we get a language which can drop
pronominal subjects, which doesn’t have pleonastic subjects, which can invert subjects with
VPs and which can move wh-elements over long distances. If we set the pro-drop parameter
the other way, we get a language which has overt subject of finite clauses, which has
pleonastic subjects, which cannot invert subjects and VPs and which cannot move whelements over long distances. Note that the last fact is quite complex and the data is not likely
to be the sort of thing that children will be exposed to. But all they need is to know whether
the language has null subjects or not, and that will tell them whether wh-elements can move
long distances or not and they will not have to hear sentences such as in (15) to know this.
For, the important point is that this idea may serve to limit the kind of thing that we can
propose as a possible parameter. If all parameters are like the pro-drop parameter, affecting a
wide number of linguistic phenomena, then we are not entitled to come up with a parameter
to account for a single difference between two languages.
Unfortunately, this programme did not really succeed in that the pro-drop parameter,
although a spectacular example of what parameters could do, seemed to be fairly unique in
this way. Most parameters that were proposed were like the head parameter, which just deals
with the order of heads and complements and plays no role in other linguistic phenomena.
Moreover, as further languages were investigated, even the pro-drop parameter was eroded as
it seems that there are pro-drop languages which do have expletive subjects, which cannot
invert subjects and VPs and there are non-pro-drop languages which can move wh-elements
over long distances. Thus, the only thing the pro-drop parameter really determines is whether
the language allows null subjects or not. Hence the parameter is only associated with one
observable linguistic property.
A more successful restriction follows work by Borer (1984), which showed that many
linguistic differences between languages can be put down to properties of their functional
categories. Just like the difference between pro-drop and non-pro-drop languages seems to be
correlated with how rich the inflections of the language are (pro-drop languages have rich
inflectional systems and non-pro-drop languages have poor inflectional systems: compare
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Language Acquisition – Theories of Language Acquisition
English and Hungarian in this respect). Borer demonstrated that other differences between
languages could be put down to properties of other functional elements and hence if
parameters are what deal with language variation, it seems that parameters are limited to
properties of functional categories such as inflections, determiners and complementisers.
From this perspective, apart from superficial differences, all languages are the same with
respect to their argument-predicate structures: the equivalent verb to smile in all languages
will take just one argument, whereas the equivalent to give will take three.
The Functional Parameterisation Hypothesis works well for many linguistic differences, but it
is difficult to see how differences such as the head parameter can be reduced to the properties
of functional elements as it obviously affects the order of non-functional elements such as
nouns and verbs. Therefore even if some parameters are limited to the properties of
functional elements, it seems that we also need other parameters which are not and hence this
is not a fully restrictive theory.
7
A brief word about acquisition theories from other grammatical perspectives
In Chomsky’s latest thinking about language, the Minimalist Programme, linguistic
differences have been reduced to whether elements move overtly or not and thus
parameterisation is restricted to this distinction alone. It has to be said however, that the
application of this theory is not as wide as the theories of the 1980s (e.g. Government and
Binding theory) and so it is not at all clear whether this assumption can be made compatible
with all observable linguistic differences between languages.
Optimality Theory, on the other hand, has come up with an alternative to Parameter setting as
a theory of linguistic variation and acquisition. In OT, constraints conflict with each other so
that they require opposite things of a grammatical structure. The conflict is settled by ranking
the constraints so that in cases of conflict the highest ranked one will be conformed to and the
lower ranked one violated. The point is, then, that it is the ranking of the constraints that
determine what is grammatical in a language and therefore if the ranking differs, different
things will be grammatical. Ranking therefore accounts for linguistic variation. It follows that
it is constraint ranking that must be learned by a child acquiring the system: the constraints
themselves can be assumed given by Universal Grammar. Formally this is a very different
kind of acquisition process to Parameter Setting and it can be investigated in different ways.
There are interesting results in this area, but it would take us too far from our current position
to be able to go into any details.
8
Conclusion
It is very difficult not to believe in an innate ability in children to learn language. Chomsky
has argued forcefully that this innate ability must be specific to language and not a kind of
general ability to learn well (how could infants learn whether or not long distance whmovement is possible in their language when the data needed to figure this out from is far
more complicated than could be reasonably be expected to be available to a child). However
is was only once we had any reasonable idea of what Universal Grammar was that a realistic
innatist theory could be presented. While this is still far from perfect, and obviously the
theory of Universal Grammar and the dependent theory of language acquisition changes as
linguists views on language develop, the notion that came about in the 1980s was enough for
the theory to make predictions about what actually goes on in the learning procedure and as
such, for the first time, there was real contact between theoretical linguists and child language
acquisition specialists. The parameter setting theory spurred a great many investigations into
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Mark Newson
details about how children learned specific linguistic phenomena and in turn this research
informed linguistic theory about what was a viable theory and what was not. Although of
late, with the Minimalist Programme retreating into more theoretical questions, the contact
between linguists and acquisitionists has not been quite so productive, principles and
parameters theory has shown what is possible when linguistic theory is able to develop in this
direction.
References
Bloomfield, Leonard 1933 Language, Rinehart and Winston, New York.
Borer, Hagit 1984 Parametric Syntax, Foris, Dordrecht.
Braine, Martin D. S. 1963, 'The Ontogeny of English Phrase Structure: the First Phase',
Language 39, 1-13.
Chomsky, Noam 1957 Syntactic Structures, Mouton, the Hague.
Chomsky, Noam 1959 ‘Review of B.F. Skinner’s Verbal Behaviour’, Language, 35, 26-58.
Chomsky, Noam 1981 Lectures on Government and Binding, Foris, Dordrecht, Holland.
Gold, E. M. 1967 ‘Language identification in the limit’ in Information and Control, 10, 447–
474.
Rizzi, Luigi 1982 Issues in Italian Syntax, Foris, Dordrecht, Holland.
Skinner, B. F. 1957 Verbal Behavior Appleton Century Crofts, New York.
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