VOCABULARYACQUISITION
The construction of a system of vocabulary by a child as part of the process of acquiring a first language. Research studies the increase in vocabulary size and the rate at which it occurs. It also examines the underlying semantic development: for example, the way in which the child learns to form conceptual categories and the way in which meaning associations are built up between the words that are acquired.
The child first has to recognise the word as a linguistic unit, since there are few gaps between words in connected speech. Their attention may be drawn to the existence of syllables, which are identifiable by steady-state periods (i.e. vowels) at the centre of each. They then notice and store recurrent chunks of language which are associated with a particular context. They gradually deconstruct these chunks, isolating perceptually salient sections and recurrent sub sequences. This holistic learning style appears to be adopted by a majority of children; but a minority adopt a localistic style, in which they build individual words into chunks.
Late in its second year (though there is much variation), a child has mastered 50 to 100 words. It may understand four times more words than it produces; but it is also likely to produce certain words without fully understanding what they signify. The first 50 words tend to be mainly nouns, which are frequent in the speech of carers and easily matched to physical objects. However, this may depend upon learning style: a minority are said to acquire a wider range of word classes, especially verbs.
At some point, most children manifest a vocabulary spurt, where the rate of acquisition of new words increases suddenly and markedly. From then until about six years old, the average rate of acquisition is estimated to be five or more words a day. Many of the new words are verbs and adjectives, which gradually come to assume a larger proportion of the child’s vocabulary. The vocabulary acquired during this period partly reflects frequency and relevance to the child’s environment. Basic level terms are acquired first (DOG before ANIMAL or SPANIEL), possibly reflecting a bias towards such terms in child directed speech.
The initial ‘acquisition’ of a word entails its use in a very limited range of contexts. It is only over an extended period of time that a child comes to recognise a word’s full range of senses and comes to establish a system of associations between the word and other items in the lexicon.
Children appear to need minimal exposure to a new word form (sometimes just a single occurrence) before they assign some kind of meaning to it; this process of rapid mapping appears to help them to consolidate the form in their memory. In the early stages, mapping is exclusively from form to meaning; but it later also takes place from meaning to form, as children coin words to fill gaps in their vocabulary (‘spooning my coffee’; ‘cookerman’ for a chef).
Four important issues arise:
Word-object relationship. How does a child recognise, for example, that the word DOG refers to the whole animal rather than its tail and to a whole class of animals rather than to a specific exemplar? See mapping.
Concept formation. The range of meaning first assigned to a word may not coincide exactly with the adult one, though it often overlaps with it. There is then a process in which the concept associated with a word is constantly adjusted as the child encounters more and more exemplars of it. Instances of over-extension or under-extension of the adult meaning are frequent.
Word associations. Connected with concept formation, but less studied, are the relationships between words that the child builds. It needs, for example, to establish complex patterns which link words such as BIG and LARGE but which also differentiate them. Newly acquired words appear to be stored in a very systematic way, as is seen in substitution errors (e.g. the word spoon used instead of FORK).
Cognitive development. A different line of research has examined the order in which items of vocabulary are acquired, and has attempted to match the findings to the child’s cognitive development. The kind of cognitive constraints that need to be considered include attention span and memory as well as world knowledge and ability to handle concepts. Thus, the over-extension of items at the one-word stage may reflect the child’s inability to separate object and event (ball = THROW) but may equally reflect processing limitations due to working memory.
See also: Bootstrapping, Concept formation, Mapping, Over extension, Vocabulary spurt
Further reading: Aitchison (2003: Chaps 16–17); Barrett (1995); Bloom (2000); Clark (1993, 1995); Dromi (1999); Gleitman and Landau (1994); Griffiths (1986); Kuczaj (1999); Neisser (1987); Tomasello and Bates (2001: Part II)
