The Effect of ZPD-activated Instruction on EFL Learners' Vocabulary Knowledge and Written Lexical Density

Vygotsky's Sociocultural Theory (SCT, 1978) of human learning focuses on human cognitive development and its origination in social interaction. One of Vygotsky's notions is the zone of proximal development (ZPD). This study sought to examine the effect of the ZPD-activated vocabulary instruction (i.e., collaborative dialogue and scaffolding) on Iranian EFL learners' vocabulary knowledge, their written lexical density, and their domain-specific vocabulary use in writing outputs. Forty male and female EFL students from language institutes in Isfahan (Iran) took part in the study in the form of a pretest-posttest-comparison-group design. A pretest was administered to the first 2 groups (i.e., vocabulary and lexical density groups) to ensure their homogeneity in the control and experimental groups. Afterwards, the control group was taught using their EFL textbooks without any use of ZPD-activated vocabulary instruction, whereas the second group was taught through ZPD-activated vocabulary instruction and received scaffolding. The experimental and control groups also performed 3 writing tasks related to their use of domain-specific vocabulary that was taught to them previously in order to check the effect of ZPD-activated vocabulary instruction on domain-specific vocabulary use. After the instructions, the first 2 groups received a posttest to check the participants' vocabulary achievement and their lexical density improvement in their writing. The ANCOVA and independent samples t-test results for all groups showed that the experimental group developed great gains of vocabulary, lexical density and domain-specific vocabulary in their writing output, whereas the control group, which was taught using conventional techniques in vocabulary teaching showed a small development in their vocabulary knowledge, lexical density and domain-specific vocabulary knowledge. Further, the results showed that scaffolding was most effective in improving learning. The findings have implications for implementing ZPD-based activities in L2 classrooms...