Early vocabulary acquisition by children with Down syndrome.

Early acquisition of object names by 6 children with Down syndrome relative to the acquisition pattern of 6 nonretarded children was investigated. Each child was followed for 14 to 21 months. At the start of the study the children with Down syndrome were 17 to 19 months old. The nonretarded children were 9 months old. Results indicated that the children with Down syndrome were at the same level of cognitive development as the nonretarded children at the onset of both comprehension and production of object names. Soon after language acquisition began, however, the language development of the Down syndrome group began to lag behind their cognitive development: Level of vocabulary development was lower than would have been expected based on level of cognitive development.