Krashen’s Input Hypothesis rightly puts understood input at the centre. The strong version (input is the only route; learning never becomes acquisition) fails: immersion learners understood a great deal but kept persistent grammatical errors. Input is the engine, not the whole car.
The argument
- Krashen (early 1980s): acquisition via i + 1; the acquisition/learning distinction.
- Canadian French immersion: strong comprehension, weak accuracy → Swain’s Output Hypothesis.
- Schmidt’s noticing: input must be attended to.
- i + 1 can’t be measured, so the hypothesis is hard to test.
- “Teachers who swallow it whole end up with learners who understand a great deal and can say very little.”
Moves
Grade your language (slow, repeat, rephrase) without removing all unfamiliar items; context (visuals, gesture, realia); extensive reading and listening for volume; check comprehension with questions, not nods; push output and give form feedback.
Where sources disagree
Steve Smith treats CI as “the main driver”; Conti floods input but structures it; Weller adds output and noticing. These are differences of degree, not kind. Everyone in the vault agrees input is necessary.
Connections
Teaching is the management of attention · MARS-EARS - the EPI instructional sequence · Why L2 listening is hard - cognitive and affective barriers · Topic - SLA Theories Map