Despite OT's success, opaque alternations prove difficult to capture with constraints, and some violate the theory's formal restrictions. Here, I propose a novel account of opacity drawing upon developments in psychology. Rather than one grammar, I propose a dual-system model with implicit and explicit mechanisms, a domain-specific OT-like system and a domain-general rule-based system respectively. While the implicit system can handle most linguistic patterns, special cases like opacity require explicit acquisition. This predicts an advantage for explicit over implicit learning of opacity, and that elusive substantive bias may manifest by isolating implicit learners. In an artificial language experiment, participants learned opaque and transparent metathesis patterns. Despite participants' difficulty acquiring the patterns, analysis shows a positive effect of explicit learning for opaque patterns. Additionally, implicit learners, but not explicit learners, show higher performance for substantively motivated vs. non-motivated patterns. These results tentatively support the dual-system account, and further exploration is warranted. [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://www.proquest.com/en-US/products/dissertations/individuals.shtml.]