The interface issue concerning the nature of interactions between explicit and implicit linguistic knowledge in second language acquisition (SLA) has been a focus of widespread academic interest for almost four decades. However, despite intense debate at the theoretical level and emerging methodologically rigorous studies related to the topic, the issue remains unresolved. With this overview paper, we hope to offer a contribution to the pending theoretical and methodological topics related to the interface in acquiring L2 syntax. First, the paper discusses the definitions and operationalization criteria of implicit and explicit knowledge, as well as their interface. Then, we review the methods and findings of representative studies on domain-general learning and second language acquisition that have explored the interactions between implicit and explicit learning systems. Specifically, we identify the types of interactions that are tenable according to the literature in cognitive psychology and seek evidence for those interactions in the results of pub-lished state-of-the-art research. Finally, we compile methodological recommendations for further SLA studies exploring the interface. Following other scholars, throughout the discussion, we argue that bringing the field closer to resolving the interface issue requires an interdisciplinary approach that combines insights and methods from linguistic, psychological and neurocognitive research traditions.