Is “Comprehensible Input” Enough to Learn a Language?
Theories on How to Learn a Language
If you’ve plunged into the pedagogical world of language, you’ve probably heard about Stephen Krashen’s Comprehensible Input (CI) theory. The core idea is straight forward: the best way to acquire a language is to expose yourself to language input that you mostly understand, but which contains just a bit more complexity than your current level. This is what Krashen called i+1.
“We acquire language when we understand messages that contain structures a bit beyond our current competence.”
The appeal is obvious: activity watch and listen to CI content. No drilling, no grammar books, no spending your grade-eight French class conjugating verbs without talking because your teacher couldn’t speak a word of French herself and then had the audacity to call your father because you were acting like a class clown and when your father came to the meeting, he refused to speak in English, only French, just so show how fucked up the Canadian public school system was with languages—I digress.
Instead of wasted time, it’s about immersion and time.
But is it really that simple?
Krashen’s theory has been hugely influential. It underpins much of modern communicative language teaching and natural approaches. Yet, the theory isn’t without critics.
Empirical research shows that while CI is vital for language acquisition, it alone is insufficient for developing full active fluency. For example:
Swain (1985) emphasized the importance of output, arguing that producing language pushes learners to process language more deeply and notice gaps in their knowledge.
Long (1996) proposed the Interaction Hypothesis, highlighting that negotiation of meaning during conversations — not just passive input — is crucial for acquisition.
Lyster & Ranta (1997) demonstrated that corrective feedback in classroom settings significantly improves grammatical accuracy.
In other words, input is necessary but not enough. Relying solely on comprehensible input often leads to “receptive competence” (understanding) but limited productive skills (speaking, writing).
What about the “natural approach” and immersion?
The “natural approach,” heavily inspired by Krashen’s ideas, promotes creating environments rich in comprehensible input and delaying output until learners feel ready. This is appealing and mimics how children acquire their first language.
However, children learn in highly interactive environments with rich feedback, multimodal cues, and constant social interaction. Adults in classroom or self-study settings rarely get the same quality or quantity of interaction. Well… unless, you’re in my class, of course.
Moreover, the adult brain processes language differently, relying more on explicit learning mechanisms and metalinguistic awareness.
The pitfalls of input-only learning
Without opportunities to produce language and receive feedback:
Learners tend to fossilize errors (make mistakes that become ingrained).
They may understand much but hesitate to speak due to lack of practice.
Pronunciation, grammar, and syntactic accuracy stagnate.
They often suffer from the “comprehension paradox”: they understand much but can’t express themselves.
Practical implications for learners
Don’t throw out comprehensible input—it’s crucial. But complement it with:
Output practice: Speak, write, interact actively. Producing language helps consolidate and automatize knowledge.
Feedback: Whether from teachers, native speakers, or language tech, feedback is vital to correct mistakes before they fossilize.
Deliberate practice: Focused exercises targeting troublesome grammar or pronunciation.
Motivation and metacognition: Understand how you learn best and keep yourself engaged.
At English for Global Citizens…
My approach reflects this balanced perspective. We learn languages to communicate, and we communicate to connect. I design learning experiences combining rich input (podcasts, stories, and conversations based on your interests) with guided output practice and timely corrective feedback. This mix accelerates fluency and breaks plateaus faster than input alone. Yet, language learning isn’t race. At least, I hope it isn’t because my personal journey in Spain has taken several years because I work in English. In other words, I feel the struggle, and find ways to love it.
If you want to dive deeper into this method, join our next workshop or explore our resources:
English for Global Citizens → englishforglobalcitizens.com
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Your digression anecdote made me literally LOL
Very interesting! I think language production is really important. I’m working on a piece about what has helped me learn Spanish from scratch in middle age. Balancing consumption and production is key. Looking for opportunities to speak and regularly getting outside my comfort zone has helped