The Bilingual Advantage: Assessing the Impact of Proficiency Levels

Date of Submission

Spring 2026

Document Type

Closed Research Project

Degree Name

Master of Science in Speech-Language Pathology

Department

Speech-Language Pathology

First Advisor

Beatriz Barragan, PhD

Abstract

This study examined whether bilingual proficiency, defined by the number of translational equivalents (TE) produced during a semantic fluency task, influences executive function and working memory performance in Spanish-English bilingual adults. While the bilingual advantage hypothesis suggests that lifelong management of two languages enhances executive control, inhibitory control, cognitive flexibility, and memory, prior research remains mixed, partly due to treating bilinguals as a uniform group without accounting for proficiency differences. Forty-one Spanish-English bilingual adults (ages 19–43) completed the LEAP-Q, a bilingual semantic fluency task (mean TE = 18.7), and a cognitive battery assessing inhibitory control (Flanker task), cognitive flexibility (Switching task), and working memory (Digit Span, Hand Movement, and Non-Word Repetition tasks). Participants were classified into high-TE (n = 19, above mean) and low-TE (n = 22, below mean) groups based on translational equivalents.  Results revealed no significant group differences on any working memory measures. However, the high-TE group showed significantly higher accuracy on the Flanker task and a clear performance advantage on the Switching task (in both accuracy and reaction time), reflecting superior inhibitory control and cognitive flexibility. These advantages were selective to higher-order executive functions. The findings indicate that bilingual cognitive advantages are not universal but primarily appear among bilinguals with high, balanced proficiency in both languages. This study helps resolve inconsistencies in the literature and highlights important implications for education and clinical practice. Speech-language pathologists and educators should assess proficiency in both languages when interpreting executive function performance and promote high bilingual mastery to optimize cognitive benefits, while administering assessments in both languages to reduce misdiagnosis risk in lower-proficiency bilinguals.

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