People often assume that teaching through English automatically helps students “go global”. But what if using only English in complex subjects like biology actually hinders learning? A 2025 study by Aiman Alhazmi & Mohammed Alzahrani at King Saud bin Abdulaziz University for Health Sciences challenges this assumption in fascinating ways.
The Study
Researchers compared two groups of first-year Saudi medical science 1students, all native Arabic speakers with similar English proficiency levels.
- Group 1 (Bilingual): A biology lecture delivered in English & Arabic (scientific terms remained in English).
- Group 2 (English-only): The same lecture taught entirely in English. Both groups took a pre-test & post-test, & completed a perception survey.
The Findings
Both groups improved after the lecture, but the bilingual group’s performance gain was significantly higher. On new, unseen test questions, bilingual students also outperformed their peers. Even more striking were the perceptions:
- 98% of bilingual-group students said the dual-language approach improved their understanding.
- Only 56% in the English-only group said the same.
- 86% of bilingual students said the mixed-language lecture reduced distractions, compared with just 32% of the English-only group.
Why It Matters
The findings make perfect sense through Cognitive Load Theory (Sweller, 1988). Processing complex information in a second language taxes working memory, leaving less capacity for actual learning. Using the first language can lighten that load, freeing up cognitive resources for understanding new concepts.
This also aligns with Cummins’ (1979) Common Underlying Proficiency Hypothesis—the idea that strong L1 skills support L2 academic learning. In other words, Arabic didn’t “interfere” with English; it scaffolded it. Similarly, Vygotsky’s Sociocultural Theory suggests that L1 provides a bridge for meaning-making within the learner’s zone of proximal development.
A Broader Shift
Globally, English Medium Instruction (EMI) has expanded rapidly (Macaro et al., 2018), often justified by internationalisation goals. Yet this study reminds us that language policy isn’t neutral—it directly shapes comprehension, participation & equity. Research in multilingual classrooms (e.g. García & Lin, 2016; Nhongo & Tshotsho, 2019) increasingly highlights translanguaging as a powerful pedagogical tool rather than a crutch.
Teacher Takeaways?
- Use L1 strategically: Allowing students to clarify or discuss complex concepts in their first language can enhance rather than hinder English development- even in an ELT classroom
- Scaffold cognitive load: Present key terms in English, but explain concepts in the students’ L1 when needed—especially in STEM or abstract content areas.
- Encourage translanguaging: Invite learners to connect both linguistic systems through note-taking, group work, or bilingual glossaries.
As English educators, we often face the “English-only vs bilingual” dilemma. This research suggests it’s not a zero-sum game—our students’ first languages might be one of their most powerful learning tools.
Do you ever use students’ first languages to support learning in your classes?
- Men only, I’m afraid. According to the researchers, “The reason only male students were included is that the university has separate campuses for male and female students, which is aligned with local cultural and educational norms, and the researchers are instructors at the male campus.” ↩︎
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