The 5 hypotheses of Krashen's Theory of Second Language Acquisition
Krashen's theory of second language acquisition consists of five main hypotheses:
- the Acquisition-Learning hypothesis;
- the Monitor hypothesis;
- the Input hypothesis;
- and the Affective Filter hypothesis;
- the Natural Order hypothesis.
1. The Acquisition-Learning distinction is the most fundamental of the five hypotheses in Krashen's theory.
According to Krashen there are two independent systems of foreign language performance: 'the acquired system' and 'the learned system'.
The 'acquired system' or 'acquisition' is the product of a subconscious process very similar to the process children undergo when they acquire their first language. It requires meaningful interaction in the target language - natural communication - in which speakers are concentrated not in the form of their utterances, but in the communicative act.
The "learned system" or "learning" is the product of formal instruction and it comprises a conscious process which results in conscious knowledge 'about' the language, for example knowledge of grammar rules.
A deductive approach in a teacher-centered setting produces "learning", while an inductive approach in a student-centered setting leads to "acquisition".
According to Krashen 'learning' is less important than 'acquisition'.
2. The monitoring function is the practical result of the learned grammar. According to Krashen, the acquisition system is the utterance initiator, while the learning system performs the role of the 'monitor' or the 'editor'. The 'monitor' acts in a planning, editing and correcting function when three specific conditions are met:
- The second language learner has sufficient time at their disposal.
- They focus on form or think about correctness.
- They know the rule.
3. he Input hypothesis is Krashen's attempt to explain how the learner acquires a second language – how second language acquisition takes place.
The Input hypothesis is only concerned with 'acquisition', not 'learning'.
According to this hypothesis, the learner improves and progresses along the 'natural order' when he/she receives second language 'input' that is one step beyond his/her current stage of linguistic competence. For example, if a learner is at a stage 'i', then acquisition takes place when he/she is exposed to 'Comprehensible Input' that belongs to level 'i + 1'.
4. The Affective Filter hypothesis embodies Krashen's view that a number of 'affective variables' play a facilitative, but non-causal, role in second language acquisition.
These variables include: motivation, self-confidence, anxiety and personality traits. Krashen claims that learners with high motivation, self-confidence, a good self-image, a low level of anxiety and extroversion are better equipped for success in second language acquisition.
Low motivation, low self-esteem, anxiety, introversion and inhibition can raise the affective filter and form a 'mental block' that prevents comprehensible input from being used for acquisition.
In other words, when the filter is 'up' it impedes language acquisition. On the other hand, positive affect is necessary, but not sufficient on its own, for acquisition to take place.
5. Finally, the less important Natural Order hypothesis is based on research findings which suggested that the acquisition of grammatical structures follows a 'natural order' which is predictable. For a given language, some grammatical structures tend to be acquired early while others late.
Krashen points out that the implication of the natural order hypothesis is not that a language program syllabus should be based on the order found in the studies. In fact, he rejects grammatical sequencing when the goal is language acquisition.
