The Mediating Role of Explicit Information in Processing Instruction and Production-Based Instruction on Second Language Morphological Development

This study explored the effectiveness of processing instruction (PI) and production-based instruction (PBI) with and without explicit information on the acquisition of the English simple past tense regular verb morpheme (-ed). To this end, nine Turkish EFL classes at a preparatory school of an English medium university in Istanbul were randomly selected and assigned into four instructional groups: PI+EI (n = 28), PI-EI (n = 32), PBI+EI (n = 32), PBI-EI (n = 36), and one control group (n = 16). Pre/post-test analyses showed that all the instructional groups outperformed the control group from the pre-test to the post-test. Regarding specific group differences, the PI-EI and PBI-EI groups made equal gains in both interpretation and production tasks. When EI was included as a component, however, the PI+EI group performed significantly better than the PBI+EI group on the interpretation task, while both groups showed equally improved performance on the production task. That is, EI mediated for the greater effectiveness of the PI condition than the PBI condition on the interpretation task. Further comparisons of PI+EI to PI-EI and of PBI+EI to PBI-EI showed no significant difference within the groups. Findings are discussed, implications are provided for the teachers, directions are made for further research.