Linguistic TheoryLinguistic Theory

Lecture 12Lecture 12

Language AcquisitionLanguage Acquisition

Outline of lectureOutline of lecture

• This lecture will be in three parts:This lecture will be in three parts:– What children actually doWhat children actually do– How to model what children doHow to model what children do– Theories about how they do itTheories about how they do it

What children don’t doWhat children don’t do

• Common opinion: children are taught Common opinion: children are taught language by their parentslanguage by their parents

• This cannot be true:This cannot be true:– The vast majority of children learn language The vast majority of children learn language

perfectlyperfectly– Teaching is a skill that has to be learnedTeaching is a skill that has to be learned

• Most parents are not trained teachersMost parents are not trained teachers

– You have to know something to be able to teach itYou have to know something to be able to teach it• No adult ‘knows’ the language that they have learnedNo adult ‘knows’ the language that they have learned

• The first fact stands in direct opposition to the The first fact stands in direct opposition to the following two!following two!

What children don’t doWhat children don’t do

• Maybe, parents can teach like this:Maybe, parents can teach like this:– Wait until child says something ungrammatical Wait until child says something ungrammatical

(this often happens)(this often happens)– Provide the grammatical version as a Provide the grammatical version as a

correctioncorrection

• This does not require them to know the This does not require them to know the grammar – just the difference between grammar – just the difference between grammatical and ungrammatical sentencesgrammatical and ungrammatical sentences

• But ...But ...

• For this to work:For this to work:– Parents must behave consistentlyParents must behave consistently

•They must correct every error the child makesThey must correct every error the child makes

•They must never correct a grammatical They must never correct a grammatical sentencesentence

– Children must know:Children must know:•When a parent repeats one of their sentences When a parent repeats one of their sentences

it is meant as a correctionit is meant as a correction

•What the mistake is in their sentence and how What the mistake is in their sentence and how to alter the grammar according to the ‘correct’ to alter the grammar according to the ‘correct’ sentence provided by the childsentence provided by the child

– The first does not happen, the second is The first does not happen, the second is rather much to expect of a child.rather much to expect of a child.

What children do doWhat children do do

• From birth:From birth:– They make noiseThey make noise

• Soon after:Soon after:– BabblingBabbling

• Not reactive/reflexive noisesNot reactive/reflexive noises

• From about 24 weeks:From about 24 weeks:– Reduplicative babblingReduplicative babbling

• Repetitive CV sequencesRepetitive CV sequences

• Soon after:Soon after:– Non-reduplicative babblingNon-reduplicative babbling

• Differing CV sequences with intonation contours Differing CV sequences with intonation contours

• No one knows why:No one knows why:– It is not essentialIt is not essential

•Babies who had tracheotomies during the Babies who had tracheotomies during the babbling period learn language perfectly babbling period learn language perfectly wellwell

– It is not dependent on environmentIt is not dependent on environment•Profoundly deaf babies do itProfoundly deaf babies do it

– It doesn’t differ depending on language It doesn’t differ depending on language of parents/community of parents/community

First wordsFirst words

• From about 1 year (±0;2):From about 1 year (±0;2):– First ‘meaningful’ words appearFirst ‘meaningful’ words appear– One or two to startOne or two to start– Slowly increases over next 4-6 months, then ...Slowly increases over next 4-6 months, then ...

• From about 1;6 (±0;2):From about 1;6 (±0;2):– Vocabulary spurtVocabulary spurt– First words in combination (2 word sentences)First words in combination (2 word sentences)– Mirrors word order of parent languageMirrors word order of parent language

• This continues for nearly a yearThis continues for nearly a year– Slowly increase in number of words Slowly increase in number of words

which are combinedwhich are combined– But not much syntactic variationBut not much syntactic variation– Until ...Until ...

• From about 2;6 (±0;2):From about 2;6 (±0;2):– Syntax spurtSyntax spurt

•Rapid increase in number of wordsRapid increase in number of words•Syntactically varied expressions presentSyntactically varied expressions present

• This continues to slowly develop for This continues to slowly develop for another 2;6 by which time most of another 2;6 by which time most of the system is in placethe system is in place

What do children learn?What do children learn?

• Clearly, they do not learn languageClearly, they do not learn language– We do not know languageWe do not know language– We know grammarWe know grammar

• That children learn rules is That children learn rules is demonstrated by:demonstrated by:– Wug experiment (Berko 1958):Wug experiment (Berko 1958):

• Here is a Wug:Here is a Wug:

• Here are two .................Here are two .................

• All children say [wʊgz]All children say [wʊgz]– Not [wʊgs] or [wʊgɪz]Not [wʊgs] or [wʊgɪz]

• They have never heard the word beforeThey have never heard the word before• But they know the correct plural formBut they know the correct plural form• So they must be able to generate new So they must be able to generate new

forms from what they have learnedforms from what they have learned

Modelling the acquisition Modelling the acquisition situationsituation• With the onset of the mathematical With the onset of the mathematical

approach to language in the 1960s, linguists approach to language in the 1960s, linguists also attempted to set up a mathematical also attempted to set up a mathematical model of language acquisition.model of language acquisition.

• These models were deliberately These models were deliberately simplifications with respect to the actual simplifications with respect to the actual casecase

• The point being that any negative result for The point being that any negative result for the simplified model would carry over to the the simplified model would carry over to the more complex real situationmore complex real situation

AssumtpionsAssumtpions

• What is learned:What is learned:– Languages (not grammars)Languages (not grammars)

•Thus the ‘learner’ does not have to figure Thus the ‘learner’ does not have to figure out from data what the underlying rules are out from data what the underlying rules are (a more difficult process)(a more difficult process)

– We can assume that the hypothesis We can assume that the hypothesis space is limited to mathematically space is limited to mathematically defined languages (context free, context defined languages (context free, context sensitive, etc.)sensitive, etc.)

• The learning situationThe learning situation– Data from the target language is Data from the target language is

presented to the learner one bit at a timepresented to the learner one bit at a time– On the basis of a datum, the learner On the basis of a datum, the learner

makes a guess at the target languagemakes a guess at the target language– Given the next datum, the learner either Given the next datum, the learner either

sticks with the hypothesis or abandons it sticks with the hypothesis or abandons it in favour of anotherin favour of another

– This continues for ever (no one tells the This continues for ever (no one tells the learner when to stop)learner when to stop)

– Learning is successful if in some finite Learning is successful if in some finite time the learner correctly selects the time the learner correctly selects the target language and never rejects it on target language and never rejects it on future datafuture data

• The learning strategyThe learning strategy– Conservative learningConservative learning

•Learner rejects a hypothesis only if they Learner rejects a hypothesis only if they receive data to show that it is wrongreceive data to show that it is wrong

– Non-conservative learningNon-conservative learning•A hypothesis can be rejected even if the A hypothesis can be rejected even if the

data is compatible with itdata is compatible with it

– Conservative learning is safer – if the Conservative learning is safer – if the target is selected, it will never be target is selected, it will never be rejected as all data will be compatible.rejected as all data will be compatible.

• Data presentationData presentation– Negative and positiveNegative and positive

•Both grammatical and ungrammatical Both grammatical and ungrammatical sentences are presented properly indicatedsentences are presented properly indicated

– Positive onlyPositive only•Only grammatical sentences are presentedOnly grammatical sentences are presented

Gold’s resultsGold’s results

• Assuming a conservative learning Assuming a conservative learning strategy and positive data presentation strategy and positive data presentation only finite languages are learnableonly finite languages are learnable

• Context free, context sensitive, Context free, context sensitive, unrestricted re-write systems (formally unrestricted re-write systems (formally equivalent to transformational equivalent to transformational grammars) are unlearnablegrammars) are unlearnable

Theories of language Theories of language acquisitionacquisition• Structuralist/behaviourist theoryStructuralist/behaviourist theory

– Child makes noisesChild makes noises– Child accidentally makes a noise similar to Child accidentally makes a noise similar to

one of the parent’s languageone of the parent’s language– Parents react to this positivelyParents react to this positively– Child’s behaviour is reinforced and so they Child’s behaviour is reinforced and so they

are more likely to make the same noise againare more likely to make the same noise again– Over time and a series of accidents and Over time and a series of accidents and

reinforcements, the child only makes the reinforcements, the child only makes the noises of the languagenoises of the language

• It should be obvious what is wrong It should be obvious what is wrong with this!with this!

Early ChomskyEarly Chomsky

• The child has some species and The child has some species and linguistic specific innate ability which linguistic specific innate ability which allows her to learn languageallows her to learn language

• The Language Acquisition Device The Language Acquisition Device (LAD)(LAD)– Not much was known about thisNot much was known about this

Mathematical approachMathematical approach

• Assuming that human language falls Assuming that human language falls into one of the mathematically into one of the mathematically defined set of languages, the LAD defined set of languages, the LAD orders possible languages and the orders possible languages and the child selects and rejects grammars child selects and rejects grammars on the basis of thison the basis of this

1970s - constraints1970s - constraints

• With constraints came greater With constraints came greater generalitygenerality

• Generality allows ‘universal’ principles Generality allows ‘universal’ principles to be proposedto be proposed

• Universal Grammar became a Universal Grammar became a reachable goalreachable goal

• But how ‘learning’ operated within But how ‘learning’ operated within this was still unsettledthis was still unsettled

1980s Principles and 1980s Principles and ParametersParameters

• Principles are universal parts of UGPrinciples are universal parts of UG

• Parameters are variable parts of UGParameters are variable parts of UG– Parameters can be set differently for Parameters can be set differently for

different languagesdifferent languages– Parameter settings are what needs to be Parameter settings are what needs to be

learnedlearned

E.g. X-bar principles and E.g. X-bar principles and parametersparameters• English has heads preceding English has heads preceding

complements (object follows V, complements (object follows V, preprepositions, inflections precede VP, etc.)positions, inflections precede VP, etc.)

• Japanese has heads following Japanese has heads following complements (objects precede V, complements (objects precede V, postpostpositions, inflections follow VP, etc.)positions, inflections follow VP, etc.)

• Both have heads and complements but Both have heads and complements but the order varies:the order varies:

• X-bar principleX-bar principle– X’ X’ X, YP (comma indicates no X, YP (comma indicates no

order)order)

• X-bar parameterX-bar parameter– A) head firstA) head first– B) head lastB) head last

• All the child has to hear is one head All the child has to hear is one head initial phrase and she will know that initial phrase and she will know that the language has prepositions and the language has prepositions and VO and I-VP word orderVO and I-VP word order

ProblemsProblems

• Isn’t this a bit too easy?Isn’t this a bit too easy?– Why does it take so long to learn Why does it take so long to learn

language?language?

• Isn’t this too descriptive?Isn’t this too descriptive?– What counts as a parameter?What counts as a parameter?– If any difference between languages can If any difference between languages can

be stated as a parameter we can account be stated as a parameter we can account for any logically possible amount of for any logically possible amount of variationvariation

Restricting parametersRestricting parameters

• Rich deductive parametersRich deductive parameters– A simple underlying parameter is A simple underlying parameter is

responsible for a lot of apparently responsible for a lot of apparently unconnected surface phenomena unconnected surface phenomena because the modules of the grammar because the modules of the grammar interact with each other in complex waysinteract with each other in complex ways

– E.g. Pro-dropE.g. Pro-drop

• Unfortunately this could not be Unfortunately this could not be empirically sustainedempirically sustained

Restricting parametersRestricting parameters

• Languages differ only in the Languages differ only in the behaviour of their functional behaviour of their functional elements (nouns, verbs, etc. are elements (nouns, verbs, etc. are pretty much universal).pretty much universal).

• =the functional parameterisation =the functional parameterisation hypothesis (Borer 1986)hypothesis (Borer 1986)

• This works for some parameters, but This works for some parameters, but it is difficult to see how it can work it is difficult to see how it can work for all (head left/right parameter)for all (head left/right parameter)

Restricting parametersRestricting parameters

• Learners have to learn the lexicon of the Learners have to learn the lexicon of the languagelanguage

• Perhaps parameters are a matter of Perhaps parameters are a matter of lexical differenceslexical differences

• = the lexical parameterisation = the lexical parameterisation hypothesis (Manzini and Wexler 1986)hypothesis (Manzini and Wexler 1986)

• If this is so, it is difficult to see why there If this is so, it is difficult to see why there is not more variation within a language is not more variation within a language with one word conforming to one with one word conforming to one parameter value and another to another parameter value and another to another value.value.

MaturationMaturation• None of these theories account for the syntax None of these theories account for the syntax

spurtspurt– Why do children all of a sudden learn a lot of Why do children all of a sudden learn a lot of

syntax?syntax?• It has been proposed that what happens at this It has been proposed that what happens at this

time is that functional elements enter the time is that functional elements enter the child’s grammar:child’s grammar:– Before they operate only with thematic categories: Before they operate only with thematic categories:

nouns, verbs, adjectives, etc.nouns, verbs, adjectives, etc.• So the question is: why do they not learn So the question is: why do they not learn

functional categories before 2;6?functional categories before 2;6?• The functional maturation hypothesis (Radford The functional maturation hypothesis (Radford

1988)1988)– The notion of a functional category is not available The notion of a functional category is not available

to the child until after a genetically predetermined to the child until after a genetically predetermined time (like teeth and puberty)time (like teeth and puberty)