Affective Filter

The affective filter is a hypothesised emotional barrier that stops language input from being absorbed. Proposed by Stephen Krashen in 1982, it holds that anxiety, low motivation and low self-confidence raise the filter, so a learner hears comprehensible English without acquiring it. Lowering the filter is a teaching decision, not a fixed feature of the learner.

The term appears in almost every initial TEFL course and in a great deal of observation feedback, usually in the form of a note about how relaxed the class seemed. This page defines it precisely, sets out what it does and does not claim, and shows what lowering the filter looks like in an actual lesson. It is one entry in the TEFL teaching methods and classroom techniques glossary.

What the affective filter actually claims

Krashen introduced the affective filter as one of five hypotheses in his model of second language acquisition, set out in Principles and Practice in Second Language Acquisition (1982) and developed in The Input Hypothesis (1985). The model’s central claim is that language is acquired by understanding messages slightly above the learner’s current level. The affective filter is the part that explains why that does not always work.

The metaphor is a screen sitting between the input and the part of the mind that acquires language. When the screen is down, comprehensible input passes through and is acquired. When it is up, the input is still heard and may even be understood consciously, but it is not converted into acquired competence. Krashen identified three variables that raise it: anxiety, low motivation and low self-confidence.

Two things follow that teachers sometimes miss. First, the hypothesis does not say that anxious learners cannot learn. It says that comprehensible input is a necessary condition for acquisition and a low filter is what allows that input to do its work. Second, the filter is described as strengthening around puberty, which is Krashen’s explanation for why adolescent and adult learners often plateau where younger children do not.

The idea did not arrive from nowhere. Dulay and Burt had proposed a socio-affective filter in the 1970s, and Krashen adopted and renamed it. The vocabulary of emotional barriers to learning was already in circulation; his contribution was to attach it to a specific account of how acquisition happens.

How teachers use it in practice

In staffrooms and observation feedback the affective filter functions as shorthand for a real and observable phenomenon: a class that is tense produces less language, takes fewer risks and retains less, even when the material and the teaching are identical to a class that is not.

The practical moves that follow from it are unglamorous and well established.

Sequence the risk. New language is rehearsed in pairs or small groups before anyone is asked to produce it in front of the whole room. The learner who has already said the sentence twice to one person is not gambling when they say it to thirty.

Separate accuracy from fluency. During a fluency stage, errors are noted and dealt with afterwards rather than corrected on the spot. Interrupting a learner mid-sentence to fix a verb ending teaches them that speaking is dangerous, which is expensive for a small grammatical gain. This is the reasoning behind delayed correction and behind the preference for recasts over explicit correction in communicative stages.

Make the task genuinely doable. A great deal of what looks like anxiety is an accurate reading of a task that is out of reach. Scaffolding and affect are closely linked here: support that makes the task achievable also lowers the emotional stakes. See scaffolding in the glossary for how that support is built and removed.

Normalise error. Learner errors are evidence of a developing system rather than failure, which is the point of interlanguage. Teachers who say so explicitly, and who visibly treat a wrong answer as useful information, change what it costs to attempt one.

Watch the first ten minutes. Filter conditions are set early. A lesson that opens with a cold call on the weakest learner in the room has made a decision about the rest of the hour.

A worked classroom example

A B1 general English class of eighteen adults, first session after a long summer break. The plan is a speaking lesson on past experiences, with the target language being past simple and past continuous in narrative.

The version that raises the filter. The teacher opens by asking each learner in turn to tell the class what they did over the summer. Learner three hesitates, produces a broken sentence, is corrected twice, and stops. By learner six the room has worked out that the price of speaking is public correction, and answers shrink to a few words. The teacher notes afterwards that the class was quiet and the level seemed lower than expected.

The version that lowers it. The teacher puts four holiday photographs on the board and asks the class, in pairs, to guess which one is hers. Everyone talks, nobody is on record, and the language is low stakes. She then models the target narrative herself, twice, with the second version on the board as a written frame. Pairs tell each other one summer story using the frame, then change partners and tell it again, which is where the fluency gain sits because the second telling is always better than the first. Only then does she ask for two volunteers to tell the class. Errors collected during the pair stages go on the board at the end, unattributed, and the class corrects them together.

The linguistic content of the two lessons is identical. The second produces more language, more accurate language by the end, and a class that will volunteer next week. Whether one accepts the filter metaphor or not, the difference is real and it was produced by sequencing decisions rather than by any change in the material.

Common confusions

The affective filter is regularly conflated with three other terms. The distinctions matter because they lead to different classroom responses.

Pair	The distinction
Affective filter vs language anxiety	Language anxiety is a measurable psychological state, assessed with instruments such as the Foreign Language Classroom Anxiety Scale (Horwitz, Horwitz and Cope, 1986). The affective filter is a theoretical mechanism proposed to explain what that anxiety does to acquisition. Anxiety is the evidence; the filter is the explanation offered for it.
Affective filter vs comprehensible input	Comprehensible input is the raw material of acquisition in Krashen’s model. The affective filter is the gate it has to pass. Input can be perfectly pitched and still fail to be acquired, which is the only reason the filter is needed in the model at all.
Affective filter vs motivation	Motivation is one of the three variables Krashen says raises or lowers the filter, not a synonym for it. Motivation research since Dörnyei (2001) treats motivation as something a teacher actively builds over a course, whereas the filter is a moment-by-moment classroom condition.
Affective filter vs scaffolding	Scaffolding is a technique, the affective filter is a condition. They are related because well-judged scaffolding lowers the filter as a side effect, but a scaffold can be present and the filter still high if the classroom culture punishes error.

Distinctions drawn from the sources listed below. Compiled 28 August 2026.

What the evidence supports, and what it does not

A definition of this term is incomplete without the criticism, because the criticism is well known and a teacher who cites the filter in a training assignment should know it.

The central objection is that the affective filter is difficult to falsify. Gregg (1984) argued that Krashen’s hypotheses are not stated in a way that allows them to be tested and disproved, and that the filter in particular can be invoked after the fact to explain any case of input failing to produce acquisition. McLaughlin (1987) made a related argument about the model’s key terms being defined too loosely to support the weight placed on them. The acquisition and learning distinction underpinning the whole model has been questioned on similar grounds.

What is much better supported is the underlying observation. Foreign language classroom anxiety is a well-studied construct with a validated measurement instrument, and the association between higher anxiety and lower language achievement is one of the more consistent findings in the field. The direction of causation is genuinely contested, since poor performance also produces anxiety.

The honest position for a teacher is therefore this: the filter is a useful metaphor for a real effect, and the classroom practices it recommends are supported by evidence that does not depend on the metaphor being literally true. Teach the practices with confidence. Cite the mechanism with care.

Where this term comes from

For	Source
The hypothesis itself	Krashen, S. (1982) Principles and Practice in Second Language Acquisition. Oxford: Pergamon; Krashen, S. (1985) The Input Hypothesis: Issues and Implications. London: Longman.
The earlier socio-affective filter	Dulay, H. and Burt, M. (1977) ‘Remarks on Creativity in Language Acquisition’, in Burt, M., Dulay, H. and Finocchiaro, M. (eds) Viewpoints on English as a Second Language. New York: Regents.
Measured classroom anxiety	Horwitz, E. K., Horwitz, M. B. and Cope, J. (1986) ‘Foreign Language Classroom Anxiety’, The Modern Language Journal 70(2), pp. 125–132.
The main criticism	Gregg, K. (1984) ‘Krashen’s Monitor and Occam’s Razor’, Applied Linguistics 5(2), pp. 79–100; McLaughlin, B. (1987) Theories of Second-Language Learning. London: Edward Arnold.
Motivation as a taught variable	Dörnyei, Z. (2001) Motivational Strategies in the Language Classroom. Cambridge: Cambridge University Press.
Level descriptors used here	Council of Europe, Common European Framework of Reference for Languages (CEFR), including the 2020 Companion Volume. Link checked 28 August 2026.
Practitioner guidance	British Council, TeachingEnglish professional development articles on classroom management and learner affect. Cited without a link because the URL could not be verified on the date of writing.

Print sources are given in full so they can be checked independently rather than taken on ours.

Related terms and where to go next

The affective filter sits in the group of glossary entries that describe how a learner’s English develops rather than how a lesson is run. Its closest neighbours are interlanguage, which explains why errors are systematic rather than random, and scaffolding, which is the main technique for making a task achievable enough that the filter stays down. All twenty terms are defined in the TEFL teaching methods and classroom techniques glossary.

If you want the practices above taught in sequence rather than looked up one at a time, the 120-hour Advanced International TEFL course covers lesson planning, classroom management and teaching methodology across ten modules. The lesson plan generator on this site is a quick way to draft the staged, low-risk sequencing described in the worked example.

For terminology outside pedagogy, such as what TEFL, TESOL, ESOL and CELTA stand for and which qualifications employers ask for, the global reference sits with our sister site: TEFL qualifications and terminology explained. If you are teaching or training in Ireland, The TEFL Institute of Ireland’s lesson planning walkthrough is a practical companion to the staging decisions described above.

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Last updated: 28 August 2026 · Written by: Katie Troy, The TEFL Institute Group · Review cycle: definitions are re-checked against their cited sources every six months.