This chapter discusses the significance of the results presented in the previous chapter together with an examination of the current SLA studies. First, it focuses on the effectiveness of instruction types in the acquisition of English transitivity alternation. Second, it presents the role of awareness as reported in the postexposure questionnaire and its relationship with instruction types and learning outcomes. Third, it discusses the variable of learners’ individual differences in terms of their aptitude as measured in the grammatical sensitivity subtest and language analysis subtest. The role of learners’ aptitude is interpreted in a complex interaction with instruction type, rule awareness and learning effectiveness.