Child Language Acquisition: Early Vocabulary

The following chart illustrates the rate at which children learn new words:

Age  Number of words used

18 months 50+ *

2 years 300 

5 years Aprox 3000

7 years  Aprox 4000

*Children can understand a lot more words than they can say. Although an 18 month old child can only actively produce 50 words, they can understand aproximately 250.

As a child gets older, their vocabulary increases and their grammar becomes more accurate and complex. 

Katherine Nelson conducted a study of an eighteenth month old's first fifty words. Nelson created five new categories for a child's early vocabulary:

1. Classifying objects (eg. dog, ball, cat)

2. Actions/events 

3. Specific objects (eg. mummy, daddy)

4. Modifying words (eg. teeny, big)

5. Social words (eg. hello, bye, yes, no)

Overextension = Where a child uses a word refer to different things which are related.

Underextension = Where a child makes restrictive use of a word.

Rescorla's analogical and categorial extensions

Analogical = Where a word is used to refer to several different things which bear physical/functional similarities.

Categorial = Where a word is used to refer to things in a similar category.