Although explicit and implicit knowledge of language learners are essential to theoretical and pedagogical debates in second language acquisition (SLA), little research has addressed the effects of instructional interventions on the two knowledge types (R. Ellis, 2005).This study examined the relative effectiveness of explicit and implicit types of form-focused instruction (FFI) on the acquisition of four morphosyntactic features by four measures of explicit and implicit language knowledge. The measures included: oral elicited imitation, timed and untimed grammaticality judgment, and metalinguistic knowledge tests. A pretest and two posttests were conducted immediately and three weeks after the instructional interventions. Durable effects of FFI on low intermediate Iranian learners were found for the target language forms.In particular, explicit and implicit FFI positively facilitated the development of explicit and implicit knowledge of the target features, both immediately after the instructional interventions and, marginally decreasing, over time. Also, explicit FFI was more effective than implicit FFI as measured by both explicit and implicit knowledge tests. The findings may contribute to understanding of the efficacy of explicit and implicit FFI on L2 learners’ controlled (explicit) and spontaneous (implicit) use of morphosyntactic forms at relatively early stages of L2 acquisition.
