The Effects of the Instruction of Self-regulation Strategies and Critical Thinking Strategies on the Second Language Vocabulary Achievement among Iranian EFL Learners

The present study was set to investigate the effects of the instruction of self-regulation strategies (SSs) and critical thinking strategies (CTSs) on the second language (L2) vocabulary achievement among Iranian English as a Foreign Language (EFL) learners. In so doing, ninety intermediate level adult female students in a language institute in Tehran were selected as the main participants of the study according to their performance on the Preliminary English Test (PET). The participants were divided into three equal and homogenized groups (i.e., one control group and two experimental groups). The learners in all groups underwent pretesting, intervention, and post testing. The experimental groups were provided with the instruction of self-regulation strategies and critical thinking strategies, whereas the control group did not receive any instruction in self-regulation or critical thinking strategies. The effects of the two experimental interventions on the L2 vocabulary achievement of the EFL learners were measured. Furthermore, the degree of the improvement of both of these strategies was also studied via comparing the students’ achievement scores on pre- and post-tests of CTSs and SSs. Analyses of one-way ANOVA, post-hoc Scheffe’s tests, and paired-samples t-tests were used to analyze the collected data. The results of data analyses revealed that applying critical thinking strategies as instructional aid had a significant impact on EFL learners’ L2 vocabulary achievement. Likewise, the findings revealed that the instruction of self-regulation strategies significantly improved EFL learners’ vocabulary achievement. Moreover, it was found that self-regulation strategies were more effective than critical thinking strategies in helping the EFL learners develop their L2 vocabulary.