Graduation Year

2026

Document Type

Dissertation

Degree

Ph.D.

Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Language, Literacy, ED.D., Exceptional Education, and Physical Education

Major Professor

Sara A. Smith, Ph.D.

Co-Major Professor

Maria S. Carla, Ph.D.

Committee Member

Sanghoon Park, Ph.D.

Committee Member

John Ferron, Ph.D.

Keywords

Linguistic Complexity, Oral Language Production, Spanish-Speaking English Learners, Vocabulary Diversity, Vocabulary Instruction

Abstract

As fourth-grade students transition from learning to read to reading to learn, their ability to use language for academic purposes becomes increasingly important, particularly for Spanish-speaking English Learners (ELs). However, students often have limited opportunities to produce extended oral language during instruction. Students’ oral language production reflects both structural aspects of language use, captured through measures of linguistic complexity, and lexical aspects of language use, captured through measures of vocabulary diversity. Although prior studies have examined transcript-derived measures of oral language production, limited research has examined how these measures predict English proficiency, capture growth over time, and respond to different instructional conditions among Spanish-speaking ELs.

This study examined whether transcript-derived measures of linguistic complexity and vocabulary diversity produced during instructor–student instructional conversations predicted English proficiency among fourth-grade Spanish-speaking ELs. The study also examined growth across a six-week instructional period and the responsiveness of these measures to instructional condition. Participants engaged in remote synchronous one-on-one vocabulary instruction under either a mixed-language condition (Spanish and English) or a single-language condition (English only). Linguistic complexity was operationalized using mean length of utterance in words and morphemes (MLU-w and MLU-m), while vocabulary diversity was measured using Type–Token Ratio (TTR), VOCD, and Moving-Average Type–Token Ratio (MATTR), including both word-based and lemma-based approaches. Multilevel models were used to examine predictive relationships between transcript-derived measures and English proficiency outcomes on the Woodcock–Muñoz Language Survey–Revised Normative Update (WMLS–R NU) subtests, as well as patterns of growth over time.

Results indicated that among measures of linguistic complexity, MLU-m emerged as the strongest predictor of expressive vocabulary knowledge, as measured by the Picture Vocabulary subtest. Among vocabulary diversity measures, MATTR and VOCD, particularly lemma-based and length-adjusted approaches, demonstrated more stable predictive relationships across models, whereas TTR showed greater variability across analyses. Associations with Passage Comprehension were weaker and less consistent overall. Growth models indicated small, non-significant slopes across measures of linguistic complexity and vocabulary diversity, suggesting relative stability in students’ transcript-level oral language production over the six-week instructional period. Additionally, no statistically significant differences in growth trajectories were observed between instructional conditions.

Findings support the use of transcript-derived measures of linguistic complexity and vocabulary diversity as predictors of English proficiency outcomes among Spanish-speaking ELs. Findings also highlight the importance of operationalization and measurement decisions when assessing oral language production and suggest that short-term differences in instructional language support may not immediately manifest in transcript-level language outcomes.

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