In recent years, the importance of thinking skills in education has attracted the attention of researchers. To this end, this study investigated the effect of scaffolding and implicit instructions on the critical thinking skills (i.e., inference, evaluation, analysis, inductive and deductive reasoning) of EFL learners. To this end, 20 EFL learners who were taking an IELTS course at a language institute in two intact classes were chosen as the participants. One group was randomly assigned as the experimental group and their critical thinking skills were scaffolded following Vygotsky’s developmental model of the Zone of Proximal Development, and the other group was assigned as the control group and received implicit instruction for promoting critical thinking skills. California Critical Thinking Skills Test Form B developed by Facione and Facione (1993) was used to check the participants’ critical thinking skills. The results of the paired-samples t-test displayed that scaffolding and implicit instructions enhanced the EFL learners’ critical thinking. The analyses of the independent-samples t-test showed that the experimental group promoted their critical thinking to a greater extent in comparison with the control group. The findings of one-way MANCOVA indicated that by controlling for the pre-tests, scaffolding instruction was more effective than implicit instruction in developing the EFL learners’ critical thinking skills.
