Evaluating English Morpheme Accuracy, Diversity, and Productivity Measures in Language Samples of Developing Bilinguals.

Purpose: This work explores the clinical relevance of three measures of morpheme use for preschool-age Spanish-English bilingual children with varying language skills. The 3 measures reflect accuracy, diversity (the tense marker total), and productivity (the tense and agreement productivity score [TAP score]) of the English tense and agreement system. Method: Measures were generated from language samples collected at the beginning and end of the participants' preschool year. Participants included 74 typically developing Spanish-English bilinguals and 19 peers with low language skills. The morpheme measures were evaluated with regard to their relationships with other language sample measures, their ability to reflect group differences, and their potential for capturing morphological development at group and individual levels. Results: Across both groups, the tense marker total and TAP scores were associated with other language measures and demonstrated both group differences and growth over time. The accuracy measure met few of these benchmarks. Conclusion: The tense marker total and TAP score, which were designed to capture emerging morphological abilities, contribute valuable information to a comprehensive language assessment of young bilinguals developing English. Case examples are provided to illustrate the clinical significance of including these measures in assessment.