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.

中文翻译：

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书面纠正反馈及其与工作记忆的关联对英语学习者英语复数发展的贡献

尽管大量研究已经证明书面纠正反馈 (WCF) 在提高第二语言 (L2) 准确性方面的有效性，但 WCF 对习得的贡献程度仍然存在争议。因此，本研究旨在调查 WCF 对泰国 EFL（英语作为外语）学习者英语复数的内隐和外显知识发展的影响，以及学习者工作记忆能力 (WMC) 差异在多大程度上调节了效果的WCF。本实验研究采用前-后-延迟-后测设计，历时9个月。 75 名中低级学习者被随机分配到直接专注组、直接不专注组和对照组。所有小组都完成了元语言知识、不定时语法判断、定时写作、定时口头引发模仿和两项工作记忆测试。还进行了问卷调查和访谈，以探索可能调节 WCF 影响的潜在变量。在治疗期间，参与者写了一篇定时论文并收到反馈。 6周治疗期结束后，立即完成后测，并在后测三个月后进行延迟后测。结果表明，WCF 在帮助学习者复数习得方面非常有效，这表明 WCF 尤其有利于受学习者母语（L1）影响的语言特征的发展。然而，未发现 WMC 可以调节 WCF 的功效。 WCF 的明确性、教学背景和熟练程度可能导致工作记忆效应的缺失。