Acquiring the English adjective lexicon: relationships with input properties and adjectival semantic typology.

Properties of the input, such as raw frequency and syntactic diversity, have been shown to play a role, to different extents, in the acquisition of nouns and verbs. This study investigated the relationship between three properties of the input (input frequency, syntactic diversity, and variety in noun-type co-occurrence) and age of acquisition of English adjectives. In addition, this study explored the relationship between adjectival semantic typology and order of acquisition. The data are 7262 child utterances and 6318 maternal utterances containing one of 272 adjective in the language samples of two children, Sarah and Adam, from age 2;3 to 5;0 (Brown, 1973) available in CHILDES (MacWhinney, 2000). Statistical analyses revealed that all three properties of the input were significantly correlated with age of acquisition, but variety in noun-type co-occurrence was not a significant predictor once input frequency and syntactic diversity were taken into account. Semantic analyses revealed that the distribution of adjective types and tokens differed between the children and the mothers (to an extent) when the data were examined in terms of adjectival semantic types. The results suggest that both properties of the input and the semantic properties of the English adjective class play a role in its acquisition.