A grammaticality judgement test (GJT) presents participants with sentences and asks them to judge whether each is grammatically acceptable or unacceptable. It is one of the most widely used data collection instruments in SLA research, providing a window into learners' underlying linguistic knowledge without requiring production.
GJTs aim to access what learners know about the target language grammar, as distinct from what they can produce. A learner might fail to produce a correct relative clause in spontaneous speech but correctly judge one as grammatical on a GJT, revealing knowledge that is not yet available for production.
The critical design distinction is time pressure, which determines what type of knowledge is measured:
| Feature | Timed GJT | Untimed GJT |
|---|---|---|
| Time allowed | 3-5 seconds per item | Unlimited |
| Knowledge tapped | Implicit (automatised) | Explicit (analysed) |
| Processing | Fast, intuitive | Slow, reflective |
| Monitoring | Minimal: no time to apply rules | Maximum: learners can reason about rules |
R. Ellis (2005) demonstrated through factor analysis that timed GJTs loaded with other implicit knowledge measures (Elicited Imitation, oral narration), while untimed GJTs loaded with explicit knowledge measures (metalinguistic knowledge test). This validated the timed/untimed distinction as a methodological tool for separating the two knowledge types.
Including a correction component strengthens the instrument: a learner who judges a sentence as ungrammatical and correctly identifies the error demonstrates more robust knowledge than one who merely rejects the sentence.
GJTs have been central to debates about: