A prominent linguist and educational researcher, Stephen Krashen, developed the Monitor Model, a key theory in second-language acquisition (SLA). This model consists of five interrelated hypotheses that explain how people acquire and use a second language. His theory distinguishes between acquisition (a subconscious process similar to how children learn their first language) and learning (a conscious process of studying rules and grammar).
The Acquisition-Learning Hypothesis
This hypothesis makes a clear distinction between language acquisition and language learning:
- Language Acquisition is an implicit, subconscious process, similar to how children naturally pick up their first language. It occurs when individuals are exposed to meaningful communication in the target language. This intuitive process focuses on understanding and communication rather than explicit rules.
- Language Learning, on the other hand, is a conscious process. It involves formal instruction where learners study grammar rules, memorise vocabulary, and engage in structured exercises. Krashen believes that learning alone does not lead to fluency in a language.
Acquisition leads to fluency, while learning helps monitor language use but does not significantly contribute to spontaneous communication.
The Monitor Hypothesis
This hypothesis explains how learned knowledge (conscious learning) is used to monitor or edit language production.
- The Monitor acts as a “grammar checker” that helps correct errors before speaking or writing.
- It requires time, focus, and explicit knowledge of rules to be effective.
- Some learners rely too much on monitoring (over-users), some use it too little (under-users), and others use it appropriately (optimal users).
The Monitor is useful only for refining language use but cannot replace natural fluency, which comes from acquisition.
The Natural Order Hypothesis
Krashen argues that language acquisition follows a predictable sequence, much like how children acquire their first language.
- Some grammatical structures are learned earlier than others, regardless of a learner’s first language or teaching methods.
- For example, in English, learners typically acquire -ing (progressive tense) before the third-person singular -s (he runs).
- This sequence remains relatively consistent across learners.
Language rules are acquired in a set order, and forcing learners to study them in a different order does not speed up acquisition.
The Input Hypothesis
This is one of Krashen’s most influential ideas, stating that language acquisition happens when learners receive comprehensible input (language slightly beyond their current level).
- He refers to this as i + 1, where i represents the learner’s current level and +1 is the next step in learning.
- If input is too difficult, learners will not understand or retain it.
- If input is too easy, it does not contribute to progress.
- Input should be meaningful and context-rich (e.g., through stories, conversations, or engaging reading materials).
Comprehensible input drives language acquisition—the more learners understand and engage with slightly challenging content, the more they progress.
The Affective Filter Hypothesis
This hypothesis explains how emotional factors influence language acquisition.
- Anxiety, low motivation, or lack of confidence can raise the affective filter, blocking input and hindering learning.
- Conversely, when learners feel relaxed, motivated, and confident, their affective filter is low, and they absorb more language naturally.
- A positive learning environment, engaging activities, and encouragement help lower the filter.
Emotions and motivation impact language learning—lowering stress and increasing interest can significantly improve acquisition.
Implications for Teaching and Learning
Krashen’s Monitor Model has had a profound impact on language teaching:
- Focus on Meaning, Not Just Grammar – Teachers should provide rich, comprehensible input rather than overemphasising grammar drills.
- Encourage Natural Communication – Speaking and listening in real contexts help learners acquire the language.
- Create a Low-Stress Environment – Reducing anxiety and increasing motivation improves learning outcomes.
- Gradual and Natural Learning – Language learning should be step-by-step, following the natural order of acquisition.
Criticism of Krashen’s Model
- Some researchers argue that formal instruction plays a larger role than Krashen suggests.
- His theory does not fully explain how learners develop accuracy in grammar over time.
- The Monitor Hypothesis is difficult to measure empirically.
- Individual differences (such as aptitude, cognitive skills, and exposure) may also affect language learning beyond what Krashen describes.
Krashen’s Monitor Model is a landmark theory in second-language acquisition. It highlights the importance of comprehensible input, natural communication, and a stress-free environment in learning a language. While it has some limitations, it has influenced modern communicative language teaching (CLT) and immersion programmes, promoting fluency through meaningful interaction rather than rote memorisation of grammar rules.