Let's Be Explicit About the Psycholinguistic Bases of Developmental Measures: A Response to Leonard, Haebig, Deevy, and Brown (2017)

Conclusion We encourage the use of composite diversity and productivity measures when assessing grammar early in development, but we discourage the use of composite accuracy measures until children demonstrate emergence of diverse tense/agreement morphemes across a sufficient number of low-frequency sentence frames.
Source: Journal of Speech, Language, and Hearing Research - Category: Speech-Language Pathology Source Type: research