Definition:
The Comprehensible Output Hypothesis, proposed by Merrill Swain in 1985, argues that language acquisition requires not only comprehensible input but also opportunities to produce language (output). When learners attempt to express meaning and encounter gaps in their ability to do so, they are pushed to notice what they don’t know, test hypotheses about language forms, and move from semantic processing to syntactic processing.
In-Depth Explanation
Swain developed this hypothesis in response to the Input Hypothesis, which claimed that input alone was sufficient for acquisition. Swain observed that Canadian French immersion students — who had received years of rich comprehensible input — had excellent comprehension but still made significant grammatical errors in production. If input alone were sufficient, these students should have been more accurate.
Three functions of output:
| Function | What happens | Example |
|---|---|---|
| Noticing (triggering) | Learner realizes they can’t say what they want to say | “I want to talk about what I did yesterday but I don’t know past tense” → notices the gap |
| Hypothesis testing | Learner tries a form and sees if it works | “I goed to the store” → gets corrected → learns “went” |
| Metalinguistic (reflective) | Learner uses language to reflect on language | Discussing grammar rules with a study partner → deepens understanding |
The “pushed output” mechanism:
The key is being pushed beyond your current ability. Output that stays comfortably within what you already know doesn’t promote acquisition. When a conversation partner signals they don’t understand, or when you realize you can’t express a thought, you’re pushed to restructure your message — and this restructuring drives acquisition.
Conversational example:
- Learner: 「昨日、私は…えっと…学校…行く…」
- Tutor: 「行きまし？」
- Learner: 「行きました。昨日、学校に行きました。」
The learner was pushed to produce the correct past tense form — a form they might have understood in input but hadn’t yet automatized for production.
Output vs. Input — not opposition:
Swain did not argue that output replaces input. Rather, input and output serve complementary functions:
- Input primarily provides the data for acquisition
- Output forces learners to process language syntactically (not just semantically) and notice gaps
This is why methods that combine rich input with meaningful output opportunities (conversation, writing, negotiation of meaning) tend to produce the best outcomes.
Related Terms
- Output Hypothesis
- Comprehensible Input
- Input Hypothesis
- Noticing Hypothesis
- Negotiation of Meaning
- Corrective Feedback
See Also
Research
- Swain, M. (1985). Communicative competence: Some roles of comprehensible input and comprehensible output in its development. In S. Gass & C. Madden (Eds.), Input in Second Language Acquisition (pp. 235–253). Newbury House. — The original formulation of the hypothesis.
- Swain, M. (2005). The output hypothesis: Theory and research. In E. Hinkel (Ed.), Handbook of Research in Second Language Teaching and Learning (pp. 471–483). Erlbaum. — Updated overview of the hypothesis and supporting research.