How cognitive factors affect language development in children with intellectual disabilities

The present study investigated the language development of 50 children with intellectual disabilities (ID) and 42 typically developing children from age 4 to 5 years, and was designed to shed more light on the respective roles of phonological working memory (WM) and nonverbal intelligence in vocabulary and syntax development. Results showed that nonverbal intelligence predicted phonological WM, vocabulary and syntax of children with ID at age 4 and 5, and that it only predicted these skills at age 4 in typically developing children. Furthermore, syntax at age 5 was predicted by vocabulary at age 4 in children with ID, which points to children with ID requiring a larger critical mass of vocabulary for syntactic development to be initiated.

► Language development of children with ID and typically developing children from age 4 to 5 years was studied.
► Influence of phonological working memory and nonverbal intelligence on vocabulary and syntax development.
► Nonverbal intelligence predicts language skills at both age 4 and 5 in children with ID.
► Nonverbal intelligence only predicts language skills at age 4 in typically developing children.
► Vocabulary at age 4 predicts syntax at age 5 in children with ID, showing a prolonged lexical bootstrapping effect.