Second Language Acquisition and Development
What Domain II Covers
This domain asks how additional languages are acquired and what that means for K-12 classrooms: theory, stages, individual differences, and the BICS/CALP distinction that drives service decisions.
Core Concepts
- Krashen's monitor model: acquisition vs. learning, comprehensible input (i + 1), natural order, monitor, and affective filter. Useful as a teaching heuristic, but the hypotheses are not precisely measurable and have been criticized for weak empirical support.
- Cummins: BICS (conversational fluency) typically develops in about 2–3 years; CALP (academic language proficiency) takes roughly 5–7 years and depends on prior schooling and literacy in the L1.
- Interlanguage (Selinker): the learner's rule-governed interim system, shaped by L1 transfer, overgeneralization, and instruction. Persistent plateaus are fossilization.
- Errors vs. mistakes (Corder): errors reflect the underlying system and are informative; mistakes are slips the learner can self-correct.
- Stages: pre-production (silent period), early production, speech emergence, intermediate fluency, advanced fluency.
- Other theory: Swain's output hypothesis, Long's interaction hypothesis, Vygotsky's ZPD and scaffolding, and communicative competence (grammatical, sociolinguistic, discourse, strategic).
Worked Example
A fourth grader who arrived two years ago chats fluently at recess but scores poorly on expository writing and science explanations. Reasoning: her BICS is well developed while CALP is still emerging, which is a normal trajectory, not evidence of a learning disability. The right response is continued sheltered content instruction with explicit language objectives and writing scaffolds, not immediate exit from services or special education referral.
Traps
Equating playground fluency with academic proficiency; interpreting a silent period as defiance; correcting every utterance and raising the affective filter; calling all errors "interference"; assuming younger learners are always faster - older learners often progress faster in morphosyntax, while younger starters tend to achieve more native-like pronunciation.