SLA in a Nutshell
Willy A Renandya, 11 January 2026
Understanding how people learn a second language isn’t just theory. It’s the key to being a more effective and empathetic TESOL teacher. When you know how learners pick up new words, build confidence, and make sense of grammar over time, you can create lessons that truly connect with them.
This knowledge helps you avoid pushing too hard for perfection, focus on meaningful communication, and support each student’s unique journey, thus making your classroom a place where real learning (and even joy!) happens.
Summarized below are Rod Elis’ 12 principles of instructed second language acquisition.
- Develop Formulaic Expressions and Rule-Based Competence
Proficiency in a second language requires two mental systems: a memory-based system containing formulaic expressions (chunks like “What’s the matter?”) for high fluency, and a rule-based system (grammar) for constructing unique, complex thoughts. Early instruction should emphasize “survival language” and eventually help students “unpack” these chunks into flexible syntax and morphology.
- Focus Predominantly on Meaning
For acquisition to occur, learners must engage with pragmatic meaning, where they act as real people conveying real messages rather than just repeating prompts. The brain’s language processor is most effective when the focus is on achieving a communicative goal, often through Task-Based Language Teaching (TBLT),.
- Focus on Form
Pure immersion can lead to fossilization, where learners become fluent but continue making basic errors. Teachers should draw attention to specific linguistic features—grammar, vocabulary, and pronunciation—at the moment they are needed within a communicative context, either through planned tasks or incidental “recasts”,.
- Develop Implicit Knowledge while not Neglecting Explicit Knowledge
Implicit knowledge is the unconscious knowledge required for true fluency, while explicit knowledge consists of conscious rules. While implicit skills should be prioritized, explicit explanations help older learners “notice” complex structures and serve as a “monitor” for their speech.
- Take into Account the Learner’s “Built-in Syllabus”
SLA research shows that learners follow a natural, universal order of acquisition that is largely immune to instruction. Because you cannot force a learner to master a structure before they are ready, teachers should use a “cyclical” curriculum, moving on and returning to difficult points later when the student is developmentally ready.
- Require Extensive L2 Input
Acquisition requires massive exposure to the target language. This input must be “comprehensible,” meaning the learner understands the general message even if they don’t know every word. Teachers should maximize English as the medium of instruction and encourage extensive reading and listening programs outside of class.
- Require Opportunities for Output
If input is the fuel, output (speaking and writing) is the “engine”. Output forces learners to move from understanding meaning to understanding syntax, allows them to test theories about how language works, and helps “automatize” their knowledge through “pushed output”.
- Prioritize Interaction in the L2
Interaction is the “matrix” of learning. When learners engage in the Negotiation of Meaning—asking for clarification or confirming understanding—linguistic features become “salient” (noticeable), which triggers acquisition. Classrooms should use Information Gap tasks to mimic real-world social communication.
- Account for Individual Differences
Success is influenced by a learner’s profile, including aptitude, motivation, and learning style. No single method works for everyone; therefore, instruction must be diversified to include analytical, social, and visual/kinesthetic tasks to foster intrinsic motivation.
- Assess through Free as well as Controlled Production
Multiple-choice tests often only measure “controlled” or explicit knowledge. To measure true acquisition, teachers must evaluate free production, where the student’s mind is focused on the message rather than the linguistic form. This requires performance-based assessments like unscripted role-plays.
- Examine “Free” as Well as “Controlled” Production
Comprehensive evaluation must compare how a student performs when monitoring their speech versus when they are speaking naturally. A student’s variety and complexity in free speech is a far better indicator of their “interlanguage development” than their performance on a controlled grammar drill,.
- Focus on the Process of Learning, Not Just the Product
Instruction should prioritize the long-term psychological and social process of learning over just the final exam “product”. Teachers should use formative assessment to observe student engagement and strategy use, providing feedback that encourages trial and error rather than just punishing mistakes.
You can also watch a short video clip that captures the key points of Rod Elis’ ISLA Principles.
Reference
Ellis, R. 2014. Principles of Instructed Second Language Learning. In Celce-Murcia, Marianne, Brinton, Donna M., Snow, Marguerite Ann, David Bohlke (Eds.), Teaching English as a Second of Foreign Language, pp 31-45. Boston: Cengage Learning.