Second Language Acquisition (SLA) Theories Applied in ESL Teacher Training

The incorporation of Second Language Acquisition (SLA) theory into English as a Second Language (ESL) teacher education is essential for preparing teachers who make research-informed instructional decisions. SLA frameworks such as the input hypothesis, interaction hypothesis, sociocultural theory, and cognitive processing models are extensively cited in professional standards and program curricula, yet their impact on practical teacher preparation varies. This systematic literature review synthesizes 62 empirical and conceptual studies published between 1980 and 2024, examining how SLA theories inform ESL teacher training, with attention to curriculum design, pedagogical skill development, teacher cognition, and practicum supervision. Searches across Scopus, Web of Science, JSTOR, ERIC, and Google Scholar initially generated 2,314 records, which were screened using PRISMA guidelines. Results reveal six key areas where SLA theory shapes teacher preparation. These primarily involve input-based instruction, interactionist and task-based approaches, cognitive and noticing frameworks, sociocultural mediation, usage-based perspectives, and formal linguistic theories. Despite this theoretical foundation, a theory-practice gap persists, as teacher trainees often struggle to apply SLA constructs during lesson planning, feedback, and classroom interface. This review then recommends systematic curriculum integration, scaffolded mentorship, reflective practice, and professional development to ensure SLA theory functions as an active component of ESL teacher preparation.