Theories in Second Language Acquisition: An Introduction

10 Observations of SLA

Originally Long (1990) but shortened and presented here:

  1. Exposure to input is necessary for SLA
  2. A good deal of SLA happens incidentally
  3. Learners come to know more than what they have been exposure to in the input
  4. Learner's output often follows predictable paths with predictable stages in the acquisition of a given structure
  5. Second language learning is variable in its outcome
  6. Second language learning is variable across linguistic subsystems
  7. There are limits on the effects of frequency on SLA
  8. There are limits on the effect of a learner's first language on SLA
  9. There are limits on the effects of instruction on SLA
  10. There are limits on the effects of output on language acquisition


The idea language acquisition is based upon positive or negative reinforcement (Pavlovian), which lead to language habits forming or the extinction of bad habits. Frequency of feedback is important. Ideal learning is when language models are plentiful and feedback is immediate.

Subscribes to Constrastive Analysis idea that similar languages are easy to acquire. Pairs with Structural Linguistics view that language is a finite set of blocks that can be rearranged in a finite number of ways.

Widely disregarded.

Monitor Theory

From Krashen, father of modern SLA thinking. Language acquisition is biological aspect of humans.

  • Acquisition hypothesis: acquisition (naturalistic, occuring from L2 use) and learning (explicit, book-learning) are distinct areas of cognition, do not interact
  • Monitor hypothesis: Learning (or Monitoring) is only useful in set, non-timed situations. Otherwise acquisition is better for natural use/communication
  • Natural order hypothesis: Language aspects are learnt in a set type of natural order. Contentious.
  • Input hypothesis: Acquisition is optimised when one is acquiring at: i + 1, where i is current L2 level and 1 is incrementally difficult/novel
  • Affective filter hypothesis: Learners who are comfortable and positive are less filtered and therefore more open to acquisition. Stress raises this filter and harms acquisition.