Abstract Interlanguage pragmatics has attracted considerable attention in recent years. One strand of interlanguage pragmatics research includes studies comparing the effectiveness of implicit versus explicit teaching on the development of pragmatics. Many studies, although inconclusively, have shown the superior effect of explicit teaching of pragmatics, but few have focused on finding ways to improve the implicit teaching of pragmatics. The present study attempted to unfold the effect of collaborative dialogue on the quality of implicit teaching of request (head act and preparator). To this end, 28 participants (19 to 33 years old, intermediate) majoring in English (freshman and junior) were divided into two groups. The experimental group (n=14) had the opportunity to complete the tasks collaboratively and the control group (n=14) were not provided with any specific pragmatic instruction. The instructional procedure included four successive sessions of teaching request in situations where the sociological parameters were systematically varied. For the purpose of data collection, the classes were audio-recorded and a pretest-posttest design for discourse completion task (DCT) was adopted. For the purpose of data analysis, target request head acts and preparators were scored and also the audio recordings of classes were transcribed and the process of learning during treatment was checked in detail. The findings indicated that the experimental group outperformed the control group in producing target preparators and head acts. And evidence of noticing the pragmatic forms namely noticing unnoticed forms, noticing the gap, and negotiation of form was observed during the collaborative task. This study suggests that teachers may need to provide learners with the opportunities for collaborative tasks along with input enhancement tasks in order to improve the pragmatic knowledge of the learners.
