Socio-constructivist theory represented by Vygotsky (1978) emphasizes interaction and engagement with the target language in a social context based on the concept of ‘Zone of Proximal Development’（ZPD) and scaffolding. In other words, learning is best achieved through the dynamic interaction between the teacher and the learner and between learners. With the teacher's scaffolding through questions and explanations, or with a more capable peer's support, the learner can move to a higher level of understanding and extend his/her skills and knowledge to the fullest potential.