Second language acquisition research into the effects of corrective feedback has investigated a variety of learning targets using a wide range of implicit and explicit feedback types (Li, 2010). To date, however, its linguistic focus has been limited to theoretically noticeable surface features (Carroll, 2001; Schmidt, 2001), and researchers have only recently begun to explore how individual differences might influence the effectiveness of particular feedback techniques (Robinson, 2005). This dissertation examines whether metalinguistic feedback presented in a visual format can help English-speaking learners improve their accuracy in interpreting the Japanese reflexive zibun ("self"), whose binding behavior involves structural characteristics (e.g., c-command, subjecthood) not overtly represented in surface morphosyntax. Both positive and negative evidence may be necessary since, unlike English "himself", Japanese "zibun" allows long-distance antecedents while disallowing non-subject antecedents (Thomas, 1995). In a computer-assisted language learning experiment using a pre-/post-/delayed-post-test design, 80 university Japanese learners were randomly assigned into three treatment conditions: one informing them whether or not their interpretations were correct (Right/Wrong Feedback), one informing them of correctness and illustrating relevant structural relationships with tree diagrams (Trees Feedback), and one providing no feedback. Participants were also administered a battery of cognitive tests, including the Modern Language Aptitude Test (Carroll & Sapon, 1959), the Visual Patterns Test (Della Sala et al., 1997), and a test of metalinguistic knowledge and sensitivity to ambiguity. Results indicated clear evidence of improvement only in the Trees-Feedback group, and cognitive variables showed different relationships with test performance according to treatment condition: Visual memory, grammatical sensitivity, rote memory, and sensitivity to ambiguity predicted post-test scores in the Trees-Feedback condition; course levels and length of Japanese study predicted scores in the Right/Wrong-Feedback condition; and grammatical sensitivity, metalinguistic knowledge, and formal study of linguistics predicted scores in the No-Feedback condition. Thus, visual feedback can facilitate the learning of a linguistic target which involves underlying structural relationships, but may work best for learners with particular aptitude profiles. Analyses of aptitude-treatment interactions hold great promise for advancing the field of SLA through producing insights about language learning processes and helping to optimize L2 instruction in relation to learners' individual characteristics. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]