Second Language Acquisition (SLA). Krashen’s Six Hypotheses – Applications for Teaching

Stephen Krashen is an American professor at the University of Southern California, an expert in the field of linguistics, specializing in theories of language acquisition and development. Krashen states out a clear difference between language learning vs. acquisition. According to him, language learning is when we are thinking about the language, whereas acquisition is when we are using the language.

Acquisition requires meaningful interactions in the target language- natural communication- in which speakers are concerned not with the form of their utterances but with the messages they are conveying and understanding.

Therefore, Krashen‘s theory of second language acquisition (SLA) consists of six main hypotheses.

1. The Acquisition – Learning Hypothesis

Krashen makes a distinction between acquiring language and learning language. According to him, language that is learned is not the language that is really spoken. Krashen stresses out that there are two methods of developing language ability. Acquisition implies the subconscious acceptance of knowledge where information is stored in the brain through the use of communication. It is picking up or acquiring language through real, meaningful activities and interaction with other people. Learning, on the other hand, is the conscious acceptance of knowledge about a language, items such as grammar, style and form issues.

According to Krashen, language learning is a conscious process via a formal process (i.e., teachers explicitly teach grammar/ structure and students‘study). Therefore, it is about an “acquired system” or acquisition which is the product of the subconscious process, very similar to the process children undergo when they acquire their first language and “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. (Krashen, Stephen D. Second Language Acquisition and Second Language Learning, 1988)

1. 1. Applications for Teaching
According to the acquisition- learning theory, the best method a language is learned is through natural communication. For second language learning, the teacher should come up with a context where in language is used to
fulfil authentic purposes.

2. The Monitor Hypothesis

Krashen states that when people talk or write in their second languages, they produce only the language they have acquired, not the language they have learned. This hypothesis provides details about how acquisition and learning are used. The acquired system” or acquisition initiates and utterance and “the learned system” or learning monitors the utterances to check and correct errors. A second language learner will use the monitor hypothesis   when   he/she   is   writing   or   talking. Monitor means that second language learners can self-correct or self-repair.  Krashen suggests that learners must have knowledge through learning, they know how to apply rules. He asserts that learning is important so that people can monitor the language they produce. According to Krashen the role of the monitor should be minor, being used only to correct deviations from normal speech. Therefore, he identifies  three  categories  of  learners, over users those  who  use  the monitor all  the  time, under users those who have not learned or prefer not to use their conscious knowledge, and optimal users those who properly use monitor.

2. 1. Applications for Teaching
Second language teachers are always challenged to find out a balance between encouraging accuracy and fluency in their students. However, finding a balance depends on several variables, such as the aims of the lesson, the language level, the personal goal of each student.

3. The Natural Order Hypothesis

According to Krashen, there are two ideas to this hypothesis:
Acquisition of grammatical structures follows a natural order which is predictable and mimics that of first language acquisition. Second languages are acquired through 4 stages in the same way that first languages are acquired:
a. The preproduction stage (the silent period)
b. The early pre-production stage
c. The speech emergence stage
d. The intermediate fluency stage

3. 1. Applications for Teaching
According to this hypothesis, teachers should take into account that certain structures of a language are easier to acquire than others. Thus, second language teachers should teach these language structures in an order that is conducive to learning. At first, teachers should be introducing language structures that are relatively easy for learners, according to their language level, and then use scaffolding to introduce more difficult

4. The Reading Hypothesis

This hypothesis points out the fact that the more we read in a second language, the greater our vocabulary will be.

4. 1. Applications for Teaching
Second language teachers should be aware of the importance of involving students   in   reading   in   the language classroom to enrich their vocabulary and knowledge and the way it is used in real-life contexts.

5. The Input Hypothesis

This hypothesis emphasizes the fact that language acquisition occurs when students get comprehensible input in the second language. Krashen argues that the input received must not be only comprehensible but also slightly beyond the learner‘s current level of competency. This concept is represented as i+1, with I standing for comprehensible input. Second-language acquisition theory provides a very clear explanation   as   to   why   immersion   works.

According to current theory, we acquire language in only one way: when we understand messages in that language, when we receive comprehensible input. (Krashen, Stephen D. The Input Hypothesis: Issues and Implications, 1984:61)

5. 1 Applications for Teaching
Within a class, this hypothesis points out to the fact that using the target language in the
classroom is vital. The aim of any class for learners is to be able to develop their language skills. Teachers can make input comprehensible by using visuals, realia, objects, gesturing, modeling,   charts, graphs, maps, crosswords, etc.

6. The Affective Filter Hypothesis

However, a comprehensible input is not the only ingredient needed in the language acquisition process. Three compulsory aspects need to be taken into account and represent success in language acquisition motivation, self-esteem, anxiety, the lower the anxiety, the better the language acquisition; for language acquisition to succeed, anxiety should be zero. How can these aspects be transferred into language acquisition? If a student is not motivated, self-esteem is low, anxiety is high, he/she is under defensive, and thinks that language class is a place where his/her weaknesses are going to be revealed, he/she may understand the input, but it will not penetrate, it will not reach those parts of the brain that do language acquisition. A block keeps it out, and this block is called the affective filter.

6. 1. Applications for Teaching
A safe and welcoming environment is the keystone aspect of a student‘s educational success. In language classrooms, this aspect plays a great role, as learners need to feel comfortable when   trying   to produce some language and taking risks.


  • Jiang, N. Lexical Representation and Development in a Second Language. Applied Linguistics, 2000
  • Krashen, Stephen D. Second Language Acquisition and Second Language Learning. Prentice-Hall International, 1988
  •  Krashen, Stephen D. The Input Hypothesis: Issues and Implications. Longman Publishing Group, 1984
  • Krashen, Stephen D. Principles and Practice in Second Language Acquisition. Prentice- Hall International, 1987
  • Segalowitz, N. Automaticity and Second Languages. In: Doughty, C. J. & Long, M. H. (eds). The Handbook of Second Language Acquisition. Oxford: Blackwell, 2003


prof. Ana Scrob

Liceul Teoretic Creștin Pro Deo, Cluj-Napoca (Cluj) , România
Profil iTeach:

Articole asemănătoare