Abstract

This study examined whether a complexity-based expressive morphosyntactic intervention targeting auxiliary BE questions improves morphosyntactic, vocabulary, and narrative comprehension in adolescents with Down syndrome (DS). Two participants (ages 15;11 and 14;2) received intervention delivered over 15 and 12 sessions, respectively, using a structured narrative-based protocol. Comprehension was assessed pre- and post-intervention using the Clinical Evaluation of Language Fundamentals-Fifth Edition (CELF-5) Following Directions subtest, the Peabody Picture Vocabulary Test-Fifth Edition (PPVT-5), the Test of Narrative Language-Second Edition (TNL-2), and the Test of Early Grammatical Impairment (TEGI) Grammaticality Judgment (GJ) task. Results indicate no reliable or clinically significant improvements in comprehension across the broader standardized measures, as reflected by stable scaled scores and reliable change index values. Although small increases in raw scores were observed, these changes did not generalize to standardized measures. However, the more sensitive TEGI GJ task captured meaningful but limited gains in specific morphosyntactic structures, suggesting emerging sensitivity to grammatical forms directly related to the intervention targets. These findings suggest that expressive morphosyntactic intervention alone may not be sufficient to produce measurable changes in comprehension when comprehension is not directly targeted. Results highlight the importance of measurement sensitivity, intervention duration, and participant factors when evaluating language outcomes in adolescents with DS.

Degree

MS

College and Department

David O. McKay School of Education; Communication Disorders

Rights

https://lib.byu.edu/about/copyright/

Date Submitted

2026-05-28

Document Type

Thesis

Keywords

Down syndrome, complexity approach, language comprehension, morphosyntax, language intervention

Language

english

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