Differences at 17 months: productive language patterns in infants at familial risk for dyslexia and typically developing infants.

Productive vocabulary composition is investigated in 17-month-old children who are participating in an ongoing longitudinal dyslexia research project in the Netherlands. The project is searching for early precursors for dyslexia and follows a group of children who are genetically at risk for dyslexia and a control group during the first 10 years of their lives. Among other measures, the Dutch version of the MacArthur Communicative Development Inventory: Words and Sentences (N-CDI) is used to investigate early vocabulary development. In this article, the first N-CDI results from the 2 groups of 17-month-old children are compared with each other, with other cross-sectional, cross-linguistic studies, and with a similar Finnish longitudinal dyslexia project. The Dutch children show the same general acquisition pattern as documented for other languages, but there are significant differences between the two groups of 17-month-old children in total number of words produced and in the linguistic composition of their productive vocabulary.