This study aimed to investigate the effect of visual input enhancement (VIE) on the comprehension of reading texts and the learning of two grammatical forms: English relative clauses and articles. Individual learners’ working memory (WM) capacity was also tested to explore its impact on the effectiveness of VIE. A total of 48 Korean college learners of English were assigned into three groups: (a) relative group receiving VIE on relative clauses (b) article group receiving VIE on articles, and (c) a control group receiving no VIE. Results showed that VIE did not have any negative effect on the learners’ reading comprehension. Rather, it had positive effects on the learning of the two grammatical forms. According to the findings, VIE on relative clauses enhanced the learners’ receptive knowledge of the grammatical form, whereas VIE on articles enhanced the learners’ productive knowledge of the form. There was a potential link between the effectiveness of VIE and the learners’ working memory processing ability. Pedagogical implications are also discussed based on these findings.

Two experiments were conducted to examine the effects of visual input enhancement (VIE) of target forms and deliberate attention on grammar learning and reading comprehension of Korean high school students. In Experiment 1, eighty-eight students read one of the three experimental texts: (i) BT (baseline text), (ii) VIE (BT with the target forms visually enhanced), and (iii) VIE-Attention (VIE with explicit instruction asking students to pay deliberate attention to both the target forms and reading comprehension). After reading, the students responded to grammar and reading comprehension tests. The results showed that only VIE-Attention promoted grammar learning, while both the VIE and VIE-Attention significantly impaired reading comprehension. In Experiment 2, an eye tracker was used in order to further probe the effects of VIE and deliberate attention. The results revealed that the VIE and VIEAttention groups fixated longer and more often than those in the BT group and that the VIE and VIE-Attention groups performed better in the grammar test and poorer on the reading comprehension test than the BT group. The present study makes significant contributions to the VIE literature since it provides the first eye movement data elucidating the effects of VIE.