The importance of input has been a broadly documented concept in the field of second or foreign language acquisition. However, kinds of input and ways of its presentation are among the controversial issues in L2 classroom research. Therefore, this study was designed to compare the effects of three kinds of input-based instruction on intake and acquisition of the English causative structures by Iranian EFL learners. A total of 105 university students in four intact classes were randomly assigned to four different conditions: processing instruction (PI), textual input enhancement (TE), consciousness-raising (C-R), and control (CO). A pretest/posttest (immediate and delayed) design was used, where participants’ ability to interpret and produce the target structure was assessed through administering a multiple choice interpretation test and a sentence-level production test. Moreover, a grammaticality judgment test was run to assess the amount of intake. Results revealed that learners in the PI group significantly outperformed learners in the other groups on both immediate/delayed production posttests. The findings also indicated that, C-R group could not retain the significant effect of instruction on delayed production posttest and TE tasks were not effective in improving the learners’ production of the target structure. Moreover, the PI group outperformed the other groups on grammaticality judgment test too. Based on these findings, we can conclude that PI which encompasses the most outstanding features of both focus on form and meaning instruction might be a more effective approach in helping EFL learners to acquire the target grammatical forms.

The current second language (L2) instruction research has raised great motivation for the use of both processing instruction and meaningful output instruction tasks in L2 classrooms as the two focus-on-form (FonF) instructional tasks. The present study investigated the effect of structured input tasks (represented by referential and affective tasks) compared with meaningful output tasks (implemented through text reconstruction cloze tasks) on the acquisition of English nominal clauses (NCs). The study sought to investigate if (1) both input and output instruction would lead to significant gains of knowledge in acquiring NCs, and (2) there were any significant differences between learners' receptive and productive knowledge of nominal clauses. First-year undergraduate students studying at four intact university classrooms participated in the study. The effectiveness of the tasks was determined by a noun-clause recognition test and a sentence combination production test administered both as the pretest and posttest. The results revealed that both processing instruction and meaningful output instruction helped the learners improve their receptive knowledge of grammar effectively nevertheless, the processing instruction group did not significantly outperform the meaningful output group in their gains of receptive knowledge of grammar. The findings further illustrated that meaningful output instruction group significantly outperformed processing instruction group in their productive knowledge of grammar.