- MacArthur Communicative Developmental Inventories (CD!) and the Minnesota Child Development Inventor y (MinnCDI, Ireton & Thwing, 1974) are parent report measures that provide an index of growth from birth to 30 months of age. The CD!has a ceiling on the Wordsand Sentences version of 30 months of age; however the MinnCDI assesses development up to 6 years of age. The CD!also has two forms: Gestures and Words for children aged 8- to