Implicit vs Explicit Knowledge
The distinction between implicit and explicit L2 knowledge, and whether one can become the other, is arguably the most consequential theoretical question in SLA. Rod Ellis (2004, 2009) systematized this distinction and developed psychometric instruments to measure each type independently.
Defining the Constructs
| Feature | Implicit knowledge | Explicit knowledge |
|---|---|---|
| Awareness | Intuitive, no conscious access to rules | Conscious, verbalizable rules |
| Speed | Available in real-time processing | Accessed slowly, deliberately |
| Systematicity | Variable, probabilistic | Precise, often categorical |
| Learnability | Through exposure and use | Through instruction and study |
| Example | "That sounds wrong" | "You need third-person -s" |
The Interface Debate
The central question: can explicit knowledge convert into implicit knowledge (or vice versa)?
| Position | Proponent(s) | Claim |
|---|---|---|
| No Interface | Krashen (1981), Paradis (2009) | Explicit and implicit knowledge are neurologically distinct systems; no conversion possible |
| Strong Interface | DeKeyser (2007) | Explicit knowledge, through practice, becomes automatized and functionally equivalent to implicit knowledge |
| Weak Interface | R. Ellis (2004), N. Ellis (2005) | Explicit knowledge facilitates implicit learning by promoting noticing and directing attention to form, but does not become implicit knowledge directly |
Most current SLA researchers accept some version of the weak interface. The practical implication: explicit instruction has a role, but not by the mechanism PPP assumes (direct conversion through controlled practice). Rather, explicit knowledge helps learners notice features in input that then feed implicit learning processes.
Ellis's Measurement Battery
Ellis (2005) validated five tests loading on two factors: an implicit factor (elicited imitation, oral narrative, timed grammaticality judgment) and an explicit factor (untimed grammaticality judgment, metalinguistic knowledge test). This work moved the field beyond philosophical debate toward empirical operationalization.
References
- Ellis, R. (2004). The definition and measurement of L2 explicit knowledge. Language Learning, 54(2), 227–275.
- Ellis, R. (2009). Implicit and Explicit Knowledge in Second Language Learning, Testing and Teaching. Multilingual Matters.
- Paradis, M. (2009). Declarative and Procedural Determinants of Second Languages. John Benjamins.