Senin, 27 Desember 2010

Early Morphological Acquisition

Early Morphological Acquisition

A.  Two Kinds of Words
Lexical Class: carry major meanings of sentences: noun, verb, adjective, adverb
Functional Class: modulate the meanings of lexical class words

• Bound vs. Free morphemes
Bound Categories
- functional categories affixed to lexical categories
Noun: plural {-s}, e.g. two cat/s
possessive {-s}, e.g. cat/’s paw
Verb Inflections:
progressive {-ing} e.g. walk/ing
regular present {-s} e.g. walk/s
past tense {-ed}, e.d. walk/ed
Free Categories
- separate words
Prepositions, e.g. ‘in’, ‘on’, ‘under’
Articles, ‘the’, ‘a’
Pronouns, ‘he’ ‘him’ ‘she’ her’ etc.

Acquisition
• Children begin to acquire functional categories around the time they begin to make word combinations
• They are acquired over several years

B.  Influencing Factors
􀂾 Semantic Complexity, e.g. {-ing} vs. {-ed}
􀂾 Syntactic Complexity, e.g. agreement present tense {-s} vs. past tense {-ed}

‘I walk’ ‘he walk/s’
‘I walk/ed’ ‘he walk/ed’
􀂾 Perceptual Salience, e.g. present {-s} vs. progressive {-ing}
􀂾 Frequency,

e.g. {-s} vs {-ing}
e.g. ‘in’ vs. ‘between’
􀂾 Allomorphy: variants of a single morpheme

E.g. ‘plural’ {-s}
cats /s/ dog /z/ bush /ez/
- children need to acquire all the variants
{-ing} has no variants

C.  Some Studies
Brown (1973)
14 Grammatical Morphemes
Obligatory Occurrence
I ‘on’ ‘plural’
II ‘ing’, ‘in’, past irregular
IV possessive
Brown’s Conclusions
􀂄 Few grammatical morphemes acquired during the first 4 stages
􀂄 Irregular past preceded regular past
􀂄 Plural and –ing first inflections acquired

Cazden (1968)
Adam, Eve, Sarah
5 inflections
Measures:
• Correct use
• Inappropriate Use, e.g. ‘one dogs’
• Overgeneralizations, e.g. ‘two foots’

Interpretation
􀂄 Inappropriate Use precedes overgeneralization
􀂄 Inappropriate Use is a lexical error
􀂄 Overgeneralization only occurs when there is a high rate of success

Marcus et al. 1992
• English past tense
• 11,521 irregular past tense verbs, 83 SS
• Low rate of overgeneralization 2.5%

Explanation:
• Irregulars are memorized; rule for regulars
• Retrieval of irregular blocks rule
• Errors are retrieval errors; i.e. when retrieval fails, rule is applied

Berko (1958)
• 5 & 6 year olds
• A range of English morphemes
• Nonsense words
Berko’s Results
􀂄 Accurate use of all allomorphs takes a long time
􀂄 Not just phonological, I.e. plural, possessive, & 3rd person show different scores

Summary
􀂄 Morphological acquisition covers several years
􀂄 Different factors influence learning
􀂄 Measures vary

D.  General Early Morphological Acquisition
One of the first steps in acquiring a morphology system is discovering which phonetic strings correspond to morphemes. These phonetic strings can then be further analyzed in order to determine their grammatical privileges and contribution to meaning and thus to bootstrap into a functional morphology system. In order to model acquisition of morphological forms by children, an automatic morphology discovery system must have the following characteristics. First, since morphemes must be acquired by the child, any morphology discovery system must use a plausible learning mechanism. This entails not only using information available to the language learner, but also using mechanisms that children possess. Second, because morphemes can appear as (multiple) prefixes, suffixes, and infixes in affixing languages, any morpheme discovery system must have flexibility in terms of the position in the word where the morpheme occurs. Third, it must generate a robust list of morphemes which is minimally sufficient to allow the child to bootstrap into the rest of the morphological system. Finally, given that grammatical morphemes generally occur with a large number of other morphemes (especially root morphemes) across various contexts, grammatical morphemes should play an especially important role in acquiring a morphological system.
The frequent sound sequence approach, when combined with the frames approach, provides a highly plausible model of the beginning stages of morpheme acquisition. Given the important role of homogenous environments, one can speculate that this method would be effective cross-linguistically, and thus could represent a general approach used by children acquiring a wide variety of affixing languages.
In the early stages of acquisition, when the learner has only been exposed to a relatively small amount of data, only a few rules can be learned. As more words are observed, rarer morphological patterns can rise above the noise and be learned.
In addition to identifying surface forms of morphemes, children are also acquiring the syntactic uses of morphemes and determining allophones. It is known in the acquisition literature (Slobin, 1973,1986) that acquisition of homophonous morphemes is delayed since a child must sort out the different syntactic functions of morphemes, whereas acquisition of unambiguous
morphemes is faster.
Children typically begin to say their first words between twelve and twenty months of age. And they produce systematic morphological modulations of those words within their first year of talking. As they move to more complex expression of their meanings, they add grammatical morphemes – prefixes, suffixes, prepositions, postpositions, and clitics. On nouns, for example, they start to add morphemes to mark such distinctions as gender, number, and case; on verbs, they add markers for aspect, tense, gender, number, and person. Within a particular language, children's mastery of such paradigms may take several years. There are at least three reasons for this: (a) some meaning distinctions appear to be more complex conceptually than others, and so take longer to learn; (b) some paradigms are less regular than others, and they too take longer to learn; and (c) language typology may affect the process of morphological acquisition: suffixes, for instance, are acquired more readily, and earlier, than prefixes.In order to acquire noun and verb morphology, children must first analyze the structure of words heard in input, identify stems and affixes, map consistent meanings onto them, and then begin to use those stems and affixes in new combinations. This process of analyzing form and assigning meaning is a prerequisite for the acquisition of inflectional morphology.









REFERENCES
Pdf file of Early Morphological Acquisition
Aronoff, Justin M., Nuria Giralt, and Toben H. Mintz. Stochastic Approaches to Morphology Acquisition, University of Southern California (Pdf file)

Lignos, Constantine., Chan, Erwin. Yang, Charles., P. Marcus, Mitchell. Evidence for  Morphological Acquisition Model from Development Data. University of Pensylvania, University of Arizona

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