Index of Productive Syntax

A new method for evaluating the grammatical complexity of preschool natural language corpora is introduced. In the Index of Productive Syntax, occurrences of 56 syntactic and morphological forms are counted, yielding a total score and subscores for noun phrases, verb phrases, questions/negations, and sentence structures. Development of the index and analyses of its reliability and age-sensitivity when applied to language samples of 2- to 4-year-olds are described. Some advantages and limitations of the index as a research and clinical instrument are also discussed.