This document discusses lexical and semantic development in children. It outlines that lexical development refers to a child's acquisition of words, while semantic development is a child's understanding of word meanings. It provides details on the typical growth of a child's vocabulary from 50 words at 18 months to 2000 words by age 5. It also notes that children understand more words than they can produce at each stage of development. The document examines common errors like overextension and underextension of word meanings as children learn. It outlines three stages of vocabulary acquisition: labelling, packaging, and network building to fully understand word meanings.

1. Lecture Three
Lexical and Semantic Development

2. Lexical and Semantic
Development …
• Lexical development = a child’s
acquisition of words.
• Semantic development = a child’s
acquisition of the meanings associated
with those words.

3. Be careful …
• REMEMBER: vocabulary acquisition
does not end at a certain age. We continue
hearing and learning new words and their
meanings throughout our lives.

4. Rate of acquisition …
• End of first year: child begins to speak.
• 18 months: vocabulary of about 50 words.
• 2 years: vocabulary of about 200 words.
EXPLOSION!!!
• 5 years: vocabulary of 2000 words.
• 7 years: vocabulary of 4000 words.

5. Understanding …
• The previous figures refer to word use.
• At each stage, the number of words
understood by the child is expected to be
higher.
• 18 months: 250 words understood.

6. Meanings …
• When a child adds a new word to their
vocabulary, they are not immediately
aware of its full range of meanings.
• More time is required to acquire this
additional knowledge.

7. First words …
• Research has shown
that there are
predictable patterns
in the words and word
classes first acquired
by children.

8. First words …
• Entities
• Properties
• Actions
• Personal-social

9. First words …
• Predictably, a large
proportion of a child’s
first words refer to
familiar people,
objects and aspects of
social interaction.

10. Word classes …
• Nouns
• Verbs
• Adjectives
• Concrete nouns
• 5-7 years: abstract
nouns begin to be
used.

11. Word classes …
• Grammatical
function words:
noticeably absent in
the early stages of
lexical acquisition.

12. Under-extension …
• Common semantic
error made by
children.
• A word is given a
narrower (under
extended) meaning.
• ‘cat’ is the family pet,
but not other cats.

13. Over-extension …
• Another common
semantic error.
Opposite of under-
extension.
• A word is given a
broader (more
general, over
extended) meaning.

14. Overextension …
• ‘daddy’ for all men,
rather than just the
child’s father.
• ‘dog’ for all four-
legged animals.

15. Over-extension …
• More common: than
under-extension.
• 50 word vocabulary:
one third are likely to
be overextended.

16. Getting it right …
• Age 2 ½ : marked decrease in number of
overextensions.
• Explanation: child’s vocabulary is
increasing rapidly, thus filling the gaps
previously filled by overextended words.

17. Understanding …
• REMEMBER: children’s understanding
of word meanings is ahead of their ability
to produce the corresponding words.

18. Aitchison (1987) …
• Three stages/processes occur during
acquisition of vocabulary:
Labelling Linking words to the objects to which they
refer Understanding that objects can be labelled
Packaging Exploring what labels can apply to. Over/under
extension occurs in order to understand the range
of a word’s meaning
Network
building
Making connections between words –
understanding similarities and
opposites in meanings

19. New vocabulary …
• GRAMMATICAL FUNCTION WORDS
• UNDEREXTENSION
• OVEREXTENSION
• LABELLING
• PACKAGING
• NETWORK BUILDING