Backsliding is the reappearance of interlanguage errors that appeared to have been eradicated. Selinker (1972) identified it as one of the defining characteristics of interlanguage: a learner demonstrates correct usage of a form, then reverts to a previous incorrect form, typically under communicative pressure.
Selinker (1972) argued that backsliding is neither random nor a simple return to the L1. It gravitates toward an interlanguage norm, a stable point in the learner's own system rather than the native language baseline. This distinguishes it from raw transfer.
Backsliding is most visible when:
Backsliding reveals the gap between controlled and automatic knowledge. A learner who produces correct forms only when consciously monitoring, and reverts to errors in spontaneous speech, has not achieved automaticity for that feature. The correct form exists in explicit knowledge but has not been proceduralised.
This has important implications for assessment: a learner's best performance (careful, monitored output) may overestimate their actual acquisition level. Unmonitored production is a truer indicator of what has been fully acquired.
| Backsliding | Fossilization | |
|---|---|---|
| Nature | Temporary reappearance of errors | Permanent cessation of development |
| Trigger | Communicative pressure, fatigue, attention shift | Systematic: errors persist regardless of conditions |
| Prognosis | Correct form can be restored with attention | Resistant to instruction and feedback |
| Implication | Incomplete automatisation | Feature may never be fully acquired |
Persistent backsliding over extended periods may be an early indicator of incipient fossilization, particularly if corrective feedback produces only temporary improvement.