Fossilisation in language learning: what it is and how to fix it

A fossilised error is a mistake that has stopped responding to exposure. You have heard the correct form thousands of times, you may even be able to explain the rule, and the wrong version still comes out of your mouth, fluent and confident.

The term is spelled fossilization in American sources and fossilisation in British ones. Either way it describes the same uncomfortable thing: an error that has become a habit.

What fossilisation means in language learning

The word comes from the linguist Larry Selinker. In his 1972 paper "Interlanguage" he argued that a learner's version of a language is not a broken copy of the target. It is a system of its own, with its own rules, sitting somewhere between the native language and the language being learned. He called that system the interlanguage.

Fossilisation was his name for the parts of the interlanguage that stop moving. Selinker's estimate was that only a small minority of adult learners, perhaps five per cent, ever reach a level that cannot be told apart from a native speaker's. For everyone else, some features freeze along the way.

Later writers sorted these features by type, and the old sorting is still useful: sounds (tones, vowel length), words (a wrong translation used for years), grammar (particles, word order) and social use (politeness that is slightly off). Fossilisation is local. It hits single features, never the whole language.

Why errors fossilise

Communication works well enough. This is the main reason. If the waiter understands your order with the wrong measure word, nothing tells your brain to change it. Richard Schmidt's well-known case study of "Wes", a Japanese artist living in Hawaii, showed a learner who became a relaxed and effective conversationalist in English while his grammar barely moved over three years.

Nobody corrects you. Friends and colleagues respond to what you mean. Past a certain level, even teachers let small things go.

The native language pulls. Selinker listed transfer from the first language as one of the processes behind the interlanguage, next to overgeneralising a rule and the side effects of how something was taught.

Practice made it permanent. An error said five thousand times is a well-trained skill. It is fast and effortless, which is exactly the problem.

You no longer notice. The correct form passes your ears every day without registering, because you are listening for meaning.

Typical fossilised errors in Chinese, Japanese and Korean

These are the ones Kungfucius meets most often among long-term learners who are otherwise fluent.

Language	Fossilised habit	Example
Chinese	Tones that are right in single words and flat in sentences	Every third tone pronounced as a full dip, or neutralised entirely
Chinese	One measure word for everything	個 (个, ge) used for books, cars and fish alike
Chinese	了 (le) used as a past tense	Added to every past event, including habits and states
Chinese	是 (shì) before adjectives	我是很忙 for 我很忙 (wǒ hěn máng, I am busy)
Japanese	は (wa) and が (ga) chosen by feel	が where the topic is already known, は on new information
Japanese	Vowel and consonant length ignored	おばさん (obasan, aunt) and おばあさん (obāsan, grandmother) pronounced alike
Japanese	Pronouns carried over from English	私は (watashi wa) and あなた (anata) in every sentence
Japanese	Mixed politeness	Plain and です/ます (desu/masu) forms alternating in one conversation
Korean	은/는 (eun/neun) and 이/가 (i/ga) swapped	The same topic and subject problem as in Japanese
Korean	Three consonant series merged	달 (dal, moon), 딸 (ttal, daughter) and 탈 (tal, mask) pronounced alike
Korean	Reading by spelling	합니다 said as "hap-ni-da" when it is pronounced hamnida
Korean	Speech levels mixed	해요 (haeyo) style and plain forms used with the same person

None of these blocks communication, which is why all of them survive.

Can fossilised errors be fixed

Mostly yes, slowly, and one at a time. Reports from learners and teachers agree that long-standing errors can be shifted when the learner works on them deliberately. More exposure alone does not do it. If it did, the error would already be gone.

Expect three stages. First you hear the error only afterwards, on a recording. Then you catch it as it leaves your mouth. Then you catch it before. Under stress or speed the old form returns for a while, and that is normal.

Stabilisation or fossilisation: the criticism of the concept

The concept has serious critics. The best-known objection comes from Michael Long, who reviewed the research in 2003 and concluded that permanent cessation of learning had never really been demonstrated. To prove that an error is fossilised you would have to follow a learner for many years, under good conditions, and show that it could not change. Almost no study does that.

Long therefore preferred the more modest word stabilisation: the error is stable for now. Researchers who kept the concept, notably ZhaoHong Han, narrowed it instead, describing fossilisation as selective and local, affecting particular features in particular learners.

For a learner the debate has a cheerful outcome. What you have is, as far as anyone can prove, a stable habit. Stable habits can be retrained. "Fossil" is a metaphor, and nobody has found one in a mouth.

How to stop making the same mistakes

Record yourself. Three minutes of free talk on your phone, once a week. Listen the next day and write down what you hear. This is the only reliable way to notice errors you have stopped hearing live.

Get targeted feedback. Ask a teacher or tutor, for example on italki, to do one specific thing: interrupt every time a chosen error appears, and nothing else. General correction of everything changes nothing. A tutor who corrects only your third tones changes your third tones.

Work on one error at a time. Two at most. Keep a short list and cross items off only when recordings from three different weeks come back clean.

Retrain the mouth with imitation drills. For sound and rhythm errors, explanation is not enough. Use the three drills that force a direct comparison with a native model:

• Chorusing: speak one looped phrase in unison with the recording until the two voices merge. Best for tones, rhythm and length.
• Echoing: listen, replay the phrase in your head, then say it. Best for hearing the difference in the first place.
• Shadowing: speak along with longer audio a beat behind. Best for carrying the repaired sound into connected speech.

Overlearn the correct form. For grammar errors, write ten true sentences about your own life with the correct pattern, say them aloud daily for two weeks, then use the pattern on purpose in conversation.

Slow down. For a few weeks, speak a little more slowly than you can. The old form lives in your fast speech.

Which errors to leave alone

Not every stable error is worth the effort. Kungfucius's rule: fix what causes misunderstanding first, then what makes listeners work hard, then what bothers you. A slight accent that everyone understands can stay. Native speakers have regional habits of their own, and no committee has come for them yet.

If the stuck feeling is wider than a few specific errors, the cause is more likely the intermediate plateau than fossilisation.

What to do next

1. Record three minutes of speech today.
2. Listen tomorrow and list every error you can hear. Ask a native speaker to add to the list.
3. Pick the one that affects understanding most.
4. Spend ten minutes a day on it for three weeks, using the drill that fits: chorusing for sounds, overlearning for grammar.
5. Record again and compare. Then choose the next one.