Second language acquisition theory seeks to quantify how and by what processes individuals acquire a second language. The predominant theory of second language acquisition was developed by the University of Southern California’s Steven Krashen. Krashen is a specialist in language development and acquisition, and his influential theory is widely accepted in the language learning community.
There are five main components of Krashen’s theory. Each of the components relates to a different aspect of the language learning process. The five components are as follows:
• The Acquisition Learning Hypothesis
• The Monitor Hypothesis
• The Natural Order Hypothesis
• The Input Hypothesis
• The Affective Filter Hypothesis
1. The Acquisition-Learning Hypothesis
This hypothesis actually fuses two fundamental theories of how individuals learn languages. Krashen has concluded that there are two systems of language acquisition that are independent but related: the acquired system and the learned system.
The acquired system relates to the unconscious aspect of language acquisition. When people learn their first language by speaking the language naturally in daily interaction with others who speak their native language, this acquired system is at work. In this system, speakers are less concerned with the structure of their utterances than with the act of communicating meaning. Krashen privileges the acquired system over the learned system.
The learned system relates to formal instruction where students engage in formal study to acquire knowledge about the target language. For example, studying the rules of syntax is part of the learned system.
2. The Monitor Hypothesis
The monitor hypothesis seeks to clarify how the acquired system is affected by the learned system. When second language learners monitor their speech, they are applying their understanding of learned grammar to edit, plan, and initiate their communication. This action can only occur when speakers have ample time to think about the form and structure of their sentences.
The amount of monitoring occurs on a continuum. Some language learners over-monitor and some use very little of their learned knowledge and are said to under-monitor. Ideally, speakers strike a balance and monitor at a level where they use their knowledge but are not overly inhibited by it.
Krashen also suggests that there is individual variation among language learners with regard to 'monitor' use. He distinguishes those learners that use the 'monitor' all the time (over-users); those learners who have not learned or who prefer not to use their conscious knowledge (under-users); and those learners that use the 'monitor' appropriately (optimal users). An evaluation of the person's psychological profile can help to determine to what group they belong. Usually extroverts are under-users, while introverts and perfectionists are over-users. Lack of self-confidence is frequently related to the over-use of the 'monitor'.
3. The Natural Order Hypothesis
This hypothesis argues that there is a natural order to the way second language learners acquire their target language. Research suggests that this natural order seems to transcend age, the learner's native language, the target language, and the conditions under which the second language is being learned. The order that the learners follow has four steps:
• They produce single words.
• They string words together based on meaning and not syntax.
• They begin to identify elements that begin and end sentences.
• They begin to identify different elements within sentences and can rearrange them to produce questions.
4. The Input Hypothesis
This hypothesis seeks to explain how second languages are acquired. In its most basic form, the input hypothesis argues that learners progress along the natural order only when they encounter second language input that is one step beyond where they are in the natural order. Therefore, if a learner is at step one from the above list, they will only proceed along the natural order when they encounter input that is at the second step.
This hypothesis relates to acquisition, not to learning. Krashen claims that people acquire language best by understanding input that is a little beyond their present level of competence. Consequently, Krashen believes that 'comprehensible input' (that is, i + 1) should be provided. The 'input' should be relevant and 'not grammatically sequenced'. The 'input' should also be in sufficient quantity.
5. The Affective Filter Hypothesis
This hypothesis describes external factors that can act as a filter that impedes acquisition. These factors include motivation, self-confidence, and anxiety. For example, if a learner has very low motivation, very low self-confidence, and a high level of anxiety, the affective filter comes into place and inhibits the learner from acquiring the new language. Students who are motivated, confident, and relaxed about learning the target language have much more success acquiring a second language than those who are trying to learn with the affective filter in place.
B. Critical Review of Stephen D. Krashen's Theory of Second Language Acquisition
Krashen's theory of second language acquisition consists of five main hypotheses:
1. The Acquisition-Learning Hypothesis
Krashen, in his theory of second language acquisition (SLA) suggests that adults have two different ways of developing competence in second languages: Acquisition and learning. There are two independent ways of developing ability in second languages. Acquisition is a subconscious process identical in all important ways to the process children utilize in acquiring their first language, and learning, which is a conscious process that results in knowing about the rules of language.
Related to the real situation, the acquisition-learning hypothesis tells us that we should balance class time between acquisition activities and learning exercises. It is important to realize that students or any human being cannot both learn and acquire at the same time because one can focus on only one thing at a time, either on form or on meaning. Therefore, there must be a separation between acquisition and learning activities in FL classes and the relative weight of acquisition classes should be over that of learning classes.
The natural approach instructor does not expect students at the end of a particular course to have acquired a 'specific grammar point'. Instead s/he does expect them to display their comprehension. It is necessary and inevitable, as has been mentioned earlier, to employ two separated classes: Input and grammar classes (i.e., acquisition and learning classes). In input classes, students are given as much comprehensible input as possible. In grammar classes, however, grammar rules are presented deductively or inductively depending on the age of the students (also on whether they are field-independent or field-dependent). The role of grammar classes is to produce 'optimal monitor users' and to aid comprehension indirectly. Therefore, the core of the natural approach is acquisition activities which have a purpose other than conscious grammar exercises such as audiolingual drills and cognitive learning exercises.
2. The Monitor Hypothesis
As is mentioned, adult second language learners have two means for internalizing the target language. The first is acquisition which is a subconscious and intuitive process of constructing the system of a language. The second means is a conscious learning process in which learners attend to form, figure out rules and are generally aware of their own process. The monitor is an aspect of this second process. It edits and makes alterations or corrections as they are consciously perceived. Krashen believes that fluency in second language performance is due to what we have acquired, not what we have learned: Adults should do as much acquiring as possible for the purpose of achieving communicative fluency. Therefore, the monitor should have only a minor role in the process of gaining communicative competence. Similarly, Krashen suggests three conditions for its use: (1) there must be enough time; (2) the focus must be on form and not on meaning; (3) the learner must know the rule.
There are many difficulties with the use of the monitor, making the monitor rather weak as a language tool.
a) Having time to use the monitor: there is a price that is paid for the use of the monitor- the speaker is then focused on form rather than meaning, resulting in the production and exchange of less information, thus slowing the flow of conversation. Some speakers over-monitor to the point that the conversation is painfully slow and sometimes difficult to listen to.
b) Knowing the rule: this is a difficult condition to meet, because even the best students do not learn every rule that is taught, cannot remember every rule they have learned, and can't always correctly apply the rules they do remember. Furthermore, every rule of a language is not always included in a text nor taught by the teacher .
c) The rules of language make up only a small portion of our language competence: Acquisition does not provide 100% language competence. There is often a small portion of grammar, punctuation, and spelling that even the most proficient native speakers may not acquire. While it is important to learn these aspects of language, since writing is the only form that requires 100% competence, these aspects of language make up only a small portion of our language competence.
Due to these difficulties, Krashen recommends using the monitor at times when it does not interfere with communication, such as while writing.
3. The Natural Order Hypothesis
The Natural Order hypothesis is based on research findings (Dulay & Burt, 1974; Fathman, 1975; Makino, 1980 cited in Krashen, 1987) 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. This order seemed to be independent of the learners' age, L1 background, conditions of exposure, and although the agreement between individual acquirers was not always 100% in the studies, there were statistically significant similarities that reinforced the existence of a Natural Order of language acquisition. Krashen however 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.
4. The Input Hypothesis
The Input Hypothesis holds that language learners acquire properties of an L2 in a predictable order, going through a series of common transitional stages in moving towards target language forms. Krashen also suggests that the natural order is unaffected by instruction. (See interface/non-interface positions in sla, monitor model, morpheme acquisition studies.) (1985). The Input Hypothesis: Issues and implications.
In this hypothesis, Krashen attempts to explain how the learner acquires a second language. It is an explanation of how second language acquisition takes place. So, 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'. Since not all of the learners can be at the same level of linguistic competence at the same time, Krashen suggests that natural communicative input is the key to designing a syllabus, ensuring in this way that each learner will receive some 'i + 1' input that is appropriate for his/her current stage of linguistic competence.
Evidence for the Input Hypothesis (chiefly Krashen 1985a)
• people speak to children acquiring their first language in special ways
• people speak to L2 learners in special ways
• L2 learners often go through an initial Silent Period
• the comparative success of younger and older learners reflects provision of comprehensible input
• the more comprehensible input the greater the L2 proficiency
• lack of comprehensible input delays language acquisition
• teaching methods work according to the extent that they use comprehensible input
• immersion teaching is successful because it provides comprehensible input
• bilingual programs succeed to the extent they provide comprehensible input.
Language acquisition is caused by learners understanding input which is slightly beyond their current stage of knowledge, by means of context and other extra-linguistic cues, and that, while we should not try to provide input which specifically aims at the next stage, ‘comprehensible’ input is particularly beneficial. In this article I will suggest that there are a number of problems with Krashen's input hypothesis, as currently formulated. Firstly, by concentrating on meaning and context, he misses the fact that certain aspects of grammar development in the learner are largely internally driven, and independent of context or meaning. Secondly, he overestimates the role and benefits of simplified input. Thirdly, Krashen feels that we can never really be sure what input is relevant to what stage, but this is due to the imprecision of his formulation: once one incorporates a detailed theory of language, it is possible to come up with a theory to identify precisely what aspects of input trigger development. Finally, there are circumstances where the secondlanguage (L2) input will not be able to show the learner how to retreat from certain non-target forms: the input hypothesis is geared to handling additions to intermediate grammars, rather than losses. I will argue that second-language acquisition theory should indeed include an input hypothesis, and, consequently, that we should try and tighten up Krashen's formulation to deal with these objections, rather than abandoning it.
5. The Affective Filter Hypothesis
Finally, the fifth hypothesis, 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 and anxiety. Krashen claims that learners with high motivation, self-confidence, a good self-image, and a low level of anxiety are better equipped for success in second language acquisition. Low motivation, low self-esteem, and debilitating anxiety can combine to 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.
The learner's emotional state, according to Krashen, is just like an adaptable filter which freely passes or hinders input necessary to acquisition. In other words, input must be achieved in low-anxiety contexts since acquirers with a low affective filter receive more input and interact with confidence. The filter is 'affective' because there are some factors which regulate its strength. These factors are self-confidence, motivation and anxiety state.
Conclusion of Krashen's Comprehension Hypothesis Model of L2 learning
1. The Natural Order Hypothesis: we acquire the rules of language in a predictable order
2. The Acquisition/ Learning Hypothesis: adults have two distinctive ways of developing competences in second languages acquisition. Acquiring, that is by using language for real communication, and learning , "knowing about" language' (Krashen & Terrell 1983)
3. The Monitor Hypothesis: conscious learning can only be used as a Monitor or an editor' (Krashen & Terrell 1983)
4. The Input Hypothesis: humans acquire language in only one way - by understanding messages or by receiving "comprehensible input"
5. The Affective Filter Hypothesis: a mental block, caused by affective factors that prevents input from reaching the language acquisition device
Krashen. D. 1987. Principles and Practice in Second Language Acquisition. Prentice Hall International (UK) Ltd.
______________. Second Language Acquisition and Second Language Learning. Prentice Hall International (UK) Ltd.
Ellis. R. 1985. Understanding Second Language Acquisition. Oxford University Press.
Klein. W. 1986. Second Language Acquisition. Cambridge University Press.