Validating a Rate-Based Measure of Early Grammatical Abilities: Unique Syntactic Types

This paper introduces an alternative measure of grammatical development, unique syntactic types (UST), for use with young children with intervention goals focusing on the emergence of word combinations. A unique syntactic type refers to a unique combination of two or more words with syntactic status that could fit into the phrase structure of a more grammatically complete adult utterance. The measure is appropriate only for children in Brown's Stage I of language development (mean length of utterance [MLU] 1.00 to 2.00). It is intended to monitor the facility with which children deploy their grammatical knowledge under the real-time demands of conversation. The relationships between UST and existing measures of grammatical development were examined among 20 toddlers with specific language impairment to explore its validity. Similarly, measures of UST obtained on two separate days were compared to evaluate its reliability. Results revealed that UST demonstrates temporal reliability and is highly correlated with MLU (Brown, 1973) and total scores on the Index of Productive Syntax (Scarborough, 1990) at concurrent measurement points. Additionally, UST demonstrates predictive stability over 3- and 6-month intervals. These findings support the use of UST as an alternative measure for tracking the progress of children in this early stage of grammatical development. Data collection strategies for use in real practice settings are also discussed.