The Impact of Bilingual vs English-Only Instruction on the Performance of Undergraduate Saudi Medical Science Students.

Introduction: Using English as the medium of instruction in science courses may hinder comprehension for students who lack sufficient English language proficiency. This challenge is particularly relevant in non-English speaking countries, where students may struggle to follow complex scientific content delivered exclusively in English. Methods: This study was conducted at King Saud bin Abdulaziz University for Health Sciences, where the majority of students are native Arabic speakers. To assess the impact of language on knowledge acquisition, two groups of first-year students enrolled in various health and medical science majors were compared. The test group attended a biology lecture delivered bilingually (Arabic and English), while the control group received the same lecture in English only. A pre- and post-test design was used to evaluate knowledge acquisition during the lecture session. Results: Both groups showed improvement in post-test scores; however, the test group demonstrated a statistically significant higher gain compared to the control group. Furthermore, 86% of students in the test group reported that the bilingual approach reduced distractions, and 98% reported improved understanding. In contrast, only 32% of the English-only group reported reduced distractions, and 56% felt it improved their understanding. Discussion: The findings suggest that bilingual instruction enhances comprehension and reduces cognitive load for students with limited English proficiency. This highlights the importance of adapting the medium of instruction to student language competencies in science education, especially for non-native English speakers, who lack sufficient English language skills.