Krashen’s SLA Theory


One of the great gifts that humans are equipped with is the ability to learn language. Krashen describes language learning as a cognitive behavior that takes place within a traditional classroom. In this classroom, the teacher is the central focus and the learners take a passive role. Accordingly, it is the teachers’ role to transmit information and rules about the language; the students’ roles are to manipulate that information and produce correct utterances. This classroom follows a mandated syllabus and classroom activities that focus mainly on written forms of a language. It is the students’ role to deduce the syntax and grammatical rules of the language from what the teacher is presenting them with. It is then believed that students who focus on syntax and phonics will be able to transfer this information into their mental departments for later usage.  With some practice, many are able to learn a second or third language. Often the method of learning the second language is a little more complicated than the first language. According to Krashen, the main purpose of language is communication. This concept goes hand and hand with teaching because a good teacher must be able to communicate with his/her students. Krashen’s theory was introduces over 20 years ago and has been widely influential in the training of aspiring Language Arts teachers around the world. Krashen’s theory of second language acquisition consists of five hypotheses: the acquisition-Learning Distinction, the monitory hypothesis, the natural order hypothesis, the input hypothesis, and the affective filter hypothesis.

Acquisition of Language Hypothesis         

The acquisition learning theory is the most fundamental of the five parts and is most widely known and accepted by linguistics. The acquisition learning hypothesis conveys that adults have two distinct ways of learning which are acquisition-subconscious and learning –conscious (Gregg, p.79). The acquired is subconscious knowledge. The acquisition part is a product of the sub-conscious and very similar to the process a young child goes through in learning to speak. Nonetheless, it does require interaction with the target language. In other words, the second language learner must have adequate time and practice with the new language.  According to Corder, “While classwork is directly aimed at increasing conscious linguistic knowledge of the target language, to the extent that the target language is used realistically, affects the extent to which acquisition will  occur” (p. 47). Elizabeth Tricomi adds,

“Chief among techniques to avoid when teaching acquisition is the use of error based exercises. These exercises require students to choose the correct form out of several incorrect alternatives or to locate and correct the errors of grammar, punctuation, or usage in a passage. Through their input of erroneous or nonstandard forms, such as exercises impede rather than promote students’ acquisition of standard forms. Instead of teaching students, they merely test whether they are able, thorough either acquired or learned competence, to supply the correct forms.” (p. 63).

She suggests that teachers use the students’ own papers when teaching acquisition. However, rather than labeling their errors, the teacher should discuss and clarify errors.

Also, according to acquisition theory, adults learn a second language in two distinctive ways: subconscious and conscious. Krashen reminds that adults never lose the ability to learn language as children do. Krashen goes on to point out that there are three ways learning may contribute to acquisition. First, the learner may produce his/her own comprehensive input through the language acquisition device. Secondly, as the learner’s knowledge of rules increase, so will his/her comprehension ability. Finally, learning a second language is often an emotional journey; therefore, the learner’s lower affective filter may be affected resulting in more input being available for acquisition.  One distinction between the acquisition and learning is the limited role for grammar and error correction.

Krashen conveys that learning the formal knowledge of language as it is connected to the knowledge of rules has a great deal to do with implicit and explicit learning. According to Krashen, some experts believe that children acquire language while adults learn language. However, Krashen disagrees. He believes that when the learner is engaged in the communication of a language, he/she will acquire that knowledge. (Ellis, p. 261). Nonetheless, Krashen also believes that learned knowledge is separate and cannot be converted into acquired knowledge.  This is supported by his belief that the two types of knowledge are housed in different portions of the brain.  The knowledge that a person has of his/her first language is said to be implicit. “Implicit knowledge of a language is said to be intuitive and cacti and it cannot be directly reported.” (Ellis, 1994). Implicit knowledge is comprised of formulaic knowledge and rule based knowledge. Formulaic knowledge consists of fragments of language and rule based consists of generalized abstracts structures which the learner has internalized (Ellis, 1994). According to MacWhinney, in order to accept Krashen’s theory of the contrast between learning and acquisition, one must be able to prove that explicit instruction is unnecessary or counterproductive (p. 277-78). MacWhinney goes on to say that explicit instruction and explicit learning are two separate entities, and explicit instruction will not necessarily lead to explicit learning.  According to Green & Hecht, 1992, “Explicit instruction works best for clear, simple structures” (p. 170). Krashen supports this belief because he believes that language acquisition is mostly intuitive.

The Monitory System

            This hypothesis builds on the acquisition learning by allocating functions to separate systems within the larger system. Krashen says that only the acquisition can initiate utterances, learning functions as an editor for these performances (1982). The monitory system hypothesis describes the relationship between learning and acquisition. Accordingly, learning influences acquisition. The role of the conscious is limited in this process. Consequently, the learner must have adequate practice time at his/her disposal.  The monitor system is the application of formal rules. McLaughlin argues that it is difficult to prove that the Monitor exists. He says,

“People have rules for language use in their heads, but these rules are not those of the grammarian. People operate on the basis of informal rules of limited scope and validity. These rules are sometimes conscious and sometimes not, but in any given utterance it is impossible to determine what the knowledge source is.” (p. 30).

According to Burden, “In order that the Monitor may work, three principal conditions must be met. They are: the monitor needs time, a focus on form and an appropriate knowledge of the rule” (p. 194). The acquisition of language is not an overnight process; therefore the learner and teacher should have reachable goals and expectations.

Natural Order Hypothesis

This hypothesis deals with grammatical structure. There is a distinction between competence and performance (Anderson, 1980). Anderson goes on to that that accuracy deals with behavior, while acquisition deals with knowledge. He does not feel that performance is an accurate indicator of competence (p. 17-20). For any given language, some skills will take longer to acquire than others because knowledge is obtained in a predictable way and instruction usually does not alter that process. The natural order commands the way in which a language is assimilated, but learning might follow another order (Wilson, 2000). Many critics have evaluated the morpheme studies which were conducted by Roger Brown in 1973. He concluded that children typically had certain morphemes imbedded into their speech between the ages of 2-4. For the reason, many critics disagree with Krashen’s belief that adults will learn a second language in the same manner that small children learn their first language (Hakuta, p. 298). White argues that grammar instruction will increase the rate and accuracy of the learner when it is appropriate to the learner’s stage of development (p. 98). Although there is some controversy about the ways knowledge of the language is learned, most critics agree that it must be presented on a steady basis.

Input Hypothesis

The input hypothesis seeks to answer how a learner becomes competent over a period of time and focuses mainly on the acquiring of knowledge, but not the actual learning. In order to move from one point to the next, the learner must have comprehensive input. Consequently, one only learns what he/she understands.  Krashen said, “All other factors thought to encourage or cause second language acquisition work only when they contribute to comprehensible input/or low affective filter.” (p. 4). Learners move from their current level of learning to the next through understanding. Once they gain competence in using context, their accuracy will increase. As a result, an observer can expect to see what Krashen calls the “silent period” when dealing with language learners.  Accordingly, second language learners usually speak very little of the second language for several months (Romeo, 2000). During this silent period language learners are acquiring the skills to produce the new language. Once they have gained the competence, they will begin to produce the language. Krashen believes, “In accordance with the Input Hypothesis, speaking ability emerges on its own after enough competence has been developed by listening and understanding” (Gregg, p. 90).

Affective Hypothesis Filter

Krashen believes that the number of affective variables plays a viable role in the acquisition of the second language. According to Krashen, humans are designed with a mechanism that determined how much comprehension can be obtained. A high filter obstructs the comprehension.  Anxiety, stress, self-confidence, and motivation are variables that affect second language acquisition by limiting input. Individuals with low motivation will not have the same amount of time committed to learning the language as those with high motivation; as a result they will likely receive less input (Ellis, p. 100). Krashen believes that learners with high motivation, self-esteem, self-confidence, and low anxiety will perform better at learning a new language. A combination of low motivation and anxiety can raise the affective filter and cause a mental block towards the learning of the new language. Simply put, a high affective filter stops acquisition, while a low affective filter encourages acquisition. According to Krashen, this filter is present in adults but not in children, and is directly linked to the failure to learn a second language (MacIntire & Gardner, p. 255 ). Accordingly, McLaughlin suggests that learning a second language is more feasible when a person in young. He adds that Krashen has “provided no coherent explanation for the development of the affective filter and no basis for relating the affective filter to individual differences in language learning” (p. 56). McLaughlin conveys that the drive to learn a new language resides within the person, regardless to age.

The Critics

Gregg disagrees with Krashen’s insistence that learning cannot become acquisition. He believes that anyone who has experienced internalized grammar that they previously memorized would refute this portion of Krashen’s hypothesis too. He based his information on the experience he had when learning the English language.  He said that he learned rules of grammar by memorizing charts provided to him by his teacher. He says that he was able to produce grammatically correct sentence within days with no input other than the grammar drills (p. 80-82). He goes on to say that Krashen should not separate grammatical morphemes from phonology and syntax because they are too similar in nature.

According to Schultz, Krashen’s theory is too complex. It is difficult for him to understand why Krashen used to completely separate systems: one for acquisition and one for learning. He feels the idea of two systems is possible, but improbable. He believes this set up would not be an efficient way for humans to store information. He also goes on to express that he doesn’t feel that Krashen adequately explains the acquisition process, and why learned information is not accessed in the same way as acquired information (p. 18-25).

According to Elizabeth Taylor the results of the morpheme studies the often observed phenomenon of language learners ability to complete grammar exercises perfectly, but are still unable to transfer that knowledge into speaking. In her opinion, the formal study of grammar does not improve the language learners speaking ability. These findings are supported by William Labov’s observation of African-American speakers who learned Standard English later in life. Many African-American people grew up speaking non-standard English. As a result, when they are tired or distracted they usually revert back to that non-standard form of speaking (Tricomi, p. 61). This type of speaking is the product of rote memory of grammar drills. When speaking, people who have learned in this way are usually meticulous and robotic like in speaking.

Implication for Mediators

            Good teachers make classroom instruction comprehensible for both native and ESL students. When this is done correctly, ESL students are learning content while acquiring the English Language as well. Many ESL students are nervous and anxious in the general education classroom; therefore, teachers should seek ways to reduce the student’s affective filter so that they will be able to use the input they receive. In order to lower the affective filter, teachers should offer a variety of activities and modes of instruction. When done correctly, this will motivate students to participate and decrease anxiety levels. Some ways that teachers can implement this is their classrooms are: give both oral and written instruction, provide lesson that relate to student’s real lives, provide lessons that are interesting-popular culture and new technology, refrain from correcting students orally, allow students to submit answers anonymously, and reinforce that language acquisition takes time( Singleton, 1989).

Studies have shown that reading improves students speaking and writing skills. This fact is also true of ESL students. When ESL students read information in the target language they are inadvertently learning the styles and syntax of the language. Teachers should collaborate with parents, librarians, and other educators to get students reading. Krashen advocates the whole language approach, which claims that children learn most when they are reading materials that are pleasing to them. As a result, teachers may have to allow students to read outside text in order to get them reading.


            From Krashen’s perspective, when a teacher corrects the output they are not helping the student. In class correction is one way teachers can help students, but they must do so carefully. Both the Affective Filter Hypothesis and Natural Order Hypothesis suggest creating a low anxiety environment and allowing the natural order of learning to take place. Motivation plays an intricate role in the ability to learn a new language. Likewise, the constant correction of errors by the teacher will aid is learners losing their motivation. I agree with each of Krashen’s hypothesis. Anyone who has witnessed the grammar translation method in action knows that the actual acquisition of a second language is not found within the textbook. In my opinion, Krashen’s research has made an incredible contribution to the teaching of language acquisition. Krashen acknowledges that some learners gain acquisition with ease. For others, the process is hard and tedious. There are some areas of Krashen’s theories that are difficult to understand and require sound deduction and reasoning, but overall I believe his research is accurate in understanding language acquisition.


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