Complexity metrics and growth curves for measuring grammatical development from five to ten

Abstract

This project evaluated a set of metrics for assessing the complexity of language samples elicited from school-aged children. The metrics included: mean length of utterance in words (MLU) and in clauses (MCU), Developmental Sentence Scoring (DSS), Developmental Level (DLevel), the Index of Productive Syntax, and propositional density. Each metric was applied to 24 narratives told by children 5-10 years of age collected by Sutton- Smith (1981) and to a second corpus of 38 narratives told by children 5-8 years of age collected by Hicks (1990). MLU, MCU, DSS and DLevel measures were modelled by logistic population growth curves. The growth curve analysis indicated that the MCU, DSS, and DLevel metrics are parametric variations of the same underlying function and revealed that syntactic development acclerated rapidly from the fourth to the sixth year of age, then gradually slowed to an asympotic level at approximately eight years of age.