Publication Date

2014-12-02

Availability

Open access

Embargo Period

2014-12-02

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PHD)

Department

Teaching and Learning (Education)

Date of Defense

2014-07-25

First Committee Member

Maria S. Carlo

Second Committee Member

Soyeon Ahn

Third Committee Member

Batya Elbaum

Fourth Committee Member

Mary Avalos

Abstract

This systematic review provides a comprehensive analysis of the empirical literature on the effectiveness of vocabulary instructional methods for English language learners (ELLs) in prekindergarten through 6th grade settings. Thus, a central goal of this study is to appraise the available research on vocabulary learning and assess intervention studies’ levels of evidence for effectiveness in order to make a critical assessment of the variables that are currently represented in the field. Specifically, the research questions guiding this systematic review are: (1) How do intervention studies developing L2 word-meaning acquisition with ELLs in pre-kindergarten through 6th grade settings vary in their methodological characteristics (i.e., research design, learners, instructional design and outcome)? (a) What are the studies’ levels of evidence for effectiveness based on their design and outcome characteristics? and (2) What is the impact of studies that meet requisite evidence standards on learners’ L2 word-meaning acquisition? A total of 18 studies meeting the inclusion criteria were identified. Independent coding of 20% of the articles (n=4) was completed, the results were cross-checked against the original codes, and further discrepancies in coding were resolved through discussion between the two coders. The final criteria were subsequently reapplied by the author to all studies in the review. Coding categories for each study were organized by four main characteristics: (1) design characteristics (i.e., random assignment, baseline equivalence, comparison group type); (2) learner characteristics (i.e., L1/L2 proficiency, SES, age and grade level); (3) treatment characteristics (i.e., focus of instruction, level of L1 support, word tier targeted, total instructional time, training, explicitness of instruction, contextual/definitional support, group size, and level of word exposure) and (4) outcome characteristics (i.e., outcome objective, type of measure, type of ability measured, modality, word tier assessed, and type of knowledge). Based on the studies’ design and outcome characteristics, their level of evidence for effectiveness was also examined. Subsequent analyses revealed that a large proportion of studies underreported information and did not meet evidence standards for effectiveness. Additionally, studies with available effect sizes for measures of breadth and depth of vocabulary knowledge revealed inconclusive evidence about the best instructional practices for ELLs due to the large variations among a limited number of studies in their instructional approach, learners, and outcome characteristics. An analysis of the merits and limitations of the reviewed studies reveals a number of methodological problems that threaten the validity and credibility of vocabulary research. These findings highlight the need for increased research in this field of study, particularly in revisiting existing practices to add to current understandings relating to vocabulary practices with ELLs. Additionally, this study points to specific issues in current research and provides recommendations for researchers seeking to address the significant knowledge gap in research that is centered on ELL vocabulary learning.

Keywords

vocabulary learning; word-meaning acquisition; bilingual learners; English language learners; systematic review

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