Ch.5: Lexical development: learning words

Transcription

1 Ch.5: Lexical development: learning words Lexical Knowledge in Adults The Mental lexicon -mental lexicon: knowledge of words that adults have What Is A Word? -word: symbol. It stand for something without being part of that something. The relation between words and what they stand for is arbitrary. Can be sued to refer to things -reference: a word to be sued consistently in combination with a particular object is not sufficient to qualify that word use as referential The course of early lexial development First words -first words may be harder to distinguish from earlier protowords described in the previous chapter on phonological development. The critical difference is that although protowords are sound sequences that seem to have consistent meaning for the child, the particular sounds of protowords are not derived in any obvious way from the language the child is learning. In contrast, the firs towards are approximations of words in the target language, even if somewhat rough approximations -First words may be context bound. Like the protowords that preceded them, the first words children use may be tied to particular contexts -on the basis of data from hundreds of American and Italian children, Caselli and colleagues concluded that children s first words may always be parts of routine or language games. Such specific or function specific understandngs of word use are crucially different from adult s mental representations of words as symbols that refer Is there a prelexical stage of word use -because the understanding of word meaning that seems to underlie children s early context-bound words is so different from adults mental representations of word meanings, some have argued that these context bound words are not really words at all. Suggesting these words are merely responses elicited by particular environment conditions (prelexical) First words can also be referential -Harris and colleagues categorized the children s first words into three groups. -The largest group was context-bound words -Nominals (names for things) came in second -the smallest group was contextually flexible words (can be used in more than one context) Why are some words context bound and others referential -remember referential means not bound to one context -why arent t all words referential from the beginning if they can be from the start? -possibly due to limited understanding -limited experience Context-bound words become decontextualized -words that are at frist context bound gradually become decontextualized -studies of early ages shows that children start out with atleast two kinds of lexixal entries for the words they use 1. situation specific 2.more adult like. A word encodes a meaning Vocabulary development from first words to 50 words

2 -achieve 50 wrds between 15 to 24 months (usually 18) -study of the first 50 words showed 1. the most common were specific nominal (ex. Mommy) 2. general nominal (dog, ball) 3. action words (go, up, look) 4. modifiers (all gone, big, mine) 5. personal social words (no, want, please) 6. the least common was grammatical function words (what, is, for) Vocabularies at the 50-world mark -childrens first words represent their experience -include routines, names for common things they see, verbs with more general meanigns that they use often (example. up) -dominated by nouns (45% of first 50 words) What determines the context of early vocabularies -children acquire nouns before verbs because the meanings nouns encode are easier for children to learn than are meanings verbs encode -nouns refer to entities or things and young children can have an understanding of things based on their perception of the physical world. Verbs on the other hand, express relationships among things, and these relational meanings are less available to young children though nonlinguistic experience -natural partitions hypothesis: physical world makes obvious the things that takes nouns as labels, whereas the meanings that verbs encode have to be figured out from hearing the verb in use -relational relativity hypothesis: the reason verb meanings must be figured out from the use is that they do not naturally emerge from the structure of the world, leaving open the possibility that verb meanings will vary from language to language -in support of this view, Gentner refers to linguistic work showing that noun meanings are more similar across language than are verb meanings -summary: according to the natural partitions and relational relativity hypothesis, in learning nouns children need only learn the labels for means they already have, whereas in learning verbs children have to figure out how meaning is packaged by their language -a different hypothesis attributes the source of the noun bias in children s early vocabularies to the nature of children s early understanding of how types of words and types of meanings are linked. According to this view, children understand that certain kinds of nouns label objects at the very beginning of language acquisition. Understand that other kinds of words are linked with other kinds of meanings (adjectives) comes later. Children s first words are the words they first know how to link meanings -also been argued that the child s cognitive or linguistic understandings have nothing to do with why some words are acquired earlier than others. Rather it si a language-learning problem -easiest words to learn through observation are nouns -another relevant factor has to do with how the particular language being acquired illustrated nouns and verbs -children acquiring Korean, Japanese, and Mandarin (Chinese) show less of a noun bias than do children acquiring English -in these languages, a verb is often the final word in a sentence, and this position may be particularly salient (noticeable ) to children. -also the grammars of these languages allow noun dropping, thus making verbs relatively more frequent in the input -class and culture also affect children s vocabulary

3 -American mothers spend a great deal of time labeling objects for their babies/ Japanese mother do so much less frequently Overextensions and Underextensions of first words -underextensions: using a word in more restricted fashion -overextensions: overly broad uses -overextensions are highly variable -overextensions are very noticeable when they occur, but they are actually not very common -good evidence that overextensions occur for reasons other than incomplete word meanings -one possibility why a child might call a horse a dog is that the child really thinks the word for horse is dog -supporting this view what that incidences of overextensions decline as children acquire more differentiated vocabularies The Word Spurt -lexical development starts slowly for most children. During the first months after speaking their first words -during these months of slow lexical growth, words that were apparently learned at one point do not necessarily become permanent additions to children s permanent additions to children s productive vocabularies -lexical development seems to shift into a different gear at about the 50 word milestone. Much faster rate -this lexical development is known as word spurt, word explosion, and the naming explosion What is the word spurt -some claim that a spurt occurs while others claim it does not -does not: gradual increase. With possibly a plateau that makes it seem as though there is a spurt afterwards - graphs of children words shows spurts (some may occur later than others) What causes changes in word learning efficiency -onset or maturation of internal word-learning constraints occur at this point -reaching the threshold of a 50 word vocabulary gives children a basis for figuring out principles of how the lexicon works -children s phonological abilities influence their very early vocabularies, raising the possibility that changes in the nature of children s phonological systems contribute to the word spurt -comprehension vocabularies are greater than production vocabularies -not only differ in size but also in content -proportionately more verbs in children s comprehension vocabularies than in their production vocabularies Word processing -lexical representations are built gradually and become more complete and more robust with development. Individual differences in lexical development Individual differences in language style -most first words are context bound -diffrences among children in the number of context bound words in their early lexicon may reflect different experiences. May also reflect differences in approaches to langauge acquisition -another difference is if they are risk takers

4 -risk takers will jump into talking with a minimal understanding of what they are saying. Mreo cautious children will produce fewer context bound words -sociability is one last sort of difference among children. More sociable is more context bound Referential and expressive language users -referential language style: more object labels in their vocabularies -expressive language style: fewer object labels and more personal/social words -most children in between the two Sources of the referential/expressive differences in lexical development -again experience. Some parents spend a lot of time teaching their children labels -referential children are more likely than average to be the firstborn of college-educated parents Significance of the referential/expressive distinction -thought at first referentially was the difference but then rejected. Individual differences in the rate of lexical development -vocabularies of chidren of the same age vary a lot Environmental factors that influence the rate of lexical development -experience, including the sheer amount of talk the child hears -the more speech they hear the greater the vocab development -birth order and socioeconomic status are important -effects of birth order are small and ot always found, but when they are found, the consistently show that firstborn children have a slight advantage in vocabulary development over later born children - a likely cause of this difference between firstborn and later born children may be the different amount of one to one interaction they experience with an adult -effects of socioeconomic status (SES) on vocab development, but these effect grow larger over time and always show that children of more educated parents have larger vocabularies than children of less educated parents -more educated mothers talk to their children more -its not just about the amount of speech heard but the quality of it. -hearing a rich vocabulary (one that includes many different words and alos includes rare or sophisticated words) is associated with more rapid vocabulary development -another reason why SES is important Child factors that influence the rate of lexical development -children who are very outgoing may elicit more input which, in turn may support more rapid language development -phonological memory: the ability to remember a sequence of unfamiliar sounds -sex differences are small and not always present, but several studies have shown girls to be more advanced in vocabulary development -possible experimental bias with mothers talking to girl babies more than boy babies -however girls sometimes demonstrate word-learning skills that boys of the same age do not The process of word learning Word segmentation -speech segmentation: must find word boundaries -child directed speech helps with this Word referent mapping -mapping problem: the process of knowing if its labeled or not -it appears that children begin by making an initial fast mapping between a new word they hear and a likely candidate meaning

5 -when the child hears a new word, the setting usually contains multiple candidate referents to the word Lexical constraints on referent mapping -lexical principles (lexical constraints): guide the child by limiting the possible interpretations of new words that children must consider -whole object assumption: child s assumption that words refer to whole objects -mutual exclusivity assumption: the assumption that different words refer to different things Pragmatic bases of word learning -Pragmatic principles (principles about how language is used) -principle of conventionality: the meaning of a word is determined by convention -principle of contrast: different words have difference meaning -close to mutual-exclusivity assumption but differs in that it allows for multiple labels for different meanings (ex. Such as dog and animal) Input as a source of support -the way in which people talk to children makes word meaning in context much less ambiguous Syntax as a clue to word meaning -another potential source about word meaning is the structure of the language itself -synaptic bootstrapping hypothesis: proposal that knowledge of language structure is generally useful for learning new verbs Word extension -word extension: does it refer to other things -taxonomic assumption: holds that words refer to things that are the same kind Learning semantic Organization -learning lexicons of their languages, children must determine which cognitive distinctions are marked in their language and which are not. This level of organizing the world that mediates between cognitive organization and language is called semantic organization -acquiring a language includes learning its semantics (how meanings are linguistically realized) -lexical organization: children learn the semantics of their language with respect to the lexicon