An Investigation of the Role of Explicit and Implicit Instruction in Second Language Acquisition: A Case of English Embedded Question

The present study examined the facilitative effects of three types of input-based (explicit and implicit) instruction on the intake and acquisition of the English embedded questions. The participants were 105 Iranian EFL learners from four intact classes who were randomly assigned to three treatment groups of processing instruction (PI), consciousness-raising tasks (C-R), textual input enhancement (TE), and one control group (CO). A quasiexperimental design with a pretest-treatment-posttest (immediate and delayed) sequence was used. Assessment consisted of a grammar knowledge test which included interpretation and production tasks at sentence level and a timed grammaticality judgment test. The results of data analysis indicated that all treatment groups performed significantly better than the control group on the interpretation tests over time and the treatments were also effective in improving the intake of the target structure measured through grammaticality judgment test. Moreover, all types of instruction were effective in improving the learners’ production tests except the TE. Since PI was superior to other groups in all of the tests one reasonable pedagogical implication is that explicit instruction is a more effective technique in helping EFL learners to acquire target grammatical forms.