The Effects of SystemicTheoretical Instruction on Developing Iranian EFL Learners’ Explicit and Implicit Knowledge of TenseAspect System

This study aimed to investigate the effects of Systemic Theoretical Instruction (STI), grounded in Sociocultural Theory and proposed by Gal’perin, on developing Iranian EFL learners’ knowledge of English tenseaspect system. To this end, two lowintermediate classes, including 24 and 21 language learners aged between 1219, were taught the distinction between simple past and present perfect tense through STI and traditional method of grammar instruction. The learners sat for a pretest one week before the treatment and an immediate and delayed posttest, one and three weeks after the instruction, respectively. The tests included binarychoice and gapfilling items to evaluate the learners’ explicit knowledge of the target tenseaspect pairings and elicited imitation test items to check their implicit knowledge. The results obtained from a series of independent and pairedsample ttests revealed a significant improvement for both groups in the immediate posttest both in terms of the entire test and its subcomponents suggesting that both types of instruction were effective in improving the learners’ implicit and explicit knowledge of the target forms in the short term. However, the significant outperformance of the STI group compared to the traditional group implied the superiority of this method. Moreover, the STI group generally outperformed the traditional group in the delayed posttest indicating the possibility of having a more lasting effect on developing learners’ knowledge when compared to the traditional method. These findings can have significant implications for teachers and materials developers in practicing the assumptions of more innovative approaches such as STI.