Second language acquisition and learner characteristics
Theories to compare
Behaviourism (habit formation, drills, contrastive analysis) gave way to cognitivist views of an internal syllabus. Krashen's monitor model offers five hypotheses: acquisition/learning, natural order, monitor, input and affective filter; it is a useful shorthand but empirically contested. Add Swain's output hypothesis, Long's interaction hypothesis, Schmidt's noticing hypothesis, and Vygotsky's zone of proximal development with scaffolding. Sociocultural and identity-based views treat learning as participation in communities.
Interlanguage and error
Selinker's interlanguage is a rule-governed developing system that is neither L1 nor L2. Errors are systematic; mistakes are slips. Sources include interlingual transfer, intralingual overgeneralisation, communication strategies and teaching-induced error. Fossilisation describes stabilised plateaus.
Learner characteristics
Consider age and the critical period (stronger for phonology than syntax), aptitude, motivation (integrative/instrumental, intrinsic/extrinsic, Dörnyei's ideal and ought-to L2 selves), anxiety, willingness to communicate, strategies versus styles, autonomy and multilingual identity.
Traps
Claims that matching learning styles to tasks improves outcomes are not well supported. Krashen's model is a set of hypotheses, not settled fact. The critical period is not an absolute barrier for adult learners. Many errors labelled 'L1 interference' are in fact developmental.
Worked example
A learner says 'I goed'. This is overgeneralisation of the regular past, not transfer, so it is evidence of rule learning: respond with a recast and keep using the form in context rather than drilling 'went' as if no rule existed.