Parents' report of vocabulary and grammatical development of African American preschoolers: child and environmental associations.

This study examined how child and family factors affect individual differences in the language development of African American children between 18 and 30 months of age. Participants were 87 African American children, primarily from low-income families. Children's vocabulary and grammatical skills were assessed at 18, 24, and 30 months of age using the short form of the MacArthur Communicative Development Inventory (CDI), a standardized parent report tool. Standardized language tests were administered repeatedly between 1 and 3 years of age. Results showed that children's vocabulary and utterance length grew linearly over time between 18 and 30 months of age. Children from more stimulating and responsive homes were reported to have larger vocabularies, to use more irregular nouns and verbs, and to use longer utterances, in addition to having more rapid rates of acquisition of irregular forms and longer utterances over time. Girls used longer utterances than boys and more irregular forms. Girls also had larger vocabularies in a secondary analysis that eliminated children whose parent report of their vocabulary was substantially lower than children's scores on a standardized language test. There are indications that some parents may be under-reporting their children's early vocabulary and grammatical development, with a high proportion of the parents reporting their child's 30 month vocabulary and grammatical development as being at or below the 10th percentile according to the CDI norms.