The contribution of written corrective feedback and its association with working memory on the development of EFL learners’ English plurals

Although numerous studies have attested to the effectiveness of written corrective feedback (WCF) in promoting second language (L2) accuracy, the extent to which WCF contributes to acquisition is still debatable. This study thus aimed to investigate the effects of WCF on the development of Thai EFL (English as a foreign language) learners’ implicit and explicit knowledge of English plurals, and the extent to which learner differences in working memory capacity (WMC) moderated the efficacy of WCF. This experimental study adopted a pre–post–delayed-posttest design and was carried out over the course of a 9-month period. Seventy-five low intermediate learners were randomly assigned to the direct focused, direct unfocused and the control group. All groups completed a metalinguistic knowledge, untimed grammatical judgement, timed writing, timed oral elicited imitation, and two working memory tests. Questionnaires and interviews were also administered to explore potential variables that may moderate the effect of WCF. During treatment, participants wrote a timed essay and received feedback. After the 6-week treatment period, the immediate posttest was completed and the delayed posttest was administered three months after the posttest. The results revealed that WCF was effective in assisting learners’ plural acquisition, suggesting that WCF is beneficial especially to the development of linguistic features influenced by learners’ first language (L1). However, WMC was not found to moderate the efficacy of WCF. The explicitness of WCF, instructional context and proficiency level may have contributed to the absence of working memory effect.