* Krashen 2: Open letter

An open letter to Stephen Krashen

Dear Stephen,

When I got your comments on the post I’d written about Michael Hoey’s defence of your theory, I was almost as excited as I was when, in 1983, I read The Natural Approach; Language Acquisition in the Classroom (let’s not forget your marvellous co-writer Tracy Terrell, sadly no longer with us). When I’d finished it, I went out and bought your 2 previous volumes (SLA and Second Language Learning (1981) and Principles and Practice in SLA (1982)), after which I felt qualified to join in the enormously animated discussions that were going on in teachers rooms and bars all over Barcelona. I’m sure you’re aware of the huge impact your theory of SLA had on the ELT world; I can honestly say that for me, as, I suspect, for hundreds of thousands of teachers, your work affected my teaching and thinking more than any other writer before or since. Whatever its shortcomings, your theory of SLA is surely one of the most influential works in the field of applied linguistics that hs been published in the last 60 years.

To the issue, then. In your reply to the criticisms I made of your theory, you urged me to read a list of replies you’ve made over the years to a number of critics. I’m in the process of gathering the texts and once I’ve read them, I’ll write my comments. But to pave the way for a critical discussion, I’d like to briefly summarise what I think are the main points of your theory and invite you to correct any mistakes I might make. This summary is taken from Jordan, 2004.

Krashen (1985) re-formulated what Corder (1967) had called in relation to SLA a “built-in syllabus” into a Natural Order Hypothesis.

To my knowledge, this hypothesis was first proposed by Corder (1967). It states that we acquire the rules of language in a predictable way, some rules tending to come early and others late. The order does not appear to be determined solely by formal simplicity, and there is evidence that it is independent of the order in which rules are taught in language classes (Krashen, 1985: 14).

Krashen (1977a, 1977b, 1978, 1981, 1982, 1985) developed these hypothesis into the Monitor Model, which contains the following five hypotheses:

A. The Acquisition-Learning Hypothesis.

According to Krashen, adults have two ways of developing competence in second languages. The first way is via acquisition, that is, by using language for communication. This is a subconscious process and the resulting acquired competence is also subconscious. The second way to develop second language competence is by language learning, which is a conscious process and results in formal knowledge of the language. For Krashen, acquisition, picking up a language naturally like children do their L1, is a process still available to adults, and is far more important that language learning. Furthermore, knowledge gained through one means (e.g., learning) cannot be internalised as knowledge of the other kind (e.g., acquisition), and only the acquisition system produces language, the learned system serving only as a monitor of the acquired system, checking the correctness of utterances against the formal knowledge stored therein.

B. The Natural Order Hypothesis

The rules of language are acquired in a predictable way, some rules coming early and others late. The order is not determined solely by formal simplicity, and it is independent of the order in which rules are taught in language classes.

C. The Monitor Hypothesis

The learned system has only one, limited, function: to act as a Monitor. Further, the Monitor cannot be used unless three conditions are met:

  1. Time. “In order to think about and use conscious rules effectively, a second language performer needs to have sufficient time” (Krashen, 1982:12).
  2. Focus on form “The performer must also be focused on form, or thinking about correctness” (Krashen, 1982: 12).
  3. Knowledge of the rule.

D. The Input Hypothesis

If there is a Natural Order, how do learners move from one point to another, from one stage of competence to the next? The Input Hypothesis explains the learner’s progress. Second languages are acquired by understanding language that contains structure “a bit beyond our current level of competence (i + 1)” by receiving “comprehensible input”. “When the input is understood and there is enough of it, i + 1 will be provided automatically. Production ability emerges. It is not taught directly” (Krashen, 1982: 21-22).

E. The Affective Filter Hypothesis

The Affective Filter is “that part of the internal processing system that subconsciously screens incoming language based on … the learner’s motives, needs, attitudes, and emotional states” (Dulay, Burt, and Krashen, 1982: 46). If the affective Filter is high, (because of lack of motivation, or dislike of the L2 culture, or feelings of inadequacy, for example) input is prevented from passing through and hence there is no acquisition. The Affective Filter is responsible for individual variation in SLA (it is not something children use) and explains why some learners never acquire full competence.

In my book, I go on to suggest weaknesses in these hypotheses, some of which I referred to in my recent post on Hoey. For the moment, let’s concentrate on the theory itself. I wonder if you, Stephen, see the above as a fair summary of it? In particular, could you answer these questions:

  1. Is it right to say that the Monitor hypothesis claims that learning is available for use in production, but not in comprehension?
  2. You say in your comment on my recent post that your hypotheses “make correct predictions, predictions that are confirmed by many studies. The hypotheses are thus easy to test – one counterexample is enough to destroy them”. Could you give me an example of a counterexample which would destroy your hypotheses?
  3. You also say in your comment that we don’t need to know whether i+1 is present in input or in output, saying that “When the existience of electrons was hypothesized, nobody had seen one. The existence of the Higgs-Boson particle was hypothesized before it was observed”. I don’t get the connection between hypothesising the existence of so far unobserved things and not needing to know whether i+1 is present in input or in output. Could you say a bit more about this, please?
  4. This comment prompts me to mention Nicola (1991) who defends aspects of your theory. Below I summarise Nicola’s argument (again, taken from my book) and I hope you’ll give your reaction.

Nicola (1991) reminds us that in order to explain why the moon moved around the earth (instead of travelling in a straight line, which, according to Newton, is what all bodies naturally do) Newton hypothesised that a body can exert a force on another body at a distance, and called this force “gravity”. Nicola says that Newton was subjected to the same main criticisms as Krashen – first that the onus was on him to prove his counter-intuitive hypothesis (about motion), which he did not do, and second that he gave no explanation for gravity any more than Krashen gives an explanation for how comprehensible input results in acquisition. Nicola continues the analogy by reminding us that, as Mach demonstrated, Newton’s laws were riddled with logical problems, such as the famous first law which states that every body perseveres in its state of rest or uniform motion, except when a force is impressed on it, which allows for a new “force” to be invented to explain any counter-observation. Mach re-formulated Newton’s theory and then Einstein took it an important step further. Nicola argues that while Gregg’s and McLaughlin’s critiques of Krashen are important, they are not necessarily fatal to his theory and that “by wholesale rejection of the theory the critics are passing up a valuable opportunity to accomplish for SLA theory what Mach and Einstein accomplished for physics.” (Nicola, 1991: 23)

Nicola suggests that in order to make the input hypothesis less than vacuous, i.e. to give it empirical content, we need to operationalise “comprehensible input”. While Nicole agrees with McLaughlin that comprehension is an introspective act that is “woefully inadequate” for empirical research, she argues that nonetheless “a workable operational definition for classroom purposes is not difficult to attain.” She suggests that classroom teachers can develop a faculty for “reading” student comprehension of input

in somewhat the same way as an experimental physicist develops a faculty for quick and accurate reading of laboratory instruments from extended work with them. The teacher can thus help the researcher in the quest for precise operational definitions of concepts (Nicola, 1991: 25).

Most of Nicola’s argument deals with what in the philosophy of science is known as the context of discovery. It is certainly true that many extremely important theories in the history of science, Newton’s and Darwin’s among them, started off with badly-defined terms and a poor track record in terms of empirical testability, and I agree that an awareness of the history of science should make us tolerant in our assessment of young theories. In order to give the hypotheses in Krashen’s model more empirical content, a good start would be, as Nicola suggests, to operationalise the concepts, starting with comprehensible input. The most important claim that Krashen makes is that no consciously-learned linguistic information can become part of one’s unconscious linguistic knowledge, and it seems that, unless we stick to circular arguments that make it necessarily so, this claim is contradicted by the evidence. But certainly it is true that as Nicola says, the hypotheses together have clear pedagogical implications, and so, in principle, any teacher interested in testing them could arrive at a good enough working definition of comprehensible input to begin the task of exploring them.

OK, that’s the first part concluded. I hope very much that you’ll respond, Stephen. For my part, I’ll write Part 2, replying to your list of responses to various critics, ASAP.



Krashen, S. (1977a) The monitor model of adult second language performance. In Burt, M., Dulay, H. and Finocchiaro, M. (eds.), Viewpoints on English as a second Languaqe. New York: Regents, 152-61.

Krashen, S. (1977b) Some issues relating to the monitor model. In Brown, H., Yorio,C. and Crymes, R. (eds.). Teaching and learning English as a second language: some trends in research and practice. Washington, DC: TESOL, 144-48.

Krashen, S. (1978) Individual variation in the use of the monitor. In Ritchie, W. (ed.) Second language acquisition research: issues and implications. New York: Academic Press, 175-83.

Krashen, S. (1981) Second language acquisition and second language learning. Oxford: Pergamon.

Krashen, S. (1982) Principles and practice in second language acquisition. Oxford; Pergamon.

Krashen, S. (1985) The Input Hypothesis: Issues and Implications. New York: Longman.

Krashen, S. and Scarcella, R. (1978) On routines and patterns in second language acquisition and performance. Language Learning 28, 283—300.

Krashen, S. and Terrell, T. (1983) The natural approach: language acquisition in the Classroom. Hayward, CA: Alemany Press.

3 thoughts on “* Krashen 2: Open letter

  1. You write that “The most important claim that Krashen makes is that no consciously-learned linguistic information can become part of one’s unconscious linguistic knowledge, and it seems that, unless we stick to circular arguments that make it necessarily so, this claim is contradicted by the evidence”

    Krashen doesn’t say that. My reading of P&P (1981) is that Krashen says that OPTIMAL acquisition occurs when the student gets interesting comprehensible input in a low-stress situation. Krashen has acknowledged that grammar teaching (e.g. learn and apply rule-type activities) works (albeit not very well compared to C.I.) but he poses the question of why it works.

    E.g. students are practising “querer” (to want) in Spanish. They could get a lecture on querer, explanations, and practice conjugating the verb and putting it in sentences. So how are they learning? Is it the explanation? Or is it exposure to meaningful language? I don’t know if, strictly speaking, you could say “how” a studentnin a grammar class is acquiring the language.

    The evidence broadly suggests (Kashen, 1981; Spada and Lightbrown 2013) that comprehensible input is the main driver of acquisition; grammar and compositional feedback, help with pronunciation etc make a small positive difference once people have a solid foundation.


  2. Hi Chris,

    Thanks for your interest in my posts on Krashen.

    I say “Krashen claims that no consciously-learned linguistic information can become part of one’s unconscious linguistic knowledge”. You say “Krashen doesn’t say that”. Sorry, but he does. This is the basis of Krashen’s distinction between acquisition and learning. Krashen (1982) says acquisition is a subconscious process and the resulting acquired competence is also subconscious, whereas language learning is a conscious process and results in formal knowledge of the language. Krashen insists that knowledge gained through one means cannot be internalised as knowledge of the other kind. More recently, Krashen (2000) emphasizes that explicit knowledge of grammar adds nothing to the acquired knowledge of a language, it just creates a monitor to notice and correct errors in output. Explicit knowledge is strictly separated from implicit knowledge and there’s no interface, which means explicit knowledge can never become implicit knowledge. As I said, this claim is contradicted by the evidence.

    I agree that the evidence broadly suggests that comprehensible input is the main driver of acquisition, but this doesn’t rescue Krashen’s Monitor model from the criticisms I made of it. The biggest problem with Krashen’s hypotheses is that the constructs (acquisition/learning; i+1; affective filter; etc.) are so vague that the theory is circular. Krashen is, of course, right to stress the importance of comprehensible input, and to raise the issue of conscious versus unconscious learning processes, but we now have far better theories of interlanguage development (including, for example Schmidt’s Noticing hypothesis, Pienemann’s Learnability and Teachability hypotheses, Long’s Interaction hypothesis, and Swain’s Output hypothesis), and a better idea of how grammar teaching can be done in such a way that the learner’s interlanguage route is recognised and the rate of acquisition significantly speeded up.

    Krashen, S. (1982) Principles and Practice in Second Language Acquisition. Oxford: Pergamon Press.
    Krashen, S. (2000) What does it take to acquire a language? ESL Magazine, 3, 22-23.


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