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Published online by Cambridge University Press: 27 June 2008
Studies examining factors that influence when words are learned typically investigate one lexical category or a small set of words. We provide the first evaluation of the relation between input frequency and age of acquisition for a large sample of words. The MacArthur-Bates Communicative Development Inventory provides norming data on age of acquisition for 562 individual words collected from the parents of children aged 0 ; 8 to 2 ; 6. The CHILDES database provides estimates of frequency with which parents use these words with their children (age: 0 ; 7–7 ; 5; mean age: 36 months). For production, across all words higher parental frequency is associated with later acquisition. Within lexical categories, however, higher frequency is related to earlier acquisition. For comprehension, parental frequency correlates significantly with the age of acquisition only for common nouns. Frequency effects change with development. Thus, frequency impacts vocabulary acquisition in a complex interaction with category, modality and developmental stage.
Preparation of this article was made possible in part by a grant from the National Science Foundation (BCS-0131829) to PL. We thank Shihfen Tu for the initial calculations of age of acquisition from the CDI database and Janet Patterson for her helpful comments on the manuscript. We are grateful to the many child language researchers who contributed data to the CHILDES database that made possible the estimates of input frequency utilized here.